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.