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This Half-Heusler compounds are currently considered promising photovoltaic (PV) and thermoelectric (TE) materials owing to their favorable electronic, optical, thermopower and electrical conductivity properties. Using first-principles density-functional theory (DFT) and many-body–based methods such as the GW approximation, Bethe–Salpeter equation (BSE), and electron–phonon interactions (EPI) [1, 2], we study the quasiparticle band structures, optical excitonic properties, and charge mobility of LiZnAs and ScAgC. These materials direct-band-gap semiconductors and both exhibit triply degenerate, loosely bound bright excitons (with binding energies in the range of 45–55 meV) at the main absorption peak 1. Furthermore, these excitons are highly localized (delocalized) in momentum (real) space, indicating the presence of Mott–Wannier–type excitons at the band gap 1. Next, the temperature-induced renormalization of the electronic states due to EPI is obtained within the non-adiabatic Allen–Heine–Cardona formalism 2. We then solve the Boltzmann transport equation (BTE), both iteratively and within multiple relaxation-time approximations (RTAs), to evaluate the carrier transport. Phonon-limited electron and hole mobilities computed using the linearized self-energy and momentum RTAs (SERTA and MRTA) are compared with the iterative BTE (IBTE) results 2. Finally, we obtain a spectroscopic limited maximum efficiency (SLME) in the range of ~31–32% at a thin-film thickness of ~0.4 µm 1, and a TE figure of merit (zT) in the range of ~0.8–1.0 (for bulk) and ~1–1.5 (for nanostructured samples) 2. These findings highlight the significant role of excitons in the solar energy absorption process and electron–phonon coupling in charge transport, and also suggest that both materials are highly suitable candidates for next-generation single-junction thin-film PV solar and TE devices.
(1) V. K. Solet and S. K. Pandey, Phys. Rev. Appl. 23, 064040 (2025).
(2) V. K. Solet and S. K. Pandey, Phys. Rev. B 113, 115203 (2026).