Abstract
Poly(9,9-dioctylfluorene-2,7-diyl-co-2,8-dihexyldibenzothiophene-S,S-dioxide-3,7-diyl) copolymers (pF-S6 8−10) of varying composition have been synthesized by Suzuki−Miyaura polymerization. The hexyl substituents on the dibenzothiophene-S,S-dioxide (S) units improve the solubility of the copolymers and increase the dihedral angles in the backbone; this shifts the emission deep into the blue (λmax 420 nm for films of 10) and increases the photoluminescence quantum yield compared with previous pF-S copolymers containing non-alkylated S units. The backbone twist restricts formation of the intramolecular charge transfer (ICT) state for low incorporation ratios of S6 units. The triplet energy of these new copolymers increases as the percentage of the S6 unit increases (i.e., 15, 30, 50%: 8 → 9 → 10). The alternating copolymer 10 has a sufficiently high triplet energy (ET 2.46 eV for onset of phosphorescence) to host a green phosphorescent iridium guest emitter, as demonstrated in electroluminescence studies wh...
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