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Half‐Heusler compounds with a 1 eV (1.7 eV) direct band gap, lattice‐matched to GaAs (Si), for solar cell application: A first‐principles study

A systematic theoretical study of the structural and electronic properties of new half‐Heusler compounds is performed to find the appropriate target key physical parameters for photovoltaic application. As a result, five ternary half‐Heusler compounds ScAgC, YCuC, CaZnC, NaAgO, and LiCuS are studied by density functional theory for potential applications in multi‐junction solar cells. The calculated formation enthalpies indicate that these materials are thermodynamically stable. Using state‐of‐the‐art modified Becke–Johnson exchange potential approximation, we find a direct band gap close to 1 eV ( ∼ 1.88 eV) for ScAgC, YCuC, CaZnC, NaAgO (LiCuS) being quasi‐lattice matched to GaAs (Si). In addition, the band offsets between half‐Heusler compounds and GaAs (Si) and their consequences for heterostructures are derived using the modified Tersoff method for the branch‐point energy. Furthermore, the elastic constants and phonon dispersion curves are calculated. They indicate the respective mechanical and dynamical stability of these half‐Heusler compounds.