Highly stable inverted methylammonium lead tri-iodide perovskite solar cells achieved by surface re-crystallization

Despite the promise of simple manufacturing via an entirely solution-based process at low temperature (<100 °C), the planar-type inverted perovskite solar cells (PeSCs) based on methylammonium lead tri-iodide (MAPbI₃) still suffer from a notorious instability problem under operational conditions. Here, we found that the operational stability of PeSCs with MAPbI₃ is significantly related to a high density of ionic defects and correlated amorphous regions at the interface between the electron transport layer and the MAPbI₃ film. By recrystallizing the surface of the MAPbI₃ layer, we fabricate defect-free stoichiometric MAPbI₃ crystals and demonstrated burn-in loss-free and intrinsically stable inverted MAPbI₃ PeSCs. The inverted MAPbI₃ PeSCs exhibited a power conversion efficiency (PCE) of 18.8% and maintained over 80% and 90% of their initial PCEs even after 1000 hours of real operation (under AM 1.5G irradiation) and continuous heating conditions (at 85 °C in the dark), respectively. Our work demonstrates that the MAPbI₃ layer under ionic defect-free conditions is 'intrinsically' stable under operational conditions.