Enhancing perovskite quality and energy level alignment of TiO2 nanorod arrays-based solar cells via interfacial modification

The perovskite quality and energy level alignment are critical for achieving high-performance and stability perovskite solar cells (PSCs). In this work, ultrathin anatase TiO2 were in-situ deposited on rutile TiO2 nanorod arrays (NM) by a room-temperature solution method, contributing to form Type-II band alignment and accelerate interfacial charge transfer in PSCs. Then, a self-assembled monolayer (SAM) of N-[3-(Trimethoxysilyl) propyl]ethylenediamine was grafted on the surface of rutile@anatase TiO2 coaxial NM (TCNAs). Interestingly, the power conversion efficiency (PCE) of PSCs was significantly improved to 14.89%, compared to 11.8% of the pristine TCNAs-based devices. The results indicate that the SAM controls the TiO2 surface wettability to improve the morphology and crystallinity of the following deposited perovskite layers. Moreover, the electric dipoles from the SAM increase the Fermi level of TiO2 for further enhancing the energy level alignment with perovskite layers to improve the interfacial charge transfer.