Carrier transport model and novel design for micro thermoelectric generator with enhanced performance

The carrier transport processes in thermoelectric materials are significantly correlated with the performance of thermoelectric devices (TEs), which is modeled in this study considering the drift-diffusion equation with thermoelectric contributions for detailing the effects of carrier transport on the yielded current density. A micro thermoelectric generator (μTEG) with boron and arsenic being respectively doped into Si_0.7Ge_0.3 for p-type and n-type thermoelectric materials is employed as the study case by the three-dimensional numerical simulation to reveal the effects of doping concentrations on the thermoelectric performance. Based on the simulation results a novel μTEG design that incorporates PN junctions to extract minority carriers to reduce the recombination rates of electrons and holes is proposed. The performances for conventional and the present novel μTEGs at different temperature differences are compared. The results show that there is an optimal doping concentration for the conventional μTEG to peak the output power and the thermoelectric conversion efficiency. In particular, the novel μTEG reveals a significant improvement of thermoelectric efficiency by approximately 20% as the hot-end temperature is above 900 K. The transport of minority carriers by the PN junctions demonstrates the expected effects through the analysis on the vector distribution of minority carrier current density.