Structure and thermoelectric properties of electrodeposited bismuth telluride thin films by controlling electrolyte temperature

To improve the thermoelectric performance of bismuth telluride (Bi 2 Te 3 ) thin film using electrodeposition, we investigated the effect of electrolyte temperature ranging from 10°C to 70°C. The thermoelectric properties including electrical conductivity, Seebeck coefficient and power factor were measured at room temperature in the in-plane direction. The structural properties were examined by scanning electron microscope and X-ray diffraction analysis. The maximum power factor of 1.3 μW/(K 2 ･ cm) was exhibited at a electrolyte temperate of 20°C. For further increasing the electrolyte temperature, the power factor linearly decreased because both the electrical conductivity and Seebeck coefficient decreased. The surface structure of the Bi 2 Te 3 thin films greatly changed when the electrolyte temperature was changed. The Bi 2 Te 3 thin films at lower electrolyte temperature (T < 30°C) exhibited dense structure while the thin films at higher electrolyte temperature (T > 50°C) exhibited dendrite structure and many deep apertures which caused a decrease in the thermoelectric performance.