High-Performance and Stable Mesoporous Perovskite Solar Cells via Well-Crystallized FA_0.85MA_0.15Pb(I_0.8Br_0.2)₃

The overall performance of perovskite solar cells (PSCs) depends particularly on the chemical composition and crystalline quality of the perovskite light harvester. Here, the well-crystallized mixed-cation lead mixed-halide perovskite films with the optimized composition of FA0.85MA0.15Pb(I0.8Br0.2)3 were achieved by antisolvent-assisted single-step spin-coating in ambient conditions. The resulting PSCs with the well-crystallized FA0.85MA0.15Pb(I0.8Br0.2)3 exhibit impressive power conversion efficiency (PCE) over 20% under standard AM 1.5 illumination with excellent reproducibility. Remarkably, no perceivable degradation in PCE was detected from the PSCs stored in ambient conditions without any encapsulation after 7000 h (nearly 300 days), which was among the best shelf stability ever reported for PSCs. The superior performance was mainly attributed to the improved structural quality of the FA0.85MA0.15Pb(I0.8Br0.2)3 layer with reduced grain boundaries, reduced trap-state density, and prolonged carrier lifetime, as well as the better intrinsic stability of the mixed perovskite with an optimized composition.