The normalized steady-state photoluminescence (PL) spectra of 4CzIPN and pDTCz-DPmS in DCM are presented in Figure . The Gaussian band shape, alongside the observed positive solvatochromism (Figure ), provide evidence of the charge transfer (CT) character of the emissive excited state. The optical gap, E0,0, identified from the intersection point between the normalized absorption and emission spectra (Table ) are 2.60 and 3.01 eV for 4CzIPN and pDTCz-DPmS, respectively, in DCM. pDTCz-DPmS displays a much larger E0,0 than 4CzIPN, irrespective of solvent. This is due to both the emission of pDTCz-DPmS being slightly blue-shifted relative to 4CzIPN (λPL = 524 nm and 544 nm in DCM, respectively) as well as the redshifted CT absorption band present in 4CzIPN compared to that in pDTCz-DPmS. As a result, pDTCz-DPmS has an optical gap of ca. 0.5 eV larger than that of 4CzIPN;