Influence of germanium doping on the structural, band structure, and optical properties of RbPbCl3 for optoelectronics: A DFT approach

Semiconducting lead halide perovskites have emerged as significant absorber materials aimed at improving the performance of photovoltaic and optoelectronic devices. In this investigation, we performed a density functional theory (DFT) calculation to analyze the optical properties, electronic tuning, and structural distortion of RbPbCl 3 and Ge doped RbPbCl 3 perovskites. The incorporation of Ge into the RbPbCl 3 lattice resulted in a notable structural deformation, resulting in phase transition from cubic to tetragonal. The calculated values for the Goldschmidt tolerance factor are 0.910, 0.933, and 0.956, while the Octahedral factor values are 0.428, 0.394, and 0.360 for RbPbCl 3 , RbPb 0.75 Ge 0.25 Cl 3 , and RbPb 0.5 Ge 0.5 Cl 3 , respectively. The determined bandgap of RbPbCl 3 is 2.19 eV, exhibiting a direct nature at the R high symmetry point. Upon substituting Ge 4 + for Pb 2+ at concentrations of 25% and 50%, a notable reduction in the band gap was observed, yielding values of 1.66 eV and 1.37 eV, respectively. Furthermore, the effective mass of electrons and holes was calculated to observe the rates of charge carrier generation and migration within the materials. Notably, due to reduction in bandgap and phase transition, remarkable optical properties were demonstrated within the ultraviolet and visible regions. The incorporation of Ge 4+ at the B site of RbPbCl 3 exhibits promising properties, making it a prominent material for use in optoelectronic and photovoltaic devices.