Electroluminescence and photophysical properties of polyquinolines

The electroluminescence and photophysical properties of a series of 11 poly quinolines were investigated and used to explore the effects of molecular a nd supramolecular structures on the light-emitting proper ties of polymers. Thin films of the polyquinolines have photoluminescence quantum yields bet ween 2 and 30% and unusually long excited-state lifetimes of 2.4-5.2 ns. El ectroluminescence colors spanning blue, green, yellow, orange, and red were obtained through regulation of the molecular and supramolecular structures of the excimer- and aggregate-forming polyquinolines. ITO/hole transport l ayer/polyquinoline/Al light-emitting diodes fabricated and evaluated in air had electroluminescence quantum efficiencies between 0.02 and 1% and lumin ance levels of up to 280 cd/m(2) at a current density of 100 mA/cm(2). The electroluminescence efficiency approximately scaled linearly with the photo luminescence quantum yield. Favorable reaction at the aluminum/polyquinolin e interface is proposed to account for the efficient electron injection and device performance in spite of the large (1.5-1.9 eV) energetic barrier to electron injection. These results provide new insights into the design of efficient light-emitting polymer materials and devices for optoelectronic a pplications.