Energy-harvesting from low-temperature environmental heat via thermoelectric generators (TEG) is a versatile and maintenance-free solution for large-scale waste heat recovery and supplying renewable energy to a growing number of devices in the Internet of Things (IoT) that require an independent wireless power supply. A prerequisite for market competitiveness, however, is the cost-effective and scalable manufacturing of these TEGs. Our approach is to print the devices using printable thermoelectric polymers and composite materials. We present a mass-producible potentially low-cost fully screen printed flexible origami TEG. Through a unique two-step folding technique, we produce a mechanically stable 3D cuboidal device from a 2D layout printed on a thin flexible substrate using thermoelectric inks based on PEDOT nanowires and a TiS2:Hexylamine-complex material. We realize a device architecture with a high thermocouple density of 190 per cm² by using the thin substrate as electrical insulation between the thermoelectric elements resulting in a high-power output of 47.8 µWcm−² from a 30 K temperature difference. The device properties are adjustable via the print layout, specifically, the thermal impedance of the TEGs can be tuned over several orders of magnitudes allowing thermal impedance matching to any given heat source. We demonstrate a wireless energy-harvesting application by powering an autonomous weather sensor comprising a Bluetooth module and a power management system.

Printed thermoelectrics (TE) could significantly reduce the production cost of energy harvesting devices by large-scale manufacturing. However, developing a high-performance printable TE material is a substantial challenge. In this work,...

The thermoelectric performance of thin films fabricated from two commercially available, highly conductive polymer formulations based on poly (3,4-ethylendioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) was investigated. In order to enhance the electrical conductivity, the high-boiling solvent dimethyl sulfoxide (DMSO) was added. By changing the content of DMSO the electrical conductivity was increased by a factor of two without changing the Seebeck coefficient or the thermal conductivity. We achieved ZT = 9.2 9 10 À3 at room temperature upon the addition of 5 vol.% DMSO to the PEDOT:PSS formulation.

High-performance Ag−Se-based n-type printed thermoelectric (TE) materials suitable for room-temperature applications have been developed through a new and facile synthesis approach. A high magnitude of the Seebeck coefficient up to 220 μV K −1 and a TE power factor larger than 500 μW m −1 K −2 for an n-type printed film are achieved. A high figure-of-merit ZT ∼0.6 for a printed material has been found in the film with a low in-plane thermal conductivity κ F of ∼0.30 W m −1 K −1 . Using this material for n-type legs, a flexible folded TE generator (flexTEG) of 13 thermocouples has been fabricated. The open-circuit voltage of the flexTEG for temperature differences of ΔT = 30 and 110 K is found to be 71.1 and 181.4 mV, respectively. Consequently, very high maximum output power densities p max of 6.6 and 321 μW cm −2 are estimated for the temperature difference of ΔT = 30 K and ΔT = 110 K, respectively. The flexTEG has been demonstrated by wearing it on the lower wrist, which resulted in an output voltage of ∼72.2 mV for ΔT ≈ 30 K. Our results pave the way for widespread use in wearable devices.