TY - JOUR A1 - Perdigon-Toro, Lorena A1 - Zhang, Huotian A1 - Markina, Anastaa si A1 - Yuan, Jun A1 - Hosseini, Seyed Mehrdad A1 - Wolff, Christian Michael A1 - Zuo, Guangzheng A1 - Stolterfoht, Martin A1 - Zou, Yingping A1 - Gao, Feng A1 - Andrienko, Denis A1 - Shoaee, Safa A1 - Neher, Dieter T1 - Barrierless free charge generation in the high-performance PM6:Y6 bulk heterojunction non-fullerene solar cell JF - Advanced materials N2 - Organic solar cells are currently experiencing a second golden age thanks to the development of novel non-fullerene acceptors (NFAs). Surprisingly, some of these blends exhibit high efficiencies despite a low energy offset at the heterojunction. Herein, free charge generation in the high-performance blend of the donor polymer PM6 with the NFA Y6 is thoroughly investigated as a function of internal field, temperature and excitation energy. Results show that photocurrent generation is essentially barrierless with near-unity efficiency, regardless of excitation energy. Efficient charge separation is maintained over a wide temperature range, down to 100 K, despite the small driving force for charge generation. Studies on a blend with a low concentration of the NFA, measurements of the energetic disorder, and theoretical modeling suggest that CT state dissociation is assisted by the electrostatic interfacial field which for Y6 is large enough to compensate the Coulomb dissociation barrier. KW - driving force KW - non-fullerene acceptors KW - organic solar cells KW - photocurrent generation Y1 - 2020 U6 - https://doi.org/10.1002/adma.201906763 SN - 0935-9648 SN - 1521-4095 VL - 32 IS - 9 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Zuo, Guangzheng A1 - Shoaee, Safa A1 - Kemerink, Martijn A1 - Neher, Dieter T1 - General rules for the impact of energetic disorder and mobility on nongeminate recombination in phase-separated organic solar cells JF - Physical review applied N2 - State-of-the-art organic solar cells exhibit power conversion efficiencies of 18% and above. These devices benefit from the suppression of free charge recombination with regard to the Langevin limit of charge encounter in a homogeneous medium. It is recognized that the main cause of suppressed free charge recombination is the reformation and resplitting of charge-transfer (CT) states at the interface between donor and acceptor domains. Here, we use kinetic Monte Carlo simulations to understand the interplay between free charge motion and recombination in an energetically disordered phase-separated donor-acceptor blend. We identify conditions for encounter-dominated and resplitting-dominated recombination. In the former regime, recombination is proportional to mobility for all parameters tested and only slightly reduced with respect to the Langevin limit. In contrast, mobility is not the decisive parameter that determines the nongeminate recombination coefficient, k(2), in the latter case, where k2 is a sole function of the morphology, CT and charge-separated (CS) energetics, and CT-state decay properties. Our simulations also show that free charge encounter in the phase-separated disordered blend is determined by the average mobility of all carriers, while CT reformation and resplitting involves mostly states near the transport energy. Therefore, charge encounter is more affected by increased disorder than the resplitting of the CT state. As a consequence, for a given mobility, larger energetic disorder, in combination with a higher hopping rate, is preferred. These findings have implications for the understanding of suppressed recombination in solar cells with nonfullerene acceptors, which are known to exhibit lower energetic disorder than that of fullerenes. Y1 - 2021 U6 - https://doi.org/10.1103/PhysRevApplied.16.034027 SN - 2331-7019 VL - 16 IS - 3 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Wang, Suhao A1 - Zuo, Guangzheng A1 - Kim, Jongho A1 - Sirringhaus, Henning T1 - Progress of Conjugated Polymers as Emerging Thermoelectric Materials JF - Progress in polymer science N2 - Thanks to the combined effort s of scientist s in several research fields, the preceding decade has witnessed considerable progress in the use of conjugated polymers as emerging thermoelectric materials leading to significant improvements in performance and demonstration of a number of diverse applications. Despite these recent advances, systematic assessments of the impact of molecular design on thermoelectric properties are scarce. Although several reviews marginally highlight the role of chemical structure, the understanding of structure-performance relationships is still fragmented. An in-depth understanding of the relationship between molecular structure and thermoelectric properties will enable the rational design of next-generation thermoelectric polymers. To this end, this review showcases the state-of-the-art thermoelectric polymers, discusses structure-performance relationships, suggests strategies for improving thermoelectric performance that go beyond molecular design, and highlights some of the most impressive applications of thermoelectric polymers. KW - Organic thermoelectrics KW - Seebeck coefficient KW - Doping KW - Polaron KW - Conducting polymers KW - Structure-performance relationship Y1 - 2022 U6 - https://doi.org/10.1016/j.progpolymsci.2022.101548 SN - 0079-6700 SN - 1873-1619 VL - 129 PB - Elsevier CY - Oxford ER -