Journal articles: 'Excitonic process'

1

Seiler, Hélène, Marcin Krynski, Daniela Zahn, Sebastian Hammer, Yoav William Windsor, Thomas Vasileiadis, Jens Pflaum, Ralph Ernstorfer, Mariana Rossi, and Heinrich Schwoerer. "Nuclear dynamics of singlet exciton fission in pentacene single crystals." Science Advances 7, no. 26 (June 2021): eabg0869. http://dx.doi.org/10.1126/sciadv.abg0869.

Full text

Abstract:

Singlet exciton fission (SEF) is a key process for developing efficient optoelectronic devices. An aspect rarely probed directly, yet with tremendous impact on SEF properties, is the nuclear structure and dynamics involved in this process. Here, we directly observe the nuclear dynamics accompanying the SEF process in single crystal pentacene using femtosecond electron diffraction. The data reveal coherent atomic motions at 1 THz, incoherent motions, and an anisotropic lattice distortion representing the polaronic character of the triplet excitons. Combining molecular dynamics simulations, time-dependent density-functional theory, and experimental structure factor analysis, the coherent motions are identified as collective sliding motions of the pentacene molecules along their long axis. Such motions modify the excitonic coupling between adjacent molecules. Our findings reveal that long-range motions play a decisive part in the electronic decoupling of the electronically correlated triplet pairs and shed light on why SEF occurs on ultrafast time scales.

APA, Harvard, Vancouver, ISO, and other styles

2

Sánchez, Fernando, Vicenta Sánchez, and Chumin Wang. "Coarse-Grained Quantum Theory of Organic Photovoltaic Devices." Nanomaterials 11, no. 2 (February 16, 2021): 495. http://dx.doi.org/10.3390/nano11020495.

Full text

Abstract:

Understanding the exciton dissociation process in organic solar cells is a fundamental issue for the design of high-performance photovoltaic devices. In this article, a parameterized quantum theory based on a coarse-grained tight-binding model plus non-local electron-hole interactions is presented, while the diffusion and recombination of excitons are studied in a square lattice of excitonic states, where a real-space renormalization method on effective chains has been used. The Hamiltonian parameters are determined by fitting the measured quantum efficiency spectra and the theoretical short-circuit currents without adjustable parameters show a good agreement with the experimental ones obtained from several polymer:fullerene and polymer:polymer heterojunctions. Moreover, the present study reveals the degree of polymerization and the true driving force at donor-acceptor interface in each analyzed organic photovoltaic device.

APA, Harvard, Vancouver, ISO, and other styles

3

VIELHAUER, S., M. KIRM, V. KISAND, E. NEGODIN, E. SOMBROWSKI, B. STEEG, and G. ZIMMERER. "EXCITONIC SIDE BANDS OF INNER-SHELL EXCITATIONS IN RARE GAS SOLIDS." Surface Review and Letters 09, no. 02 (April 2002): 1333–38. http://dx.doi.org/10.1142/s0218625x02003767.

Full text

Abstract:

Valence-exciton luminescence under inner-shell excitation of the rare gas solids Xe, Kr, and Ar has been measured using time-resolved photoluminescence. Two different processes for exciton creation can be distinguished: creation of "prompt" excitons immediately after excitation (within the experimental time resolution), and creation of "delayed" excitons through electron–hole recombination. The decay structure of the exciton emission in the range of inner-shell excitation is characterized by the coexistence of the two processes. Time-resolved excitation spectra near the 2p edge in Ar, the 3d edge in Kr, and the 4d edge in Xe are discussed. The process of prompt exciton creation is strongly enhanced above an excitation threshold at the energy position of the ionization limit of the core state plus the energy of the valence free exciton.

APA, Harvard, Vancouver, ISO, and other styles

4

TAKEDA, JUN, SUSUMU KURITA, YEFAN CHEN, and TAKAFUMI YAO. "ULTRAFAST CARRIER DYNAMICS IN ZnO EPITAXIAL THIN FILMS STUDIED BY OPTICAL KERR GATE LUMINESCENCE SPECTROSCOPY." International Journal of Modern Physics B 15, no. 28n30 (December 10, 2001): 3669–72. http://dx.doi.org/10.1142/s0217979201008391.

Full text

Abstract:

Time-resolved luminescence spectra of ZnO epitaxial thin films have been measured by the optical Kerr gate luminescence spectroscopy under resonant excitation of the excitonic state. At moderate excitation density, a luminescence band (P band) which is attributed to an exciton-exciton collision process was observed. With increasing the excitation density, the P band disappears while a new luminescence band (EHP band) due to radiative recombination of electrons with holes in an electron-hole plasma appears. The EHP band has a rise time of ~1 ps, and shifts to lower energy with time and then finally shifts to higher energy. The rise time of the EHP band shows a transition time from a high density excitonic state to an unbound electron-hole system due to the screening of Coulomb interaction. The red shift of the EHP band comes from the reduced band-gap effect, while the blue shift to the EHP band is mainly attributed to recovery of the renormalized band-gap, which occurs with decreasing the carrier density due to the radiative recombination of electrons with holes.

APA, Harvard, Vancouver, ISO, and other styles

5

Wilhelm, Philipp, Jakob Schedlbauer, Florian Hinderer, Daniel Hennen, Sigurd Höger, Jan Vogelsang, and John M. Lupton. "Molecular excitonic seesaws." Proceedings of the National Academy of Sciences 115, no. 16 (April 2, 2018): E3626—E3634. http://dx.doi.org/10.1073/pnas.1722229115.

Full text

Abstract:

The breaking of molecular symmetry through photoexcitation is a ubiquitous but rather elusive process, which, for example, controls the microscopic efficiency of light harvesting in molecular aggregates. A molecular excitation within a π-conjugated segment will self-localize due to strong coupling to molecular vibrations, locally changing bond alternation in a process which is fundamentally nondeterministic. Probing such symmetry breaking usually relies on polarization-resolved fluorescence, which is most powerful on the level of single molecules. Here, we explore symmetry breaking by designing a large, asymmetric acceptor–donor–acceptor (A1-D-A2) complex 10 nm in length, where excitation energy can flow from the donor, a π-conjugated oligomer, to either one of the two boron-dipyrromethene (bodipy) dye acceptors of different color. Fluorescence correlation spectroscopy (FCS) reveals a nondeterministic switching between the energy-transfer pathways from the oligomer to the two acceptor groups on the submillisecond timescale. We conclude that excitation energy transfer, and light harvesting in general, are fundamentally nondeterministic processes, which can be strongly perturbed by external stimuli. A simple demonstration of the relation between exciton localization within the extended π-system and energy transfer to the endcap is given by considering the selectivity of endcap emission through the polarization of the excitation light in triads with bent oligomer backbones. Bending leads to increased localization so that the molecule acquires bichromophoric characteristics in terms of its fluorescence photon statistics.

APA, Harvard, Vancouver, ISO, and other styles

6

El Kabbash, Mohamed, Alireza Rahimi Rashed, Kandammathe Valiyaveedu Sreekanth, Antonio De Luca, Melissa Infusino, and Giuseppe Strangi. "Plasmon-Exciton Resonant Energy Transfer: Across Scales Hybrid Systems." Journal of Nanomaterials 2016 (2016): 1–21. http://dx.doi.org/10.1155/2016/4819040.

Full text

Abstract:

The presence of an excitonic element in close proximity of a plasmonic nanostructure, under certain conditions, may lead to a nonradiative resonant energy transfer known as Exciton Plasmon Resonant Energy Transfer (EPRET) process. The exciton-plasmon coupling and dynamics have been intensely studied in the last decade; still many relevant aspects need more in-depth studies. Understanding such phenomenon is not only important from fundamental viewpoint, but also essential to unlock many promising applications. In this review we investigate the plasmon-exciton resonant energy transfer in different hybrid systems at the nano- and mesoscales, in order to gain further understanding of such processes across scales and pave the way towards active plasmonic devices.

APA, Harvard, Vancouver, ISO, and other styles

7

Guo, Bolin, Chao Luo, Cheng Yan, Bai Sun, Wen Li, and Weiqing Yang. "Understanding Excitonic Behavior in Light Absorption and Recombination Process." Journal of Physical Chemistry C 124, no. 47 (November 13, 2020): 26076–82. http://dx.doi.org/10.1021/acs.jpcc.0c09334.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

Ueno, Yoshihiro, Shiho Kishino, Hideyuki Kunugita, Kazuhiro Ema, Masahiro Rikukawa, Yuko Tabuchi, and Naoya Ogata. "Ultrafast Excitonic Nonlinearity in Regioregular Head-to-Tail Coupled Poly(3-Hexylthiophene)." Journal of Nonlinear Optical Physics & Materials 07, no. 01 (March 1998): 161–66. http://dx.doi.org/10.1142/s0218863598000132.

Full text

Abstract:

Third-order optical nonlinearity of regioregular head-to-tail coupled poly(3-hexylthiophene)(HT-PHT) was measured using degenerate four wave mixing (DFWM), and the dispersion spectrum of |χ(3)| around the exciton absorption peak was obtained. In addition, the relaxation process of the excitons was measured using the transient grating method. The resultant decay time was less than 2 ps and consisted of two components.

APA, Harvard, Vancouver, ISO, and other styles

9

Михайлов, Т. Н., Е. А. Европейцев, К. Г. Беляев, A. A. Торопов, A. В. Родина, A. A. Головатенко, С. В. Иванов, Г. Позина, and T. В. Шубина. "Ферстеровский резонансный перенос энергии с участием светлых и темных экситонов в массивах эпитаксиальных квантовых точек CdSe/ZnSe." Физика твердого тела 60, no. 8 (2018): 1575. http://dx.doi.org/10.21883/ftt.2018.08.46246.03gr.

Full text

Abstract:

AbstractUsing time-resolved photoluminescence (PL) spectroscopy, we establish the presence of the Förster energy transfer mechanism between two arrays of epitaxial CdSe/ZnSe quantum dots (QDs) of different sizes. The mechanism operates through dipole–dipole interaction between ground excitonic states of the smaller QDs and excited states of the larger QDs. The dependence of energy transfer efficiency on the width of barrier separating the QD insets is shown to be in line with the Förster mechanism. The temperature dependence of the PL decay times and PL intensity suggests the involvement of dark excitons in the energy transfer process.

APA, Harvard, Vancouver, ISO, and other styles

10

Thomas, P., M. M�ller, R. Eichmann, T. Meier, T. Stroucken, and A. Knorr. "Microscopic Foundation of the F�rster Excitonic Energy Transfer Process." physica status solidi (b) 230, no. 1 (March 2002): 25–29. http://dx.doi.org/10.1002/1521-3951(200203)230:1<25::aid-pssb25>3.0.co;2-8.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Do, Thanh Nhut, Adriana Huerta-Viga, Cheng Zhang, Parveen Akhtar, Pawei J. Nowakowski, Muhammad Faisal bin Khyasudeen, Hoang Long Nguyen, Petar H. Lambrev, and Howe-Siang Tan. "Excitation energy transfer and equilibration process in LHCII studied by multidimensional electronic spectroscopy." EPJ Web of Conferences 205 (2019): 09038. http://dx.doi.org/10.1051/epjconf/201920509038.

Full text

Abstract:

Light-harvesting complex II (LHCII) – the light-harvesting antenna of Photosystem II – is a naturally abundant system that plays an important role in photosynthesis. In this study, we present a phenomenological analysis of the excitonic energy transfer in LHCII using ultrafast two-dimensional electronic spectroscopy, that we find compares well with previous theoretical and experimental results.

APA, Harvard, Vancouver, ISO, and other styles

12

DeSilva, L. Ajith, Sarahn Nazaret, A. G. U. Perera, and T. M. W. J. Bandara. "Optical Properties of Alq3/TiO2 BDR Structure Processed by Spin Coating Technique." MRS Advances 4, no. 11-12 (2019): 661–66. http://dx.doi.org/10.1557/adv.2019.22.

Full text

Abstract:

ABSTRACTOne-dimensional hybrid Distributed Bragg Reflector (DBR) is constructed using Tris (8-hydroxy) quinoline aluminum (Alq3) molecules and Titanium dioxide (TiO2) nanoparticles via spin coating process. Light emission from thin films of low molecular weight organic semiconductor of Alq3 is dominated by excitons. This material has been widely used as a superior emitter for organic light emitting diodes. Titanium dioxide (TiO2) is an inorganic semiconductor with a high band gap. Photoluminescence (PL) of thin films of Alq3 showed a broad PL peak at 530 nm. In DBR structures, PL quenching is observed but there is no shift in the PL peak of the Alq3. The PL quenching is tentatively attributed to energy transfer via sensitization to wide band gap TiO2 layers. A simple excitonic model is suggested to explain the observation. Fabrication process and optical properties of the structure are presented.

APA, Harvard, Vancouver, ISO, and other styles

13

Ezaki, Hiromi, G. S. Agarwal, and Eiichi Hanamura. "Photon number squeezing enhanced by two-photon process in excitonic systems." Optics Communications 138, no. 1-3 (May 1997): 65–70. http://dx.doi.org/10.1016/s0030-4018(97)00084-9.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Hernández‐Cabrera, A., P. Aceituno, and H. Cruz. "Stark effect and excitonic tunneling escape process in semiconductor quantum wells." Journal of Applied Physics 76, no. 9 (November 1994): 4983–88. http://dx.doi.org/10.1063/1.357208.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Okamoto, Akimitsu. "Excitonic interaction: another photophysical process for fluorescence-controlled nucleic acid sensing." Chemical Record 10, no. 3 (May 27, 2010): 188–96. http://dx.doi.org/10.1002/tcr.201000003.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

Gaur, Poonam, B. P. Malik, Dimple Sharma, and Arun Gaur. "Preparation of Zinc-Doped CdSe Nanoparticles and Determination of Their Nonlinear Optical Properties using Z-Scan Technique in Thick Media." Nano 10, no. 02 (February 2015): 1550018. http://dx.doi.org/10.1142/s1793292015500186.

Full text

Abstract:

The present work aims at the synthesis of Zinc-doped CdSe ( Zn : CdSe ) nanoparticles with average size near the Bohr radius by wet chemical method. The synthesized nanoparticles have been characterized by X-ray diffraction (XRD), UV-Vis spectrometer is used for the determination of bandgap and crystallite size is estimated using Debye–Scherrer formula and Brus equation. The nonlinear optical property that is excitonic nonlinear absorption and the wavelength dependence of nonlinear absorption has also been measured near the excitonic transitions involving the lowest electron state (1S) and one of the hole states 1S3/2(h). We observe the saturable absorption (SA), which can be described by a third-order and a fifth-order nonlinear process for Zn : CdSe nanocrystals. The irradiance and wavelength dependence of the excitonic nonlinearity are explained by two-level model. The calculations have been performed with the help of Z-scan experimental setup using Handy Compact Q-switched pulsed Nd:YAG laser (HYL-101 Quanta System).

APA, Harvard, Vancouver, ISO, and other styles

17

Ko, Brian A., Alexei V. Sokolov, Marlan O. Scully, Zhenrong Zhang, and Ho Wai Howard Lee. "Enhanced four-wave mixing process near the excitonic resonances of bulk MoS2." Photonics Research 7, no. 3 (February 5, 2019): 251. http://dx.doi.org/10.1364/prj.7.000251.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Otsuka, Keigo, Akihiro Ishii, and Yuichiro K. Kato. "Super-resolution fluorescence imaging of carbon nanotubes using a nonlinear excitonic process." Optics Express 27, no. 13 (June 10, 2019): 17463. http://dx.doi.org/10.1364/oe.27.017463.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

Jeong, Hongsik, In-Ja Lee, Jung-Chul Seo, Minyung Lee, Dongho Kim, Seong-Ju Park, Seung-Han Park, and Ung Kim. "Temperature and size dependent excitonic relaxation process in GaAs/AlGaAs quantum wells." Solid State Communications 85, no. 2 (January 1993): 111–14. http://dx.doi.org/10.1016/0038-1098(93)90357-s.

Full text

APA, Harvard, Vancouver, ISO, and other styles

20

Aghoutane, Noreddine, Laura Pérez, Anton Tiutiunnyk, David Laroze, Sotirios Baskoutas, Francis Dujardin, Abdelouahad Fatimy, Mohamed El-Yadri, and El Feddi. "Adjustment of Terahertz Properties Assigned to the First Lowest Transition of (D+,X) Excitonic Complex in a Single Spherical Quantum Dot Using Temperature and Pressure." Applied Sciences 11, no. 13 (June 27, 2021): 5969. http://dx.doi.org/10.3390/app11135969.

Full text

Abstract:

This theoretical study is devoted to the effects of pressure and temperature on the optoelectronic properties assigned to the first lowest transition of the (D+,X) excitonic complex (exciton-ionized donor) inside a single AlAs/GaAs/AlAs spherical quantum dot. Calculations are performed within the effective mass approximation theory using the variational method. Optical absorption and refractive index as function of the degree of confinement, pressure, and temperature are investigated. Numerical calculation shows that the pressure favors the electron-hole and electron-ionized donor attractions which leads to an enhancement of the binding energy, while an increasing of the temperature tends to reduce it. Our investigations show also that the resonant peaks of the absorption coefficient and the refractive index are located in the terahertz region and they undergo a shift to higher (lower) therahertz frequencies when the pressure (temperature) increases. The opposite effects caused by temperature and pressure have great practical importance because they offer an alternative approach for the adjustment and the control of the optical frequencies resulting from the transition between the fundamental and the first excited state of exciton bound to an ionized dopant. The comparison of the optical properties of exciton , impurity and (D+,X) facilitates the experimental identification of these transitions which are often close. Our investigation shows that the optical responses of (D+,X) are located between the exciton (high energy region) and donor impurity (low energy region) peaks. The whole of these conclusions may lead to the novel light detector or source of terahertz range.

APA, Harvard, Vancouver, ISO, and other styles

21

Huang, Tongyun, Peng Han, Xinke Wang, Shengfei Feng, Wenfeng Sun, Jiasheng Ye, and Yan Zhang. "Phonon induced pure dephasing process of excitonic state in colloidal semiconductor quantum dots." Superlattices and Microstructures 92 (April 2016): 52–59. http://dx.doi.org/10.1016/j.spmi.2016.01.042.

Full text

APA, Harvard, Vancouver, ISO, and other styles

22

An, Nguyen Ba, and P. Mandel. "An analytic study of the switching process in excitonic optical bistability in semiconductors." Journal of Physics: Condensed Matter 5, no. 26 (June 28, 1993): 4451–66. http://dx.doi.org/10.1088/0953-8984/5/26/016.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

Li, Chun Ping, Yu Zhen Lv, Lin Guo, X. B. Xu, X. C. Ai, and J. P. Zhang. "Synthesis and Optical Characterizations of ZnO Nanorods." Solid State Phenomena 121-123 (March 2007): 805–8. http://dx.doi.org/10.4028/www.scientific.net/ssp.121-123.805.

Full text

Abstract:

Monodisperse wurtzite ZnO nanorods with the length of 4 μm and the diameter of 200 nm were prepared via a simple solution chemical process. The crystal phases and the microstructure of nanorods were studied via XRD, SEM, respectively. The properties of the excitonic luminescence are investigated by using the laser power dependence and temperature dependence of photoluminescence (PL) spectra.

APA, Harvard, Vancouver, ISO, and other styles

24

Švrček, Vladimir. "Excitation energy transfer in conjugated polymer/silicon nanocrystal-based bulk heterojunctions." Pure and Applied Chemistry 82, no. 11 (August 6, 2010): 2121–35. http://dx.doi.org/10.1351/pac-con-09-12-01.

Full text

Abstract:

An excitation energy transfer in a bulk heterojunction based on freestanding silicon nanocrystals (Si-NCs) and conjugated polymers {poly(3-hexylthiophene) (P3HT), poly[2-methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV)} is demonstrated. The electrochemical etching process is employed for fabrication of freestanding and polymer soluble Si-NCs. Formation of a bulk heterojunction is confirmed by a difference in a work function of both polymers and an ionization potential of the NCs. An annealing step significantly influences the polymer chain conformation and electronic interaction between the polymer and the NC, which improves the exciton energy migration. The presence of the Si-NCs in polymers suppresses the relative intensity of vibronic peaks, resulting in a red-shift of the blend photoluminescence (PL) spectra. This phenomenon is attributed to a temperature-dependent migration process of singlet exciton and Dexter excitation energy transfer from the polymer to the NC. Compared to MEH-PPV polymer, a lamella-type stacking structure of the P3HT and an abridged PL spectra overlap with NCs decreases an excitation energy transfer rate. At the same time, an improvement in photocurrent generation is recorded when Si-NCs are embedded in P3HT polymer. After Dexter-like excitonic energy transfer, the PL emission of both blends is controlled through a quantum confinement effect and electron-hole recombination in Si-NCs.

APA, Harvard, Vancouver, ISO, and other styles

25

Matsuzaki, Ryosuke, and Takashi Uchino. "Effect of size and shape on the excitonic stimulated emission process in ZnO microstructures." Journal of Applied Physics 124, no. 6 (August 14, 2018): 063103. http://dx.doi.org/10.1063/1.5039790.

Full text

APA, Harvard, Vancouver, ISO, and other styles

26

Hirayama, T., T. Nagai, M. Abo, I. Arakawa, K. Mitsuke, and M. Sakurai. "Excitonic energy transfer process in NeKr alloy studied by photon stimulated desorption of metastable atoms." Journal of Electron Spectroscopy and Related Phenomena 80 (May 1996): 101–4. http://dx.doi.org/10.1016/0368-2048(96)02932-5.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

Резник, И. А., А. С. Златов, П. О. Ильин, Р. A. Заколдаев, С. A. Мошкалёв, and A. O. Орлова. "Люминесцентные и фотоэлектрические свойства гибридных структур на основе многослойного графена и 0D и 2D полупроводниковых квантовых нанокристаллов." Журнал технической физики 128, no. 6 (2020): 726. http://dx.doi.org/10.21883/os.2020.06.49403.66-20.

Full text

Abstract:

Establishing the laws of the mechanisms underlying the interaction of nanostructured materials is one of the most important tasks on the way to creating a new generation of efficient photovoltaic devices. In this paper, we study the luminescent and photoelectric properties of hybrid structures formed on the basis of multilayer graphene nanobelts and semiconductor quantum nanocrystals: 0D-: core-shell CdSe / ZnS quantum dots, and 2D-: CdSe nanoplatelets. It was shown that the multiexponential decay of the excitonic luminescence of CdSe nanoplates at room temperature originates from the delayed luminescence due to the presence of trap states on the surface of the nanoplates. It has been established that in the dry layers of nanoplatelets on a dielectric substrate and in the composition of hybrid structures with graphene nanoribbons, the efficiency of delayed excitonic luminescence of nanoplates increases. It has been demonstrated that the rate of increase in photoconductivity in hybrid structures based on CdSe nanoplatelets is an order of magnitude higher than the rate of this process in similar structures based on CdSe / ZnS quantum dots, which indicates the formation of an effective energy / charge transfer channel from nanoplatelets to graphene nanoribbons.

APA, Harvard, Vancouver, ISO, and other styles

28

Guimarães, José Diogo, Carlos Tavares, Luís Soares Barbosa, and Mikhail I. Vasilevskiy. "Simulation of Nonradiative Energy Transfer in Photosynthetic Systems Using a Quantum Computer." Complexity 2020 (September 16, 2020): 1–12. http://dx.doi.org/10.1155/2020/3510676.

Full text

Abstract:

Photosynthesis is an important and complex physical process in nature, whose comprehensive understanding would have many relevant industrial applications, for instance, in the field of energy production. In this paper, we propose a quantum algorithm for the simulation of the excitonic transport of energy, occurring in the first stage of the process of photosynthesis. The algorithm takes in account the quantum and environmental effects (pure dephasing), influencing the quantum transport. We performed quantum simulations of such phenomena, for a proof of concept scenario, in an actual quantum computer, IBM Q, of 5 qubits. We validate the results with the Haken-Ströbl model and discuss the influence of environmental parameters on the efficiency of the energy transport.

APA, Harvard, Vancouver, ISO, and other styles

29

Kheng, K., K. Saminadayar, and N. Magnea. "Inter-Landau level shakeup process compared in excitonic absorption and recombination spectra of modulation-doped quantum wells." Physica E: Low-dimensional Systems and Nanostructures 2, no. 1-4 (July 1998): 256–60. http://dx.doi.org/10.1016/s1386-9477(98)00054-x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Gayou, V. L., B. Salazar Hernández, R. Delgado Macuil, G. Zavala, P. Santiago, and A. I. Oliva. "Structural Studies of ZnS Nanoparticles by High Resolution Transmission Electron Microscopy." Journal of Nano Research 9 (February 2010): 125–32. http://dx.doi.org/10.4028/www.scientific.net/jnanor.9.125.

Full text

Abstract:

Zinc sulfide (ZnS), a representative of wide band gap semiconductor nanocrystals, has an excitonic Bohr radius (aBZnS ) of 2.5 nm. It makes ZnS nanoparticles (ZnS NP) having such size very interesting as small biomolecular probes for fluorescence and laser scanning microscopy. To date, ZnS NP of diameters larger than aBZnS has been subject of extensive experimental and theoretical studies. However many questions remain open concerning the synthesis of undoped and uncapped ZnS NP of diameters less than 2.5 nm. To further probe into the physical properties of undoped and uncapped ZnS NP, in this work we report on studies of uncapped ZnS nanoparticles synthesized by a wet chemical process at room temperature. Three colloidal suspensions (named A, B and C, respectively) were obtained from 9:1, 1:1 and 1:9 volume mixtures of 1mM ZnSO4 and 0.85mM Na2S aqueous solutions. Qualitative differences in UV-Vis absorption spectra are discussed in the context of Z-contrast scanning transmission electron microscopy (Z-contrast), low and high resolution transmission electron microscopy (TEM) results. Distribution of particle size is dependent on different volumes of source solutions. For the intermediate mixture, it has been found that about 78% of ZnS nanoparticles have a diameter smaller than the excitonic Bohr Radius of 2.5 nm. HRTEM studies have revealed that nanoparticles grow preferentially with hexagonal structure.

APA, Harvard, Vancouver, ISO, and other styles

31

Yuen-Zhou, Joel, and Alán Aspuru-Guzik. "Quantum process tomography of excitonic dimers from two-dimensional electronic spectroscopy. I. General theory and application to homodimers." Journal of Chemical Physics 134, no. 13 (April 7, 2011): 134505. http://dx.doi.org/10.1063/1.3569694.

Full text

APA, Harvard, Vancouver, ISO, and other styles

32

Debus, J., D. Kudlacik, V. F. Sapega, T. S. Shamirzaev, D. R. Yakovlev, D. Reuter, A. D. Wieck, A. Waag, and M. Bayer. "Basic requirements of spin-flip Raman scattering on excitonic resonances and its modulation through additional high-energy illumination in semiconductor heterostructures." Физика твердого тела 60, no. 8 (2018): 1583. http://dx.doi.org/10.21883/ftt.2018.08.46250.14gr.

Full text

Abstract:

AbstractWe describe the major requirements to experimentally perform and observe resonant spin-flip Raman scattering on excitonic resonances in low-dimensional semiconductors. We characterize in detail the properties of this resonant light scattering technique and evaluate the criteria, which must be fulfilled by the experimental setup and the semiconductor sample studied to be able to observe a spin-flip scattering process. We also demonstrate the influence of additional unpolarized laser illumination with energies, which exceed considerably the band gap energy of the semiconductor nanostructure under study, on the resonantly excited electron spin-flip scattering in InAs-based quantum dot ensembles as well as on the paramagnetic Mn-ion spin-flip in (Zn,Mn)Se/(Zn,Be)Se quantum wells.

APA, Harvard, Vancouver, ISO, and other styles

33

Jonnard, P., F. Vergand, C. Bonnelle, M. Leroux, and J. Massies. "Al 3p valence and excitonic states in GaSb/Al0.3Ga0.7Sb and GaAs/Al0.3Ga0.7As heterostructures as a function of growth process." Physical Review B 55, no. 23 (June 15, 1997): 15727–34. http://dx.doi.org/10.1103/physrevb.55.15727.

Full text

APA, Harvard, Vancouver, ISO, and other styles

34

Spitz, C., and S. Daehne. "Low temperature exciton-exciton annihilation in amphi-PIPE J-aggregates." International Journal of Photoenergy 2006 (2006): 1–7. http://dx.doi.org/10.1155/ijp/2006/84950.

Full text

Abstract:

The mobility of optically excited excitons on J-aggregates can be demonstrated by the phenomena of exciton-exciton annihilation. In this intensity-dependent process the collision of two excitons results in their annihilation and hence in a shortening of the mean excitation lifetime. By measuring the intensity-dependent fluorescent lifetime in contrast to the predicted immobilization of the excitons at low temperature we could prove the excellent mobility of the excitons at a temperature (4K), which is far below their expected freezing point.

APA, Harvard, Vancouver, ISO, and other styles

35

XUE, S. W., X. T. ZU, X. XIANG, M. Y. CHEN, and W. G. ZHENG. "EFFECTS OF Ge DOPING THROUGH ION IMPLANTATION ON THE STRUCTURAL AND OPTICAL PROPERTIES OF ZnO THIN FILMS PREPARED BY SOL-GEL TECHNIQUE." International Journal of Modern Physics B 21, no. 31 (December 20, 2007): 5257–63. http://dx.doi.org/10.1142/s0217979207038290.

Full text

Abstract:

ZnO thin films were first prepared by the sol–gel process, and then Ge ions were implanted into the ZnO films. The effects of ion implantation on the structural and optical properties of the ZnO films were investigated by X-ray diffraction, photoluminescence (PL), and optical transmittance measurements. Measurement results showed that the intensity of the (002) diffraction peak was decreased and the full width at half maximum was narrowed. PL emission was greatly extinguished after Ge ion implantation. Both the near band edge (NBE) excitonic UV emission at 391 nm and the defect related deep level emission centered at 470 nm in the visible region were decreased after Ge ion implantation. NBE peak and the absorption edge were observed to have a blueshift toward higher energy.

APA, Harvard, Vancouver, ISO, and other styles

36

Mahendra, Robert, Mariesta Arianti, Dyah Sawitri, and Doty Dewi Risanti. "Synthesis of Various ZnO Nanotree Morphologies through PEG-Assisted Co-Precipitation Method." Advanced Materials Research 1112 (July 2015): 66–70. http://dx.doi.org/10.4028/www.scientific.net/amr.1112.66.

Full text

Abstract:

ZnO, with direct wide band gap of 3.37 eV and high excitonic binding energy of 60 meV has been attracting much attention due to its wide range of applications, for transparent electronics, solar cells, and other optoelectronics device. We present a simple, single step process to produce ZnO nanotrees using co-precipitation method. As a precursor, zinc nitrate dehydrate was stabilized by hexamethylene tetraamine (HMTA) and 3-9 mM polyethylene glycol (PEG) was added at 180°C for 3-6 hours followed by residual polymer removal. Scanning Electron Microscopy revealed the typical rod-like branched nanostructures were achieved. For longer annealing time the PEG-assisted growth process indeed exhibited a distinctive c-direction inhibition responsible for the lateral growth and subsequent branching of ZnO, in which the branch growth in sample with PEG amount of 0.05 g is the slowest. Some amounts of PEG up to 0.03 g are sensitive to affect several parameters, such as, lattice stress, unit cell volume, density of film and dislocation density.

APA, Harvard, Vancouver, ISO, and other styles

37

Ma, Fei, Long-Jiang Yu, Ruud Hendrikx, Zheng-Yu Wang-Otomo, and Rienk van Grondelle. "Excitonic and Vibrational Coherence in the Excitation Relaxation Process of Two LH1 Complexes as Revealed by Two-Dimensional Electronic Spectroscopy." Journal of Physical Chemistry Letters 8, no. 12 (June 7, 2017): 2751–56. http://dx.doi.org/10.1021/acs.jpclett.7b00824.

Full text

APA, Harvard, Vancouver, ISO, and other styles

38

Кособукин, В. А. "Двумерные кулоновские плазмон-экситоны: релаксация возбуждений." Физика твердого тела 63, no. 8 (2021): 1157. http://dx.doi.org/10.21883/ftt.2021.08.51171.078.

Full text

Abstract:

A theory is developed for the relaxation of two-dimensional non-radiative (Coulomb) plasmon-excitons in thin closely located layers of a metal and a semiconductor. In the framework of classical electrodynamics, the equations of motion are formulated for the polarization waves of non-radiative plasmons and excitons with taking into account the Coulomb coupling and the near-field of external polarization. In the model of coupled harmonic oscillators represented by the polarization fields of excitations, the problem of relaxation is solved for Coulomb plasmons, excitons and plasmon-excitons. It is shown that the two dispersion branches of normal plasmon-exciton modes undergo anticrossing (mutual repulsion) at the resonance between plasmon and exciton. With dissipative damping and power interchange between the excitations taken into account, the process of plasmon-exciton relaxation depending on time is investigated. The theory displays the principal analogies between dynamics of plasmon-excitons and of excitations in other objects of linear vibration theory, such as mechanical oscillators, resonant electric chains, etc.

APA, Harvard, Vancouver, ISO, and other styles

39

Binet, A., and J. Bolard. "Recovery of hepatocytes from attack by the pore former amphotericin B." Biochemical Journal 253, no. 2 (July 15, 1988): 435–40. http://dx.doi.org/10.1042/bj2530435.

Full text

Abstract:

Sublytic amounts of the pore former Amphotericin B (AmB) induced transient movements of Na and K ions across the hepatocyte plasma membranes without altering the intracellular free Ca ion concentration. The presence of 1-5 microM-AmB induced leakage of up to 80% of the intracellular K+ within 3 min, followed by Na+ entry without loss of cell viability. A repair process occurred after 3-10 min, which restored the initial cationic concentrations. Progressive binding of AmB to the cells could be observed by following the disappearance of the intense excitonic dichroic doublet of free AmB. It was shown that the amount of AmB binding, responsible for the Na+ and K+ movements, was low (approx. 16% of total AmB). The recovery process occurred when higher amounts of AmB bound to the cells, and was mediated by Na+/K+-ATPase. The c.d. spectrum of AmB bound to isolated hepatocyte plasma membranes, indicated that during this step AmB formed a complex with cholesterol, similar to that formed by the binary mixture in water.

APA, Harvard, Vancouver, ISO, and other styles

40

Chen, T., A. Vierheilig, P. Waltner, W. Kiefer, and A. Materny. "The relaxation process of the excitonic states in polydiacetylene studied by time- and wavenumber-resolved femtosecond coherent anti-Stokes Raman scattering." Chemical Physics Letters 325, no. 1-3 (July 2000): 176–82. http://dx.doi.org/10.1016/s0009-2614(00)00683-7.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Ermolaev, Georgy A., Dmitry I. Yakubovsky, Yury V. Stebunov, Aleksey V. Arsenin, and Valentyn S. Volkov. "Spectral ellipsometry of monolayer transition metal dichalcogenides: Analysis of excitonic peaks in dispersion." Journal of Vacuum Science & Technology B 38, no. 1 (January 2020): 014002. http://dx.doi.org/10.1116/1.5122683.

Full text

APA, Harvard, Vancouver, ISO, and other styles

42

Rivera, Julio A., Sonia J. Bailón-Ruiz, and Oscar J. Perales-Perez. "One-step Aqueous Synthesis of Zn-based Quantum Dots as Potential Generators of Reactive Oxygen Species." MRS Advances 4, no. 07 (2019): 399–404. http://dx.doi.org/10.1557/adv.2019.27.

Full text

Abstract:

AbstractThe actual incorporation of dopant species into the ZnS Quantum Dots (QDs) host lattice will induce structural defects evidenced by a red shift in the corresponding exciton. The doping should create new intermediate energetic levels between the valence and conduction bands of the ZnS and affect the electron-hole recombination. These trap states would favour the energy transfer processes involved with the generation of cytotoxic radicals, so-called Reactive Oxygen Species, opening the possibility to apply these nanomaterials in cancer research. Any synthesis approach should consider the direct formation of the QDs in biocompatible medium. Accordingly, the present work addresses the microwave-assisted aqueous synthesis of pure and doped ZnS QDs. As-synthesized quantum dots were fully characterized on a structural, morphological and optical viewpoint. UV-Vis analyzes evidenced the excitonic peaks at approximately 310 nm, 314 nm and 315 nm for ZnS, Cu-ZnS and Mn-ZnS, respectively, Cu/Zn and Mn/Zn molar ratio was 0.05%. This indicates the actual incorporation of the dopant species into the host lattice. In addition, the Photoluminescence spectrum of non-doped ZnS nanoparticles showed a high emission peak that was red shifted when Mn2+ or Cu2+ were added during the synthesis process. The main emission peak of non-doped ZnS, Cu-doped ZnS and Mn-doped ZnS were observed at 438 nm, 487 nm and 521 nm, respectively. Forthcoming work will address the capacity of pure and Cu-, Mn-ZnS quantum dots to generate cytotoxic Reactive Oxygen Species for cancer treatment applications.

APA, Harvard, Vancouver, ISO, and other styles

43

Das, Soumen, Soumen Basu, Gautam Majumdar, Dipankar Chakravorty, and S. Chaudhuri. "Sol–Gel Synthesized SnO2 Nanoparticles and Their Properties." Journal of Nanoscience and Nanotechnology 7, no. 12 (December 1, 2007): 4402–11. http://dx.doi.org/10.1166/jnn.2007.875.

Full text

Abstract:

Sol–gel synthesized SnO2 nanoparticles with an average size of 2.0 nm obtained at 373 K were gradually annealed to 673 K in air for 25 minutes. Sequentially taken transmission electron microscopy (TEM) images showed that particle agglomeration of these non-matrix SnO2 nanocrystals was a very slow process. The blue shifts of the band gap (∼ 2.3 eV) obtained from the optical absorbance spectra were matched with the theoretical results of the size related excitonic binding energies. These calculations also supported the observed slow grain growth. The depth sensitive hardness measurements of the thin films indicated hardness in the range of 5.03 GPa to 6.79 GPa. These undoped and non-matrix SnO2 nanoparticles were also investigated with the X-ray photoelectrons spectroscopy (XPS), atomic force microscope (AFM), X-ray diffraction spectroscopy (XRD), and ac impedance analyzer.

APA, Harvard, Vancouver, ISO, and other styles

44

Stern, Hannah L., Andrew J. Musser, Simon Gelinas, Patrick Parkinson, Laura M. Herz, Matthew J. Bruzek, John Anthony, Richard H. Friend, and Brian J. Walker. "Identification of a triplet pair intermediate in singlet exciton fission in solution." Proceedings of the National Academy of Sciences 112, no. 25 (June 9, 2015): 7656–61. http://dx.doi.org/10.1073/pnas.1503471112.

Full text

Abstract:

Singlet exciton fission is the spin-conserving transformation of one spin-singlet exciton into two spin-triplet excitons. This exciton multiplication mechanism offers an attractive route to solar cells that circumvent the single-junction Shockley–Queisser limit. Most theoretical descriptions of singlet fission invoke an intermediate state of a pair of spin-triplet excitons coupled into an overall spin-singlet configuration, but such a state has never been optically observed. In solution, we show that the dynamics of fission are diffusion limited and enable the isolation of an intermediate species. In concentrated solutions of bis(triisopropylsilylethynyl)[TIPS]—tetracene we find rapid (<100 ps) formation of excimers and a slower (∼10 ns) break up of the excimer to two triplet exciton-bearing free molecules. These excimers are spectroscopically distinct from singlet and triplet excitons, yet possess both singlet and triplet characteristics, enabling identification as a triplet pair state. We find that this triplet pair state is significantly stabilized relative to free triplet excitons, and that it plays a critical role in the efficient endothermic singlet fission process.

APA, Harvard, Vancouver, ISO, and other styles

45

Moritomo, Yutaka, Kouhei Yonezawa, and Takeshi Yasuda. "Carrier Formation Dynamics in Prototypical Organic Solar Cells as Investigated by Transient Absorption Spectroscopy." International Journal of Photoenergy 2016 (2016): 1–17. http://dx.doi.org/10.1155/2016/9105460.

Full text

Abstract:

Subpicosecond transient absorption spectroscopy is a powerful tool used to clarify the exciton and carrier dynamics within the organic solar cells (OSCs). In this review article, we introduce a method to determine the absolute numbers of the excitons and carriers against delay time (t) only from the photoinduced absorption (PIA) and electrochemically induced absorption (EIA) spectra. Application of this method to rr-P3HT-, PTB7-, and SMDPPEH-based OSCs revealed common aspects of the carrier formation dynamics. First, the temporal evolution of the numbers of the excitons and carriers indicates that the late decay component of exciton does not contribute to the carrier formation process. This is probably because the late component has not enough excess energy to separate into the electron and hole across the donor/acceptor (D/A) interface. Secondly, the spectroscopy revealed that the exciton-to-carrier conversion process is insensitive to temperature. This observation, together with the fast carrier formation time in OSCs, is consistent with the hot exciton picture.

APA, Harvard, Vancouver, ISO, and other styles

46

An, Ki-Seok, Wontae Cho, Byung Kook Lee, Sun Sook Lee, and Chang Gyoun Kim. "Atomic Layer Deposition of Undoped and Al-Doped ZnO Thin Films Usingthe Zn Alkoxide Precursor Methylzinc Isopropoxide." Journal of Nanoscience and Nanotechnology 8, no. 9 (September 1, 2008): 4856–59. http://dx.doi.org/10.1166/jnn.2008.ic47.

Full text

Abstract:

Undoped and Al-doped ZnO thin films have been prepared by atomic layer deposition (ALD) using the Zn precursor methylzinc isopropoxide [MZI, (CH3)Zn(OCH(CH3)2)] with water (H2O). Dimethylaluminum isopropoxide (DMAI) was used as an Al precursor. The self-limiting ALD process via alternate surface reactions of MZI and H2O was confirmed by thickness measurements of the ZnO films with varying MZI supply time and numbers of MZI-H2O ALD cycles. Under optimal reaction conditions, the growth rate of the ZnO films was 1.9∼2.0 Å/cycle in the substrate temperature range of 160∼200 °C and the maximum growth rate reached about 2.58 Å/cycle at 240 °C. Room temperature photoluminescence (PL) measurements revealed a strong free excitonic peak at 3.27 eV with almost negligible deep level emission. Resistivities of ZnO films were measured to be 5 × 10−3 ∼3.2 × 10−3 Ωcm depending on the substrate temperature. By Al-doping, the resistivity was minimized to ∼1 35 × 10−4 Ωcm.

APA, Harvard, Vancouver, ISO, and other styles

47

Zhai, Yaxin, Chuanxiang Sheng, and Z. Valy Vardeny. "Singlet fission of hot excitons in π -conjugated polymers." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 373, no. 2044 (June 28, 2015): 20140327. http://dx.doi.org/10.1098/rsta.2014.0327.

Full text

Abstract:

We used steady-state photoinduced absorption (PA), excitation dependence (EXPA( ω )) spectrum of the triplet exciton PA band, and its magneto-PA (MPA( B )) response to investigate singlet fission (SF) of hot excitons into two separated triplet excitons, in two luminescent and non-luminescent π -conjugated polymers. From the high energy step in the triplet EXPA( ω ) spectrum of the luminescent polymer poly(dioctyloxy)phenylenevinylene (DOO-PPV) films, we identified a hot-exciton SF (HE-SF) process having threshold energy at E ≈2 E T (=2.8 eV, where E T is the energy of the lowest lying triplet exciton), which is about 0.8 eV above the lowest singlet exciton energy. The HE-SF process was confirmed by the triplet MPA( B ) response for excitation at E >2 E T , which shows typical SF response. This process is missing in DOO-PPV solution, showing that it is predominantly interchain in nature. By contrast, the triplet EXPA( ω ) spectrum in the non-luminescent polymer polydiacetylene (PDA) is flat with an onset at E = E g (≈2.25 eV). From this, we infer that intrachain SF that involves a triplet–triplet pair state, also known as the ‘dark’ 2A g exciton, dominates the triplet photogeneration in PDA polymer as E g >2 E T . The intrachain SF process was also identified from the MPA( B ) response of the triplet PA band in PDA. Our work shows that the SF process in π -conjugated polymers is a much more general process than thought previously.

APA, Harvard, Vancouver, ISO, and other styles

48

Singh, Nagendra Pratap, S. A. Shivashankar, and Rudra Pratap. "Defect Driven Emission from ZnO Nano Rods Synthesized by Fast Microwave Irradiation Method for Optoelectronic Applications." MRS Proceedings 1633 (2014): 75–80. http://dx.doi.org/10.1557/opl.2014.254.

Full text

Abstract:

ABSTRACTBecause of its large direct band gap of 3.37 eV and high exciton binding energy (∼60 meV), which can lead to efficient excitonic emission at room temperature and above, ZnO nanostructures in the würtzite polymorph are an ideal choice for electronic and optoelectronic applications. Some of the important parameters in this regard are free carrier concentration, doping compensation, minority carrier lifetime, and luminescence efficiency, which are directly or indirectly related to the defects that, in turn, depend on the method of synthesis. We report the synthesis of undoped ZnO nanorods through microwave irradiation of an aqueous solution of zinc acetate dehydrate [Zn(CH3COO)2. 2H2O] and KOH, with zinc acetate dihydrate acting as both the precursor to ZnO and as a self-capping agent. Upon exposure of the solution to microwaves in a domestic oven, ZnO nanorods 1.5 µm -3 µm and 80 nm in diameter are formed in minutes. The ZnO structures have been characterised in detail by X-ray diffraction (XRD), selective area electron diffraction (SAED) and high-resolution scanning and transmission microscopy, which reveal that each nanorod is single-crystalline. Optical characteristics of the nanorods were investigated through photoluminescence (PL) and cathodoluminescence (CL). These measurements reveal that defect state-induced emission is prominent, with a broad greenish yellow emission. CL measurements made on a number of individual nanorods at different accelerating voltages for the electrons show CL intensity increases with increasing accelerating voltage. A red shift is observed in the CL spectra as the accelerating voltage is raised, implying that emission due to oxygen vacancies dominates under these conditions and that interstitial sites can be controlled with the accelerating voltage of the electron beam. Time-resolved fluorescence (TRFL) measurements yield a life time (τ) of 9.9 picoseconds, indicating that ZnO nanorods synthesized by the present process are excellent candidates for optoelectronic devices.

APA, Harvard, Vancouver, ISO, and other styles

49

Samanta, Samaresh, Subir Kumar Ray, Shubham Deolka, Sudipta Saha, Pradeep K. R., Rohit Bhowal, Nirmalya Ghosh, and Debangshu Chaudhuri. "Safeguarding long-lived excitons from excimer traps in H-aggregated dye-assemblies." Chemical Science 11, no. 22 (2020): 5710–15. http://dx.doi.org/10.1039/d0sc01784a.

Full text

Abstract:

An unusually large exciton coupling and spontaneous self-localization safeguards the long-lived excitons of H-aggregated perylene bisimide against a notoriously universal excimeric trapping process, and rekindles its potential as a light-harvesting material.

APA, Harvard, Vancouver, ISO, and other styles

50

Crapanzano, Roberta, Irene Villa, Silvia Mostoni, Massimiliano D’Arienzo, Barbara Di Credico, Mauro Fasoli, Roberto Scotti, and Anna Vedda. "Morphology Related Defectiveness in ZnO Luminescence: From Bulk to Nano-Size." Nanomaterials 10, no. 10 (October 7, 2020): 1983. http://dx.doi.org/10.3390/nano10101983.

Full text

Abstract:

This study addresses the relationship between material morphology (size, growth parameters and interfaces) and optical emissions in ZnO through an experimental approach, including the effect of different material dimensions from bulk to nano-size, and different excitations, from optical sources to ionizing radiation. Silica supported ZnO nanoparticles and ligand capped ZnO nanoparticles are synthesized through a sol–gel process and hot injection method, respectively. Their optical properties are investigated by radioluminescence, steady-state and time-resolved photoluminescence, and compared to those of commercial micrometric powders and of a bulk single crystal. The Gaussian spectral reconstruction of all emission spectra highlights the occurrence of the same emission bands for all samples, comprising one ultraviolet excitonic peak and four visible defect-related components, whose relative intensities and time dynamics vary with the material parameters and the measurement conditions. The results demonstrate that a wide range of color outputs can be obtained by tuning synthesis conditions and size of pure ZnO nanoparticles, with favorable consequences for the engineering of optical devices based on this material.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Excitonic process'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles