External Quantum Efficiency Exceeding 24% with CIE_y Value of 0.08 using a Novel Carbene‐Based Iridium Complex in Deep‐Blue Phosphorescent Organic Light‐Emitting Diodes

Abstract Deep‐blue triplet emitters remain far inferior to standard red and green triplet emitters in terms of exhibiting high‐color‐purity Commission International de l'Éclairage (CIE) y values of ≤0.1, external quantum efficiencies (EQEs), and high electroluminescent brightnesses in phosphorescent organic light‐emitting diodes. In fact, no deep‐blue triplet emitter with color purity and high device performance has previously been reported. In this study, a deep‐blue triplet emitter, mer‐tris(N‐phenyl, N‐benzyl‐pyridoimidazol‐2‐yl)iridium(III) (mer‐Ir1) is developed, which meets the requirements of the National Television System Committee (NTSC) CIE(x, y) coordinates of (0.149, 0.085) with an extremely high EQE of 24.8% and maximum brightness (L_max) of 6453 cd m⁻², by a device with a 40 vol% doping ratio. Moreover, another device demonstrates an EQE_max of 21.3%, an L_max of 5247 cd m⁻², and CIE(x, y) coordinates of (0.151, 0.086) at a 30 vol% doping ratio. This is the first report of a high‐performance, deep‐blue phosphor, carbene‐based Ir(III) complex device with outstanding CIE(x, y) color coordinates and a high EQE. The results of this study indicate that the novel dopant mer‐Ir1 is a promising candidate for reducing power consumption in display applications.