Steering S-scheme charge transfer via interfacial dipoles induced by amine-containing polyelectrolytes

The lack of a robust interfacial driving source over multicomponent photocatalysts is an essential contributor to the sluggish spatial charge transfer across the heterointerface and severe carrier recombination, thereby rendering maneuvering charge transfer of composite materials a thorny issue. Herein, we demonstrate an electric dipole moment-driven charge transfer photosystem utilizing amine-containing polyfluorene polyelectrolyte (i.e., PFN) and inorganic semiconductor matrices (i.e., WO₃) as the building blocks to direct the interfacial charge transfer, effectively targeting the photoexcited charge carriers to the active sites. Experimental results and theoretical simulations reveal that the electronic coupling interaction between the pendant electron-rich amine groups along the PFN backbone and WO₃ surface enables the nonuniform charge distribution at the interface over the WO₃@PFN heterojunction, which ultimately fosters the formation of interfacial dipoles oriented from conjugated macromolecular backbone of PFN to the surface of WO₃ matrices. The interfacial dipoles with excellent charge transfer kinetics spontaneously activate the unidirectional and accelerated S-scheme charge motion from the WO₃ framework to the conjugated chain of PFN due to the suitable band offsets at the interface, thus endowing WO₃@PFN heterostructures with a significantly enhanced net efficiency of photoactivity. These findings would provide some insights into the design of advanced heterojunction photocatalysts for solar energy conversion as well as the study of the working mechanism of polyelectrolyte interlayers in optoelectronic devices. [Figure not available: see fulltext.]