Comprehensive study of absorption coefficient and charge carrier generation in methylammonium lead iodide perovskite solar cells

• A novel analytical model is developed to describe the absorption coefficient of MAPbI 3 perovskite. • The model accounts for three distinct optical energy gaps, improving agreement with experimental data. • A new extinction coefficient formulation is proposed, offering both physical insight and computational simplicity. • The study highlights the critical role of electronic structure in determining charge carrier generation efficiency. • The model agrees with experiments, providing a reliable tool for performance prediction and optimization. This study investigates the mechanisms of photon absorption and the rate of charge carrier generation in methylammonium lead iodide (MAPbI 3 ) perovskite solar cells. Charge carrier generation rates are influenced by incident light intensity, the material’s absorption coefficient, and its surface reflectivity. By reviewing experimental results from various researchers, we propose a theory for the absorption coefficient in these perovskite structures. This theory, based on band structure calculations and density of states (DOS) diagrams derived via DFT, explains the behavior of the absorption coefficient as a function of the incident photon’s energy and provides an accurate, practical, and relatively simple model. In this model, the dependence of the absorption coefficient on the incident photon energy is linked to three distinct energy gaps identified in the MAPbI 3 ​ perovskite band structure, leading to a three-range representation for this dependency. Additionally, the relationship between the extinction coefficient and photon energy is derived from the absorption coefficient. Finally, this new model is applied to calculate the charge carrier generation as a function of photon energy. The insights provided by this study enhance our understanding of absorption mechanisms and offer pathways for optimizing perovskite solar cells by targeting specific energy ranges in the photon spectrum.