Single-Crystal Methylammonium-Free Perovskite Solar Cells with Efficiencies Exceeding 24% and High Thermal Stability

Grain-free single-crystal perovskites offer a potential avenue to the stability of advance perovskite solar cells (PSCs) beyond that of polycrystalline films. Recent progress in single-crystal PSCs (SC-PSCs) has come primarily from methylammonium (MA)-containing (e.g., FA(0.6)MA(0.4)PbI(3)) perovskite devices, which have achieved a 23.1% power conversion efficiency (PCE). Yet, such perovskites are intrinsically vulnerable to thermal stresses, given the relative volatility of the MA molecule within the perovskite structure. Herein, we demonstrate MA-free SC-PSCs based on an similar to 20-mu m-thick Cs(0.05)FA(0.95)PbI(3) single-crystal absorber layer, which achieves new stability and efficiency benchmarks for SC-PSCs. Our devices exhibit 24.29% PCE and retain 90% of their initial efficiency after 900 h at 53 degrees C. Accelerated aging tests on the Cs(0.05)FA(0.95)PbI(3) single crystals show that they endured the damp heat test (85 degrees C/65% RH) approximately twice as long as polycrystalline films of the same composition. These results indicate that MA-free FAPbI(3)-based SCs are promising candidates to develop the stability and efficiency of PSCs on the road to commercialization.