Milliwatt-scale 3D thermoelectric generators via additive screen printing†

Electronic components driving digitalization, such as wearables, Internet of Things (IoT), and Industry 4.0 systems, consume a growing portion of the global primary energy, largely relying on lithium-ion batteries. To enable a sustainable alternative, we explore cost-effective, fully printed thermoelectric generators (TEGs), which can be an alternative to batteries in low-power electronics. We here report a promising additive screen-printing method to fabricate two printed 3D TEGs (print-TEG I and print-TEG II) with varying thermocouple counts and a 0.36 fill factor, overcoming high contact resistance and thickness limitations. The print-TEGs were prepared via layer-by-layer printing of electrodes, interlayers, and n- and p-type legs, with six different layouts. Printed Ag₂Se as n-type legs and Bi_0.5Sb_1.5Te₃ as p-type legs were used for TEG fabrication. The print-TEG II with 50 thermocouples generates a maximum power output P_max of 1.22 mW with an open circuit voltage, V_OC of 268 mV for ΔT = 43 K. The print-TEG shows a highest power density P_d of 67 μW cm⁻² (>400 μW g⁻¹) for a fully printed planar TEG. The results demonstrate the potential of print-TEGs as a steadfast power source, guaranteeing nonstop operation of low-power electronic devices.