Precise Control of Crystal Growth for Highly Efficient CsPbI2Br Perovskite Solar Cells

All-inorganic perovskite solar cells (pero-SCs) are attracting considerable attention due to their promising thermal stability, but their inferior power-conversion efficiency (PCE) and moisture instability are hindering their application. Here, we used a gradient thermal annealing (GTA) method to control the growth of alpha-CsPbI2Br crystals and then utilized a green anti-solvent (ATS) isopropanol to further optimize the morphology of alpha-CsPbI2Br film. Through this GTA-ATS synergetic effect, the growth of alpha-CsPbI2Br crystals could be precisely controlled, leading to a high-quality perovskite film with one-micron average grain size, low root-mean-square of 25.9 nm, and reduced defect density. Pero-SCs based on this CsPbI2Br film achieved a champion scan PCE of 16.07% (stabilized efficiency of 15.75%), which is the highest efficiency reported in all-inorganic pero-SCs. Moreover, the CsPbI2Br pero-SC demonstrates excellent robustness against moisture and oxygen, and maintains 90% of initial PCE after aging 120 hr under 100 mW/cm(2) UV irradiation.