Control of I-V Hysteresis in CH₃NH₃PbI₃ Perovskite Solar Cell

Mismatch of current (I)-voltage (V) curves with respect to the scan direction, so-called I-V hysteresis, raises critical issue in MAPbI₃ (MA = CH₃NH₃) perovskite solar cell. Although ferroelectric and ion migration have been proposed as a basis for the hysteresis, origin of hysteresis has not been apparently unraveled. We report here on the origin of I-V hysteresis of perovskite solar cell that was systematically evaluated by the interface-dependent electrode polarizations. Frequency (f)-dependent capacitance (C) revealed that the normal planar structure with the TiO₂/MAPbI₃/spiro-MeOTAD configuration showed most significant I-V hysteresis along with highest capacitance (10^-2 F/cm²) among the studied cell configurations. Substantial reduction in capacitance to 10^-3 F/cm² was observed upon replacing TiO₂ with PCBM, indicative of the TiO₂ layer being mainly responsible for the hysteresis. The capacitance was intensively reduced to 10^-5 F/cm² and C-f feature shifted to higher frequency for the hysteresis-free planar structures with combination of PEDOT:PSS, NiO, and PCBM, which underlines the spiro-MeOTAD in part contributes to the hysteresis. This work is expected to provide a key to the solution of the problem on I-V hysteresis in perovskite solar cell.