Redox probes to track band edge evolution of thin film oxide semiconductors in aqueous solutions

The interaction of semiconductor materials with aqueous electrolytes governs the operation of a wide range of emerging technologies, including photoelectrochemical energy conversion, chemical sensing, and iontronic devices. At the heart of these applications lies the semiconductor/electrolyte interface, where charge transfer reactions are dictated by the alignment of the semiconductor's electronic energy levels with the electrochemical potentials of species in solution. However, these band-edge positions are not fixed material properties and can evolve in response to pH, ionic composition, surface chemistry, and electrochemical bias. Developing a fundamental understanding of these dynamic interfacial processes is therefore essential for the rational design of next-generation semiconductor devices.

We are currently developing new methodologies to probe and understand semiconductor/solution interfaces. One particularly promising approach uses redox reactions with well-defined formal potentials as electrochemical markers (i.e. redox probes) to infer the positions of semiconductor band edges. Such techniques are especially valuable for nanostructured and thin-film semiconductors, where conventional methods like Mott-Schottky procedure cannot be used.