Hybridized Multi-Spiral Donor Engineering for High-Efficiency Narrowband Thermally Activated Delayed Fluorescence Emitters

The pursuit of narrowband multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters with both high efficiency and color purity remains a critical challenge in the field of organic light-emitting diodes (OLEDs). A novel molecular design paradigm is proposed by hybridizing di-/tri-spiral donors in polycyclic heteroaromatic frameworks. The orthogonal, sterically hindered spiral donors disrupt molecular planarity, which can simultaneously suppress the aggregation-caused quenching and spectral broadening. These emitters exhibit narrowband emission with full-width at half-maximum of 22–24 nm and high photoluminescence quantum yields of ∼100%. The tri-spiral donor configuration further improves horizontal dipole orientation for the enhanced light outcoupling. As a result, the optimal Ts-NBN-based OLED achieves a maximum external quantum efficiency of 39.1% with the CIE y value of 0.70.