Effect of metal doping on the visible light absorption, electronic structure and mechanical properties of non-toxic metal halide CsGeCl 3 .

Non-toxic metal halide perovskites have become forefront for commercialization of the perovskite solar cells and optoelectronic devices. In the present study, for the first time we show that particular metal doping in CsGeCl 3 halide can considerably enhance the absorbance both in the visible and ultraviolet light energy range. We have carried out DFT based first principles calculations on Mn-doped and Ni-doped CsGeCl 3 halide. We investigate the detailed structural, optical, electronic and mechanical properties of all the doped compositions theoretically. The study of the optical properties shows that the absorption edge of both Ni and Mn-doped CsGeCl 3 is shifted toward the low energy region (red shift) relative to the pristine one. An additional peak is observed for both doped profiles in the visible light energy region. The study of the mechanical properties demonstrates that both the doped samples are mechanically stable and ductile as the pristine CsGeCl 3 . The study of the electronic properties shows that the excitation of photoelectrons is easier due to the formation of intermediate states in Mn-doped CsGeCl 3 . As a result Mn-doped CsGeCl 3 exhibits higher absorptivity in the visible region than the Ni-doped counterpart. A combinational analysis indicates that CsGe 1- x Mn x Cl 3 is the best lead free candidate among the inorganic perovskite materials for solar cell and optoelectronic applications.