Mesoscopic CH3NH3PbI3 perovskite solar cells using TiO2 inverse opal electron-conducting scaffoldsElectronic supplementary information (ESI) available. See DOI: 10.1039/c6ta07004c

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. A mesoscopic inverse opal is prepared as an electron-conducting scaffold for high efficiency and stable perovskite solar cells.