Thermoelectrics (TEs) are important because they can convert heat directly into electrical energy and enable efficient heating/cooling. As such, they can contribute to mitigating the energy shortage of our society, enable new applications in the fields of wearable electronics, and provide powering solutions for the internet of things. However, the popularization of TEs has been hindered by 1) their low efficiency (especially at room temperature), 2) the use of rare/toxic materials, and 3) the difficulty to process those materials. In 3DALIGN, I target a 3-in-1 solution to these challenges by using for the first time electric-field-assisted molecular alignment of 3D-printed TE polymers. High electrical/low thermal conductivity is required for efficient TEs, but both conductivities go hand in hand in traditional inorganic TE materials. This paradigm can shift for polymers, which possess complicated molecular structures. Despite their relatively low electrical conductivity, conducting polymers are appealing for TEs due to their much lower thermal conductivity than inorganic TE materials. Existing studies of organic TEs have focused on finding new materials, but not much attention has been paid to molecular ordering, a known strategy to improve performance in organic transistors. I have recently developed a versatile method to induce molecular alignment in solution-processed polymers by using externally applied electric fields. In 3DALIGN, I propose to use this new method to boost the electrical conductivity of polymer TEs while inducing minimal alteration in their thermal conductivity. The high risk of this goal is mitigated by other advantages of using polymer TEs: polymers are less toxic and more abundant than inorganic TE materials; and they are easy to 3D print, enabling a simple fabrication route for large-area through-plane TE structures that will lead to novel applications. In conclusion, this project will shed light on the relationship between molecular ordering and transport properties of organic electronic materials. If successful, it will also introduce a breakthrough in the performance and feasibility of TEs.
