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

Abstract 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.