High-Resolution Photolithographic Patterning of Conjugated Polymers via Reversible Molecular Doping

Area of Science:

• Materials Science
• Organic Electronics
• Nanotechnology

Background:

• Organic field-effect transistors (OFETs) require precise patterning of semiconducting layers.
• Conjugated polymers are typically incompatible with photolithography due to solvent-induced dissolution and damage.

Purpose of the Study:

• To develop a photolithography-compatible patterning strategy for conjugated polymers in OFETs.
• To demonstrate the effectiveness of doping-induced solubility conversion (DISC) for high-resolution patterning.

Main Methods:

• Utilized doping-induced solubility conversion (DISC) with AuCl3 to temporarily suppress solubility of poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT).
• Fabricated micropatterns in various geometries with linewidths down to 2 µm using photolithography.
• Evaluated pattern fidelity, resolution, and reproducibility through quantitative analysis.
• Fabricated and tested OFETs based on patterned PBTTT to assess device performance.

Main Results:

• Achieved high-fidelity micropatterning of PBTTT with linewidths as small as 2 µm in diverse geometries.
• Demonstrated excellent resolution and reproducibility across large areas, with low mean absolute errors and coefficients of variation.
• OFETs fabricated using DISC-assisted lithography showed performance comparable to spin-coated devices, preserving charge-carrier mobility and on/off ratios.
• Successfully applied the DISC method to other conjugated polymers like P3HT and PDPP-4T, confirming its broad applicability.

Conclusions:

• DISC provides a scalable and robust strategy for photolithography of conjugated polymers, overcoming previous limitations.
• This method enables precise integration of organic semiconductors into electronic devices.
• The technique is suitable for high-density organic electronic applications, including flexible circuits and biointerfaces.