Vapor phase deposition of Pb-free inorganic perovskite films

초록

Metal halide perovskites (MHPs) have recently emerged as highly attractive materials for next-generation photovoltaics, largely due to their excellent optoelectronic properties and rapidly improving power conversion efficiency (PCE). However, the toxicity of lead-based perovskites presents a significant challenge to their commercialization. In response to this challenge, tin (Sn)-based MHPs have been extensively studied as a promising alternative, owing to the similarity of Sn with Pb in terms of the ionic radius and oxidation states while possessing reduced toxicity and environmental pollution. However, the optoelectronic performance of Sn-based MHPs is generally inferior to their Pb counterparts due to their chemical instability, which can result in Sn vacancy caused by oxidation, particularly under solution-based film deposition processes. In this study, we propose a novel approach to enhance the stability and performance of Sn-based MHP thin films through the vapor phase deposition method. We co-evaporated an additive, SnF2, with precursors (CsBr and SnBr2) to deposit CsSnBr3 thin films on the substrate. We confirmed that the nucleation and growth of CsSnBr3 films is critically affected by the SnF2. By controlling the amount of SnF2, we obtained an optimized perovskite film with improved morphology and free from holes. Our results shed light on the vapor-based perovskite film deposition to fabricate solar cells with improved efficiency by promoting perfect contact between the electron transport layer (ETL) and hole transport layer (HTL) of the device. Overall, this study demonstrates a promising method for improving the performance and stability of Sn-based MHP solar cells, which could contribute to the development of environmentally friendly and efficient photovoltaic devices.