Light extraction enhancement in organic light-emitting diodes based on localized surface plasmon and light scattering double-effect

We have demonstrated a new approach to realize the light extraction enhancement in organic light-emitting diodes (OLEDs) by using platinum-cobalt (Pt3Co) alloy nanoparticles (ANPs). The current efficiencies of 19.2 cd A(-1) and 29.3 cd A(-1) at a current density of 20 mA cm(-2) are obtained for the device with Pt3Co ANPs unannealed and annealed, respectively, which correspond to a similar to 46% and similar to 123% enhancement compared to the control device without Pt3Co ANPs. A systematic study on the devices with and without unannealed Pt3Co ANPs shows that the significantly enhanced efficiency is mainly due to the resonance of localized surface plasmon (LSP). The analysis of surface topography, angular-dependent EL spectra and theoretical calculations of the devices with and without annealed Pt3Co ANPs reveals that the annealing treatment of Pt3Co ANPs could result in a further enhancement in light extraction due to the increased light scattering effect, thereby achieving a double-enhancement in light extraction by simultaneously realizing the resonance of LSP and the light scattering effect.