Efficient and colour-stable hybrid white organic light-emitting diodes utilizing electron–hole balanced spacers

• Published in: Journal of physics. D, Applied physics Vol. 43; no. 40; p. 405102
• Main Authors: Leem, Dong-Seok, Kim, Ji Whan, Jung, Sung Ouk, Kim, Seul-Ong, Kim, Se Hoon, Kim, Kee Young, Kim, Yun-Hi, Kwon, Soon-Ki, Kim, Jang-Joo
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 13.10.2010; Institute of Physics
• Subjects: Applied sciences; Brightness; Color; Colour; Devices; Electronics; Emitters; Exact sciences and technology; Light-emitting diodes; Optoelectronic devices; Oranges; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Spacers; Transport process; Line intensity; Luminance; Benzene derivatives; Electroluminescence; Quantum yield; Current density; Light emitting diode
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/0022-3727/43/40/405102

High-efficiency two-colour white organic light-emitting diodes (WOLEDs) comprising a newly synthesized iridium complex orange phosphor ((impy) 2 Ir(acac)) and a blue fluorophor (BD012) have been realized by placing several kinds of thin spacers between two emitters. Hybrid WOLEDs with a spacer composed of a hole-transporting N , N -dicarbazolyl-3,5-benzene (mCP) and an electron-transporting 4,7-diphenyl-1,10-phenanthroline (Bphen) exhibit a high external quantum efficiency (EQE) of up to 8.4% and a negligible colour change (the colour coordinate of (0.39, 0.41) at 1000 cd m −2 ) with increasing brightness, whereas the device using a hole-transporting mCP spacer shows a relatively low EQE of 6.2% and a large shift of emitting colour with increasing brightness. Device performance is further characterized based on the charge transport behaviour of the spacers inserted between the two emitters.