Excited-state property regulation of tetradentate Pt(II) emitter for high-performance blue OLEDs

Blue organic light-emitting diodes (OLEDs) have attracted great attention because of their promising application in displays; however, developing high-performance blue OLEDs is challenging. Here, we report a strategy to design extremely narrowband phosphorescent Pt(II) emitters by extending the π conjugation and assembling steric hindrance groups. This Pt(II) emitter possesses a surprisingly narrow emission spectrum in solution with a small full width at half-maximum (FWHM) of only 18.4 nm. A bottom-emitting device achieves a high maximum external quantum efficiency (EQE) of 30.3% and maintains high EQE values of 29.2%, 25.1%, and 22.0% at 1,000, 5,000, and 10,000 cd/m 2 , respectively; moreover, the device exhibits one of the highest maximum brightness values of up to 51,315 cd/m 2 among Pt(II)-based blue OLEDs with a Commission Internationale de l'Eclairage y value (CIE y ) of < 0.20. This work provides a strategy to design robust Pt(II) emitters for fabricating highly efficient blue OLEDs with high color purity and luminescence.