Small-Molecule Targeting of Defect Passivation in All-Inorganic Carbon-Based Perovskite Solar Cells

The fast-track development in all-inorganic perovskite photovoltaics for high efficiency are still facing the defect issues including vacancy, undercoordinated ions, and dislocation at the surface/interface of perovskite materials. Herein, three kinds of small-molecules difluorobenzylamine (DFBA) are found to act as the interfacial modification materials to stabilize and enhance the efficiency of all-inorganic carbon perovskite CsPbI3-xBrx solar cell. The fluorine atoms with different positions in the benzene ring are demonstrated by the density-functional theory simulations and experiments to passivate the defect at the surface/interface of perovskites, boosting the photocarrier transfer. Accordingly, the most suitable 2,6-DFBA is used to modify the perovskite to prepare hole-transporting materials-free carbon-based CsPbI3-xBrx (X = 0.3) perovskite solar cells, and the interface-modified device yields a power conversion efficiency (PCE) of 14.6%, the open-circuit voltage is increased to 1.14 V, and the PCE of the unpackaged device remained at 92% of the initial PCE after 1680 h of storage at 20-30% air humidity.