High‐Performance Narrowband Pure‐Green OLEDs with Gamut Approaching BT.2020 Standard: Deuteration Promotes Device Efficiency and Lifetime Simultaneously

Abstract In order to fulfill the demand for ultrahigh definition organic light‐emitting diodes (OLEDs), pure‐green emitters with Commission Internationale de l’Éclairage (CIE) y‐coordinate over 0.71 are in urgent demand. Meanwhile, the high device efficiency, small efficiency roll‐off, and operational lifetime also remain challenging issues. In this work, a series of narrowband pure‐green fluorescent emitters based on a double‐boron (B) doped polycyclic aromatic hydrocarbons (PAHs) framework fused with naphthalene units is reported. The newly designed emitters realize green emission with peaks of 512–521 nm and extremely narrow full‐width at half‐maxima (FWHMs) of 16–17 nm in toluene solution. Utilizing these emitters in a phosphor‐sensitized fluorescence (PSF) system, the resulting OLEDs exhibit pure green emission with peaks in the range of 514–526 nm and very narrow FWHMs of 19–20 nm. Notably, the devices based on the partially deuterated emitter, DBN‐NaPh‐d, not only achieve a maximum external quantum efficiency (EQE_max) as high as 35.2%, small efficiency roll‐off, along with a CIEy of 0.74 but also showcase impressive operational stability with a long lifetime (LT₅₀) of over 3000 h at an initial luminance of 1000 cd m⁻². This work represents one of the highest device efficiencies and superior device stability among fluorescence emitter‐based OLEDs.