Stable Binuclear Platinum(II) Emitters with Substituted 2‐Hydroxypyridine Bridging Ligands for Red and Near‐Infrared OLEDs with EQE up to 32% and LT ₉₅ up to 26 250 h at 1000 cd m ⁻²

Abstract

Abstract Platinum(II) metal–metal‐to‐ligand charge transfer ( 3 MMLCT) emitters have high radiative decay rates and tunable emission energies but their stability under device operation conditions is a critical issue. Here we describe a new class of substituted 2‐hydroxypyridine bridged binuclear Pt II complexes [Pt 2 (R‐N^O)] that display strong 3 MMLCT emission in the red to NIR region with emission quantum yields up to 0.87 and radiative decay rate as high as 6.69 × 10 5 s −1 . Compared with the conventional formamidinate bridging ligand, the asymmetric N and O donor sites of the R‐N^O bridging ligand can form strong Pt─N and Pt─O bonds by modulating the electron distribution on the N^O bridging ligand, thus forming a binuclear Pt II complex with enhanced stability. OLEDs based on [Pt 2 (R‐N^O)] emitters as dopants have an EQE max of 32.7%, efficiency roll‐off of 2.4% at 1000 cd m −2 and LT 95 >26 200 h at L 0 of 1000 cd m −2 . The [Pt 2 (R‐N^O)] complex‐sensitized red hyper‐OLEDs with CIE coordinates of (0.65, 0.35) had an FWHM of 35 nm (0.11 eV) and an outstanding device lifetime of LT 95 >23 300 h at 1000 cd m −2 . The co‐doped NIR OLEDs achieved an EQE max of 17.5% at 734 nm emission and excellent operational stability with LT 99 value of 25 873 h at an initial radiance of 1000 mW Sr −1 m −2 . This highlights the practical commercial application of 3 MMLCT emitters in OLEDs technology.