Narrow-Bandgap Halide Perovskite Cs₄CuSb₂Cl₁₂ with Full-Spectrum Photothermal Conversion

Light-to-heat conversion represents one of the most promising pathways to utilize full-spectrum solar energy. The key for boosting the photothermal conversion in semiconductor-based light absorbers relies on narrowing the bandgap for harvesting wide-range sunlight and localizing thermal energy via decreasing heat loss. Here, we demonstrate the first example of using a halide perovskite, Cs4CuSb2Cl12, as the photothermal material for efficient solar-to-heat conversion, with an intrinsic narrow bandgap and ultralow thermal conductivity. Full-spectrum (200-2500 nm) absorption and solar-thermal conversion efficiency up to 93.4% are achieved. The photothermal property enables a low-temperature and rapid hydrogen production from ammonia borane, with 2.0 equiv of hydrogen released, and a photothermal activation efficiency of 12.2% is realized, without any extra energy input. This high photothermal performance not only provides a potential for an energy-efficient on-board hydrogen supply for fuel cells but also opens up a new field for halide perovskites utilized as photothermal convertors.