Session: 03-01-02: Annual Conference-Wide Symposium on Additive Manufacturing

Paper Number: 150286

150286 - Nanostructures of Poly(3-Hexylthiophene) Wrapping Carbon Nanotubes in Mechano-Optoelectronic Thin Films 

Mechano-optoelectronic (MO) thin films exhibit strain-sensitive optoelectronic properties due to varying nanostructures of conjugated polymers of the MO thin films subjected to mechanical deformation. MO thin films were fabricated in Ryu’s previous studies by spin-coating poly(3-hexylthiophene) (P3HT) and [6,6] phenyl-C61-butyric acid methyl ester (PCBM) in 1,2-dichlorobenzene solution on a flexible substrate, and the P3HT and PCBM were shown to form p-n bulk heterojunction (BHJ) structures in the thin films. The MO thin films have been used as a self-powered strain sensing component as the MO thin films-based strain sensor generated direct current (DC) by absorbing radiant energy from various sources (e.g., sunlight, luminescent functional constituent) and the generated DC changes its magnitude with applied mechanical strain. It is thought that the unique MO properties are attributed mainly to increased light absorption by conjugated polymers that are reorganized to be in MO-favorable nanostructures after the MO thin films are deformed.

In this study, we study the effect of carbon nanotubes in nanostructures of P3HTs through experiments and simulations. It is known that carbon nanotubes (CNTs) non-covalently wrap around the P3HTs. So, we hypothesize that doping CNTs in P3HT-based thin films could help align in the strain direction when the MO thin films are stretched. It was already reported that doping multi-walled carbon nanotubes (MWNTs) in the MO thin films improved strain sensing sensitivity (i.e., gage factor), which seems to result from MWNTs’ effects on the strain-induced alignment of P3HTs in the strain direction. We employ small angle X-ray scattering (SAXS) and ultraviolet visible (UV-Vis) spectroscopy with polarized beams for characterization of P3HTs’ nanostructures in MO thin films stretched at various tensile strains. 

First, MO inks are formulated using P3HTs with and without CNTs in different solvents, such as 1,2-dichlorobenzene, p-xylene, and toluene. The formulated MO inks are used for fabricating MO thin films using a spin-coating and an air-brushing technique to assess processibility of the MO ink and quality of the MO thin films. Second, surface morphology and thickness of the MO thin films are characterized using a scanning electron microscopy (SEM) and an optical microscopy. The P3HTs’ nanostructures of the MO thin films are characterized using a grazing-incidence SAXS and a UV-Vis spectroscopy with polarized beams. Third, using large-scale atomic/molecular massively parallel simulator (LAMMPS), P3HTs and CNTs are modeled and molecular dynamics (MD) simulations are conducted to understand how CNTs affect formation of P3HTs’ nano-structures. Last, DC-based strain sensors are fabricated using the MO thin films and tested for characterizing the strain sensors’ sensing capability as well as optoelectronic properties. The fabricated strain sensors are subjected to cyclic tensile loading/unloading cycles while measuring DC under light from a solar simulator.

Presenting Author: Cason Jones New Mexico Tech

Presenting Author Biography: Cason Jones

Authors:

Cason Jones New Mexico Tech
Adrian Salustri New Mexico Tech
Jayden Hogue New Mexico Tech
Kyungtae Kim Center for Integrated Nanotechnologies, Los Alamos National Lab
Myeong-Lok Seol NASA Ames Research Center
Jessica Koehne NASA Ames Research Center
Donghyeon Ryu New Mexico Tech