Organic Electrochemical Transistors for Energy‐Autonomous Bioelectronics: Materials, Devices, and System Integration

ABSTRACT The rapid growth of bio‐integrated electronics, ranging from epidermal wearables to deep‐tissue implants, has created an urgent need for energy‐autonomous systems capable of operating without external power. While conventional silicon‐based devices suffer from poor mechanical compliance and low energy efficiency at biological interfaces, organic electrochemical transistors (OECTs) offer a compelling alternative by combining biocompatibility, low‐voltage operation, and intrinsic signal amplification. This review examines the integration of OECTs with energy harvesting technologies, with a particular focus on self‐powered biosensing. We first outline the fundamental operating principles, highlighting how volumetric capacitance and mixed ionic‐electronic conduction enable high transconductance at low voltages, making OECTs well suited for amplifying weak physiological signals. We then review recent advances in materials and device architectures, emphasizing how organic mixed ionic‐electronic conductors govern energy efficiency and operational stability. The electrolyte plays an active role by regulating ion transport and interfacial capacitance, thereby critically influencing device performance under energy‐autonomous conditions. The core discussion focuses on system‐level integration, where OECTs interface with mechanical (triboelectric and piezoelectric), thermal, and optical energy harvesters. Key challenges, including impedance matching and rectification, are analyzed to optimize sensing performance under harvested energy inputs. Finally, we outline future directions toward fully integrated, battery‐free bioelectronic platforms.