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 - Roland, Steffen A1 - Kniepert, Juliane A1 - Love, John A. A1 - Negi, Vikas A1 - Liu, Feilong A1 - Bobbert, Peter A1 - Melianas, Armantas A1 - Kemerink, Martijn A1 - Hofacker, Andreas A1 - Neher, Dieter T1 - Equilibrated Charge Carrier Populations Govern Steady-State Nongeminate Recombination in Disordered Organic Solar Cells JF - The journal of physical chemistry letters N2 - We employed bias-assisted charge extraction techniques to investigate the transient and steady-state recombination of photogenerated charge carriers in complete devices of a disordered polymer-fullerene blend. Charge recombination is shown to be dispersive, with a significant slowdown of the recombination rate over time, consistent with the results from kinetic Monte Carlo simulations. Surprisingly, our experiments reveal little to no contributions from early time recombination of nonequilibrated charge carriers to the steady-state recombination properties. We conclude that energetic relaxation of photogenerated carriers outpaces any significant nongeminate recombination under application-relevant illumination conditions. With equilibrated charges dominating the steady-state recombination, quasi-equilibrium concepts appear suited for describing the open-circuit voltage of organic solar cells despite pronounced energetic disorder. Y1 - 2019 U6 - https://doi.org/10.1021/acs.jpclett.9b00516 SN - 1948-7185 VL - 10 IS - 6 SP - 1374 EP - 1381 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Zapata-Arteaga, Osnat A1 - Marina, Sara A1 - Zuo, Guangzheng A1 - Xu, Kai A1 - Dörling, Bernhard A1 - Alberto Pérez, Luis A1 - Sebastián Reparaz, Juan A1 - Martín, Jaime A1 - Kemerink, Martijn A1 - Campoy-Quiles, Mariano T1 - Design rules for polymer blends with high thermoelectric performance JF - Advanced energy materials N2 - A combinatorial study of the effect of in-mixing of various guests on the thermoelectric properties of the host workhorse polymer poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT) is presented. Specifically, the composition and thickness for doped films of PBTTT blended with different polymers are varied. Some blends at guest weight fractions around 10-15% exhibit up to a fivefold increase in power factor compared to the reference material, leading to zT values around 0.1. Spectroscopic analysis of the charge-transfer species, structural characterization using grazing-incidence wide-angle X-ray scattering, differential scanning calorimetry, Raman, and atomic force microscopy, and Monte Carlo simulations are employed to determine that the key to improved performance is for the guest to promote long-range electrical connectivity and low disorder, together with similar highest occupied molecular orbital levels for both materials in order to ensure electronic connectivity are combined. KW - doping KW - microstructure KW - organic thermoelectrics KW - orientation KW - ternary Y1 - 2022 U6 - https://doi.org/10.1002/aenm.202104076 SN - 1614-6832 SN - 1614-6840 VL - 12 IS - 19 PB - Wiley CY - Weinheim ER -