Preparation of Bismuth Telluride Films with High Thermoelectric Power Factor.

Highly conductive n-type Bi2Te3 films on a flexible substrate were prepared via electrodeposition followed by a transfer process using an adhesive substrate. The growth of the Bi2Te3 crystals was precisely controlled by an electrochemical deposition potential (Vdep), 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 Bi2Te3 film prepared under Vdep 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 Bi2Te3 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 Bi2Te3 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 ΔT = 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.