Prof. Jiaqing He’s group has publishedtheir recent researching results of thermoelectrics on Advanced Functional Materials, depicting the technique thatutilizing modulation doping to significantly improved the thermoelectricperformance in BiAgSeS. This work was designed and dominated by Prof. He’sgroup, with the cooperation from Prof. Li Huang (SUSTC) and Prof. Lidong Zhao(Beihang University).

       Thermoelectricmaterials can directly create electrical power from heat and have thus drawngrowing research interest for decades. Materials withintrinsically low thermal conductivities represent an important series inthermoelectrics. However, a bottle neck was faced, when the intrinsic thermalconductivities for these materials approach the corresponding glass limits.Therefore, improving the electrical transport performance, namely, the powerfactor, seems to be one and the only feasible strategy. In this work, theyoriginally introduced modulation doping, a well-developedtechnique widely used in thin-film devicesin order to improve the electrical conductivity,into bulk materials for better thermoelectric performance.Experimentally, they constructed heterogeneous BiAgSeScomposites by incorporating pristine BiAgSeS grains with a certain volumefraction of BiAgSeS1-xClx(x=0.03 or 0.05) grains, and achieved improved power factor via simultaneouslyincreasing the carrier mobility and concentration in the notion of modulation doping. Consequently, they obtained a significantly enhanced power factor (87%higher than uniformly dopedsample with the same nominal composition at 823 K). The heterogeneous composite in this work is to facilitate charge carriertransport, thus very distinct to the mechanism normally adopted to strengtheninterface phonon scattering. Our finding creates new insights and sheds lighton further improvements on thermoelectric performance of a wide range ofthermoelectric materials simply via constructing heterogeneous composites withproper band alignments.