Hole-Transporting Organic Salt Induced Surface-2D/Bulk-3D Hierarchy Perovskite for Efficient and Stable Photovoltaic Devices

Here, we report a novel hole-transporting organic salt (HTOS) based on (4'-(bis(4-methoxyphenyl)amino)-[1,1'-biphenyl]-4-yl)methanaminium bromide, which facilely forms a hole-transporting 2D perovskite on the top surface of 3D perovskite via a spin-coating procedure. This capping 2D perovskite can significantly reduce interface trap densities and enhance hole-extracting abilities of heterojunction region between 3D perovskite and hole-transporting layer (HTL), owing to its spatially and potentially confined hole-charge carriers, simultaneously. This interfacial HTOS induced 2D perovskite can effectively suppress nonradiative recombination, which leads to an increase in the photovoltage of perovskite solar cells (PSC) to more than 1.20 V. As a result, the n-i-p planar PSC can achieve a champion power conversion efficiency of 20.71% as well as excellent operational stability exhibiting 92% of initial efficiency after 500 h continuous illumination without encapsulation. This work provides a facile approach to fabricate hole-transporting surface-2D and light-harvesting bulk-3D hierarchy perovskite structure, which delivers significantly enhanced efficiency and stability of PSCs.