Enhancement of Phosphorescence of Ir Complexes Bound to Conjugated Polymers: Increasing the Triplet Level of the Main Chain

Conjugated fluorene-alt-pyridine and fluorene-alt-thiophene polymers containing phosphorescent iridium complexes have been synthesized. Exchanging the 2,5-linked pyridine group with the 3,4-linked thiophene group resulted in a blue shift in the absorption and emission spectra of the conjugated polymers. Upon incorporation of the thienyl unit, phosphorescent quantum yields of films increased from 0.05 to 0.20 and electrophosphorescent external quantum efficiencies increased from 0.32 to 0.84%. These results are attributed to raising the triplet energy of the main chain polymer, with respect to the Ir phosphor, thereby reducing quenching of the phosphor by the main chain.