New Options for transparent contact electrodes
Scanning Electron Microscopy of Nanowires of Silver.
They have diameters around 0,1 micrometer and lenghts
between 5 and 10 micrometern. © ACS Nano 3: 1767-1774
Found in flat screens, solar modules, or in new organic light-emitting diode (LED) displays, transparent electrodes have become ubiquitous. Typically, they consist of metal oxides like In2O3, SnO2, ZnO and TiO2 .
But since raw materials like indium are becoming more and more costly, researchers have begun to look elsewhere for alternatives. A new review article by HZB scientist Dr. Klaus Ellmer, published in the renowned scientific journal Nature Photonics, is hoping to shed light on the different advantages and disadvantages of established and new materials for use in these kinds of contact electrodes.
Metallic (Ag or Cu) or carbon based nanostructures exhibit many interesting properties that could potentially be exploited pending further research.Even graphene, a modified form of carbon, could turn out to be a suitable transparent electrode, since it is both transparent and highly conductive. These properties depend, to a large extent, on the material's composition:graphene, which consists of a single layer of carbon atoms arranged into a hexagonal "honeycomb" grid, is two-dimensional, and, within these dimensions, electrons can freely move about.
According to Ellmer, "these new kinds of materials could be combined with more conventional solutions or find their way into entirely new areas of application." For this to become a reality, researchers have yet to come up with solutions to nanostructure problems like short circuits and continue to illuminate the relevant transport mechanisms. It would also be interesting to determine whether these two-dimensional "electron gases" also form in materials other than graphene. Success ultimately depends on whether or not the new materials prove stable in the long run in their practical application and whether or not they can be produced relatively inexpensively.
Ellmer is sole author of an extensive review article published in Nature photonics online on 30. November 2012, doi: 10.1038/nphoton.2012.282
- Joint Kyiv Energy and Climate Lab goes liveHelmholtz-Zentrum Berlin and the National University of Kyiv-Mohyla Academy established on 27 November a Joint Energy and Climate Lab.
- How carbonates influence CO2-to-fuel conversionResearchers from the Helmholtz Zentrum Berlin (HZB) and the Fritz Haber Institute of the Max Planck Society (FHI) have uncovered how carbonate molecules affect the conversion of CO2 into valuable fuels on gold electrocatalysts. Their findings reveal key molecular mechanisms in CO2 electrocatalysis and hydrogen evolution, pointing to new strategies for improving energy efficiency and reaction selectivity.
- Peat as a sustainable precursor for fuel cell catalyst materialsIron-nitrogen-carbon catalysts have the potential to replace the more expensive platinum catalysts currently used in fuel cells. This is shown by a study conducted by researchers from the Helmholtz-Zentrum Berlin (HZB), Physikalisch-Technische Bundesanstalt (PTB) and universities in Tartu and Tallinn, Estonia. At BESSY II, the team observed the formation of complex microstructures within various samples. They then analysed which structural parameters were particularly important for fostering the preferred electrochemical reactions. The raw material for such catalysts is well decomposed peat.