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

Platinum(II) metal-metal-to-ligand charge transfer (³MMLCT) 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 [Pt₂(R-N^O)] that display strong ³MMLCT emission in the red to NIR region with emission quantum yields up to 0.87 and radiative decay rate as high as 6.69 × 10⁵ 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 [Pt₂(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 LT₉₅ >26 200 h at L₀ of 1000 cd m^-2. The [Pt₂(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 LT₉₅ >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 LT₉₉ value of 25 873 h at an initial radiance of 1000 mW Sr^-1 m^-2. This highlights the practical commercial application of ³MMLCT emitters in OLEDs technology.