First-principles calculations of inherent properties of Rb based state-of-the-art half-Heusler compounds: promising materials for renewable energy applications

In the present work, we have studied structural, electronic, optical and thermoelectric properties of Rb based state-of-the-art materials RbYZ (Y = Be, Mg, Ca, Sr and Ba; Z = P, As, Sb and Bi) having 8 valence electron count (VEC) using density functional theory followed by solution of Boltzmann transport equation with constant relaxation time approximation. The exchange and correlation potential are described by the GGA of Wu and Cohen (GGA-WC); the Becke-Johnson approach modified by Tran and Blaha (TB-mBJ) has been used to model the exchange-correlation potential. The bandgap of these materials lies in the range of 0.201 eV-2.591 eV. The various optical parameters are comparable with the state-of-the-art photovoltaic materials. Thermoelectric properties have been computed at 300 K, 600 K and 900 K. At these temperatures lattice thermal conductivity have been computed using Slack's model. This detailed study shows that these compounds are promising for renewable energy applications.