The ordering of poly(3-hexylthiophene) (P3HT) molecules in dilute P3HT/chloroform solutions was accelerated by adding small amounts of concentrated H2SO4. The concentrated H2SO4 stimulates the nucleation of crystals, which controls the overall rate of P3HT crystallization. Dispersed nuclei spur P3HT solution crystallization, and adsorbed nuclei induce P3HT crystallization on substrates. By AFM, the morphology of P3HT nanowhiskers prepared in solution differ from those prepared on substrates, and nanowhisker structure and growth kinetics was further investigated using Raman spectroscopy and UV-vis adsorption spectroscopy. All P3HT nanowhiskers are well-ordered.