Efficient orange-red/red thermally activated delayed fluorescence materials based on 1,8-naphthalimide and donor engineering

Low-cost and efficient long-wavelength thermally activated delayed fluorescence (TADF) materials are crucial for organic light-emitting diodes (OLEDs) applications. In this study, 1,8-naphthalimide (NAI)-based D-A-type molecules were explored with a focus on donor engineering. A green-emitting non-TADF original control, the NAI/triphenylamine (TPA) hybrid NAI-TPA, was subjected to structural locking by oxygen-atom bridges on the TPA unit and further adopted an adjacent two-donor configuration to obtain two efficient orange-red/red TADF emitters, NAI-DPXZ and NAI-2DPXZ. The two compounds exhibited both significantly redshifted electroluminescence and improved external quantum efficiency (EQE), reaching 22.12% at 583 nm and 11.17% at 622 nm, respectively, which are approximately 2-3 times greater than those achieved by the O-bridges-free controls NAITPA (7.38 % at 517 nm) and NAI-2TPA (5.80 % at 564 nm). This work may provide an effective design strategy for the development of high-performance and low-cost orange-red/red TADF materials.