Abnormal Current-Voltage Hysteresis Induced by Reverse Bias in Organic-Inorganic Hybrid Perovskite Photovoltaics

In this study, reverse bias (RB)-induced abnormal hysteresis is investigated in perovskite solar cells (PVSCs) with nickel oxide (NiO_x)/methylammonium lead iodide (CH₃NH₃PbI₃) interfaces. Through comprehensive current-voltage (I-V) characterization and bias-dependent external quantum efficiency (EQE) measurements, we demonstrate that this phenomenon is caused by the interfacial ion accumulation intrinsic to CH₃NH₃PbI₃. Subsequently, via systematic analysis we discover that the abnormal I-V behavior is remarkably similar to tunnel diode I-V characteristics and is due to the formation of a transient tunnel junction at NiO_x/CH₃NH₃PbI₃ interfaces under RB. The detailed analysis navigating the complexities of I-V behavior in CH₃NH₃PbI₃-based solar cells provided here ultimately illuminates possibilities in modulating ion motion and hysteresis via interfacial engineering in PVSCs. Furthermore, this work shows that RB can alter how CH₃NH₃PbI₃ contributes to the functional nature of devices and provides the first steps toward approaching functional perovskite interfaces in new ways for metrology and analysis of complex transient processes.