Tunable photodetector performance through electrolyte redox potential engineering

The semiconductor/electrolyte interface is the core region for the separation and transport of photo generated charge carriers in photoelectrochemical (PEC) photodetectors. The band arrangement of the interface has a significant impact on the electrochemical performance of the system. Here, three electrolytes with different redox potentials are designed and configured using the Nernst equation and Fe3+/Fe2+ as the redox pair and systematically investigated the influence of electrolyte redox potential on the photoelectrochemical performance of P-type Si and N-type WO3 electrodes. The band structures of Si and WO3 are estimated using the Mott–Schottky test. The electrochemical test results indicate that the change in electrolyte redox potential will significantly affect the photoresponsivity of the sample: as the redox potential decreased. The dark current decreased by over 23-fold for Si (0.251–0.011 mA/cm2) and 60-fold for WO3 (1.87–0.029 mA/cm2) as the redox potential decreased. With the change of electrolyte redox potential, the photocurrent density increased by twofold for Si (0.0065–0.0145 μA/cm2) and 25-fold for WO3 (0.0523–1.293 μA/cm2). These effects originate from the band bending modulation driven by the electrolyte redox potential at the semiconductor/electrolyte interface. This work uses the electrolyte as a tunable medium for interfacial band engineering, offering a viable strategy for optimizing and designing high-performance photoelectrochemical detectors.