Effect of chlorobenzene on the optical and structural properties of CH3NH3PbI3:DMF perovskite films

Methylammonium lead iodide perovskites (MAPbI3) thin films were prepared by changing the molarity concentration of methylammonium iodide and lead iodide in the N,N- dimethylformamide solvent, with and without chlorobenzene (CB). Rietveld refinement analysis revealed that all prepared samples belong to tetragonal CH3NH3PbI3 phase (sp. gr. I4/mcm). The effect of MAPbI3 concentration on the lattice parameters, crystallite size, lattice microstrain and dislocation density of the prepared films with and without CB was investigated in detail. The FESEM images of perovskite films indicated the presence of pinholes in each sample, and the number of pinholes reduced as CB added to MAPbI3. Generally, the transmission and reflection spectra decreased as the amount of MAPbI3 increased in the films; also, both are reduced as CB added to films. The value of the reflectivity over measured wavelengths changed from about 1% to about 18% and 12% in the case of films without and with CB, respectively. Without CB, the highest absorbance intensity was obtained for 1.3 M films, while with CB the 1.5 M film has the highest absorbance. The number of bandgaps appeared in different samples depending on the concentration of MAPbI3 and CB. The refractive index at 500 nm for (1, 1.3 and 1.5 M) MAPbI3 films without CB are 1.6, 1.44, 1.43 and 1.31 respectively, where its value in the corresponding films with CB are 1.34, 1.3, 1.3 and 1.28, respectively. The effect of MAPbI3 concentration and the existence of CB during the film preparation on the extinction coefficient, refractive index, dielectric constant, the photoluminescence peak position, and PL intensity for the different films were explored.