First-Principles Study on the Optoelectronic and Mechanical Properties of Lead-Free Semiconductor Silicon Perovskites ASiBr3 (A = K, Rb, Cs)

We deployed density functional theory to assess the structural, electronic, elastic, and optical properties of ASiBr3 (A = K, Rb, and Cs). KSiBr3, RbSiBr3, and CsSiBr3 band structure profiles suggest they are semiconductors with direct band gaps of 0.34, 0.36, and 0.39 eV, respectively. The material’s dynamic stability is evidenced by the formation energies acquired negative values (−2.35, −2.18, and −2.08 for K, Rb, and Cs respectively). Mechanical characteristics and elastic constants measured suggest the compound’s mechanical stability and ductile character, which was assessed by calculating the Poissons ratio (>0.25) and Pugh’s ratio (>1.75). The research also explores optical properties, including the dielectric function, refractive index, reflectivity, optical conductivity, absorption coefficient, and extinction coefficient for the optical spectrum. The findings highlight possible applications for these materials in the semiconductor industry and modern electronic gadgets. The optical properties assessment reveals that these materials have strong optical absorption and conductivity, making these compounds the best prospects for usage in solar cells. CsSiBr3’s lower band gap renders it the superior choice for light-emitting diode (LED) and solar cell applications. Our findings may provide a complete understanding for experimentalists to pursue additional research leveraging applications in LEDs, photodetectors, or solar cells.