Highly Fluorescent Emitters Based on Triphenylamine-π-Triazine (D-π-A) System: Effect of Extended Conjugation on Singlet-Triplet Energy Gap

Abstract

Three D-π-A type linearly-extended emitters, based on diphenylamine (DPA) as the donor and 2,4,6-triphenyl-1,3,5-triazine (TRZ) as the acceptor, were synthesized and their optoelectronic properties characterized. The introduction of an additional phenyl or phenylethynyl π-spacer results in an enhancement of the molar extinction coefficient and a systematic bathochromic shift of the charge-transfer transition in the absorption spectra. A mirrored bathochromic shift in the photoluminescence spectra is also observed with increasing conjugation of the bridge moiety. All three compounds show high photoluminescence quantum yields and moderate singlet-triplet excited state energy gaps, ΔEST, of 0.26-0.37 eV were observed in 10 wt% doped films in PMMA as the host matrix.