Highly Efficient Flexible Perovskite Solar Cells through Pentylammonium Acetate Modification with certified efficiency of 23.35.

Among the emerging photovoltaic technologies, rigid perovskite solar cells (PSCs) have made tremendous development owing to their exceptional power conversion efficiency (PCE) of up to 25.7%. However, the record PCE of flexible PSCs (∼22.4%) still lags far behind their rigid counterparts and their mechanical stabilities are also not satisfactory. Herein, we report a highly efficient and stable flexible inverted PSC through modifying the interface between perovskite and hole transport layer (HTL) via Pentylammonium Acetate (PenAAc) molecule. Through synthetic manipulation of anion and cation, we show that the PenA + and Ac- have strong chemical binding with both acceptor and donor defects of surface-terminating ends on perovskite films. The PenAAc modified flexible PSCs achieved a record PCE of 23.68% (0.08 cm 2 , certified: 23.35%) with a high open-circuit voltage (V OC ) of 1.17 V. Large-area devices (1.0 cm 2 ) also realized an exceptional PCE of 21.52%. Moreover, the fabricated devices showed excellent stability under mechanical bending, with PCE remaining above 91% of the original PCE even after 5000 bends. This article is protected by copyright. All rights reserved.