Structural, Electronic, and Optical Properties of CsPb(Br_1-xCl_x)₃ Perovskite: First-Principles Study with PBE-GGA and mBJ-GGA Methods

The effect of halide composition on the structural, electronic, and optical properties of CsPb(Br_1-xCl_x)₃ perovskite was investigated in this study. When the chloride (Cl) content of x was increased, the unit cell volume decreased with a linear function. Theoretical X-ray diffraction analyses showed that the peak (at 2θ = 30.4°) shifts to a larger angle (at 2θ = 31.9°) when the average fraction of the incorporated Cl increased. The energy bandgap (E_g) was observed to increase with the increase in Cl concentration. For x = 0.00, 0.25, 0.33, 0.50, 0.66, 0.75, and 1.00, the E_g values calculated using the Perdew-Burke-Ernzerhof potential were between 1.53 and 1.93 eV, while those calculated using the modified Becke-Johnson generalized gradient approximation (mBJ-GGA) potential were between 2.23 and 2.90 eV. The E_g calculated using the mBJ-GGA method best matched the experimental values reported. The effective masses decreased with a concentration increase of Cl to 0.33 and then increased with a further increase in the concentration of Cl. Calculated photoabsorption coefficients show a blue shift of absorption at higher Cl content. The calculations indicate that CsPb(Br_1-xCl_x)₃ perovskite could be used in optical and optoelectronic devices by partly replacing bromide with chloride.