Near-Unity Photothermal Conversion in Bimetallic M44 and M81 Nanoclusters Enables NIR-Driven Photo-Thermo-Electricity Generation.

More than half of the solar energy lies in the near-infrared (NIR) range; however, utilizing a significant amount of energy in this region remains largely inaccessible in conventional photovoltaic technologies. Here, we establish quantum-sized nanoclusters (NCs) as a new class of NIR-driven photo-thermo-electric transducers via light-to-heat-to-electricity cascade conversion. Two alkynyl-protected alloy NCs, namely, Au24Ag20 (M44) and Au43Ag38 (M81), exhibit NIR-II photoluminescence, being rare among the NCs. More strikingly, the NC solutions deliver record photothermal conversion efficiencies of 69% and 91% with M44 and M81, respectively, which are the highest reported for atomically precise nanomaterials to date, together with their exceptional solid-state temperature rise of more than 200°C under 808 nm irradiation for thermoelectric generation (TEG) while maintaining photostability. The nanocluster absorption profiles overlap well with the solar spectrum, suggesting the potential of such NCs in converting sunlight to thermoelectricity. The current work will drive the future design of next-generation NC-based devices that are capable of harvesting the NIR solar spectrum for light-to-heat-to-electricity conversion and other photonic energy harvesting technologies.