Insights into Excimer Formation Factors from Detailed Structural and Photophysical Studies in the Solid‐State

Abstract Solid‐state luminescent materials are essential for the development of optoelectronic devices like lasers, sensors, and organic light‐emitting diodes. Organic molecules reveal several benefits like stability, costs, and environmental compatibility compared to metal‐based materials. As common organic fluorophores often suffer from aggregation‐caused quenching, different strategies have been established to overcome this quenching, which are mainly based on intramolecular modifications. Controlling the photophysical properties via intermolecular interactions is more challenging and less investigated. The formation of excited dimers (excimers) bears great potential for obtaining efficient solid‐state luminescent materials. As the excimer‐formation process is strongly dependent on the non‐covalent interactions, a full understanding of the structure–property relationship is essential. In this study, structurally simple thiophosphoranyl anthracene excimers and the dependency of the photophysical properties on the solid‐state arrangement are investigated. Through crystallization of polymorphs and co‐crystals, the resulting intermolecular interactions have been modulated over a broad range. Novel insights into the excimer formation factors and the dependence of the photophysical properties on the intermolecular interactions are obtained. This study will help in the development and controlling the photophysical properties of solid‐state luminescent materials.