Improved performance of sol-gel ZnO-based perovskite solar cells via TiCl4 interfacial modification

CH3NH3PbI3 perovskite materials deposited on ZnO electron transport layers (ETLs) undergo decomposition during annealing in N2 atmosphere. We found that this decomposition can be retarded by restricting sublimation. Moreover, the decomposition upon thermal annealing is highly suppressed by TiCl4 treatment of the ZnO ETLs. Finally, we present a facile method for prolonged annealing in sol-gel ZnO-based perovskite solar cells, which exhibit a power conversion efficiency of 16.5% at a small area of 0.098 cm2 and 15.1% at a large area of 1 cm2 (active area) under AM 1.5 simulated sunlight illumination. This study shows that TiCl4 hydrolysis is an effective surface treatment for ZnO ETLs to be used in low-temperature and efficient sol-gel ZnO-based perovskite solar cells.