Benzo[1,2-b:4,5-b']dithiophene as a weak donor component for push-pull materials displaying thermally activated delayed fluorescence or room temperature phosphorescence

In the search for high-performance donor-acceptor type organic compounds displaying thermally activated delayed fluorescence (TADF), triisopropylsilyl-protected benzo[1,2-b:4,5-b']dithiophene (BDT-TIPS) is presented as a novel donor component in combination with two known acceptors: dimethyl-9H-thioxanthenedioxide (TXO2) and dibenzo[a,c]phenazinedicarbonitrile (CNQxP). For broader comparison, same acceptors are also combined well-studied 9,9-dimethyl-9,10-dihydroacridine (DMAC) donor. Optimized BDT-TIPS-containing structures show calculated dihedral angles of around 50° well-separated highest occupied lowest unoccupied molecular orbitals, although varying singlet-triplet energy gaps observed experimentally. By changing acceptor moiety resulting ordering excited states, room temperature phosphorescence (RTP) attributed to localized BDT-TIPS emission TXO2-BDT-TIPS, whereas CNQxP-BDT-TIPS affords TADF triplet-triplet annihilation (TTA) emission. contrast, strong pure well-known TXO2-DMAC, CNQxP-DMAC shows mixture TTA at very long timescales. Overall, represents an alternative low-strength push-pull emitters that able induce RTP properties.