Graded doping profiles for reduction of carrier trapping in organic light-emitting devices incorporating doped polymers

Dispersing emissive dopants into luminescent polymers is an effective appro ach to enhance luminescence and to tune emission color in organic light-emi tting devices incorporating polymer films. However, the carrier trapping ef fect due to emissive dopants often causes deterioration of electrical chara cteristics. In this letter, we show that, by introducing a graded doping pr ofile to match the carrier recombination zone in the doped polymer, the car rier trapping, and the deterioration of electrical characteristics can be m inimized while the enhancement in efficiency maintains. The finite-source d ye-diffusion thermal transfer is used to produce graded doping profiles int o a luminescent polymer. The effectiveness of this approach has been demons trated in both single-layer and heterostructure devices incorporating doped polymers. (C) 2001 American Institute of Physics.