3D Printing of Solution-Processable 2D Nanoplates and 1D Nanorods for Flexible Thermoelectrics with Ultrahigh Power Factor at Low-Medium Temperatures.

Solution-processable semiconducting 2D nanoplates and 1D nanorods are attractive building blocks for diverse technologies, including thermoelectrics, optoelectronics, and electronics. However, transforming colloidal nanoparticles into high-performance and flexible devices remains a challenge. For example, flexible films prepared by solution-processed semiconducting nanocrystals are typically plagued by poor thermoelectric and electrical transport properties. Here, a highly scalable 3D conformal additive printing approach to directly convert solution-processed 2D nanoplates and 1D nanorods into high-performing flexible devices is reported. The flexible films printed using Sb2Te3 nanoplates and subsequently sintered at 400 °C demonstrate exceptional thermoelectric power factor of 1.5 mW m-1 K-2 over a wide temperature range (350-550 K). By synergistically combining Sb2Te3 2D nanoplates with Te 1D nanorods, the power factor of the flexible film reaches an unprecedented maximum value of 2.2 mW m-1 K-2 at 500 K, which is significantly higher than the best reported values for p-type flexible thermoelectric films. A fully printed flexible generator device exhibits a competitive electrical power density of 7.65 mW cm-2 with a reasonably small temperature difference of 60 K. The versatile printing method for directly transforming nanoscale building blocks into functional devices paves the way for developing not only flexible energy harvesters but also a broad range of flexible/wearable electronics and sensors.