Slow Response of Carrier Dynamics in Perovskite Interface upon Illumination.

The current-voltage hysteresis, as well as the performance instability of perovskite solar cells (PSCs) under a working condition, is serving as the major obstacle toward their commercialization while the exact fundamental mechanisms to these issues are still in debate. In this study, we investigated the slow variation of photogenerated carrier dynamics in a (FAPbI3)0.85(MAPbBr3)0.15 perovskite interface under continuous illumination. Different response behaviors of carrier dynamics in the perovskite interfaces with and without the hole transport layer, Spiro-OMeTAD (Spiro), were systematically studied by time-dependent, steady-state, and time-resolved photoluminescence. It was demonstrated that a light-induced defect curing process is dominantly responsible for the carrier dynamics evolution for the perovskite interface without Spiro, whereas both defect curing process and mobile ion migration should be accounted for the dynamic response of the perovskite interface contact with Spiro. When contacted with Spiro, the energy band curvature evolution in the perovskite interface induced by ion migration would decrease the hole transfer rate from the perovskite interface to Spiro upon illumination. This research work can faithfully highlight the strong correlation of slow photoresponse behaviors of the perovskite interface with both light-induced defect curing and ion migration processes, providing novel implications into the physical mechanism for the slow variation of PSC performances under a working condition.