Dual Functional Z‐Scheme Heterojunction Covalent Organic Frameworks for Bipolar‐Driven Organic Photoelectrochemical Transistor Biosensing

Abstract Organic photoelectrochemical transistor (OPECT) as a photo‐electric‐biological technology, is shown considerable potential for high‐performance detection in biological sensing. High gating effect and current is always a pursuit to improve the performances of OPECT, but to date, their inherent channel materials and invariant structure limit their further development. The challenge is addressed through a new bipolar‐driven OPECT for signal amplification and efficient modulation. Herein, inspired by self‐powered photoelectrochemical (PEC) systems, a bipolar‐driven enhancement‐mode poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) OPECT powered by a Z‐scheme COF/Cu₂O@Cu PtNCs photocathode and CdIn₂S₄ photoanode is proposed. It exhibits an enhanced gating effect and a remarkable current gain of ≈7613, which is much higher than the single‐photoelectrode ones and will have a beneficial impact on achieving sensitive, portable, and reliable sensing devices. Moreover, the sandwich system composed of multifunctional COF‐based nanomaterials for signal amplification and the target‐mediated biomimetic precipitation reaction is designed upon the photocathode, resulting in dual signal amplification and realizing the high‐performance alpha‐fetoprotein (AFP) detection with a linear range of 32 fg mL⁻¹–10 ng mL⁻¹ and a low detection limit of 22 fg mL⁻¹.