Original research articleLow-cost synthesis, fluorescent properties, growth mechanism and structure of CH3NH3PbI3 with millimeter grains

Organic-inorganic hybrid perovskite materials exhibit excellent photoelectric properties. Their photoelectric performance strongly depends on the film morphology and size, controlled by the deposition technique and subsequent heat treatment. In this article, perovskite film was deposited by the drop casting method in contrast to the widely used techniques such as spin-coating. The perovskite solution precursor was obtained by adding PbI2 and CH3NH3I (1:1 molar ratio) into the N,N-dimethylformamide (DMF) solvent until they were dissolved. Fluorescent properties of the perovskite solution precursor were analyzed. Two emission bands were observed at 1.5 eV and 2.5 eV. Drop the solution precursor on the substrate, evaporate the solvent, the grain size distribution present larger on the edge of the substrate than the center. The grain size distribution presented a ring shape distribution, and the mechanism of grain growth was discussed. During the solvent evaporation, formed compensating flow from the solution center to the edge. The concentration of solution edge is higher, so it promotes the grain growth. The effect of heat treatment temperature on the film morphology, structure and composition was studied. It was found that the grains with millimeter-scale were obtained when the heat treatment temperature changed from 70 °C to 115 °C. Furthermore, increasing the heat treatment temperature above a certain threshold lead to the additional formation of PbI2.

143The CH3NH3PbI3 perovskite films with millimeters grains were prepared with drop-casting method. The grain size distribution presented a ring shape distribution, and the film growth mechanism was discussed.