Researchers have made a breakthrough in designing electrically and thermally conductive polymers for generating energy from waste heat. A team at the University of Massachusetts Amherst have made a breakthrough in research to generate energy from waste heat using a common material that isn’t usually electrically conductive—polymer. Chemist Dhandapani Venkataraman and electrical engineer Zlatan Aksamija have discovered a key variable to making polymer materials conductive—by observing a new characteristic during doping, a process that adds molecules or removes or adds electrons to the polymers to make them conductive.
“As we increase the doping, we can increase its conductivity but decrease the thermally-induced voltage,” Venkataraman explained to Design News about the discovery. “If we decrease the doping, we decrease the conductivity but increase the thermally-induced voltage. We need to balance both.”
What researchers specifically discovered is that dopants can clump, or cluster--or not, he told us. This is key to achieving the right balance for conductivity. “We found that this clustering is an important new variable that we can tune to achieve the balance,” Venkataraman told Design News. Aksamija already had led previous research to create polymer-based materials to store solar energy in chemicals bonds and release them as heat on-demand, Venkataraman told us. So there was a precedent for the current work, he said. “The natural next step is for us to convert this heat to electricity,” Venkataraman told Design News. “Therefore, we started looking into polymer-based thermoelectric materials. We are also intrigued by some experimental results we got in our lab. So we joined hands to look into this problem of converting waste heat into energy.”
Doping typically involves a trade-off, researchers said. It can either achieve more current and less thermally induced voltage, or more voltage and less current; however, it can’t achieve both. Usually, if researchers improve one property, the other becomes worse, making it difficult to achieve the balance in materials, researchers said. To achieve their goal with this research, the team conducted experiments and efficiency analyses that ranged from zero doping to maximum doping to come up with the best electrically conductive balance for their polymers. Researchers published a paper on their work in the journal Nature Communications. Venkataraman said that the result will likely be a surprise for other scientists in the field, and a significant one, as polymers are useful materials to investigate for generating energy from waste heat for a couple of reasons.