The THz conductivity at 1 THz is 0.26 S cm -1 in PTI-LiBr and 0.07 S cm -1 in PTI-IF, exceeding the macroscopic electrical measurements by about six and eight orders of magnitude, respectively (Figure ). Hence, the conductivity inside the single crystals of PTI-LiBr and PTI-IF is much higher (Figure , c) (i)) than in the films. This is most likely due to inefficient charge transport between loosely packed PTI crystals (Figure , c) (ii)) in the macroscopic films. We surmise that the reason for the higher THz conductivity in PTI-LiBr compared to PTI-IF lies in the higher orbital coefficients on the lithiated imide bridges and, as a consequence, better charge transport between the triazine units (Figure ).