Spin‐Enhanced Magneto‐Photogating for High Transconductance at Zero Bias in Organic Electrochemical Transistors

ABSTRACT Organic electrochemical transistors (OECTs) exhibit high transconductance but typically require continuously applied, non‐zero external gate bias, limiting their ultra‐low‐power operation. While magneto‐photo coupling has driven advancements in photocatalysis, photoelectrochemical water splitting, and electronics, yet its potential in transconductance modulation remains largely underexplored. Here, a universal magneto‐photo‐gated OECT (MPG‐OECT) was proposed, which combines an Au/Fe 2 O 3 /TiNTs gate with a hybridization chain reaction to achieve low‐power, high‐sensitivity modulation. The device architecture was based on the combined utilization of well‐established photoelectrochemical processes and magnetic‐field‐assisted effects, which cooperatively enhance the effective photovoltage applied to the PEDOT:PSS channel. Under the dual stimulations from optical and magnetic fields, the MPG‐OECT exhibits a transconductance enhancement of approximately 300% compared with purely photonic gating, even at zero electrical gate bias ( V G = 0). First‐principles calculations reveal that spin‐selective transport, recombination suppression, and magnetic anisotropy collectively contribute to this enhanced performance. The feasibility of the MPG‐OECT was further demonstrated through experiments using cardiac troponin I (cTnI) as the target, achieving a detection limit of 0.31 pg mL − 1 and highlighting its strong potential for practical applications. This multifield gating strategy establishes a new paradigm for low‐power, high‐transconductance OECTs, opening new opportunities for magnetic sensing, integrated logic devices, and bioelectronics interfaces.