Interfacial Engineering of Rubrene Thin Films with Crosslinked Polymer Layers

The controlled crystallization of organic semiconductors remains a key challenge for achieving reproducible performance in organic electronic devices. In this study, the influence of polymer interlayers on the polycrystalline growth of organic semiconductors was systematically investigated. Rubrene thin films deposited on UV-modified polystyrene interlayers exhibited spherulitic crystallization, with uniform orthorhombic domains forming exclusively on IPA-rinsed, crosslinked PS (PS-net). Polarized optical microscopy revealed a time-dependent nucleation-and-growth mechanism, while temperature-dependent studies identified a narrow 170–180°C window for stabilizing orthorhombic domains. Surface morphology and surface energy analyses indicated that roughness and interfacial energy contribute partially, but cannot fully account for the observed crystallization behavior. Differential scanning calorimetry and solubility tests suggested that the thermal dynamics of the interlayer and the removal of chain-scission fragments play critical roles in enabling molecular diffusion and ordering. Taken together, these findings provide new insights into how polymer interlayers can be engineered to direct the crystallization pathways of small-molecule semiconductors, offering valuable guidance for the rational design of organic electronic materials.