LAUSR

Monitoring dissolved oxygen is essential to marine research, but the high redox potentials required to drive sensing reactions have posed an ongoing instability issue in the sensors. Here, a novel dual‐gate configuration for organic electrochemical transistors that extends the device electrochemical stability window is demonstrated. This paper presents the sensor operating principle that relates the channel conductance to potentials on the two gates. This broadly applicable design allows a large potential to be applied between the gates for sensing analytes, while synergistically modulating the channel within a lower potential range to maintain the stability of the semiconductor. Specifically, the sensor achieves a detection limit of 0.3 ppm dissolved oxygen concentration in seawater, with a sensitivity of 222 µA cm−2 ppm−1 for concentrations below 5 ppm. The device demonstrates reliable operation over 5 days and is capable of monitoring oxygenation changes arising from the photosynthesis cycles of saltwater macro‐algae. This dual‐gate configuration serves to extend the sensor operating voltage window and improves device stability. Thus, this new configuration provides a new type of compact, robust sensor for marine research, and opportunities in other fields ranging from waste‐water management to bioelectronics.