Blue emission from polymer light-emitting diodes using non-conjugated polymer blends with air-stable electrodes

By dispersing a non-conjugated luminescent polymer and an electron-transporting material, 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD), into a hole-transporting polymer, poly(9-vinylcarbazole) (PVK), we have achieved improved efficiencies for blue light-emitting diodes (LEDs) fabricated with a copolyester (CPE) containing isolated 1,2-dinaphthylethene units. Quantum efficiencies of the LEDs with the solid dispersion of CPE and PBD in PVK as electroluminescent layer and indium as the electron injection electrodes are about 0.1% photons per electron, better by factor of 102 than similar devices made with only the CPE. The LEDs turn on at about 30 V and have a peak emission wavelength in the blue at 485 nm.