ABSTRACT Deep‐blue phosphorescent OLEDs (PhOLEDs) with high efficiency and high color purity often suffer from serious efficiency roll‐off and brightness decay, which critically limit their practical application. Herein, we report a rigid and sterically hindered tetradentate Pt(II) emitter, PtKW2, designed via synergistic modulation of molecular rigidity, intermolecular stacking suppression, and triplet localized excited‐state ( 3 LE) character. By introducing a bulky 2,6‐diisopropylphenyl group, a ring‐locked framework, and a π‐conjugated extended benzofuro3,2‐ c carbazole moiety, PtKW2‐doped film exhibits deep‐blue emission at 459.0 nm with an ultra‐narrow full width at half maximum (FWHM) of 18.0 nm, a high photoluminescence quantum yield ( Φ PL ) of 94%, and a short excited‐state lifetime ( τ ) of 4.4 µs. A PtKW2‐based bottom‐emitting PhOLED achieves deep‐blue electroluminescence at 467 nm with Commission Internationale de l’Éclairage (CIE) coordinates of (0.122, 0.167). Notably, a record‐low efficiency roll‐off of only 1.2% at 1000 cd m − 2 , a record‐high L 90 of 5091 cd m − 2 , and a record‐high J 90 of 20.4 mA cm − 2 are simultaneously achieved among reported Pt(II)‐based OLEDs with CIE y < 0.20. This study establishes an effective molecular engineering strategy for overcoming efficiency roll‐off and brightness degradation in high‐performance deep‐blue PhOLEDs.
Xu et al. (Tue,) studied this question.