Narrowing band gap and enhanced visible-light absorption of metal-doped non-toxic CsSnCl3 metal halides for potential optoelectronic applications

Non-toxic (lead-free) inorganic perovskites have seized the leading position in the race for the commercialization of solar cells and other photovoltaic devices. The present study is the first theoretical approach to show that metal (Cr/Mn)-doped CsSnCl3 perovskites exhibit high optical absorption, high photoconductivity, and high dielectric constant not only in the visible but also in the ultraviolet region of light energy due to the narrowing band gap. We carried out density functional theory (DFT) investigations to find the structural, electronic, optical, and mechanical properties of pristine CsSnCl3, Cr-, and Mn-doped CsSnCl3 samples in detail. The investigation of the optical functions displayed that the absorption edges of both Cr- and Mn-doped CsSnCl3 shifted greatly in the direction of the low photon energy area (red-shift) compared with the pristine sample. An extra very high intensity peak of absorption was noted for both Cr- and Mn-doped CsSnCl3 in the visible energy region. The investigation of the mechanical parameters revealed that both Cr- and Mn-doped CsSnCl3 samples were as mechanically stable and highly ductile as the pure CsSnCl3 sample. The investigation of the electronic properties demonstrated that the creation of intermediate states in the band gap for both the Cr- and Mn-doped CsSnCl3 samples made the transition of excited photoelectrons to the conduction band from the valence band easier. A combined study suggested that Mn-doped CsSnCl3 was better suited for applications in high potency solar cells and other optoelectronic devices than the other inorganic metal halide perovskites.