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

Edge-oxidized graphene-dispersed Bi0.4Sb1.6Te3 (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 mu m 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/mK(2), which is approximately 1.7 times higher than the output of 0.00133 W/mK(2) 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 (sp(2)) 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.