Thermal and electrical conductivity of single crystalline kesterite Cu2ZnSnS4

Abstract

For single crystalline sulfur-based kesterite Cu2ZnSnS4 the electrical and thermal conductivity are measured from 20 K to 320 K. The electrical conductivity decreases exponentially with decreasing temperature. The temperature dependence can be assigned to Mott-variable-range-hopping, an electrical transport process within an impurity band in the band gap. With the 3ω-method a thermal conductivity room temperature value of 5.1 ± 0.5 Wm−1K−1 and a maximal value of 8.0 ± 0.5 Wm−1K−1 at 100 K are found. Phonon-phonon-umklapp-scattering can explain the high temperature range from 100 K to 320 K. The low temperature values of the thermal conductivity are dominated by the temperature-dependence of the specific heat capacity, due to a reduced phonon-mean-free-path, owing to phonon-impurity-scattering.