Improving the Extraction of Photogenerated Electrons with SnO₂ Nanocolloids for Efficient Planar Perovskite Solar Cells

Abstract

Great attention to cost‐effective high‐efficiency solar power conversion of trihalide perovskite solar cells (PSCs) has been hovering at high levels in the recent 5 years. Among PSC devices, admittedly, TiO 2 is the most widely used electron transport layer (ETL); however, its low mobility which is even less than that of CH 3 NH 3 PbI 3 makes it not an ideal material. In principle, SnO 2 with higher electron mobility can be regarded as a positive alternative. Herein, a SnO 2 nanocolloid sol with ≈3 nm in size synthesized at 60 °C was spin‐coated onto the fuorine‐doped tin oxide (FTO) glass as the ETL of planar CH 3 NH 3 PbI 3 perovskite solar cells. TiCl 4 treatment of SnO 2 ‐coated FTO is found to improve crystallization and increase the surface coverage of perovskites, which plays a pivotal role in improving the power conversion efficiency (PCE). In this report, a champion efficiency of 14.69% ( J sc = 21.19 mA cm −2 , V oc = 1023 mV, and FF = 0.678) is obtained with a metal mask at one sun illumination (AM 1.5G, 100 mW cm −2 ). Compared to the typical TiO 2 , the SnO 2 ETL efficiently facilitates the separation and transportation of photogenerated electrons/holes from the perovskite absorber, which results in a significant enhancement of photocurrent and PCE.