a b s t r a c t The optimization of the deposition process of n-type Bismuth Telluride and p-type Antimony Telluride thin films for thermoelectric applications is reported. The films were deposited on a 25 mm-thick flexible polyimide (kapton) substrate by co-evaporation of Bi and Te, for the n-type element, and Sb and Te, for the p-type element. The evaporation rate of each material was monitorized by an oscillating crystal sensor and the power supplied to each evaporation boat was controlled with a PID algorithm in order to achieve a precise user-defined constant evaporation rate. The influence of substrate temperature (in the range 240–300 C) and evaporation rates of Bi, Te and Sb on the electronic properties of the films was studied and optimized to obtain the highest Seebeck coefficient. The best n-type Bi 2 Te 3 films were deposited at 300 C with a polycrystalline structure, a composition close to stoichiometry, electrical resistivity w20 mU m and Seebeck coefficient À195 mV/ C. The best p-type Sb 2 Te 3 films were deposited at 240 C, are slightly Te-rich, have electrical resistivity w20 mU m and Seebeck coefficient þ153 mV/ C. These high Seebeck coefficients and low electrical resistivities make these materials suitable for fabrication of Peltier coolers and thermopile devices.