Photophysical Properties, Self-Assembled Thin Films, and Light-Emitting Diodes of Poly (p -pyridylvinylene) s and Poly(p-pyridinium vinylene)s

Poly(p-pyridylvinylene) (PP_yV) and its derivatives have been synthesized, and their optical properties have been studied in solutions and thin films. These conjugated polymers are highly photoluminescent in both their neutral and protonated states. Polymer thin films and concentrated solutions show photoluminescence (PL) from excimeric states, which contributes to the observed red-shift in the emission spectra and the low PL quantum yields relative to dilute solutions. Self-assembled polymer thin films of poly(pyridinium vinylene) with sulfonated polystyrene or sulfonated polyaniline have been prepared by the electrostatic deposition method. Various deposition conditions were investigated and the films examined by atomic force microscopy (APM). Light-emitting devices (LEDs) with several different architectures were made from this class of polymers and evaluated. The polymer thin films were spin-coated from solution, and the devices emit generally orange-red colors consistent with their PL spectra. The device made from poly(3-n-butyl-p-pyridylvinylene) with the configuration ITO/Bu-PPyV/Al has an external quantum efficiency of 0.02%. The introduction of a hole transport layer (poly(p -phenylenevinylene), PPV) between the Bu-PP_yV and ITO layers improves the quantum efficiency of the device (up to 0.05%), reduces the operating voltage and prolongs the life of the device.