Enhanced Crystallinity of Low-Temperature Solution-Processed SnO₂ for Highly Reproducible Planar Perovskite Solar...

Low-temperature solution-processed SnO₂ as a promising electron-transport material for planar perovskite solar cells (PSCs) has attracted particular attention because of its outstanding properties such as high optical transparency or high electron mobility. However, low-temperature sol-gel processes used in the synthesis are inevitably affected by the humidity of the atmosphere, which results in a wide distribution in the performance of the prepared PSCs owing to the inability to control crystallinity and defects. Herein, a highly crystalline SnO₂ film is synthesized using a simple water bath post-treatment, which can remove the surface residuals of SnCl₄ on the SnO₂ films, which is beneficial for the interface charge transport from the perovskite to the SnO₂ electron-transport layer. An improved performance of the PSCs can be easily obtained applying this treatment, giving rise to a high power conversion efficiency (PCE) of 19.17 %, much higher than that of the pristine SnO₂ -based device (17.59 %). Most importantly, the reproducibility of the devices has been greatly improved, independent of the environmental humidity. Therefore, the enhanced crystallinity of SnO₂ has shown promise for future commercial PSC applications: 5 cm×5 cm PSC modules have achieved a PCE of 16.16 %.