Stabilizing Perovskite/Electrode Interface With Tailored 2D/1D Stacking Layer.

Metal halide perovskite (MHP) single crystals are promising for optoelectronic applications, yet their surfaces suffer from severe ion migration-related degradation. Herein, a 2D/1D stacking layer is explored to stabilize the crystal/electrode interface. In addition to providing a dense barrier layer, the inserted 2D perovskites can modulate the microscopic morphology and coverage ratio of the overlying 1D perovskite layer. Through tailoring the 2D/1D stacking layer, interface iodide migration is suppressed markedly, extending the T90 lifetime of single-crystal perovskite solar cells (PSCs) from 450 h to 2500 h, which significantly exceeds previously reported values. Besides, the reverse-bias-induced performance decay can be recovered substantially, indicating effective hindrance of irreversible iodide ion migration across the perovskite/electrode interface. Finally, the surface iodide vacancies and nonradiative recombination loss are mitigated, increasing the power conversion efficiency (PCE) from 23.2% to 25.5%, which is among the highest value for single-crystal PSCs. Since interface ion migration is a universal issue for both polycrystalline films and single crystals, our strategy is instructive for optimizing diverse perovskite optoelectronic devices.