Benzazasiline combined with triphenylborane-based cores for constructing deep-blue donor-acceptor-donor TADF emitters

Abstract

We performed a first-principles systematic study on the fitness of two tricyclic donors (acridine and benzazasiline) interacting with five acceptors (triazine or triphenylborane-based) within the donor-acceptor-donor (D-A-D) framework for the potential application in organic light-emitting diodes (OLEDs) as thermally activated delayed fluorescence (TADF) emitters. Three types of compounds (D1-A-D1 (I), D2-A-D2 (II), and D1-A-D2 (III) were thus constructed to investigate the substitution pattern which can exhibit good TADF performance. We found that: by incorporating into the D-A-D frameworks and adopting an appropriate donor/acceptor combination, the studied compounds can bear rather small singlet-triplet gaps of ∼0.02 eV, and the emission energy can span a large space in (deep-)blue region (2.62∼3.13 eV); the molecular symmetry, in addition to the character of donors, control the properties of excited states, and acridine is more easily to be excited compared to benzazasiline. The symmetric setup (types I and II) is more suitable than asymmetric counterpart (type III) for optimal optoelectric properties. Accompanied with estimation of emission energy and rate constant, this study suggests that benzazasiline donor can serve as a versatile structural unit to combine with triphenylborane-based acceptor cores for constructing deep-blue D-A-D TADF emitters.