High performance blue light-emitting diodes based on conjugated polymer blends

We report on the fabrication and properties of single layer blue light-emit ting diodes (LEDs) based on conjugated Polymer blends of emissive and hole transport materials. Despite the fact that the photoluminescence quantum ef ficiency of the blend is lower compared to that of both the host and the gu est polymers, an enhancement in both the electroluminescence quantum and pa ver efficiency is seen for the blend. This observation indicates that the h ole transporting material leads to a significantly improved hole injection and thus a greatly improved charge carrier balance factor. Optimised single layer blue LEDs showed a maximum brightness of 6000 Cd/m(2) at 14 V and a maximum external ELQE of 1% (2.1Cd/A) at 15 Cd/m(2) corresponding to a powe r efficiency of 1 lm/W.