Role of the chemical substitution on the structural and luminescence properties of the mixed halide perovskite thin MAPbI3 − xBrx (0 ≤ x ≤ 1) films

Mixed bromide iodide lead perovskites were prepared from methylamine, lead nitrate and the corresponding hydroX acid (X = I, Br), they were then deposited as thin films on ITO substrate by the spin coating process. X-ray diffraction analyses indicated the formation of a tetragonal phase I4/mcm up to x = 0.4 and a cubic perovskite with space group Pm3 m in the composition range of 0.6 ≤ x ≤ 1. Mixed lead perovskites showed a high absorbance in the UV-vis range. The band gap energy of thin films were estimated from absorbance spectral measurements, it was found that the onset of the absorption edge for MAPbI3 − xBrx (x < 1) thin films is ranging between 1.58 to 1.72 eV. Photoluminescence emission energies for mixed halide perovskites presented intermediate values from 781 nm (MAPbI3) to 545 nm (MAPbBr3).