Synergistic Modulation of Triplet Density and Heavy‐Atom Effect Accelerates Reverse Intersystem Crossing for Narrowband Multi‐Resonance TADF Emitters

Key Points

• To explore design strategies that enhance efficiency and color purity in organic light-emitting diodes (OLEDs).
• Developed narrowband multi-resonance thermally activated delayed fluorescent (MR-TADF) emitters.
• Analyzed triplet density and heavy-atom effects to optimize reverse intersystem crossing (RISC).
• Evaluated the performance using Commission Internationale de l'Éclairage (CIE) coordinates.
• Achieved high efficiency and excellent color purity in OLEDs.
• CIE coordinates recorded at (0.20, 0.74), indicating a strong green device performance.
• Established design principles for optimizing RISC and color purity in MR-TADF systems.