An integrated computational and experimental study of FeS2 pyrite reveals that phase coexistence is an important factor limiting performance as a thin‐film solar absorber. This phase coexistence is suppressed with the ternary materials Fe2SiS4 and Fe2GeS4, which also exhibit higher band gaps than FeS2. Thus, the ternaries provide a new entry point for development of thin‐film absorbers and high‐efficiency photovoltaics.

We describe here a general synthesis approach for the preparation of new families of misfit layer compounds and demonstrate its effectiveness through the preparation of the first 64 members of the [(PbSe)0.99] m (WSe2) n family of compounds, where m and n are integers that were systematically varied from 1 to 8. The new compounds [(PbSe)1+y ] m (WSe2) n were synthesized by annealing reactant precursors containing m layers of alternating elemental Pb and Se followed by n layers of alternating elemental W and Se, in which the thickness of each pair of elemental layers was calibrated to yield a structural bilayer of rock salt structured PbSe and a trilayer of hexagonal WSe2. The compounds are kinetically trapped by the similarity of the composition profiles and modulation lengths in the precursor and the targeted compounds. The structural evolution from initial reactant of layer elements to crystalline misfit layer compounds was tracked using X-ray diffraction. The crystal structures of new compounds were probed using both analytical electron microscopy and X-ray diffraction. The c-axis of the misfit layer compound is perpendicular to the substrate, with a c-axis lattice parameter that changes linearly with a slope of 0.612−0.615 nm as m is changed and n is held constant and with a slope of 0.654−0.656 nm as n is varied and m is held constant. The in-plane lattice parameters did not change as the individual layer thicknesses were increased and a misfit parameter of y = −0.01 was calculated, the first negative misfit parameter among known misfit layer compounds. Analytical electron microscopy images and X-ray diffraction data collected on mixed hkl reflections revealed rotational (turbostratic) disorder of the a−b planes.

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We theoretically investigate the electronic and optical properties of semiconductor Cu3PSe4. We also report diffuse reflectance spectroscopy measurements for Cu3PSe4 and Cu3PS4, which indicate a band gap of 1.40 eV for the former.Hybrid functional calculations agree well with this value, and reveal that the band gap is direct. Calculations yield an optical absorption spectrum similar to GaAs in the visible region, with {\alpha} > 5x10^4 cm^-1 for {\lambda} < 630 nm. We conclude that the optical properties of Cu3PSe4 are within the desired range for a photovoltaic solar absorber material.Comment: 3 pages, 3 figure

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Double excitonic absorption peaks are observed in textured BaCuSF and BaCuSeF thin films. The excitonic doublet separation increases with increasing fraction of heavy chalcogen in the thin-film solid solutions, in good agreement with the spin-orbit splitting of the valence bands calculated by density-functional theory. In BaCuSF and BaCuSeF, the excitons have large binding energies ͑95 and 65 meV, respectively͒ and can be observed at room temperature. A three-dimensional Wannier-Mott excitonic absorption model gives good agreement between the experimental and theoretical optical properties. Band gaps of BaCuSF and BaCuSeF calculated using the GW approximation agree with experiment. In BaCuTeF, transitions across the lowest direct energy gap and excitonic absorption are suppressed, extending its transparent range.