Narrowband Deep‐Red and Near‐Infrared Tetradentate Platinum(II) Complexes for High‐Performance OLEDs With Emission Peaks up to 715 nm and EQEs Over 20%

Narrowband heavy‐metal phosphorescent complexes have been achieved in the visible region recently, yet such narrowband deep‐red/near‐infrared (DR/NIR) emitters have not been reported. In this study, four new tetradentate Pt(II) emitters ( Pt‐ 1,3 ‐DZF , Pt‐ 2,4 ‐DZF , Pt‐ 1,3 ‐PhCz , and Pt‐ 2,4 ‐PhCz ) are rationally designed by combining donor π‐extension with linkage‐position isomerization based on dibenzo[ b,d ]furan (DZF)‐ and 9‐phenyl‐9 H ‐carbazole (PhCz)‐functionalized triarylamine frameworks. This strategy effectively modulates the emissive excited‐state character and enables narrowband DR/NIR phosphorescence. Vacuum‐deposited OLEDs based on these emitters achieve emission maxima of 670–715 nm, maximum external quantum efficiencies (EQEs) up to 20.4%, and small efficiency roll‐offs at high radiance. Moreover, the full width at half maximums (FWHM) of electroluminescence spectra realize as narrow as 51 nm (0.14 eV), which is comparable to state‐of‐the‐art DR/NIR multiple‐resonance thermally activated delayed fluorescence (MR‐TADF) emitters, highlighting the potential of these Pt(II) complexes for high‐performance narrowband DR/NIR OLEDs.