Abstract
There has been significant progress in the development of polymer devices in recent years with polymer light-emitting diodes (PLEDs) now entering the market place as viable contenders to existing inorganic technologies. The fundamental processes governing device characteristics are the subjects of debate and there is considerable interest in experimental measurements that provide insight into device operation. In this paper, we use electroabsorption (EA) spectroscopy to investigate the strength of the internal electric field in polyfluorene (PF)-based operational PLEDs. Based on this technique, we study the operating mechanisms of the red, green and blue PLEDs with single layer structures. To fully understand the relationship between the PLEDs perforinance (brightness, efficiency etc.) and their internal operational mechanism, current-voltage-luminance response as well as the corresponding luminance and power efficiencies are also recorded and compared for each type of the PLEDs. The luminance efficiency of the devices used in this paper could all achieve at least 1 cd/A under a relatively low voltage.