Microstructure Modulation Of The Ch3nh3pbi3 Layer In Perovskite Solar Cells By 2-Propanol Pre-Wetting And Annealing In A Spray-Assisted Solution Process

As the light absorption layer, a CH3NH3PbI3 perovskite film with a fully and homogeneously covered flat surface is crucially important for perovskite photovoltaic devices. Herein, the sequential method is improved by introducing a spray-assisted solution process (SSP) instead of the commonly used dipping process in CH3NH3PbI3 perovskite film deposition. The morphology analysis for PbI2 films found that the airflow of the spray pre-wetting process provides a driving force for accelerating the dissolution and deep infiltration, which is helpful to form a mesoporous PbI2 scaffold. So the 2-propanol (IPA) prewetting has advantages to complete the reaction of PbI2 and CH3NH3I through the diffusion channel in the grain boundary and on the surface of the PbI2 film. Furthermore, the grain size and surface coverage of the film can be controlled effectively by a facile IPA pre-wetting process in the SSP. Meanwhile, the influence of the annealing process on the crystallization, chemical composition, microstructures and carrier transport properties of the perovskite films were investigated. Our results showed that an optimum annealing temperature and time can reduce crystal defects in the film and weaken the hysteresis phenomenon of the perovskite solar cell. Efficient mesoporous structured perovskite solar cells were fabricated with an optimal PCE of 14.2%, because of the improved perovskite film preparation method.