The solution-processible semiconducting polymer poly(3-hexyithiophene) (P3HT) was produced by a sequence of monomer synthesis, chemical polymerization and solution phase film growth.
The fundamental energy gap of the material was determined from the optical absorption spectrum to be 2.14 eV, in agreement with previous measurements on electrochemically synthesized films of P3HT.
A thin film photovoltaic junction of p-type P3HT with indium-tin oxide (ITO) glass showed two peaks in its photovoltaic action spectrum: a normal peak corresponding to the primary absorption process of the polymer and a larger, inverse polarity peak thought to be due to photo-ionization of charge transfer complexes formed at the polymer-ITO interface.
The Hall mobility of p-type P3HT was measured and found to be rather low (about 0.25 x 10-5 m 2 V-~ s-l). However, the material initially produced from solution was largely amorphous, and ways of improving the mobility by means of increasing the alignment of the polymer chains and increasing the crystallinity were investigated.
Stretch afignment of the polymer chains induced a general increase in conductivity, predominantly in the stretch direction, and this was believed to be due entirely to an increase in the mobility. The effects of annealing on the electrical properties and structure of P3HT are also reported in this work.