Lattice Substitution Induced Fast Charge Transport in Integrated and Flexible Organic Photoelectrochemical Transistors for Portable Sensing.

Timely and on-site biochemical monitoring is highly desired in healthcare systems and smart cities. However, known sensor technologies struggle to combine technologically relevant metrics of portability, sensitivity, and reliability due to their difficulties in integrating multiple functions (e.g., target recognition, signal amplification) into a single sensing platform. Here, an integrated and portable sensing device (named IP-OPECT) that combines photoelectrochemical sensor-gated organic electrochemical transistor units and hydrogel electrolyte designs is presented to address these challenges, enabling sensitive and on-site biochemical detection. Theoretical calculations reveal that elemental lattice substitution in the photoelectrode not only suppresses the recombination of photogenerated electron-hole pairs but also improves electron transfer kinetics, ultimately enhancing the optoelectronic properties. As a proof-of-concept, we demonstrate its use in detecting varying concentrations of ochratoxin A (OTA) from contaminated commercial coffee samples, achieving an accuracy of over 96.7%. Additionally, the intrinsically flexible hydrogel electrolyte covering the electrode surface ensures long-term operation of devices, with stable photocurrent signals under different bending angles (0-180°) and over 1000 bending cycles. These results further underscore the sensory capabilities and portability of as-prepared IP-OPECT sensing devices for OTA detection as well as other biochemicals requiring real-time and on-site monitoring within the IoT ecosystem.