Manipulating Organic Semiconductor Morphology with Visible Light

A method is presented to manipulate the final morphology of roll‐to‐roll slot‐die coated poly(3‐hexylthiophene) (P3HT) by optically exciting the p‐type polymer in solution while coating. These results provide a comprehensive picture of the entire knowledge chain, from demonstrating how to apply the authors’ method to a fundamental understanding of the changes in morphology and physical properties induced by exciting P3HT while coating. By combining results from density functional theory and molecular dynamics simulations with a variety of X‐ray experiments, absorption spectroscopy, and THz spectroscopy, the relationship between morphology and physical properties of the thin film is demonstrated. Specifically, in P3HT films excited with light during deposition, changes in crystallinity and texture with more face‐on orientation and increased out‐of‐plane charge mobility are observed. Optical excitation of semiconducting polymers in solution during roll‐to‐roll slot‐die coating enables morphological manipulation of thin‐films relevant for organic photovoltaics and flexible electronics. Theoretical and experimental techniques elucidate the morphological changes upon polymer excitation from solution to thin‐film. The changes induced in the nanostructure of the thin‐film increase the out‐of‐plane electron mobility.