Efficient energy transfer to achieve narrow bandwidth red emission from Eu3+-grafting conjugated polymers

A convenient approach to novel Eu3+-grafting conjugated polymers to achieve sharp red emission for polymeric light emitting diodes (PLEDs) has been developed in this contribution. The structure of polymer 1 is verified by FT-IR, H-1, C-13 NMR and elemental analysis. The results indicate that efficient intramolecular Foster energy transfer depends on the overlap between the fluorescent spectrum of polymer 1 and absorption spectrum of Eu3+ chelates. Eu(DBM)(3) is obviously the best one for accepting energy from polymer 1 among three Eu3+ chelates to exhibit the sharp red emission. The investigation also shows that the efficiency of energy transfer relies on the content of Eu3+ in the complexes. The investigations on the photophysical and electrochemical properties also show that the HOMO and LUMO energy levels and the band gap of complexes have no alteration with the attachment of the Eu3+ chelate in comparison with those of polymer 1 due to the Eu3+ chelate at the side chain of the whole molecule. The pure red electroluminescence is achieved from the fabrication of PLEDs using complex 5 as the active layer with the configuration of ITO/PVK/complex 5/Ba/Al.