Efficient solid-state perovskite solar cells based on nanostructured zinc oxide designed by strategic low temperature water oxidation

Abstract

A strategic low temperature oxidation of Zn thin films in water is presented to fabricate nanostructured ZnO as an electron transporting layer in efficient solid-state perovskite solar cells (glass/ITO/ZnO/perovskite/P3HT/Ag) for the first time. By controlling the oxidation time and temperature, novel nanostructured surface morphologies including platelets, rods, honeycomb structures and fibrous wires composed of particles are obtained. Nanostructures formed in longer reaction times show reduced concentration of surface defects improving the possible recombination losses in solar cells. The perovskite solar cell based on room temperature oxidized fibrous ZnO nanostructures exhibited a respectable maximum efficiency of 3.62%. This efficiency is improved up to 5.96% by utilizing the pointed nanorod morphology generated by oxidation at a growth temperature of 90 °C for 8 h. Most of the fabricated solar cells based on rod-like structures show higher efficiencies, weaker hysteresis behavior and good stability owing to the enhanced electronic properties and interfacial area between ZnO and the active layer. These results highlight the potential of wet oxidized nanostructured ZnO as an electron selective layer for low cost, sustainable and large-scale production of flexible perovskite solar cells.