Additive induced crystallization of a twisted perylene diimide dimer within a polymer matrix.

The controlled aggregation of organic π-conjugated molecular semiconductors within a host material (often a polymer) is important for obtaining appropriate organic film morphologies and mechanical properties for optoelectronic applications. In this study, we demonstrate how we have challenged the twisting effect in perylene diimide dimers, which is known to hinder their aggregation. Indeed, a twisted N-annulated perylene diimide dimer (tPDI2N-EH) can be induced to form crystalline aggregates within a host poly-3-hexylthiophene (P3HT) polymer matrix using solution processing. The size of the aggregates can be controlled using varying amounts of the common processing solvent additive 1,8-diiodooctane (DIO) during film formation, by changing the concentration of the molecule within the polymer film, and by adjusting the film drying time. A combination of UV-visible spectroscopy, fluorescence microscopy, cross-polarized light microscopy, and atomic force microscopy were used to characterize the organic films.