A Novel Design Strategy for Benzo[ <i>b</i> ]Thiophene Substituted Multiple Resonance Type Blue Fluorescent Dopant With Maximized Efficiency and Super‐Narrow FWHM

Conventional blue fluorescent emitters suffer from low efficiency and broad full width at half maximum (FWHM), limiting their application in next-generation organic light-emitting diodes (OLEDs). In this work, we report a novel double boron-based multi-resonance-type blue fluorescent emitter, v-DABNA-BT by incorporating a benzo[b]thiophene unit into the v-DABNA core to address the efficiency and color purity issues of the blue OLEDs. The v-DABNA-BT exhibited deep blue emission with a photoluminescence peak at 466 nm and an exceptionally narrow FWHM of 13.9 nm. As a pure blue fluorescent emitter, it delivered a high external quantum efficiency of 10.8%, FWHM of 15.6 nm, and color coordinate of (0.115, 0.138). In addition, the v-DABNA-BT-based hyperfluorescent (HF) OLEDs achieved a maximum external quantum efficiency of 28.7% with a FWHM of 18.2 nm, one of the best performances reported among HF systems employing pure fluorescent terminal emitters. This result underscores the potential of benzo[b] thiophene-modified boron-based MR-type fluorescent emitters as promising candidates for high-efficiency, high-color-purity OLED applications.