Solvent-Assistant Room Temperature Nanoimprinting-InducedMolecular Orientation in Poly(3-hexylthiophene) Nanopillars.

Nanoimprintinghas been well explored to create nanostructures and to induce molecularorientation in conjugated polymer thin films. We demonstrate herethat large area poly(3-hexylthiophene) (P3HT) nanopillar arrays canbe fabricated by a simple, cost-effective nanoimprinting method ina solvent-swollen plasticized state at room temperature. In addition,the solvent-assistant room-temperature nanoimprinting induces face-onchain alignment in the P3HT nanopillars; i.e., the π–πstacking of P3HT is aligned normal to the substrate, favorable fororganic photovoltaic cell applications. The face-on chain alignmentsolely depends on the diameters of nanopores defined in the nanoimprintingmold, rather than on the initial chain orientation in unprocessedthin films. Furthermore, a critical dimension of ca. 85 nm in diameteris found to be essentially needed to induce the face-on chain alignmentwithin the nanopillars. [ABSTRACT FROM AUTHOR]