Narrowband Tetradentate Pt(II) Complexes‐Based Deep‐Blue OLEDs with Low Efficiency Roll‐Off

This study designed and synthesized two tetradentate Pt(II) complexes featured with aryl‐ modified N ‐heterocyclic carbene (NHC) ligands, PtTJ‐Ph and PtTJ‐bPh, which exhibited narrow emission spectra with full‐width at half‐maximum (FWHM) of 19.0 and 19.8 nm in dichloromethane, respectively. They also showed remarkably high photoluminescence quantum yields of 99% and 93%, along with short excited‐state lifetimes of 2.72 µs and 2.34 µs in poly(methyl methacrylate (PMMA) films, respectively. Deep‐blue OLED device using PtTJ‐Ph as emitter exhibited narrowband emission spectrum peaking at 458 nm with a small FWHM value of 25 nm, resulting in a small Commission Internationale de l'Éclairage (CIE) y coordinate of 0.138. The device also achieved a maximum external quantum efficiency (EQE) of 22.7%, and maintained an EQE of 20.8% at 1000 cd/m 2 with a low efficiency roll‐off of only 8.3%, demonstrating excellent electroluminescent properties for deep‐blue OLED application.