Using Heat‐Cool Processing to Change the Assembly and Photoconductive Properties of Perylene Bisimides

Abstract Thermal processing is widely used in solution‐based coating techniques or to enhance solubility, yet the impact on supramolecular self‐assembly and thin film properties remains largely unexplored. Here, we demonstrate how heating and cooling cycles modulate the self‐assembly of amino acid‐appended perylene bisimides (PBIs), influencing their structural and optoelectronic properties. Using small‐angle neutron scattering (SANS), rheology, and absorption spectroscopy, we show that heating increases fibre flexibility while cooling results in spherical aggregate formation. Additionally, we demonstrate the impact of these changes on thin film performance using nanoindentation and voltammetry. When incorporated as electron transport layers (ETLs) in perovskite solar cells, heat‐cooling reduces the series resistance from 6.33 to 4.40 Ω∙cm 2 , enhancing device efficiency. Our findings highlight the importance of thermal history in supramolecular materials and emphasise the need for strict temperature control in solution‐based coating techniques to optimise optoelectronic device performance.