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Kesterite semiconductors, particularly Cu2ZnSnS4 (CZTS), have attracted attention for thin-film solar cells. We investigate the incorporation of Fe into CZTS to form the Cu2(Zn,Fe)SnS4 solid-solution for tuning the lattice spacing and band gap. First-principles calculations confirm a phase transition from kesterite (Zn-rich) to stannite (Fe-rich) at Fe/Zn∼0:4. The exothermic enthalpy of mixing is consistent with the high solubility of Fe in the lattice. There is a linear band-gap bowing for each phase, which results in a blue-shift of photo-absorption for Fe-rich alloys due to the confinement of the conduction states. We propose compositions optimal for Si tandem cells. [ABSTRACT FROM AUTHOR]

The thermoelectric properties and electronic band structures for Se-doped Co 3 SnInS 2 were examined. The parent compound of this material (Co 3 Sn 2 S 2 ) has two kinds of Sn sites (Sn1 and Sn2 sites). The density functional theory (DFT) calculations show that the indium substitution at the Sn2 site induces a metallic band structure, on the other hand, a semiconducting band structure is obtained from substitution at the Sn1 site. However, according to the previous reports, since the indium atom prefers to replace the tin atom at the Sn1 site rather than the Sn2 site, the resistivity of Co 3 SnInS 2 shows semiconducting-like behavior. In this study we have demonstrated that metallic behavior and a decrease in resistivity for Se-doped Co 3 SnInS 2 occurs without suppression of the Seebeck coefficient. From the DFT calculations, when the selenium content is above 0.5, the total crystallographic energy shows that a higher indium occupancy at Sn2 site is more stable. Therefore, it is suggested that the selenium doping suppress the site preference for indium substitution. This is one of the possible explanations for the metallic conductivity observed in Se-doped Co 3 SnInS 2 [ABSTRACT FROM AUTHOR]

A series of polycrystalline samples of Cu2+xFe1-xSnS4-y (x = 0-1, y ≤ 0.4) are prepared by solid state reaction of stoichiometric mixtures of the elements (evacuated silica tubes, 750 °C, 96 h). [ABSTRACT FROM AUTHOR]