Bulk and interface passivation through potassium iodide additives engineering enables high-performance and humidity-stable CsPbBr 3 perovskite solar cells

Organic -inorganic hybrid perovskite solar cells (PSCs) have gained significant attention in the past decade due to their exceptional photovoltaic performance and unique advantages. However, the organic cation component of the hybrid perovskites results in poor humidity resistibility and thermal stability. Replacing organic cations with inorganic cations, such as Cs + , to fabricate all -inorganic CsPbX 3 PSCs, is an effective way to improve their stability. Among the CsPbX 3 PSCs, full-brominated CsPbBr 3 PSCs have excellent moisture and thermal tolerance, with great potential for commercialization. However, these PSCs suffer from energy loss during operation, and their photoelectric conversion efficiency is lower than that of mainstream hybrid PSCs. Additive engineering is an effective method to improve the quality of perovskite films, which introduces functional additives into the perovskite precursor to induce perovskite crystallization, achieve the passivation of uncoordinated ions defects, and finely tune the energy level structures. In this study, Potassium iodide (KI) was added to the CsBr precursor solution to participate in the formation of the CsPbBr 3 perovskite thin film. The partial substitution of A -site cation in the ABX 3 perovskite occurred during the film formation, leading to beneficial variation of the crystal structure and photoelectronic performance in the CsPbBr 3 system. The planar -architecture device based on the modified CsPbBr 3 layer could reach a best efficiency of 10.06 %, together with a high open -circuit voltage ( V oc ) of 1.60 V. The KI-doped CsPbBr 3 based PSC can retain over 90 % of the original PCE even after 30 days of aging, thanks to the diminished defect density by the KI passivation.