Energy transfer process from polymer to rare earth complexes

The interaction between poly(N-vinylcarbazole) (PVK) and rare earth (RE) complexes, such as Eu(thenoytrifluoacetonato) 4-(monopyridinium) (Eu(TTA)4Py). Eu(nitrate)3 (monophenanthroline) (Eu(NO3) 3phen) and Tb(acetylacetonato) 3 (monophenanthroline) (Tb(AcA)3phen), was investigated in solution as well as in films using the photoluminescence (PL) spectrum. In chloroform solution, the fluorescent intensity of the Eu(NO3) 3phen was enhanced by PVK; however, the fluorescent intensity of the Tb complex was greatly quenched by PVK. Strongly characteristic emissions of Eu3+ and Tb3+ were observed in Eu and Tb complex-dispersed PVK films, respectively. The excitation spectra of Eu complex-dispersed PVK films and Tb complex-dispersed PVK film are very similar to that of the pure PVK film, indicating that effective energy transfer occurs from PVK to the RE complexes. Based on the above experimental results, three types of organic electroluminescence (EL) devices with structure of ITO/Eu(NO3)3phen:PVK/OXD-7/Al, ITO/Eu(TTA)4Py:PVK/OXD-7/Al and ITO/ Tb(AcA)3phen:PVK/OXD-7/Al (ITO = indium-tin oxide) were fabricated. Bright red emission can be observed in the first and second devices while bright green light was emitted from the latter device.