Role of Trapped Carriers Dynamics in Operating Lead Halide Wide-Bandgap Perovskite Solar Cells

Here we investigate the role of charge trapping/recombination dynamics at halide interstitials, responsible for halide segregation, when wide-band gap perovskites are embodied in solar cells. Such dynamics can be either fast (picoseconds-nanoseconds) or slow (nanoseconds-μs) according to the oxidation state of the halide defect. When carriers accumulate within the perovskite, at open-circuit conditions, the trapping/recombination process having the slowest dynamics causes photo instability predominantly. When the solar cell is under a load, the device performances are mainly affected by the fast carrier trapping, depending on a direct competition between the trapping rate and the charge extraction efficiency. We show that by selectively passivating the defects correlated to fast carrier trappings, the solar cell operation and stability can be largely improved by improving the charge extraction. Thus, a deep knowledge of the chemical nature of defect activities and the corresponding electronic dynamics is crucial for maximizing the performance and stability of wide bandgap perovskite solar cells.