Exploring In$_2$(Se$_{1-x}$Te$_x$)$_3$ alloys as photovoltaic materials

TL;DR

This study investigates In$_2$Se$_3$ and its Te-alloys as photovoltaic materials, demonstrating tunable band gaps and high absorption coefficients suitable for solar cell applications through experimental growth and theoretical calculations.

Contribution

It provides new insights into the electronic and optical properties of In$_2$Se$_3$ and its Te-alloys, including band gap tuning and absorption characteristics, expanding their potential for optoelectronic devices.

Findings

Band gap of 1.84 eV for In$_2$Se$_3$ matches experimental data.

Te incorporation tunes the band gap from 1.84 eV to 1.23 eV.

High absorption coefficient comparable to conventional semiconductors.

Abstract

In$_2$Se$_3$ in the three-dimensional (3D) hexagonal crystal structure with space group $P6_1$ ($\gamma$-In$_2$Se$_3$) has a direct band gap of $\sim$1.8 eV and high absorption coefficient, making it a promising semiconductor material for optoelectronics. Incorporating Te allows for tuning the band gap, adding flexibility to device design and extending the application range. Here we report the growth and characterization of $\gamma$-In$_2$Se$_3$ thin films, and results of hybrid density functional theory calculations to assess the electronic and optical properties of $\gamma$-In$_2$Se$_3$ and $\gamma$-In$_2$(Se$_{1-x}$Te$_x$)$_3$ alloys. The calculated band gap of 1.84 eV for $\gamma$-In$_2$Se$_3$ is in good agreement with data from the absorption spectrum, and the absorption coefficient is found to be as high as that of direct band gap conventional III-V and II-VI semiconductors. Incorporation of Te in the form of $\gamma$-In$_2$(Se$_{1-x}$Te$_x$)$_3$ alloys is an effective way to tune the band gap from 1.84 eV down to 1.23 eV, thus covering the optimal band gap range for solar cells. We also discuss band gap bowing and mixing enthalpies, aiming at adding $\gamma$-In$_2$Se$_3$ and $\gamma$-In$_2$(Se$_{1-x}$Te$_x$)$_3$ alloys to the available toolbox of materials for solar cells and other optoelectronic devices.