Peripheral Decoration of Dibenzofuran with Donors and Acceptors as a New Design Platform for Thermally Activated Delayed Fluorescence Emitters

A novel design for thermally activated delayed fluorescence (TADF) emitters was developed by decorating dibenzofuran with four carbazole type electron donors and two CN electron withdrawing units. The four carbazole type donors were attached to one side of the dibenzofuran, and two CN units were introduced on the other side of the dibenzofuran for highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) separation. The HOMO and LUMO were largely separated, and they were overlapped in the dibenzofuran due to aromatic nature of dibenzofuran. Two TADF emitters, DBFCzCN and DBFtCzCN, were built on the design platform decorating the dibenzofuran, and they showed high EQEs of 25.2% and 17.4% in the vacuum deposited TADF devices. Additionally, the DBFtCzCN emitter showed a high EQE of 13.9% in the solution processed TADF devices.