Electrodeposition of bismuth telluride thermoelectric films from a nonaqueous electrolyte using ethylene glycol

Ethylene glycol was studied as an electrolyte for the electrodeposition of thermoelectric bismuth telluride films by cyclic voltammetry, rotating ring disk electrode and electrochemical quartz crystal microbalance (EQCM). The reduction of both Bi3+ and Te4+ ions proceeds in one step without the formation of intermediates at potentials more negative than +0.2 V and +0.55 V vs. SHE, respectively. The diffusion coefficients and the rate constants for reduction were found to be similar for Bi and Te. Stoichiometric Bi2Te3 films with a uniform composition profile were obtained from solutions containing up to 1 M of Bi(NO3)3 and TeCl4, at current densities up to 5 A dm−2 (∼102 μm h−1). Both p- and n-type bismuth telluride films could be obtained, as confirmed by Seebeck coefficient measurements.

► New electrolyte for BixTey thermoelectric electrodeposition using ethylene glycol.
► One-step reduction/oxidation for both Bi3+/Bi and Te4+/Te.
► Te reduction: monolayer forms prior to bulk deposition (on Pt).
► Concentrated solutions (up to 1 M), highest growth rate (up to 100 μm h−1) to date.
► Both p- and n-type Bi2Te3 can be prepared from the same electrolyte.