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

Inorganic CsPbI 2 Br 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 CsPbI 2 Br films hinder the progress in enhancing the power conversion efficiency (PCE). Herein, we put forward facile acetate-assisted buried interface engineering to passivate TiO 2 /perovskite interface defects along with regulate the crystallization process of CsPbI 2 Br. Multifunctional small molecule interface modifier zinc acetate (Zn(Ac) 2 ) is introduced into the surface of TiO 2 ETL, which can passivate the oxygen vacancy defects of TiO 2 and optimize the energy level alignment at the TiO 2 /CsPbI 2 Br interface. Meanwhile, part of Ac – may be dissolved in the CsPbI 2 Br precursor to retard its nucleation process, leading to enhanced crystallinity with a larger grain size of the CsPbI 2 Br film. As a result, reduced interface defects and bulk defects as well as enhanced electron extraction are achieved, which substantially enhance the PCE of CsPbI 2 Br 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.