Exceedingly Stable Luminescent Dinuclear Pt(II) Complexes with Ditopic Formamidinate Bridging Ligands for High‐Performance Red and Deep‐Red OLEDs with LT97 up to 2446 h at 1000 cd m−2

Abstract The utilization of triplet metal‐metal‐to‐ligand‐charge‐transfer ( 3 MMLCT) emissions of Pt(II) complexes having a large radiative decay rate is a promising strategy to develop efficient red and deep‐red emitters for practical organic light‐emitting diodes (OLEDs). The panel of robust luminescent dinuclear Pt(II) emitters described here features pyridine‐/pyrazine‐fused N‐heterocyclic carbene‐based cyclometalating ligands and ditopic bis‐ µ 2 ‐formamidinate bridging ligands. These complexes show intramolecular Pt–Pt distances of 2.85–2.87 Å, are thermally stable up to 446 °C, and display strong red and deep‐red 3 MMLCT emission (604–689 nm) with emission quantum yields close to unity. Under laboratory conditions, red and deep‐red OLEDs with these complexes show high external quantum efficiencies (up to 21.3%) and prolonged operational lifetimes (LT 97 up to 2446 h) at an initial luminance of 1000 cd m −2 , highlighting the practicality of these dinuclear Pt(II) emitters in organic optoelectronics application.