Heat transfer in photovoltaic polymers and bulk‐heterojunctions investigated by scanning photothermal deflection technique

Organic semiconductors in electronic devices usually have poor thermal conduction which could trap considerable amount of heat, inducing operational instability and reducing device lifetime, limiting commercialization potential. Despite the technological essence to understand enhance heat-dissipation, related studies on organic are very limited. In this study, authors show that scanning photothermal deflection technique can be employed study transport thin films photovoltaic (OPV) polymers bulk-heterojunctions (BHJs), with a simple empirical correction for extrinsic experimental configuration. Phonons identified dominate due low carrier mobility. For OPV semiconductors, positive correlation between diffusivity molecular planarity, π– π stacking crystallinity is demonstrated. High-performance 2D such as PM6 possess values comparable alloys like stainless steel. BHJs, using polymeric acceptor retain high diffusivities compared fullerene ITIC acceptors, attributed efficient heat transfer within polymer chains. The results offer not only simple, highly customizable but sensitive method systems, also insights into phonon dynamics clinical investigations stability, pushing forward strategic material design.