SCHEDULED MAINTENANCE
Revealing superoxide-induced degradation in lead-free tin perovskite solar cells†
Abstract
The poor stability of lead (Pb)-free tin (Sn)-based perovskites under only oxygen (O2) exposure has attracted extensive research, while their stability under simultaneous light and O2 (light/O2) exposure is unexplored. Herein, we found that the (NH2)2CHSnI3 (FASnI3) perovskite degrades more severely when exposed to light/O2 than only O2, which we attribute to the superoxide generated via the reaction between O2 and photoexcited electrons. We propose the superoxide-induced degradation routes of FASnI3. Fluorescent molecular probe results indicate higher yield of superoxide in FASnI3 than in FAPbI3. Density functional theory simulation results rationalize that the formation energy of the most preferred sites (iodine vacancy, VI) for superoxide formation in FASnI3 is much lower than that in FAPbI3; meanwhile, superoxide formation at VI is more energetically favorable in FASnI3. A targeted strategy by incorporating halide-containing additives is applied to fill the VI in FASnI3 to suppress superoxide formation. Combined with superoxide yield measurement, capacitance-dominated characterization can systematically differentiate the reduction of surface and interior VI after modification. Understanding the degradation mechanism of FASnI3 upon light/O2 exposure manifests the fatal effect of superoxide on the stability of Sn-based perovskite solar cells.
Please wait while we load your content...
