Optoelectronic and thermoelectronic properties of 3d, 4d, and 5d based semiconductor half-Heuslers (Ni/Pd/Pt)ScSb with narrow bandgap

Abstract

Based on DFT-GGA, we investigate the structural, optoelectronic, and thermoelectronic properties of half-Heusler alloys TScSb (T = Ni, Pd, Pt). The optimizations confirm that TScSb are structurally stable in nonmagnetic phase with FCC (F4‾3m; C1b; No. 216). Also, the ground state, formation and cohesive energies show that TScSb are chemically stable. The elastic parameters confirm that TScSb are mechanically stable and are ductile. Debye temperature decreases (ƟD = 410.8, 328.5, 302.1 K) for T = Ni, Pd, Pt. TScSb exhibit semiconductor nature with indirect Γ–X (T = Ni, Pd) and direct Γ (T = Pt) narrow bandgap (EBG = 0.277, 0.300, 0.587 eV), respectively. The calculated optoelectronic properties show that TScSb have high absorption and low reflectivity in VL and low UV ranges. At constant concentration, Seebeck coefficient S decreases with an increase in temperature, and maximum S is obtained in n-type (Smax = 1840, 2270, 2550 μV/K) for T = Ni, Pd, Pt, respectively. TScSb alloys give similar figure of merit (ZT = 1.000) at T < 100 K corresponding to their Smax. Therefore, the chemical and mechanical stability along with narrow semiconductor bandgap, high absorption, and ideal ZT make half-Heusler alloys TScSb more suitable materials for many optoelectronic and thermoelectronic applications.