Structure and property development of poly(3-hexylthiophene) organogels probed with combined rheology, conductivity and small angle neutron scattering

The structural, mechanical and electrical properties of poly(3-hexylthiophene) (P3HT) organogels have been probed during the sol-gel transition through combined rheology, AC dielectric spectroscopy and small angle neutron scattering (SANS). SANS shows that structural features of P3HT gels, which are crucial for the optimization of organic photovoltaic devices, evolve throughout the gelation process. In situ structure-property analyses also demonstrate that there are very different mechanisms for the formation and dissolution of fibers and networks prepared from these polymeric semiconductors. It is determined that P3HT gels form conductive pathways that are maintained even after up to 50% of the fibers re-dissolve upon heating. P3HT organogels formed in different aromatic solvents also show differences of more than two orders of magnitude in conductivity despite having similar nanoscale fiber structures. These results demonstrate the importance of controlling the self-assembled morphology of fiber networks for maintaining optimal electronic properties. This work also highlights the potential for using organogels as flexible platforms for designing efficient organic photovoltaic devices.