Bandgap assessment of compositional variation for uncovering high-efficiency improved stable all-inorganic lead-free perovskite solar cells

Bandgap evolution with composition variation of ABX${}_3$ perovskites is explored, where A = MA, FA, Cs, Rb; B = Pb, Sn, Ge; and X = I, Br, Cl. To identify alternative lead-free and stable perovskite-absorbing compositions, all possible combinations of compositions are screened under constraints of structural stability and optimal bandgap values. The comparative analysis reveals Cs-, Rb-, and Ge-based perovskite as an alternative to MAPbI${}_3$'s toxicity and stability issues. The Cs-, Rb-, and Ge-based perovskites are lead free and structurally stable, with the requisite optical cum electrical properties. The numerical simulation of the proposed Cs${}_{1-y}$Rb${}_y$Ge(Br${}_x$I${}_{1-x}$)${}_3$-based device shows efficiency above the 22% mark. All aspects of the proposed device are identical to MAPbI${}_3$, except that the MAPbI${}_3$ absorber is replaced with a Cs${}_{1-y}$Rb${}_y$Ge(Br${}_x$I${}_{1-x}$)${}_3$-based absorber. (© 2023 Wiley‐VCH GmbH)