TY - JOUR A1 - Albrecht, Steve A1 - Schaefer, Sebastian A1 - Lange, Ilja A1 - Yilmaz, Seyfullah A1 - Dumsch, Ines A1 - Allard, Sybille A1 - Scherf, Ullrich A1 - Hertwig, Andreas A1 - Neher, Dieter T1 - Light management in PCPDTBT:PC70BM solar cells: A comparison of standard and inverted device structures JF - Organic electronics : physics, materials and applications N2 - We compare standard and inverted bulk heterojunction solar cells composed of PCPDTBT:PC70BM blends. Inverted devices comprising 100 nm thick active layers exhibited short circuit currents of 15 mA/cm(2), 10% larger than in corresponding standard devices. Modeling of the optical field distribution in the different device stacks proved that this enhancement originates from an increased absorption of incident light in the active layer. Internal quantum efficiencies (IQEs) were obtained from the direct comparison of experimentally derived and modeled currents for different layer thicknesses, yielding IQEs of similar to 70% for a layer thickness of 100 nm. Simulations predict a significant increase of the light harvesting efficiency upon increasing the layer thickness to 270 nm. However, a continuous deterioration of the photovoltaic properties with layer thickness was measured for both device architectures, attributed to incomplete charge extraction. On the other hand, our optical modeling suggests that inverted devices based on PCPDTBT should be able to deliver high power conversion efficiencies (PCEs) of more than 7% provided that recombination losses can be reduced. KW - Organic solar cells KW - Inverted solar cells KW - PCPDTBT KW - Low band-gap KW - Optical modeling Y1 - 2012 U6 - https://doi.org/10.1016/j.orgel.2011.12.019 SN - 1566-1199 VL - 13 IS - 4 SP - 615 EP - 622 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Moule, Adam J. A1 - Neher, Dieter A1 - Turner, Sarah T. ED - Ludwigs, S T1 - P3HT-Based solar cells: structural properties and photovoltaic performance JF - Advances in Polymer Science JF - Advances in Polymer Science N2 - Each year we are bombarded with B.Sc. and Ph.D. applications from students that want to improve the world. They have learned that their future depends on changing the type of fuel we use and that solar energy is our future. The hope and energy of these young people will transform future energy technologies, but it will not happen quickly. Organic photovoltaic devices are easy to sketch, but the materials, processing steps, and ways of measuring the properties of the materials are very complicated. It is not trivial to make a systematic measurement that will change the way other research groups think or practice. In approaching this chapter, we thought about what a new researcher would need to know about organic photovoltaic devices and materials in order to have a good start in the subject. Then, we simplified that to focus on what a new researcher would need to know about poly-3-hexylthiophene: phenyl-C61-butyric acid methyl ester blends (P3HT: PCBM) to make research progress with these materials. This chapter is by no means authoritative or a compendium of all things on P3HT: PCBM. We have selected to explain how the sample fabrication techniques lead to control of morphology and structural features and how these morphological features have specific optical and electronic consequences for organic photovoltaic device applications. KW - Free carrier generation KW - Non-geminate recombination KW - Organic solar cells Y1 - 2014 SN - 978-3-662-45145-8; 978-3-662-45144-1 U6 - https://doi.org/10.1007/12_2014_289 SN - 0065-3195 VL - 265 SP - 181 EP - 232 PB - Springer CY - Berlin ER - TY - JOUR A1 - Albrecht, Steve A1 - Grootoonk, Bjorn A1 - Neubert, Sebastian A1 - Roland, Steffen A1 - Wordenweber, Jan A1 - Meier, Matthias A1 - Schlatmann, Rutger A1 - Gordijn, Aad A1 - Neher, Dieter T1 - Efficient hybrid inorganic/organic tandem solar cells with tailored recombination contacts JF - Solar energy materials & solar cells : an international journal devoted to photovoltaic, photothermal, and photochemical solar energy conversion N2 - In this work, the authors present a 7.5% efficient hybrid tandem solar cell with the bottom cell made of amorphous silicon and a Si-PCPDTBT:PC70BM bulk heterojunction top cell. Loss-free recombination contacts were realized by combing Al-doped ZnO with either the conducting polymer composite PEDOT:PSS or with a bilayer of ultrathin Al and MoO3. Optimization of these contacts results in tandem cells with high fill factors of 70% and an open circuit voltage close to the sum of those of the sub-cells. This is the best efficiency reported for this type of hybrid tandem cell so far. Optical and electrical device modeling suggests that the efficiency can be increased to similar to 12% on combining a donor polymer with suitable absorption onset with PCBM. We also describe proof-of-principle studies employing light trapping in hybrid tandem solar cells, suggesting that this device architecture has the potential to achieve efficiencies well above 12%. (C) 2014 Elsevier B.V. All rights reserved. KW - Hybrid solar cells KW - Tandem solar cells KW - Organic solar cells KW - Bulk heterojunction KW - Efficiency optimization Y1 - 2014 U6 - https://doi.org/10.1016/j.solmat.2014.04.020 SN - 0927-0248 SN - 1879-3398 VL - 127 SP - 157 EP - 162 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Laquai, Frederic A1 - Andrienko, Denis A1 - Deibel, Carsten A1 - Neher, Dieter T1 - Charge carrier generation, recombination, and extraction in polymer-fullerene bulk heterojunction organic solar cells JF - Elementary processes in organic photovoltaics N2 - In this chapter we review the basic principles of photocurrent generation in bulk heterojunction organic solar cells, discuss the loss channels limiting their efficiency, and present case studies of several polymer-fullerene blends. Using steady-state and transient, optical, and electrooptical techniques, we create a precise picture of the fundamental processes that ultimately govern solar cell efficiency. KW - Charge extraction KW - Charge generation KW - Charge recombination KW - Organic solar cells KW - PBT7 KW - PBTTT KW - PCPDTBT Y1 - 2026 SN - 978-3-319-28338-8 SN - 978-3-319-28336-4 U6 - https://doi.org/10.1007/978-3-319-28338-8_11 SN - 0065-3195 VL - 272 SP - 267 EP - 291 PB - Springer CY - Berlin ER - TY - THES A1 - Hosseini, Seyed Mehrdad T1 - Non-Langevin Recombination in Fullerene and Non-Fullerene Acceptor Solar Cells T1 - Nicht-Langevin-Rekombination in Fulleren- und Nicht-Fulleren-Akzeptor-Solarzellen N2 - Organic solar cells (OSCs), in recent years, have shown high efficiencies through the development of novel non-fullerene acceptors (NFAs). Fullerene derivatives have been the centerpiece of the accepting materials used throughout organic photovoltaic (OPV) research. However, since 2015 novel NFAs have been a game-changer and have overtaken fullerenes. However, the current understanding of the properties of NFAs for OPV is still relatively limited and critical mechanisms defining the performance of OPVs are still topics of debate. In this thesis, attention is paid to understanding reduced-Langevin recombination with respect to the device physics properties of fullerene and non-fullerene systems. The work is comprised of four closely linked studies. The first is a detailed exploration of the fill factor (FF) expressed in terms of transport and recombination properties in a comparison of fullerene and non-fullerene acceptors. We investigated the key reason behind the reduced FF in the NFA (ITIC-based) devices which is faster non-geminate recombination relative to the fullerene (PCBM[70]-based) devices. This is then followed by a consideration of a newly synthesized NFA Y-series derivative which exhibits the highest power conversion efficiency for OSC at the time. Such that in the second study, we illustrated the role of disorder on the non-geminate recombination and charge extraction of thick NFA (Y6-based) devices. As a result, we enhanced the FF of thick PM6:Y6 by reducing the disorder which leads to suppressing the non-geminate recombination toward non-Langevin system. In the third work, we revealed the reason behind thickness independence of the short circuit current of PM6:Y6 devices, caused by the extraordinarily long diffusion length of Y6. The fourth study entails a broad comparison of a selection of fullerene and non-fullerene blends with respect to charge generation efficiency and recombination to unveil the importance of efficient charge generation for achieving reduced recombination. I employed transient measurements such as Time Delayed Collection Field (TDCF), Resistance dependent Photovoltage (RPV), and steady-state techniques such as Bias Assisted Charge Extraction (BACE), Temperature-Dependent Space Charge Limited Current (T-SCLC), Capacitance-Voltage (CV), and Photo-Induce Absorption (PIA), to analyze the OSCs. The outcomes in this thesis together draw a complex picture of multiple factors that affect reduced-Langevin recombination and thereby the FF and overall performance. This provides a suitable platform for identifying important parameters when designing new blend systems. As a result, we succeeded to improve the overall performance through enhancing the FF of thick NFA device by adjustment of the amount of the solvent additive in the active blend solution. It also highlights potentially critical gaps in the current experimental understanding of fundamental charge interaction and recombination dynamics. N2 - Organische Solarzellen (OSZ) haben in den letzten Jahren durch die Entwicklung neuartiger Nicht-Fulleren-Akzeptoren (NFA) hohe Wirkungsgrade erzielt. Fulleren-Derivate waren das Herzstück der Akzeptor-Materialien, die in der Forschung zur organischen Photovoltaik (OPV) verwendet wurden. Doch seit 2015 haben neuartige NFAs den Fullerenen den Rang abgelaufen. Allerdings ist das derzeitige Verständnis der Eigenschaften von NFA für OPV noch relativ begrenzt und kritische Mechanismen, die die Leistung von OPV bestimmen, sind immer noch Gegenstand von Diskussionen. In dieser Arbeit geht es um das Verständnis der Reduced-Langevin-Rekombination in Hinblick auf die bauteilphysikalischen Eigenschaften von Fulleren- und Nicht-Fulleren-Systemen. Die Arbeit besteht aus vier eng miteinander verbundenen Studien. Die erste ist eine detaillierte Untersuchung des Füllfaktors (FF), ausgedrückt als Transport- und Rekombinationseigenschaften in einem Vergleich von Fulleren und Nicht-Fulleren-Akzeptoren. Wir untersuchten den Hauptgrund für die geringere FF im NFA-Bauelement (auf ITIC-Basis), nämlich die schnellere nicht-geminate Rekombination im Vergleich zum Fulleren-Bauelement (auf PCBM[70]-Basis). Anschließend wird ein neu synthetisiertes NFA-Derivat der Y-Serie betrachtet, das derzeit die höchste Leistungsumwandlungseffizienz für OSZ aufweist. In der zweiten Studie veranschaulichten wir die Rolle der Unordnung bei der nicht-geminaten Rekombination und der Ladungsextraktion von dicken NFA-Bauelementen (auf Y6-Basis). Infolgedessen haben wir die FF von dickem PM6:Y6 verbessert, indem wir die Unordnung reduziert haben, was zur Unterdrückung der nicht-geminaten Rekombination in Richtung Nicht-Langevin-System führt. In der dritten Arbeit haben wir den Grund für die Dickenunabhängigkeit des Kurzschlussstroms von NFA-Bauelementen aufgedeckt, die durch die außerordentlich lange Diffusionslänge von Y6 verursacht wird. Die vierte Studie umfasst einen umfassenden Vergleich einer Auswahl von Fulleren- und Nicht-Fulleren-Mischungen in Hinblick auf die Effizienz der Ladungserzeugung und Rekombination, um die Bedeutung einer effizienten Ladungserzeugung zum Erzielen einer geringeren Rekombination aufzuzeigen. Zur Analyse der OSCs habe ich transiente Messungen wie das Time Delayed Collection Field (TDCF), Resistance dependent Photovoltage (RPV) sowie stationäre Techniken wie die Bias Assisted Charge Extraction (BACE), Temperature-Dependent Space Charge Limited Current (T-SCLC), Capacitance-Voltage (CV) und Photo-Induce Absorption (PIA) eingesetzt. Die Ergebnisse dieser Arbeit zeichnen ein komplexes Bild zahlreicher Faktoren, die die Rekombination nach dem Prinzip des reduzierten Langèvins und damit die FF und die Gesamtleistung beeinflussen. Dies bietet eine geeignete Plattform zum Identifizieren wichtiger Parameter bei der Entwicklung neuer Mischsysteme. So ist es uns gelungen, die Gesamtleistung zu verbessern, indem wir die FF der dicken NFA-Vorrichtung durch Anpassung der Menge des Lösungsmittelzusatzes in der aktiven Mischungslösung erhöht haben. Außerdem werden potenziell kritische Lücken im derzeitigen experimentellen Verständnis der grundlegenden Ladungswechselwirkung und Rekombinationsdynamik aufgezeigt. KW - Organic solar cells KW - Non-fullerene acceptors KW - Charge recombination KW - Non-Langevin systems KW - Structural and energetic disorder KW - Ladungsrekombination KW - Nicht-Langevin-Systeme KW - Nicht-Fulleren-Akzeptoren KW - Organische Solarzellen KW - Strukturelle und energetische Unordnung Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-547831 ER -