Designing nanobowl arrays of mesoporous TiO2 as an alternative electron transporting layer for carbon cathode-based perovskite solar cells

Abstract

In this work, we have designed a mesoporous TiO₂ nanobowl (NB) array with pore size, bowl size and film thickness being easily controllable by the sol–gel process and the polystyrene (PS) template diameter. Based on the TiO₂ NB array, we fabricated carbon cathode based perovskite solar cells (C-PSCs) to investigate the impact of TiO₂ NB nanostructures on the performance of the as-obtained C-PSCs devices. As expected, the TiO₂ NB based devices show a higher power conversion efficiency (PCE) than that of the planar counterpart, mainly due to the enhanced light absorption arising from the NB-assisted light management, the improved pore-filling of high quality perovskite crystals and the increased interface contact for rapid electron extraction and fast charge transport. Leveraging these advantages of the novel TiO₂ NB film, the 220 nm-PS templated TiO₂ NB based devices performed the best on both light absorption capability and charge extraction, and achieved a PCE up to 12.02% with good stability, which is 37% higher than that of the planar counterpart. These results point to a viable and convenient route toward the fabrication of TiO₂ ETL nanostructures for high performance PSCs.