Fluorene‐Arylamine Copolymers: Separable Control of Hole Transport and Light Emission Through Composition and Conformation

ABSTRACT Suitable model polymer systems enable systematic studies that can progress understanding of structure–property relationships in these chemically diverse materials. To this end, the hole mobility of four fluorene‐arylamine copolymers containing varying ratios of 9,9‐dioctylfluorene and butyl‐substituted phenylenediamine has been studied. The copolymers with longer sequences of fluorene units can adopt the chain‐extended β ‐phase conformation, and its effect on transport is also investigated. The room temperature hole mobility of the fluorene homopolymer, poly(9,9‐dioctylfluorene), is drastically reduced by copolymerization of 5% arylamine units due to trapping at the arylamine sites. With increasing arylamine percentage, the mobility rises due to the commencement of direct arylamine‐to‐arylamine transport. Air photoemission spectroscopy measurements reveal two separate contributions to the photoemission signal whose intensities vary with composition, rather than a single energy level that shifts continuously from fluorene to arylamine, as has sometimes been assumed in transport models. This work demonstrates both that mobility can be controlled over a large range in these copolymers and that the role of fluorene β ‐phase formation is secondary here to chemical composition. Conversely, the light emission properties are strongly affected by conformation. The transport and emission characteristics are thereby separable, consistent with the observed multifunctional nature of state‐of‐the‐art complex copolymers.