An effective method of evaluating the device-level thermophysical properties and performance of micro-thermoelectric coolers

Despite the success of achieving thermoelectric materials with high figure of merit, precisely evaluating the performance of micro-thermoelectric coolers remains challenging at the microdevice level because of various interfacial effects and device construction. This study develops a method for the effective evaluation of the device-level thermophysical properties capturing various interfacial and size effects, and establishes a three-dimensional numerical model to evaluate the cooling performance of micro-thermoelectric coolers. The model is validated by the reported experimental data. The impact of interaction between boundary and size effects is captured in the investigation of Seebeck coefficient, thermal conductivity and electricity resistivity of the thermoelectric materials at the device-level. Contact resistances are also considered in analyzing the cooling performance. Results indicate that the device-level figure of merit decreases by 5-18.1% with decreased thermoelectric element thickness from 20 μm to 5 μm. The boundary effects considerably weaken the cooling performance of the microdevice, and a higher heat flux corresponds to a greater impact of boundary effects. Cooling temperature increases by 6.1 K due to the boundary effects when heat flux is 300 W/cm2, while the temperature difference decreases by 17.1%. Finally, the three-dimensional numerical model is performed to evaluate the cooling performance and optimal working condition of the micro-thermoelectric cooler. At heat flux of 300 W/cm2 and 200 W/cm2, the minimum cold side temperatures of 310.7 K and 287.3 K are predicted to be achieved at 11 μm/20 mA (Hte/I), 15 μm/16 mA, respectively.