Doping induced assembly of conjugated polymer into nanowires

Abstract

The control of the nanoscale morphology of the conjugated polymers(CPs) has been recognized as a key parameter that affects charge transfer property. Especially, the one-dimensional nanostructure is highly suitable for charge transfer with effective transport property of electrical carriers along the anisotropic stacking direction. Along with the line, the pre-assembly of conjugated nanowires (NWs) in the solution state has attracted attention as an alternative to the use of a post-annealing process, which enables the roll-to-roll manufacturing with a large-area production and a significant cost reduction. As representative solution processing methods, the whisker method and the mixed solvent method are widely used to give an additional driving force for assembly of the CPs. Therefore, we have introduced the doping method to simultaneously perform nanowire growth as well as doping without a physical driving force. While doping process generally used to tune the electrical property of the CPs to enhance the conductivity, we have focused on charge transfer at the contact of CPs and dopant which can trigger aggregates of the CPs. Herein, we demonstrate the doping induced assembly of P3HT into NWs by addition of F4TCNQ in chloroform as a single good solvent. The formation of the NWs can be controlled by the dopant concentration and the molecular weight of the P3HT. We observed that highly ordered NWs can be fabricated with the addition of a small amount of the dopant. The conformational change of NWs by dopant concentration is studied and correlated with doping efficiency to provide a guideline for optimization. This research might provide a useful strategy for the fabrication of doped organic semiconducting NWs with high performance in the optoelectronic device.