N‑Heterocyclic Carbene Based Pt(II) Complexes with d‐p Transition for Highly Performable Green Phosphorescent Electroluminescence

Abstract Novel carbene‐based tetradentated Pt(II) complexes, namely Pt(pibOppy) and Pt(ppbOppy), are developed and found to exhibit radiative metal‐centered (MC) d‐p triplet transition, resulting in highly efficient and configurational‐rigid phosphorescence. The Pt(II) complexes emit green light with peak wavelengths of 512–526 nm. Pt(ppbOppy), with enhanced carbene‐Pt interaction, achieves a high photoluminescent quantum yield of 99% in thin film, better thermo‐ and photo‐stability, and a structured emission spectrum. Device B1, by incorporating Pt (ppbOppy), shows a narrow green emission with Commission Internationale de l'Elcairage (CIE) coordinates of (0.306, 0.633), a long working lifetime of LT 95 = 111 h at 1000 cd m −2 , and high maximum values of the external quantum efficiency, power efficiency, and current efficiency of 20.4%, 74.1 lm W −1 , and 72.1 cd A −1 , respectively. The exceedingly flawless device performance highlights the immense potential of Pt(II) complexes with d‐p transition for organic electroluminescence.