To realize the predicted n-type TE performance of Y 2 Te 3 , it must be suitably doped with electrons and the free electron concentration must be tuned to optimize the performance. Whether a material can be optimally doped depends largely on the self-doping behavior of the native defects. The presence of high concentrations of acceptor-like defects will limit n-type doping due to the charge compensation by the holes created by the acceptor defects. Therefore, to probe whether Y 2 Te 3 can be doped n-type, we calculate the formation energies of native defects using first-principles calculations. The details of the defect calculations are provided in the Methods section.