Ion Compensation-Assisted Photolithography Enables High-Resolution Electrolytes for Neuromorphic Transistors

High-density organic electrochemical transistor (OECT) arrays are essential for neuromorphic computing and bioelectronic interfaces, but progress has been limited by the low resolution of electrolyte patterning. Although conventional photolithography offers high feature resolution, it involves a fundamental trade-off among spatial resolution, ionic capacitance, and stability in the electrolyte. Here we report an ion compensation-assisted photolithography (ICAP) strategy that yields electrolyte micro-patterns combining high precision, high capacitance and high stability. A molecularly engineered electrolyte forms, under UV exposure, a physicochemical dual cross-linked network with strong solvent resistance and hydrophobicity, which suppresses swelling during both aqueous development and the subsequent ion-compensation step, preserving pattern fidelity. Ion compensation then restores and enhances the mobile-ion content, increasing areal capacitance. The resulting electrolytes achieve a record 2 μm resolution, 15.6 μF cm^-2 capacitance, and strong thermal stability from - 50 to 200 °C. Integrated into OECTs, the ICAP-patterned electrolytes suppress crosstalk by 97.6% and boost on/off ratios by 325%, reducing parasitic coupling by more than 40 times compared to unpatterned arrays. The method is compatible with p-type and n-type organic semiconductors and inorganic oxides, providing a versatile route to scalable neuromorphic circuits and advanced bioelectronics.