Lithium Doping Effect for Enhancing Thermoelectric and Optoelectronic Performance of Co₂NbAl

Cobalt-rich Heusler compounds represent a very interesting family of Heusler alloys owing to their performance in spintronics and magnetic devices. The quaternary Heusler, created by swapping of an anti-atom site with an alkali element, improves the performance of physical properties for applications. In this study, the electronic structures and magnetic properties before and after substitution of Co by Li in the Co₂NbAl compound were investigated using ab initio computational calculations. Our findings revealed that substitution of Co antisites by Li destroys the half-metallic character of Co₂LiNbAl. Analysis of the band structures shows that the parent ternary Heusler compound is ferromagnetic half-metallic with a half-metallic gap (band gap in the minority channel) equal to 0.497 eV. Using the HSE06 approach substituting of Co by Li leads the material to change its behavior and becomes a semiconductor with a gap equal to 1.043 eV. The results of optical and thermoelectric properties such as absorption coefficient, reflectivity or thermo power, and figure of merit are very interesting in the optoelectronic field and encourage researchers to realize photovoltaic cells and thermoelectric generators with higher efficiency. These interesting features suggest that Co₂NbAl and LiNbAlCo Heusler compounds are good candidates for applications in spintronics and optoelectronics for commercial semiconductor industry.