Reliable Annealing of CH3NH3PbI3 Films Deposited on ZnO

CH3NH3PbI3 deposited on a ZnO electron transport layer is chemically unstable and decomposes at >80 °C, leaving PbI2 on the substrate along with traces of iodine. We found that this decomposition was reversible and could be prevented if a restricted volume solvent annealing procedure was applied. We also found that decomposition requires the presence of a certain amount of the processing solvent within the film. Finally, we developed a reliable annealing protocol for depositing perovskite film on ZnO, which resulted in the generation of repeatable solar cell devices.