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Hybrid organic–inorganic perovskite solar cells (PSCs) have attracted great interest owing to their low fabrication costs and high power conversion efficiency. Most studies have focused on the devices with methylammonium lead trihalide perovskites. Here, we explore a new perovskite with mixed organic cations and mixed halides, MA1−xFAxPbI3−yCly. MA1−xFAxPbI3−yCly films can be fabricated by annealing at a temperature of 80–110 °C. Planar heterojunction PSCs using this perovskite as the active material can exhibit a high power conversion efficiency (PCE) of up to 18.14% with short-circuit photocurrent density (Jsc) of 21.55 ± 0.55 mA cm−2, open-circuit voltage (Voc) of 1.100 ± 0.010 V, and fill factor (FF) of 0.75 ± 0.02. The PCE is much higher than those of the control devices with other commonly employed perovskites including MAPbI3, MAPbI3−yCly, MAPbI3−yBry, and MA1−xFAxPbI3. The superior performance is mainly attributed to the enhancement of Jsc, which is a result of long charge diffusion lengths due to the presence of mixed organic cations and mixed halides. In addition, there is no obvious hysteresis in the J–V curves along the forward and reverse scan directions. The formation of undesirable δ-phase perovskite that has a band gap of 2.8 eV is not observed in the MA1−xFAxPbI3−yCly films. These findings pave the way for the design of new hybrid perovskites with stronger light absorption over a wide range, lower charge recombination, and improved charge transport properties through compositional engineering. [ABSTRACT FROM AUTHOR]

The determination of molecular conformations of oligomeric acceptors (OAs) and their impact on molecular packing are crucial for understanding the photovoltaic performance of their resulting polymer solar cells (PSCs) but have not been well studied yet. Herein, we synthesized two dimeric acceptor materials, DIBP3F-Se and DIBP3F-S, which bridged two segments of Y6-derivatives by selenophene and thiophene, respectively. Theoretical simulation and experimental 1D and 2D NMR spectroscopic studies prove that both dimers exhibit O-shaped conformations other than S- or U-shaped counter-ones. Notably, this O-shaped conformation is likely governed by a distinctive "conformational lock" mechanism, arising from the intensified intramolecular π-π interactions among their two terminal groups within the dimers. PSCs based on DIBP3F-Se deliver a maximum efficiency of 18.09 %, outperforming DIBP3F-S-based cells (16.11 %) and ranking among the highest efficiencies for OA-based PSCs. This work demonstrates a facile method to obtain OA conformations and highlights the potential of dimeric acceptors for high-performance PSCs., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

It is very important to study the crystallization of hybrid organic-inorganic perovskites because their thin films are usually prepared from solution. The investigation on the growth of perovskite films is however limited by their polycrystallinity. In this work, methylammonium lead triiodide single crystals grown from solutions with different methylammonium iodide (MAI):lead iodide (PbI 2 ) ratios were investigated. We observed a V-shaped dependence of the crystallization onset temperature on the MAI:PbI 2 ratio. This is attributed to the MAI effects on the supersaturation of precursors and the interfacial energy of the crystal growth. At low MAI:PbI 2 ratio (<1.7), more MAI leads to the supersaturation of the precursors at lower temperature. At high MAI:PbI 2 ratio, the crystal growing plans change from (100)-plane dominated to (001)-plane dominated. The latter have higher interfacial energy than the former, leading to a higher crystallization onset temperature., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)