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 degrees C), the planar-type inverted perovskite solar cells (PeSCs) based on methylammonium lead tri-iodide (MAPbI(3)) still suffer from a notorious instability problem under operational conditions. Here, we found that the operational stability of PeSCs with MAPbI(3) is significantly related to a high density of ionic defects and correlated amorphous regions at the interface between the electron transport layer and the MAPbI(3) film. By recrystallizing the surface of the MAPbI(3) layer, we fabricate defect-free stoichiometric MAPbI(3) crystals and demonstrated burn-in loss-free and intrinsically stable inverted MAPbI(3) PeSCs. The inverted MAPbI(3) 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 degrees C in the dark), respectively. Our work demonstrates that the MAPbI(3) layer under ionic defect-free conditions is 'intrinsically' stable under operational conditions.