Enhanced near-ultraviolet and visible light absorption of organic-inorganic halide perovskites by co-doping with cesium and barium: Insight from first-principles calculations

Compositional engineering of halide perovskite solar cells has been showing potential for the enhancement of efficiency and stability. The co-doping effects of Ba and Cs on the electronic structure and optical properties of organic-inorganic halide perovskites Cs(x)MA(1-x)Ba(y)Pb(1-y)I(3 ) were performed using first-principles calculations. Substitution of MA molecules with Cs atom can increase the stability, while the substitution of Pb atoms with Ba atoms can decrease the toxic issues. Lattice structural analysis indicates that the doping of Cs and Ba induce the distortion of octahedra. Tunable band gaps from 1.20 eV to 2.47 eV are obtained in hybrid halide perovskites with various chemical compositions. Doping Cs atoms compress the neighboring Pb-I and Ba-I bond and reduce the I-Pb-I bond angles. It is unveiled that compositional engineering of hybrid halide perovskite via doping Cs and Ba ions can design the optical properties. In the near-ultraviolet regions, the optical absorption coefficient of Cs and Ba co-doped hybrid halide perovskites are significantly enhanced, while the absorption efficiency of Cs and Ba co-doped at the strongest emission area of visible light is 1.5 times larger than that of undoped MAPbI(3).