If the excited-state dipole moment (μe) is greater in magnitude than the permanent dipole moment associated with the ground state (μg), positive emission solvatochromism is more pronounced than the absorption solvatochromism. For PCs whose lowest energy excited state is CT in nature, μe is expected to be large, thus leading to a strong positive solvatochromism (Figures ). Positive solvatochromism is observed in each of the organic PCs 4CzIPN, 2CzPN and pDTCz-DPmS (Figure , Table ), confirming the CT character of the emissive As illustrated in Figures , solvent can influence the energy and profile of the emission spectra of the PC and, as a result, in the optical gap, E0,0 (Table , Figure ). For the 4d and 5d transition metal PCs, the optical gap between the ground state and first triplet excited state, E0,0(T1), is most significant because, as previously discussed, PET occurs exclusively from the triplet excited state. E0,0(T1) can therefore be inferred from the onset of the phosphorescence spectrum. For the organic PCs and [Cu(dmp)(xantphos)]PF6 it is less clearly defined whether the SET will originate from the S1 or T1 states owing to their intrinsic TADF nature. However, as previously discussed, it is more likely that the SET will occur from the T1 state. Despite this, from the room temperature, steady-state emission measurements, only E0,0(S1) can be determined (from the intersection point between the normalized absorption and emission spectra). Therefore, this value was used for subsequent determination of excited-state redox potentials.