Download or read book Investigation of Charge transfer Dynamics in Organic Materials for Solar Cells written by Christian T. Weisspfennig 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 Charge Recombination Transport Dynamics and Interfacial Effects in Organic Solar Cells written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Handbook of Materials Modeling written by Sidney Yip and published by Springer Science & Business Media. This book was released on 2007-11-17 with total page 2903 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first reference of its kind in the rapidly emerging field of computational approachs to materials research, this is a compendium of perspective-providing and topical articles written to inform students and non-specialists of the current status and capabilities of modelling and simulation. From the standpoint of methodology, the development follows a multiscale approach with emphasis on electronic-structure, atomistic, and mesoscale methods, as well as mathematical analysis and rate processes. Basic models are treated across traditional disciplines, not only in the discussion of methods but also in chapters on crystal defects, microstructure, fluids, polymers and soft matter. Written by authors who are actively participating in the current development, this collection of 150 articles has the breadth and depth to be a major contributor toward defining the field of computational materials. In addition, there are 40 commentaries by highly respected researchers, presenting various views that should interest the future generations of the community. Subject Editors: Martin Bazant, MIT; Bruce Boghosian, Tufts University; Richard Catlow, Royal Institution; Long-Qing Chen, Pennsylvania State University; William Curtin, Brown University; Tomas Diaz de la Rubia, Lawrence Livermore National Laboratory; Nicolas Hadjiconstantinou, MIT; Mark F. Horstemeyer, Mississippi State University; Efthimios Kaxiras, Harvard University; L. Mahadevan, Harvard University; Dimitrios Maroudas, University of Massachusetts; Nicola Marzari, MIT; Horia Metiu, University of California Santa Barbara; Gregory C. Rutledge, MIT; David J. Srolovitz, Princeton University; Bernhardt L. Trout, MIT; Dieter Wolf, Argonne National Laboratory.

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 Interfacial Charge Transfer Dynamics in Solid State Hybrid Organic Inorganic Solar Cells written by Arianna Marchioro and published by . This book was released on 2014 with total page 175 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Organic Solar Cells written by Qiquan Qiao and published by CRC Press. This book was released on 2017-12-19 with total page 510 pages. Available in PDF, EPUB and Kindle. Book excerpt: Current energy consumption mainly depends on fossil fuels that are limited and can cause environmental issues such as greenhouse gas emissions and global warming. These factors have stimulated the search for alternate, clean, and renewable energy sources. Solar cells are some of the most promising clean and readily available energy sources. Plus, the successful utilization of solar energy can help reduce the dependence on fossil fuels. Recently, organic solar cells have gained extensive attention as a next-generation photovoltaic technology due to their light weight, mechanical flexibility, and solution-based cost-effective processing. Organic Solar Cells: Materials, Devices, Interfaces, and Modeling provides an in-depth understanding of the current state of the art of organic solar cell technology. Encompassing the full spectrum of organic solar cell materials, modeling and simulation, and device physics and engineering, this comprehensive text: Discusses active layer, interfacial, and transparent electrode materials Explains how to relate synthesis parameters to morphology of the photoactive layer using molecular dynamics simulations Offers insight into coupling morphology and interfaces with charge transport in organic solar cells Explores photoexcited carrier dynamics, defect states, interface engineering, and nanophase separation Covers inorganic–organic hybrids, tandem structure, and graphene-based polymer solar cells Organic Solar Cells: Materials, Devices, Interfaces, and Modeling makes an ideal reference for scientists and engineers as well as researchers and students entering the field from broad disciplines including chemistry, material science and engineering, physics, nanotechnology, nanoscience, and electrical engineering.

Download or read book Organic Solar Cells written by Wallace C.H. Choy and published by Springer Science & Business Media. This book was released on 2012-11-19 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt: Organic solar cells have emerged as new promising photovoltaic devices due to their potential applications in large area, printable and flexible solar panels. Organic Solar Cells: Materials and Device Physics offers an updated review on the topics covering the synthesis, properties and applications of new materials for various critical roles in devices from electrodes, interface and carrier transport materials, to the active layer composed of donors and acceptors. Addressing the important device physics issues of carrier and exciton dynamics and interface stability and novel light trapping structures, the potential for hybrid organic solar cells to provide high efficiency solar cells is examined and discussed in detail. Specific chapters covers key areas including: Latest research and designs for highly effective polymer donors/acceptors and interface materials Synthesis and application of highly transparent and conductive graphene Exciton and charge dynamics for in-depth understanding of the mechanism underlying organic solar cells. New potentials and emerging functionalities of plasmonic effects in OSCs Interface Degradation Mechanisms in organic photovoltaics improving the entire device lifetime Device architecture and operation mechanism of organic/ inorganic hybrid solar cells for next generation of high performance photovoltaics This reference can be practically and theoretically applied by senior undergraduates, postgraduates, engineers, scientists, researchers, and project managers with some fundamental knowledge in organic and inorganic semiconductor materials or devices.

Download or read book Single Molecule Spectroelectrochemistry of Interfacial Charge Transfer Dynamics In Hybrid Organic Solar Cell written by and published by . This book was released on 2014 with total page 191 pages. Available in PDF, EPUB and Kindle. Book excerpt: Our research under support of this DOE grant is focused on applied and fundamental aspects of model organic solar cell systems. Major accomplishments are: 1) we developed a spectroelectorchemistry technique of single molecule single nanoparticle method to study charge transfer between conjugated polymers and semiconductor at the single molecule level. The fluorescence of individual fluorescent polymers at semiconductor surfaces was shown to exhibit blinking behavior compared to molecules on glass substrates. Single molecule fluorescence excitation anisotropy measurements showed the conformation of the polymer molecules did not differ appreciably between glass and semiconductor substrates. The similarities in molecular conformation suggest that the observed differences in blinking activity are due to charge transfer between fluorescent polymer and semiconductor, which provides additional pathways between states of high and low fluorescence quantum efficiency. Similar spectroelectrochemistry work has been done for small organic dyes for understand their charge transfer dynamics on various substrates and electrochemical environments; 2) We developed a method of transferring semiconductor nanoparticles (NPs) and graphene oxide (GO) nanosheets into organic solvent for a potential electron acceptor in bulk heterojunction organic solar cells which employed polymer semiconductor as the electron donor. Electron transfer from the polymer semiconductor to semiconductor and GO in solutions and thin films was established through fluorescence spectroscopy and electroluminescence measurements. Solar cells containing these materials were constructed and evaluated using transient absorption spectroscopy and dynamic fluorescence techniques to understand the charge carrier generation and recombination events; 3) We invented a spectroelectorchemistry technique using light scattering and electroluminescence for rapid size determination and studying electrochemistry of single NPs in an electrochemical cell. For example, we are able to use this technique to track electroluminescence of single Au NPs, and the electrodeposition of individual Ag NPs in-situ. These metallic NPs are useful to enhance light harvesting in organic photovoltaic systems. The scattering at the surface of an indium tin oxide (ITO) working electrode was measured during a potential sweep. Utilizing Mie scattering theory and high resolution scanning electron microscopy (SEM), the scattering data were used to calculate current-potential curves depicting the electrodeposition of individual Ag NPs. The oxidation of individual presynthesized and electrodeposited Ag NPs was also investigated using fluorescence and DFS microscopies. Our work has produced 1 US provisional patent, 15 published manuscripts, 1 submitted and two additional in-writing manuscripts. 5 graduate students, 1 postdoctoral student, 1 visiting professor, and two undergraduate students have received research training in the area of electrochemistry and optical spectroscopy under support of this award.

Download or read book Plasmonic Organic Solar Cells written by Bo Wu and published by Springer. This book was released on 2016-10-04 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book explores the incorporation of plasmonic nanostructures into organic solar cells, which offers an attractive light trapping and absorption approach to enhance power conversion efficiencies. The authors review the latest advances in the field and discuss the characterization of these hybrid devices using a combination of optical and electrical probes. Transient optical spectroscopies such as transient absorption and transient photoluminescence spectroscopy offer powerful tools for observing charge carrier dynamics in plasmonic organic solar cells. In conjunction with device electrical characterizations, they provide unambiguous proof of the effect of the plasmonic nanostructures on the solar cells’ performance. However, there have been a number of controversies over the effects of such integration – where both enhanced and decreased performance have been reported. Importantly, the new insights into the photophysics and charge dynamics of plasmonic organic solar cells that these spectroscopy methods yield could be used to resolve these controversies and provide clear guidelines for device design and fabrication.

Download or read book Exciton Behaviour at Organic Solar Cell Interfaces written by Olivia Dinica and published by . This book was released on 2015 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: Organic photovoltaics (OPVs) have emerged as a promising class of materials in the production of flexible and cheap solar cells. Polymer OPVs are typically composed of a blend of a semiconducting electron donating polymer with an electron accepting fullerene derivative. This blend leads to a high donor-acceptor interfacial surface area where excitons are split apart to create free charges. The generation of free charges after photo-excitation is a main factor influencing solar cell efficiency. However, the mechanisms of charge transfer and the competing process of charge recombination at the interface are not completely clear. The understanding of these processes is essential for the rational design of materials that can maximize photovoltaic conversion efficiencies. The focus of this dissertation is on the influence that electric fields and chemical structure have on exciton issociation and recombination at the interface of donor-acceptor materials. In particular, we use mixed classical dynamical simulations and electronic structure calculations to investigate several oligomer-fullerene systems. In order to study the potential energy surfaces guiding the dynamics of electron transfer, the nuclear and electron dynamics of large systems need to be simulated. To make these calculations computationally feasible, a mixed quantum classical molecular dynamics (MQCMD) approach was taken. This technique is based on the QCFF/PI formalism first described by Warshel and Karplus and was further developed by Lobaugh and Rossky for the simulation of betaine-30. This approach divides the conjugated system into a classical and a quantum subsystem. The quantum treatment is reserved for the [greek small letter pi] electronic system described by the Pariser-Parr-Pople (PPP) Hamiltonian. The classical potential describes a fully flexible molecular backbone and is modeled using an empirical molecular mechanics force field. In the first part of the dissertation we are examining the effect of an external electric field on charge transfer pathways and rates at sexithiophene/fullerene interfaces. In the second part, we develop a rigorous parametrization technique that allows us to model push-pull polymers. These polymers include PCDTBT and KP115 which have a more complex molecular structure than homo-polymers like the one considered in the first part. We use the QCFF/PI method as well as electronic structure calculations to investigate the influence of molecular structure and donor-acceptor orientation on charge transfer and recombination. The pathways linking exciton formation, charge transfer and thermal relaxation are explored, particularly in the context of dependence in the morphology of the donor molecules as well as the non-adiabatic coupling between excited states.

Download or read book Charge Recombination in Novel Blend Materials for Organic Solar Cells Optical Detection and Kinetic Modelling written by Melissa Van Landeghem and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Spectroscopic Study of Charge transfer States in Organic Semiconductors written by Yun Liu and published by . This book was released on 2021 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt: To achieve net zero carbon emission required for a sustainable economy, global energy production requires a clean and reliable solution. Photovoltaic technology that directly converts sunlight into electricity has demonstrated its potential in contributing to a carbon free energy future. Among myriad solar technologies, photovoltaic cells based on organic semiconductors offer unique advantages of being light weight, flexible and low cost and have shown promising photovoltaic performance with efficiency climbing over 18%. In state-of-the-art organic solar cells, a mixture of polymer electron donor and electron acceptor molecules converts light energy to electrical energy. The rapid performance advancement from 11% to over 18% in recent years is largely achieved by the replacement of fullerene molecules with small molecules as electron acceptors, known as non-fullerene acceptors. These new materials not only unlock promising photovoltaic performance but more importantly pose new photophysical questions that challenge the research community’s original understanding of organic solar cells and suggest new design rules. Central to the photophysics of organic solar cells, as reviewed in Chapter 1, is the charge-transfer state formed between the electron donor molecular and the acceptor molecule. The work presented in this thesis focuses on understanding the properties of the charge-transfer state and its role in mediating energy loss in solar cells. Contrary to the traditional model in which significant driving energy is required to separate tightly bound electron-hole pair in the charge-transfer state, one surprising finding to the organic solar cell community is that the most efficient polymer/non-fullerene organic photovoltaics have negligible driving force for charge separation. Furthermore, compared to fullerene acceptors, non-fullerene acceptors have appreciable absorption, implying that charge generation via hole transfer from acceptor to donor could play an important role. In Chapter 2, via detailed time-resolved and steady state spectroscopic studies, we discover a slow yet efficient generation of the charge-transfer state and charge carriers via hole transfer using a model blend of polymer and non-fullerene acceptors. Our findings also allude to a new photophysical scheme in charge generation that was not observed in polymer/fullerene blends but important to efficient polymer/non-fullerene acceptor blends. Another remarkable property of many efficient polymer/non-fullerene blends is their high photoluminescence efficiency and consequently small non-radiative recombination loss, suggesting that "a great solar cell is also a great light emitting diode" also applies to organic solar cells and prompting research efforts on improving the luminescence efficiency of charge-transfer states. Based on Shockley-Queisser’s theoretical framework, an ideal solar cell should only suffer energy loss from radiative recombination as it is unavoidable, and that any non-radiative recombination is excess. In organic solar cells, however, due to molecular vibrations, non-radiative recombination loss contributes a significant amount to total energy loss. Current research efforts have shown that the non-radiative recombination loss follows an energy-gap law where higher gap materials have intrinsically lower loss. Moreover, photoluminescence yield of the charge-transfer state can be limited by that of the local exciton of the lower bandgap material when these states quantum mechanically mix. In Chapter 3, I combine spectroscopic methods and molecular dynamic calculations to examine in detail what molecular properties determine photoluminescence yield of the charge-transfer state and non-radiative recombination loss of the solar cell. After demonstrating an intrinsically emissive yet charge-generating small molecule blend, I show that due to wavefunction mixing between the charge-transfer state and the local exciton, both photoluminescence quantum yield and lifetime of the local exciton influences emission of the charge-transfer state. The latter is a new consideration for selecting materials for efficient organic photovoltaics and light emitting diodes. In Chapter 4, I propose and show current progress on a previously overlooked spectroscopy method directly detecting wavefunction mixing between the charge-transfer state and the local exciton of non-fullerene acceptor molecules. Our findings and proposal provide direction for molecular design and material selection to limit energy loss in organic solar cells.

Download or read book Solution processable Solar Cell Technologies written by Yeefun Lim and published by . This book was released on 2011 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: The high cost of production of solar panels has prevented the widespread adoption of solar energy. A possible solution is to pursue solution-based solar cell technologies, since they can enable a low-cost and high-throughput manufacturing process. Both organic semiconductors and inorganic nanocrystals have emerged as promising solution-processable materials for solar cells. In this dissertation, I present my work on the investigation of both classes of materials for solar cell applications. Organic photovoltaics consist of donor and acceptor organic semiconductors. The mechanism of charge transfer between the donor poly(3-hexylthiophene) (P3HT) and acceptor C60 was studied by incorporating an inter-layer into the bilayer solar cell. Charge transfer was shown to take place in a two-step process whereby energy transfer of the photo-generated excitons in P3HT to C60 is followed by a backward charge transfer step to P3HT. Novel ways to process these materials are also investigated. Solar cells from P3HT and a fullerene derivative, phenyl C61-butyric acid methyl ester (PCBM) were fabricated by spray-deposition. Good power conversion efficiencies above 2 % were demonstrated, indicating the viability of spray deposition as a fabrication method. In a separate effort, a novel fluorinated resorcinarene photoresist was used to photolithographically pattern solar cells based on a blend of P3HT and PCBM for highvoltage applications. A 15 mm array of 300 solar cells connected in series achieved an open circuit voltage (VOC) of 90 volts. Three new classes of materials for organic solar cell acceptors are presented, namely pentacenes, hexacenes, and anthradithiophenes. Solar cells based on P3HT and pentacenes gave efficiencies as high as 1.2 %. The hexacenes have the lowest bandgap, enabling hexacene-based solar cells to have photocurrent response up to 800 nm. The anthradithiophene-based solar cells achieved the highest VOC approaching 1.1 Volts, and decent efficiencies of around 0.8 %. Finally, a facile alcothermal method for the synthesis of dispersible CuO and Cu2O nanocrystals is presented. A bilayer CuO / PCBM solar cell demonstrated an efficiency of 0.04 %, indicating the potential of these materials for light harvesting applications.

Download or read book Investigation of the Photo induced Charge Transfer in Organic Semiconductors Via Single Molecule Spectroscopy Techniques written by Kwang Jik Lee and published by . This book was released on 2009 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt: Photo-induced charge transfer which occurs between molecules or different parts of a large molecule is the pivotal process related to performances of organic electronics. In particular, injection of charge carriers into conjugated polymers and dissociation of photo-generated excitons at the heterojunction between a donor and acceptor system are of great importance in determining the luminescence efficiency of organic light emitting diodes (OLEDs) and solar energy conversion efficiency of organic solar cells, respectively. However, the complex nature of organic semiconductors as well as complicated primary processes involved in the functioning of these devices have prevented us from understanding unique characteristics of these processes and thereby engineering better materials for higher performances. In this dissertation, two different types of photo-induced (or -related) charge transfer processes occurring in organic semiconductors were investigated by using single molecule spectroscopy (SMS) techniques to unravel the complexities of these processes. The carefully designed functioning capacitor-like model devices similar to OLEDs and photovoltaic cells were fabricated where isolated single nanoparticles were introduced as an active medium to mitigate the complexities of these materials. We observed that injection of positively charged carriers (holes) into poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) single nanoparticles from the carbazole hole transport layer does not occur in the absence of light. We denoted the observed hole injection in aid of light as the light-induced hole transfer mechanism (LIHT). It was revealed that the charging dynamics are highly consistent with a cooperative charging effect. In addition, the LIHT was proposed as the possible source for the formation of deep trapped hole in organic devices. Local exciton dissociation yields across a nanostructured domain between poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) single nanoparticles and either poly(9,9- dioctylfluorene - co - bis-N, N- (4 -butylphenyl)-bis-N, N-phenyl-1,4-phenylene diamine) (PFB) or poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine) (TFB) film in model photovoltaic devices was also investigated. A wide distribution of exciton dissociation yields was observed from each nanodomain due to the device geometry. The observed hysteresis in fluorescence voltage curve was ascribed to accumulated charges following charge separations. The dynamics of charge separation under the applied electric field was described in more detail.

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 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 Synchrotron Radiation in Materials Science written by Chunhai Fan and published by John Wiley & Sons. This book was released on 2018-05-29 with total page 846 pages. Available in PDF, EPUB and Kindle. Book excerpt: Meeting the long-felt need for in-depth information on one of the most advanced material characterization methods, a top team of editors and authors from highly prestigious facilities and institutions covers a range of synchrotron techniques that have proven useful for materials research. Following an introduction to synchrotron radiation and its sources, the second part goes on to describe the various techniques that benefit from this especially bright light, including X-ray absorption, diffraction, scattering, imaging, and lithography. The thrid and final part provides an overview of the applications of synchrotron radiation in materials science. bridging the gap between specialists in synchrotron research and material scientists, this is a unique and indispensable resource for academic and industrial researchers alike.