A DFT and Time-dependent DFT Investigation of the Structural, Electronic and Optical Properties of Lead-free FAMgI₃ Perovskite for Photovoltaic Applications

Lead-free perovskites are among the compounds that are currently the most investigated for their potential application in photovoltaics because of their nontoxic effect on the environment. In this work, we report the structural, electronic, and optical properties of hybrid organic-inorganic FAMgI₃-based perovskite for use in photovoltaic technology. We use density functional theory (DFT) and time-dependent density functional theory (TDDFT) executed in the Quantum Espresso framework. These calculations were performed by applying the generalized gradient approximation of Perdew–Burke–Ernzerhof (GGA-PBE), the GGA-PBE revised for solids (GGA-PBESol), and local density approximation (LDA). The band structure and total and partial density of states (DOS and PDOS) of this perovskite are elaborated and discussed; the semiconductor behavior and direct band gap of this material are demonstrated. In addition, we investigated the effect of spin–orbit coupling (SOC) correction on the band gap energy and demonstrated that the band gap energy was reduced by the SOC effect. In fact, when using the GGA-PBE in the absence of SOC, the calculated band gap energy was 1.4 eV. When including the SOC effect, it is demonstrated that the band gap energy decreases to 1.01 eV. Moreover, the optical properties have been presented and discussed. The material also exhibits excellent optical properties, including high absorption, and can therefore be used in the development of lead-free perovskite solar cells and other optoelectronic applications.