High brightness and efficiency blue light-emitting polymer diodes

Abstract

Efficient blue electroluminescence, peaked at 436 nm, is demonstrated from polymer light-emitting diodes operating at high brightness. A dioctyl-substituted polyfluorene was used as the emissive layer in combination with a polymeric triphenyldiamine hole transport layer. The luminance reaches $\text{600\hspace{0.5em}}{\mathrm{cd/m}}^{\mathrm{2}}$ at a current density of $\text{150\hspace{0.5em}}{\mathrm{mA/cm}}^{\mathrm{2}}$ for a bias voltage of 20 V, corresponding to an efficiency of 0.25 cd/A and a luminosity of 0.04 lm/W. These values are optimized at a critical emissive layer thickness.