Harnessing Photothermal Synergy of Cs₄CuSb₂Cl₁₂/MoS₂ Composite for Photothermoelectric Energy Harvesting and Small Power Application

Photothermal (PT) and photothermoelectric (PTE) energy conversions are emerging research topics. Innovative material designs integrating energy harvesting and PT conversions are sought to drive these hybrid systems. Here, we report a study of a popular photovoltaic material Cs₄CuSb₂Cl₁₂ (CCSC), which, when combined with bulk MoS₂ into a rational composite, demonstrates exceptional PT/PTE energy conversion upon near-infrared (NIR) illumination for small power applications. Comprehensive structural, composition, and optical characterization of pure CCSC, MoS₂, and their phase-pure mixtures helped us to optimize a composite that demonstrated a synergistic PT conversion. Thermal conductivity (<i>k</i>) modeling of the composite based on CCSC's low (0.32 W m^-1 K^-1) and MoS₂'s superior thermal conductivity (155 W m^-1 K^-1) with measured optical power absorption could explain the PT/PTE behavior. The 75% CCSC composite demonstrated a maximum temperature differential (Δ<i>T</i>) of ∼30 °C, and PTE voltage and current output of 500 mV and 105 mA, respectively, on a TE generator corresponding to a maximum power density of 3.26 mW cm^-2 and efficiency of 7.26 × 10^-3% under a 3000 K lamp at 450 mW cm^-2. The optimized PTE device successfully charged a 40 mAh Li-ion battery within 180 s under 3000 K illumination. For NIR photodetection, the composites showed high responsivity under 808 and 980 nm lasers, with the 75% CCSC sample excelling at 808 nm with ∼9 × 10² V W^-1 and the 100% CCSC sample leading at 980 nm with ∼8.2 × 10² V W^-1.