Tuning Local Molecular Orientation-Composition Correlations in Binary Organic Thin Films by Solution Shearing

A general impact of solution shearing on molecular orientation correlation is observed in polymer:fullerene organic solar cells in which one of the components forms fibrils or aggregates. Further investigation with polarized soft X-ray scattering reveals that solution shearing induces more face-to-face orientation relative to the interface of two components compared to spin-coating. This impact is shearing speed dependent, that is, slow shearing speed can induce more face-to-face orientation than a fast shearing speed. These results demonstrate that solution shearing is an effective method to control the relative molecular orientation. Solution shearing can also modify the domain size and average composition variations.