Enhancing zT in Organic Thermoelectric Materials through Nanoscale Local Control Crystallization

Organic thermoelectric materials are promising for wearable heating and cooling devices, as well as near-room-temperature energy generation, due to their nontoxicity, abundance, low cost, and flexibility. However, their primary challenge preventing widespread use is their reduced figure of merit (zT) caused by low electrical conductivity. This study presents a method to enhance the thermoelectric performance of solution-processable organic materials through confined crystallization using the lithographically controlled wetting (LCW) technique. Using PEDOT as a benchmark, we demonstrate that controlled crystallization at the nanoscale improves electrical conductivity by optimizing chain packing and grain morphology. Structural characterizations reveal the formation of a highly compact PEDOT arrangement, achieved through a combination of confined crystallization and DMSO post-treatment, leading to a 4-fold increase in the power factor compared to spin-coated films. This approach also reduces the thermal conductivity dependence on electrical conductivity, improving the zT by up to 260%. The LCW technique, compatible with large-area and flexible substrates, offers a simple, green, and low-cost method to boost the performance of organic thermoelectrics, advancing the potential for sustainable energy solutions and advanced organic electronic devices.