Optical absorption and stability enhancement in mixed lead, tin, and germanium hybrid halide perovskites for photovoltaic applications

Hybrid halide perovskite (HHP) materials present flexible version of next-generation solar cells and among these, Methyl ammonia lead iodide, i.e., CH 3 NH 3 PbI 3 (MAPbI 3 ), dominated the research field owing to its excellent photovoltaic properties, but its commercial deployment was halted due to the presence of toxic Pb. Mixed cation and anion strategies can play a significant role in improving structural stability and reducing toxicity. Partial or full replacement of Pb with congener but non-toxic elements such as Sn and Ge can facilitate the large uptake of HHP solar cells. In this work by first-principles calculations, we explore the potential alternatives to MAPbI 3 by investigating the structural, electronic and optical properties of MAPb 1-x-y Sn x Ge y I 3 [(x, y) = (0, 0.5), (0.25, 0.25) (0.5, 0)]. The present report indicates that via Ge and Sn-doping in MAPbI 3 , the bandgap can be tuned from 1.16 eV to 0.77 eV. Meanwhile, in the Sn/Ge/Sn–Ge doped MAPbI 3, the optical absorption coefficients get enhanced in the visible region and in the regions as far as mid-infrared, making them better alternatives to toxic MAPbI 3 for photovoltaic applications. Moreover, owing to the outstanding photovoltaic characteristics, MAPb 0.50 Sn 0.25 Ge 0.25 I 3 is proposed as an absorber layer material for the efficient perovskite solar cell modules. • A range of Ge and Sn doping concentration in MAPbI 3 is explored to tune the bandgap from 1.16 eV to 0.77 eV. • In Sn/Ge/Sn–Ge doped MAPbI 3, the optical absorption gets enhanced not only in the visible region but also in mid-infrared. • MAPb 0.50 Sn 0.25 Ge 0.25 I 3 is proposed as an alternate absorber layer in place of pure MAPbI 3 for HHP based solar cells.