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

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, TiO2 is the most widely used electron transport layer (ETL); however, its low mobility which is even less than that of CH3NH3PbI3 makes it not an ideal material. In principle, SnO2 with higher electron mobility can be regarded as a positive alternative. Herein, a SnO2 nanocolloid sol with approximate to 3 nm in size synthesized at 60 degrees C was spin-coated onto the fuorine-doped tin oxide (FTO) glass as the ETL of planar CH3NH3PbI3 perovskite solar cells. TiCl4 treatment of SnO2-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 TiO2, the SnO2 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.