Polymer-Passivated Inorganic Cesium Lead Halide Perovskites for High-Voltage and High-Efficiency Solar Cells

Abstract

Cesium-based trihalide perovskites have been demonstrated as promising light absorbers for photovoltaic applications due to its superb thermal stability. However, the large energy losses (Eloss) in the conversion from photons to electrons observed in many inorganic perovskite solar cells has become a major hindrance impairing the ultimate efficiency of these devices. Here, we report an effective and reproducible method of modifying the interface between a CsPbI2Br absorber and polythiophene hole-acceptor to minimize the Eloss. We demonstrate that polythiophene, deposited on the top of CsPbI2Br, can significantly reduce electron-hole recombination within the perovskite, which is due to the electronic passivation of surface defect states. In addition, the interfacial properties are improved by a simple annealing process, leading to significantly reduced energy disorder in polythiophene and enhanced hole-injection into the hole-acceptor. Consequently, a record power conversion efficiency (PCE) of 12.09% in inorganic perovskite solar cells is obtained, together with a high open-circuit voltage (VOC) over 1.3 V, under 100 mWcm-2 AM1.5G solar illumination. This method provides a new route to further improve the efficiency of perovskite solar cells by minimizing the Eloss.