Low-Temperature Solution-Processed Amorphous Titania Nanowire Thin Films for 1 cm² Perovskite Solar Cells

The development of solution-processed inorganic amorphous electron-transporting layers (ETLs) is important for the future commercialization of perovskite solar cells (PSCs). The formation of such ETLs using low-temperature processing techniques will lower potential production costs and accommodate diverse substrate materials. Herein, a low-temperature (<150 °C) solution process forms amorphous titania nanowire (Am-TNW) thin films on fluorine-doped tin oxide conducting glass substrates. When applied as an ETL in PSCs, the Am-TNW layer achieves a higher average power conversion efficiency (18.3%) relative to that of a nanocrystalline anatase TNW (ATNW) layer obtained after high-temperature (500 °C) heating (16.7%). Compared to the ATNW counterparts, the Am-TNW-based PSCs exhibit inferior charge extraction across the TNW/CH₃NH₃PbI₃ interface but more effectively suppress interfacial charge recombination. The insertion of a fullerene layer between the Am-TNW and CH₃NH₃PbI₃ improves the charge extraction. The Am-TNW-based bilayer ETL gave optimal power conversion efficiencies of 20.3% and 19.0% for PSCs with 0.16 cm² and 1.00 cm² apertures, respectively. This is due to the concurrent advantages of enhanced light absorption, facilitated charge extraction, and reduced charge recombination. The use of the Am-TNW as an ETL in PSCs provides a facile, efficient way to increase the effectiveness of PSCs.