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 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 Singlet Exciton Fission a Multi exciton Generation Process in Organic Semiconductor Solar Cells written by Priyadarshani Jadhav and published by . This book was released on 2012 with total page 115 pages. Available in PDF, EPUB and Kindle. Book excerpt: Organic semiconductor photovoltaics hold the promise of cheap production and low manufacturing setup costs. The highest efficiency seen in research labs, ~10% today, is still too low for production. In this work we explore implementations of a multiple exciton generation process, singlet exciton fission, to work around the Shockley-Queisser limit, according to which, all single junctions cells have a theoretical efficiency limit of 33.7%. This is the first implementation of a singlet fission photovoltaic. We measured a singlet fission efficiency of 72% at room temperature. We showed that singlet fission can be implemented in bulk heterojunction photovoltaics, which is an important result since some of the highest efficiency organic photovoltaics in the last 5 years have been bulk heterojunction structures. Secondly, we showed that the magnetic field effect can be used as a probe to investigate triplet dissociation in singlet fission devices. Thirdly, we implemented singlet fission photovoltaics, using the singlet fission material pentacene as donor and low bandgap infrared-absorptive lead chalcogenide quantum dots as acceptors. Singlet fission can enhance the efficiency of organic photovoltaics only if the fission material is paired with an absorptive low-energy-gap material. We find that pentacene triplet excitons dissociate at the pentacene/quantum dot heterojunctions with an internal quantum efficiency of 35%. Lastly, we investigate a series of materials to find a better acceptor in singlet fission photovoltaics using the methods and some results from the previous two investigations. We investigate device structures that pair pentacene and 6,13 diphenyl-pentacene as singlet fission donors with C60 , perylene diimides, PbS quantum dots and PbSe quantum dots as acceptors.
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 Advanced Concepts in Photovoltaics written by Arthur J. Nozik and published by Royal Society of Chemistry. This book was released on 2014-07-10 with total page 631 pages. Available in PDF, EPUB and Kindle. Book excerpt: Photovoltaic systems enable the sun’s energy to be converted directly into electricity using semiconductor solar cells. The ultimate goal of photovoltaic research and development is to reduce the cost of solar power to reach or even become lower than the cost of electricity generated from fossil and nuclear fuels. The power conversion efficiency and the cost per unit area of the phototvoltaic system are critical factors that determine the cost of photovoltaic electricity. Until recently, the power conversion efficiency of single-junction photovoltaic cells has been limited to approximately 33% - the so-called Shockley-Queisser limit. This book presents the latest developments in photovoltaics which seek to either reach or surpass the Shockley-Queisser limit, and to lower the cell cost per unit area. Progress toward this ultimate goal is presented for the three generations of photovoltaic cells: the 1st generation based on crystalline silicon semiconductors; the 2nd generation based on thin film silicon, compound semiconductors, amorphous silicon, and various mesoscopic structures; and the 3rd generation based on the unique properties of nanoscale materials, new inorganic and organic photoconversion materials, highly efficient multi-junction cells with low cost solar concentration, and novel photovoltaic processes. The extent to which photovoltaic materials and processes can meet the expectations of efficient and cost effective solar energy conversion to electricity is discussed. Written by an international team of expert contributors, and with researchers in academia, national research laboratories, and industry in mind, this book is a comprehensive guide to recent progress in photovoltaics and essential for any library or laboratory in the field.
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 Singlet Fission Holds Two for One Potential in Solar Cells Fact Sheet written by and published by . This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: NREL scientists have confirmed the first molecular compound specifically designed to exhibit multiple-exciton generation through singlet fission - in effect, producing two electrons for every one photon absorbed by the compound. And in related work, NREL has reported the first proven instance of multiple-exciton generation in an operating quantum-dot solar cell.
Download or read book Photosynergetic Responses in Molecules and Molecular Aggregates written by Hiroshi Miyasaka and published by Springer Nature. This book was released on 2020-09-05 with total page 593 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book compiles the accomplishments of the recent research project on photochemistry “Photosynergetics”, supported by the Ministry of Education, Culture, Sports, Science and Technology of Japan, aiming to develop and elucidate new methods and molecules leading to advanced utilization of photo-energies. Topics include photochemical responses induced by multiple excitation, multiphoton absorption, strong modulation of electronic states, developments of new photofunctional molecules, mesoscopic actuations induced by photoexcitation, and novel photoresponses in molecules and molecular assemblies. The authors stress that these approaches based on the synergetic interaction among many photons and many molecules enable the expansion of the accessibility to specific electronic states. As well, they explain how the development of reaction sequences and molecules/molecular assemblies ensure “additivity” and “integration” without loss of the photon energy, leading to new photoresponsive assemblies in meso- and macroscopic scales.
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 Advanced Micro and Nanomaterials for Photovoltaics written by and published by Elsevier. This book was released on 2019-05-25 with total page 342 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanomaterials are becoming increasingly important photovoltaic technologies from absorbers to contacts. This book is dedicated to describing the novel materials and technologies for photovoltaics that derive from these new and novel approaches in solar technologies. We have collected a set of renowned experts in their respective fields as authors and their expertise covers a broad set of areas including novel oxides, quantum dots, CZTS and organic solar cells, as well as light management and reliability testing. The organization of the book is divided into three sections; the first part deals with emerging photovoltaic absorbers and absorber approaches, the second part is focused on novel solar cell architectures and device concepts and components; and the last part is focused on their integration into module technologies. The first chapter is an introduction to the basics of solar cells technology facilitating an understanding by the non-expert of the following chapters. The book is intended for academics and professionals, at the research and R&D level in materials and devices, who are looking for opportunities for applications in the solar materials, devices and modules areas. Hopefully it will serve as a reference for students and professionals looking into the potential and development of novel photovoltaic technologies, researchers looking into the development of innovative projects, and teachers in the field of energy and sustainability. - Showcases a range of cutting-edge photovoltaic materials and devices, exploring their special properties and how they are best used - Assesses the challenges of fabricating solar cell devices using nanotechnology - Explores how producing cheaper modules, increasing reliability and increasing efficiency have led to new applications for photovoltaic devices
Download or read book Singlet Fission Organic Solar Cell with Long wavelength Absorption Using Non fullerene Acceptors written by Alice Qianlan Wu and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Organic solar cells made with singlet exciton fission materials are able to convert a single photon into two charges. Paired with a long-wavelength absorbing acceptor material, singlet fission materials enable solar cells that exhibit the quantum efficiency benefits of a multi-junction solar cell, with the simplicity of a single-junction structure. We investigated bilayer solar cells using tetracene, a singlet fission material, and Y6, a long-wavelength non-fullerene acceptor material. We characterized their current-voltage characteristics, internal and external quantum efficiency, and change in photocurrent under a magnetic field. We demonstrated successful triplet exciton dissociation at the donor-acceptor interface and a positive contribution to the photocurrent from singlet fission. In addition, we investigated coupling a thin layer of tetracene to a PM6:Y6 bulk heterojunction solar cell, which is well-known OPV structure. We found that the addition of tetracene boosts external quantum efficiency at its peak absorption wavelengths and the overall power conversion efficiency. Further improvements to the device structure and materials should yield even more promising results.
Download or read book Transfer of Triplet Excitons in Singlet Fission Silicon Solar Cells written by and published by . This book was released on 2021 with total page 171 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 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 Physics of Solar Cells written by Peter Würfel and published by John Wiley & Sons. This book was released on 2008-07-11 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt: Peter Würfel describes in detail all aspects of solar cell function, the physics behind every single step, as well as all the issues to be considered when improving solar cells and their efficiency. Based on the highly successful German version, but thoroughly revised and updated, this edition contains the latest knowledge on the mechanisms of solar energy conversion. Requiring no more than standard physics knowledge, it enables readers to understand the factors driving conversion efficiency and to apply this knowledge to their own solar cell development.
Download or read book Development in Utilizing Singlet Fission and Triplet triplet Annihilation to Improve Solar Cell Efficiency written by Tony Chang-Chi Wu and published by . This book was released on 2018 with total page 113 pages. Available in PDF, EPUB and Kindle. Book excerpt: Our main energy source are burning fossil fuels. Solar energy is a clean, sustainable energy source that does not emit greenhouse gas that causes global warming. In this thesis, singlet fission and triplet-triplet annihilation would be discussed and studied to increase solar cell power conversion efficiency. Singlet fission splits a singlet exciton into two lower energy triplet excitons. This energy down conversion is efficient and have shown near 200% triplet exciton yield. With energy down conversion, thermalization loss in solar cell could be reduced. We have shown singlet fission in tetracene, a suitable down conversion fission material to pair with silicon solar cell, up to 127% of internal quantum yield. To integrate tetracene as the energy down converter for silicon, we have demonstrated triplet exciton transfer from tetracene to silicon with WNx passivation. To show triplet exciton transfer, a spectrally resolved magnetic field effect measurement setup was designed and built. We have also demonstrated a metal-free, solid state optical up conversion system. This is in contrast with most optical up conversion system that uses heavy metal for triplet generation and are limited to solution fabrication based on material restrictions. The novel optical up conversion system provided cheaper material choices as well as better fabrication freedom and potentially longer device operation lifetime.
Download or read book Singlet Fission Sensitizers for Ultra High Efficiency Excitonic Solar Cells written by and published by . This book was released on 2008 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: We have considered the potential benefits offered by using singlet fission sensitizers in photovoltaic cells and identified two key issues involved in the search for such sensitizers.
