Epitaxial thin films of the iron chalcogenide superconductor FeSe with Tc≃7 K were prepared by Molecular Beam Epitaxy. The films grow in (001)-orientation on YAlO3(110) substrates. The influence of the Fe to Se atomic ratio on the transport properties of the samples is studied. Only within a narrow compositional range superconductivity is observed and films with a residual resistance ratio of up to RRR=R300 K/R8 K≃4 are obtained. The anisotropy of the upper critical field Hc2 is increasing with the RRR and a maximum ratio of Hc2,H∥a/Hc2,H∥c≃3 is observed. From this result, an anisotropy ratio of the coherence lengths of ξab/ξc>3 is estimated.

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authorenWe present a temperature‐ and intensity‐dependent photoluminescence (PL) study of the binary semiconductor Bi2S3 on the mm‐scale and a laterally resolved PL measurement with a resolution of x≈900nm. The films can show a rather rough surface with needles and flakes of Bi2S3 with different orientations as well as very flat and smooth surface morphology. Despite a band gap of Eg≈1.3eV the films show a splitting of quasi‐Fermi levels (QFL) of μ≈700meV at room temperature. By means of temperature‐dependent PL we have located several radiative and non‐radiative defect states in the band gap. For a better understanding of this thin film semiconductor a full analysis of the laterally resolved PL measurement including the integrated PL yield, energetic position of the PL maximum, optical band gap, splitting of quasi‐Fermi levels and defect absorption of both sample morphologies is presented to avoid misinterpretation of experimental data.

The electronic structure of polycrystalline Bi2S3 thin films deposited by thermal evaporation under high vacuum conditions was investigated with respect to their potential use as absorber materials in p-i-n solar cells by means of hard x-ray photoemission spectroscopy at the PETRA III synchrotron. A clear influence of the post-deposition treatment on the electronic structure could be observed, resulting in a lowering of the Fermi level as well as in a change of the electronic states in the valence band. Furthermore, chemical shifts of Bi2S3 were determined in the bulk-sensitive hard x-ray regime as ΔEB,Bi=1.35 eV and ΔEB,S=−2.80 eV.

Sträter et al. (pp. http://doi.wiley.com/10.1002/pssb.201451271) present a detailed photoluminescence (PL) study on the binary semiconductor bismuth sulfide (Bi2S3). Due to its band gap of about 1.3 eV and its non‐toxicity it is regarded as a potential thin film solar cell absorber. The films prepared by physical vapor deposition show a varying surface morphology in terms of roughness and surface structure. By temperature and excitation‐intensity PL experiments Sträter et al. located different defect levels within the band gap. The authors also determined a splitting of quasi‐ Fermi levels (QFL), which can be interpreted as the upper limit of the open circuit voltage, of about 700 meV and an optical band gap of about 1.3 eV at room temperature. By laterally resolved PL measurements they show that a full analysis of the laterally resolved maps is necessary to interpret the lateral variation properly. This includes a detailed analysis of each PL spectrum and the energetic position of its maximum as well as a determination of the QFL splitting, optical band gap, Urbach energy, defect PL yield, and defect absorption to identify properties with opposing effects.