Preparation of Bismuth Telluride Films with High Thermoelectric Power Factor

Highly conductive n-type Bi 2 Te 3 films on a flexible substrate were prepared via electrodeposition followed by a transfer process using an adhesive substrate. The growth of the Bi 2 Te 3 crystals was precisely controlled by an electrochemical deposition potential ( V dep ), which was critical to the preferred orientation of the crystal growth along the (110) direction and thus to the properties of a flexible thermoelectric generator (FTEG). A Bi 2 Te 3 film prepared under V dep of 0.02 V showed high electrical conductivity (691 S cm –1 ) with a maximum power factor of 1473 μW m –1 K –2, which is the highest among the Bi 2 Te 3 films prepared by the electrodeposition methods. As-prepared FTEG was bendable, showing only a small resistance change after 300 repeated bending cycles. Combined with the n-type Bi 2 Te 3 FTEG, a prototype p-n-type flexible thermoelectric (pn-FTEG) was prepared using p-type poly(3,4-ethylene dioxythiophene)s. The pn-FTEG (5-couples) generated an output voltage of 5 mV at Δ T = 12 K with high output power of 56 nW (or 105 nWg –1 ). These results indicate that the FTEG can reproducibly work well in a bent state and has high application potential for harvesting thermal energy from curved sources such as human body temperature.