Yanfei Xu Receives National Science Foundation Award to Study Thermal-transport Properties in Electrically Conductive Polymers

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Yanfei Xu

Assistant Professor Yanfei Xu of the Mechanical and Industrial Engineering (MIE) Department has been awarded a grant of $452,125 from the National Science Foundation (NSF) through its thermal-transport processes program. As Xu explains, “This project aims to advance our fundamental understanding of thermal-transport properties in electrically conductive polymers, resulting in crucial insights and practical strategies for designing high-performance polymer-based devices. These devices find applications in various fields, such as high-efficiency plastic solar cells, organic field-effect transistors, and organic light-emitting diodes (OLEDs).”

Xu, who is also an adjunct in the Chemical Engineering Department, directs the Advanced Polymer Engineering Laboratory in the MIE department. Her lab is an interdisciplinary research group of mechanical engineers, materials scientists, chemists, and physicists. Their research is dedicated to understanding the heat and charge transport in polymeric materials, as well as uncovering the relationships between polymeric material structures and transport properties across multiscale, from the atomic level to the nanoscale.

As Xu explains about her NSF project, “Electrically conductive polymers have revolutionized modern devices, enabling advancements in plastic solar cells, electronics, and thermoelectric devices. The performance of these devices is linked to how heat is dissipated through conduction or how heat is trapped through insulation.”

In that context, says Xu, “Understanding thermal-transport physics in polymers has been a long-standing challenge. Existing theories and simulations do not quantitatively describe thermal-conductivity enhancement (or reduction) in polymers.”

According to Xu, “The overarching goal of this project is to better understand how charge carriers (polarons and bipolarons) and structural parameters (short-range positional orders, orientational orders, and chain conformations) quantitively affect thermal conductivities along (and across) chain directions, which are the missing pieces in providing a complete microscopic picture of heat conduction in electrically conductive polymers.”

Accordingly, Xu’s project will study temperature-dependent thermal conductivities, heat capacities, electrical conductivities, and Seebeck coefficients by employing several state-of-the-art techniques.

“This project will not only create insights into thermal-transport processes in electrically conductive polymers,” says Xu, “but also provide transformative opportunities to develop novel electronic devices based on the interaction of microscopic energy carriers.”

Xu emphasizes that fundamental experimental studies on thermal transport in electrically conductive polymers open up possibilities for designing multifunctional polymers with precise control over both thermal- and electrical-transport capabilities. If successful, this project has the potential to facilitate the development of advanced functional polymers that can effectively manage thermal conditions in devices, leading to the emergence of innovative technologies and applications, such as OLEDs without overheating.

Xu concludes that “We have chosen a simple model conjugated polymer (a polymer chain with alternating single and double bonds) called polythiophene for our proposed research. Our aim is to advance the fundamental understanding of how different structures and charge carriers influence the thermal-transport properties of conjugated polymers. This knowledge will guide the design of new conjugated polymers with improved thermal-transport properties for various applications.”

Xu adds that “Our education plan will prioritize diversity and inclusion in the engineering workforce, with a specific aim to engage and support women and individuals from underrepresented racial and ethnic groups, ultimately contributing to the development of a more diverse and globally competitive STEM workforce.” (July 2023)