Low-temperature growth of uniform ultrathin TiO2 blocking layer for efficient perovskite solar cell

Although chemical bath of TiCl4 treatment has been used to serve as a compact layer for planar perovskite solar cells (PSCs), uneven TiO2 particle sizes and chlorine residual would decrease the device performance. In this study, we modify the TiCl4 treatment process through well-controlled the kinetics grown of TiO2 nanoparticle, leading to a uniform and ultrathin TiO2 blocking layer. A dense and pinholeless TiO2 blocking layer is crucial for high-performance PSCs because of its effective charge extraction and elimination of carrier shunting path. The as-fabricated devices using modified process of TiO2 blocking layer exhibit the best power conversion efficiency (PCE) of 17.89% with an average PCE of 17.5%. Scanning electron microscopy and cyclic voltammetry analysis of TiO2 blocking layer reveal that this process improved surface uniformity and the carrier blocking capability.