Effect of acetic acid concentration on optical properties of lead acetate based methylammonium lead iodide perovskite thin film

High absorption of perovskite thin films is crucial for efficient metal halide perovskite solar cells. In this study, methylammonium lead iodide (CH₃NH₃PbI₃) perovskite thin films are prepared using lead (II) acetate Pb(Ac)₂, acetic acid (HAc) and CH₃NH₃I through solution method. The effect of HAc volume (0 ml–100 ml at step size of 25 ml HAc) on optical properties and parameters of the CH₃NH₃PbI₃ perovskite thin films developed are investigated using UV–Vis spectrophotometry and mathematical correlations. Interestingly, the increase of HAc amount to 75 ml leads to an increase in absorbance, refractive index, extinction co-efficient, dielectric properties and optical conductivity and a decrease in transmittance and optical band gaps of the CH₃NH₃PbI₃ perovskite thin films. The optimized film is obtained at 75 ml HAc at which refractive index, film thickness and optical band gap is 1.45 at 485 nm, 355 nm and 1.47 eV, respectively. The enhanced absorption of the optimized thin film is attributable to an increase in structure ordering at HAc amount equals 75 ml. The fabricated CH₃NH₃PbI₃ perovskite thin films have potential as ideal antireflection coatings for solar cells and optoelectronic applications.