Donor-sigma-Acceptor Motifs: Thermally Activated Delayed Fluorescence Emitters with Dual Upconversion

Abstract

A family of organic emitters with a donor-sigma-acceptor (D-sigma-A) motif is presented. Owing to the weakly coupled D-sigma-A intramolecular charge-transfer state, a transition from the localized excited triplet state ((LE)-L-3) and charge-transfer triplet state ((CT)-C-3) to the charge-transfer singlet state ((CT)-C-1) occurred with a small activation energy and high photoluminescence quantum efficiency. Two thermally activated delayed fluorescence (TADF) components were identified, one of which has a very short lifetime of 200-400 ns and the other a longer TADF lifetime of the order of microseconds. In particular, the two D-sigma-A materials presented strong blue emission with TADF properties in toluene. These results will shed light on the molecular design of new TADF emitters with short delayed lifetimes (c) 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim