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Environmental cells sealed with photoelectron‐transparent graphene windows are promising for extending X‐ray photoelectron spectroscopy (XPS) to liquid and high‐pressure gas environments for in situ and operando studies. However, the reliable production of graphene windows that are sufficiently leak‐tight for extended measurements remains a challenge. Here we demonstrate a PDMS/Au(100 nm)‐supported transfer method that reliably produces suspended graphene on perforated silicon nitride membranes without significant contamination. A yield of ~95 % is achieved based on single‐layer graphene covering >98 % of the holes in the silicon nitride membrane. Even higher coverages are achieved for stacked bilayer graphene, allowing wet etching (aqueous KI/I2) of the Au support to be observed in a conventional lab‐based XPS system, thereby demonstrating the in situ formation of leak‐tight, suspended graphene windows. Furthermore, these windows allow gas‐phase measurements at close to atmospheric pressure, showing future promise for XPS under higher‐pressure gas environments in conventional lab‐based systems. [ABSTRACT FROM AUTHOR]

Antimony selenide (Sb 2 Se 3) possesses great potential in the field of photovoltaics (PV) due to its suitable properties for use as a solar absorber and good prospects for scalability. Previous studies have reported the growth of a native antimony oxide (Sb 2 O 3) layer at the surface of Sb 2 Se 3 thin films during deposition and exposure to air, which can affect the contact between Sb 2 Se 3 and subsequent layers. In this study, photoemission techniques were utilized on both Sb 2 Se 3 bulk crystals and thin films to investigate the band alignment between Sb 2 Se 3 and the Sb 2 O 3 layer. By subtracting the valence band spectrum of an in situ cleaved Sb 2 Se 3 bulk crystal from that of the atmospherically contaminated bulk crystal, a valence band offset (VBO) of − 1.72 eV is measured between Sb 2 Se 3 and Sb 2 O 3. This result is supported by a − 1.90 eV VBO measured between Sb 2 O 3 and Sb 2 Se 3 thin films via the Kraut method. Both results indicate a straddling alignment that would oppose carrier extraction through the back contact of superstrate PV devices. This work yields greater insight into the band alignment of Sb 2 O 3 at the surface of Sb 2 Se 3 films, which is crucial for improving the performance of these PV devices. [ABSTRACT FROM AUTHOR]

Despite the recent success of CdS/Sb2Se3 heterojunction devices, cadmium toxicity, parasitic absorption from the relatively narrow CdS band gap (2.4 eV) and multiple reports of inter‐diffusion at the interface forming Cd(S,Se) and Sb2(S,Se)3 phases, present significant limitations to this device architecture. Among the options for alternative partner layers in antimony chalcogenide solar cells, the wide band gap, non‐toxic titanium dioxide (TiO2) has demonstrated the most promise. It is generally accepted that the anatase phase of the polymorphic TiO2 is preferred, although there is currently an absence of analysis with regard to phase influence on device performance. This work reports approaches to distinguish between TiO2 phases using both surface and bulk characterization methods. A device fabricated with a radio frequency (RF) magnetron sputtered rutile‐TiO2 window layer (FTO/TiO2/Sb2Se3/P3HT/Au) achieved an efficiency of 6.88% and near‐record short–circuit current density (Jsc) of 32.44 mA cm−2, which is comparable to established solution based TiO2 fabrication methods that produced a highly anatase‐TiO2 partner layer and a 6.91% efficiency device. The sputtered method introduces reproducibility challenges via the enhancement of interfacial charge barriers in multi‐phase TiO2 films with a rutile surface and anatase bulk. This is shown to introduce severe S‐shaped current–voltage (J–V) distortion and a drastic fill–factor (FF reduction in these devices. [ABSTRACT FROM AUTHOR]

Germanium sulfide and germanium selenide bulk crystals were prepared using a melt growth technique. X-ray photoemission spectroscopy (XPS) was used to determine ionisation potentials of 5.74 and 5.48 eV for GeS and GeSe respectively. These values were used with the previously-measured band gaps to establish the natural band alignments with potential window layers for solar cells and to identify CdS and TiO2 as sensible choices. The ionisation potential of GeS is found to be smaller than in comparable materials. Using XPS and hard X-ray photoemission (HAXPES) measurements in conjunction with density-functional theory calculations, we demonstrate that stereochemically active Ge 4s lone pairs are present at the valence-band maxima. Our work thus provides direct evidence for active lone pairs in GeS and GeSe, with important implications for the applications of these and related materials such as Ge-based perovskites. [ABSTRACT FROM AUTHOR]

Multiple anion materials are of particular interest for the discovery of new crystal structures and offer an original way to modulate physical properties, including energy storage materials with enhanced performances. Through careful synthesis optimization, a new Na2Fe2OS2 phase was prepared by two different routes: high temperature solid-state synthesis and simple mechanochemical synthesis. The long-range and local structure of Na2Fe2OS2 was studied by Rietveld refinement of neutron and X-ray diffraction data combined with EXAFS data refinement. The phase comprises an amorphous and a crystalline part which has an anti-K2NiF4 structure, corresponding to the n = 1 member of the homologous anti-Ruddlesden–Popper [AX][ABX3]n series. Its electrochemical properties as a cathode material were studied in Na half cells and Na-ion full cells, revealing that the material becomes fully amorphous upon initial desodiation to Na0.5Fe2OS2, but maintains a reversible capacity of 135 mA h g−1 in full cells where up to 1.2 Na+ can be reversibly extracted and reinserted when compensating for the Na lost in SEI formation. The stability of the pristine material and its structural evolution upon charging are discussed, paving the way for further optimization of this material. Being composed exclusively of earth-abundant elements and stable under dry air, Na2Fe2OS2 perfectly illustrates the great opportunity of multiple anion chemistry to explore new structure types and develop better energy storage systems. [ABSTRACT FROM AUTHOR]

The presence of a lone pair of 5s electrons at the valence band maximum (VBM) of Sb2Se3 and the resulting band alignments are investigated using soft and hard X-ray photoemission spectroscopy in parallel with density functional theory (DFT) calculations. Vacuum-cleaved and exfoliated bulk crystals of Sb2Se3 are analysed using laboratory and synchrotron X-ray sources to acquire high resolution valence band spectra with both soft and hard X-rays. Utilising the photon-energy dependence of different orbital cross-sections and corresponding DFT calculations, the various orbital contributions to the valence band could be identified, including the 5s orbital's presence at the VBM. The ionization potential is also determined and places the VBM at 5.13 eV below the vacuum level, similar to other materials with 5s2 lone pairs, but far above those of related materials without lone pairs of electrons. [ABSTRACT FROM AUTHOR]

A comprehensive study of bulk molybdenum dichalcogenides is presented with the use of soft and hard X-ray photoelectron (SXPS and HAXPES) spectroscopy combined with hybrid density functional theory (DFT). The main core levels of MoS 2 , MoSe 2 , and MoTe 2 are explored. Laboratory-based X-ray photoelectron spectroscopy (XPS) is used to determine the ionization potential (IP) values of the MoX 2 series as 5.86, 5.40, and 5.00 eV for MoSe 2 , MoSe 2 , and MoTe 2 , respectively, enabling the band alignment of the series to be established. Finally, the valence band measurements are compared with the calculated density of states which shows the role of p-d hybridization in these materials. Down the group, an increase in the p-d hybridization from the sulfide to the telluride is observed, explained by the configuration energy of the chalcogen p orbitals becoming closer to that of the valence Mo 4d orbitals. This pushes the valence band maximum closer to the vacuum level, explaining the decreasing IP down the series. High-resolution SXPS and HAXPES core-level spectra address the shortcomings of the XPS analysis in the literature. Furthermore, the experimentally determined band alignment can be used to inform future device work., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Shell-isolated nanoparticles (SHINs) with a 37 nm gold core and an 11 nm tin dioxide (SnO 2 ) coating exhibited long-life Raman enhancement for 3 months and a wide pH stability of pH 2-13 in comparison with conventional SiO 2 -coated SHINs. Herein, Au-SnO 2 is demonstrated as a more durable SHIN for use in the technique Shell-Isolated Nanoparticles for Enhanced Raman Spectroscopy (SHINERS)., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Mixed ionic-electronic conductors (MIECs) that display high oxide ion conductivity (σ o ) and electronic conductivity (σ e ) constitute an important family of electrocatalysts for a variety of applications including fuel cells and oxygen separation membranes. Often MIECs exhibit sufficient σ e but inadequate σ o . It has been a long-standing challenge to develop MIECs with both high σ o and stability under device operation conditions. For example, the well-known perovskite oxide Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3- δ (BSCF) exhibits exceptional σ o and electrocatalytic activity. The reactivity of BSCF with CO 2 , however, limits its use in practical applications. Here, the perovskite oxide Bi 0.15 Sr 0.85 Co 0.8 Fe 0.2 (BiSCF) is shown to exhibit not only exceptional bulk transport properties, with a σ 3- δ (BiSCF) is shown to exhibit not only exceptional bulk transport properties, with a σ o among the highest for known MIECs, but also high CO 2 tolerance in a single-phase MIEC gives BiSCF a significant advantage over existing MIECs for practical applications.2 . The combination of high oxide transport properties and CO 2 tolerance in a single-phase MIEC gives BiSCF a significant advantage over existing MIECs for practical applications., (© 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)