From Pb-based MAPbI3−xClx to Pb-free FASnI3−xClx and CsSbCl4 derivatives fabrication in atmospheric conditions for optoelectronic and solar cell applications

MAPbI₃ is the most attractive perovskite, but toxicity and instability issues hinder its commercial applications. Stability can be improved by halide mixing; however, Pb-free perovskites are designed to alleviate the toxicity and to enable green photovoltaics (PVs). To this end, MAPbI_3-xCl_x, FASnI_3-xCl_x and CsSbCl₄ films are deposited by spay pyrolysis technique in atmospheric conditions. SEM images demonstrated that through this process, high quality film fabrication is possible. Color of the precursor solutions changes with stirring time. High crystallinity and existence of mixed-phases are confirmed by XRD analysis. Compositions greatly impact the morphology and optical properties. Value of α is larger than 10⁵ cm⁻¹ for all films. Band gaps of FASnI_3-xCl_x and CsSbCl₄ are 1.46 eV and 1.52 eV, which are more suitable for PVs, optoelectronic applications than MAPbI_3-xCl_x (E_g = 1.59 eV). The efficiency was obtained as 16.34%, 9.90%, and 13.08% for deposited MAPbI_3-xCl_x, FASnI_3-xCl_x, and CsSbCl₄ films. The lower efficiency can further be enhanced by optimizing parameters, and in this study it was found as 20.78%, 11.93%, and 18.02%. Theoretical calculations show the films can easily produce O₂ by a strong oxidation process. Thus, the favorable characteristics of FASnI_3-xCl_x and CsSbCl₄ make alternative Pb-free perovskites for PV, electronic, and optoelectronic applications.