Morphology control and nanoscale patterning of small molecule organic thin films

Abstract

We present methods for nanostructuring organic thin films for organic photovoltaic (OPV) devices. Using the glancing angle deposition (GLAD) technique, we fabricate a variety of columnar morphologies of metal phthalocyanine (MPc) materials that can be used as structured donor layers in OPV devices. We leverage this capability with block copolymer surface patterning techniques to achieve perfectly periodic columnar arrays while providing additional control over column dimensions, spacing, and density. Our investigation employs hexagonal seed patterns of platinum on silicon and we vary the seed spacing between 40 nm and 60 nm. We find that pattern resemblance begins to fade when the film thickness exceeds the seed spacing. We compare the film evolution between vertical post and slanted post morphologies, and use advanced substrate motion techniques to constrain column diameters. We conclude by addressing the compatibility of surface patterning with device fabrication. Patterned ITO surfaces and SiO₂ seed patterns are shown.