Synthesis and characterization of color tunable electro-luminescent polymer by blending oxadiazole containing polymer

The electro-optical properties of novel polymers such as poly(phenylenevinylene-alt-N-hexylcarbazolevinylene) ([poly(PPV-N-hexylCvz)]) poly[1′,4′-phenylene-1′′,4′′-(2′′-(2′′′′-ethylhexyloxy))phenylene-2,5-(1′′′,4′′′-phenylene)-1,3,4-oxadiazolyl] (PPEPPO) and their blends were characterized. The photoluminescence and electroluminescence (EL) spectra of the blend films composed of poly(PPV-N-hexylCvz) and PPEPPO were mainly contributed from the luminance of poly(PPV-N-hexylCvz) even at low poly(PPV-N-hexylCVz) ratios. Remarkably enhanced EL efficiency was observed as increase the ratio of PPEPPO. This probably results from the energy transfer in the excited state from PPEPPO, with a larger band gap, to poly(PPV-N-hexylCvz) with a smaller band gap. When the ratio of PPEPPO was increased, we observed color emission from green to blue and slightly increased the turn-on voltage compared to poly(PPV-N-hexylCvz). The forward bias turn-on voltage for the light emitting diodes are 5 V for poly(PPV-N-hexylCvz) and 40 V for PPEPPO, respectively.