Colloidal Synthesis of Quaternary Wurtzite Cu3 AlSnS5 Nanocrystals and Their Photoresponsive Properties

Nanobulk Thermoelectric Materials Fabricated from Chemically Synthesized Cu3Zn1-x Al x SnS5-y Nanocrystals

Direct energy conversion of heat into electricity using thermoelectric materials is an attractive solution to help address global energy issues. Developing novel materials composed of earth-abundant and nontoxic elements will aid progress toward the goal of sustainable thermoelectric materials. In this study, we chemically synthesized Cu-Zn-Sn-S nanocrystals and fabricated a Cu3ZnSnS5-y thermoelectric material using nanocrystals as building blocks. The figure-of-merit (ZT) value of the Cu3ZnSnS5-y material was found to be 0.39 at 658 K. We substituted Zn with Al in the Cu3ZnSnS5-y system to form Cu3Zn1-x Al x SnS5-y (x = 0.25, 0.5, 0.75, and 1) to lower the lattice thermal conductivity of the resulting materials. Complete substitution of Al for Zn substantially decreased the lattice thermal conductivity and dramatically increased the electrical conductivity of the material. However, the ZT value could not be significantly enhanced, which could be primarily attributed to the high carrier thermal conductivity. These results highlight the production of Cu3Zn1-x Al x SnS5-y thermoelectric materials and unveil the scope for improvement of ZT values by altering transport properties.

Application of Cu3InSnSe5 Heteronanostructures as Counter Electrodes for Dye-Sensitized Solar Cells

In this research, we reported the synthesis of quaternary Cu₃InSnSe₅ nanoparticles with uniform size distribution and morphology for the first time through delicate controls over the chemical reaction kinetics. On the basis of the preparation strategy of Cu₃InSnSe₅ nanoparticles, Pt-Cu₃InSnSe₅ and Au-Cu₃InSnSe₅ heteronanostructures were designed and yielded using a simple and efficient seed growth method. These two heteronanostructures remained monodispersed without presence of any Cu₃InSnSe₅ nanocrystal impurities. To explore their application potentials for dye-sensitized solar cells, counter electrodes consisting of individual Cu₃InSnSe₅, Pt-Cu₃InSnSe₅, or Au-Cu₃InSnSe₅ constituents were fabricated. Current density-voltage (J-V) characteristics evaluation reveals that Cu₃InSnSe₅ nanoparticles, Pt-Cu₃InSnSe₅ and Au-Cu₃InSnSe₅ heterostructured nanoparticles display a comparative power conversion efficiency (PCE) of 5.8%, 7.6%, and 6.5% to that of a Pt-based counter electrode (7.9%), respectively. As such, we believe that the reported preparation strategy could provide new insights to the design and manufacture of counter electrode materials with controlled structure, morphology, and optimized power conversion efficiency for dye-sensitized solar cells.