Chemical bath deposited rutile TiO2 compact layer toward efficient planar heterojunction perovskite solar cells

Abstract

TiO2 is a best choice of electron transport layers in perovskite solar cells, due to its high electron mobility and stability. However, traditional TiO2 processing method requires rather high annealing temperature (>500°C), preventing it from application to flexible devices. Here, we show that TiO2 thin films can be synthesized via chemical bath deposition below 100°C. Typically, a compact layer of rutile TiO2 is deposited onto fluorine-doped tin oxide (FTO) coated substrates, in an aqueous TiCl4 solution at 70°C. Through the optimization of precursor concentration and ultraviolet-ozone surface modification, over 12% power conversion efficiency can be achieved for CH3NH3PbI3 based perovskite solar cells. These findings offer a potential low-temperature technical solution in using TiO2 thin film as an effective transport layer for flexible perovskite solar cells.