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 π–π 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 2θ = 5.1°, 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. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.