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

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 LT95 = 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.