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1
Meyertholen, Andrew. "Characteristics of charge carriers in nanostructures." Diss., [La Jolla] : University of California, San Diego, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p3355877.
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Thesis (Ph. D.)--University of California, San Diego, 2009.Title from first page of PDF file (viewed July 2, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 96-100).
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Kozikov, Aleksey. "Interference and interaction of charge carriers in graphene." Thesis, University of Exeter, 2011. http://hdl.handle.net/10036/3080.
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Electron transport at low temperatures in two-dimensional electron systems is governed by two quantum corrections to the conductivity: weak localisation and electron-electron interaction in the presence of disorder. We present the first experimental observation of these quantum corrections in graphene, a single layer of carbon atoms, over a temperature range 0.02 - 200 K. Due to the peculiar properties of graphene, weak localisation is sensitive not only to inelastic, phase-breaking scattering events, but also to elastic scattering mechanisms. The latter includes scattering within and between the two valleys (intra- and inter-valley scattering, respectively). These specifics make it possible, for example, to observe a transition from weak localisation to antilocalisation. Our work reveals a number of surprising features. First of all the transition occurs not only as the carrier density is varied, but also as the temperature is tuned. The latter has never been observed in any other system studied before. Second, due to weak electron-phonon interaction in graphene, quantum interference of electrons survives at very high temperatures, up to 200 K. For comparison, in other two-dimensional (2D) systems the weak localisation effect is only seen below 50 K. The electron-electron interaction correction is also affected by elastic scattering. In a two-valley system, there are two temperature regimes of the interaction correction that depend on the strength of inter-valley scattering. In both regimes the correction has its own expression. We show that because of the intra-valley scattering, a third regime is possible in graphene, where the expression for the correction takes a new form. The study of weak localisation demonstrates that the third regime is realised in our experiments. We use the new expression to determine the Fermiliquid parameter, which turns out to be smaller than in other 2D systems due to the chirality of charge carriers. At very low temperatures (below 100 mK) we observe a saturation of the electron dephasing length. We study different mechanisms that could be responsible for the saturation and discuss in detail one of them – spin-orbit interaction. We determine the spin coherence length from studies of weak localisation and the temperature dependence of the conductivity and found good agreement between the two types of experiments. We also show the way to tune the spin coherence length by an order of magnitude by controlling the level of disorder. However, experiment shows contradictions with theory both in values of the spin coherence length and the type of spin relaxation. We speculate about another spin-related mechanism, spin flip by vacancies, which to some extent could also explain our observations. We also present electron transport in graphene irradiated by gallium ions. Depending on the dosage of irradiation the behavior of electrons changes. Namely, electron localisation can be tuned from weak to strong. At low dosages we observe the weak localisation regime, where the mentioned quantum corrections to the conductivity dominate at low temperatures. We found the electron scattering between the valleys to be enhanced, attributing it to atomically sharp defects (kicked out carbon atoms) produced by ion irradiation. We also speculate that gallium ions can be embedded in the substrate or trapped between silica and graphene. We draw this conclusion after investigation of the spin-orbit interaction in irradiated samples. At high dosages electrons become strongly localised and their transport occurs via variable-range hopping.
3
Ito, H., Y. Yokochi, H. Tanaka, S. Kuroda, R. Kanehama, M. Umemiya, H. Miyasaka, et al. "Charge carriers in the divalent conductor (BEDT-TTF)Cu_2Br_4." The American Physical Society, 2005. http://hdl.handle.net/2237/7154.
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Devasagayam, Peter. "Experimental investigations into charge and spin carriers in polyaniline." Thesis, Durham University, 1998. http://etheses.dur.ac.uk/4745/.
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Conductivity and electron spin resonance measurements have been performed on solution doped polyaniline (PANi). It is proposed that both camphor-sulphonic acid (CSA) and 2-acrylamido-2-methyl-l-propanesulphonic acid (AMPSA) doped PANi can be described by the same model. It is suggested that the polyaniline materials are composed of differently ordered layers, a highly ordered region forming the core of the crystallites. The core of the crystallites are believed to be encapsulated within a semi- ordered region, with the crystallites themselves being dispersed in an amorphous polymer matrix. The conductivity measurements and ESR results described in this work support the proposal that within the highly ordered region of doped polyaniline crystallites, a polaronic lattice exists. The polaronic lattice facilitates "free" carriers which are responsible for "metallic" conduction within the crystallites. Encapsulating the polaronic lattice is a semi-ordered region in which (partially) mobile polarons (and possibly bipolarons) are present. The highly conductive crystallites are randomly dispersed in a less conductive polymer matrix. Charge transport within this heterogeneous system is well described by a heterogeneous metal - fluctuation induced tunnelling (FIT) model. The differences in the temperature dependent conductivities of the PANi-CSA and PANi-AMPSA materials are attributed to the systems having layers of different relative sizes (in the above model). AMPSA doped polyaniline films had a maximum room temperature conductivity of ~100 Scm(^-1). This material also showed potential for use as an electrode layer in polymer LEDs, to replace ITO coated glass. The conductivity of PANi-AMPSA was measured to be 50 ± 10 Scm(^-1) at thickness' of ~30nm. Layers of this thickness provide >90% optical transmission between 450 and 675 nm (most of the visible spectrum). Faraday rotation measurements have shown that the recently reported large Faraday rotation of polyaniline can not be reproduced. The limited results of the Faraday rotation experiments described in this work provide support for the theory that charge carriers in polyaniline have an effective mass of at least 100 times that of a free electron. It has also been shown that the claims of a polyaniline derivative (namely the Marcoussis polymer) being an entirely organic ferromagnet are unsubstantiated, despite intense investigation.
5
Tolvaišienė, Sonata. "Transport of charge carriers in ultrathin films of manganese oxides." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2009. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2009~D_20090218_143224-76401.
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The objective of this dissertation is to investigate lanthanum manganites, which exhibit colossal negative magnetoresistance and phase transitions from the paramagnetic state to the ferromagnetic state. The magnetoresistance and its ani-zotriopy of thin epitaxial manganite films at low (up to 0.5 T) magnetic fields, as well as effects induced by strong pulsed magnetic and electric fields were in-vestigated. It was demonstrated how it can be used in the development of magne-tic field sensors, short electric pulse forming devices and amplitude modulators.
It was found that in the case of ultra-thin La-Sr-MnO3 films, the sign and value of the magnetoresistance anisotropy at low magnetic fields depends on the thickness of the films. An explanation of these results was proposed using the mean field approach and taking into consideration that the structure of the films changes with its thickness. A reversible thermoelectrical switching effect was discovered and investigated. A new method for nanosecond duration electrical pulses amplitude modulation by an external magnetic field using La0.87Sr0.17MnO3 films was suggested and experimentally verified.
This dissertation consists of the abstracts in Lithuanian and English, intro-duction, six chapters, the main results and conclusions and list of literature.
The introduction contains topicality and problem, the aim of the work, tasks, scientific novelty, practical value, approval of the results, statement to be de-fended and... [to full text]Disertacijoje nagrinėjami lantano manganitai, pasižymintys faziniu virsmu iš paramagnetinės į feromagnetinę būseną bei milžiniškos neigiamos magnetovar-žos efektu. Tiriami magnetovaržos ir jos anizotropijos efektai silpnuose (iki 0,5 T) magnetiniuose laukuose bei stiprių impulsinių srovių ir magnetinių laukų sukelti efektai plonuose epitaksiniuose manganitų sluoksniuose. Pateikiami pasiūlymai tyrimo rezultatus panaudoti kuriant magnetinio lauko jutiklius, spar-čiųjų elektrinių impulsų formuotuvus bei amplitudės moduliatorius. Tiriant sil-pnų magnetinių laukų poveikį ultraplonųjų La-Sr-MnO3 sluoksnių elektriniam laidumui, buvo nustatyta, kad magnetovaržos anizotropijos ženklas ir vertė šiuo-se laukuose priklauso nuo sluoksnio storio. Pateiktas modelis, paaiškinantis eks-perimentinius rezultatus, paremtas vidutinio lauko artiniu ir įskaitantis sluoksnio struktūros kitimą kintant jo storiui. Aptiktas ir ištirtas grįžtamasis termoelektrinis nestabilumas, išaiškintos šio reiškinio atsiradimo priežastys. Pasiūlytas ir ekspe-rimentiškai realizuotas naujas ns trukmės elektrinių impulsų amplitudės modulia-vimo išoriniu magnetiniu lauku būdas, naudojant epitaksinius La0,87Sr0,17MnO3 sluoksnius. Disertaciją sudaro reziumė lietuvių ir anglų kalbomis, įvadas, šeši skyriai, pagrindiniai rezultatai ir išvados, literatūros sąrašas, publikacijų disertacijos tema sąrašas. Įvadiniame skyriuje nagrinėjamas problemos aktualumas, formuluojamas darbo tikslas bei uždaviniai, aprašomas mokslinis... [toliau žr. visą tekstą]
6
Simons, Benjamin David. "Charge carriers in magnetic Mott insulators : a route to superconductivity." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358784.
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Townsend, Paul David. "Photoexcitation and transport of charge carriers in Durham-route polyacetylene." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329161.
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Ansaripour, Ghassem. "Hot carriers and high field effects in SiGe heterostructures." Thesis, University of Warwick, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343250.
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Martínez, Moreno Elías [Verfasser]. "Kinetics of charge carriers in Si, SiNx heterojunctions / Elías Martínez Moreno." Berlin : Freie Universität Berlin, 2010. http://d-nb.info/1024103498/34.
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Röder, Christian. "Strain, charge carriers, and phonon polaritons in wurtzite GaN - a Raman spectroscopical view." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2015. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-173073.
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Die vorliegende Dissertation befasst sich mit der ramanspektroskopischen Charakterisierung von Galliumnitrid (GaN). Der Zusammenhang zwischen Waferkrümmung und mechanischer Restspannungen wird diskutiert. Mit Hilfe konfokaler Mikro-Ramanmessungen wurden Dotierprofile nachgewiesen sowie die Ladungsträgerkonzentration und -beweglichkeit ermittelt. Sämtliche Ramantensorelemente von wz-GaN wurden erstmals durch die Anwendung verschiedener Streugeometrien bestimmt. Eine neu entwickelte Vorwärtsstreuanordnung ermöglichte die Beobachtung von Phonon-Polaritonen. Es konnte gezeigt werden, dass von der theoretischen und experimentellen Betrachtung der Ramanstreuintensitäten dieser Elementaranregungen eindeutig das Vorzeichen der Faust-Henry-Koeffizienten von wz-GaN abgeleitet werden kann. Im Rahmen dieser Arbeit wurden alle Faust-Henry-Koeffizienten für GaN experimentell bestimmtThis thesis focuses on special aspects of the Raman spectroscopical characterization of wurtzite gallium nitride (wz-GaN). The correlation between wafer curvature and residual stress is discussed. By means of confocal micro-Raman measurements doping profiles were detected as well as the density and mobility of free charge carriers were deduced. All Raman scattering cross sections of wz-GaN were determined the first time using different scattering configurations. A novel method for near-forward scattering was developed in order to observe phonon polaritons with pure symmetry. It is shown that the theoretical and experimental consideration of the Raman scattering efficiency of these elementary excitations allow for determining the sign of the Faust-Henry coefficients of wz-GaN unambiguously. The Faust-Henry coefficients of GaN were deduced from Raman scattering efficiencies of corresponding TO and LO phonons
11
Falck, Jens Petter. "Polaronic charge carriers and their optical excitations in insulating La₂CuO₄ây̳." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12450.
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Ma, Yimeng. "Dynamics of charge carriers in bismuth vanadate photoanodes for water splitting using solar energy." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/38559.
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This thesis described an investigation of charge carrier dynamics in dense, flat bismuth vanadate (BiVO4) photoanodes using transient absorption spectroscopy and photoelectrochemical measurements including transient photocurrents. Transient absorption spectroscopy was employed to probe directly the photogenerated charge carrier population change as a function of time from microsecond (μs) to second (s) timescales. Transient photocurrent measurements were used to monitor charge extraction under chopped light conditions. Photo-induced absorption spectroscopy was employed to investigate charge carriers under working photo-electrochemical (PEC) conditions. The transient absorption signals due to photogenerated holes in BiVO4 were determined through using electron/hole scavengers and applied electrical bias in a complete photoelectrochemical cell. In 'un-doped' BiVO4, photogenerated holes were found to absorb from 500 nm to 900 nm. The dynamics of photogenerated holes were studied as a function of applied potential and excitation intensity. The population of long-lived (milliseconds-seconds) holes increased with increasing the width of space charge layer as a function of applied potential. A recombination process in kinetic competition with water oxidation on these long timescales was found to limit the photocurrent amplitude and onset potential in un-doped BiVO4 photoanodes. Using transient photocurrent measurements, this recombination process was identified as recombination of surface-accumulated holes with electrons from the bulk of the semiconductor (back electron/hole recombination). Doping molybdenum (MoVI) in un-doped BiVO4 has been reported to be an effective method to increase photocurrent amplitude. Impedance measurements were carried out to determine the donor density increased by the presence of MoVI doping. The increased donor density limited efficient generation of the space charge layer to retard fast recombination on microseconds to milliseconds timescales, thus limiting the long-lived hole yield under modest applied potentials. MoVI dopants were shown to improve the electron transport determined by front/back side illumination in PEC and transient absorption spectroscopy (TAS) measurements. Cobalt phosphate (CoPi) surface-modified un-doped BiVO4 photoanodes were also studied using transient absorption spectroscopy and transient photocurrent measurements. Transient absorption spectra of CoPi-modified BiVO4 were similar to those of unmodified BiVO4, and the kinetics on milliseconds to seconds did not change in the presence of CoPi surface modification. Both results indicated that photogenerated holes in BiVO4 rather than CoPi species were monitored by transient absorption spectroscopy. However, the negative shift of photocurrent onset and increased photocurrent could be explained by efficient suppression of back electron/hole recombination in BiVO4 photoanodes. In terms of the function of CoPi water oxidation catalysts on BiVO4, photo-induced absorption (PIA) was employed to further study the CoPi/BiVO4 system. CoPi species oxidised by BiVO4 holes were observed in PIA measurements due to the high extinction coefficient of oxidised CoPi and significant hole accumulation generated by continuous illumination. However, these oxidised CoPi species did not appear to drive catalytic water oxidation, as evidenced by results from spectroelectrochemical measurements of CoPi/FTO electrodes; water oxidation still occurred via BiVO4, consistent with the transient absorption results. Therefore, I concluded that in the CoPi/BiVO4 system, CoPi did not act as a catalyst, although hole transfer to CoPi can take place.
13
Kaveh, Baghbadorani Masoud. "Emission and Dynamics of Charge Carriers in Uncoated and Organic/Metal Coated Semiconductor Nanowires." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1470754655.
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Tolvaišienė, Sonata. "Krūvininkų pernaša ultraplonuosiuose mangano oksidų sluoksniuose." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2009. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2009~D_20090218_143235-51205.
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Disertacijoje nagrinėjami lantano manganitai, pasižymintys faziniu virsmu iš paramagnetinės į feromagnetinę būseną bei milžiniškos neigiamos magnetovar-žos efektu. Tiriami magnetovaržos ir jos anizotropijos efektai silpnuose
(iki 0,5 T) magnetiniuose laukuose bei stiprių impulsinių srovių ir magnetinių laukų sukelti efektai plonuose epitaksiniuose manganitų sluoksniuose. Pateikiami pasiūlymai tyrimo rezultatus panaudoti kuriant magnetinio lauko jutiklius, spar-čiųjų elektrinių impulsų formuotuvus bei amplitudės moduliatorius. Tiriant sil-pnų magnetinių laukų poveikį ultraplonųjų La-Sr-MnO3 sluoksnių elektriniam laidumui, buvo nustatyta, kad magnetovaržos anizotropijos ženklas ir vertė šiuo-se laukuose priklauso nuo sluoksnio storio. Pateiktas modelis, paaiškinantis eks-perimentinius rezultatus, paremtas vidutinio lauko artiniu ir įskaitantis sluoksnio struktūros kitimą kintant jo storiui. Aptiktas ir ištirtas grįžtamasis termoelektrinis nestabilumas, išaiškintos šio reiškinio atsiradimo priežastys. Pasiūlytas ir ekspe-rimentiškai realizuotas naujas ns trukmės elektrinių impulsų amplitudės modulia-vimo išoriniu magnetiniu lauku būdas, naudojant epitaksinius La0,87Sr0,17MnO3 sluoksnius.
Disertaciją sudaro reziumė lietuvių ir anglų kalbomis, įvadas, šeši skyriai, pagrindiniai rezultatai ir išvados, literatūros sąrašas, publikacijų disertacijos tema sąrašas.
Įvadiniame skyriuje nagrinėjamas problemos aktualumas, formuluojamas darbo tikslas bei uždaviniai, aprašomas mokslinis... [toliau žr. visą tekstą]The objective of this dissertation is to investigate lanthanum manganites, which exhibit colossal negative magnetoresistance and phase transitions from the paramagnetic state to the ferromagnetic state. The magnetoresistance and its ani-zotriopy of thin epitaxial manganite films at low (up to 0.5 T) magnetic fields, as well as effects induced by strong pulsed magnetic and electric fields were in-vestigated. It was demonstrated how it can be used in the development of magne-tic field sensors, short electric pulse forming devices and amplitude modulators. It was found that in the case of ultra-thin La-Sr-MnO3 films, the sign and value of the magnetoresistance anisotropy at low magnetic fields depends on the thickness of the films. An explanation of these results was proposed using the mean field approach and taking into consideration that the structure of the films changes with its thickness. A reversible thermoelectrical switching effect was discovered and investigated. A new method for nanosecond duration electrical pulses amplitude modulation by an external magnetic field using La0.87Sr0.17MnO3 films was suggested and experimentally verified. This dissertation consists of the abstracts in Lithuanian and English, intro-duction, six chapters, the main results and conclusions and list of literature. The introduction contains topicality and problem, the aim of the work, tasks, scientific novelty, practical value, approval of the results, statement to be de-fended and... [to full text]
15
Haque, Saif Ahmed. "Charge recombination kinetics in dye sensitised nanocrystalline solar cells." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342251.
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Kropelnytska, Yu V. "Aggregation of the squaraine dyes and its influence on the photogeneration of electric charge carriers." Thesis, БДМУ, 2020. http://dspace.bsmu.edu.ua:8080/xmlui/handle/123456789/18369.
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Pintossi, C. "CARBON-BASED HYBRID PLATFORMS FOR NOVEL PHOTOVOLTAIC DEVICES: BURIED INTERFACE CHEMISTRY AND CHARGE CARRIERS DYNAMICS." Doctoral thesis, Università degli Studi di Milano, 2016. http://hdl.handle.net/2434/362241.
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Current photovoltaic (PV) market is strongly dominated by an intense use of silicon. Although it is the second most abundant element on the Earth crust, after oxygen, Si is never present in its pure form but always bounded with other elements, and relatively complex and expensive purification procedures are needed in order to have clean, crystalline and optimally doped pure silicon.
This issue, joined with the ever-increasing demand of clean Si by almost all the technological modern applications, led scientists all over the world to look for suitable alternatives.
One of the most promising options, is to try to substitute silicon with carbon, essentially for two reasons: (i) pure C not only exists in nature but can also be obtained and purified through easy and low-cost processes, (ii) carbon can behave as a metal or a semiconductor without being doped, depending only on the particular allotrope.
Moreover, carbon allotropes capability of arranging in various geometry allows C-based materials to assume different dimensionality, starting from the quasi zero-dimensional fullerene to three-dimensional diamonds. This makes carbon nanomaterials excellent candidate for a wide range of electrical and technological devices, offering the possibility to chose the suitable allotropes depending on the particular task that is needed to be fulfilled.
For photovoltaic application, a semiconducting material which can provide dissociation sites for excitons is necessary. To accomplish this role, the mono-dimensional form of C, carbon nanotubes (CNTs), revealed to be a perfect substitute of p-type silicon, on one side of the junction because CNTs are naturally p-doped in air.
Moreover, thanks to their peculiar geometry and extraordinary electrical conductivity, they are able to provide excellent transport path for the dissociated carriers with a very good transparency (which allows a relevant amount of incident light to reach the depletion region).
In the first chapter of this thesis, carbon nanotubes will be introduced, emphasizing the properties which make this nanostructured materials optimal for PV applications. Then, the different types of carbon/silicon heterojunctions will be analyzed, starting from the classical semiconductor theory, to a more complex and realistic model. At the end of the chapter CNTs solar cells state of the art will be presented, highlighting the open questions at which this thesis is aimed to answer.
The experimental techniques, such as angle-resolved X-rays photoelectron spectroscopy (AR-XPS) and transient reflectivity (TR) measurements, used to reach this goal will be presented in Chapter 2, together with the description of the manufacturing processes that yielded to the creation of three different series of PV devices, with an improvement of the efficiency from 0.1% to 12.2% in three years.
In the third chapter, we will show how the complex buried interface between CNTs and Si can be investigated and modelled by means of photoelectron spectroscopy techniques. A complex oxide interface, composed by silicon dioxide and non-stoichiometric silicon oxide, has been unveiled and possible effects on the power conversion efficiency of PV devices are outlined.
A systematic study on the chemical and physical properties of the buried interface will be presented in Chapter 4. Oxides have been alternatively removed and regrown using suitable acids and the effects on the PV performances will be discussed in detail in this chapter. The doping effects of acids on the carbon nanotubes will also be investigated through Raman spectroscopy.
Acid effects on the heterojunctions will be unambiguously shown by the XPS measurements, and the matching of these data with the electrical PV measurements allows us to discuss the nature of the heterojunction in more detail.
In order to properly address the operation mechanism of these devices, which can be either a conventional p-n or a metal-insulator-semiconductor (MIS) junction, the dynamics of charge transfer processes at the interface will be investigated in Chapter 5 with time-resolved pump-probe reflectivity measurement.
The aim is to find a correlation between the thickness of the buried SiOxlayer and the carriers photogeneration and transport, comparing the device electrical parameter with the ultrafast behavior, analyzed by time-resolved reflectivity.
These last findings, along with several improvements in the CNTs dispersion and deposition, have led to the creation of optimized third-series solar cells with a record efficiency of 12.2%, which will be fully characterized at the end of this last chapter through a combination of suitable experimental techniques, in order to highlight the factors which contributed to this huge jump in the power conversion efficiency. The stability in time of this optimized PV devices will finally be discussed.
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Studzinsky, S. L., L. S. Tonkopieva, N. A. Davidenko, I. I. Davidenko, A. A. Ishchenko, L. I. Kostenko, A. N. Ankin, and E. V. Mokrinskaya. "Photoconductive Composite Films Based on Cobalt (II) and Nickel (II) Organic Salts Doped with Polymethine Dyes." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35287.
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Photoconducting film compositions based on cobalt (II) and nickel (II) octanoates doped by cationic
and(or) anionic polymethine dyes are obtained. Their electric and photoconductive properties are investigated.
Anomalous for semiconductor materials peculiarities of the photocurrent were observed in these composites.
Effect of memory of preliminary illumination with light was observed in the obtained films. The
scheme of non-equilibrium charge carriers photogeneration process in these compositions are suggested.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35287
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Šalkus, Tomas. "Investigation of the Correlation between Structure, Elemental Composition, and Charge Carriers’ Transport in Li+, Vo Solid Electrolytes." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2009. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2009~D_20090526_111250-04091.
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The influence of the structure and elemental composition of lithium ions’ and oxygen vacancies’ (Vo) solid electrolytes (SE) on their electrical properties are investigated in the dissertation. The technological conditions of SE ceramics’ and films’ fabrication, which influence their microstructure, are described. The results of the investigation of the surfaces, temperature stability, and electrical properties are presented.
Li+ SE belong to monoclinic, orthorhombic, or rhombohedral symmetries. The microstructure of the ceramics is mainly influenced by the temperature of their sintering. It has been shown by XPS that LiCe2/3PO4 ceramic is Li+-ion conductor. Complex impedance spectroscopy investigation showed that the increase of x in the systems Li1+xScxZr2-x(PO4)3, Li1+xZr2-2xAlxTix(PO4)3, and Li1+xGe2-2xAlxTix(PO4)3 (where x = 0.1, 0.2, 0.3) leads to the increase of bulk ionic conductivity of the ceramics and to the decrease of its activation energy. Phase transition temperature in Li3Sc2–xBx(PO4)3 compounds depends on x. The anomalies of temperature dependencies of bulk conductivity of Li3-xSc2-x-yYyZrx(PO4)3 system were observed when x = 0.1, y = 0, 0.1. The anomalies are related to superionic phase transitions in the materials, but no phase transitions have been detected for x = 0.2 compound in the studied temperature range.
Ionic conductivity and its activation energy of YSZ thick films prepared by magnetron sputtering depend on their preparation’s technological... [to full text]Disertacijoje yra nagrinėjama, kokią įtaką ličio katijonų ir deguonies vakansijų (Vo) kietųjų elektrolitų elektrinėms savybėms daro jų struktūra ir elementinė sudėtis. Darbe yra aprašomos technologinės superjoninių junginių (SJ) keramikų ir sluoksnių gamybos sąlygos, lemiančios jų mikrostruktūrą, bei pateikiami SJ paviršių, temperatūrinio stabilumo ir elektrinių savybių tyrimo rezultatai. Li+ SJ priklauso monoklininei, ortorombinei arba romboedrinei singonijoms. Keramikų mikrostruktūra labiausiai priklauso nuo jų kepinimo temperatūros. LiCe2/3PO4 keramiką paveikus elektriniu lauku, XPS buvo parodyta, kad šioje medžiagoje vyksta Li+ jonų pernaša. Kompleksinės varžos spektroskopijos tyrimai parodė, kad sistemose Li1+xScxZr2-x(PO4)3, Li1+xZr2-2xAlxTix(PO4)3 ir Li1+xGe2-2xAlxTix(PO4)3 (čia x = 0,1, 0,2, 0,3), didinant x, didėja kristalitiniai keramikų laidžiai, o jų aktyvacijos energijos mažėja. Li3Sc2–xBx(PO4)3 junginiuose vykstančio superjoninio fazinio virsmo temperatūra priklauso nuo x. Li3-xSc2-x-yYyZrx(PO4)3 sistemoje kai x = 0,1, y = 0, 0,1 temperatūrinėse kristalitinio laidžio prieklausose yra stebimos anomalijos, susijusios su superjoniniais faziniais virsmais šiose medžiagose, o kai x = 0,2 tirtame temperatūrų intervale faziniai virsmai nevyksta. Magnetroninio dulkinimo metodu suformuotų YSZ storųjų sluoksnių joninis laidis ir šio laidžio aktyvacijos energija priklauso nuo jų paruošimo technologinių sąlygų. Didinant NiO-CGO sluoksnių, suformuotų purškimo pirolizės... [toliau žr. visą tekstą]
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Deng, Zhuo, and 鄧卓. "Luminescence and transport processes of charge carriers in the GaxIn₁-xP/GaAs double-junction tandem solar cells." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/211134.
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Semiconductor multijunction solar cell is a cutting-edge photovoltaic technology aimed at developing a frontier solution to the clean energy demand and environmental problem. Due to the efficient photoabsorption and energy conversion in the visible and near-infrared spectral ranges of the solar spectrum, the multijunction solar cell structures have shown an unprecedented application potential by demonstrating a solar conversion efficiency of over 44 %. Among various multijunction solar cell structural designs, the GaxIn1-xP/GaAs double-junction tandem structure is considered as the most fundamental building block for developing the industry-standard triple- and even more junction photovoltaic cells with super high efficiency. Therefore, obtaining a better and more in-depth understanding of physical properties of the GaxIn1-xP/GaAs double-junction tandem device structure, especially some fundamental optoelectronic processes in the individual structural layer, including photoexcitation, transport and the mid-way recombination of charge carriers, is crucial for further improving the energy conversion efficiency. In this thesis, the mid-way radiative recombination, diffusion transport, localization mechanism, and photocurrent spectra of charge carriers in the GaxIn1-xP/GaAs double-junction tandem solar cells grown on GaAs substrates with different misorientation angles were investigated in detail.
Our main findings are summarized as below. Efficient radiative recombination of carriers in the GaxIn1-xP/GaAs double-junction tandem solar cell samples was demonstrated by using electroluminescence (EL) and photoluminescence (PL) techniques. The radiative recombination intensity was shown to be dependent on the intrinsic material-related parameters such as the doping concentration, growth thickness and the substrate misorientation angle both experimentally and theoretically. The radiative recombination was thus revealed to be an important loss channel of carriers in the GaxIn1-xP/GaAs double-junction tandem solar cells.
Super strong transverse diffusion of minority carriers in the top GaxIn1-xP subcell was found by the micro-EL image surveying. Theoretical simulation on the experimental data shows that the minority carrier diffusion length is as long as ~93 μm at a forward bias of 2.75 V, which is ~30 times longer than that of unbiased GaxIn1-xP epilayer. Origin of this super transverse diffusion was argued, and its influence on device performance was also discussed.
Significant correlations of carrier localization and luminescence behaviors with the substrate misorientation angle in the top GaxIn1-xP subcells were unveiled by excitation intensity- and temperature-dependent PL. The large difference in potential energy profile of GaxIn1-xP layers, caused by the different degrees of atomic ordering, was argued to interpret the observed PL distinctions.
Vertical transport and photoresponse mechanisms of charge carriers in the GaxIn1-xP/GaAs double-junction tandem solar cells were studied by temperature- and reverse bias-dependent photocurrent (PC) spectroscopy. Both the temperature and reverse bias were shown to have significant impact on the device photoresponse, in particular on the photoresponse due to the absorption of photons with energy above the bandgap of GaAs and GaxIn1-xP, namely the supra-bandgap photoresponse. A model was proposed to simulate the observed temperature- and reverse-bias dependence of the supra-bandgap photoresponse.published_or_final_version
Physics
Doctoral
Doctor of Philosophy
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Villamil, Franco Carolina. "Ultrafast dynamics of excitons and charge carriers in colloidal perovskite nanostructures studied by time-resolved optical spectroscopies." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASF012.
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Les matériaux semiconducteurs de pérovskite halogénée se sont révélés très prometteurs en raison de leurs propriétés exceptionnelles et de leur capacité d’élaboration à faible coût. Malgré les progrès réalisés, une meilleure compréhension des dynamiques de relaxation et de recombinaison dans ces matériaux photo-actifs est nécessaire afin d’améliorer les performances des dispositifs opto-électroniques. Cette thèse porte sur la relaxation des porteurs de charge/excitons « chauds » après excitation au-dessus de la bande interdite, et la recombinaison Auger advenant après une excitation de forte puissance ou à haute énergie. La spectroscopie de fluorescence résolue en temps et d'absorption transitoire (AT) femtoseconde sont utilisées afin d’étudier les effets du confinement et de la composition sur ces processus, en particulier dans les nanoplaquettes (NPLs) colloïdales de pérovskite bidimensionnelles (2D), dont la synthèse a été développée et optimisée au préalable. Les dynamiques de relaxation ont été étudiées par AT en utilisant une méthode d'analyse globale où l'évolution temporelle des différentes compositions spectrales est modélisée suivant une cinétique de réactions séquentielles. Cette méthode a pu être appliquée afin de décrire efficacement la relaxation progressive dans les nanostructures de FAPbI₃ (FA= formamidinium) faiblement confinées, et a permis de dissocier les processus de retardement de relaxation à haute puissance d’excitation dus aux effets de « hot phonon bottleneck » et de ré-excitation par recombinaison Auger (RA). Par ailleurs, l'analyse globale de l’évolution spectrale a été essentielle afin d’examiner les dynamiques de relaxation dans les NPLs 2D à fort confinement quantique et diélectrique, présentant des effets Stark importants et une transition de bord de bande excitonique discrète. Comme dans les systèmes faiblement confinés, le taux de relaxation dans les NPLs diminue avec la puissance d'excitation. Cependant, il est plus rapide dans les systèmes présentant un confinement plus important, mettant alors en évidence l'absence de ”phonon bottleneck” intrinsèque. La nature des cations internes (FA, MA=méthylammonium ou Cs) n’influe pas ce taux, ni son évolution en puissance. Toutefois, les mesures dans les films de pérovskite 2D présentant une épaisseur de puits quantique équivalente, suggèrent un rôle des ligands de surface dans la capacité à libérer l'excès d'énergie dans l'environnement. Ensuite, les recombinaisons multi-excitoniques dominées par la RA non radiative ont été étudiées dans les NPLs de pérovskite 2D fortement confinées. Dû à la géométrie asymétrique de ces nanostructures et de la délocalisation limitée de l'exciton, le temps de RA dépend fortement de la densité d'excitons via la distance inter-exciton moyenne : A faible puissance d’excitation, la RA est limitée par la diffusion de l'exciton dans le plan 2D et se produit sur plusieurs centaines de picosecondes (dépendant ainsi de la géométrie de l'échantillon). En revanche, une puissance d'excitation élevée produit des excitons dont les fonctions d’onde se recouvrent spatialement, entraînant des temps de RA inférieurs à 10 ps. Finalement, les dynamiques excitoniques dans les NPLs 2D ont été mesurées par AT après excitation dans l’ultraviolet afin d'observer le processus de multiplication d’excitons. Ce dernier implique la génération de plusieurs excitons “géminés”, et donc proches spatialement, suite à l'absorption d'un unique photon de haute énergieHalide perovskites have emerged as very promising photoactive materials due to their outstanding optoelectronic properties combined with low-cost processability. In spite of their successful implementation in photovoltaic or light-emitting devices, a deep understanding of the dynamics of relaxation and recombination is still missing in order to enhance the device performances. This thesis focuses on the study of two major fundamental processes occurring in colloidal halide perovskite nanostructures: the hot charge carrier/exciton relaxation (“cooling”), after excitation above the optical bandgap, and the non-radiative Auger recombination, taking place after high-fluence or high-photon energy excitation. In particular, time-resolved photoluminescence and femtosecond transient absorption spectroscopy were used to investigate the confinement and composition effects in strongly confined two-dimensional (2D) lead iodide perovskite nanoplatelets (NPLs), that were synthesized following the development and optimizations of colloidal methods. For the investigation of the cooling dynamics, a global analysis method based on single value decomposition was used, where the temporal evolution of the spectral lineshapes was modeled with a sequential kinetic scheme. This method was succesfully applied to effectively describe the continuous energy relaxation in weakly-confined thick FAPbI₃ nanoplates (FA=formamidinium) and allowed disantangleting the hot phonon bottleneck from the Auger reheating effects at high excitation fluence. Furthermore, the global analysis was essential to investigate the cooling dynamics in strongly confined 2D NPLs presenting large Stark effects and discrete excitonic band-edge transition far away from the continuum of states (exciton binding energy in several hundreds of meV). As in the weakly confined samples, the cooling rate of the NPLs decreases with the excitation fluence. However, it is faster in more-strongly confined samples, evidencing the absence of an intrinsic phonon bottleneck. Furthermore, the cooling rate and its evolution with the exciton density were found independent of the nature of the internal cations (FA, MA=methylammonium and Cs=cesium). However, when comparing with the rate measured in 2D layered perovskite thin film with equivalent quantum well thickness, the results strongly suggest a role of the surface ligands in the possibility to release the excess energy to the surrounding environment. This ligand-mediated relaxation mechanism becomes dominent in the thinner NPL samples with enhanced exciton/ligand vibrational mode coupling. Then, the multiple exciton recombination dominated by non-radiative Auger recombination (AR) was studied in the strongly-confined 2D perovskite NPLs. Due to the large asymmetric geometry and the limited exciton wavefunction delocalization, the AR rate strongly depends on the exciton density via the initial average inter-exciton distance. At low fluence, this distance is in several tens of nanometers such as the AR is limited by the exciton diffusion in the 2D plane. It thus occurs on a timescale of several hundreds of picoseconds and depends on the sample dimensionality (thickness and lateral sizes). In contrast, high excitation fluences produce “overlapping” excitons with inter-exciton distances of only a few times the exciton Bohr radius, resulting in AR times of less than 10 ps and independent of the NPL composition nor geometry. Finally, the exciton population dynamics of 2D NPLs after excitation in the ultraviolet was measured. The strong dependence of the AR with the inter-exciton distance allows the identification of multiple exciton generation (MEG), which involves the reaction of “geminate biexcitons” produced by the absorption of a single high-energy photon
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Klein, David. "Characterization and improvement of silicon solar cells : enhanced light acceptance and better separation and extraction of charge-carriers." Thesis, Metz, 2009. http://www.theses.fr/2009METZ003S/document.
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Ce mémoire porte sur les propriétés anti-réflectives et de passivation électrique du nitrure de silicium déposé sur du silicium type n et p. Le nitrure de silicium est utilisé dans l'optique de la fabrication de cellules solaires à hétéro contacte a-Si : H/c-Si en tant que couche frontal. Des études comparatives seront faites avec l'oxyde de silicium et le silicium amorphe. Le nitrure de silicium est déposé par déposition chimique en phase gazeuse assistée par plasma (Plasma Enhanced Chemical Vapour Déposition, PECVD). Les modifications apportées par la variation de la quantité de gaz précurseurs (silane, ammoniac, di-azote) sur la composition ont été mesurées par analyses ERDA (Elastic Recoil Detection Analysis). Les relations entre la composition de la couche et les propriétés optiques et de passivations électrique ont été mesurées (Spectroscopie Infra Rouge (FTIR), Spectrométrie Photoélectronique X (SPX), …) et simulées. L’évolution de l'épaisseur et de l'indice de réfraction fut mesurée par ellipsométrie, la réflexion, l'absorption et la transmission par spectroscopie. La passivation électrique induite par les couches de nitrure de silicium a été mesurée par TRMC (Time Resolved Microwaves Conductivity). Les meilleurs paramètres de dépositions ont été définis pour une passivation électrique optimal (vitesse de recombinaison de surface < 20 cm.s-1) et une réflexion minimal (0.03% pour l = 560 nm). La reproductibilité des dépositions ainsi que celle des propriétés des couches pour plusieurs paramètres de déposition a également été étudiéeThis work studies Silicon nitride and its electrical passivation and anti-reflection properties on n-type and p-type mono crystalline silicon for its use as light entrance window of an inverted a-Si:H/c-Si heterocontact solar cell in the frame of the development of low cost, high efficiency solar cells. Comparative investigation on silicon dioxide and amorphous silicon coatings were performed. Silicon nitride is deposited by plasma enhanced chemical vapour deposition and was investigated by various measurement methods. The modifications induced by variation of the precursor gas mixture (silane, ammoniac and nitrogen) on the composition were measured by Elastic Recoil Detection Analysis (ERDA). Correlation between the composition and the optical and electrical properties were studied (Fourier Transform InfraRed (FTIR) spectroscopy, XPS, …) and simulated. Evolution of the thickness and refractive indices were measured by ellipsometry.Measurements of the reflection, absorption and transmission were performed with spectroscopy. Time Resolved Microwaves Conductivity (TRMC) was used as a non-destructive method to determine the electrical passivation effect due to silicon nitride. Optimum deposition parameters were found in order to obtain the best electrical passivation (surface recombination velocity <20 cm.s-1) and the minimum reflection (0.03% of reflection for l = 560 nm). Reproducibility of the deposition method and behaviour of the layers for different pre-treatment and under annealing were also investigated
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Mathieson, Keith. "Modelling semiconductor pixel detectors." Thesis, University of Glasgow, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368733.
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Day, Stephen. "Controlling charge carrier injection in organic electroluminescent devices via ITO substrate modification." Thesis, University of Nottingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368243.
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Oelerich, Jan Oliver [Verfasser], and Sergei [Akademischer Betreuer] Baranovski. "Theoretical Modeling of Kinetic Phenomena of Atoms and Charge Carriers in Disordered Materials / Jan Oliver Oelerich. Betreuer: Sergei Baranovski." Marburg : Philipps-Universität Marburg, 2015. http://d-nb.info/1077866860/34.
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Shin, Ji-Yong [Verfasser], and Joachim [Akademischer Betreuer] Maier. "Effects of ionic and electronic charge carriers in nanostructured TiO2 on lithium storage / Ji-Yong Shin. Betreuer: Joachim Maier." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2012. http://d-nb.info/1024490734/34.
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Böttge, Christoph N. [Verfasser], and Mackillo [Akademischer Betreuer] Kira. "On the Phonon Interactions and Terahertz Excitations among Coulomb-correlated Charge Carriers of Semiconductors / Christoph N. Böttge. Betreuer: Mackillo Kira." Marburg : Philipps-Universität Marburg, 2013. http://d-nb.info/1043316590/34.
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AVILA, HAROLD JOSE CAMARGO. "INVESTIGATION OF THE CHARGE CARRIERS MOBILITY IN POLY(3-HEXYLTHIOPHENE) THIN FILMS PHYSICALLY AND CHEMICALLY MODIFIED USING DIFFERENT EXPERIMENTAL TECHNIQUES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2016. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=29619@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Este trabalho apresenta o estudo da mobilidade de portadores de carga em filmes finos de poli(3-hexiltiofeno) rrP3HT modificados: (a) fisicamente, através da mistura do rrP3HT com o polimetilmetacrilato, PMMA, com diferentes solventes e concentrações; e (b) quimicamente, através da sínteses de novos polímeros baseados de politiofenos com poliselenofeno rrP3HTCoSe com 5 e 10 porcento de Se. Todos os filmes fabricados foram caracterizados através de medidas de absorção UV-Vis, fotoluminescência e absorção no infravermelho. Para as blendas rrP3HT:PMMA, a partir destes espectros e usando o modelo de Spano, foram determinados os valores de acoplamento excitônico W e as semilarguras da distribuição gaussiana de estados sigma mostrando que o comprimento de conjugação, a ordem e a cristalinidade foram aprimoradas nas blendas rrP3HT:PMMA. Medidas J-V e CELIV mostraram que simples diodos baseados nas blendas rrP3HT:PMMA 70:30 exibem valores de mobilidade de portadores maiores (1.0x10 elevado a menos quatro até 5.5x10 elevado a menos quatro centimetro quadrado/Vs), com um aumento de até 450 porcento quando comparados com o valor da mobilidade do rrP3HT puro. Células fotovoltaicas foram fabricadas para avaliar o desempenho da blenda 70:30 apresentando um valor de eficiência 6 vezes maior em relação aos dispositivos baseados em rrP3HT puro. Por outro lado, o estudo da modificação química mostrou altos valores de acoplamento excitônico para os polímeros rrP3HTCoSe de 5 e 10 porcento, o que significa menores comprimentos de conjugação, ordem e cristalinidade. Os valores de mobilidade encontrados nos polímeros rrP3HTCoSe 5 e 10 porcento foram inferiores com relação ao rrP3HT puro, encontrando uma relação direta entre a energia do gap, o comprimento de conjugação e mobilidade de portadores de carga.
This work presents the study of charge carrier mobility in thin films of poly(3-hexylthiphene) rrP3HT modified: (a) physically, through the mixing the rrP3HT with polymethylmethacrylate PMMA with different solvents and concentrations and (b) chemically, through the syntheses of new polymers based on polythiophene and polyselenophene rrP3HTCoSe 5 and 10 percent of Se. All the films produced were characterized by UV-Vis absorption, photoluminescence and infrared absorption measurements. For the rrP3HT:PMMA blends, from these spectra and using the Spano model were determined excitonic bandwidth values W(eV) and half width of the Gaussian distribution of site-energy disorder sigma (eV) showing that the conjugation length, order and crystallinity were improved in rrP3HT:PMMA blends. J-V and CELIV measurements showed that the simples diodes based in rrP3HT:PMMA 70:30 with different solvents showed the highest mobility (1.00x10 to negative 4 power to 5.55x10 to negative 4 power centimeter square/Vs), with an increase of up to 450 percent compared with the value of mobility of rrP3HT pure. Photovoltaic cells were fabricated to evaluated the performance of the blend 70:30 presenting a value conversion efficiency 6 times higher compared to devices based rrP3HT pure. On the other hand, the study of chemical modification showed high values of excitonic bandwidth for the rrP3HTCoSe polymers 5 and 10 percent, which means smaller conjugation lengths, order and crystallinity. The mobility values found in rrP3HTCoSe polymers 5 and 10 percent were lower with respect to rrP3HT pure, finding a direct relationship between Eg, the conjugation length and mobility of charge carriers.
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Telfah, Ahmad D. S. "Transport of protonic charge carriers in methyl-sulfonic-acid/water mixtures a model for lowly hydrated sulfonic acid based ionomers /." [S.l. : s.n.], 2008. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-36945.
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Amonson, Michael D. "Multiple Charge Carrier Species and Their Effects in Photorefractive Two-Beam Coupling in Potassium Niobate." University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1512494096366019.
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BANDI, DILIP KUMAR. "Small Signal Impedance and Optical Modulation Bandwidth Characterization and Modeling of Organic Light Emitting Devices." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1204912125.
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Pal, Shovon [Verfasser], Andreas D. [Akademischer Betreuer] Wieck, and Nathan [Akademischer Betreuer] Jukam. "THz transmission spectroscopy of charge carriers in semiconductor heterostructures under surface electric fields / Shovon Pal. Gutachter: Andreas D. Wieck ; Nathan Jukam." Bochum : Ruhr-Universität Bochum, 2016. http://d-nb.info/1089006926/34.
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Braithwaite, Glyn. "Characterisation of the hole-acoustic phonon interaction in modulation doped Si/Siâ†1â†-â†xGeâ†x (0.085<=x<=0.28) heterostructures." Thesis, University of Warwick, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364597.
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Morgan, B. A. "Current transport in hydrogenated amorphous silicon nitride." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/842874/.
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A defect band is formed in hydrogenated amorphous silicon nitride (a-SiNx:H) due to current stressing of the material. This gives rise to an increase in conductivity, referred to as current induced conductivity. This thesis investigates the current transport mechanisms that occur in the induced defect band, by comparing the temperature dependence of the conductivity of several sets of a-SiNx:H thin film diodes. These sets were systematically current stressed to different levels with one set remaining unstressed. Samples with energy gaps of 2.06 eV and 2.28 eV were considered. We show that around room temperature a modified Poole-Frenkel description of conduction (i.e. field enhanced hopping of carriers via charged defect states) provides a good fit to the data. Using this model the activation energy of current transport was calculated and shown to depend on the material band gap. Data fitting to the Poole-Frenkel model provided further support for the field-assisted hopping mechanism. Previous investigations had suggested that the defect band resides in the lower half of the band gap, so that current transport through the defect band was then expected to be due to the movement of holes, in a manner consistent with Poole-Frenkel conduction. By considering samples grown on p-type and n-type substrates, we demonstrated that transport was indeed the result of the movement of holes through the defect states within the induced defect band. At lower temperatures the experimental data is poorly described by a modified Poole-Frenkel type process, so further mechanisms were considered, including variable-range hopping and nearest-neighbour hopping. Due to the similar nature and slight temperature dependence of each process, differentiating between the two mechanisms proved difficult. However, other factors such as the temperature range and defect density favoured variable-range hopping transport. By assuming this form of low temperature hopping transport, conduction through the defect-band of the a-SiNx:H, could then be convincingly explained over the entire temperature range from 320 K to 20 K in terms of two dominant transport mechanisms, Poole-Frenkel conduction and variable-range hopping.
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Röder, Christian [Verfasser], Jens [Akademischer Betreuer] Kortus, Jens [Gutachter] Kortus, and Ion M. [Gutachter] Tiginyanu. "Strain, charge carriers, and phonon polaritons in wurtzite GaN - a Raman spectroscopical view / Christian Röder ; Gutachter: Jens Kortus, Ion M. Tiginyanu ; Betreuer: Jens Kortus." Freiberg : Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2015. http://d-nb.info/1220837989/34.
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McGarry, Stephen. "Irradiated silicon particle detectors." Thesis, Lancaster University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369468.
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Gerleman, Ian Gregory. "Thermo-electric properties of two-dimensional silicon based heterostructures." Thesis, University of Warwick, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343787.
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Ivancová, Anna. "Elektrické transportní vlastnosti molekulárních materiálů pro pokročilé aplikace." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2012. http://www.nusl.cz/ntk/nusl-216894.
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This master´s thesis deals with possibilities of application of new organic molecular materials for electronic devices. Nowadays it is a very attractive field of research, because of the tendencies in industry to miniaturize, reduce production costs and develop new, eco-friendlier, processes of production. The theoretical part of the thesis provides a short overview of organic materials suitable for smart applications and thin films issues including their characterization. The experimental part is dedicated to means how to prepare thin-film electronic components to silicon wafers for thin films field effect transistors. The obtained results in the last part of thesis are discussed about properties of prepared thin films, in the concrete about the electrical transport properties, in the connection with the condition of preparation.
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Daanoune, Mehdi. "Mesure de durée de vie de porteurs minoritaires dans les structures semiconductrices de basse dimensionnalité." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAT024.
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La durée de vie des porteurs minoritaires est l'un des principaux paramètres mesurés dans les semi-conducteurs et la décroissance de photoconductivité (PCD) l'une des méthodes les plus largement utilisées pour ce type de mesure. Aujourd'hui, grâce aux divers équipements automatisés, la mesure de durée de vie est devenue une caractérisation de routine qui permet de juger de la qualité d'un matériau dans tous les secteurs utilisant les semi-conducteurs. Cependant, l'utilisation de micro- et nano-matériaux dans l'industrie du photovoltaïque et de la microélectronique requière l'adaptation des techniques existantes (PCD, photoluminescence etc.). En effet, avec la réduction des dimensions (couches ultraminces telles que les couches épitaxiées, couches SOI « silicon on insulator », et nanostructures), l'influence de la surface (états d'interfaces, pièges, etc.) devient prépondérante. La présence des substrats utilisés pour les croissances ou report de couche de ces différentes structures perturbe également les mesures. Ceci rend difficile l'adaptation des méthodes de mesure de durée de vie classiques comme, par exemple, le déclin de photoconductivité. Au cours de cette thèse nous nous sommes attachés à adapter des techniques de caractérisation de durée de vie à des matériaux de faibles dimensions. Nous avons tout d'abord caractérisé des échantillons massifs et des couches épitaxiées d'une épaisseur de l'ordre de la dizaine de micromètres. Nous avons proposé une technique qui consiste à déterminer simultanément la durée de vie en volume et la vitesse de recombinaison en surface des porteurs minoritaires dans d'une couche épitaxiée, à partir de la mesure de l'intensité de photoluminescence. La méthode développée consiste à calculer le rapport de l'intensité de photoluminescence (RPL) mesurée à différentes longueurs d'onde et pour différentes puissances d'excitation. Ces rapports RPL expérimentaux sont ensuite comparés aux rapports RPL simulés, ce qui permet d'évaluer la vitesse de recombinaison en surface et le temps de vie en volume. Nous avons ensuite étudié des couches semi-conductrices ultraminces de l'ordre de la centaine de nanomètres dans des structures de type SOI (silicon on insulator). Après un rappel des méthodes de fabrication et de quelques-unes des utilisations, nous avons analysé les méthodes électriques existantes permettant de déterminer la qualité des substrats SOI. Cela nous a amené à proposer une nouvelle méthode de caractérisation apportant des solutions aux limitations de ces techniques. Cette méthode se base sur une mesure courant-tension sous obscurité et sous éclairement en configuration PSEUDO-MOSFET où le substrat de la structure SOI sert de grille du transistor et deux pointes déposées sur le film de silicium servent de source et drain. Nous avons appliqué cette nouvelle méthode de caractérisation de la durée de vie des porteurs de charge à un substrat SOI et avec l'aide de la simulation numérique, nous avons pu expliquer les phénomènes de recombinaison aux interfaces et extraire les paramètres associés. Enfin, la dernière partie de ce travail de thèse concerne l'étude des nanofils pour des applications photovoltaïques. Dans les nanofils, le rapport surface sur volume augmente considérablement ce qui entraîne une diminution de la durée de vie effective due à l'augmentation de l'influence des surfaces. Le fonctionnement des cellules solaires à base de nanofils que nous avons étudiées est très dépendant de la qualité des interfaces. Nous avons analysé ces cellules grâce à la méthode RRT (« Reverse Recovery Transient ») basée sur la proportionnalité qui existe entre la quantité de charges stockées dans les régions neutres des jonctions pn polarisées et la durée de vie des porteurs minoritaires. Ce type de structure étant assez complexe, nous avons utilisé des simulations numériques pour analyser les phénomènes de recombinaison au sein de la cellule solaire et extraire les densités de défauts aux interfacesThe minority carrier lifetime is one of the main parameters used to analyse the semiconductors quality and photoconductivity decay (PCD) is one of the most widely used lifetime characterization method. Thanks to the variety of automated equipment that has developed, lifetime measurement has become a routine technique to assess the quality of semiconductors. However, the micro and nano materials used in the photovoltaic and microelectronics industry require an adaptation of the existing methods (PCD, photoluminescence etc.). Indeed, with reduced dimensions (epitaxial layers, SOI “Silicon on Insulator”, nanostructures and nanowires), the influence of the surface (interface states density, traps, etc.) becomes predominant. The presence of the substrates used for the material growth or for the layer transfer can also influence the measures. Consequently traditional methods of lifetime measurement are difficult to apply to low dimensional materials. This thesis is focused on the measurement of minority carrier lifetime in micro and nano materials (bulk, epitaxial layer, silicon on insulator and nanowires) with a special emphasis on the adaptation of the characterization tools to the material thickness. We have studied first bulk samples and epitaxial layers (with thicknesses around 50µm) by photoluminescence. We have developed a method to determine simultaneously the bulk lifetime and the surface recombination velocity using room temperature photoluminescence measurement. The procedure consists in measuring the photoluminescence intensity ratio at different incident laser wavelengths and power. These photoluminescence ratios are then compared with analytical simulations, which allow us to evaluate the surface recombination velocity and the bulk lifetime. We have then investigated SOI (Silicon on insulator) structures with ultrathin semiconductor layers of the order of 100 nanometers. After a brief description of the manufacturing methods and of some of their uses, we have analyzed the existing electrical methods used to evaluate the quality of SOI substrates. This led us to propose a new characterization method to overcome the limitations of these techniques. This method is based on a current-voltage measurement in the dark and under illumination called PSEUDO-MOSFET (the substrate of the SOI structure serves as the transistor gate and the two contact points deposited on the silicon film are used as the source and drain). We applied this new method to characterize the lifetime of a SOI substrate and with the help of numerical simulation, we were able to explain the recombination mechanism associated with interfaces and extract the parameters. Finally, the last chapter concerns the study of nanowires for photovoltaic applications. In the nanowires, the surface to volume ratio greatly increases leading to a decrease of the effective lifetime due to the increased influence of the surfaces. In this chapter, we have studied the minority carrier lifetime in core-shell nanowire-based solar cells under dark conditions with a purely electrical approach called reverse recovery transient (RRT). This method is based on storage time measurement which depends essentially on the amount of stored charges in the biased junction and can be used to calculate the minority carrier lifetime. Numerical simulations have also been done to explain the measurements and to validate the theory and the hypotheses used for parameter extraction
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Salajková, Zita. "Plazmonicky aktivní elektrochemické elektrody na bázi nanotrubic sulfidu wolframičitého pokrytých zlatými nanočásticemi." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-320220.
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When an electromagnetic wave illuminates metal nanostructure under right circumstances, it can couple to the motion of electrons and thus give rise to so-called LSPR. When these collective oscillations non-radiatively decay, they excite charge carriers that can have, for a short moment of time, highly non-thermal energy distribution. These so-called "hot" electrons and holes can then take part in photochemical applications, e.g. in reactions on photoactive electrodes where hot electrons act as catalysts. Gold nanoparticles seem to be a good candidate for fabrication of such electrodes because they exhibit resonantly enhanced absorption due to plasmon excitation in the visible and near infrared spectral range, which could make the solar energy harvesting more efficient. In this work we present electrohemical experiments that should help to clarify the underlying principles of photochemical reactions involving hot electrons. Our model system consists of indium tin oxide electrodes covered with tungsten disulphide nanotubes that were previously decorated by gold nanoparticles. By comparing the results of chronoamperometric measurements on individual components of this system it was shown that excitation of plasmonic nanoparticles indeed leads to photocurrents and that electrochemical methods can serve as a valuable tool for analysis of photochemical reactions catalyzed by hot electrons.
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Ahme, Helene [Verfasser], and Eicke [Akademischer Betreuer] Weber. "Spectroscopic investigations of transfer and transport of charge carriers in the donor/acceptor network of organic solar cells = Spektroskopische Untersuchungen zum Ladungstransfer und -transport in Donator/Akzeptor Netzwerken von organischen Solarzellen." Freiburg : Universität, 2014. http://d-nb.info/1123480591/34.
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Nilsson, David. "An Organic Electrochemical Transistor for Printed Sensors and Logic." Doctoral thesis, Norrköping : Organic Electronics, Dept. of Science and Technology, Linköping Univ, 2005. http://www.ep.liu.se/diss/science_technology/09/21/index.html.
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Djebbar, El-hocine. "A DLTS study of copper indium diselenide." Thesis, University of Salford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391312.
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Mazur, Leszek. "Etude des propriétés de transport de charges dans des semiconducteurs organiques auto-assemblés." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066388.
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Les travaux effectués dans le cadre de la thèse de doctorat, ont porté sur la mesure de la mobilité des porteurs de charge dans des semi-conducteurs organiques. La thèse de doctorat a été réalisée en "cotutelle" dans le cadre du programme franco-polonais entre le Département de Chimie de l'Université de Technologie de Wroclaw et les Laboratoire de Chimie des Polymères de l'Université Pierre et Marie Curie, Paris. Certains des résultats présentés ont été obtenus dans le cadre d'un stage scientifique dans la groupe du prof. Jeong Weon Wu à l'Ewha Womans University, Séoul, Corée du Sud. Cette thèse se compose de deux parties principales, une théoriques et expérimentales. Dans le premier, je décris matériaux semi-conducteurs organiques et les techniques de mesure, que je utilisé au cours de la thèse. La partie expérimentale est composé de cinq chapitres. En raison du fait que les molécules recherchées diffèrent fortement dans leurs structures et leurs propriétés, je décidai de présenter chaque chapitre dans la forme d'un article scientifique. La caractéristique commune de toutes les molécules étudiées est la possibilité de l'auto-organisation supramoléculaire dans les structures de cristaux liquides. Je étudié composés accepteurs-donneurs, qui peut être comprise comme matériaux de type p et n semi-conducteur. Au cours de ma thèse j'ai utilisé la technique de temps de vol et mesuré les caractéristiques courant-tension de transistor à effet de champ organique pour déterminer la mobilité des porteurs des charges dans semi-conducteurs organiques. Enfin, je payé beaucoup d'attention aux techniques spectroscopiques, y compris d'absorption femtoseconde résolue en tempsI have carried out my PhD Thesis within the framework of a Polish-French “cotutelle” program, between Chemistry Department of Wroclaw University of Technology and Laboratoire de Chimie des Polymères of Université Pierre et Marie Curie. The Polish advisor of this work was Prof. Marek Samoć and the French advisor was Prof. André Jean Attias. A part of results described in this Thesis was obtained during a research internship in a group of Prof. Jeong Weon Wu from Ewha Womans University in South Korea. This Thesis is composed of two main parts, a theoretical and experimental. In the former I describe organic semiconducting materials and the measurement techniques, which I utilized during the PhD work. The experimental part is composed of five chapters. Due to the fact that the investigated molecules differed strongly in their structures and properties, I decided to present every chapter within a form of a scientific article. The common feature of all explored molecules is the possibility of supramolecular self organization into liquid crystalline structures, and the opportunity of utilizing these materials in organic electronics and optoelectronics. Among these molecules, both oligomers and polymers can be distinguished. I studied also donor acceptor compounds, which in terms of organic electronics can be understood as materials with p and n type semiconducting character. During my PhD Thesis I used Time-of-Flight technique and measured current voltage characteristics of organic field effect transistor (OFET) to determine charge carriers mobility in organic semiconductor. Finally, I paid a lot of attention to the spectroscopic techniques, including fs transient absorption
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Bigarre, Janick. "Effets des impuretés sur la charge d'espace dans l'alumine : application au frottement." Ecully, Ecole centrale de Lyon, 1996. http://www.theses.fr/1996ECDL0007.
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L'effet des impuretés et des dopants dans l'alumine sur le piégeage de charges a été étudié à partir des monocristaux de saphirs purs et impurs, de rubis (saphirs dopés au chrome) et d'alumine polycristalline implantée par des ions zirconium. L'aptitude à former une charge d'espace a été déterminée par la méthode du miroir électrostatique en relation avec la caractérisation des sites de piégeage générés par les impuretés, le chrome et l'implantation ionique. Enfin, les propriétés de charges ont été corrélées avec le comportement tribologique de l'alumine en régime de frottement sans usure.
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Burgo, Thiago Augusto de Lima 1984. "Triboeletrização de polímeros dielétricos : mosaicos macroscópicos de carga e seus efeitos sobre as forças de atrito em interfaces." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/250320.
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Orientador: Fernando GalembeckTese (doutorado) - Universidade Estadual de Campinas, Instituto de Química
Made available in DSpace on 2018-08-24T05:29:50Z (GMT). No. of bitstreams: 1 Burgo_ThiagoAugustodeLima_D.pdf: 54614783 bytes, checksum: 04e6b01b521de52d69d91a83d891d034 (MD5) Previous issue date: 2013
Resumo: A triboeletrização de polímeros gera domínios macroscópicos de carga positiva e negativa, verificando a geometria fractal de mosaicos de carga previamente detectados por microscopia de sonda elétrica. Utilizando métodos analíticos adequados (espectroscopia de perda de energia de elétrons, microespectroscopia infravermelho/Raman e carbonização/colorimetria) e cálculos teóricos, espécies positivas foram identificadas como hidrocarbocátions e espécies negativas como fluorocarbânions. A triboeletrização de PTFE com PE é entendida como segue: a ruptura homolítica mecanoquímica da cadeia é seguida por transferência eletrônica dos radicais livres de hidrocarbonetos para os radicais mais eletronegativos do fluorocarbono. Os íons gerados pelos fragmentos de cadeia sofrem auto-ordenamento de acordo com a teoria de Flory- Huggins, formando os padrões macroscópicos observados experimentalmente. Estes resultados mostram que a triboeletrização só pode ser compreendida considerando os eventos químicos complexos provocados por ação mecânica, acoplados a conceitos bem estabelecidos pela físico-química. Além disso, o atrito entre superfícies dielétricas produz padrões de carga fixos e estáveis que contribuem para interações eletrostáticas entre superfícies. Medidas de coeficiente de resistência de rolamento de esferas de vidro sobre PTFE triboeletrizado, bem como de atrito estático de pellets de polietileno e imagens de microscopia de força lateral, mostraram que as forças de atrito aumentam muitas vezes em superfícies triboeletrizadas, nas quais as contribuições das interações eletrostáticas podem suplantar todas outras contribuições. Estes resultados são explicados considerando um mecanismo segundo o qual a indução de carga por uma superfície triboeletrizada no contato com outra superfície dissipa energia durante o atrito, sugerindo novas abordagens para controlar atrito em interfaces pelo controle da formação de tribocargas
Abstract: Tribocharged polymers display macroscopically patterned positive and negative domains, verifying the fractal geometry of electrostatic mosaics previously detected by electric probe microscopy. Using suitable analytical techniques (electron energy-loss spectral imaging, infrared/Raman microspectrophotometry and carbonization/colorimetry) and theoretical calculations, the positive species were identified as hydrocarbocations and the negative species as fluorocarbanions. A comprehensive model is presented for PTFE tribocharging with PE: mechanochemical chain homolytic rupture is followed by electron transfer from hydrocarbon free radicals to the more electronegative fluorocarbon radicals. Polymer ions self-assemble according to Flory-Huggins theory, thus forming the experimentally observed macroscopic patterns. These results show that tribocharging can only be understood by considering the complex chemical events triggered by mechanical action, coupled to well-established physicochemical concepts. Also, friction between dielectric surfaces produces patterns of fixed, stable electric charges that in turn contribute electrostatic components to surface interactions between the contacting solids. The coefficient of rolling resistance of glass beads on tribocharged PTFE was measured, as well as the static friction coefficient of polyethylene pellets on PTFE and friction force on the scanning probe during lateral-force microscopy imaging. Results show that friction coefficients may increase many-fold on tribocharged surfaces and the contribution of electrostatic interactions may supersede all other contributions to friction. These results are explained considering a mechanism according to which charge induction by an electrified surface on a contacting body accounts for energy dissipation during friction suggesting new approaches to control friction coefficients, by controlling tribocharge formation
Doutorado
Físico-Química
Doutor em Ciências
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Grigioni, I. "DEVELOPMENT OF PHOTOCATALYTIC MATERIALS FOR SOLAR LIGHT CONVERSION INTO FUELS." Doctoral thesis, Università degli Studi di Milano, 2015. http://hdl.handle.net/2434/333066.
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Solar light possesses a large amount of energy. The sun provides to our planet an intense flux of high energetic photons capable to promote extremely up-hill reactions, such as the photosynthetic fixation of CO2 in biological systems. This energy flow drives life on Earth.
My PhD thesis is focused on solar driven conversion processes. While in the first year I principally investigated the photocatalytic reduction of CO2 with TiO2-based materials. In the second year I started to explore new promising visible light harvesting materials and in particular I worked on CdSe quantum dots synthesis and on their use as photocatalysts for hydrogen production under visible light, with special interest on the size dependent recombination of the photogenerated. Finally, during my stage by Professor Kamat’s laboratory at Notre Dame University (Indiana, US), I started to work on the use of WO3/BiVO4 heterojunction photoanodes, for photoelectrocatalytic applications, and especially on charge carriers dynamics through transient absorption spectroscopy measurements.
A short overview of the main themes treated during my PhD is outlined below.
1st year
1. Photocatalytic tests on TiO2 based materials in the photoassisted reactions of CO2 reduction and steam reforming of methanol, as a part of the research project FotoRiduCO2 PON01_02257.
2nd year
2. Synthesis and characterization of CdSe quantum dots with different size and their application in photocatalytic H2 production under visible light irradiation.
3. Preparation of WO3, BiVO4 and WO3/BiVO4 photoanodes for photoelectrochemical water splitting application and their study with transient absorption techniques.
3rd year
4. Preparation and characterization through femtosecond transient absorption spectroscopy of BiVO4 and WO3/BiVO4 films with variable BiVO4 thickness. The use of different pump energy allowed to suggest a new optical transition model that accounts for the electron transfer paths between the two oxides. Photoelectrochemical experiments validate the proposed model.
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Mazur, Leszek. "Etude des propriétés de transport de charges dans des semiconducteurs organiques auto-assemblés." Electronic Thesis or Diss., Paris 6, 2014. http://www.theses.fr/2014PA066388.
Full textAbstract:
Les travaux effectués dans le cadre de la thèse de doctorat, ont porté sur la mesure de la mobilité des porteurs de charge dans des semi-conducteurs organiques. La thèse de doctorat a été réalisée en "cotutelle" dans le cadre du programme franco-polonais entre le Département de Chimie de l'Université de Technologie de Wroclaw et les Laboratoire de Chimie des Polymères de l'Université Pierre et Marie Curie, Paris. Certains des résultats présentés ont été obtenus dans le cadre d'un stage scientifique dans la groupe du prof. Jeong Weon Wu à l'Ewha Womans University, Séoul, Corée du Sud. Cette thèse se compose de deux parties principales, une théoriques et expérimentales. Dans le premier, je décris matériaux semi-conducteurs organiques et les techniques de mesure, que je utilisé au cours de la thèse. La partie expérimentale est composé de cinq chapitres. En raison du fait que les molécules recherchées diffèrent fortement dans leurs structures et leurs propriétés, je décidai de présenter chaque chapitre dans la forme d'un article scientifique. La caractéristique commune de toutes les molécules étudiées est la possibilité de l'auto-organisation supramoléculaire dans les structures de cristaux liquides. Je étudié composés accepteurs-donneurs, qui peut être comprise comme matériaux de type p et n semi-conducteur. Au cours de ma thèse j'ai utilisé la technique de temps de vol et mesuré les caractéristiques courant-tension de transistor à effet de champ organique pour déterminer la mobilité des porteurs des charges dans semi-conducteurs organiques. Enfin, je payé beaucoup d'attention aux techniques spectroscopiques, y compris d'absorption femtoseconde résolue en tempsI have carried out my PhD Thesis within the framework of a Polish-French “cotutelle” program, between Chemistry Department of Wroclaw University of Technology and Laboratoire de Chimie des Polymères of Université Pierre et Marie Curie. The Polish advisor of this work was Prof. Marek Samoć and the French advisor was Prof. André Jean Attias. A part of results described in this Thesis was obtained during a research internship in a group of Prof. Jeong Weon Wu from Ewha Womans University in South Korea. This Thesis is composed of two main parts, a theoretical and experimental. In the former I describe organic semiconducting materials and the measurement techniques, which I utilized during the PhD work. The experimental part is composed of five chapters. Due to the fact that the investigated molecules differed strongly in their structures and properties, I decided to present every chapter within a form of a scientific article. The common feature of all explored molecules is the possibility of supramolecular self organization into liquid crystalline structures, and the opportunity of utilizing these materials in organic electronics and optoelectronics. Among these molecules, both oligomers and polymers can be distinguished. I studied also donor acceptor compounds, which in terms of organic electronics can be understood as materials with p and n type semiconducting character. During my PhD Thesis I used Time-of-Flight technique and measured current voltage characteristics of organic field effect transistor (OFET) to determine charge carriers mobility in organic semiconductor. Finally, I paid a lot of attention to the spectroscopic techniques, including fs transient absorption
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Solowan, Hans-Michael [Verfasser], and Ulrich T. [Akademischer Betreuer] Schwarz. "Charge carrier dynamics in InGaN quantum wells: stimulated emission depletion and lateral charge carrier motion." Freiburg : Universität, 2016. http://d-nb.info/1119452694/34.
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Fernandez, Garrillo Pablo Arturo. "Développement de techniques de microscopie Kelvin hautement résolues et photomodulées pour l'étude de systèmes photovoltaïques." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAY031/document.
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Cette thèse propose, décrit et utilise un ensemble de techniques basées sur la microscopie à force atomique sous ultravide pour la cartographie simultanée, à l'échelle nanométrique, de la topographie de surface et des dynamiques temporelles des photo-porteurs. Ainsi, en contrôlant la dépendance du photo-potentiel de surface moyen mesuré par microscopie à force de sonde Kelvin en fonction de la fréquence de répétition d'une source lumineuse externe d'excitation, le dispositif expérimental permet d’accéder aux dynamiques temporelles du photo-potentiel de surface qui, à leur tour, permettent d'étudier les dynamiques des photo-porteurs sur une large gamme d'échantillons. Afin de permettre le processus de nano-imagerie bidimensionnelle, ces mesures sont acquises de manière répétée en enregistrant des courbes spectroscopiques en chaque point d’une grille prédéfinie. En utilisant une procédure d'ajustement mathématique automatique, les dynamiques temporelles des photo-porteurs sont extraites à partir des données expérimentales.Cet ensemble de nouvelles méthodes est utilisé pour l’étude de plusieurs types d'échantillons issus de différentes technologies photovoltaïques telles que des couches minces en silicium poly-cristallin à petits grains, des cellules de troisième génération à nano cristaux de silicium, des cellules photovoltaïques organiques et des cellules à base de matériaux de structure pérovskite. Dans chaque cas, on décrit les processus de recombinaison des photo-porteurs ainsi que leur lien avec la morphologie et la structuration du matériau. Enfin, les aspects techniques de ces nouvelles méthodes d’analyse sont présentés, ainsi que leurs limites, notamment celles concernant l'interprétation des résultatsThis thesis is directed towards the proposition and demonstration of a set of novel advanced atomic force microscopy based techniques under ultra-high vacuum conditions, enabling to map simultaneously the surface topography and the photo-carrier dynamics at the nanometre scale. In fact, by monitoring the dependence of the average surface photo-voltage measured with Kelvin probe force microscopy, as a function of the repetition frequency of a modulated excitation source, we will access the built-up and decay dynamics of the surface photo-voltage response which in turn will allows us to study the photo-carrier dynamics over a wide range of samples. In order to enable the 2-dimensional nano-imaging process, Kelvin probe force microscopy under modulated illumination measurements are acquired repeatedly over each point of a predefined grid area over the sample acquiring a set of spectroscopy curves. Then, using an automatic mathematical fit procedure, spectroscopy curves are translated into pixels of the photo-carrier dynamic time-constant images.Moreover, these set of novel techniques will be used to investigate the surface photo-voltage dynamics in several kinds of photovoltaic samples from different technological branches such as small grain polycrystalline silicon thin films, silicon nanocrystal-based third generation cells, bulk heterojunction donor-acceptor organic photovoltaics and organic-inorganic hybrid perovskite single crystal cells, discussing in each case the photo-carrier recombination process and its relation with the material’s structuration/morphology. Finally, technical aspects of these novel techniques will be discussed as well as their limitations and remaining open question regarding results interpretation