Highly efficient white polymer light-emitting diodes based on nanometer-scale control of the electron injection layer morphology through solvent processing

A study has reported highly efficient white phosphorescent polymer light-emitting diodes (WPLED) based on nanoscale morphological control of the poly[9,9-bis(6'-diethanolamino)hexyl)-fluorene] (PEN-OH) electron-injecting layer, which was inserted between the emissive layer and Al cathode through solution processing. The electroluminescent (EL) spectra and luminous efficiency (LE) of the devices are strongly dependent on the morphology of the PFN-OH films. The maximum luminance efficiency and power efficiency of WPLEDs increase significantly from 4.83 cd A^-1 and 3.12 lm W^-1 to 20.7 cd A^-1 and 13.2 lm W^-1 for PFN-OH film cast from different solvents. Furthermore, after the insertion of an active metal (Ba) layer between PFN-OH and Al, the maximum power efficiency of the corresponding WPLEDs reaches 14.5 lm W^-1, which is comparable to the power efficiency of the incandescent light bulbs.