An innovative analysis of critical point parabolic band oscillators of lead and lead-free halide perovskites

Abstract

This paper describes an innovative analysis of critical point parabolic band (CPPB) oscillators used to model bandgap of methylammonium lead halide (MAPbI₃) and two lead-free halide perovskites – cesium bismuth iodide (Cs₃Bi₂I₉) and cesium antimony iodide (Cs₃Sb₂I₉). Using this analysis, we modeled the dielectric response and extracted key oscillator parameters: amplitude, broadening, phase and energy position. These parameters provide insight into the optical transitions and band structure of the studied materials. Using this model, we determined optical bandgap energies as 1.63 eV for MAPbI₃, 2.20 eV for Cs₃Sb₂I₉, and 2.70 eV for Cs₃Bi₂I₉. In addition, we studied how the degradation of the perovskite thin layer affects the trends in the extracted parameters.