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/cm(2)) among the studied cell configurations. Substantial reduction in capacitance to 10(-3) F/cm(2) 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/cm(2) 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.