  The discovery of novel materials for thermoelectric energy conversion has
potential to be accelerated by data-driven screening combined with
high-throughput calculations. One way to increase the efficacy of successfully
choosing a candidate material is through its evaluation using transport
descriptors. Using a data-driven screening, we selected 12 potential candidates
in the trigonal ABX2 family, followed by charge transport property simulations
from first principles. The results suggest that carrier scattering processes in
these materials are dominated by ionised impurities and polar optical phonons,
contrary to the oft-assumed acoustic-phonon-dominated scattering. Combined with
calculations of thermal conductivity based on three-phonon scattering, we
predict p-type AgBiS2 and TlBiTe2 as potential high-performance thermoelectrics
in the intermediate temperature range for low grade waste heat harvesting, with
a predicted zT above 1 at 500 K. Using these data, we further derive
ground-state transport descriptors for the carrier mobility and the
thermoelectric power factor. In addition to low carrier mass, high dielectric
constant was found to be an important factor towards high carrier mobility. A
quadratic correlation between dielectric constant and transport performance was
established and further validated with literature. Looking ahead, dielectric
constant can potentially be exploited as an independent tuning knob for
improving the thermoelectric performance.
