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

Abstract

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(50nm)∕PVK(40nm)∕PFO:PBD:Ir(DMFPQ)2acac(2%,75nm)∕PFN(20nm)∕Ba(4.5nm)∕Al(150nm) showed an external quantum efficiency of 18.0% and luminance efficiency of 9.8Cd∕A at a current density of 1.1mA∕cm2, a peak emission at λmax=636nm, and Commission International de I’Eclairage coordinates of (0.665, 0.319). The efficiency remained as high as QE=11.1%, and LE=6.0cd∕A, at a current density of 100mA∕cm2, and a luminance of 6140cd∕m2.