A Sustainable Brand-New Thermoelectric Cooling Material: High-Mobility Diamondoid Cu₃SbSe₄ Crystal

Diamondoid Cu₃SbSe₄ is an earth-abundant thermoelectric material with strong potential for near-room to mid-temperature applications. However, its performance has been limited by intrinsically low carrier mobility. Here, we report the first successful growth of large-sized Cu₃SbSe₄ crystals, achieving a fivefold enhancement in carrier mobility, and demonstrate the first Cu₃SbSe₄-based thermoelectric cooling device. We show that Ag substitution reduces both the effective mass and deformation potential through strengthened bond covalency, yielding a high carrier mobility of ∼150 cm² V^-1 s^-1. This leads to a remarkable power factor of ∼23 µW cm^-1 K^-2 at 300 K, a maximum ZT of ∼1.6 at 700 K and an average ZT of ∼0.85 over 300-700 K, representing state-of-the-art performance among Cu-based thermoelectric materials in this temperature range. A 7-pair device based on Cu₃SbSe₄ crystal achieves a cooling temperature difference of ∼25 K at room temperature, and reaching a maximum of ∼34 K at 343 K. Additionally, the optimized sample demonstrates a single-leg power-generation efficiency of ∼7% at ΔT = 350 K. These results highlight crystal-growth as a powerful strategy to unlock high-performance refrigeration in previously limited materials, establishing diamondoid Cu₃SbSe₄ crystals as a viable, low-cost and environmentally benign platform for practical thermoelectric applications.