Heterojunction Gate-Empowered OPECT Aptasensing: A Valid Protocol for Realizing High Current Gain at Low Electron...

Achieving high current gain in organic photoelectrochemical transistors (OPECTs) under low-concentration electron donor conditions is of critical importance for enhancing device stability and extending operational lifetime. In this work, we proposed a simple but effective heterojunction engineering strategy to gate the OPECT, achieving a current gain of up to 3 orders of magnitude with 1 mM ascorbic acid (AA), thereby overcoming the reliance on high-concentration AA in conventional OPECT systems. Benefiting from the enhanced photoelectric conversion efficiency of the MnIn₂S₄-ZnIn₂S₄ heterojunction gate, the OPECT device exhibited superior modulation performance to that of the pure MnIn₂S₄ or ZnIn₂S₄ gate. By systematically characterizing the gate and integrating theoretical analysis, an in-depth investigation into the interfacial charge transfer mechanism and the gating effect of the heterojunction gate was conducted. As a proof of concept, the feasibility and practicality of the OPECT system in aptasensing were validated by using the emerging contaminant nonylphenol in water as the target analyte. This study achieved high current gain in the OPECT under low AA requirements through an effective heterojunction engineering strategy, offering a promising approach for the development of a new generation of high-performance, long-life span OPECT sensing technology.