Enhanced Charge Transport through Secondary Nucleation of P3HT

Printable organic electronics have developed as a cost-effective alternative to conventional inorganic electronics due to the solution processability of semiconducting polymers. The hypothesized ideal structure consists of interconnected, densely packed, aligned fibrillar domains on the mesoscale. Methods to induce an ideal morphology are limited by the self-assembling properties of poly-3-hexylthiophene (P3HT). We aim to use a type of secondary “seed” nucleation by mixing amorphous and treated P3HT to achieve the ideal microstructure. Treatment incorporates exposure of P3HT in solution to ultraviolet irradiation followed by solution aging ultimately resulting in the formation of nanofibers. Three solutions were made with 20%, 50%, and 80% treated P3HT with the balance amorphous polymer. A thin film of solution was deposited on a bottom gate, bottom contact transistor through a blade-coating technique. Using a semiconductor parameter analyzer, it was found that mixing a small amount of treated P3HT with a larger amount of amorphous polymer resulted in high charge mobility across the field effect transistor. The maximum charge carrier mobility resulted from a mixture of 20% treated P3HT suggesting that high amounts of nucleated polymer leads to precipitation and inferior performance. UV-vis spectroscopy of solution and film support this data with repeatable trends of increasing aggregate fraction with increasing amount of treated P3HT. Consistent with high charge mobilities, atomic force microscopy (AFM) shows densely packed and aligned fibers for secondary nucleated solutions. Seed nucleation demonstrates a viable method capable of reducing resources required for solution processing by nearly four times compared to the traditional method of treating the entire solution.