Download or read book Nanomorphology Control and Novel Materials Studies in Polymer fullerene Bulk Heterojunction Solar Cells written by Yan Yao and published by . This book was released on 2008 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Device Physics and Recombination in Polymer Fullerene Bulk Heterojunction Solar Cells written by Steven Hawks and published by . This book was released on 2015 with total page 241 pages. Available in PDF, EPUB and Kindle. Book excerpt: My thesis focuses on improving and understanding a relatively new type of solar cell materials system: polymer:fullerene bulk-heterojunction (BHJ) blends. These mixtures have drawn significant interest because they are made from low-cost organic molecules that can be cast from solution, which makes them a potential cheap alternative to traditional solar cell materials like silicon. The drawback, though, is that they are not as efficient at converting sunlight into electricity. My thesis focuses on this issue, and examines the loss processes holding back the efficiency in polymer:fullerene blends as well as investigates new processing methods for overcoming the efficiency limitations. The first chapter introduces the subject of solar cells, and polymer:fullerene solar cells in particular. The second chapter presents a case study on recombination in the high-performance PBDTTT polymer family, wherein we discovered that nongeminate recombination of an anti-Langevin origin was the dominant loss process that ultimately limited the cell efficiency. Electroluminescence measurements revealed that an electron back-transfer process was prevalent in active layers with insufficient PC$_{71}$BM content. This work ultimately made strong headway in understanding what factors limited the relatively unexplored but highly efficient PBDTTT family of polymers. In the next chapter, I further explore the recombination mechanisms in polymer:fullerene BHJs by examining the dark diode ideality factor as a function of temperature in several polymer:fullerene materials systems. By re-deriving the diode law for a polymer:fullerene device with Shockley-Read-Hall recombination, we were able to confirm that trap-assisted recombination through an exponential band-tail of localized states is the dominant recombination process in many polymer:fullerene active layers. In the third chapter, I present a generalized theoretical framework for understanding current transients in planar semiconductor devices, like those discussed above. My analysis reveals that the apparent free-carrier concentration obtained via the usual integral approach is altered by a non-trivial factor of two, sometimes leading to misinterpretations of the charge densities and overall device physics. This new perspective could have far-reaching effects on semiconductor research and technology. Finally, in the last two chapters, I discuss the device physics associated with a relatively novel method for fabricating nanoscale polymer:fullerene BHJs: solution sequential processing (SqP). In particular, I compare recombination in SqP vs. traditionally processed blend-cast devices, and demonstrate that SqP is a more scalable method for making BHJ solar cells. In the final chapter, I examine an unexpected discovery that occurred while working on the content in Chapter 5. Specifically, Chapter 6 examines electrode metal penetration in the SqP quasi-bilayer active layer architecture. Therein, we unexpectedly found that evaporated metal can readily penetrate into fullerene-rich layers, up to $\sim$70 nm or more. The details and consequences of this surprising occurrence are discussed in detail.

Download or read book Polymer Photovoltaics written by Fei Huang and published by Royal Society of Chemistry. This book was released on 2016 with total page 422 pages. Available in PDF, EPUB and Kindle. Book excerpt: An international perspective on the latest research in polymer solar cell technology.

Download or read book Process structure property relationship of polymer fullerene bulk heterojunction films for organic solar cells written by Benjamin Schmidt-Hansberg and published by Cuvillier Verlag. This book was released on 2012-05-09 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt: Photovoltaic (PV) is attracting increasing interest as an important contribution to renewable energy supply. Organic photovoltaic (OPV) is a comparable young PV technology with a great potential towards low cost solar power. This is due to the intrinsic advantage of the incorporated organic semiconductors which are soluble. Solution processing allows high throughput coating and printing processes. Hence, energy intensive high temperature and vacuum steps can be avoided which reduces the fabrication costs and keeps energy payback times low. The performance of organic solar cells strongly depends on the structure of the solution cast photoactive layer which comprises a polymer-fullerene blend. The blend structure evolves during the film drying step which has been studied in this thesis. Starting point of this work was the hypothesis that drying process parameters are suitable for systematically tuning the structure formation during drying of solution cast polymer-fullerene films in order to generate optimized structures with improved photovoltaic performance. For the evaluation of this hypothesis the structure formation of the polymer-fullerene system Poly(3-hexylthiophene-2,5-diyl):[6,6]-Phenyl C61-butyric acid methyl ester (P3HT:PCBM) was investigated incorporating i) thin film drying kinetics, ii) phase behavior of polymer-fullerene solutions, iii) structure formation and iv) the drying process-structure-property relationship of solar cells. The generality of the obtained results has been studied in comparison with the behavior of Poly{[4,40-bis(2-ethylhexyl)dithieno(3,2-b;20,30-d)silole]-2,6-diyl-alt-(2,1,3-benzothidiazole)-4,7-diyl} (PSBTBT). i) Within this thesis a dedicated coating and drying setup was developed which afforded precisely defined coating and drying process conditions as prerequisite for all obtained results. For the first time, the drying behavior of finally a few hundred nanometer thin films could be investigated at five measurement positions with laser reflectometry simultaneously. This allowed the elaboration of a spatially resolved numerical thin film drying model. ii) In conjunction with the measurement and simulation of the evolution of film composition it was required to determine important instants of phase transitions such as solubility limits. Therefore the binodal region of P3HT solutions has been determined in the temperature range of 0°C-60°C. Within the unstable region P3HT solutions phase separate into a sol and a gel phase. The fullerene PCBM exhibits only a single solubility limit. iii) In order to correlate the expected phase transitions according to the phase diagrams with the real structure formation, the above mentioned coating and drying setup was combined with synchrotron based in situ grazing incidence X-ray diffraction (GIXD) measurements. This gave unique insights into the mechanisms and dynamics of polymer-fullerene blend crystallization. After reaching P3HT solubility the crystallization proceeded with well-oriented interface-induced P3HT nucleation followed by P3HT crystal growth with increasing orientation distribution of the crystallites and PCBM aggregation in the final drying period. Furthermore strong polymer-fullerene interaction forces could be derived. By increasing the PCBM fraction it could be shown for the 1:2 P3HT:PCBM ratio that PCBM molecules brake the (020) π-π-stacking of P3HT lamellae which signifies a dramatic loss of hole mobility and consequently reduced device performance. It is further notable that increasing drying temperatures reduce the amount of (020) π-π-stacked P3HT molecules but lead to an increased amount of P3HT (100) crystallinity. Hence, drying temperature determines the preferred direction of crystal growth. iv) Besides a finer degree of phase separation, reduced drying temperatures also cause a higher amount of π-π-stacked polymers, longer effective polymer conjugation length, increased amount of vertical charge transport pathways and an increasingly rough topography due to larger polymer aggregates. Jointly this leads to improved power conversion efficiency at lower drying temperatures. Based on the elaborated knowledge a strategy for a 40% reduction of drying time with only small drawbacks in solar cell performance could be developed. Finally it was important to investigate the transferability of the obtained knowledge to other material systems. PSBTBT:PC71BM blends show similarities to that of P3HT:PCBM with partly interface induced polymer nucleation and subsequent fullerene aggregation in the final drying stage. The kinetics of molecular ordering however proceed fast enough such that the drying process under the investigated conditions cannot limit the structure formation. Hence, P3HT:PCBM is a suitable model system due to its sensitivity to many process parameters. According to the process influence on novel materials the results of this thesis can serve as a source for appropriate process strategies.

Download or read book Controlled Morphology in Bulk Heterojunction Polymer and Perovskite Solar Cells written by Yan Sun and published by . This book was released on 2016 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bulk heterojunction (BHJ) polymer solar cells constitute an emerging approach to a low cost, solution processable, and highly scalable renewable energy avenue. However, one of the major challenges limiting the broad applicability of these solar cells is their lower device efficiencies compared to their inorganic counterparts. In this regard, much effort has been dedicated to optimizing the efficiencies by developing new high-performance materials and fine tuning the BHJ blend morphology via various processing methods. This study presents a molecular level understanding of what controls the device performance.In the first part, a novel fulleropyrrolidine derivative C60-fused N-(3-methoxypropyl)-2-(carboxyethyl)-5-(4-cyanophenyl) fulleropyrrolidine (NCPF) was synthesized and blended with a conjugated polymer poly(3-hexylthiophene) (P3HT) for applications of BHJ polymer solar cells. NCPF has a good solubility in common organic solvents and comparable electronic properties with the widely used acceptor [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). A short term thermal annealing induced enhancement in device performance was found to be associated with improved crystallization of polymer within blend thin films and correspondingly increased hole mobility. The long term annealing study showed that P3HT:NCPF blends had superior thermal stability compared to P3HT:PCBM blends. In the second part, we demonstrate the compatibilization effect of a rod-coil block copolymer (BCP) in different polymer:fullerene derivative blend systems. AFM results and GIWAXS analyses revealed that the addition of BCP into the blend thin films effectively altered the thin film nanostructure and polymer crystalline structure. Moreover, higher device efficiencies were obtained in blends containing block copolymer compatibilizer. The improvement in performance was then ascribed to the morphological changes in the polymer:fullerene blends.The final study deals with the application of a simple, high throughput and roll-to-roll compatible process, zone annealing, to process polymer:fullerene BHJ blends. By morphological study, we established a regime in which interpenetrating phase separated morphology was obtained via zone annealing that exhibited no overgrown fullerene crystallites. Moreover, we extend the use of zone annealing method to perovskite materials, i.e. inorganic--organic hybrid lead halide perovskites. The zone annealed perovskite film morphology exhibits a transition from densely packed structures to dendritic crystallizations with increasing sample annealing velocity. This transition shifts to lower speed in higher temperature condition. By varying temperature and the sweeping speed, large grains were observed in zone annealed samples. Collectively, these studies provide a more fundamental and deeper understanding of the relationships between materials, processing, morphology and performance of thin film solar cells.

Download or read book Polymeric Solar Cells written by Frederik C. Krebs and published by DEStech Publications, Inc. This book was released on 2010 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: Book offers a comprehensive treatment of nonhybrid polymeric solar cells from the basic chemistry of donor and acceptor materials through device design, processing and manufacture. Written by a team of Europe-based experts, the text shows the steps and strategies of successfully moving from the science of solar cells to commercial device production. Chapters focus on technologies that lead to increased efficiencies, longer usable life and lower costs. Highlighted are ways to fabricate solar cells from a range of polymers and develop them into marketable commodities. Special consideration is given to solar cells as intellectual property.

Download or read book Morphology Studies of Polymer Bulk Heterojunction Solar Cells written by Ji Sun Moon and published by . This book was released on 2011 with total page 127 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis is a study of the morphology of polymer:fullerene BHJ, one of the most critical and challenging parts of high efficiency polymer solar cells. To discover the morphology, cross-section as well as top-down transmission electron microscopy were used. The contrast was achieved by utilizing phase contrast microscopy. Thermal annealing, dependence of BHJ thickness, processing additives, solution sequential process and solution sequential process with the use of cosolvent that affects/controls the BHJ morphology are studied in detail.

Download or read book Morphology of Bulk Heterojunction Materials in Polymer Based Solar Cells written by Wanli Ma and published by . This book was released on 2006 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt: Solar cell technology based on conjugated polymer/fullerene composites continues to be of interest as a potential source of renewable energy. By applying rigorous fabrication conditions and postproduction annealing at 150°C, polymer solar cells with 5% power conversion efficiency are demonstrated. These devices exhibit remarkable thermal stability. We attribute the improved performance to morphology changes in the bulk heterojunction material induced by thermal annealing.

Download or read book Dissertation Abstracts International written by and published by . This book was released on 2009 with total page 810 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Polymer Solar Cells Molecular Design and Microstructure Control written by Kui Zhao and published by Frontiers Media SA. This book was released on 2020-12-10 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt: This eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contact.

Download or read book Polymer written by Jeroen Karolus Johannes van Duren and published by . This book was released on 2004 with total page 133 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Optical and Electrical Modeling of Polymer written by Jan Derk Kotlarski and published by . This book was released on 2012 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Controlling the Electronic Interface Properties in Polymer Fullerene Bulk Heterojunction Solar Cells written by Tobias Stubhan and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Handbook of Conducting Polymers 2 Volume Set written by Terje A. Skotheim and published by CRC Press. This book was released on 2007-01-16 with total page 1692 pages. Available in PDF, EPUB and Kindle. Book excerpt: Learn how recent advances are fueling new possibilities in textiles, optics, electronics, and biomedicine! As the field of conjugated, electrically conducting, and electroactive polymers has grown, the Handbook of Conducting Polymers has been there to document and celebrate these changes along the way. Now split into two vo

Download or read book written by and published by . This book was released on 1995 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Studies of Charge Transport and Energy Level in Solar Cells Based on Polymer fullerene Bulk Heterojunction written by Abay Gadisa and published by . This book was released on 2006 with total page 61 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Conjugated Polymers written by Terje A. Skotheim and published by CRC Press. This book was released on 2006-12-26 with total page 1030 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many significant fundamental concepts and practical applications have developed since the publication of the best-selling second edition of the Handbook of Conducting Polymers. Now divided into two books, the third edition continues to retain the excellent expertise of the editors and world-renowned contributors while providing superior coverage of