Preparation of nanocuboid perovskite CH3NH3PbI3 thin films with controlled grain size, morphology and phase purity

In this work we prepared nanocuboid perovskite CH₃NH₃PbI₃ thin films by using sequential two-step solution method, and tried to control the grain size, morphology and phase purity by controlling the diffusion behavior of CH₃NH₃I in PbI₂. Our experimental results indicate that the diffusion behavior of CH₃NH₃I in PbI₂ can be effectively controlled by adjusting the concentration of CH₃NH₃I solution and immersing temperature, and thus the grain size, morphology and phase purity were controllable. The formation dynamics of perovskite was discussed and the impact of grain size, morphology and purity on the transport and photoelectric properties of the films were investigated. The results show that the surface uniformity and the CH₃NH₃PbI₃ phase purity are crucial for achieving high carrier lifetime, high photoconductivity and fast extraction of the photo-induced carriers across the perovskite/HTM (hole transport materials) interface.When the optimized CH₃NH₃PbI₃ thin film which was prepared using CH₃NH₃I solution with concentration of 10 mg/ml at 70 °C was interfaced with Spiro-MeOTAD, the life time as short as 0.31 ns was achieved, indicating the very efficient extraction of the photo-induced carriers across the perovskite/HTM interface.