Improvement of thermoelectric performance of α-In2Se3upon S incorporation

Abstract

In this work, we have observed the enhancement of carrier concentration in α-In2Se3 at a specific S content. This enhancement results from avoiding the annihilation of defects, such as VIn and interstitial Ini acting as donors, via the rearrangement of both the cationic and anionic disorders. Therefore, there is a remarkable improvement in electrical conductivity (σ). For example, the sample α-In2S0.05Se2.95 perpendicular to the pressing direction (C┴) gives the highest σ value of 5.56 × 103 Ω−1 m−1 at 923 K, while the virgin α-In2Se3 gives only 9.17 × 102 Ω−1 m−1. In addition, there are dual effects on the lattice thermal conductivity (κL) resulting from the stabilization of the lattice structure caused by the rearrangement of defect disorder and the lattice distortion from the formation of defect SSe. Therefore, the lattice contribution (κL) in S-incorporated α-In2Se3 remains relatively high at high temperatures. As a consequence, we have improved the thermoelectric performance, achieving a ZT value of 0.67 for α-In2S0.05Se2.95 at 923 K, which is about 2.8 times that of virgin α-In2Se3 (ZT = 0.24 at C┴).