Acetate-Assisted Buried Interface Engineering for Highly Efficient Carbon-Based CsPbI₂Br Perovskite Solar Cells

Inorganic CsPbI₂Br carbon-based perovskite solar cells (C-PSCs) are considered as an alternative promising contender in the field of photovoltaics, attributed to their remarkable thermal stability and cost-effectiveness. However, the defects located at the electron transporting layer (ETL)/perovskite interface (i.e., buried interface) and unsatisfactory crystallinity of CsPbI₂Br films hinder the progress in enhancing the power conversion efficiency (PCE). Herein, we put forward facile acetate-assisted buried interface engineering to passivate TiO₂/perovskite interface defects along with regulate the crystallization process of CsPbI₂Br. Multifunctional small molecule interface modifier zinc acetate (Zn(Ac)₂) is introduced into the surface of TiO₂ ETL, which can passivate the oxygen vacancy defects of TiO₂ and optimize the energy level alignment at the TiO₂/CsPbI₂Br interface. Meanwhile, part of Ac^- may be dissolved in the CsPbI₂Br precursor to retard its nucleation process, leading to enhanced crystallinity with a larger grain size of the CsPbI₂Br film. As a result, reduced interface defects and bulk defects as well as enhanced electron extraction are achieved, which substantially enhance the PCE of CsPbI₂Br C-PSCs from 12.54% to 14.20%, among the highest values of this type of device. Besides, thermal and long-term storage stabilities of the optimized devices are improved.