Selective decoration of dibenzofuran with multi-donors and a triazine acceptor for triplet to singlet up-conversion

A chemical platform of thermally activated delayed fluorescence (TADF) emitters is proposed through selective substitution of multi-donors and an acceptor to the dibenzofuran core. Three carbazole based donors and one triazine acceptor were selectively attached to the phenyl unit of dibenzofuran. This novel material design platform enabled efficient up-conversion of triplet excitons into singlet excitons through the multi-donor-acceptor structure with the donors and acceptor aligned in a linear fashion. The congested molecular structure with the donors and acceptor at one side of dibenzofuran facilitated the up-conversion process and achieved high external quantum efficiency in the TADF devices. The TADF organic light-emitting diodes demonstrated high external quantum efficiency of 18.9% and efficient triplet exciton to singlet exciton up-conversion. 3CzDBFTrz and 3mCzDBFTrz with multi-donor-acceptors of thermally activated delayed fluorescence emitters are achieved with a small singlet-triplet energy gap and fast reverse intersystem crossing.