Control of IV Hysteresis in CH3NH3PbI3 Perovskite Solar Cell

Mismatch of current (I)-voltage (V) curves with respect to the scan direction, so-called IV 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 IV 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 IV 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 Cf 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 IV hysteresis in perovskite solar cell.