Dual Regulation of Molecular Rigidity and Orbital Engineering of Pt(II) Emitters for High‐Performance Deep‐Blue OLEDs

Abstract Blue phosphorescent organic light‐emitting diodes (PhOLEDs) face critical challenges in terms of low color purity and severe efficiency roll‐off. In this study, four novel tetradentate Pt(II) emitters (PtCY, PtCY‐F, PtCY‐ t Bu, PtCY‐ t BuF) are designed through a synergistic strategy of molecular orbital engineering and steric hindrance effect. By introducing a bulky diisopropylbiphenyl (diPrPh) group at the N ‐heterocyclic carbene (NHC) moiety to increase molecular rigidity and suppress intermolecular interactions, the Pt(II) emitters achieve narrowband deep‐blue emission (452–457 nm) in dichloromethane, with full width at half maximum (FWHM) values of 18–23 nm. Combined with the introduction of fluorine atoms (─F) away from the lowest unoccupied molecular orbital (LUMO) distribution, the external quantum efficiency (EQE) is improved while avoiding the breakage of the C─F bond. PtCY‐ t BuF‐based device B4 achieved a high maximum luminance of 45621 cd m −2 , and record high EQEs of 27.1%, 24.3%, and 21.7% at high brightness levels of 1000, 5000, and 10 000 cd m − 2 respectively and lowest efficiency roll‐off of 3.2% at 1000 cd m −2 , among reported Pt(II)‐based deep‐blue OLEDs with CIE y < 0.15. This study provides a novel strategy for the development of highly efficient tetradentate Pt(II) emitters with high color purity for high‐performance deep‐blue PhOLED applications.