Zinc Stabilized Cation Ordered Chalcopyrite Thin Film for Enhanced Thermoelectric Power Generation Near Room Temperature

Multinary sulfides represent a significant family of semiconductors because of their low cost and promising performance, yet controlling their composition is challenging. CuFeS 2 thin films are particularly attractive because of their great potential in thermoelectricity and photovoltaics. Herein we reveal the newest finding that Zn promotes the cation ordering and stabilizes the chalcopyrite CuFeS 2 film, preventing the reverse transformation to wurtzite with a random distribution of Cu–Fe at high temperature. The thermoelectric properties of chalcopyrite thin films are investigated as a function of Zn content, resulting in an optimized power factor of 0.168 mW/m·K 2 at room temperature, outperforming any CuFeS 2 thin films ever reported. For the first time, synchrotron-based in situ X-ray diffraction and X-ray absorption fine structure confirm the phase transition, offering insights into the isomeric structure of CuFeS 2 and the role of Zn. The in-depth understanding of cation-ordering and phase transformation between CuFeS 2 polymorphs might impact the multinary sulfide film fabrication and improvement in efficiency of renewable energy applications.