Control of <i>I</i>–<i>V</i> Hysteresis in CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> Perovskite Solar Cell

Mismatch of current (<i>I</i>)-voltage (<i>V</i>) curves with respect to the scan direction, so-called <i>I</i>–<i>V</i> hysteresis, raises critical issue in MAPbI<sub>3</sub> (MA = CH<sub>3</sub>NH<sub>3</sub>) 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>I</i>–<i>V</i> hysteresis of perovskite solar cell that was systematically evaluated by the interface-dependent electrode polarizations. Frequency (<i>f</i>)-dependent capacitance (C) revealed that the normal planar structure with the TiO<sub>2</sub>/MAPbI<sub>3</sub>/spiro-MeOTAD configuration showed most significant <i>I</i>–<i>V</i> hysteresis along with highest capacitance (10<sup>–2</sup> F/cm<sup>2</sup>) among the studied cell configurations. Substantial reduction in capacitance to 10<sup>–3</sup> F/cm<sup>2</sup> was observed upon replacing TiO<sub>2</sub> with PCBM, indicative of the TiO<sub>2</sub> layer being mainly responsible for the hysteresis. The capacitance was intensively reduced to 10<sup>–5</sup> F/cm<sup>2</sup> and <i>C</i>–<i>f</i> 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>I</i>–<i>V</i> hysteresis in perovskite solar cell.