Cost-effective n-type thermocells enabled by thermosensitive crystallizations and 3D multi-structured electrodes

Emerging thermocells have the commercialized potential for directly harvesting low-grade heat. Although a huge progress in p-type thermocells, their n-type counterpart has seriously lagged, becoming a major bottleneck for practical utilization of their integrated devices. Here, we developed a novel Cu-based thermosensitive crystallization and 3D multi-structured electrodes to synergistically boost the thermodynamic and kinetic characteristics of the n-type thermocell. As a result, the optimized Cu/Cu 2+ -based system achieved an exceptionally high value for the Seebeck coefficient (1.66 mV K –1 ) and the power density (3.5 W m –2 ), accompanied with a much competitive cost-performance metric (~$3.28 W –1 ), all of which were superior to the p-type benchmark. Furthermore, a high-performance p-n junction of thermocells was demonstrated with a 14.5 times enhancement of output, paving the way for advancing the integrated devices.