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

• Published in: Advanced materials (Weinheim) Vol. 32; no. 29
• Main Authors: Park, Ho‐Yeol, Maheshwaran, Athithan, Moon, Chang‐Ki, Lee, Hyuna, Reddy, Saripally Sudhaker, Sree, Vijaya Gopalan, Yoon, Jiyoung, Kim, Jeong Won, Kwon, Jang Hyuk, Kim, Jang‐Joo, Jin, Sung‐Ho
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01-07-2020
• Subjects: carrier balance; Color; concentration quenching; deep‐blue phosphorescence; Doping; Electroluminescence; Emitters; Iridium compounds; Materials science; N‐heterocyclic carbene ligands; organic light‐emitting diodes; Phosphorescence; Phosphors; Power consumption; Purity; Quantum efficiency
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202002120

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 (Lmax) of 6453 cd m−2, by a device with a 40 vol% doping ratio. Moreover, another device demonstrates an EQEmax of 21.3%, an Lmax 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.
A high external quantum efficiency for deep‐blue‐emitting organic light‐emitting diodes is developed using a novel carbene‐based Ir(III) complex, which enhances the carrier balance in the emission layer. A high quantum efficiency of 24% with a deep‐blue CIE(x, y) coordinate of (0.149, 0.085) is achieved, which satisfies the stringent National Television System Committee (NTSC) requirements with high efficiency.