First-Principles Study of Ge-Doped CH₃NH₃PbI₃ Perovskite:

This study focuses on the examination of the optical and electronic properties of perovskite structures, with particular emphasis on the effect of germanium ( Ge) doping on these properties. The aim of this study is to explore how doping with Ge can affect its optoelectronic properties and thus optimize its efficiency in applications such as photovoltaic solar cells. We used the code CASTEP from the Materials Studio software to calculate the optical and electronic attributes of perovskite structures , doping the lead (Pb) metal with three different percentages of germanium: 12.5%, 25%, and 37.5%. Pure perovskite has a bandgap energy (Eg) of 1.733 eV. The bandgap energies of the doped materials are 1.57 eV, 1.545 eV, and 1.503 eV, respectively. The pure structure has a maximum absorption coefficient of in the wavelength range of 400 nm to 800 nm. This calculation also studied the effects of Ge doping on the bandgap energy, absorption, total density of states, the real and imaginary components of the dielectric function, as well as the refractive index, the optical conductivity, and the loss function. The computed results align with the experimental findings and provide information on the possibility of modulating the optical properties and electronic of through Ge doping, doping with Ge enhances its optoelectronic properties, particularly its absorption in the visible range, optimizing its efficiency in photovoltaic solar cells. These improvements make Ge-doped promising for renewable energy applications, as well as in light-emitting diodes and laser devices.