A multifunctional interlayer between mesoporous TiO₂ and perovskite for perovskite solar cells with high efficiency and stability

Abstract The industrialization of the perovskite solar cells (PSCs) requires further lifting their power conversion efficiency (PCE). There are some important factors to hinder the PCE improvement, such as interface defects and energy level mismatching betwee electron transport layer (ETL) and perovskite layer, and solar energy loss due to no absorption of near infrared (NIR) for the perovsktie. Thus in this study, a multifunctional material of W-Er-Yb doped TiO 2 (W-UC-TiO 2 ) was prepared and applied to PSCs as an interlayer between mesoporous TiO 2 and perovskite. The experimental results demonstrate that the interlayer of W-UC-TiO 2 has the functions of improving NIR absorption for PSCs, passivating inerface defects and improving energy level matching between TiO 2 and perovskite. A high efficiency of 21.32% was acquired for the PSCs with W-UC-TiO 2 interlayer from 19.26% for the control device. Moreover, stability of the PSCs was improved by the insertion of W-UC-TiO 2 interlayer.