First-principles assessment of thermoelectric properties of CuFeS2

Composed of inexpensive and naturally abundant elements, the chalcopyrite mineral CuFeS2 has received attention as a potentially useful thermoelectric. We use first-principles electronic structure and Boltzmann transport theory calculations to investigate thermoelectric properties of n-doped CuFeS2. We find that energy-dependent carrier lifetimes that are inversely proportional to the electronic density-of-states are crucial for reproducing experimental data on the transport properties, including the measured values of the Seebeck coefficient, alpha. The heavy-effective-mass conduction band promotes high values of alpha, but it also leads to low mobility due to strong electron-acoustic-phonon scattering. Low mobility forces one to rely on high carrier concentration to achieve high conductivity, which decreases alpha and limits the achievable power factor. Our calculations predict that ideally doped CuFeS2 that has been nanostructured to an average grain size d approximate to 20 nm can attain thermo-electric figures of merit zT = 0.25 to 0.8 for T = 300 to 700 K, respectively, due to a reduction in the lattice thermal conductivity. Published under license by AIP Publishing.