A π-extended tercarbazole-core multi-resonance delayed fluorescence emitter exhibiting efficient narrowband yellow electroluminescence.

Herein, a simple and versatile molecular design for long-wavelength (>550 nm) multi-resonance thermally activated delayed fluoresence emitters is reported. Extending a fully fused polycyclic π-system with an additional para -N-π-N conjugation induces narrowband bright-yellow photoluminescence and electroluminescence emissions at ∼560 nm.