摘要： In this article, we perform density functional theory calculation to investigate the electronic and optical properties of newly reported In3?xSe4 compound using CAmbridge Serial Total Energy Package (CASTEP). Structural parameters obtained from the calculations agree well with the available experimental data, indicating their stability. In the band structure of In3?xSe4 (x = 0, 0.11, and, 0.22), the Fermi level (EF) crossed over several bands in the conduction bands, which is an indication of the n-type metal-like behavior of In3?xSe4 compounds. On the other hand, the band structure of In3?xSe4 (x = 1/3) exhibits semiconducting nature with a band gap of ～0.2 eV. A strong hybridization among Se 4s, Se 4p and In 5s, In 5p orbitals for In3Se4 and that between Se 4p and In 5p orbitals were seen for β-In2Se3 compound. The dispersion of In 5s, In 5p and Se 4s, Se 4p orbitals is responsible for the electrical conductivity of In3Se4 that is con?rmed from DOS calculations as well. Moreover, the bonding natures of In3?xSe4 materials have been discussed based on the electronic charge density map. Electron-like Fermi surface in In3Se4 ensures the single-band nature of the compound. The e?ciency of the In3?xSe4/p-Si heterojunction solar cells has been calculated by Solar Cell Capacitance Simulator (SCAPS)-1D software using experimental data of In3?xSe4 thin ?lms. The e?ect of various physical parameters on the photovoltaic performance of In3?xSe4/p-Si solar cells has been investigated to obtain the highest e?ciency of the solar cells. The optimized power conversion e?ciency of the solar cell is found to be 22.63% with VOC = 0.703 V, JSC = 38.53 mA/cm2, and FF = 83.48%. These entire theoretical predictions indicate the promising applications of In3?xSe4 two-dimensional compound to harness solar energy in near future.