The effect of Cr buffer layer thickness on voltage generation of thin-film thermoelectric modules

The effect of Cr buffer layer thickness on the open-circuit voltage generated by thin-film thermoelectric modules of Bi0.5Sb1.5Te3 (p-type) and Bi2Te2.7Se0.3 (n-type) materials was investigated. A Cr buffer layer, whose thickness generally needs to be optimized to improve adhesion depending on the substrate surface condition, such as roughness, was deposited between thermoelectric thin films and glass substrates. When the Cr buffer layer was 1 nm thick, the Seebeck coefficients and electrical conductivity of 1 mu m thermoelectric thin films with the buffer layers were approximately equal to those of the thermoelectric films without the buffer layers. When the thickness of the Cr buffer layer was 1 mu m, the same as the thermoelectric films, the Seebeck coefficients of the bilayer films were reduced by an electrical current flowing inside the Cr buffer layer and the generation of Cr2Te3. The open-circuit voltage of the thin-film thermoelectric modules decreased with an increase in the thickness of the Cr buffer layer, which was primarily induced by the electrical current flow. The reduction caused by the Cr2Te3 generation was less than 10% of the total voltage generation of the modules without the Cr buffer layers. The voltage generation of thin-film thermoelectric modules could be controlled by the Cr buffer layer thickness.