The calculated electronic band structures and DoS of π SnS and SnSe (Fig. † ) are comparable to previous studies and yield direct bandgaps of E g = 1.61 and 1.28 eV that are an excellent match to experimental measurements and previous calculations. The σ , S and κ el of the π phases were calculated as a function of temperature and an extrinsic carrier concentration n ("doping level") by solving the electron BTE with energy-and monentum-dependent electron scattering rates from four scattering processes common to semiconductors. With this approach, we estimate per-state electron lifetimes, which is an improvement on previous computational studies that have determined the σ and κ el with respect to an unknown, fixed or state-independent relaxation times. The doping level is a key parameter for optimising the electrical properties of semiconductor thermoelectrics. Pnma SnS and SnSe can be both p-type (hole) and n-type (electron) doped at n up to 4 × 10 19 cm -3 . 45,46 Fig. shows the calculated σ , absolute |S|, PF S 2 σ and κ el of the π and Pnma 36,37 phases of SnS and SnSe for p-and n-type doping with n = 10 16 -10 20 cm -3 at T = 700 K. This temperature was chosen to be well below the high-temperature Pnma → Cmcm phase transitions in orthorhombic SnS and SnSe (T = 878/807 K 71 ).