Designing high-performance infrared optoelectronic materials: indium-site substitution in LiInSe2 with Al, Ga, Sn, and Sb.

In this study, we employed first-principles calculations based on density functional theory to systematically evaluate the impact of substituting Al, Ga, Sn and Sb atoms into LiInSe2 crystals with R3m and I41/amd space groups. By adjusting the doping ratios of these elements, we analyzed their effects on the optoelectronic properties of LiInSe2. The results reveal that Al doping reduces the formation energy in the I41/amd structure, indicating easier synthesis under conventional conditions. Moreover, Al incorporation increases the bandgap, thereby raising the excitation energy required for electronic transitions. In contrast, Ga, Sn and Sb dopants tend to increase the formation energy while narrowing the bandgap. Further analysis identified four effective doping pathways in the R3m structure, all exhibiting potential for enhanced optoelectronic performance. Notably, Sb doping-despite its higher formation energy and reduced bandgap compared to the intrinsic structure-significantly enhances the optical absorption response in 1.65-3.00 eV. The structural modifications induced by Al, Ga, and Sb doping contribute to improved crystal stability and broadened spectral response, underscoring the strong potential of these materials for infrared detector applications.