THE INFLUENCE OF HEAT TREATMENT ON THE CHARACTERISTIC OF POLY(3-HEXYLTHIOPHENE-2,5-DIYL)P3HT AND):[6,6] PHENYL-C71- BUTYRIC ACID METHYL ESTER (PCBM)BLEND

The influence of post thermal annealing of thin poly (3-hexylthiophene) film, and poly (3-hexylthiophene):[6,6] phenyl C-71 butyric acid methyl ester (P3HT:PC71BM) composite were investigated regarding their structural, morphology, optical and electrical properties. The structural properties were studied by x-ray diffraction analysis. It was found that the crystallinity of both films increased upon annealing temperature, and reduce with addition of fullerene molecules to P3HT. The surface morphology of prepared films also studied by Field Emission Scanning Electron Microscope (FESEM) and Atomic Force Microscope (AFM). The first one showed that P3HT films has a smooth and homogenous morphology with small cubic crystals and after blending with PC71BM, the surface exhibited aggregates of needle or rod-like shapes. AFM measurements for all prepared films show that the average grain size and the surface roughness increases with the increase of annealing temperature. The optical measurements show that P3HT and its blend films exhibited strong optical absorption in the visible region. The absorption of the annealed P3HT:PC71BM blend films become strong and red shifted in the wavelength region ascribe to P3HT, while the absorption due to PCBM contribution does not change. Hall measurements of P3HT and the blend films showed that the mobility increases with the increase of annealing temperature while the concentration of charge carriers showed opposite manner.