Optical and Structural Properties of MEH-PPV: C60-Based Structures

Abstract

Structural evolution and optical properties in blends of poly[2-methoxy,5-(20-ethylhexyloxy)-1,4,-phenylene-vinylene] and fullerene (C60) upon thermal treatment at different temperatures have been investigated using X-ray diffraction, absorption, and photoluminescence measurements. From the XRD results, the as-cast film exhibited three broad diffraction peaks at around 2 Θ = 6°, 12° and 21.7° accompanied with two well-defined diffraction peaks at wide angle at about 2 Θ = 30.7° and 35.5°. The diffraction peaks at around 2 Θ = 6° and 21.7 were attributed to MEH-PPV while the diffraction peaks at around 2 Θ = 12°, 30.7° and 35.5° were originated from the effect of the incorporation of C60 molecules in the polymer matrix. As the temperature is increased to 125°C, the intensities of the diffraction peaks at wide angles increased and the peak at around 2Θ = 12° decreased progressively then at 125°C it disappeared completely. When the temperature is increased further to 180°C this peak reappears again and the diffraction peaks at 2 Θ = 30.7° and 35.5° dissipated. These results suggested the occurrence of a crystalline transition in the composite film at about 125°C. In addition to that it revealed that the amorphous domain was increased with annealing at elevated temperatures. The optical properties of MEH-PPV: C60 composites showed a strong dependence with the structural evolution with thermal treatment.