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-9H-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.