On the Interplay between Molecular Packing and Optical Response in Thin Films for Organic Photovoltaics

Limited control over the complex morphology exhibited by organic materials in the solid phase constitutes one of the greatest challenges to power conversion enhancement in the field of organic photovoltaics. Often, this problem is made worse by the molecular architecture of the building blocks engineered with complex structures that make the mechanisms of self-organization less straightforward and less efficient. Here, we present the computational study of a small-molecule donor with a simple architecture whose absorption spectrum in thin film experiences a dramatic change upon thermal treatment. In our present study, this change is rationalized in terms of reorganization of the molecular packing within the film. This reorganization is described in its microscopic details: the results of our simulations provide a plausible picture of the macroscopic thin-film morphology, thus offering valuable hints on how to improve the control of morphology in molecular solids.