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.