Fabrication and evaluation of a flexible thermoelectric device using metal thin films

The purpose of this work is to fabricate and evaluate a flexible thermoelectric (TE) device. Because of its flexibility, it is expected that application field of the TE device will be enlarged. The device consists of p and n-type thin films placed between 2 polyimide sheets, and it can generate electricity from temperature difference (ΔT_out) applied between the outer surfaces of the device. The ΔT_out is transformed into in-plane temperature difference (ΔT_in), which can be utilized for thermoelectric power generation by the p-n couple. The ΔT_in was measured as 16.7 K when ΔT_out was 57.8 K, being in good agreement with calculated value by Finite Element Method. Calculations revealed that the use of TE material with high power factor is effective, and low thermal conductivity will be not so important for this device performance. Chromel as p-type and constantan as n-type was, therefore, selected for the flexible TE device. The device composed of 9 pairs of the films was fabricated by RF-sputtering-method. The device could generate maximum output of 144 nW at ΔT_out = 28.6 K in measurement. According to the calculation, maximum out of 114 nW at ΔT_out = 28.6 K was predicted, being in good agreement with measured value.