Light-emitting diodes using n-type conducting polymer: Poly(p-pyridyl vinylene)

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Abstract
A yellow‐orange electroluminescent (EL) diode using an n‐type conducting polymer, poly(p‐pyridyl vinylene) (PPyV), as an emitting layer has been demonstrated and its EL properties are discussed. The EL emission of this device can be interpreted in terms of radiative recombination of the singlet polaron exciton formed by the injection of electrons and holes. Although the EL intensity of the PPyV light‐emitting diode is weak, yellowish‐orange EL emissions were clearly observed under normal room light. Changing from the PPyV EL device to the PPV‖PPyV EL device using poly(p‐phenylene vinylene) (PPV) as a hole‐transporting layer increased the maximum quantum efficiency from 0.0065% to 0.08% photons per electron. Detailed electrical and optical properties for these diodes with aluminum as the electron‐injecting contacts are presented and an improved quantum efficiency for light emission has been achieved.