A Solution‐Based Deposition Method Enabling Pigment Blue Edible Electrochemical Transistors

Abstract Copper(II) phthalocyanine (CuPc), also known as Pigment Blue 15, is a widely utilized pigment renowned for its exceptional semiconducting properties when refined to electronic‐grade purity. Recent studies have confirmed its safety if ingested at doses required for essential active components in edible electronics for advanced gastrointestinal tract monitoring. Since in‐body operations impose stringent safety constraints on operational biases, the development of transistors with high transconductance at low voltages is required to ensure adequate amplification gain. This study presents a simple and cost‐effective method for producing solution‐processed CuPc films characterized by a unique porous microstructure that facilitates efficient volumetric ion uptake and mixed ionic‐electronic conductivity in electrolyte‐gated devices. These porous films exhibit capacitance 30 times greater than compact CuPc films produced through conventional physical vapor deposition methods. The resulting edible transistors demonstrate On/Off ratios exceeding 10 ³ and channel width‐normalized transconductance of up to 50 µS mm ⁻¹ at 0.8 V, establishing their potential as critical active components in future edible devices. Moreover, the proposed method results in a limited impact of impurities on CuPc charge transport efficiency, thus affecting the purification costs and, crucially, enabling the sourcing of CuPc pigments through recycling and upcycling.