Breakthrough molecular brake enables high-performance stretchable semiconductors for next-generation flexible electronics

A revolutionary discovery has been made by a team of researchers led by Professor Kilwon Cho and Ph.D. candidates Seung Hyun Kim and Sein Chung from the Department of Chemical Engineering at POSTECH, along with Professor Boseok Kang from the Department of Nano Engineering at Sungkyunkwan University (SKKU). Their findings, published in the journal Advanced Functional Materials, unveil a remarkable technology for high-performance organic polymer semiconductors that possess both electrical functionality and stretchability.

To enable semiconductors to be used in flexible applications like flexible displays and skin-attachable medical devices, it is crucial to utilize materials that can stretch instead of rigid ones. However, when semiconductors undergo stretching, the force exerted on them can be up to ten times greater than during simple bending. This can cause the breakdown of the semiconductor layers and a decline in their electrical performance. Researchers have been diligently seeking methods to maintain semiconductor performance even under deformation, but a definitive solution has been elusive.

Fortunately, the research team has now developed a breakthrough solution—a flexible molecular photocrosslinker equipped with azide-reactive groups at both ends. When exposed to ultraviolet light, this photocrosslinker forms a network structure with the polymer semiconductor, acting as a brake that prevents slipping even under stretching conditions.

Unlike conventional semiconductor materials, where polymer chains become entangled and slip irreversibly, leading to fracture when stretched, the presence of this “brake” allows the polymer chains to retain their stretchability and performance without any slipping.

Through this innovative approach, the research team achieved remarkable results. They successfully preserved up to 96 percent of the electrical performance of the polymer semiconductor, even when it was stretched to 80 percent. Moreover, the semiconductor exhibited significantly improved stretchability and durability compared to conventional semiconductors, clearly demonstrating the effectiveness of the developed technology.

Professor Kilwon Cho elaborated on the significance of the discovery, stating, “By incorporating azide photocrosslinkers into the films, we have successfully maintained the excellent electrical properties of polymer semiconductors for organic thin-film transistors, even under significant mechanical deformation. This simple approach significantly enhances the stretchability and UV-patternability of organic semiconducting polymers, making it highly valuable for industries requiring large-area production and photolithography for the development of next-generation flexible electronics.”

Source: Pohang University of Science and Technology

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