Carrier transport and high-efficiency electroluminescence properties of copolymer thin films

• Published in: Thin solid films 2000-03, Vol.363 (1), p.173-177
• Main Authors: Chen, Baijun, Liu, Yunqi, Lee, C.S, Yu, Gui, Lee, S.T, Li, Hongyu, Gambling, W.A, Zhu, Daoben, Tian, He, Zhu, Weihong
• Format: Article
• Language: English
• Subjects: Carriers mobility; Efficiency; Organic electroluminescent devices; Time-of-flight
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/S0040-6090(99)00990-6

A novel copolymer with moieties capable of charge transport and electroluminescence was synthesized. The drift mobilities of electron and hole in the spin-coated films of the copolymer on silicon substrate have been determined by the time-of-flight technique. The shape of the photo-current curves obtained for the transport of both electron and hole is typical for dispersive transport in organic polymers. Under an electrical field strength of 5.0×10 5 V/cm, the drift mobility of electron and hole is 4.78×10 −6 and 3.46×10 −6 cm 2/V s, respectively. A high-efficiency electroluminescent device with the bi-layer structure of ITO/copolymer/2-(4-biphenylyl)-5-(4-tert-butylphenl)-1,3,4,-oxadiazole (PBD) /LiF/Al was fabricated. The device emitted a bright blue-green light peaking at wavelength of 496 nm, originating from copolymer with a maximum current efficiency of 10 cd/A and a maximum luminescence efficiency of 2.9 lm/W at the DC drive voltage of 12 V.