Structural Hierarchy of Functional Block Copolymer System Induced by Electrohydrodynamic Lithography

The advantages arising from anisotropic functional block copolymer nanostructures hold great promise for applications in electro-optical devices made of organic materials. Efficient hierarchical structures are formed exhibiting order on several length scales by using electrohydrodynamic patterning approach. Initially block copolymer microdomains oriented parallel to the substrate are destabilized by electric fields yielding formation of microstructures perpendicular to the substrate. Within each fabricated microstructures the cylinders are aligned parallel with respect to the electric field lines. An internal vertical alignment of the copolymers nanometric domains exhibits an additional molecular orientation thus, providing a straightforward path for exciton transport to the donor-acceptor interface essential for the enhanced charge generations. Inside the superstructured films, ordered arrays of nanocrystals of the constituting block are aligned in smectic phase giving rise to linear dichroism. Controlled alignment of the nanodomians improves the charge conduction toward the device electrodes. These findings, while establishing a straightforward strategy to produce oriented assemblies of nanodomains of electroactive polymers, open a new avenue for nanotechnologal applications and are very promising for optoelectronic applications, especially in photovoltaic devices.