Our defects calculations suggest that it is possible to dope Y 2 Te 3 n-type under Y-rich conditions (Figure ) since the formation of acceptor-like native defects (V Y and Te Y ) is suppressed i.e., acceptor defects have high formation energy. In fact, under Y-rich conditions Y 2 Te 3 is found to be self-doped n-type with a free electron concentration of 1.0 × 10 20 cm -3 at T = 923 K. The relatively high electron concentration is due to the low formation energy of donor-like cation interstitials (Y i ), which reside at the vacancy sites in the ordered-vacancy structure of Y 2 Te 3 (Figure ). In addition, the generated electrons are free conduction electrons and not localized at mid-gap states that require temperature activation. The mid-gap states associated with V Te are occupied when E F,eq is located at ∼1.5 eV above the VBM.