(226bd) Fabrication of Size-Controllable Highly Ordered P3HT Nanostructures and Analysis of Their Assembly

In previous studies, solution processing methods such as ultrasound irradiation or addition of poor solvents have been used to induce nano-scale structure formation in poly(3-hexylthiophene) (P3HT) thin-films. Concomitantly, P3HT charge carrier mobility has been reported to be enhanced, which indicates that the features formed during these processes are likely to be ordered P3HT chains that are stacked via pi-pi interactions, resulting in improved interchain charge carrier transport. Here, we present a comprehensive study of the thin-film structure-charge carrier transport property relationships within P3HT thin-films by precisely controlling development of highly ordered P3HT nanostructures. When utilized separately, ultrasound irradiation and poor solvent addition are limited in their ability to assemble P3HT nanostructures having a range of dimensions. However, in a synergistic approach, the combination of both methodologies, i.e., ultrasound irradiation coupled with poor solvent addition, P3HT nanostructures with controlled length, width and quantity have been fabricated. Field-effect hole mobility of P3HT thin-films composed of nanostructures prepared here has exhibited a clear trend related to the differentiated nanostructure dimensions and quantities. P3HT hole mobility with material having highly ordered nanostructural features has reached impressive maximum average value of 0.103cm²/V-s and corresponding mobility values have been correlated with AFM morphology and x-ray crystallography data. Further, systematic investigation based on AFM morphology, grazing incidence x-ray diffraction, and UV-Vis spectroscopy data has enabled us to successfully apply a conventional 2-step crystallization model including nucleation and growth steps to the self-assembly process of P3HT nanostructures.