Electronic Structure of In Se 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 Se 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 Se ( = 0, 0.11, and, 0.22), the Fermi level ( ) crossed over several bands in the conduction bands, which is an indication of the n-type metal-like behavior of In Se compounds. On the other hand, the band structure of In Se ( = 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 InSe and that between Se 4p and In 5p orbitals were seen for β-InSe compound. The dispersion of In 5s, In 5p and Se 4s, Se 4p orbitals is responsible for the electrical conductivity of InSe that is confirmed from DOS calculations as well. Moreover, the bonding natures of In Se materials have been discussed based on the electronic charge density map. Electron-like Fermi surface in InSe ensures the single-band nature of the compound. The efficiency of the In Se/p-Si heterojunction solar cells has been calculated by Solar Cell Capacitance Simulator (SCAPS)-1D software using experimental data of In Se thin films. The effect of various physical parameters on the photovoltaic performance of In Se/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 = 0.703 V, = 38.53 mA/cm, and FF = 83.48%. These entire theoretical predictions indicate the promising applications of In Se two-dimensional compound to harness solar energy in near future.