Unraveling the roles of mesoporous TiO2 framework in CH3NH3PbI3 perovskite solar cells

Both of planar and mesoporous architectures prevail for perovskite solar cells (PSCs). However, it is still an open question how the architecture affects the performance of PSCs. The inconsistent results in the references often create confusion. In particular, the specific roles of mesoporous frameworks are yet to be well elaborated and require further clarification. In this study, we carefully compared the properties of perovskite films and the device performances for both architectures to unravel the roles of mesoporous TiO2 framworks in CH3NH3PbI3 PSCs. The detailed characterizations of structural, microscopic, optical and electrical properties revealed that the presence of mesoporous TiO2 framework contributed to enlarged perovskite crystal sizes, enhanced light harvesting, efficient electron extration and suppressed charge recombination. As a result, compared with the planar device, the mesoporous device yielded an improved power conversion efficiency of 18.18%, coupled with a reduced hystersis. This study reveals the benefits of mesoporous TiO2 framework in PSCs and provides the guidance for the design and optimization of architectures for high-performance devices.