Hybridizing Carbonyl‐/Nitrogen‐ and Carbon‐/Nitrogen‐ Multiple Resonant Motifs for Efficient Pure Green TADF Emitters

Abstract In next‐generation displays, green emission carries weight for widening the color gamut comparing to blue and red emissions. Multi‐resonant (MR) emitters hold great potential in meeting the new BT.2020 color purity. However, C/N and C═O/N‐based pure‐green MR systems remain underdeveloped despite their synthetic accessibility. Here, a successful case is presented by merging C/N and C═O/N MR cores into a hybrid MR system, forming a new pure green emitter, DPQAO‐ICz. The new molecule simultaneously maintains the MR character of its parent cores and effectively redshifts the emission to the target green region with a peak/full‐width‐at‐half‐maximum (FWHM) of 504/26 nm in toluene. The enhanced transition oscillator strength endows DPQAO‐ICz with improved photoluminescence quantum yield up to 92% in the doped film. Organic light‐emitting diodes (OLEDs) based on DPQAO‐ICz deliver pure green emission peaking at 515 nm with FWHM of 34 nm, cutting‐edge CIEy and maximum external quantum efficiency (EQE max ) of 0.68 and 25.9% among reported C/N‐ and C═O/N‐based MR emitters. The EQE max was boosted to 31.6% in the hyper‐OLED. This study exemplifies an effective method to considerably extend the π plane to reduce the energy gap of emitters. The method also enables redshifted narrowband emission without sacrificing oscillator strength and broadening FWHM.