Degradation Mechanism of Perovskite under High Charge Carrier Density Condition

Extensive studies have focused on degradation of perovskite at low charge carrier density (<10^16 cm^-3), but few have surveyed the degradation mechanism at high charge carrier density (~10^18 cm^-3). Here, we investigate the degradation mechanisms of perovskite under high charge carrier conditions. Unlike the observations in previous works, we find that MAPbI3 degradation starts at surface defects and progressing from the surface defects towards neighboring regions under high charge carrier density condition. By using PbI2 passivation, the defect-initiated degradation is significantly suppressed and the nanoplatelet degrades in a layer-by-layer way, enabling the MAPbI3 laser sustain for 4500 s (2.7*10^7 pulses), which is almost 3 times longer than that of the nanoplatelet laser without passivation. Meanwhile, the PbI2 passivated MAPbI3 nanoplatelet laser with the nanoplatelet cavity displaying a maximum quality factor up to ~7800, the highest reported for all MAPbI3 nanoplatelet cavities. Furthermore, a high stability MAPbI3 nanoplatelet laser that can last for 8500 s (5.1*10^7 pulses) is demonstrated based on a dual passivation strategy, by retarding the defect-initiated degradation and surface-initiated degradation, simultaneously. This work provides in-depth insights for understanding the degradation of perovskite at high charge carrier density.