Facile Surface Reconfiguration of Nanostructured P−N Diode with Bipolar Photoresponse for Inherently Multiplexed Analyte Sensor

Abstract Photoelectrochemical sensing within complex biochemical environments typically necessitates the simultaneous determination of multiple analytes, as single-parameter measurements provide limited information. However, most existing biosensing platforms encode analyte information within a single signal dimension, which restricts their ability to achieve intrinsic multiplexing. Here, we report a polarity-encoded photoelectrochemical biosensing platform based on a wavelength-resolved p-AlGaN/n-GaN heterojunction. In this system, photocurrent polarity functions as an additional signal dimension beyond conventional amplitude-based encoding. The device exhibits illumination-dependent polarity switching, enabling analyte-specific signal transduction. Regulation of carrier transport across the heterojunction generates bipolar photoresponses, in which polarity determines analyte identity while current amplitude remains proportional to concentration. This mechanism enables wavelength-resolved dual-analyte detection on a single electrode, as demonstrated by the selective discrimination of glucose and hydrogen peroxide under different illumination conditions. Moreover, surface modification with RuO2 enhances interfacial charge-transfer kinetics and improves carrier utilization efficiency, leading to amplified bipolar signals and improved detection performance. The system achieves sensitivities of 723 μA mM−1 cm−2 and 0.11 mA mM−1 cm−2 for hydrogen peroxide (H2O2) and glucose, respectively. This work establishes a polarity-resolved signal-encoding strategy for intrinsically multiplexed photoelectrochemical biosensing.