Physics

OLED

Nanotechnology

Organic chemistry

Quantum efficiency

Boron

Optics

Quantum yield

Chemistry

Materials science

Condensed matter physics

Acceptor

Layer (electronics)

Diode

Photoluminescence

Optoelectronics

Photochemistry

Fluorescence

Nature Photonics

Materials that exhibit thermally activated delayed fluorescence are promising for the realization of efficient organic light-emitting diodes. However, finding suitable deep-blue thermally activated delayed fluorescence materials is still challenging. Here, we report two highly efficient deep-blue thermally activated delayed fluorescence emitters, TDBA–Ac and TDBA–DI, containing oxygen-bridged, symmetric and rigid boron acceptor moieties. Both emitters have been designed to have high photoluminescence quantum yield and narrow-band blue emission. TDBA–Ac and TDBA–DI exhibited deep-blue emission and a small singlet–triplet energy gap of 0.06 eV and 0.11 eV, respectively, in toluene. The 20wt%-doped films of TDBA–Ac and TDBA–DI in DBFPO host exhibited high photoluminescence quantum yields of 93% and 99%, respectively. The fabricated TDBA–DI device showed an extremely high external quantum efficiency of 38.15 ± 0.42% in the blue region with low roll-off characteristics of 25.2% at high luminance of up to 5,000 cd m–2. The TDBA–Ac-doped device exhibited a high external quantum efficiency of 21.50 ± 0.22% with deep-blue colour coordinates of (0.15, 0.06). The discovery of two deep-blue organic emitters of light could aid the development of next-generation organic light-emitting devices.

Highly efficient blue thermally activated delayed fluorescence emitters based on symmetrical and rigid oxygen-bridged boron acceptors