Low temperature-processed ZnO nanorods-TiO2 nanoparticles composite as electron transporting layer for perovskite solar cells

Abstract Electron transport is one of the most crucial processes that determine charge collection efficiency in perovskite solar cells. Herein, a low temperature-processed ZnO-TiO 2 nanocomposite is developed as an electron transporting layer for perovskite solar cells. Highly-crystalline ZnO nanorods were deposited electrochemically which served as the scaffold for spin-coated TiO 2 nanoparticles. This ZnO-TiO 2 nanocomposite is designed to integrate the fast electron transport along the nanorods and the additional surface area provided by the nanoparticles for enhanced electronic contact between the electron-transporting layer and the perovskite layer. A weak photoluminescence quenching behavior was observed for ZnO nanorods after TiO 2 nanoparticle coating which signifies a reduction in ZnO surface defects. Steady-state photoluminescence and optical absorption measurements indicated improved charge transfer and higher absorption of light, respectively, when ZnO-TiO 2 nanocomposite is contacted with the CH 3 NH 3 PbI 3 layer. However, the clustering of the nanoparticles caused inefficient charge transfer from TiO 2 to ZnO.