Abstract

Direct photopatterning with photoactivated cross-linkers provides a powerful route to highly integrated, solution-processed electronics. We introduce Diazo-6Bx, a six-branched diazo-based cross-linker that combines high miscibility with organic semiconductors and efficient C–H insertion reactivity. Comparative studies with azide-functionalized cross-linkers (phenyl- and tetrafluorophenyl-based structural analogues, namely, Ph-6Bx and 6Bx, respectively) reveal that the fluorine-free structure of Diazo-6Bx and its superior compatibility with host materials enable highly uniform cross-linking. This results in high-fidelity photopatterning with steep taper angles, excellent pattern retention, and minimal line-width variation. In solution-processed organic thin-film transistors (OTFTs), Diazo-6Bx enables the fabrication of unit devices that outperform those based on 6Bx, as well as large-area, high-resolution transistor arrays and logic circuits with excellent operational stability and scalability. These results demonstrate that a careful cross-linker design will play a crucial role in patterning next-generation electronic materials in extremely high fidelity.

Printing electronic circuits from solution offers a promising route to lightweight, flexible electronics, but producing fine circuit patterns without sacrificing device performance remains a persistent manufacturing challenge. Professor BongSoo Kim and his research team in the Department of Chemistry at UNIST, working with collaborators at Yonsei University, have developed a new photo-crosslinker that enables more precise patterning of organic semiconductor circuits while improving the stability of the resulting devices.

The material, Diazo-6Bx, was designed to blend more uniformly with hydrocarbon-based organic semiconductors than existing photo-crosslinkers. During ultraviolet patterning, it forms cross-linked networks that preserve circuit geometry, producing cleaner edges and more consistent feature sizes.

In photopatterning experiments, Diazo-6Bx reduced line-width variation from 10.3 μm to 2.5 μm—roughly one quarter that of a widely used conventional photo-crosslinker. Circuit edges also became significantly sharper, with taper angles increasing from 67.9° to 87°, approaching nearly vertical sidewalls.

The improved material compatibility also reduced charge-trapping defects, resulting in more stable transistor performance during prolonged operation. Organic thin-film transistors fabricated using Diazo-6Bx maintained more stable electrical characteristics under prolonged operation than devices produced with conventional crosslinking materials.

The researchers also demonstrated that both p-type and n-type organic semiconductors could be patterned sequentially using the same solvent process. Using the same process, the researchers fabricated an 84-transistor organic thin-film transistor (OTFT) array together with complementary NOT, NAND, and NOR logic gates, demonstrating the scalability of the approach for complex organic electronic circuits.

“This photo-crosslinker improves both patterning precision and device stability,” said Professor BongSoo Kim of the Department of Chemistry at UNIST. "Its compatibility with both p-type and n-type organic semiconductors simplifies solution processing and could help simplify manufacturing of large-area flexible displays and wearable electronic devices."

The study was conducted in collaboration with Professor Jeong Ho Cho of Yonsei University. The findings were published in ACS Nano on June 23, 2026. The research was supported by the Samsung Future Technology Incubation Program and the National Research Foundation of Korea (NRF) through funding from the Ministry of Science and ICT (MSIT).

Journal Reference

Hyobin Ham, In Cheol Kwak, Daeyeon Lee,  et al. , “Diazo-6Bx, a Six-Branched Diazo Cross-Linker, Enables High-Fidelity Patterning for Solution-Processed Electronics with Stable Operation,”  ACS Nano, (2026).