Recycling Single‐Crystal Perovskite Solar Cells With Improved Efficiency and Stability

Abstract Metal halide perovskite single crystals are promising for photovoltaic applications due to their outstanding properties. However, the high surface trap density causes severe nonradiative recombination and ion migration, hindering device performance and stability. Herein, mitigation of the deficient crystal surface is reported by optimized polishing engineering, resulting in stoichiometric lead‐iodine ratio with reduced iodide ion vacancies, increased ion migration activation energy, and suppressed nonradiative recombination. As a result, Cs 0.05 FA 0.95 PbI 3 (FA = formamidinium) devices exhibit an impressive efficiency of 23.1%, which is one of the highest values for single‐crystal perovskite solar cells (PSCs). Moreover, multiple recycling of the degraded single‐crystal PSCs with higher efficiency and stability is achieved by removing the deteriorated surface, validating crystal surface dominates device degradation while the role of bulk and buried interface is negligible, which is different from polycrystalline devices. The T85 lifetime (remain 85% of initial efficiency) of Cs 0.05 FA 0.95 PbI 3 devices increases to 1150 h after the recycling process, which is much better than that of previously reported single‐crystal PSCs. Since deficient crystal surface and ion migration are universal issues of perovskite materials, this work will promote the development of stable single‐crystal PSCs and other optoelectronic devices, such as X‐ray detectors, light‐emitting diodes, etc.