High‐Performance Thermoelectric Devices Made Faster: Interface Design from First Principles Calculations

Abstract

The enormous progress achieved with high‐performance thermoelectric materials has yet to be implemented in high‐performance devices. The bottleneck for this is the material‐specific design of the interface between the thermoelectric material and the electrical connections, particularly identifying suitable contacting electrodes. This has mainly been empirical, slowing down device maturation due to the vast experimental space. To overcome this, an electrode pre‐selection method based on first‐principles electronic structure calculations of charged defect formation energies is established in this work for the first time. Such method allows to predict thermoelectric leg degradation due to impurity diffusion from the electrode into the thermoelectric material and formation of charge carrier traps, causing a majority carrier compensation and performance deterioration. To demonstrate the feasibility of this approach, the charged point defect formation energies of relevant metal electrodes with Mg2(Si,Sn) are calculated. Five hundred ten defect configurations are investigated, and the interplay between intentional doping and electrode‐induced point defects is predicted. These predictions are compared with Seebeck microprobe measurements of local carrier concentrations near the Mg2(Si,Sn)‐electrode interface and a good match is obtained. This confirms the feasibility of electrode screening based on defect formation energy calculations, which narrows down the number of potential electrodes and accelerates device development.