Photonic Curing Enables Ultrarapid Processing of Highly Conducting β‑Cu_2−δSe Printed Thermoelectric Films in Less Than 10 ms

It has been a challenge to obtain high electrical conductivity in inorganic printed thermoelectric (TE) films due to their high interfacial resistance. In this work, we report a facile synthesis process of Cu–Se-based printable ink for screen printing. A highly conducting TE β-Cu_2−δSe phase forms in the screen-printed Cu–Se-based film through ≤10 ms sintering using photonic-curing technology, minimizing the interfacial resistance. This enables overcoming the major challenges associated with printed thermoelectrics: (a) to obtain the desired phase, (b) to attain high electrical conductivity, and (c) to obtain flexibility. Furthermore, the photonic-curing process reduces the synthesis time of the TE β-Cu_2−δSe film from several days to a few milliseconds. The sintered film exhibits a remarkably high electrical conductivity of ∼3710 S cm^–1 with a TE power factor of ∼100 μW m^–1 K^–2. The fast processing and high conductivity of the film could also be potentially useful for different printed electronics applications.