Structure And Thermoelectric Properties Of Layered InSe-Based Semiconductors

Thermoelectric(TE) material is one type of energy materials which enable a direct conversion between heat and electricity through the motion of internal carrier within solids. In recent years indium selenides have been paid increasing attention due to their intrinsic structural characteristics, including phases, crystal structures and structural imperfection.In this work, we have synthesized Sn-doped InSe Snx(x=0-0.02) alloys by melting along with spark plasma sintering(SPS) and found that the defect Sn In+, which acts as a donor, is the main species to reduce the lattice thermal conductivity(κL) and improve the thermoelectric performance, due to the preferential occupation of Sn in the In sites. However, this enhancement is limited because of the formation of an intermediate band in the middle of the bandgap, which acts as an annihilation center for electrons and holes. As a consequence, we attain the highest ZT value of 0.23 for InSe Snx(x=0.01) at 830 K, which is about 2.9 times that of Sn-free InSe.Because of its active chemical properties and small atomic radius, element lithium is an ideal intercalation candidata into the InSe-based layered materials. In this work, the Li+ ions which come from CH3 COOLi aqueous solution is doped into the layered InSe compounds via chemical diffusion method at a given temperature, and the optimal diffusion temperature and time were directly determined by the optimized electrical conductivity and carrier concentration. The results show that InSe Lit with the diffusion time t=32h has the best thermoelectric performance with the maximum ZT value of 0.14 at 830 K, which is about 2 times that of intrinsic InSe.