Improvement of morphological and electrical properties in poly (3-hexylthiophene-2, 5-diyl) Films Formed by Thermal Annealing in the presence of electric field during the solvent drying step

The morphological and electrical properties of poly(3-hexylthiophene-2,5-diyl) (P3HT) films play an important role in the performance of optoelectronic devices fabricated from them, especially organic solar cells. Higher crystallinity in P3HT films can be achieved by application of electric field during solvent drying when the film is formed at a temperature higher than the glass transition temperature. The improvement in P3HT film crystallinity is confirmed with x-ray diffraction measurements. The hole mobility in the improved films, determined by fabricating `hole-only´ devices with P3HT films, is found to be significantly higher than the hole mobility in films formed without application of electric field. Both the crystallinity and hole mobility in P3HT films monotonically increases with applied electric field during the solvent drying step. The reasons for these observations are explored with the help of computer simulations.