Exploring thermoelectric materials for renewable energy applications: The case of highly mismatched alloys based on AlBi1-xSbx and InBi1-xSbx

The high throughput thermoelectric devices are considered promising futuristic energy source to control global warming and realize the dream of green energy and sustainable environment. The ability of the highly mismatched alloys (HMAs), to show the intriguing impact on the physical properties with controlled modifications, has extended their promise to thermoelectric applications. Here, we examine comprehensively the potential of the two prototypical HMAs such as AlBi1-xSbx and InBi1-xSbx for thermoelectric applications within density functional theory together with the Boltzmann transport theory. For comprehensive understanding, alloying of these materials has been performed over the entire composition range. From our calculations, we found, the replacement of Sb with Bi leads to a significant evolution in the energy band-gap and effective masses of the charge carriers that consequently deliver enhancement in thermoelectric response. Improvement of magnitude 1.25 eV and 0.986 eV has been respectively recorded in band-gaps of AlBi1-xSbx and InBi1-xSbx for the across composition alloying. Similarly, by the electronic-structure engineering of HMAs, thermoelectric properties such as, the Seebeck coefficients over Fermi-level were found to be improved from 82.90 μV/K to 107.52 μV/K for AlBi1-xSbx and 60.32 μV/K to 92.73 μV/K for InBi1-xSbx. As a result, the thermoelectric figure of merit (ZT) and power factor show considerable enhancement as a function of alloying composition for both alloys at room temperature. However, at a higher temperature, the thermal conductivity of these materials experience an exponential increase, results in lower ZT values. Overall, the observed evolution in the electronic structure and thermoelectric response for replacing Sb over Bi is significant in AlBi1-xSbx as compared to InBi1-xSbx. Hence, with the capability of significant and controlled evolution in electronic-structure and subsequent thermoelectric properties, HMAs particularly AlBi1-xSbx are believed potential candidates for thermoelectric applications.