Compositionally Tuned Al–Mn–Ru Thin Films for Advancing Silicon Photoelectrodes in Light Harvesting and Electronic Conductivity

The advancement of silicon (Si)-based photoelectrodes for photoelectrochemical (PEC) energy conversion is no longer limited by surface catalytic activity, but rather by persistent challenges in suboptimal light harvesting and low electronic conductivity. Addressing these bottlenecks is crucial to unlock the full potential of Si-based systems for solar fuel applications. Here, we present a tunable strategy employing Al–Mn–Ru thin films conformally coated on Si wafers, where precise adjustment of the Al, Mn, and Ru atomic ratios enhances near-infrared light absorption and electrical conductivity. The resulting films demonstrate broad-spectrum light absorption from 250 to 1400 nm and achieve up to a two-order-of-magnitude reduction in ohmic resistance, indicating improved charge carrier transport properties. Structural and spectroscopic analyses reveal that compositional variations across the samples influence light harvesting and conductivity, while trends in surface potential and chromaticity illustrate the critical relationship between film composition and material properties. This work establishes a versatile platform for engineering Si-based materials with enhanced optoelectronic characteristics, paving the way for future development of high-performance PEC devices for solar fuel applications.