Healing soft interface for stable and high-efficiency all-inorganic CsPbIBr2 perovskite solar cells enabled by S-benzylisothiourea hydrochloride

Interfacial regulation to heal the soft lattice induced defective nanostructured surfaces of perovskite films plays a crucial role in determining the stability and efficiency of perovskite solar cells (PSCs). Herein, we report a facile method to strengthen and passivate the inorganic PbI2-excess CsPbIBr2 surface with a multifunctional S-benzylisothiourea hydrochloride (SBTCl), which not only significantly reduces the detrimental defects through interaction between electron-donating groups and defects (as well as Cl doping as lattice "glue") but also enables straightway unobstructed hole extraction and transfer arising from the reduced work function. Consequently, a higher efficiency of 10.56% with an open-circuit voltage of 1.327 V than control device with 7.72%-efficiency is obtained for inorganic CsPbIBr2 PSC free of hole transporting material, which is one cutting-edge value in this kind of PSC. In addition, the high hydrophobicity of SBTCl passivator hinders the permeation of moisture into perovskite film, resulting in improved long-term air-stability after storage in 5% relative humidity (RH) without encapsulation over 110 days and persistent light irradiation over 16 h in 50% RH condition.