Download or read book Theoretical Study of Electron Transfer in Organic Solar Cells written by Randa Reslan and published by . This book was released on 2015 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt: Organic solar devices can provide a cheaper alternative to the current silicon-based solar cell devices. The main disadvantage of organic photovoltaic is their low efficiency. Therefore there is a great need to better understand the mechanism of electron transfer in order to improve the efficiency of these devices. The main goal in my dissertation is to find a more accurate measure of electron transfer in these devices. I have been using theoretical methods to study electron transfer in fullerene derivatives, a common component of organic solar devices. One such method that we have investigated is time-dependent split (TD-Split) to study A to B electron transfer by a TD evaluation of the lowest energy transition from the ground state of the combined (AB)- system. Another method that we have developed is the time-dependent ZINDO method (TD-ZINDO) to study absorption. ZINDO is a useful theoretical tool for systems of interest due to its capacity to handle large systems within reasonable times. We were able to perform explicit time calculations with a minimal basis set. The results were then compared with higher order DFT and TDDFT results. We also used a DFT based method to calculate the charge transfer between very large solvated organic dimers like fullerenes from isolated dimer calculations. In this method, a delocalized bias is applied directly to the Fock matrix of the dimer until the extra electron is balanced between the two molecules in the dimers. Then the transfer rate can be calculated using Marcus theory. These theoretical methods differ in accuracy and speed. In my dissertation, I will present these different methods and compare them to each other and to experimental values.

Download or read book Theoretical Studies of the Dynamics of Electron Transfer in Dye Sensitized Solar Cells and of the Mechanism of Singlet Fission in Organic Crystalline Materials written by Francesco Ambrosio and published by . This book was released on 2014 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Solar Energy Conversion written by Piotr Piotrwiak and published by Royal Society of Chemistry. This book was released on 2013 with total page 397 pages. Available in PDF, EPUB and Kindle. Book excerpt: A state-of-the art review on experimental and theoretical approaches to the study of interfacial electron and excitation transfer processes which are so crucial to solar energy conversion.

Download or read book Modelling Charge Transport for Organic Solar Cells within Marcus Theory written by Riccardo Volpi and published by Linköping University Electronic Press. This book was released on 2016-12-20 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the technological advancement of modern society, electronic devices are getting progressively more integrated in our everyday lives. Their continuouslygrowing presence is generating numerous concerns about costs, efficiency and the environmental impact of the electronic waste. In this context, organic electronics is finding its way through the market, allowing for potentially low-cost, light, flexible, transparent and environmentally friendly electronics. Despite the numerous successes of organic electronics, the functioning of several categories of organic devices still represents a technological challenge, due to problems like low efficiencies and stabilities (degradation over time). Organic devices are composed by one or more organic materials depending on the particular application. The conformation and electronic structure of the organic molecules as well as their supramolecular arrangement in the single phase or at the interface are known to strongly a affect the mobility and/or the efficiency of the device. While there is consensus on the fundamental physics of organic devices, we still lack a detailed comprehensive theory able to fully explain experimental data. In this thesis we focus on trying to expand our knowledge of charge transport in organic materials through theoretical modelling and simulation of organic electronic devices. While the methodology developed is generally valid for any organic device, we will particularly focus on the case represented by organic photovoltaics. The morphology of the system is obtained by molecular dynamics simulations. Marcus theory is used to calculate the hopping rate of the charge carriers and subsequently study the possibility of free charge carriers production in an organic solar cell. The theory is then compared both with Kinetic Monte Carlo simulations and with experiments to identify the main pitfalls of the actual theory and ways to improve it. The Marcus rate between two molecules depends on the molecular orbital energies, the transfer integral between the two molecules and the reorganization energy. The orbital energies and the transfer integrals between two neighbouring molecules are obtained through quantum mechanical calculations in vacuum. Electrostatic effects of the environment are included through atomic charges and atomic polarizabilities, producing a correction both to the orbital energy and to the reorganization energy. We have studied several systems in the single phase (polyphenylene vinylene, C60, PC61BM) and at the interface between two organic materials (anthracene/C60, TQ1/PC71BM). We show how a combination of different methodologies can be used to obtain a realistic ab-initio model of organic devices taking into account environmental effects. This allows us to obtain qualitative agreement with experimental data of mobility in the single phase and to determine whether or not two materials are suitable to be used together in an organic solar cell.

Download or read book Development of Solar Cells written by Juganta K. Roy and published by Springer Nature. This book was released on 2021-05-12 with total page 235 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a comprehensive overview of the fundamental concept, design, working protocols, and diverse photo-chemicals aspects of different solar cell systems with promising prospects, using computational and experimental techniques. It presents and demonstrates the art of designing and developing various solar cell systems through practical examples. Compared to most existing books in the market, which usually analyze existing solar cell approaches this volume provides a more comprehensive view on the field. Thus, it offers an in-depth discussion of the basic concepts of solar cell design and their development, leading to higher power conversion efficiencies. The book will appeal to readers who are interested in both fundamental and application-oriented research while it will also be an excellent tool for graduates, researchers, and professionals working in the field of photovoltaics and solar cell systems.

Download or read book Electron Transfer Study for Selected Dye Sensitized Solar Cell and Polymer Solar Cell by Time Resolved Spectroscopy written by Lihong Yu and published by Open Dissertation Press. This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Electron Transfer Study for Selected Dye Sensitized Solar Cell and Polymer Solar Cell by Time-resolved Spectroscopy" by Lihong, Yu, 于利红, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: The pure organic dye sensitized solar cells (DSSCs) were studied and a new organic dye of donor-π-2acceptors (D-π-2A configuration) was fabricated. This dye, denoted as B2, was investigated and applied in DSSCs. Density functional theory (DFT) was used to examine the electronic distribution of the frontier orbitals of the B2 dye. It was found that intramolecular charge transfer (ICT) between the donor moieties and acceptor moieties of the B2 dye may take place under photo irradiation. The LUMO, LUMO+1 and LUMO+2 of B2 are all distributed on the acceptor moieties and this is very helpful to enhance the intramolecular electron transfer from the donor moieties to the acceptor moieties, which will consequently promote the chance of electron injection into the semiconductor. DSSCs based on B2 demonstrated an power conversion efficiency of 3.62 %. This efficiency value is approximately half of the power conversion efficiency of DSSCs based on N719 (7.69 %) under the same conditions. Femtosecond transient absorption and nanosecond transient absorption (TA), and time-correlated single photon counting (TCSPC) technique were applied to examine the electron transfer processes occurring on the surface of B2/TiO2. B2 dye has life time of the excited states three orders in magnitude shorter than that of N719. The electron injection time from excited B2 to TiO2 is also three orders in magnitude shorter than that from excited N719 to TiO2. It was revealed that the delocalized electrons of π → π* transition for both the B2 dye and the N719 dye could be further guided into the semiconductor, while such injection processes may not happen for the localized electrons in π → π* transition of these dyes. The nanosecond transient absorption and transient emission spectroscopy of the ruthenium bipyridyl sensitizer N719 in different solvents were studied. Three kinds of ZnO nanoparticles were utilized to study the electron transfer process taking place on the interface of N719/ZnO with and without electrolyte by Time-Correlated Single Photon Counting (TCSPC) technique, TA and transient emission spectroscopy. Isopropanol was found to stabilize the singlet excited state of N719 and a related emission band centered at 460 nm was observed in nanosecond time scale. It was revealed that the electrolyte has a significant impact upon the electron transfer dynamics on the N719/ZnO interface. In the absence of electrolyte, the electron transfer process on the N719/ZnO interface is dependent upon the depth of defects in ZnO nanoparticles. Conversely, in the presence of electrolyte, the impact of ZnO defects upon the electron transfer process is eliminated and the effective electron injection happens from the excited states of N719 to ZnO, in spite of the ZnO particle sizes. The polymer based solar cells were studied and a polymer incorporated with a pyrenylcarbazole pendant was synthesized and applied in the functionalization of multi-wall carbon nanotubes (MWCNT) by noncovalent π-π interaction. The polymer/MWCNT hybrids were isolated and examined. The strong interaction between the polymer and MWCNT in a 1,1,2,2-tetrachloroethane (TCE) solution was investigated. The emission spectra demonstrated an effective quenching of emission from the polymer by the MWCNT. DFT calculations showed an electron delocalization phenomenon between the pyrene and carbazole moieties. The LUMO

Download or read book Molecular Electrostatic Potentials written by J.S. Murray and published by Elsevier. This book was released on 1996-11-22 with total page 681 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past 25 years, the molecular electrostatic potential has become firmly established as an effective guide to molecular interactions. With the recent advances in computational technology, it is currently being applied to a variety of important chemical and biological systems. Its range of applicability has expanded from primarily a focus on sites for electrophilic and nucleophilic attack to now include solvent effects, studies of zeolite, molecular cluster and crystal behavior, and the correlation and prediction of a wide range of macroscopic properties. Moreover, the increasing prominence of density functional theory has raised the molecular electrostatic potential to a new stature on a more fundamental conceptual level. It is rigorously defined in terms of the electron density, and has very interesting topological characteristics since it explicitly reflects opposing contributions from the nuclei and the electrons. This volume opens with a survey chapter by one of the original pioneers of the use of the electrostatic potential in studies of chemical reactivity, Jacopo Tomasi. Though the flow of the succeeding chapters is not stringently defined, the overall trend is that the emphasis changes gradually from methodology to applications. Chapters discussing more theoretical topics are placed near the end. Readers will find the wide variety of topics provided by an international group of authors both convincing and useful.

Download or read book Electronic Properties of Organic Photovoltaic Materials written by Christopher David Arntsen and published by . This book was released on 2014 with total page 115 pages. Available in PDF, EPUB and Kindle. Book excerpt: Organic solar cells have gained much attention as an inexpensive alternative to traditional inorganic cells. While experimental efforts have steadily improved the efficiency of organic devices, a large portion of the improvements have been the result of trial-and-error. Therefore, it would be ideal to be able to use theory to predict which types of materials would produce the most efficient devices. This dissertation presents a series of theoretical studies designed to improve understanding of what makes certain solar cells perform well and to serve as a predictive tool to screen potential new materials. First, a study of electron transfer in pentacene dimers is presented. The study compares several methods for calculating the electronic transfer integral, including time-dependent density function theory, a time dependent semi-empirical method, and several static calculations. The results demonstrate that at large separations, static calculations can underestimate the strength of coupling. Next, electronic coupling in fullerenes is calculated. In this section, a method for mimicking bulk chemical environments in film through the use of solvation and application of electric fields is developed. The method is a applied to a number of fullerenes used in organic solar cells, and compared with experimental data on local and bulk electron mobilities. Comparing the theory and experiment allows one to identify beneficial self-assembly behavior in the fullerenes studied. This method is then extended to a calculation method we have termed direct delocalization. In this method, a field is applied directly to the Fock matrix in order to delocalize frontier orbitals across a dimer. Once this is accomplished, electronic transfer time is calculated within the standard Marcus theory framework. The results are compared to the more thorough methods described above, and found to be in agreement. Next, the formulation of a stochastic approach to the GW approximation is presented. In this section, a method for calculating the polarization self-energy with stochastic orbitals is introduced. The method is highly efficient, achieving near linear scaling with respect to system size, compared with the theoretical fourth order scaling. The method is applied to large silicon clusters and several fullerenes to accurately calculate quasiparticle energies. Finally, in the last two chapters, several methods for studying plasmons are presented. The first presents a method for studying the interaction between molecules and plasmonic materials. The method interfaces a semiempirical quantum mechanical calculation (to study the molecules) with a finite- ifference time-domain (FDTD) calculation (to study the plasmonic material). The study shows that plasmon propagation can be heavily influenced by the presence of a molecule. In the last section, an alternative FDTD method is presented. This method, labeled near-field, is a time-dependent version of the quasistatic frequency-dependent Poisson algorithm. This approach is advantageous in that it allows for much large time steps in the propagation, greatly expediting the calculation.

Download or read book Experimental and Theoretical Studies of Electron Transfer and Mixed Valence Systems written by Gerald Michael Sando and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation describes several experimental and theoretical studies in the general areas of electron transfer and mixed valency. Experimentally, we have used resonance Raman combined with time dependent spectral modeling to study a possible mixed valence system to determine the nature of the excited state of the molecule. In addition, nanosecond transient absorption was used to study a model of dye sensitized solar cells to help clarify the mechanism of back electron transfer. On the theoretical side, a sum over states formalism was used for predicting rates, absorption spectra, and emission spectra for electron transfer reactions as a function of vibrational mode mixing, revealing a large increase in rate for deeply inverted reactions when the Duschinsky effect is included. An application of the theory to a series of organometallic molecules, the Co(CO)4 and V(CO)6 anion/radical systems, is also discussed. In addition, density functional theory is applied to a related radical pair, [Co(Cp)|V(CO)6], and the importance of these results in analyzing previous experimental ultrafast electron transfer results is discussed. Classical spectral simulations of absorption and Stark spectroscopy of mixed valence systems were also performed, suggesting a breakdown of the Liptay assumptions as the Class II/III limit is approached.

Download or read book Fundamentals of Time Dependent Density Functional Theory written by Miguel A.L. Marques and published by Springer Science & Business Media. This book was released on 2012-01-21 with total page 573 pages. Available in PDF, EPUB and Kindle. Book excerpt: There have been many significant advances in time-dependent density functional theory over recent years, both in enlightening the fundamental theoretical basis of the theory, as well as in computational algorithms and applications. This book, as successor to the highly successful volume Time-Dependent Density Functional Theory (Lect. Notes Phys. 706, 2006) brings together for the first time all recent developments in a systematic and coherent way. First, a thorough pedagogical presentation of the fundamental theory is given, clarifying aspects of the original proofs and theorems, as well as presenting fresh developments that extend the theory into new realms—such as alternative proofs of the original Runge-Gross theorem, open quantum systems, and dispersion forces to name but a few. Next, all of the basic concepts are introduced sequentially and building in complexity, eventually reaching the level of open problems of interest. Contemporary applications of the theory are discussed, from real-time coupled-electron-ion dynamics, to excited-state dynamics and molecular transport. Last but not least, the authors introduce and review recent advances in computational implementation, including massively parallel architectures and graphical processing units. Special care has been taken in editing this volume as a multi-author textbook, following a coherent line of thought, and making all the relevant connections between chapters and concepts consistent throughout. As such it will prove to be the text of reference in this field, both for beginners as well as expert researchers and lecturers teaching advanced quantum mechanical methods to model complex physical systems, from molecules to nanostructures, from biocomplexes to surfaces, solids and liquids. From the reviews of LNP 706: “This is a well structured text, with a common set of notations and a single comprehensive and up-to-date list of references, rather than just a compilation of research articles. Because of its clear organization, the book can be used by novices (basic knowledge of ground-state DFT is assumed) and experienced users of TD-DFT, as well as developers in the field.” (Anna I. Krylov, Journal of the American Chemical Society, Vol. 129 (21), 2007) “This book is a treasure of knowledge and I highly recommend it. Although it is a compilation of chapters written by many different leading researchers involved in development and application of TDDFT, the contributors have taken great care to make sure the book is pedagogically sound and the chapters complement each other [...]. It is highly accessible to any graduate student of chemistry or physics with a solid grounding in many-particle quantum mechanics, wishing to understand both the fundamental theory as well as the exponentially growing number of applications. [...] In any case, no matter what your background is, it is a must-read and an excellent reference to have on your shelf.” Amazon.com, October 15, 2008, David Tempel (Cambridge, MA)

Download or read book Theoretical Studies of the Structure property Relationships of Hole and Electron transport Materials for Organic Photovoltaic Applications written by Laxman Pandey and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Theoretical Studies of Electron Transfer in Complex Media Progress Report written by and published by . This book was released on 1991 with total page 2 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Theoretical Study of Electron Transfer Reactions in Biological and Chemical Systems written by Iraj Daizadeh and published by . This book was released on 1998 with total page 476 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Physical Chemistry and Chemical Physics Editor s Pick 2021 written by Malgorzata Biczysko and published by Frontiers Media SA. This book was released on 2021-07-28 with total page 193 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Theoretical Studies of Electron Transfer in Complex Media written by and published by . This book was released on 1991 with total page 2 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Organic Solar Cells written by Barry P. Rand and published by CRC Press. This book was released on 2014-08-26 with total page 795 pages. Available in PDF, EPUB and Kindle. Book excerpt: Organic photovoltaic (OPV) cells have the potential to make a significant contribution to the increasing energy needs of the future. In this book, 15 chapters written by selected experts explore the required characteristics of components present in an OPV device, such as transparent electrodes, electron- and hole-conducting layers, as well as elect

Download or read book Organic Solar Cells written by Pankaj Kumar and published by CRC Press. This book was released on 2016-10-03 with total page 452 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains detailed information on the types, structure, fabrication, and characterization of organic solar cells (OSCs). It discusses processes to improve efficiencies and the prevention of degradation in OSCs. It compares the cost-effectiveness of OSCs to those based on crystalline silicon and discusses ways to make OSCs more economical. This book provides a practical guide for the fabrication, processing, and characterization of OSCs and paves the way for further development in OSC technology.