Recently, the chair professor He Jiaqing of the Department of Physics of Southern University of Science and Technology has made important progress in the research on energy conversion of thermoelectric materials. The relevant results are titled "Top-ranking high performance in n-type Bi2Te3 based thermoelectric materials" in the field of energy and environment. The journal Energy & Environmental Science is published online. This is the He Jiaqing team's latest work published in the journal after following the research work of "Efficient Waste Heat Power Generation Based on Low-cost PbS-based Thermoelectric Materials" in January this year.
At present, more than 60% of the energy in the energy utilization system is discharged into the environment in the form of waste heat, of which more than 50% of the waste heat is low-temperature (<600k) and low-quality waste heat that is difficult to recycle. Thermoelectric materials have attracted widespread attention because of their ability to directly convert thermal energy and electrical energy, and can effectively recover and utilize low-quality waste heat in the system. In practical applications, two types of p-type and n-type thermoelectric semiconductor materials are required to form a thermoelectric device. The better the matching between the two types of thermoelectric semiconductors, the higher the thermoelectric conversion efficiency of the thermoelectric device made in theory.
As the only thermoelectric material that is widely commercialized as refrigeration around room temperature, Bi2Te3 based thermoelectric material is a very potential material that can be used for low-quality waste heat recovery and is environmentally friendly. The performance of p-type Bi2Te3-based thermoelectric materials is extremely high, but the lack of corresponding high-performance n-type materials limits the commercial application of its thermoelectric devices to a certain extent. The team of He Jiaqing compounded excessive Te element in n-type Bi2Te3 material, melted the Te element through sintering, and introduced dislocation array in the matrix. On the one hand, the dislocation array enhances the material's preferred orientation and optimizes the mobility; on the other hand, the structural change causes the material deformation activation energy to fluctuate, thereby forming an energy potential well in the conduction band, localizing low-energy electrons, and effectively improving Seebeck Coefficient, which in turn significantly increases the power factor.
On this basis, through the Sb compound doping, the carrier concentration is further optimized, and a multi-scale nano-scattering mechanism is simultaneously constructed, so that dislocation arrays, lattice distortions, edge dislocations, and point defects coexist in the material. Reduce lattice thermal conductivity. In addition, the research team prepared thermoelectric power components consisting of Bi1.8Sb0.2Te2.7Se0.3 +15 wt% Te n-type thermoelectric legs and Bi0.5Sb1.5Te3 p-type thermoelectric legs, which can achieve 6.6% of energy The conversion efficiency has broken the current record of the conversion efficiency of Bi2Te3-based thermoelectric devices.