Low‐Temperature Processed Nanostructured Rutile TiO₂ Array Films for Perovskite Solar Cells With High Efficiency and Stability

The rutile TiO₂ array (RTA) films consisting of vertically oriented nanoneedles and/or nanosheets are grown on a fluorine‐doped tin oxide (FTO) glass substrate via a chemical bath deposition (CBD) process at 70 °C, and are utilized as electron transport layer (ETL) for CH₃NH₃PbI₃‐based perovskite solar cells (PSCs). The morphology and microstructure of the RTA films can be tuned by varying the CBD time. A mixed nanoneedles/nanosheets array film (∼250 nm thickness) derived from 60 min CBD process achieve a power conversion efficiency (PCE) up to 15.4% with reduced hysteresis, improved reproducibility, and stability as compared to those PSCs based on traditional mesoscopic‐TiO₂ or planar‐TiO₂ ETLs, which is due to the lower charge recombination, more efficient hole‐blocking, and electron transport. After aging and storage in the dark, the optimal PSC exhibits a slightly improved PCE (16.3%), which is the highest one among those CH₃NH₃PbI₃‐based PSCs fabricated with low‐temperature processed RTAs reported previously. This work is the first example of vertically oriented nanosheets and/or nanoneedles RTA film grown on a conductive glass to serve as ETL of PSC, and the low‐temperature procedure of the RTA film paves a promising low‐cost way for fabricating large‐scale PSCs.