Here, f (ϵ k ) = 1/(e (ϵ k -ϵ F )/k B T + 1) is the Fermi-Dirac distribution function, v k = ∇ k ϵ k /ℏ the group velocity of a charge carrier in a given band, ϵ k the band energy at a given k-point, ϵ F the Fermi-energy (the chemical potential at T = 0 K), k B the Boltzmann constant, and T the temperature. This equation describes the steady-state distribution of charge carriers in an electric field, considering the acceleration of the charge by the field and the restoration of the distribution through collisions with phonons and impurities. The so-called relaxation time τ k describes the average time between these scattering events. In the crystalline phase of the polymer, we can neglect the influence of impurities and consider only scattering events with acoustic phonons, 82 using the deformation potential theory 105 to calculate the relaxation time along a crystal direction. The necessary parameters to assess the relaxation time can be determined by parabolic and linear fitting procedures. 106,107 Together with the band structure of the system and for a given temperature, one can calculate the conductivity as a function of the charge carrier concentration by varying the chemical potential (more details on the derivation and the numerical schemes can be found in eqn. S1-S11 of the SI).