Unveiling the Low-Temperature Pseudodegradation of Photovoltaic Performance in Planar Perovskite Solar Cell by Optoelectronic Observation

The time evolution of the current-voltage characteristic of planar heterojunction perovskite solar cell (PSC) is studied within an operating temperature range of 200-325 K. The photovoltaic (PV) performance of PSC is found to be infl uenced by fi ve carrier transport pathways, which strongly depend on operating temperature and light illumination. At low temperature, a severe degradation of PV performance is presented but temporary. This is attributed to ion accumulation at the TiO2/CH3NH3PbI3 and hole transport material/ CH3NH3PbI3 interfacial regions, as an origin of screening effect of builtin fi eld, evidenced by the low external quantum effi ciency (EQE). By light illumination at open-circuit, a steady PV performance will be reached and the stabilization time increases with decreasing temperature. The recovery of PV performance is attributed to ion diffusion in CH3NH3PbI3 layer in the absence of electric fi eld. The EQE observations indicate that photogenerated carriers are separated and collected effi ciently after a long time light illumination due to a reduction of the screening effect. At high temperature, because of the low ion density at interfacial regions, the PV performance shows a quick response to light. These fi ndings may help understanding of the mechanism of temperature-dependent photogenerated carrier transport in the PSC.