Preparation of Porous Poly(3-hexylthiophene) by Freeze-Dry Method and Its Application to Organic Photovoltaics

Poly(3-hexylthiophene)(P3HT) with a microporous network structure was prepared from a 1% p-xylene solution by freeze-dry method. Scanning electron microscopy (SEM) showed P3HT molecules formed swollen gel-like structures with different extent of compactness depending on the length of the aggregation period. Absorption spectrum of this P3HT film showed a characteristic peak at 620 nm, which indicated a high degree of order between polymer chains. Photoluminescence (PL) of this highly ordered P3HT film appeared at 712 nm revealing large extent of pi-pi stacking between P3HT molecules in the freeze-dry film. Both absorption and photoluminescence results indicated that the original aggregated states of P3HT molecules in gel form had been preserved throughout the freeze-dry operation. X-ray diffraction of the annealed samples showed a strong characteristic peak for the side chain aggregation at 2 theta = 5.1 degrees, which proved that the freeze-dry film was with highly order structure. The interconnected and highly ordered P3HT film is used in the study of organic photovoltaics (OPV) after applying an n-type semiconductor to the surface of the dry porous fibers. A prototype OPV device with power conversion efficiency of 1.47% was prepared by this method. (c) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 233-240, 2011