Dissertations / Theses on the topic 'Virtual Organic Solar Cell'

This project is an extension of a pre-existing simulation program (‘Simulation_2dioden’). This simulation program was first developed in Konarka Technologies. The main purpose of the project ‘Simulation_2dioden’ is to calibrate the values of different parameters like, Shunt resistance, Series resistance, Ideality factor, Diode current, epsilon, tau, contact probability, AbsCT, intensity, etc; This is one of the curve fitting procedure’s. This calibration is done by using different equations. Diode equation is one of the main equation’s used in calculating different currents and voltages, from the values generated by diode equation all the other parameters are calculated.

The reason for designing this simulation_2dioden is to calculate the values of different parameters of a device and the researcher would know which parameter effects more in the device efficiency, accordingly they change the composition of the materials used in the device to acquire a better efficiency. The platform used to design this project is ‘Microsoft Excel’, and the tool used to design the program is ‘Visual basics’. The program could be otherwise called as a ‘Virtual Solar cell’. The whole Virtual Solar cell is programmed in a single excel sheet.

An Automated working solution is suggested which could save a lot of time for the researchers, which is the main aim of this project. To calibrate the parameter values, one has to load the J-V characteristics and simulate the program by just clicking one button. And the parameters extracted by using this automated simulation are Parallel resistance, Series resistance, Diode ideality, Saturation current, Contact properties, and Charge carrier mobility.

Finally, a basic working solution has been initiated by automating the simulation program for calibrating the parameter values.

Finding renewable sources of energy is becoming an increasingly important component of scientific research. Greater competition for existing sources of energy has strained the world’s supply and demand balance and has increased the prices of traditional sources of energy such as oil, coal, and natural gas. The experiment discussed in this paper is designed to identify and build an inexpensive and simple method for creating an effective organic solar cell.

This thesis describes studies on nanohybrid systems consisting of single-walled carbon nanotubes (SWNTs) with monolayer coatings of semiconducting polymers. Steady-state and time-resolved optical and high-resolution microscopy experiments were used to investigate the blends. These materials show promise for use in organic photovoltaics (OPVs) owing to the high carrier mobilities and large aspect ratios of SWNTs, the controllable solubilisation of tubes with various polymers and the broad light-harvesting abilities of organic polymers. Chapters 1 and 2 introduce the theory and background behind the work and present a literature review of previous work utilising carbon nanotubes in OPV devices, revealing poor performances to date. The experimental methods used during the thesis are detailed in Chapter 3 and the solution processing techniques used to prepare the polymer–nanotube blend samples are described in Chapter 4. Chapter 5 describes a study on a nanotube blend with a thiophene polymer, a system previously unsuccessfully implemented into OPV devices. Ultrafast spectroscopic measurements showed that electrons can transfer on a 400 fs time scale from the polymer to nanotubes and the conditions to allow long-lived free charges to be produced were found. The study is extended in Chapter 6 to show that nanostructures consisting of a nanotube coated in one polymer can then be coated by a second polymer and that these nano-engineered structures could be implemented into OPV devices. The use of a competition binding process to isolate purely semiconducting nanotubes dispersed with any desired polymer is then described in Chapter 7. Finally, Chapter 8 introduces systems consisting of chains of porphyrin units, nature’s light-harvesting systems, bound to nanotubes and the blends were found to exhibit the required electronic alignment for use in OPVs. The work described in this thesis provides an explanation for the poor device behaviour of nanotube–polymer blends to date and, in particular, demonstrates several nanohybrid systems that show particular promise for improved OPV applications.

The tandem solar cell concept is a promising approach to improve the efficiency of photovoltaic devices. However, characterization of tandem solar cell devices is challenging since correct efficiency determination demands special experimental infrastructure as well as suitable characterization procedures. Even though the appropriate IEC and ASTM measurement standards define all that very precisely, they cannot be applied without special care to organic photovoltaics (OPV) because they were originally developed for inorganic devices. As a consequence, nowadays almost all tandem organic solar cell publications are not using correct characterization procedures, often resulting in questionable efficiency values. The aim of this work is developing a measurement procedure for tandem organic solar cells assuring their correct characterization. Therefore, at first the existing standards and measurement procedures for tandem solar cells are reviewed and challenges when applying these standards to organic solar cells are identified. As main challenges the relatively low fill factors and distinct nonlinearities of organic solar cells are identified. As preliminary experiments, single junction organic solar cells are investigated to analyze the influence of measurement parameters like bias irradiance, bias voltage, and chopper frequency on the external quantum efficiency (EQE) of organic solar cells. This results in parameter sets assuring minimized artifacts for the subsequent EQE determination of the subcells of tandem organic solar cells. The main part of this thesis presents the detailed characterization of a tandem OPV example device. First, EQE is measured and validated by two independent institutes. The EQE results are used to calculate the illumination conditions to reach AM1.5g conditions for both subcells with a multi-source sun simulator. The resulting efficiency value under standard reporting conditions (SRC) is found to be 5% lower than the efficiency measured with a single-source sun simulator. A full spectrometric characterization shows that differing fill factors of the subcells are the reason for this behavior. To overcome the main reason for the complicated measurement procedure of tandem solar cells, the inaccessibility of the individual subcells, three different approaches for the jV-characteristics determination of the subcells are presented. The so-called Bias Voltage Approach is based on EQE-measurements under varying bias voltage and needs no additional electrical contacts. Therefore, it can be applied to existing devices. The Voltage Contact Approach as well as the Current Contact Approach require in changed stack designs. Therefore, they cannot be applied to existing devices but give more accurate results. Finally, a procedure for characterizing tandem organic solar cells is formulated. This procedures aims at giving practical advice how to characterize tandem organic solar cells to achieve results conforming to the measurement standards and being as accurate and reproducible as possible. Hence, this thesis attempts to establish standards for a correct measurement of tandem organic solar cells of which other emerging solar cell technologies can profit as well.

This thesis deals with the device physics of organic solar cells. Organic photovoltaics (OPV) is a field of applied research which has been growing rapidly in the last decade leading to a current record value of power-conversion efficiency of 10 percent. One major reason for this boom is a potentially low-cost production of solar modules on flexible (polymer) substrate. Furthermore, new application are expected by flexible or semitransparent organic solar cells. That is why several OPV startup companies were launched in the last decade. Organic solar cells consist of hydrocarbon compounds, deposited as ultrathin layers (some tens of nm) on a substrate. Absorption of light leads to molecular excited states (excitons) which are strongly bound due to the weak interactions and low dielectric constant in a molecular solid. The excitons have to be split into positive and negative charges, which are subsequently collected at different electrodes. An effective dissociation of excitons is provided by a heterojunction of two molecules with different frontier orbital energies, such that the electron is transfered to the (electron) acceptor and the positive charge (hole) remains on the donor molecule. This junction can be realized by two distinct layers forming a planar heterojunction or by an intermixed film of donor and acceptor, resulting in a bulk heterojunction. Electrodes are attached to the absorber to collect the charges by providing an ohmic contact in the optimum case. This work focuses on the electrical processes in organic solar cells developing and employing a one-dimensional drift-diffusion model. The electrical model developed here is combined with an optical model and covers the diffusion of excitons, their separation, and the subsequent transport of charges. In contrast to inorganics, charge-carrier mobilities are low in the investigated materials and charge transport is strongly affected by energy barriers at the electrodes. The current-voltage characteristics (J-V curve) of a solar cell reflect the electrical processes in the device. Therefore, the J-V curve is selected as means of comparison between systematic series of simulation and experimental data. This mainly qualitative approach allows for an identification of dominating processes and provides microscopic explanations. One crucial issue, as already mentioned, is the contact between absorber layer and electrode. Energy barriers lead to a reduction of the power-conversion efficiency due to a decrease in the open-circuit voltage or the fill factor by S-shaped J-V curve (S-kink), which are often observed for organic solar cells. It is shown by a systematic study that the introduction of deliberate barriers for charge-carrier extraction and injection can cause such S-kinks. It is explained by simulated electrical-field profiles why also injection barriers lead to a reduction of the probability for charge-carrier extraction. A pile-up of charge carriers at an extraction barrier is confirmed by measurements of transient photocurrents. In flat heterojunction solar cells an additional reason for S-kinks is found in an imbalance of electron and hole mobilities. Due to the variety of reasons for S-kinks, methods and criteria for a distinction are proposed. These include J-V measurements at different temperatures and of samples with varied layer thicknesses. Most of the studies of this this work are based on experimental data of solar cells comprisiing the donor dye zinc phthalocyanine and the acceptor fullerene C60. It is observed that the open-circuit voltage of these devices depends on the mixing ratio of ZnPc:C60. A comparison of experimental and simulation data indicates that the reason is a changed donor-acceptor energy gap caused by a shift of the ionization potential of ZnPc. A spatial gradient in the mixing ratio of a bulk heterojunction is also investigated as a donor(acceptor)-rich mixture at the hole(electron)-collecting contact is supposed to assist charge extraction. This effect is not observed, but a reduction of charge-carrier losses at the “wrong” electrode which is seen at an increase in the open-circuit voltage. The most important intrinsic loss mechanism of a solar cell is bulk recombination which is treated at the example of ZnPc:C60 devices in the last part of this work. An examination of the dependence of the open-circuit voltage on illumination intensity shows that the dominating recombination mechanism shifts from trap-assisted to direct recombination for higher intensities. A variation of the absorption profile within the blend layer shows that the probability of charge-carrier extraction depends on the locus of charge-carrier generation. This results in a fill factor dependent on the absorption profile. The reason is an imbalance in charge-carrier mobilities which can be influenced by the mixing ratio. The work is completed by a simulation study of the influence of charge-carrier mobilities and different recombination processes on the J-V curve and an identification of a photoshunt dominating the experimental linear photocurrent-voltage characteristics in reverse bias
Diese Dissertation beschäftigt sich mit der Physik organischer Solarzellen. Die organische Photovoltaik ist ein Forschungsgebiet, dem in den letzten zehn Jahren enorme Aufmerksamkeit zu Teil wurde. Der Grund liegt darin, dass diese neuartigen Solarzellen, deren aktueller Rekordwirkungsgrad bei 10 Prozent liegt, ein Potential für eine kostengünstige Produktion auf flexiblem (Polymer)substrat aufweisen und aufgrund ihrer Vielfältigkeit neue Anwendungsbereiche für die Photovoltaik erschließen. Organische Solarzellen bestehen aus ultradünnen (einige 10 nm) Schichten aus Kohlenwasserstoffverbindungen. Damit der photovoltaische Effekt genutzt werden kann, müssen die durch Licht angeregten Molekülzustände zu freien Ladungsträgern führen, wobei positive und negative Ladung an unterschiedlichen Kontakten extrahiert werden. Für eine effektive Trennung dieser stark gebundenden lokalisierten angeregten Zustände (Exzitonen) ist eine Grenzfläche zwischen Molekülen mit unterschiedlichen Energieniveaus der Grenzorbitale erforderlich, sodass ein Elektron auf einem Akzeptor- und eine positive Ladung auf einem Donatormolekül entstehen. Diese Grenzschicht kann als planarer Heteroübergang durch zwei getrennte Schichten oder als Volumen-Heteroübergang in einer Mischschicht realisiert werden. Die Absorberschichten werden durch Elektroden kontaktiert, wobei es für effiziente Solarzellen erforderlich ist, dass diese einen ohmschen Kontakt ausbilden, da ansonsten Verluste zu erwarten sind. Diese Arbeit behandelt im Besonderen die elektrischen Prozesse einer organischen Solarzelle. Dafür wird ein eindimensionales Drift-Diffusionsmodell entwickelt, das den Transport von Exzitonen, deren Trennung an einer Grenzfläche und die Ladungsträgerdynamik beschreibt. Abgesehen von den Exzitonen gilt als weitere Besonderheit einer organischen Solarzelle, dass sie aus amorphen, intrinsischen und sehr schlecht leitfähigen Absorberschichten besteht. Elektrische Effekte sind an der Strom-Spannungskennlinie (I-U ) sichtbar, die in dieser Arbeit als Hauptvergleichspunkt zwischen experimentellen Solarzellendaten und den Simulationsergebnissen dient. Durch einen weitgehend qualitativen Vergleich können dominierende Prozesse bestimmt und mikroskopische Erklärungen gefunden werden. Ein wichtiger Punkt ist der schon erwähnte Kontakt zwischen Absorberschicht und Elektrode. Dort auftretende Energiebarrieren führen zu einem Einbruch im Solarzellenwirkungsgrad, der sich durch eine Verringerung der Leerlaufspanung und/oder S-förmigen Kennlinien (S-Knick) bemerkbar macht. Anhand einer systematischen Studie der Grenzfläche Lochleiter/Donator wird gezeigt, dass Energiebarrieren sowohl für die Ladungsträgerextraktion als auch für die -injektion zu S-Knicken führen können. Insbesondere die Tatsache, dass Injektionsbarrieren sich auch negativ auf den Photostrom auswirken, wird anhand von simulierten Ladungsträger- und elektrischen Feldprofilen erklärt. Das Aufstauen von Ladungsträgern an Extraktionsbarrieren wird durch Messungen transienter Photoströme bestätigt. Da S-Knicke in organischen Solarzellen im Allgemeinen häufig beobachtet werden, werden weitere Methoden vorgeschlagen, die die Identifikation der Ursachen ermöglichen. Dazu zählen I-U Messungen in Abhängigkeit von Temperatur und Schichtdicken. Als eine weitere Ursache von S-Knicken werden unausgeglichene Ladungsträgerbeweglichkeiten in einer Solarzelle mit flachem Übergang identifiziert und von den Barrierefällen unterschieden. Weiterer Forschungsgegenstand dieser Arbeit sind Mischschichtsolarzellen aus dem Donator-Farbstoff Zink-Phthalozyanin ZnPc und dem Akzeptor Fulleren C60. Dort wird beobachtet, dass die Leerlaufspannung vom Mischverhältnis abhängt. Ein Vergleich von Experiment und Simulation zeigt, dass sich das Ionisationspotenzial von ZnPc und dadurch die effektive Energielücke des Mischsystems ändern. Zusätzlich zu homogenen Mischschichten werden Solarzellen untersucht, die einen Gradienten im Mischungsverhältnis aufweisen. Die Vermutung liegt nahe, dass ein hoher Donatorgehalt am Löcherkontakt und ein hoher Akzeptorgehalt nahe des Elektronenkontakts die Ladungsträgerextraktion begünstigen. Dieser Effekt ist in dem hier untersuchten System allerdings vergleichsweise irrelevant gegenüber der Tatsache, dass der Gradient das Abfließen bzw. die Rekombination von Ladungsträgern am “falschen” Kontakt reduziert und somit die Leerlaufspannung erhöht. Der wichtigste intrinsische Verlustmechanismus einer Solarzelle ist die Rekombination von Ladungsträgern. Diese wird im letzten Teil der Arbeit anhand der ZnPc:C60 Solarzelle behandelt. Messungen der Leerlaufspannung in Abhängigkeit von der Beleuchtungsintensität zeigen, dass sich der dominierende Rekombinationsprozess mit zunehmender Intensität von Störstellenrekombination zu direkter Rekombination von freien Ladungsträgern verschiebt. Eine gezielte Variation des Absorptionsprofils in der Absorberschicht zeigt, dass die Ladungsträgerextraktionswahrscheinlickeit vom Ort der Ladungsträgergeneration abhängt. Dieser Effekt wird hervorgerufen durch unausgeglichene Elektronen- und Löcherbeweglichkeiten und äußert sich im Füllfaktor. Weitere Simulationsergebnisse bezüglich des Einflusses von Ladungsträgerbeweglichkeiten und verschiedener Rekombinationsmechanismen auf die I-U Kennlinie und die experimentelle Identifikation eines Photoshunts, der den Photostrom in Rückwärtsrichtung unter Beleuchtung dominiert, runden die Arbeit ab

To mitigate the risk for devastating climate changes, there is an urgent need to change the energy production from the current fossil based to renewable sources. Solar cells will contribute to an increasing share of the future energy systems. Today silicon solar cells dominate the market but printed organic solar cells are promising alternatives in terms of cost, flexibility, possibilities for building integrations and energy payback times. Printing enables roll-to-roll processing that is quick and renders huge volumes. Thus, also characterization and quality control must be fast. Recent tests have been performed showing that a LED array with amplitude modulated LEDs can be used to provide photocurrent images of modules with series connected sub cells in-line during manufacturing. The purpose of this thesis work is to further evaluate and develop this LED array characterization technique focusing on contact methods and signal interpretation. Two modes were examined; a contact mode and a capacitive contact-less mode. Both modes gave comparable results and indicated strong variations in performance of sub cells in the measured modules. Other methods to address individual cells also showed similar behavior. However, by manually adding extra contact points, current-voltage curves could be measured on the individual sub cells in the modules. Extraction of photocurrents were similar, but the parallel resistances varied strongly between the cells in the module. Increasing the frequency of the LEDs resulted in less variations. Calculations indicated that this frequency dependence could be used to separate the photocurrent generation and parallel resistance in the sub cells.

Active layer morphology of polymer-based solar cells plays an important role in improving power conversion efficiency (PCE). In this thesis, the focus is to improve the device efficiency of polymer-based solar cells. In the first objective, active layer morphology of polymer-solar cells was optimized though a novel solvent annealing technique. The second objective was to explore the possibility of replacing the highly sensitive aluminum cathode layer with a low-cost and stable alternative, copper metal. Large scale manufacturing of these solar cells is also explored using roll-to-roll printing techniques. Poly (3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl (PCBM) were used as the active layer blend for fabricating the solar cell devices using bulk heterojunction (BHJ), which is a blend of a donor polymer and an acceptor material. Blends of the donor polymer, P3HT and acceptor, PCBM were cast using spin coating and the resulting active layers were solvent annealed with dichlorobenzene in an inert atmosphere. Solvent annealed devices showed improved morphology with nano-phase segregation revealed by atomic force microscopy (AFM) analysis. The roughness of the active layer was found to be 6.5 nm. The nano-phase segregation was attributed to PCBM clusters and P3HT domains being arranged under the solvent annealing conditions. These test devices showed PCE up to 9.2 % with current density of 32.32 mA/cm2, which is the highest PCE reported to date for a P3HT-PCBM based system. Copper was deposited instead of the traditional aluminum for device fabrication. We were able to achieve similar PCEs with copper-based devices. Conductivity measurements were done on thermally deposited copper films using the two-probe method. Further, for these two configurations, PCE and other photovoltaic parameters were compared. Finally, we studied new techniques of large scale fabrication such as ultrasonic spray coating, screen-printing, and intense pulse light sintering, using the facilities at the Conn Center for Renewable Energy Research at the University of Louisville. In this study, prototype devices were fabricated on flexible ITO coated plastics. Sintering greatly improved the conductivity of the copper nano-ink cathode layer. We will explore this technique’s application to large-scale fabrication of solar cell devices in the future work.

This work investigates organic solar cells made of small molecules. Using the material system α,ω-bis(dicyanovinylene)-sexithiophene (DCV6T) - C60 as model, the correlation between the photovoltaic active layer morphology and performance of the solar cell is studied. The chosen method for controlling the layer morphology is applying different substrate temperatures (Tsub ) during the deposition of the layer. In neat DCV6T layers, substrate heating induces higher crystallinity as is shown by X-ray diffraction and atomic force microscopy (AFM). The absorption spectrum displays a more distinct fine structure, a redshift of the absorption peaks by up to 11 nm and a significant increase of the low energy absorption band at Tsub = 120°C compared to Tsub = 30°C. Contrary to general expectations, the hole mobility as measured in field effect transistors and with the method of charge extraction by linearly increasing voltage (CELIV) does not increase in samples with higher crystallinity. In mixed layers, investigations by AFM and UV-Vis spectroscopy reveal a stronger phase separation induced by substrate heating, leading to larger domains of DCV6T. This is indicated by an increased grain size and roughness of the topography, the increase of the DCV6T luminescence signal, and the more distinct fine structure of the DCV6T related absorption. Based on the results of the morphology analysis, the effect of different substrate temperatures on the performance of solar cells with flat and mixed DCV6T - C60 heterojunctions is investigated. In flat heterojunction solar cells, a slight increase of the photocurrent by about 10% is observed upon substrate heating, attributed to the increase of DCV6T absorption. In mixed DCV6T : C60 heterojunction solar cells, much more pronounced enhancements are achieved. By varying the substrate temperature from -7°C to 120°C, it is shown that the stronger phase separation upon substrate heating facilitates the charge transport, leading to a significant increase of the internal quantum efficiency (IQE), photocurrent, and fill factor. Consequently, the power conversion efficiency (PCE) increases from 0.5% at Tsub = -7°C to about 3.0 % at Tsub ≥ 77°C. Subsequent optimization of the DCV6T : C60 mixing ratio and the stack design of the solar cell lead to devices with PCE of 4.9±0.2 %. Using optical simulations, the IQE of these devices is studied in more detail to identify major remaining loss mechanisms. The evaluation of the absorption pattern in the wavelength range from 300 to 750 nm shows that only 77 % of the absorbed photons contribute to the exciton generation in photovoltaic active layers, while the rest is lost in passive layers. Furthermore, the IQE of the photovoltaic active layers, consisting of an intrinsic C60 layer and a mixed DCV6T : C60 layer, exhibits a lower exciton diffusion efficiency for C60 excitons compared to DCV6T excitons, attributed to exciton migration into the adjacent electron transport layer
Diese Arbeit befasst sich mit organischen Solarzellen aus kleinen Molekülen. Anhand des Materialsystems α,ω-bis(Dicyanovinylen)-Sexithiophen (DCV6T) - C60 wird der Zusammenhang zwischen Morphologie der photovoltaisch aktiven Schicht und dem Leistungverhalten der Solarzellen untersucht. Zur Beeinflussung der Morphologie werden verschiedene Substrattemperaturen (Tsub ) während des Schichtwachstums der aktiven Schicht eingestellt. Beim Heizen des Substrates weisen DCV6T Einzelschichten eine erhöhte Kristallinität auf, die mittels Röntgenbeugung und Rasterkraftmikroskopie (AFM) erkennbar ist. Zudem bewirkt die Erhöhung der Substrattemperatur von 30°C auf 120°C eine ausgeprägtere Feinstrukturierung des Absorptionsspektrums, eine Rotverschiebung um bis zu 11 nm und eine Verstärkung der niederenergetischen Absorptionsbande. Entgegen den Erwartungen wird weder in Feldeffekttransistoren noch mit der Methode der Ladungsextraktion bei linear steigenden Spannungspulsen (CELIV) eine Verbesserung der Löcherbeweglichkeit in Zusammenhang mit der erhöhten Kristallinität gemessen. Mischschichten mit C60 weisen bei erhöhten Substrattemperaturen eine stärkere Phasentrennung auf, die zu größeren DCV6T Domänen innerhalb der Schicht führt. Dieser Effekt wird zum Einen durch größere Körnung und Rauigkeit der Topographie, zum Anderen durch die Erhöhung des Lumineszenzsignals von DCV6T sowie der Ausprägung der Feinstruktur im Absorptionsspektrum nachgewiesen. Ausgehend von den Ergebnissen der Morphologieuntersuchung werden die Auswirkungen von verschiedenen Substrattemperaturen auf das Leistungsverhalten von DCV6T - C60 Solarzellen mit planarem und Volumen-Heteroübergang analysiert. Solarzellen mit planarem Heteroübergang weisen eine geringe Verbesserung des Photostromes von etwa 10 % beim Heizen des Substrates auf. Diese wird durch die Erhöhung der DCV6T Absorption verursacht. In Volumen-Heteroübergängen führt die stärkere Phasentrennung bei steigender Substrattemperatur im untersuchten Temperaturbereich von -7°C bis 120°C zu einer Verbesserung des Ladungsträgertransports. Dadurch verbessern sich die interne Quanteneffizienz (IQE), der Photostrom und der Füllfaktor. Der Wirkungsgrad der Solarzellen erhöht sich von 0.5 % bei Tsub = -7°C auf 3.0 % bei Tsub ≥ 77°C. Eine weitere Optimierung des DCV6T : C60 Mischverhältnisses und des Schichtaufbaus ermöglicht Solarzellen mit Wirkungsgraden von 4.9±0.2 %. Mittels optischer Simulationen wird die IQE dieser Solarzellen näher untersucht, um verbleibende Verlustmechanismen zu identifizieren. Es ergibt sich, dass innerhalb des Wellenlängenbereichs von 300 bis 750 nm nur 77 % der absorbierten Photonen tatsächlich in den photovoltaisch aktiven Schichten absorbiert werden, während der Rest in nicht aktiven Schichten verloren geht. Des Weiteren kann nachgewiesen werden, dass C60 Exzitonen aus der aktiven Schicht, bestehend as einer intrinsischen C60 Schicht und einer DCV6T : C60 Mischschicht, durch Diffusion in die angrenzende Elektronentransportschicht verloren gehen

Using several organic electron donor and electron acceptor materials, solution cast blend films were studied to better understand charge separation and excited state formation in thin films for organic solar cell applications.

Transferring organic photovoltaics (OPV) from the laboratory into economically feasible products, requires the fabrication of modules, a series of connected single cells. During this transition, there is typically a drastic decrease in power conversion efficiency (PCE). This thesis reports on the design, fabrication, and characterization of state-of-the-art, high-performance organic photovoltaic modules with a novel geometry that composed of unit cells with alternating electrical polarities. Such configuration is realized by exclusive patterning of the interlayers and electrodes and avoids patterning of the photoactive layer. With this novel architecture, area losses of photovoltaic module can be significantly reduced compared with the conventional configurations. The processing of this new solar cell module is also compatible with large area processing techniques such as slot-die coating. This thesis reports on 4-cell and 8-cell modules, wherein the measured fill-factors (FF) and PCE of the constituent sub-cells and of the modules are almost identical. The 4-cell module, with a total area of 0.8 cm2, exhibits an open-circuit voltage (VOC) of 3.15 V, a short circuit-current density (JSC) of 2.3 mA/cm2 and a FF of 0.69, yielding a PCE of 5.01%. The 8-cell module, with a total area of 1.6 cm2, exhibits a VOC of 6.39 V, a JSC of 1.2 mA/cm2 and a FF of 0.63, yielding a PCE of 5.06%. Similar PCE values between 4-cell and 8-cell module is a demonstration of scalability of this novel geometry without compromising the efficiency.

Organic solar cells have emerged as an important cheap photovoltaic technology. In this thesis work, a study of P3HT:PCBM heterojunction solar cells was presented. By incorporation of photo-active film slow growth, PEDOT:PSS (Poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate)) de-water treatment and application of highly conductive PEDOT:PSS (HC-PEDOT), a maximum PCE (power conversion efficiency) of 4% was achieved.

Inkjet printing technique was on the other hand introduced into fabrication process. The morphological, electrical and optical properties of printed HC-PEDOT were investigated. Fine silver girds with well-designed pattern, combining with a transparent thin film of HC-PEDOT, was inkjet-printed to form the anode of solar cells. A functional device with printed anode and printed photo-active layer was demonstrated, showing the possibility of realizing fully printed organic solar cells.

 

Organic donor and acceptor have promised the better future energy technologies to alleviate global energy demand and environmental issues. And nowadays they begin to come true in bulk heterojunction organic solar cells (BHJ OSCs) with advantages of low-cost, light-weight, large-area, flexibility, and with high efficiencies (PCEs) of over 14% for converting solar energy to electricity. Porphyrins are unique potential for artificial photocatalysis but their application in BHJ OSCs are still limited by the PCEs less than 10%. This complicacy comes from their inadequate spectral absorptions and the imperfect morphologies. In this thesis, we devote to chemical modification of acceptor-π-porphyrin-π-acceptor (A-π-Por-π-A) structural molecules to enhance their spectral absorptions and phase-separation functions with fullerene acceptor. Firstly, chemically driving J-aggregates have been studied on the new A-π-Por-π-A porphyrin molecule, which could improve the phase-separation of its blend film with PC71BM and and enhance its performance in BHJ OSCs with PCE up to 8.04%. Secondly, two new benzodithiophene (BDT) π-bridged A-π-Por-π-A molecules have been prepared with complementary absorption between the Soret and Q bands. The devices based on the blend fims of the porphyrin donor and PC71BM acceptor exhibit full spectral photocurrent generation and impressive PCEs up to 7.92%. Thirdly, we further extended the π-conjugation of the above BDT π-brigded A-π-Por-π-A molecules by inserting alkyl chain substituted thiophene derivatives into their backbones, resulting in new porphyrin molecules with UV-visible-near-infraed absorption spectra. Using those porphyrin molecules as donor and PCBM as acceptor, the devices show full spectra photocurrent generatoion and appropriate film morphology, resulting in high PCE up to 8.59%. Besides, photocatalysis is also a new promising technology to generate renewable energy. We herein develop new low-cost and noble-metal-free photocatalysts based on Co(OH)2 modified CdS nanowires and applied them for visible light driven hydrogen production from water-splitting. The optimum H2 production rate reaches 14.43 mmol·h−1·g−1 under (λ ≥ 420 nm) upon visible light irradiation, which is 206 and 3 times larger than that of the pristine CdS NWs and 1 wt% Pt-CdS NWs, respectively. The results indicate the promising application of earth-abundant Co(OH)2 as alternative cocatalysts of noble metals.

A hole-collecting interlayer layer for organic solar cells, NiO, processed by atomic layer deposition (ALD) was studied. ALD-NiO film offered a novel alternative to efficient hole-collecting interlayers in conventional single-junction organic solar cells. Next, surface modifications with aliphatic amine group containing polymers for use as electron-collecting interlayers were studied. Physisorption of the polymers was found to lead to large reduction of the work function of conducting materials. This approach provides an efficient way to provide air-stable low-work function electrodes for organic solar cells. Highly efficient inverted organic solar cells were demonstrated by using the polymer surface modified electrodes. Lastly, charge recombination layers of the inverted tandem organic solar cells were studied. Efficient charge recombination layers were realized by using the ALD and the polymer surface modification. The charge recombination layer processed by ALD provided enhanced electrical and barrier properties. Furthermore, the polymer surface modification on the charge recombination layers showed large work function contrast, leading to improved inverted tandem organic solar cells. The inverted tandem organic solar cells with the new charge recombination layer showed fill factor over 70% and power conversion efficiency over 8%.

In recent decades, research and development of organic based semiconductor devices have attracted intensive interests. One of the most essential elements is to understand the electronic structures at various interfaces involved in these devices since the interface properties control many of the critical electronic processes. It is thus necessary to study the electronic properties of the organic semiconductors with surface analytical tools to improve the understanding of the fundamental mechanisms involved in the interface formation. This thesis covers the experimental investigations on some of the most interesting topics raised in the recent development of organic electronic devices. The thesis intends to reveal the physical processes at the interface and their contribution to the device performance with photoemission and inverse photoemission investigations on the evolution of the occupied and unoccupied electronic structures. I will report a substantial difference in the electron affinity of CuPc on two substrates as the orientations of CuPc are different. I will also illustrate that the CuPc has standing up configuration on one monolayer of C60 on SiO2 while lying down on one monolayer of C60 on HOPG. Meanwhile, the CuPc on more than one monolayers of C60 on different substrates show that the substrate orientation effect vanished. Then I will propose a two-stage model to describe the bulk doping effect of C60 by molybdenum oxide. I will also demonstrate that the doping effect of C60 by ultra-thin layer molybdenum oxide is weaker than that by interface doping and bulk doping. I will demonstrate that for Au on CH3NH3PbI3, hole accumulation occurs at the vicinity of the interface, facilitating hole transfer from CH3NH3PbI3 to Au. I will show a strong initial shift of core levels to lower binding energy in C60 on CH3NH3PbI3 interface, which indicates that electrons transfer from the perovskite film to C60 molecules. I will further demonstrate that the molybdenum oxide surface can be passivated by approximately two monolayers of organic thin films against exposure to air. I will discuss the mechanism that how oxygen plasma treatment effectively recover the high work function drop of molybdenum oxide by air exposure. At the end, I will show that a small energy offset at Pentacen/C60 heterojunction makes it easy to transfer electrons from Pentacene to C60 even under a small applied bias, facilitating the occurrence of charge generation. Finally, I will summarize the thesis.

Organic photovoltaic (OPV) cells are advanced, newly emerging technologies that are lightweight, mechanically flexible devices with highthroughput processes from low cost material in a variety of colors. Rathnayake et al. of Western Kentucky University have developed a nanostructure-based OPV cell. Presented in this thesis is a model and simulation of a generalized PV powered system that can predict the performance of solar arrays in various environmental conditions. The simulation has been carried out in Matlab/Simulink, and upon entering the cell’s parameters, it provides key electrical characteristics such as the cell’s I-V curve and efficiency information. The total system that is simulated consists of three elements: a universal two-cell solar array that can account for partial shading and manufacturing variation, a current-controlled power converter, and an energy storage device with charging and discharging capabilities.

Organic solar cells promise electricity generation at very low cost, and higher installation flexibility as compared to inorganic solar cells. The lower cost is achieved by cheaper semiconductors and easier manufacturing processes. The flexibility is naturally given by these ultra-thin, amorphous layers. Also the power conversion efficiency can be high enough for many applications. The organic molecules have to withstand the constant excitation by photons, transport of energy in form of excitons and charge. A small but significant amount of these photons has energy over the absorption gap, the excess of energy must be released without breaking the molecular bonds. In consequence, the solar cells can also heat up to temperatures at above 80°C. The objective of this work is to answer the question if the small molecules organic solar cells can be stable enough to operate under a very long time. The stability of organic doped layers in an organic solar cell is also addressed. This work starts with a general introduction followed by the description of the experimental procedures. The aging experiments of the solar cell were done with a self developed equipment. The fabrication of this equipment (a set of measurement boxes) was necessary to maintain the conditions, under which a solar cell can be aged, as constant as possible. The measurement boxes were used to control the electrical load of the cell, its temperature, the illumination intensity, and its electric connection to the IxV measurement equipment. A software package was also developed to control the equipment and to facilitate the work and visualization of the high volume of collected data. The model solar cells chosen for the aging experiments were donor-acceptor heterojunctions devices formed with the well-known materials C60 and ZnPc. Two basic different structures were analyzed, because they offered reasonable performance and potentially long lifetime: the flat heterojunction (FHJ) and the mixed heterojunction in a Metal-Insulator-p-Semiconductor (m-i-p) configuration. Variations of the FHJ and of the m-i-p structures are also used to verify the limits of the stability of electrically p- and n- doped organic semiconducting layers. The least stable solar cells are the FHJ devices. These devices show a fast initial decrease of all their characteristic conversion parameters but the Voc. After a few hundred hours, the saturation current (current under a reverse bias of 1 V) was almost stable. The saturation current is related to the number of absorbing centers, the decrease indicates that the degradation of the absorbing centers has stopped. With wavelength resolved external quantum efficiency measurements and chemical analysis, it was found that the degradation is related to the oxidation of C60. It was also shown that the use of organic dopants do not significantly affect the lifetime. The results show that the m-i-p solar cells are more stable than the FHJ devices. They are also stable under high temperatures up to 105°C. Outdoor testing also showed that the solar cells remained chemically, electrically and mechanically stable during a 900 h test.

Das wesentliche Ziel dieser Doktorarbeit ist es, die Zusammenhänge zwischen der Struktur von kleinen organischen Molekülen, deren Anordnung in der Dünnschicht und der Effizienz organischer Solarzellen zu beleuchten. Die Kombination der komplementären Methoden spektroskopischer Ellipsometrie (VASE) und Röntgenstreuung, vor allem der unter streifendem Einfall (GIXRD), hat sich als sehr effiient für die Strukturuntersuchungen organischer Dünnschichten erwiesen. Zusammen geben sie einen detailreichen Einblick in die intermolekulare Anordnung, die Kristallinität, die molekulare Orientierung, die optischen Konstanten n und k und die Phasenseparation von organischen Schichten. Zusätzlich wird die Topografie der organischen Dünnschicht mit Rasterkraftmikroskopie untersucht. Der erste Fokus liegt auf der Analyse des Dünnschichtwachstums von Zink-Phthalocyanin (ZnPc) Einzelschichten. Für alle untersuchten Schichtdicken (5, 10, 25, 50 nm) und Substrattemperaturen (Tsub=30°C, 60°C, 90°C) zeigt ZnPc ein kristallines Schichtwachstum mit aufrecht stehenden ZnPc Molekülen. Um effiziente organische Solarzellen herzustellen, werden Donor- und Akzeptormoleküle üblicherweise koverdampft. Bei der Mischung von Donor- und Akzeptormolekülen bildet sich eine gewisse Phasenseparation aus, deren Form wesentlich für die Ladungsträgerextraktion entlang der Perkolationpfade ist. Der Ursprung dieser Phasenseparation wird innerhalb dieser Arbeit experimentell für ZnPc:C60 Absorber-Mischschichten untersucht. Um die Ausprägung der Phasenseparation zu variieren, werden verschiedene Tsub (30°C, 100°C, 140°C) und Mischverhältnisse (6:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:6) bei der Koverdampfung von ZnPc und C60 angewendet. GIXRD Messungen zeigen, dass hier der bevorzugte Kristallisationsprozess von C60 Molekülen die treibende Kraft für eine effiziente Phasenseparation ist. Solarzellen, die ZnPc:C60 Mischschichten mit verbesserter Phasenseparation enthalten (Tsub=140°C, 1:1), zeigen eine verbesserte Ladungsträgerextraktion und somit eine höhere Effizienz von 3,0% im Vergleich zu 2,5% für die entsprechende Referenzsolarzelle (Tsub=30°C, 1:1). Im zweiten Teil der Arbeit wird der Einfluss der Molekülorientierung auf die Dünnschichtabsorption beispielhaft an ZnPc und Diindenoperylen (DIP) untersucht. DIP und ZnPc Moleküle, die auf schwach wechselwirkenden Substraten wie Glas, SiO2, amorphen organischen Transportschichten oder C60 aufgedampft sind, zeigen eine eher stehende Orientierung innerhalb der Dünnschicht in Bezug zur Substratoberfläche. Im Gegensatz dazu führt die Abscheidung auf stark wechselwirkenden Substraten, wie z.B. einer Gold- oder Silberschicht oder 0.5 nm bis 2 nm dünnen PTCDA (3,4,9,10-Perylentetracarbonsäuredianhydrid) Templatschichten laut GIXRD und VASE Messungen dazu, dass sich die ZnPc und DIP Moleküle eher flach liegend orientieren. Dies führt zu einer wesentlich besseren Dünnschichtabsorption da das molekulare Übergangsdipolmoment jeweils innerhalb der Ebene des ZnPc und des DIP Moleküls liegt. Ein Einbetten von Gold- oder Silberzwischenschichten in organischen Solarzellen führt leider zu keinen klaren Abhängigkeiten, da die verbesserte Absorption durch die flach liegenden Moleküle von Mikrokavitäts- und plasmonischen Effekten überlagert wird. Ebenso wenig führte das Einfügen einer PTCDA-Zwischenschicht in organischen Solarzellen zum Erfolg, da hier Transportbarrieren den Effekt der verbesserten Absorption überlagern. Das letzte Kapitel konzentriert sich auf den Einfluss der Molekülstruktur auf das Dünnschichtwachstum am Beispiel von DIP und dessen Derivaten Ph4-DIP und P4-Ph4-DIP, Isoviolanthron und Bis-nFl-NTCDI (N,N-Bis(fluorene-2-yl)-naphthalenetetra-carboxylic Diimid) Derivaten. GIXRD Messungen belegen deutlich, dass die sterischen Behinderungen, hervorgerufen durch die Phenylringe (für Ph4-DIP und P4-Ph4-DIP) und Seitenketten (für Bis-nFl-NTCDI), ein amorphes Schichtwachstum induzieren. Im Vergleich sind die Dünnschichten von DIP und Bis-HFl-NTCDI kristallin. Bezüglich der Molekülorientierung und folglich der Absorption von DIP und dessen Derivaten kann ein starker Einfluss des Schichtwachstums beobachtet werden. In Solarzellen verhindert die Präsenz der Phenylringe eine effiziente Phasenseparation der Mischschichten aus (P4-)Ph4-DIP:C60, was zu einer verschlechterten Ladungsträgerextraktion und damit zu einem reduzierten Füllfaktor (FF) von 52% im Vergleich zu dem entsprechender DIP:C60 Solarzellen mit FF=62% führt Die Untersuchungen an der Bis-nFl-NTICDI Serie zeigen ein ähnliches Ergebnis: Auch hier zeichnen sich die amorphen Schichten aus Bis-nFl-NTCDI Molekülen mit Seitenketten durch schlechtere Transporteigenschaften aus als nanokristalline Bis-HFl-NTCDI Schichten
The aim of this thesis is to demonstrate correlations between the molecular structure of small organic molecules, their arrangement in thin films, and the solar cell performance. For structure analysis of the organic thin films, the combination of variable angle spectroscopic ellipsometry (VASE) and grazing incidence X-ray diffraction (GIXRD) as complementary methods turned out to be a powerful combination. Using both methods, it is possible to obtain information about the crystallinity, crystallite size, intermolecular arrangement, mean molecular orientation, optical constants n and k, and phase separation within thin films. In addition, the topography of thin films is analyzed by atomic force microscopy. First, the thin film morphology of pristine zinc-phthalocyanine (ZnPc) films deposited at different substrate temperatures (Tsub=30°C, 60°C, 90°C) and for varying film thicknesses (5, 10, 25, 50 nm) is investigated. The ZnPc films grow highly crystalline with an upright standing molecular orientation with respect to the substrate surface for all investigated Tsub and all film thicknesses. In effcient organic solar cells, donor and acceptor molecules are commonly co-deposited to form a blend absorber film. This is usually accompanied by a certain phase separation between donor and acceptor molecules leads to a formation of percolation paths necessary to extract electrons and holes towards the electrodes. For ZnPc:C60 blends the origin of this phase separation process is analyzed by investigating different degrees of phase separation induced by film deposition at different Tsub (30°C, 100°C, 140°C) and for different blend ratios (6:1, ... , 1:6 (vol%)). GIXRD measurements indicate that the preferred crystallization of C60 is the driving force for good phase separation. Solar cells with improved phase separation of ZnPc:C60 blends (Tsub=140°C, 1:1) reveal a better charge carrier extraction and thus enhanced effciencies of 3.0% in comparison to 2.5% for the reference device (Tsub=30°C, 1:1). In the second part, the impact of molecular orientation within the absorber thin films on light harvesting is examined for pristine ZnPc and diindenoperylene (DIP) films. For film deposition on weakly interacting substrates like glass, SiO2, amorphous organic transport films, or C60, the orientation of DIP and ZnPc molecules is found to be upright standing. In contrast, GIXRD and VASE measurements show that films deposited onto strongly interacting substrates like Au and Ag, as well as on thin PTCDA templating layers lead to nearly flat-lying ZnPc and DIP molecules. Since the molecular transition dipole moment is oriented in the plane of the DIP and ZnPc molecules, the light absorption in films with flat-lying molecules is strongly improved. Unfortunately, an implementation of Au or Ag sublayers in organic solar cells does not result in reliable dependencies since the enhanced absorption by an improved molecular orientation is superimposed by different effects like microcavity and plasmonic effects. The implementation of PTCDA interlayers leads to transport barriers making the solar cell data interpretation difficult. In the last part, the influence of molecular structure on thin film growth is studied for DIP and its derivatives Ph4-DIP and P4-Ph4-DIP, isoviolanthrone, and Bis-nFl-NTCDI derivatives. GIXRD measurements reveal that steric hindrance is induced by the addition of side chains (for Bis-nFl-NTCDI) and phenyl rings (for Ph4-DIP and P4-Ph4-DIP) (N,N-Bis(fluorene-2-yl)-naphthalenetetra-carboxylic diimide) leading to an amorphous thin film growth. In contrast, DIP films and Bis-HFl-NTCDI films are found to be crystalline. The mean molecular orientation and hence the absorption is strongly affected by the different growth modes of DIP and its derivatives. In OSC, the presence of the phenyl rings prevents an effcient phase separation for (P4-)Ph4-DIP:C60 blends which causes diminished charge extraction in comparison to the crystalline DIP:C60 blends. For the Bis-nFl-NTCDI series, the transport properties are significantly worse in the amorphous films composed of Bis-nFl-NTCDI derivatives with alkyl chains in comparison to the nanocrystalline films made of the bare Bis-HFl-NTCDI

This project aims to synthesize and characterize Lead-free Methylammonium and Formamidinium based photosensitizers (dyes). The objectives of this project are to develop and characterize two types of photosensitizer: Methylammonium Titanium-based and Formamidinium Titanium-based dyes. X-ray diffraction and UV-Vis spectrophotometry were used to investigate the crystalline structure of both and determine their optical band gaps, respectively. Both dyes were heated at different temperatures for different heating times to prepare them for testing and characterization. Eight samples of Methylammonium Titanium-based dye were heated at 70, 80, 100, 120, 130 and 140°C for 10 minutes and for 100 and 120°C for 20 minutes. Sixteen samples of Formamidinium Titanium-based dye were heated at 80, 100, 120 and 130°C each for 10, 20, 40 and 60 minutes. It was found out that the treatment temperature and duration have different effects on the crystalline structure and band gap. The best band gap of 2.32 eV value was obtained for Methylammonium Titanium based dye when it was heated at 140°C for 10 minutes and the best one for Formamidinium Titanium based dye was of a 2.38 eV value obtained when it was heated at 120°C for 10 minutes. After that, two photovoltaic cells were fabricated using the two dyes and then tested under constant source of voltage (at 0.5 V) and their current response was tested when the light was shining and when it was not. Two types of lights were used, UV (50 µW/cm2 density) and white (60 µW/cm2 density). The results showed that the two dyes are photoactive.

Organic molecules based photovoltaic cells were fabricated in an open laboratory conditions without the use of glove box or clean room. Conducting polymers such as P3HT and PCBM were used as a photo-active layer of the devices. We found significant difference in the performance of the devices by employing two laboratory conditions of the polymer solutions. Enhanced current density has been observed from P3HT/PCBM bulkheterojunction solar cell after diluting a well sonicated polymers solution with fresh chloroform solvent. As the result of such current surge in the devices the efficiency rose to more than double compared to those devices without dilution of the P3HT/PCBM solution. An average power conversion efficiency of 4.5% was then recorded from the new preparation condition. This is an encouraging development toward achieving low cost organic photovoltaic devices.
Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.

碩士
明志科技大學
材料工程系碩士班
105
The strechable hybrid electrode (PEI/Ag/PEDOT:PSS, PAP electrode) was successfully fabricated. The effects of different fabricating conditions on the hybrid electrode performances and optimizing the conditions were investigated. Furthermore, in order to improve the transmittance of the device, the hybrid electrodes with SiO2 layer were also fabricated and examined. This hybrid electrode features a high gauge factor of >30, decent stretchability (100% of the original conductivity can be retained after 50-cycle stretching under a 20% strain without pre-strain treatment), high transmittance (>70%) across 400 to 800 nm, and a good sheet resistance (<50  square−1) benefitting from the reversible phase separation endowed by the nano-granular-like morphology formed in Ag. Owing to such discrete nanomorphology, the free volume within this Ag electrode is susceptible to the applied tensile strain and the ensuing change in conductivity enables the realization of an efficient strain sensor. Besides, a representative PTB7-th:PC71BM OPV using this electrode (featuring a wrinkled structure to reinforce the stretchability of the active layer) can exhibit a power conversion efficiency (PCE) of 6% along with high deformability, for which 75% of its original PCE is retained after 50-cycle stretching under a 20% strain. Meanwhile, a representative all-polymer OPV consisting of PTB7-Th:N2200 blend, in which the N2200 has a better mechanical stretchability than PC71BM, can maintains over 96% of its original PCE after 50-cycles stretching (under a 20% strain) in the absence of the wrinkled structure.

碩士
國立臺灣大學
光電工程學研究所
107
There are three parts in this thesis. First, we study on the small molecule solar cell. Second, we do the research about the triplet-triplet annihilation blue organic light-emitting diode. Last, we discuss light extraction through nanostructure in organic light-emitting diode. In chapter 3, we compared four electron donor-acceptor-acceptor (D-A-A) type electron donor materials, 7-(4-(di-p-tolylamino)phenyl)-6-fluorobenzo[c][1,2,5]thiadiazole-4,5-dicarbonitrile (DTCPiFBTCN), 7-(4-(di-p-tolylamino)phenyl)benzo[c][1,2,5]thiadiazole-4,5-dicarbonitrile (DTCPBTCN2), 7-(4-(di-p-tolylamino)phenyl)benzo[c][1,2,5]thiadiazole-4,5,6-tricarbonitrile (DTCPBTCN¬3) and 7-(5-(di-p-tolylamino)thiophen-2-yl)benzo[c][1,2,5]thiadiazole-4,5,6-tricarbonitrile (DTCTBTCN3¬)¬, with fullerene-based material C70 as the electron acceptor material in the active layer of small organic solar cells (SMOSCs) with bulk-heterojunction (BHJ) configuration. Among these D-A-A materials, DTCPBTCN2 as electron donor material with C70 as the electron acceptor material at the mixing ratio D:A=1:1.4 and 60 nm of active layer showed the highest power conversion efficiency of 5.41%, with open circuit voltage (Voc), short circuit current density (J¬sc) and fill factor (FF) of 0.89 V, 10.81 mA/cm2, and 56.26%, respectively. In chapter 4, we employed two new anthracene-core derivatives, 1-phenyl-2-(10-phenylanthracen-9-yl)-1H-benzo[d]imidazole (monoBizAn) and 4,4,5,5-tetramethyl-2-(10-(naphthalene-2-yl)-1,3,2-dioxaborolane (NpBorAn) as the blue triplet-triplet annihilation (TTA) emitters in the OLEDs with non-doped configuration and high doping concentrations in the host, 9,9''-(2-(1-Phenyl-1H-benzo[d]imidazol-2-yl)-1,3-phenylene)bis(9H-carbazole) (o-DiCbzBz). Device efficiency of TTA OLED with monoBizAn doped in o-DiCbzBz at 60% concentration showed the highest efficiency which achieved 5.74 cd/A, 4.71 lm/W and 5.56% in terms of current efficiency, power efficiency and EQE, respectively. In chapter 5, we studied the light extraction of blue phosphorescent organic light emitting diodes (PHOLEDs) with nanostructure (pitch = 833.33, 416.67, and 277.78 nm) between the substrate and the indium-zinc-oxide (IZO) anode. After optimizing plasma time、thickness of IZO and thickness of hole transport layer (HTL), blue PHOLED with nanostructure and macrolens can reach EQE value of 52.52% and enhancement ratio of 82.52%. Besides, we separate surface plasmon (SP) mode and waveguide mode to understand light extraction mechanism.

碩士
國立臺灣海洋大學
光電科學研究所
102
This thesis is based on a series of D-A-A structure. Thiazolidene, the core molecule, produces P-type small molecules which through vacuum thermal evaporation can be made into organic solar cells; and with small molecular electron acceptor materials C60 and C70 together can be made into a heterojunction device. In this project, DPPTPDC dye shown the greatest potential for solar cell use. By arranging different proportions of C60 or C70 monolayer heterojunction structures under AM1.5 solar illumination((100 mW/cm2), its efficiency can reach up to 1.55 %. Moreover, using it to produce a plane mixed bulk heterojunction of solar cell can further increase the power conversion efficiency(PCE) up to 2.63 %.

碩士
國立中正大學
物理所
98
Performance of solar cell (SC) was improved through the surface effect of gold nanoparticles (Nps) in this study. The fabrication of SC is similar, but the ways to embed the Nps are different. One is deposited gold Nps on ITO (indium tin oxide) electrode through ATPMS (3-aminopropyltrimethoxysilane) self-assemble monolayer (SAM), and another is separated 10 nm gold Nps from solution and mixed in the hole translation layer (PEDOT:PSS, poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate)) of SC. 　　In Method 1, transmission spectrum of 10 nm gold Nps deposited on glass showed strong absorption around wavelength 520 nm. PL (photoluminescence) intensity of the acitive layer (P3HT) was enhanced as the Si substrate was modified with 10 nm gold Nps. The ITO electrode was deposited by 10 nm gold Nps in different coverage, and 6 nm, 8 nm, and 10 nm gold Nps in identical density. There is no efficiency enhancement was observed in the measurement of air mass 1.5 solar simulator (AM-1.5) and incident monochromatic photon-to-current conversion efficiency (IPCE). Short circuit current showed the increasing series resistance and open circuit voltage indicated the decreasing shunt resistor in cells. AFM measurement indicated leakage path in gold-modified SC. 　　In Method 2, 10 nm gold Nps were separated by centrifuge and mixed into PEDOT:PSS. An enhancing efficiency from 2.16% to 3.18% was observed in SC with 3 mL, 10 nm gold Nps doped-PEDOT:PSS layer. Higher open circuit voltage in gold-doped SC indicated the shunt resistor was improved in reducing leakage current. Equivalent circuit of SC was demonstrated from Nyquist plot result. Lower series resistor made higher short circuit current in 3 mL doped-SC. Hall measurement result pointed higher carrier concentration after doping gold Nps in PEDOT:PSS, and improve the efficiency of SC. Band bending induced higher interface capacitance between active layer and gold-doped PEDOT:PSS layer. 　　This study supported two novel methods to improve the efficiency of SC. Enhancing efficiency of SC was achieved by decreasing series resistor because of gold Nps increased carrier concentration of PEDOT:PSS.

碩士
國立高雄應用科技大學
化學工程與材料工程系
100
Phenylenediamine (PDA) was mixed with aniline to prepare nanofiber polyaniline (PANI) which can enhance the solubility via in-situ polymerization in the presence of hydrochloric acid. Through the SEM and TEM micrographs, one can observe the morphology of nanocomposite and characterized with the photoelectron spectrometer, the energy level of materials can be obtained and the Ostwald Viscometer was used to measure the molecular weight, the measuring of hole effect show the mobility of materials, the power conversion efficiency was obtained by a solar simulator. Nanofiber of polyaniline owns similar absorption behavior with that of P3HT in UV-Vis spectra, both of which possess neutral, uncharged characteristics. The one-dimensional nano structure of polyaniline can increase the contact areas between donor and acceptor, which is useful to be coordinated with PCBM as a donor in the organic solar cell system. In the cell, we used ITO and Al as the anode and the cathode, respectively. In the case of bi-layer solar cell, the power conversion efficiency can be found to be 0.0224%。

碩士
國立臺灣大學
光電工程學研究所
104
In this study, performance improvement of Perovskite solar cells using two-step vapor-assisted solution process(VASP) has been achieved. Through experimental optimization, solar cell with optimal structure have been carried out and the mechanisms behind have been discussed in detail. Via scanning electron microscopy(SEM), the thickness profile and the morphological variation for Perovskite film obtained in different ways were investigated systematically. Next, the influence of post-annealing on device performance was verified by X-ray diffraction(XRD), suggesting that appropriate post treatment is crucial to the quality of active layer as well as the resulting performance. This is in addition to the study of passivation effect developed by PCBM([6,6]-phenyl-C61-butyric acid methyl ester) electron transport layer and also the Ca buffer incorporation, resulting in further improvement with decent fill factor for proposed devices. Based on these findings, the power conversion efficiency for Perovskite solar cells with an optimal device configuration has achieved over 11%. Further, a buffer material, HBC-6ImBr(Hexa-peri-hexabenzocoronene-6ImBr), was employed to enable hydrophilic properties for the hydrophobic graphene, allowing graphene bottom anode for conventional organic photovoltaics(OPV). With the aid of HBC-6ImBr, the aqueous PEDOT:PSS can be deposited onto graphene anode uniformly; hence the following fabrication process can be achieved to complete the solution-processed OPV. The morphological studies of graphene/HBC-6ImBr composite films were performed via atomic force microscope(AFM) to check the capabilities of surface modification. In the end of this thesis, a decent power conversion efficiency of 3.65% with a fill factor around 50% for P3HT:PCBM BHJ solar cell using graphene anode has been achieved by incorporating the anode modification of tri-layer HBC-6ImBr.

碩士
國立臺灣師範大學
化學系
99
A series of dyes (PT) with a carboxylic acid-conjugated spacer-donor-conjugated space-acceptor skeleton have been synthesized and used as the sensitizer for p-type dye-sensitized solar cells (DSSCs). Structural variation of the dye has significant influence on the photophysical and electrochemical properties of the dyes, and the incident photon-to-current conversion efficiencies of the DSSCs. DSSCs based on the sensitizers with two anchoring groups have more efficient hole injection and less dark current, and therefore higher Voc and Jscvalues those based on the dyes with only one anchoring group. Dark current and electrochemical impedance spectroscopy (ESI) were measured to rationalize the cell efficiencies. The efficiencies of the p-type devices based on PT series range from 0.043% to 0.081%. These values reach 49−92% of the standard device based on S(4-(bis(4-(5-(2,2-dicyanovinyl)thiophen-2-yl)phenyl)amino)benzoic acid) fabricated and measured under similar conditions.

碩士
國立中山大學
光電工程學系研究所
97
In this work, we studied the blends of metallic nanoparticle and polymers as a donor/acceptor bulk heterojunction active layer. The mobility of the free charge carriers in thin polymer films is lower, so we blended Pd nanoparticles (Pd NPs) into polymers to improve carrier mobility, and enhance the power conversion efficiency of the polymer solar cell. P3HT was used as a donor material because of its high stability and with high absorption in visible light. PCBM was used as a acceptor material because of its high stability and with high electron transportation. We blended nanoparticles that include different size (5nm and 20nm) and different metal (Pd and Pt) and blended into the P3HT:PCBM active layer, with the device configurations of ITO/PEDOT:PSS/P3HT:PCBM: Pt NPs/Al. Polymer solar cells measured was under AM 1.5G 100mW/cm2 illumination. When we blended Pd NPs and Pt NPs into the active layer, the power conversion efficiency increased from 2.43% to 2.78%. We will study dispersion and characteristic of different size nanoparticles in the active layer.

碩士
大葉大學
電機工程學系碩士班
92
We used p-type CuPc and n-type TPyP to grow up organic solar cells on ITO conductive glass by thermal evaporation. We have fabricated the sample No.S37 which is the best. The structure is ITO/TPyP(100 nm)/TPyP+CuPc(100 nm,2:1)/CuPc(100 nm)/Al. We also measured this sample and know the ISC=1.73 mA ,VOC=0.73V ,and evaluated fill factor(FF)=86.9% ,efficiency(η) =0.69%。Finally, we discussed the result what we got to find out the rule: the thick of n-type TPyP is thicker, or the ratio of TPyP in the mixture layer, we could get a better efficiency (η).

碩士
國立交通大學
光電工程研究所
102
In recent years, the emergence of hybrid organic and inorganic semiconductor solar cells attracts a lot of attention. Currently, GaAs hybrid solar cells which combine p-type PEDOT:PSS with n-type Gallium Arsenide(GaAs) can achieve a power conversion efficiency (PCE) of 7%. This thesis is divided into three parts. In the first part, we employ surface structures to increase the light absorption. By using a wet etching technique, we mix nitric acid with sulfuric acid and ammonia water mixed with hydrogen peroxide to etch GaAs surface. The reflectance was reduced to 13%, leading to a short-circuit current increase (Jsc) from 17.49 mA/cm2 to 23.3 mA/cm2 and an average PCE from 7.8% to 9.4%.By using a dry etching technique, the reflectance was reduced to 8.86%, leading to a Jsc increase from 16.17 mA/cm2 to 19.6 mA/cm2, and an average PCE from 7.11% to 7.42%. In the first part, we introduce organic materials TAPC and Green B into the GaAs interface. The intermediate layer functions as a recombination layer, which can reduce the chance of surface recombination and enhance the open-circuit voltage (Voc). The best device shows that the PCE can achieve 10% with Voc, Jsc and fill-factor equal to 0.645V, 25.15 mA/cm2, and 61.78%, respectively. Finally, GaAs has high absorption coefficients and a thickness of several micrometers is enough for light absorption. According to the detailed balance theory, we can further enhance the Voc by placing a good mirror on the back of a cell. In the third part, we use the wafer lift-off process to remove the substrate of GaAs hybrid solar cell and then metal bond to a silicon substrate with a gold back reflector. Our experiment result shows that the wafer-bonding cell has an average Voc of 0.7V with a net increase of 0.04V, which is qualitatively consistent with the simulation result.

碩士
國立臺灣海洋大學
光電科學研究所
94
Current research is focused on an inorganic/organic herterostructured solar cell comprising inorganic crystalline silicon and organic ZnPc (Zinc Phthalocyanine). We accidentally found that the efficiency of the solar cell reached 5.76% if the native oxide on silicon was not removed, while removing the native oxide resulted only in poor efficiency. Therefore, in this study, an insulating layer was intentionally applied on the surface of silicon to study its effect on the conversion efficiency and the related parameters of solar cells thus made. Taking the silicon oxide layer as the insulating layer, the optimized experimental conditions for fabrication such solar cell were studied. For a better performance, the silicon oxide layer should act both as a hole blocking layer and as a thin electron tunneling barrier. Eventually, an inorganic/organic heterostructere solar cell with 5.23% in efficiency and 13.22mA/cm2 in current density was successfully achieved.

碩士
國立臺灣大學
材料科學與工程學研究所
101
Electrichemical impedance analysis is a convenient technique to acquire the information about electric property of devices. After fitting with Bisquert model of equivalent circuit, we can acquire the carrier dynamic behavior such as mobility and lifetime of devices. And Mott-Schottky analysis can acquire the information about energy band bending. In this study, we use these techniques to analyze the built in voltage (Vbi) and carrier dynamic behaviors in organic photovoltaic. The structure of organic photovoltaic is: ITO/PEDOT:PSS/P3HT:PCBM/Al. There is a formation of a Schottky junction at active layer (P3HT:PCBM) and Al contact. In previous study, we spin coat different ratio TiOx on active layer and discover that the device efficiency and Voc would change depend on the ratio of TiOx. In this study, we can explain the phenomena by Mott Schottky analysis and EIS analysis. And the influences of carrier dynamic behavior also be shown. The second part, we present photoelectric light pulse technique method to compare with Mott-Schottky analysis. The photo u-v technique use space charge concept shows the similar result to measure Vbi with Mott-Schottky analysis which use the capacitance concept. We demo several device to show the result is compatible.

碩士
國立臺北科技大學
有機高分子研究所
100
According to the former research, when utilizes Pentacene as active layer to deposit on PEDOT: PSS for small molecule organic solar cell, the Pentacene occurs a phenomenon which dendritic-like(001) grain and fiber-like(110) grain are biphase coexistent. The related records also show that the phenomenon of biphase coexistence increases the possibility of scatter when charges were being transported and causes the mobility of charges to decrease. In the device performance, we would like to discuss the influence of Pentacene crystallinity and the device electrical property between the change of PFAS in the layers of PEDOT: PSS and Pentacene. Utilizing PFAS successfully lowers the surface energy on the layer of PEDOT: PSS. The analyses of AFM and XRD show that the treatment of PFAS causes fiber-like crystallite (110) of Pentacene disappearing and leaves crystalline grain (001) only. The device efficiency enhances from 0.94% to 1.38% after PFAS treatment, JSC enhances from 6.4 mA/cm2 to 8.19 mA/cm2, and VOC enhances from 0.29 V to 0.33 V. Then we try to improve the device performance by thermo annealing, the efficiency enhances to 1.73% in 180℃, VOC enhances from 0.33V to 0.45V. From XRD analysis, the Pentacene crystallite can transform from (001) to (001’) completely to form a similar single crystal when temperature more than 180℃.

碩士
南台科技大學
機械工程系
92
This research mainly focused on the fabrication of nano titanium dioxide（TiO2）thin film electrode and the infusing of electrolyte for nano-organic solar cell（NOSC）. Two kinds of organic dyes were used in NOSC to test their performance by measuring the voltage and current when exposed them under the sunlight. Furthermore, the fundamental principle, composed structure, the characteristics of organic dyes and the energy conversion efficiency of NOSC were introduced and analyzed. The feasibility and practicability about the NOSC in the future were also discussed. The fabrication method revealed in this study to produce the thin film electrode on conductive glass from nano TiO2 powders was called “Spray Vaporization Film-Growth（SVF）” method. The manufacturing procedure is to mix nano scale TiO2 powders with suitable amount of liquid, then the TiO2 mixture solution was injected from high pressure spray gun. The nebulized mixture was deposited on the heated conductive glass, and the TiO2 powders were soon sintered as thin film, when the liquid was vaporized. The method only need to heat conductive glass to 280℃ and take two minutes to form a sintered thin film electrode, compared with the other method, which need to heat conductive glass to 450℃ and take thirty minutes to form thin film. Therefore, the method used in this study may reduce the cost to fabricate TiO2 thin film electrode. On the infusing of electrolyte, this research used capillary force to fill electrolyte into the narrow space, which formed by two pieces of conductive glasses, each of them has thin film electrode on its side. The electrolyte was filled from the bottom edge to the top edge of the narrow space. However, the traditional method of infusing electrolyte needs to drill a hole on one glass surface as filling entrance. After the electrolyte was infused, the hole was sealed by UV glue. The new method does not need to drill any hole that seems to be more convenient and provide better appearance of solar cell. Besides, this research tested two kinds of organic dyes, which was extracted from plants. They were caffeine（C8H10N4O2）and chlorophyll（C55H70O6N4Mg）. The results show the chlorophyll provides better power performance for NOSC than the caffeine does.

碩士
國立中山大學
光電工程研究所
96
Polymers are with low carrier mobility. If polymer solar cells are to exhibit high power conversion efficiencies, their carrier mobilities must be improved. Metallic NPs are promising materials for use in polymer solar cells because of their high conductivities. In this work, we studied the carrier transport characteristic of metallic nanoparticle blending into polymers. We blended Pt nanoparticles (Pt NPs) and Pd nanoparticles (Pd NPs) into polymers to improve carrier mobility, and enhance the power conversion efficiency of the polymer solar cell. P3HT was used as a donor material because of its high stability and with high absorption in visible light. PCBM was used as a acceptor material because of its high stability and with high electron transportation. We blended modified Pt NPs and Pd NPs into the P3HT:PCBM active layer, with the device configurations of ITO/PEDOT:PSS/P3HT:PCBM: Pt NPs/Al and ITO/PEDOT:PSS/P3HT:PCBM:Pd NPs/Al, respectively polymer solar cells measured was under AM 1.5G 100mW/cm2 illumination. When we blended Pt NPs into the active layer, the open-circuit remained 0.64V, the short-circuit current increased from 6.67mA/cm2 to 9mA/cm2, the power conversion efficiency increased from 1.96% to 3.08%. When we blended Pd NPs into the active layer, the open-circuit remained 0.62V, the short-circuit current increased from 6.33mA/cm2 to 7.33mA/cm2, the power conversion efficiency increased from 1.7% to 2.48%. The enhanced efficiency originated from the increased carrier mobility of the active layer when the Pt NPs or Pd NPs were present.

碩士
中國文化大學
應用化學研究所
96
Two series (Cy and An) of dyes containing a cyanovinyl entity and an anthracene with alkoxy substituents at the 9 and 10 positions, respectively, as the spacer have been synthesized and characterized. Dye-sensitized solar cells (DSSCs) using these dyes as the sensitizers exhibited good efficiencies. The efficiencies of the devices based on Cy series range from 3.48-4.92%, and those based on An series range from 4.17-4.69%. These values which reach 45-70% and 59-67%, respectively, with respect to that of N719-based device fabricated under similar conditions. In general, a better DSSC performance was achieved in molecules with a shorter molecular structure and higher light harvesting. The cyanovinyl entity (Cy series), especially in the long molecular structure, where the cyanovinyl group is away from the electron donating amine by two or more aromatic groups, may behave as a charge trap. This argument was supported by theoretical computations. A positive correlation could be obtained from the theoretically calculated product of oscillator strengths and the charge shift at the cyanoacrylic acid group and the short-circuit currents in the DSSCs. The rigid anthracene segment in An series compounds. The anthracene with alkoxy substituents may cause thiophene moiety hamper the charge transfer and results in lower open-circuit voltages and short-circuit currents of the solar cells.

碩士
國立臺灣海洋大學
光電科學研究所
100
There are two topics in this thesis. First, we discussed small molecule organic solar cells (SMOSCs). Second, we used excited-state intramolecular proton transfer (ESIPT) molecules as dopant to fabricate OLEDs. In first part, we have demonstrated a novel D-A type molecule (LCC1), in which the donors (di-p-tolylamine) and the acceptor (dicyanovinylene) were bridged by a planar and rigid fluorene moiety. The vacuum-deposited planar-mixed heterojunction (PMHJ) photovoltaic devices employing LCC1 as the donor and C70 as acceptor achieved power conversion efficiencies (PCE) of 4.04 % and 5.31 % for the single- and tandem-cell photovoltaic devices, respectively, under simulated AM 1.5 illumination (100 mW cm‒2). In second part, we demonstrate two materials of fluorescent molecule by using ESIPT reaction, one is the white light generation can be achieved in a single ESIPT system to apply in OLED. Another fluorescent material is similar to the green fluorescent protein (Green fluorescent protein, GFP) chromophore p-HBDI structural isomers o-HBDI, while GFP is generally used in bio-medical. We successfully applied o-HBDI as the dopant in orange-red OLED. There are two topics in this thesis. First, we discussed small molecule organic solar cells (SMOSCs). Second, we used excited-state intramolecular proton transfer (ESIPT) molecules as dopant to fabricate OLEDs.

碩士
國立東華大學
材料科學與工程學系
101
This thesis is divided into two parts: Application of microlens array on organic photovoltaic devices and study on organic light-emitting device (OLED) polarized. In the first part of this thesis, we produced an organic photovoltaic device and reflection organic photovoltaic devices with different angles attached to different gap arranged microlens array illuminated observation of the short circuit current density (JSC) changes, and to identify the best efficiency microlens array. Studies in the oblique Illumination through the microlens array into the element of the multiple reflection effect. The reflection organic photovoltaic devices with micro-lens array in normal illumination increases the short circuit current density ( JSC ) by 11 %. The maximum the JSC to enhance 39% in the variable angle to 55 °. The second part of this thesis, we using organic light-emitting device (OLED) based on indium tin oxide (ITO)/ N,N-Bis (naphthalen-1-yl) -N,N-bis (phenyl) benzidine (NPB) (60 nm)/ 8-hydroxyquinoline aluminum (Alq3) (20~140 nm)/ lithium fluoride (LiF) (12 nm)/ aluminum (100 nm). We change the thickness of the element electron transporting layer (ETL) and emitting layer (ETL) (Alq3) is to explore different thickness photovoltaic characteristics. Use of polarizer separation of vertically polarized (VP) and parallel polarized (PP) to see such as spectral shift and the light intensity change.

碩士
國立中山大學
光電工程學系研究所
98
In this study, two kinds of homopolymers (PPDOT, and P3HT), and three different proportions of copolymers (PPDOT-co-P3HT=1:1, PPDOT-co-P3HT=3:1, and PPDOT-co-P3HT=1:3) have been synthesized successfully by Grignard metathesis. PDOT and 3HT, which are both of monomers, are electron-donating. Due to the fact that PDOT was caused larger than 3HT by pushing effect, it can change the conjugation length to be much longer, resulting in lower energy level of HOMO, and thus reduce energy gap of high molecular. These polymers possess optical bandgaps in the range of 1.908 to 1.922 eV. The desirable absorption attributes of these materials make them to be the excellent candidates for use in organic solar cells. In this study, the analysis and discussion of these polymers were measured by TGA, DSC, XRD, GPC, NMR, UV, PL, and AC-2 for thermal stability, crystallinity, structure and optical properties. From the XRD, materials of main chain ordered are well crystalline, which can increase the absorption of thiophene ring. By UV, we could find absorption region of infrared light increase that is beneficial to enhance ISC, but led to lower HOMO, and thus reduced VOC. However, the overall device power conversion efficiencies indicate that increasing ISC is much greater than decreasing VOC. Hence, power conversion efficiency increased. However, in PL, intensity of the emission is large, and it will cause components to quenching that lead to reduce its efficiency. We knew HOMO-LUMO energy level matching relations of polymer materials which were mixed with PCBM as the active layer of organic solar cells by UV-VIS and AC-2. From the instructions of device power conversion efficiency, because efficiency is not high, it causes the short circuit. The reason is (1) energy level can not match (2) the solubility of PPDOT is not very good, hence the film is not easy even. The way to improve is to identify a better solvent to increase its solubility.

碩士
國立臺北科技大學
有機高分子研究所
100
In this thesis, we synthesized two novel series of organic compound with the structure donor-conjugated chain-acceptor (D-π-A). The electron donor and acceptor groups are arylamine and cyano acrylic acid, respectively. We used these compound for dye-sensitized solar cell (DSSC). All of these compounds were characterized by UV/VIS spectrophotometer, fluorescence spectrophotometer and cyclic voltammetry. The photoconversion of these compounds were inspected using the AM 1.5 simulated solar light system.

碩士
國立臺北科技大學
化學工程研究所
97
This research is to improve the imperfection of Dye-sensitized solar cells (DSSC), which the liquid electrolyte easily leaked out form the component of cell, and raising the long-term stability of the application in DSSC. For the working electrode, first, add PEG into TiO2 powder and spin coating on working electrode, find out the best condition of it. Secondly, study the influence of using Poly(aniline-co-N-propanesulfonic acid aniline) in the TiO2 films on DSSC. For the electrolyte, first, using PEO as quis-electrolyte which can improve the imperfection, that the liquid electrolyte easily leaked out, and studying the influence of different ratios of PEO in the liquid electrolyte. If it has moisture, it would accelerate the effect of the phocatalyst of TiO2 in the fabrication process and then the dye can not develop to the expectative efficiency. To prevent this, I add water-repellent oligomer Polypropylene oxide into the qusi-electrolyte to modify its quality. Finally, I use a lot of apparatus to analyze its chemistry and physical properties which include NMR, TGA, SEM, XRD, White light Interferometers, Parallel-plate Rheometer and Cyclic Voltammetry. Finally, I imitate the system of the sun optic to test its efficiency. After testing the efficiency, TiO2 working electrode, 15um, that can obtain the best efficiency after two time calcined. When adding 15% PEO as qusi-electrolyte in the liquid electrolyte, adding 5% oligomer PPO in qusi-electrolyte can obtain the best efficiency. Oligomer PPO is modifying by synthesis can acquire PPO-COOH which has the best efficiency.

博士
國立臺灣大學
高分子科學與工程學研究所
103
This thesis investigates the function of various interfaces in solar cells. These interfaces are of great importance in controlling the key processes in solar cells such as the photocurrent generation, transport and extraction of photo-excited charge carriers. The surface-induced electronic distribution, band alignment and the molecular orientation in different solar cell structures are carefully examined by several techniques. In each study, the standard device fabrication and characterization provide the information to correlate the interface properties with the device performance. These results could be helpful for the understandings of the relationship between interface properties and the device performance of the solar cell. The interfacial engineering approaches presented here could also provide implications for the design of solar cell materials and devices. Firstly, the donor-acceptor interface is investigated by employing metal-phthalocyanine (M-Pc)/Silicon (Si) heterojunction as a model system. The lying-down configuration of PcPs (poly-Pc form) are observed, benefiting the charge transport and better contact in the hybrid based device. The strong metal-metal interaction between Pc molecules and substrate are believed to cause molecular orientation, which can facilitate the lying configuration. At the heterojunction interface also results in a relatively large open circuit voltage in a model solar cell device. Secondly, we investigate the hole transportation properties of an efficient anode interfacial layer of based on copper oxide materials. Significant band alignment and build-in voltage difference between buffer layer and active layer is observed due to the oxidation state difference of CuxO. The conduction band of evaporated- CuxO (e-CuxO) is very close to the highest occupied molecular orbital (HOMO) of donor material in polymer solar cell (eg. Poly(3-hexylthiophene-2,5-diyl), P3HT) facilitate the better charge transportation with minimal energy loss at anode/donor interface. Finally, the chemical-vapor-deposited (CVD) grown graphene modified Cu foil substrate induced orientation of pentacene so that the CVD graphene could be an effective interfacial layer to engineer the ordering of organic materials. The pentacene undergoes an obvious orientation change from a standing configuration on the PEDOT electrode to a less standing configuration on the ITO electrode and Cu foil. The surface free energy also provides a strategic way to control the orientation of organic molecules. Better transporting mobility of the lying-down pentacene on graphene modified electrode facilitate the effective charge transporting in single layer device. This is also affects active in optoelectronic devices.