The photoluminescence quantum yields, measured in degassed conditions, are strongly dependent on solvent polarity with a value of 42% in toluene and 2.0% in DMF solution (Table ). In an attempt to better ascertain trends associated with the solvent polarity, toluene was also employed as a solvent for photophysical measurements since it is nonpolar. The photoluminescence quantum yields measured under air-equilibrated solution correspond roughly to the prompt emission and show a similar trend. The ratio of the prompt and delayed emission quantum yield changes from 2:1 in toluene and DMF to almost 5:1 in THF and DCM, without a clear trend evident with respect to the solvent polarity. The time-resolved PL decays of pDTCz-DPmS were measured for 10 -5 M solutions under vacuum at room temperature (Figure ). In toluene, THF, DCM and DMF, the emission decays with bi-exponential kinetics (Table ). The prompt emission occurs with a 3 to 7 ns lifetime (tp) in all four solvents, while the microsecond-range delayed emission lifetime, td, becomes shorter with increasing solvent polarity.