Electronic Structure of In_3- Se₄ Electron Transport Layer for Chalcogenide/p-Si Heterojunction Solar Cells

In this article, we perform density functional theory calculation to investigate the electronic and optical properties of newly reported In_3- Se₄ 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 In_3- Se₄ (x = 0, 0.11, and, 0.22), the Fermi level (E _F) crossed over several bands in the conduction bands, which is an indication of the n-type metal-like behavior of In_3- Se₄ compounds. On the other hand, the band structure of In_3- Se₄ (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 confirmed from DOS calculations as well. Moreover, the bonding natures of In_3- Se₄ 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 efficiency of the In_3- Se₄/p-Si heterojunction solar cells has been calculated by Solar Cell Capacitance Simulator (SCAPS)-1D software using experimental data of In_3- Se₄ thin films. The effect of various physical parameters on the photovoltaic performance of In_3- Se₄/p-Si solar cells has been investigated to obtain the highest efficiency of the solar cells. The optimized power conversion efficiency of the solar cell is found to be 22.63% with V _OC = 0.703 V, J _SC = 38.53 mA/cm², and FF = 83.48%. These entire theoretical predictions indicate the promising applications of In_3- Se₄ two-dimensional compound to harness solar energy in near future.