Optimization of thermoelectric power factor in defect-engineered Bi$_{2}$Te$_{3}$ thin films

The figure-of-merit ZT, which is related to thermoelectric energy conversion, is largely dependent on the power factor ($S^{2}\sigma)$, the electronic part of ZT. Optimizing power factor has been technically challenging due to unfavorable coupling between electrical conductivity and Seebeck coefficient, hence ZT has been commonly improved by reducing lattice thermal conductivity. In this work, we optimize the power factor with simultaneous enhancement in the in-plane electrical conductivity and Seebeck coefficient by manipulating native defects (NDs) in Bi$_{2}$Te$_{3}$ thin films using energetic alpha particles irradiation. This nontrivial optimization leads to a high power factor and potentially improves ZT by reducing the thermal conductivity. The microscopic mechanisms achieved by the multiple roles of NDs will be discussed and our work will provide a new route to improve ZT of Bi$_{2}$Te$_{3}$-related thermoelectric materials.