Confinement Effects on the Crystalline Features of Poly(9,9-dioctylfluorene)

TL;DR

This study investigates how two-dimensional confinement within nanopores influences the crystalline structure of poly(9,9-dioctylfluorene), revealing methods to produce textured nanowires with tunable orientations for optoelectronic applications.

Contribution

It demonstrates the fabrication of ordered PFO nanowires with controlled crystal orientation using confinement and specific crystallization strategies, advancing polymer nanostructure engineering.

Findings

Confinement induces highly textured nanowires with tunable crystal orientation.

Appropriate crystallization conditions enable extended-chain crystals in confinement.

Fabrication method is simple and suitable for device applications.

Abstract

Typical device architectures in polymer-based optoelectronic devices, such as field effect transistors organic light emitting diodes and photovoltaic cells include sub-100 nm semiconducting polymer thin-film active layers, whose microstructure is likely to be subject to finite-size effects. The aim of this study was to investigate effect of the two-dimensional spatial confinement on the internal structure of the semiconducting polymer poly(9,9-dioctylfluorene) (PFO). PFO melts were confined inside the cylindrical nanopores of anodic aluminium oxide (AAO) templates and crystallized via two crystallization strategies, namely, in the presence or in the absence of a surface bulk reservoir located at the template surface. We show that highly textured semiconducting nanowires with tuneable crystal orientation can be thus produced. Moreover, our results indicate that employing the appropriate crystallization conditions extended-chain crystals can be formed in confinement. The results presented here demonstrate the simple fabrication and crystal engineering of ordered arrays of PFO nanowires; a system with potential applications in devices where anisotropic optical properties are required, such as polarized electroluminescence, waveguiding, optical switching, lasing, etc.