Insights into interfacial thermal conductance in Bi2Te3-based systems for thermoelectrics

The thermal resistance at the interface between thermoelectric materials and metallic electrodes plays an important role in the energy conversion efficiency of thermoelectric devices. This is especially prevalent in the Bi2Te3-based flexible thermoelectric generators for wearable electronics, where the temperature difference between the human skin and the ambient environment is small. In this work, we study the phonon interfacial thermal conductance (ITC) in Bi2Te3/Au and Bi2Te3/Cu, by using non-equilibrium molecular dynamics simulations. It is found that the ITC in Bi2Te3/Cu is 3-fold higher than that in Bi2Te3/Au. We explore the underlying mechanism and find that both the stronger interfacial van der Waals interaction and phonon coupling contribute to the higher ITC in Bi2Te3/Cu. We further show that the ITC of Bi2Te3/Au and Bi2Te3/Cu can be tuned effectively by mechanical strain. Remarkably, a 0.04 compressive strain leads to the increase in ITC of Bi2Te3/Au and Bi2Te3/Cu by 120% and 62%, respectively. Our work not only provides physical insights into the ITC in thermoelectric devices, but is also useful in designing the Bi2Te3-based thermoelectric generators with enhanced energy conversion efficiency.