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 approach to enhance luminescence and to tune emission color in organic light-emitting devices incorporating polymer films. However, the carrier trapping effect due to emissive dopants often causes deterioration of electrical characteristics. In this letter, we show that, by introducing a graded doping profile to match the carrier recombination zone in the doped polymer, the carrier trapping, and the deterioration of electrical characteristics can be minimized while the enhancement in efficiency maintains. The finite-source dye-diffusion thermal transfer is used to produce graded doping profiles into a luminescent polymer. The effectiveness of this approach has been demonstrated in both single-layer and heterostructure devices incorporating doped polymers.

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