Utilization of water/alcohol-soluble polyelectrolyte as an electron injection layer for fabrication of high-efficiency multilayer saturated red-phosphorescence polymer light-emitting diodes by solution processing

Highly efficient multilayer red polymer light-emitting diodes were fabricated by solution process-ing from iridium complex, bis(1-(3-(9,9-dimethyl-fluorene-2-yl)phenyl)isoquinoline-C2,N-') iridium(III)acetylacetonate, doped into polyfluorene as a host and with a water/alcohol-soluble polymer, poly[(9,9-bis(3(')-((N,N-dimethyl)-N-ethylammonium)propyl)-2,7-fluorene)-2,7-(9,9-dioctylfluorene)-4,7-(2,1,3-benzoselenadiazole)]dibromide (PFN) as electron injection layer. The device with the structure ITO/PEDOT-PSS(50 nm)/PVK(40 nm)/PFO:PBD:Ir(DMFPQ)(2)acac(2%,75 nm)/PFN(20 nm)/Ba(4.5 nm)/Al(150 nm) showed an external quantum efficiency of 18.0% and luminance efficiency of 9.8 Cd/A at a current density of 1.1 mA/cm(2), a peak emission at lambda(max)=636 nm, and Commission International de I'Eclairage coordinates of (0.665, 0.319). The efficiency remained as high as QE=11.1%, and LE=6.0 cd/A, at a current density of 100 mA/cm(2), and a luminance of 6140 cd/m(2). (c) 2006 American Institute of Physics.