The effect of Al-, Ga-, and In-doping on the thermoelectric (TE) properties of Cu3SbSe4 has been comparatively studied on the basis of theoretical prediction and experimental validation. It is found that tiny Al/Ga/In substitution leads to a great enhancement of electrical conductivity with high carrier concentration and also large Seebeck coefficient due to the preserved high band degeneracy and thereby a remarkably high power factor. Ultimately, coupled with the depressed lattice thermal conductivity, all three elements (Al/Ga/In) substituted samples have obtained a highly improved thermoelectric performance with respect to undoped Cu3SbSe4. Compared to the samples at the same Al/In doping level, the slightly Ga-doped sample presents better TE performance over the wide temperature range, and the Cu3Sb0.995Ga0.005Se4 sample presents a record high ZT value of 0.9 among single-doped Cu3SbSe4 at 623 K, which is about 80% higher than that of pristine Cu3SbSe4. This work offers an alternative approach to boost the TE properties of Cu3SbSe4 by selecting efficient dopant to weaken the coupling between electrical conductivity and Seebeck coefficient.
Keywords: Al/Ga/In doping; Cu3SbSe4; carrier concentration; decoupling; high band degeneracy; thermoelectric properties.