Probing the Electronic Band Structure of Emerging Chalcogenide Absorbers for Photoelectrochemistry

Accurate determination of the conduction band minimum (CBM) is essential for designing efficient photoelectrochemical (PEC) systems, as it governs charge separation, transfer, and catalytic activity at interfaces. However, conventional techniques often lack the sensitivity or resolution needed to reliably measure absolute CBM positions. In this work, we directly determine the absolute energy positions of the valence band maximum (VBM) and CBM from key chalcogenide semiconductors (Cu3BiS3, Cu(In,Ga)S2, Sb2S3, Ag2CuZnSnS4, and Ag2CuZnSn(S,Se)4) as well as the most significant hole and electron transport layers (HTL/ETL) for PEC applications using a combined approach of ultraviolet photoelectron spectroscopy (UPS) and the less-explored low-energy inverse photoelectron spectroscopy (LEIPS). These measurements revealed quantitative band-edge positions essential for understanding interfacial energetics and alignment with redox potential reactions. Our results provide a clear and robust framework for tailoring semiconductor interfaces with electrolytes or transport layers, thereby supporting targeted material screening and advancing the design of high-performance solar-to-X systems.