CsPbI<inf>3</inf> perovskite solar cell and decoding its skink feature in J-V curve

Skink feature in the current density-voltage (J–V) characteristic is observed in an inorganic perovskite CsPbI3 thin film solar cell. The fabricated CsPbI3 solar cell attained maximum efficiency of 8.8% under one sun illumination. It showed a prominent skink phenomenon in the positive biasing region near the open-circuit voltage in the illuminated J–V curve. Skink is a curvilinear s-shape feature in J-V that dramatically deteriorate the fill factor. This study explored the probable cause of such a skink feature by theoretical modelling. It is observed that energy level mismatch, through a relatively high valence band offset (VBO) barrier at the hole transport layer HTL/perovskite junction along with a bulk defect in perovskite, replicates the skink feature in simulated J-V. We showed a one-to-one relation between the skink feature in the J-V curve and its steering parameters in the CsPbI3 device. This one-to-one dependence provides a peek into the device's working and is of great help for understanding the defect physics of experimental devices.