We report thermoelectric characterization of Bi2-xSb xTe3 (x = 0.5, 1.0, and 1.5) synthesized by a solvothermal method using DMF as solvent. For Bi2Te3, the size of the edge and thickness of the hexagonal nanoplatelets are 200-250 nm and 20-25 nm, respectively. Bi2Te3 nanosheets appear to grow epitaxially from the surface of the Te tubes, which forms in the first step and acts as the template for the formation of the nanostructure. Upon doping with Sb, the morphology of Bi1.5Sb0.5Te3 changes to a cluster of nanoparticles with the size of ∼100 nm. The morphology of Bi 0.5Sb1.5Te3 consists of mainly nanoplatelets with a size of less than 100 nm and warped nanosheets growing along the Te tube. The nominal composition of Bi2Te3 mats containing sheet-tubes shows a negative thermopower of ca. -94 μV/K at 280 K, whereas Bi0.5Sb1.5Te3 shows a positive thermopower of ca. 200 μV/K at 280 K.