Crystallinity and defect state engineering in organo-lead halide perovskite for high-efficiency solar cells

The organo-lead halide perovskite material is a promising alternative in solar cell applications due to its solution processability, excellent light absorption and charge transporting properties. It is known that the morphology of the perovskite film is critical for high device performance. In this work, a feasible solvent annealing method was developed to regulate the crystallization process. Perovskite films consisting of atomically smooth single crystalline domains of up to 5 microns have been prepared, with proper annealing of the solvent and precursor ingredients. The defect density was reduced to half of that in the thermally-annealed film. The crystallization mechanism and defect physics have been investigated based on the solvent-annealed film. The improvement in crystallinity and defect states led to a 53% increase in the efficiency of the solar cells, reaching a value of 14.13% based on the p-i-n structure.