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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]

Polycrystalline samples of Sr2VFeAsO3-δ with perovskite-type carrier blocking layers were prepared by a solid state reaction using an alumina tube in a sealed silica tube. Sr2VFeAsO3-δ samples which were prepared as nominally δ = 0 were not synthesized as a single phase, suggesting that finite oxygen deficiency is inevitable for the compound. Although a sample, which exhibits relatively larger lattice volume, does not exhibit bulk superconductivity at temperatures ≥5 K, finite superconducting transition temperatures appear in the sample which exhibits smaller lattice volumes. These results support making the electronic and magnetic phase diagram of Sr2VFeAsO3-δ. [ABSTRACT FROM AUTHOR]