Mesoscopic CH₃NH₃PbI₃ perovskite solar cells using TiO₂ inverse opal electron-conducting scaffolds

One of the current needs of applications involving perovskite solar cells is reducing the hysteresis of the current density-voltage response with respect to the scan direction and rate. This reduction enables high and stable power conversion efficiency (η). For this purpose, a mesoscopic electron conductor with low trap density and high electron conductivity that balances charge flux is highly desirable. In the present study, we prepared a mesoscopic inverse opal (meso-IO) film with a three-dimensionally interconnected porous structure and used it as an electron-conducting scaffold for perovskite solar cells. We controlled the thickness of the meso-IO scaffold and determined its effect on the cells' photovoltaic performance. Solar cells using the 600 nm thick meso-IO scaffold exhibited a maximum η of 17.1%, no hysteresis of photocurrent density between forward and reverse scan directions, as well as hysteresis of η of only 0.5% p.