Revealing the Influence of Electrolyte Solvents and Ions on Electronic and Ionic Transport in Electrochemically Doped Conjugated Polymers

Project Summary Overview Conjugated polymers (CPs) show mixed ionic and electronic conduction, which makes them attractive for use in numerous applications. For example, CPs are currently being investigated for use in biosensing, bioelectronics, batteries, electrocatalytic applications, photoelectrochemical cells, electrochromic devices, neuromorphic computing, and memory storage applications. The material demands of all these applications differ, yet all rely on mixed ionic and electronic conduction for their operation. To accelerate the development of these and future applications, it is imperative to understand the fundamental chemistry governing ionic and electronic transport. Such an understanding demands that the complicated interplay between CP structure, electrolyte solvent, and electrolyte solvents is accounted for. This work will focus on developing a systems level understanding of ionic and electronic transport in CPs that accounts for the interconnections between electrolyte solvent, electrolyte ions, and CP structure. The three principal investigators (PI) will combine spectroscopic measurements, thermodynamic measurements, and device level measurements with density functional theory and molecular dynamics calculations to develop a fundamental understanding that spans from molecular level chemical interactions to device level ionic and electronic transport properties. The three PI team will combine their expertise to host an in-person workshop for high school chemistry and physics teachers, which will be complemented by short plug-and-play learning modules that the teachers can use to supplement their STEM classes. This workshop and module development is designed to promote STEM interest throughout Kentucky, including in regions of the state with less opportunities and a large concentration of underrepresented minorities in STEM. Intellectual Merit In CPs the ionic and electronic conduction is determined by the interplay between CP structure, CP morphology, electrolyte solvent, and electrolyte ions; thereby, a systems level approach that accounts for the connections between these variables is paramount to understanding the transport properties. This project will establish fundamental knowledge regarding the interplay between these variables, with a specific focus on how solvent-CP and ion-CP interactions combine to influence both ionic and electronic transport. A multipronged approach will be adopted to gain this knowledge, combining a suite of spectroscopic measurements, device level measurements, and theoretical calculations. Measurements of thermodynamic parameters will be conducted and compared with theoretical calculations to both enhance understanding of material behavior and refine the calculations. The results of this project will ultimately lay the groundwork for a comprehensive predictive model that can be used to guide materials design and electrolyte selection for various applications. Broader Impacts The educational outreach goal of this project is to promote STEM education across the Commonwealth of Kentucky through providing middle and high school teachers with hands-on experience and easily integrated learning modules. Throughout the project a total of 27 middle and high school teachers will participate in a hands-on workshop at the University of Kentucky where they will learn about and make organic light emitting diodes, polymer electrochromics, thermoelectrics, transistors, and basic Python programming and computational chemistry approaches. The teachers will leave the workshop with materials necessary to have their classes make working electrochromic devices, materials to build a basic amplification circuit using a transistor, a thermoelectric device, learning modules to accompany these materials and experiments, and a module to integrate into their classroom to build basic programming knowledge and access to quantum-chemical calculations. In addition, we will prepare several short plug- and-play learning modules that busy teachers can quickly integrate into their lesson plans. These learning modules will be designed to enhance STEM education through connecting fundamental concepts of chemistry and physics with the everyday lives of the students. The project will provide training to at least three graduate students and undergraduate students, thereby helping to strengthen the STEM workforce. The scientific results will accelerate the development of mixed ionic and electronic conductors and the applications (from batteries to biosensors) in which they may be used.