Water-resistant organic thermoelectric generator with >10 mu W output

Flexible p-n thermoelectric generator (TEG) technology has rapidly advanced with power enhancement and size reduction. To achieve a stable power supply and highly efficient energy conversion, absolute chemical stability of n-type materials is essential to ensuring large temperature differences between device terminals and ambient stability. With the aim of improving the long-term stability of the n-type operation of carbon nanotubes (CNTs) in air and water, this study uses cationic surfactants, such as octylene-1,8-bis(dimethyldodecylammonium bromide) (12-8-12), a gemini surfactant, to stabilize the nanotubes in a coating, which retains the n-doped state for more than 28 days after exposure to air and water in experiments. TEGs with 10 p-n units of 12-8-12/CNT (n-type) and sodium dodecylbenzene sulfonate/CNT (p-type) layers are manufactured, and their water stability is evaluated. The initial maximum output of 16.1 mu W (75 K temperature difference) is retained after water immersion for 40 days without using a sealant to prevent TEG module degradation. The excellent stability of these CNT-based TEGs makes them suitable for underwater applications, such as battery-free health monitoring and information gathering systems, and facilitates the development of soft electronics.