Modification of thermally activated delayed fluorescence emitters comprising fluorinated acridan–quinazoline and spiroacridan–quinazoline moieties for efficient green OLEDs

Abstract

We synthesize two new TADF emitters, 4Ac5FQN and 4SpAc5FQN, using acridan or spiroacridan as the donor and 5-fluoroquinazoline as the acceptor, with the introduction of F atoms into the molecules to enhance the TADF effect. These emitters exhibit emissions at 538 nm and 536 nm in electroluminescent devices, falling within the pure green light range. Both compounds exhibit small energy differences (ΔE_ST) of 0.02 eV and 0.07 eV between their singlet and triplet states, confirming their TADF characteristics. Notably, there is a long decay of up to 10 ms for these emitters in OLEDs. OLEDs utilizing 4SpAc5FQN achieve outstanding performance with the maximum external quantum efficiency (η_EQE) of 22.1%.