The role of edge-oxidized graphene to improve the thermopower of p-type bismuth telluride-based thick films

Edge-oxidized graphene-dispersed Bi_0.4Sb_1.6Te₃ (EOG/BST) thick films are fabricated by the hand-printing of EOG/BST paste followed by a heat-treatment process. Fabricated EOG/BST thick films are approximately 200 μm thick, and the EOGs in the film are dispersed rather than agglomerated but also appear to connect the separated BST grains. A 2 wt% EOG/BST thick film shows a maximum thermopower of 0.00206 W/mK², which is approximately 1.7 times higher than the output of 0.00133 W/mK² of BST film without EOG. The improved thermopower stems from the EOG, which provides rapid carrier-transport and an increase in the electrical conductivity of the BST film. It has been found that the edge-surface of EOG is chemically bonded with Bi, Te and Sb via interfacial oxygen atoms and the perfect graphite (sp²) structure of the EOG facilitates rapid movement of the carriers. The carrier mobility of 2 wt% EOG/BST film sample was improved by about 1.75 times without sacrificing the carrier density compared to that of BST film. These results indicate a promising means of using EOG to enhance the electrical properties of thermoelectric thick films, which can be utilized in active coolers and in wearable power generators.