Service Performance Prediction Based on Equivalent Circuit Model for Cosb3-Based Skutterudite Thermoelectric Device

The performance degradation is one of the most critical issues for the practical applications of thermoelectric (TE) devices. The structure evolutions at both TE material’s surface and electrode interfaces, as the primary causes of performance deterioration, exhibit complex temperature dependence and affect the device output correlatively, which makes prediction of service performance very difficult. Here, we proposed an equivalent circuit model (ECM) to quantitatively clarify the correlation between the structure evolution and device parameters (heat flow, internal resistance, output power, etc.), in which the metamorphic layer (ML) and TE matrix are divided into finite elements and the equivalent circuit is constructed by connecting them in series (or parallel) along (or perpendicular to) the heat flow. The simulation results show that, the volumetric effect give great impact on the device performance mainly due to the changes of the electrical and thermal conductivities of ML and the electrode interfacial resistivity. In addition, it is found that the formation of ML shall cause internal currents which decreases open circuit voltage and therefore deteriorate the output power. Taking CoSb3-based TE module as example, at early stage of service the performance degradation is mainly caused by the interfacial structure evolution, while the influence of surface sublimation becomes dominant in long-term service. The ECM simulation results are well verified with the aging experiments on the Ce0.9Fe3CoSb12 and Yb0.3Co4Sb12 single-leg devices, demonstrating effectiveness of ECM for the service performance evaluation and life-prediction of TE devices.