Effects of Cr- and Mn-alloying on the band gap tuning, and optical and electronic properties of lead-free CsSnBr perovskites for optoelectronic applications.

Nowadays, lead-free metal halide perovskite materials have become more popular in the field of commercialization owing to their potential use in solar cells and for other optoelectronic applications. In this study, we used density functional theory to determine the different optoelectronic properties, such as structural, optical, electronic, and elastic properties, of pure CsSnBr and metal (Cr/Mn) alloyed CsSnBr. The present study suggests high absorption with a narrow band gap, a high dielectric effect, high conductivity, and reasonable reflectivity in the visible region under metal alloying. The calculated absorption coefficients indicate that the absorption edge mainly shifted (red-shift) towards the lower energy region in the event of alloying, and a clear peak was observed in the visible region. The creation of an intermediate state (dopant level) in the band structure of the alloying samples allows excited photoelectrons to transfer from the valence band to the conduction band. The alloying materials exhibit a highly ductile nature and are mechanically stable as pristine samples. The alloying effects seen in the present investigation suggest that Mn-alloyed CsSnBr is remarkable, showing appropriate characteristics for use in solar cell devices and for other optoelectronic applications in comparison with other lead-free (toxin-free) perovskite materials.