Defect passivation of grain surface toward perovskite solar cells with a high open-circuit voltage exceeding 1.16 V

Organic–inorganic lead halide perovskites have attracted great interest as low-cost and high efficiency solar cells. However, the excessive surface defects of perovskite crystal grains are still a crucial factor that limits further improvement in the performance of corresponding devices. Here, we introduce potassium chloride (KCl) into the precursor of a triple A-cation mixed-halide perovskite to passivate the surface defects and provide an insight into the underlying passivation mechanism of this common salt. We reveal that KCl exists on the surface of perovskite grains, suppressing the grain surface defects and modulating the energy level alignment of the perovskite solar cell (PSC). KCl added PSCs achieved a high open circuit voltage of 1.162 V compared with that of a control device (1.087 V), due to suppressed non-radiative recombination losses. Our work investigates the synergetic effect of K⁺ and Cl⁻ on the enhancement of the device performance and provides an effective strategy of defect passivation toward highly efficient perovskite solar cells.