Enhanced performance of pulse driven small area polyfluorene light emitting diodes

We have investigated the performance of conjugated polymer light emitting d iodes (LEDs) as their active areas are reduced to dimensions typical for pi xellated displays. We find that by reducing the active diameter of the devi ce from our standard size (1.5x3 mm) to 50 mum, the current density that ca n be sustained before LED failure increases by a factor of 9. This increase in current density is mirrored by similar increases in maximum LED brightn ess. We propose that such effects occur due to improved thermal management in small area devices. Using pulsed driving schemes, devices with a diamete r of 50 mum sustained current densities of 5.1 MA m(-2), and have emitted e lectroluminescence with a brightness of 6.5 Mcd m(-2). (C) 2001 American In stitute of Physics.