Flexible screen printed thermoelectric generator with enhanced processes and materials

This paper presents the fabrication and testing of bismuth tellurium (Bi1.8Te3.2) - antimony tellurium (Sb2Te3) based flexible thermocouples using screen printing technology for energy harvesting application. In this study, planar screen printed thermoelectric generators (TEGs) with three different printing processes were developed and coiled up to test. All thermocouples were printed on a flexible polyimide substrate. The dimension of each planer thermoleg is 20 mm × 2 mm while the thickness varied from 70.5 μm to 78 μm. The thermoelectric performance of TEGs using different binder systems A and B were investigated. For TEGs with binder A, the calculated Seebeck coefficient of a single thermocouple was in the range of 193-227 μV/K. At a temperature difference of 20 °C, the optimized power was 142 nW contributed by the cold isostatic pressed TEG with SbTe electrodes. Binder system B with lower viscosity was applied and proved to be able to decrease the resistivity of BiTe thick film, which increased the power factor (α2ρ). The power output of such coiled-up device increased to 444 nW with the same temperature difference. Higher output power could be realized by rolling up more planar thermocouples electrically connected. This work demonstrates that the low-cost screen printing technology and low-temperature curing materials are promising for the fabrication of flexible TEGs. Binder system that could help to generate a denser film was important to BiTe and SbTe based screen printable thermoelectric materials.