Ultraviolet electroluminescence from organic light-emitting diode with cerium(III)-crown ether complex

Cerium-dicyclohexano-18-crown-6 complex, Ce-DC-18 center dot C center dot 6, was prepared and used to fabricate organic light-emitting diode (OLEDs) with structure of ITO (indium tin oxide)/CuPc (copper-phthalocyanine)/Ce-DC-18 center dot C center dot 6: CBP (4,4'-bis(9-carbazolyl)biphenyl)/Bu-PBD (2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole)/LiF/Al. In the device the emitter layer consists of Ce(III)-complex as a dopant and CBP as a host. Adopting this doping Ce(Ill)-complex film, the device exhibits ultraviolet (UV) emission at 376 nm and maximum UV radiance power 13 mu W/cm(2) at 3 wt% Ce(III)-complex doped device is obtained, which has been improved by about two times in comparison with no Ce(III)-complex layer UV device. In terms of photoluminescence (PL) of Ce(III) ion and CBP film, we demonstrated that the two UV emissions should be assigned to be from electron transitions of 5d -> 4f of the Ce(III) ion and of S-1 + S-0 of CBP molecule, respectively. Increasing in UV radiation at shorter UV wavelength is more valuable and interesting for solid lighting application because the shorter UV emission would much match with excitation bands of more organic or inorganic phosphors. The mechanism on the electroluminescence (EL) processes of Ce(III) ion was also discussed. (c) 2007 Elsevier Ltd. All rights reserved.