ABSTRACT The realization of ultrahigh definition displays necessitates pure‐green organic light‐emitting diodes (OLEDs) with simultaneously exceptional efficiency, high color purity, and long‐term operational stability. Herein, we develop a series of pure‐green multi‐resonance thermally activated delayed fluorescence (MR‐TADF) emitters based on the boron/nitrogen‐embedded polycyclic aromatic hydrocarbon (BN‐PAH), designed through a rational moderate π‐extension and peripheral phenyl blocking strategy. The molecular designs afford narrowband pure‐green emission with a full‐width at half‐maximum (FWHM) of nearly 20 nm and high photoluminescence quantum yields ( Φ PL s, up to 95%). By systematically blocking the redox‐active positions with phenyl groups, the emitters exhibit significantly enhanced electrochemical and photochemical stability. In bottom‐emitting OLEDs, the optimized emitter BN‐Tpl‐Ph achieves a maximum external quantum efficiency (EQE max ) of 33.8% and long operational lifetime (LT80 = 4012 h at 1000 cd m −2 ). Notably, in a top‐emitting OLED configuration, BN‐Tpl‐Ph delivers a pure‐green emission with a Commission Internationale de l'Eclairage (CIE) y‐coordinate of 0.78, a high EQE max up to 59.2%, and an LT80 of 409 h at 5000 cd m −2 . This work reveals the effectiveness of molecular design strategies that combine moderate π‐extension with peripheral phenyl blocking for developing high‐performance pure‐green MR‐TADF emitters.
Liu et al. (Fri,) studied this question.