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

Graphical Bathing in water : Interfacial engineering greatly improves the reproducibility in the synthesis of planar perovskite solar cells, with a much smaller standard deviation compared to pristine devices. The power conversion efficiency is also greatly increased in comparison, independent of the environmental humidity (0–75 % relative humidity). Low-temperature solution-processed SnO 2 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 SnO 2 film is synthesized using a simple water bath post-treatment, which can remove the surface residuals of SnCl 4 on the SnO 2 films, which is beneficial for the interface charge transport from the perovskite to the SnO 2 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 SnO 2 -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 SnO 2 has shown promise for future commercial PSC applications: 5 cm×5 cm PSC modules have achieved a PCE of 16.16 %.