With n-type doping, the absolute Seebeck coefficients of Bi 2 SO 2 and Bi 2 SeO 2 are predicted to decrease monotonically with n between n = 10 17 -10 20 cm -3 , from 600 to 100 µV K -1 , above which we predict a slower decrease to |S| ≈ 50 µV K -1 . On the other hand, the large intrinsic n of Bi 2 TeO 2 results in |S| < 200 µV K -1 at low n with a peak S = -226 µV K -1 at n ≈ 10 19 cm -3 and a fall to comparable |S| to Bi 2 SO 2 and Bi 2 SeO 2 at n = 10 21 cm -3 .