Energy efficient LEDs and lasers with Chalcogenide monolayers
2 (orange) on top of MoS2 (blue). The SPEEM-microscopy reveals coupling between both layers and charge transfer. © F. Kronast/HZB
As reported by nanotechweb.org, monolayers of certain chalcogenides might be used to make energy-efficient nano-optoelectronics devices, such as LEDs, lasers, solar cells, and high-electron-mobility transistors. Scientists of the University of California at Berkeley, the Lawrence Berkeley National Lab and the Helmholtz-Zentrum Berlin für Materialien und Energie in Berlin investigated the electronic and optoelectronic properties of a so called heterojunction of WSe2/MoS2.
“At BESSY II we performed local x-ray photoemission spectroscopy at the SPEEM microscope and could observe interlayer coupling and charge transfer in this new type of heterojunction”, Dr. Florian Kronast, HZB, explains. This makes these types of heterojunctions interesting candidates for new devices.
To the article in nanotechweb
The present work is detailed in PNAS doi: 10.1073/pnas.1405435111.
- Battery research with the HZB X-ray microscopeNew cathode materials are being developed to further increase the capacity of lithium batteries. Multilayer lithium-rich transition metal oxides (LRTMOs) offer particularly high energy density. However, their capacity decreases with each charging cycle due to structural and chemical changes. Using X-ray methods at BESSY II, teams from several Chinese research institutions have now investigated these changes for the first time with highest precision: at the unique X-ray microscope, they were able to observe morphological and structural developments on the nanometre scale and also clarify chemical changes.
- BESSY II: New procedure for better thermoplasticsBio-based thermoplastics are produced from renewable organic materials and can be recycled after use. Their resilience can be improved by blending bio-based thermoplastics with other thermoplastics. However, the interface between the materials in these blends sometimes requires enhancement to achieve optimal properties. A team from the Eindhoven University of Technology in the Netherlands has now investigated at BESSY II how a new process enables thermoplastic blends with a high interfacial strength to be made from two base materials: Images taken at the new nano station of the IRIS beamline showed that nanocrystalline layers form during the process, which increase material performance.
- Hydrogen: Breakthrough in alkaline membrane electrolysersA team from the Technical University of Berlin, HZB, IMTEK (University of Freiburg) and Siemens Energy has developed a highly efficient alkaline membrane electrolyser that approaches the performance of established PEM electrolysers. What makes this achievement remarkable is the use of inexpensive nickel compounds for the anode catalyst, replacing costly and rare iridium. At BESSY II, the team was able to elucidate the catalytic processes in detail using operando measurements, and a theory team (USA, Singapore) provided a consistent molecular description. In Freiburg, prototype cells were built using a new coating process and tested in operation. The results have been published in the prestigious journal Nature Catalysis.