Utilizing a sequential borylation strategy, we constructed a deuterium pure-green MR-TADF emitter. The associated device achieved narrowband emission with a full width at half maximum (FWHM) of 25 nm, CIE coordinates of (0.16, 0.75), a maximum external quantum efficiency (EQE) of 34.6% with minimal efficiency roll-off and a lifetime (LT₈₀) of 6078 h at an initial luminance of 1000 cd m⁻².

Abstract

Multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters, especially high-order B/N MR-TADF emitters, offer new opportunities in obtaining wide-color-gamut, high color purity, and highly efficient organic light-emitting diodes (OLEDs). Extending the device durability is still very challengeable for these emitters. Deuteration of emitters to slow down their degradation and lengthen device lifespan is a promising strategy. However, how to access deuterated high-order MR-TADF emitters remains to be explored. Herein, a synthetic protocol of high-order B/N products is proposed using deuterated starting materials and sequential borylation. Combining with fine-tuning electronic effect through adjusting position of tert-butyl ( ^t Bu) substituents, we successfully obtained deuterated triboron MR-TADF material ω’-DABNA-D that delivers precisely tuned pure-green emission with close-to-unity quantum yield and rapid reverse intersystem crossing (RISC). The resulting binary OLED approaches the BT.2020 standard with CIE coordinates of (0.16, 0.75) and demonstrates impressive external quantum efficiency (EQE) of 34.6% at maximum and 30.7% at 1000 cd m⁻². Additionally, an Ir(ppy)₃-sensitized device shows excellent operational stability, with an extrapolated lifetime (LT₈₀) of 6078 h at an initial luminance of 1000 cd m⁻². This study hence offers a promising methodology toward high-performance OLED with long device lifetime.