Two-dimensional layered WS 2 sheets is used as the hole extraction layer (HEL) in organic solar cells (OSCs).We find that UV-ozone treatment of the chemically exfoliated WS 2 sheets can significantly improve the device performance of the OSCs with the power conversion efficiency (PCE) of about 8.37%, which is comparable to the OSCs with the standard PEDOT:PSS as the HEL.We attribute the improvement to the incorporation of oxygen into the lattice of the WS 2 sheets.The oxygen incorporation reduces the lattice vacancies of WS 2 sheets and makes the WS 2 partially oxidized and consequently improves the electrical properties of the WS 2 sheets.
Abstract Chemical vapor deposition on metal substrates using gaseous hydrocarbon as carbon feedstock has proven to be a feasible way for synthesis of large‐area and uniform graphene films. Meanwhile, rearrangement of amorphous carbon species extracted from solid carbon sources into crystalline graphene not only offers an alternative route for graphene growth but also provides a powerful tool to excavate the underlying mechanisms of graphene formation. In this review, we discuss the processes of extracting carbon species from various solid carbon sources to form graphene. We summarize the typical steps of solid carbon sources to graphene transition and evaluate the resultant graphene film quality with regard to electrical performance. Unveiling the detailed solid carbon to graphene transition process paves the way for a reproducible production of graphene with controlled layer number, defect type and density, toward the final end of graphene's commercial utilizations with low cost.
A single-atom metal doped on carbonaceous nanomaterials has attracted increasing attention due to its potential applications as high-performance catalysts. However, few studies focus on the applications of such nanomaterials as nanotheranostics for simultaneous bioimaging and cancer therapy. Herein, it is pioneeringly demonstrated that the single-atom Gd anchored onto graphene quantum dots (SAGd-GQDs), with dendrite-like morphology, was successfully prepared. More importantly, the as-fabricated SAGd-GQDs exhibits a robustly enhanced longitudinal relaxivity (r1 = 86.08 mM-1 s-1) at a low Gd3+ concentration of 2 μmol kg-1, which is 25 times higher than the commercial Gd-DTPA (r1 = 3.44 mM-1 s-1). In vitro and in vivo studies suggest that the obtained SAGd-GQDs is a highly potent and contrast agent to obtain high-definition MRI, thereby opening up more opportunities for future precise clinical theranostics.
2D layered CrS2 flakes down to the monolayer are successfully synthesized, and different phases of CrS2 are observed and exhibit direct band gap p-type semiconducting, metallic, and semi-metallic behaviors, respectively.
Graphene nucleation at oxygen-rich Cu sites instead of on the commonly assumed pure Cu surface is discovered using high-spatial-resolution scanning Auger electron microscopy, which reveals a strong O signal existing underneath the graphene seeds, along with density functional theory calculations.
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