Abstract
Thermoelectric generation devices are able to convert waste heat into electricity. A typical thermoelectric module consists of paired p- and n-type semiconductor pellets that were sandwiched in between two ceramic plates. Generally, these tiny pellets are joined to metallic conductors on the ceramic plates by soldering. The whole fabrication process including pellet dicing, barrier plating and electrode soldering indeed is very time-consuming and costly. In this study, we present a printing-based process to prepare bismuth telluride thick films on a flexible substrate and demonstrate a solder-free process to make a generation module by connecting thermoelectric film and metallic electrode. Bismuth telluride based compounds were ground into fine powders and mixed with organic binders and solvent. The mixture was coated on a substrate by screen-printing and subsequently sintered using a hot-press technique. The p-type Bi-Sb-Te film exhibits a thermoelectric power factor of 11.3 μW/cmK2 at room temperature. To form a thermoelectric module, the contacting electrodes were directly joined to the printed film by forming a layer of intermetallic compound at the contact region through adjustment of sintering pressure and temperature. The thick film module can achieve matching load output power of 9.7 μW under a temperature difference of 17.7 K, and have the TE efficiency factor about 0.63 μW/cm^2∙K^2. The effect of film and contact properties on the performance of thermoelectric modules will be modeled and experimentally evaluated.