Estimation of Maximum zT in Cu₃SbSe₄ for Different Starting Materials Content

Cu₃SbSe₄ is considered a promising thermoelectric material because of its large effective mass and low thermal conductivity, originating from its unique lattice structure. However, Cu₃SbSe₄ has intrinsically low carrier concentration and relatively high electric resistance which limit performance. Recently, a zT improvement in Cu₃SbSe₄ was reported where doping/precipitation is controlled by changing the content of the starting materials. However, the effect of these changes in starting content on electronic band structures has not been studied. Here, we investigate how the change in starting materials content (x varying from 6 to 20) affects band parameters like density-of-states effective mass (m_d^*), non-degenerate mobility (µ₀), weighted mobility (µ_W), and B-factor using the Single Parabolic Band (SPB) model. For x greater than 8, precipitation of the secondary phase (CuSe) was observed, and the band parameters changed differently for x greater than 8. The m_d^* increases up to x = 8 and then rapidly decreases for x > 8. For µ₀, an overall decrease is observed for increasing x, but the rate of decrease is suppressed for x > 8. The µ_W reaches the maximum at x = 8. As x increases, the experimental lattice thermal conductivity also increases, especially for x > 8. Therefore, the B-factor, which is directly related to the theoretical maximum zT, becomes maximum at = 8. Hence the SPB model predicts a maximum zT of 0.0484 for x = 8 at 300 K, which is 15.5% higher than the experimental zT of 0.0419, which can be achieved by tuning the Hall carrier concentration to 4.44