Bi2Te3-based alloys are well-known as the excellent thermoelectric property at room temperature. However thermoelectric figure of merit of binary Bi2Te3 is limited to apply various categories. Ternary compound Bi2(Te-Se)3 is easy to control than binary compound Bi2Te3 and improve Seebeck coefficient. Several techniques have been used for preparation of Bi2(Te-Se)3 film such as physical vapor deposition(PVD), chemical vapor deposition(CVD) and pulsed laser deposition, etc. However the techniques have disadvantages such as high production cost and slow deposition rate. By comparison, electrodeposition have advantages such as control thickness of thin film, cost and deposition rate.
Pulsed electrodeposition of electrodeposition will be able to control the parameaters such as on/off time, pulse wave form average charge densities. And so The morphology and thermoelectric properties of the Bi2(Te-Se)3 thin films can be adjusted in a wide range. We pulse-electrodeposited ternary Bi2(Te-Se)3 thin film in order to control the composition and increase thermoelectric property. The electrolyte for the deposition was an aqueous solution containing 10 mM Bi3+, X mM HTeO2+ (X=9.5, 9.7), Y mM SeO32- (Y=0.5, 0.3), and 1.5 M HNO3 using Bi(NO3)35H2O, TeO2 and Na2SeO3 as the raw materials. The working electrode was gold-coated silicon. Opposite to the working electrode, a Pt sheet was used as counter electrode. While saturated calomel electrode (SCE) was used as reference electrode. Measurements are performed on as-deposited as well as annealed Bi2(Te-Se)3 thin film at 50℃, 100℃, 150 and 200℃ for 30min. The films deposited with pulsed deposition technique show higher Seebeck coefficients and power factros than those deposited with the DC deposition method. For pulsed deposited films, Seebeck coefficients up to -115.66 μV/K are achieved with power factors of about 2829.75 μW/mK2 at room temperature.
To improve thermoelectric properties of Bi2(Te,Se)3 thin film by pulse-electrodeposition at room temperature, we can add Cu in Bi2(Te,Se)3 solution by the change of doped Cu weight. The way of electrodeposition was almost exactly the same as how pulse-electrodeposited Bi2(Te,Se)3 thin film. So, we observed thermoelectric properties of Cu doped Bi2(Te,Se)3 thin film. The Seebeck coefficients is ?101.2 μV/K and power factors is 1412.6 μW/mK2 at room temperature.