Thin-layer photoluminescence and electroluminescence observed from pyrazoloquinoline-doped polymer matrices

1,3-bisphenyl-4-methyl-pyrazolo[3,4-b]quinoline (PAQ4) has been found to be an excellent blue emitter in the solid state. High solid state photoluminescent quantum efficiencies have been found when doped in a number of polymer matrices, such as polycarbonate, polystyrene, poly (methyl methacrylate). Photoluminescence and electroluminescence of PAQ4-doped poly (N-vinyl carbazole) were also investigated. Dopant-dopant interaction between PAQ4 molecules was found to favour the production of high fluorescence at high dopant concentrations, which also contributed to a red shift and peak broadening in the emission peaks. Thin- and single-layered electroluminescent devices were also prepared using PAQ4-doped PVK as an emitting layer. Self-absorption was also observed in the devices, which modified emission spectra. It formed a useful tool to monitor the devices. Electroluminescence from the device was shifted slightly to the blue when compared to its photoluminescence. It suggests that the exciton recombination is located close to the polymer-ITO interface in the devices studied