Download or read book Electronic Structure Modelling of Singlet Fission in Organic Photovoltaics written by David Turban and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Electronic Structure Band Formation and Singlet Fission Dynamics at Metal organic Interfaces written by Arnulf Stein and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Handbook of Organic Materials for Electronic and Photonic Devices written by Oksana Ostroverkhova and published by Woodhead Publishing. This book was released on 2018-11-30 with total page 914 pages. Available in PDF, EPUB and Kindle. Book excerpt: Handbook of Organic Materials for Electronic and Photonic Devices, Second Edition, provides an overview of the materials, mechanisms, characterization techniques, structure-property relationships, and most promising applications of organic materials. This new release includes new content on emerging organic materials, expanded content on the basic physics behind electronic properties, and new chapters on organic photonics. As advances in organic materials design, fabrication, and processing that enabled charge unprecedented carrier mobilities and power conversion efficiencies have made dramatic advances since the first edition, this latest release presents a necessary understanding of the underlying physics that enabled novel material design and improved organic device design. - Provides a comprehensive overview of the materials, mechanisms, characterization techniques, and structure property relationships of organic electronic and photonic materials - Reviews key applications, including organic solar cells, light-emitting diodes electrochemical cells, sensors, transistors, bioelectronics, and memory devices - New content to reflect latest advances in our understanding of underlying physics to enable material design and device fabrication
Download or read book Singlet Fission Photovoltaics written by Jiye Lee and published by . This book was released on 2013 with total page 151 pages. Available in PDF, EPUB and Kindle. Book excerpt: The efficiency of a solar cell is restricted by the "single junction limit," whereby photons with energy higher than the bandgap lose energy by thermalization. Singlet exciton fission splits a high-energy molecular excitation ("singlet" exciton) into a pair of lowenergy ones ("triplet" excitons). In solar cells, it promises to generate two electrons per photon, potentially overcoming the singlet junction efficiency limit. In this thesis, we present singlet-fission-based photovoltaic cells that generate more than one electron per photon. We first demonstrate organic photodetectors with quantum efficiencies reaching 100% by exploiting singlet exciton fission. Through study of the magnetic field dependence of the fission process, we find an optimum thickness of singlet fission layers that guarantees the nearly 100% conversion of a singlet into two triplets. By employing an exciton blocking layer and a light trapping scheme to the solar cell, we demonstrate the peak external quantum efficiency exceeding 100% in the visible spectrum. It is the first time that any solar cell has generated more than one electron per photon outside the UV spectrum. We also build a simple model that predicts the rate of singlet fission through intermolecular coupling, enabling rational designs of singlet fission molecules and devices. Finally, we propose a future direction-generating three electrons per photon. As a step toward this goal, we demonstrate singlet exciton fission in hexacene, whose energetics may allow a singlet to split into three triplets.
Download or read book Electronic Structure of Organic Semiconductors written by Luís Alcácer and published by Morgan & Claypool Publishers. This book was released on 2018-12-07 with total page 135 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written in the perspective of an experimental chemist, this book puts together some fundamentals from chemistry, solid state physics and quantum chemistry, to help with understanding and predicting the electronic and optical properties of organic semiconductors, both polymers and small molecules. The text is intended to assist graduate students and researchers in the field of organic electronics to use theory to design more efficient materials for organic electronic devices such as organic solar cells, light emitting diodes and field effect transistors. After addressing some basic topics in solid state physics, a comprehensive introduction to molecular orbitals and band theory leads to a description of computational methods based on Hartree-Fock and density functional theory (DFT), for predicting geometry conformations, frontier levels and energy band structures. Topological defects and transport and optical properties are then addressed, and one of the most commonly used transparent conducting polymers, PEDOT:PSS, is described in some detail as a case study.
Download or read book Relating Nanoscale Structure to Electronic Function in Organic Semiconductors Using Time resolved Spectroscopy written by Christopher Grieco and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Molecular packing arrangements at the nanoscale level significantly contribute to the ultimate photophysical properties of organic semiconducting materials used in solar energy conversion applications. Understanding their precise structure-function relationships will provide insights that can lead to chemical and structural design rules for the next generation of organic solar cell materials. In this work, two major classes of materials were investigated: Singlet fission sensitizers and semiconducting block-copolymers. By exploiting chemical design and film processing techniques, a variety of controllable nanoscale structures could be developed and related to their subsequent photophysical properties, including triplet and charge transport. Time-resolved optical spectroscopies, including both absorption and emission techniques, were used to measure the population dynamics of excited states and charge carriers following photoexcitation of the semiconducting materials. Singlet fission, an exciton multiplication reaction that promises to boost solar cell efficiency by overcoming thermalization loss, has been characterized in several organic molecules. If the energetics are such that the excited state singlet energy is at least twice the triplet energy, then a singlet exciton may split into two triplet excitons through an intermolecular energy-sharing process. The thin film structure of a model singlet fission compound was exploited by modulating its crystallinity and controlling polymorphism. A combination of visible, near-infrared, and mid-infrared transient absorption spectroscopies were used to investigate the precise singlet fission reaction mechanism. It was determined that the reaction intermediates consist of bound triplet pairs that must physically separate in order to complete the reaction, which results in multiplied, independent triplet excitations. Triplet transfer, which is modulated by molecular packing arrangements that control orbital overlap coupling, was found to determine the efficacy of triplet pair separation. Furthermore, the formation of these independent triplets was found to occur on longer (picosecond) timescales than previously believed, indicating that any kinetically competing relaxation processes, such as internal conversion, need to be controlled. Last, it was found that the diffusion of the multiplied triplet excitons, and thus their harvestability in devices, is highly influenced by the crystallinity of the material. In particular, the presence of even a small amount of contaminant amorphous phase was determined to be detrimental to the ultimate triplet diffusion length. Future research directions are outlined, which will be used to develop further chemical and structural design rules for the next generation of singlet fission chromophores. Semiconducting block-copolymers, because of their natural tendency to self-assemble into ordered nanoscale structures, offer an appealing strategy for controlling phase segregation between the hole and electron transport materials in organic solar cells. Such phase segregation is important for both ensuring efficient conversion of the photogenerated excitons into charge carriers, and for creating percolation pathways for efficient transport of the charges to the device electrodes. Time-resolved mid-infrared spectroscopy was developed for monitoring charge recombination kinetics in a series of block-copolymer and polymer blend films possessing distinct, controlled nanoscale morphologies. In addition to explaining previous work that correlated film structure to device efficiency, it was revealed how the covalent linkage in block-copolymers can be carefully designed to prevent rapid recombination losses. Furthermore, novel solution-phase systems of block-copolymer aggregates and nanoparticles were developed for future fundamental spectroscopic work. Future studies promise to explain precisely how polymer chain organization, including intrachain and interchain interactions, governs their ultimate charge photogeneration and transport properties in solar cells.
Download or read book Electronic Processes in Organic Semiconductors written by Anna Köhler and published by John Wiley & Sons. This book was released on 2015-06-08 with total page 436 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first advanced textbook to provide a useful introduction in a brief, coherent and comprehensive way, with a focus on the fundamentals. After having read this book, students will be prepared to understand any of the many multi-authored books available in this field that discuss a particular aspect in more detail, and should also benefit from any of the textbooks in photochemistry or spectroscopy that concentrate on a particular mechanism. Based on a successful and well-proven lecture course given by one of the authors for many years, the book is clearly structured into four sections: electronic structure of organic semiconductors, charged and excited states in organic semiconductors, electronic and optical properties of organic semiconductors, and fundamentals of organic semiconductor devices.
Download or read book Singlet Exciton Fission written by Nicholas John Thompson and published by . This book was released on 2014 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt: Singlet exciton fission transforms a single molecular excited state into two excited states of half the energy. When used in solar cells it can double the photocurrent from high energy photons increasing the maximum theoretical power efficiency to greater than 40%. The steady state singlet fission rate can be perturbed under an external magnetic field. I utilize this effect to monitor the yield of singlet fission within operating solar cells. Singlet fission approaches unity efficiency in the organic semiconductor pentacene for layers more than 5 nm thick. Using organic solar cells as a model system for extracting photocurrent from singlet fission, I exceed the convention limit of 1 electron per photon, realizing 1.26 electrons per incident photon. One device architecture proposed for high power efficiency singlet fission solar cells coats a conventional inorganic semiconducting solar with a singlet fission molecule. This design requires energy transfer from the non-emissive triplet exciton to the semiconducting material, a process which has not been demonstrated. I prove that colloidal nanocrystals accept triplet excitons from the singlet fission molecule tetracene. This enables future devices where the combine singlet fission material and nanocrystal system energy transfer triplet excitons produced by singlet fission to a silicon solar cell.
Download or read book Classical And Quantum Dynamics In Condensed Phase Simulations Proceedings Of The International School Of Physics written by Bruce J Berne and published by World Scientific. This book was released on 1998-06-17 with total page 881 pages. Available in PDF, EPUB and Kindle. Book excerpt: The school held at Villa Marigola, Lerici, Italy, in July 1997 was very much an educational experiment aimed not just at teaching a new generation of students the latest developments in computer simulation methods and theory, but also at bringing together researchers from the condensed matter computer simulation community, the biophysical chemistry community and the quantum dynamics community to confront the shared problem: the development of methods to treat the dynamics of quantum condensed phase systems.This volume collects the lectures delivered there. Due to the focus of the school, the contributions divide along natural lines into two broad groups: (1) the most sophisticated forms of the art of computer simulation, including biased phase space sampling schemes, methods which address the multiplicity of time scales in condensed phase problems, and static equilibrium methods for treating quantum systems; (2) the contributions on quantum dynamics, including methods for mixing quantum and classical dynamics in condensed phase simulations and methods capable of treating all degrees of freedom quantum-mechanically.
Download or read book Emerging Strategies to Reduce Transmission and Thermalization Losses in Solar Cells written by Jonas Sandby Lissau and published by Springer Nature. This book was released on 2021-10-13 with total page 348 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book describes emerging strategies to circumvent transmission and thermalization losses in solar cells, and thereby redefine the limits of solar power conversion efficiency. These strategies include the use of organic molecules and rare-earth metal materials. Approaches to augment the efficiency of these processes via near-field enhancement are described as well. This book includes a discussion of state-of-the-art implementations of these emerging strategies in solar cells, both internally, as in molecular intermediate band and charge carrier multiplication, and externally, such as photon up- and down-conversion. Tools for characterization are also provided. Written by leading researchers in the field, this book can be useful to both beginners and experienced researchers in solar energy.
Download or read book Organic Electronics written by Stephen R. Forrest and published by Oxford University Press, USA. This book was released on 2020 with total page 1068 pages. Available in PDF, EPUB and Kindle. Book excerpt: This textbook provides a basic understanding of the principles of the field of organic electronics through to their applications in organic devices. Useful for the student and practitioner, it is both a teaching text and a resource that is a jumping-off point for learning, working and innovating in this rapidly growing field.--Provided by publisher.
Download or read book Diradicaloids written by Jishan Wu and published by CRC Press. This book was released on 2022-04-01 with total page 638 pages. Available in PDF, EPUB and Kindle. Book excerpt: π-Conjugated molecules with an even number of π-electrons usually have a closed-shell ground state. However, recent studies have demonstrated that a certain type of molecules could show open-shell singlet ground state and display diradical-like (diradicaloid) behavior. Their electronic structure can be understood in terms of the “diradical character” and “aromaticity” concepts. They display very different electronic properties from traditional closed-shell π-conjugated molecules and could be used as next-generation molecular materials. This book provides a comprehensive review on the chemistry, physics, and material applications of open-shell singlet diradicaloids. Particularly, it elaborates the fundamental structure–diradical character–electronic property relationships both theoretically and experimentally. The book has been written by leading scientists in the field from Japan, Germany, Spain, Italy, China, and Singapore.
Download or read book Theoretical Investigations of the Electronic Processes in Organic Photovoltaics written by Shane Robert Yost and published by . This book was released on 2013 with total page 311 pages. Available in PDF, EPUB and Kindle. Book excerpt: The design of more efficient organic photovoltaics starts with an increase in understanding of the fundamental processes related to organic photovoltaics, such as the charge separation processes at the organic/organic interface, which can only be remedied by a combined theoretical and experimental effort. In this thesis we use a variety of computational techniques to address current questions in the field or organic photovoltaics. Applying the [delta]SCF method to a test set of conjugated organic molecules we find it has an error of +/-0.3 eV, and by using the [delta]SCF wavefunctions for a multi-reference basis we construct a new perturb then diagonalize multi-reference perturbation theory method that performs well for both ground and excited state potential energy surfaces, called [delta]SCF(2). Our computed singlet fission rates are in near quantitative agreement with experimental measurements in a variety of pentacene derivatives, and we find that the singlet fission mechanism proceeds through a non-adiabatic to adiabatic transition. By combining ab initio rate constants and Kinetic Monti-Carlo we get an accurate prediction of triplet diffusion and show that only a small decrease occurs when the crystal becomes highly disordered, and no significant traps exist. Our models of the organic/organic interface reveals that the the simple picture of constant HOMO and LUMO levels throughout an organic photovoltaic device is only qualitatively accurate at best. At the organic/organic interface effects such as change in the dielectric constant, decreased packing efficiency, and molecular multipole moments all can contribute to changing the HOMO and LUMO levels at the interface by over 0.2 eV, which is large enough to drive apart thermally relaxed charge transfer states at the interface. The work in this thesis provides insight into how to achieve better exciton diffusion and charge separation in organic photovoltaics, as well as insight into a number of electronic processes relevant to organic photovoltaics.
Download or read book On Exciton Vibration and Exciton Photon Interactions in Organic Semiconductors written by Antonios M. Alvertis and published by Springer Nature. This book was released on 2021-10-25 with total page 213 pages. Available in PDF, EPUB and Kindle. Book excerpt: What are the physical mechanisms that underlie the efficient generation and transfer of energy at the nanoscale? Nature seems to know the answer to this question, having optimised the process of photosynthesis in plants over millions of years of evolution. It is conceivable that humans could mimic this process using synthetic materials, and organic semiconductors have attracted a lot of attention in this respect. Once an organic semiconductor absorbs light, bound pairs of electrons with positively charged holes, termed `excitons’, are formed. Excitons behave as fundamental energy carriers, hence understanding the physics behind their efficient generation and transfer is critical to realising the potential of organic semiconductors for light-harvesting and other applications, such as LEDs and transistors. However, this problem is extremely challenging since excitons can interact very strongly with photons. Moreover, simultaneously with the exciton motion, organic molecules can vibrate in hundreds of possible ways, having a very strong effect on energy transfer. The description of these complex phenomena is often beyond the reach of standard quantum mechanical methods which rely on the assumption of weak interactions between excitons, photons and vibrations. In this thesis, Antonios Alvertis addresses this problem through the development and application of a variety of different theoretical methods to the description of these strong interactions, providing pedagogical explanations of the underlying physics. A comprehensive introduction to organic semiconductors is followed by a review of the background theory that is employed to approach the relevant research questions, and the theoretical results are presented in close connection with experiment, yielding valuable insights for experimentalists and theoreticians alike.
Download or read book Multiscale Modelling of Organic and Hybrid Photovoltaics written by David Beljonne and published by Springer. This book was released on 2014-08-12 with total page 407 pages. Available in PDF, EPUB and Kindle. Book excerpt: The series Topics in Current Chemistry presents critical reviews of the present and future trends in modern chemical research. The scope of coverage is all areas of chemical science including the interfaces with related disciplines such as biology, medicine and materials science. The goal of each thematic volume is to give the non-specialist reader, whether in academia or industry, a comprehensive insight into an area where new research is emerging which is of interest to a larger scientific audience. Each review within the volume critically surveys one aspect of that topic and places it within the context of the volume as a whole. The most significant developments of the last 5 to 10 years are presented using selected examples to illustrate the principles discussed. The coverage is not intended to be an exhaustive summary of the field or include large quantities of data, but should rather be conceptual, concentrating on the methodological thinking that will allow the non-specialist reader to understand the information presented. Contributions also offer an outlook on potential future developments in the field. Review articles for the individual volumes are invited by the volume editors. Readership: research chemists at universities or in industry, graduate students.
Download or read book Introduction to Organic Electronic Devices written by Guangye Zhang and published by Springer Nature. This book was released on 2022-10-13 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book comprehensively describes organic electronic devices developed in the past decades. It not only covers the mainstream devices including organic light emitting diodes (OLEDs), organic photovoltaics (OPVs), and organic thin-film transistors (OTFTs) but also includes devices of recent interest such as organic immune transistors, organic photocatalysis devices, and themoelectrical devices. The book starts from the introduction of basic theory of organic semiconductor materials and devices, which acquaints the readers with the concepts of each type of device described in the following chapters. It also discusses the working principles, device layout, and fabrication process of these devices. The book is intended for undergraduate and postgraduate students who are interested in organic electronics, researchers/engineers working in the field of organic electronic devices/systems.
Download or read book Radiationless Transitions written by Sheng Lin and published by Elsevier. This book was released on 2012-12-02 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt: Radiationless Transitions is a critical discussion of research studies on the theory and experiments in radiationless transitions. This book is composed of nine chapters, and begins with discussions on the theory and experiment of photophysical processes of single vibronic levels and/or single rovibronic levels. The subsequent chapters deal with the spectroscopic investigations of intramolecular vibrational relaxation; the dynamics of molecular excitation by light; and the photophysical processes of small molecules in condensed phase. The discussions then shift to the high pressure effects on molecular luminescence and the internal conversion involving localized excitations, presenting one qualitative and one quantitative example, as well as the intersystem crossing with localized excitations. A chapter explores the energy transfer processes that occur after a molecule in solution is excited by light, with an emphasis on solid solutions in which the large amplitude molecular motion is largely quenched. This chapter also looks into the liquid solutions in which the molecules can translate and rotate under the influence of fluctuating forces from the liquid. The concluding chapter focuses on ultrafast processes. Researchers in the fields of physics, chemistry, and biology will benefit from this book.
