Tunable opto-electronic and thermoelectric response of alkali based half-Heusler semiconductors AMgN (A = Rb, Cs) for sustainable energy: A computational approach

The quick depletion of energy sources and the resulting environmental consequences can be wisely addressed by investigating effective and environmentally friendly materials that have the capacity to convert wasted energy into electricity. This work reports on the thermoelectric features investigations of half Heusler materials, AMgN (A = Rb, Cs). The semi-empirical Boltzmann theory is used alongside the full potential linearized augmented plane wave plus local orbital method (FP-LAPW + lo) to conduct the research. The modified Becke-Johnson (mBJ) exchange potential by Trans-Blaha, the parameterized generalized gradient approximation (GGA) by Perdew-Bruke-Ernzerhof (PBE), and the local density approximation (LDA) proposed by Perdew and Wang (PW) are used to integrate the exchange-correlation energy/potential portion. The electronic band structure results show that RbMgN exhibits a direct energy band gap of 1.35 eV and CsMgN has an indirect energy band gap of 0.66 eV. The optical outcomes reveal that both compounds have absorption in the ultraviolet range, making them suitable for optoelectronic applications. The thermal conductivity, See-beck coefficient, electrical conductivity, power factor, and figure of merit (ZT) are calculated at 300 K, 700 K, and 1200 K temperatures in order to understand their thermoelectric nature. According to our computations, 300 K was the ideal value for the Seebeck coefficient for both materials. The Seebeck coefficient values for RbMgN were found to be better than those for CsMgN. The materials under consideration have the ZT parameter (ZT similar to 1) calculations for both AMgN (A = Rb, Cs) revealing that all these materials could be useful for the thermoelectric applications and used as alternative green energy resources.