Ultra-Narrow Pure-Green MR-TADF Emitter with an FWHM of 12 nm Enables Superior-Performance Top-Emitting OLEDs with EQE Approaching 60%, Power Efficiency Over 300 lm W(-1), and CIE Coordinates of (0.14, 0.79).

内容摘要

Achieving pure-green organic light-emitting diodes (OLEDs) with both precise spectral positioning and an ultra-narrow full-width at half-maximum (FWHM) remains highly challenging, as red-shifting emission into the pure-green regime is often accompanied by enhanced excited-state relaxation and spectral broadening. Herein, we report a molecular design strategy that reconciles green-region red-shift with intrinsic spectral narrowing through the synergistic integration of dibenzofuran fusion and cyano decoration within a meta-diboron framework. The proof-of-concept molecule DBFCN exhibits intrinsically ultra-pure green emission in dilute toluene, centered at 519 nm with a very small FWHM of 12 nm, placing it among the narrowest green multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters reported so far. The bottom-emitting OLEDs deliver a maximum external quantum efficiency (EQEmax) of 38.5% and pure-green emission at 521 nm with an ultra-narrow FWHM of 13 nm. Owing to the intrinsically ultra-narrow emission and minimal spectral tail of DBFCN, photon loss in the top-emitting (TE) configuration is effectively mitigated, leading to markedly enhanced device performance. Consequently, the TE-device delivers a maximum power efficiency (PEmax) exceeding 300 lm W-1 and a current efficiency (CEmax) of 232.5 cd A-1, while meeting the green BT.2020 color gamut.