Thermoelectric material can be used for energy harvesting that converting thermal energy into electricity. It also can be used as solid cooler by passing electricity thought the element. Many TE array device were manufactured and their performance were tested. Some of the TE device property is not consisted with others. Performance degradation of TE devices was observed. Impedance spectrum was proposed as the non-invasive diagnostic tool.

The impedance measurement was carried out on a single semiconducting element of N-type or P-type. Impedance data was measured over a range of dc bias and they were fitted with an equivalent RC circuit. The parameter value of the RC circuit was calculated.

The EIS data were measured for three different TE array devices over bias voltage ranged from – 1.0 V to 1.0 V and temperature ranged from room temperature to 90 oC. An equivalent circuit Rs (CPE-C) (R1-C1) (R2-C2) was found that is capable of described the EIS data of these samples over the bias voltage and temperature ranges. Values of these parameters were calculated. The EIS technique can be used as an analytic tool for the diagnosis of TE array.