Thermoelectric Generator Based on Kesterite (Cu₂ZnSnS₄) Synthesized via Sol-Gel Method

The need for sustainable and cost-effective thermoelectric materials has brought attention to earth-abundant and mineral compounds, like Cu₂ZnSnS₄ (CZTS). In this work, CZTS nanoparticles (NPs) were synthesized via the sol-gel method using environmentally friendly solvents based on water and ethanol mixtures. The resulting CZTS NPs were then processed into inks through ball milling to produce a thin-film thermoelectric generator (TEG). Structural and microstructural properties were investigated via X-ray diffraction and Raman spectroscopy, confirming the kesterite CZTS phase upon sintering. The chalcogenide exhibited p-type semiconductor behaviour, with a Seebeck coefficient reaching ~69 µV/K at 385 K. Van-der-Pauw measurements of conductivity confirmed a non-degenerate semiconducting behaviour, achieving ~1.77 S/cm at 323 K. A two-leg CZTS thin-film TEG reaching a maximum power output of 32(3) nW at a ΔT ~160 K was used, measured with a home-made setup. The volume-specific power of the generator reached 4×10-4 μW cm^-3 K^-2. These results point to an effective use of sol-gel-based techniques to produce a functional thermoelectric generator, providing a costless and environmentally friendly approach to CZTS NPs.