Photo-Patternable Organic Electrochemical Transistors with Hydrophilic and Hydrophobic Bulk Heterojunction Enabled by Ethylene Glycol-Based Photo-Crosslinker.

Organic electrochemical transistors (OECTs) utilize ion injections to regulate the overall conductivity of the organic semiconductor channel, achieving high transconductance (gm) by coupling ionic and electronic charge carriers within the whole channel's volume. However, the slow ion migration rate through the hydrophobic semiconducting polymer layer restricts the response rate of the device for widespread applications in biomedical sensing. This work introduced poly(ethylene glycol) (PEG) bisazide photo-crosslinking agent into the p-type semiconducting polymers as a hydrophilic active channel in accumulated-mode OECTs. Upon incorporation of PEG segments into conjugated polymers via photolithography, the resulting OECTs exhibit a significant enhancement in both µC* product and doping/de-doping dynamics by at least one order of magnitude. The photo-patterning of an ion-conducting semiconductor channel with a minimum line gap of 5 µm enables the fabrication of a depletion-mode inverter. This study presents a straightforward patterning process that enhances the hydrophilicity of various hydrophobic conjugated polymers while eliminating the need for complex synthesis procedures typically required for introducing ethylene glycol side chains on conjugated polymers.