{"id":10832,"date":"2016-04-18T23:24:43","date_gmt":"2016-04-19T06:24:43","guid":{"rendered":"http:\/\/cafe.foundation\/blog\/?p=10832"},"modified":"2016-04-18T23:24:43","modified_gmt":"2016-04-19T06:24:43","slug":"superlattices-and-solar-cells-that-work-at-night","status":"publish","type":"post","link":"http:\/\/cafe.foundation\/blog\/superlattices-and-solar-cells-that-work-at-night\/","title":{"rendered":"Superlattices and Solar Cells that Work at Night"},"content":{"rendered":"

Bob Elliott of the comedy team Bob and Ray <\/a>died February 3, reminding your editor of one of the many routines Elliott\u00a0and Ray Goulding performed on live radio.\u00a0 It involved an inventor who had perfected a solar panel that could run the lights in your house all day, but couldn’t\u00a0keep them going at night when they were really needed.\u00a0 That was over 50 years ago, and investigators at the Pacific Northwest National Laboratory, Argonne National Laboratory, SuperSTEM, and the University of Oxford have come up with a possible solution to Bob and Ray\u2019s quandary<\/a>.<\/p>\n

\"The

The interfaces between the two oxides (represented in this idealized, atomically abrupt model by the yellow and purple bands) create an electric field. The field separates electrons (silver) excited by sunlight (gold), which could be used to catalyze hydrogen fuel production.<\/p><\/div>\n

Combining two oxides, one containing strontium and titanium (SrTiO3) and the other lanthanum and chromium (LaCrO3), they came up with a material that uses the interface between the two oxides to absorb visible light and produce electrons (negative charges) and holes (positive charges), which might be \u201cuseful for catalyzing reactions, such as producing hydrogen fuel.\u201d<\/p>\n

The oxides have to be kept apart, though, because otherwise, \u201cthey will quickly annihilate one another without doing anything useful,\u201d somewhat like a Hollywood marriage.\u00a0 The international team cleverly synthesized the material as a series of alternating layers with a built-in electric field that separates the excited electrons and holes.\u00a0 This strategy makes the materials an excellent catalyst.<\/p>\n

A visual representation of this interaction might resemble a moire pattern, but possibly only to your editor.<\/p>\n

\"The<\/p>\n

By controlling the interfaces to have either a positive or negative charge, the resulting electric fields can interact with electrons and holes excited by solar energy, driving electrons to the surface, where they interact with water molecules, break their bonds and produce hydrogen.<\/p>\n

Bob and Ray would be proud.\u00a0 Researchers report, \u201cThis material opens up new scientific frontiers to solve a persistent energy challenge: storing solar energy for later use. Fuel cells capable of running on hydrogen fuel created by solar energy could allow people to heat their homes and run their computers on solar energy even in the dark of night.\u201d\u00a0 Or fly their solar-powered airplanes anywhere at any time.<\/p>\n

Researchers are exploring the properties of these superlattices<\/em> using cutting-edge X-ray measurements at synchrotrons around the world and using other advanced microscopy techniques to look at the chemical makeup of the interfaces.<\/p>\n

As one would guess, this type of research requires heavy hitters in intellectual and fiscal terms. \u00a0Participants included the Linus Pauling Distinguished Post-doctoral Fellowship at Pacific Northwest National Laboratory (PNNL Laboratory Directed Research and Development, the U.S. Department of Energy (DOE),\u00a0Office of Science<\/a>,Office of Basic Energy Sciences<\/a>\u00a0(BES),\u00a0Division of Materials Sciences and Engineering<\/a>, PNL\u2019s Laboratory Directed Research and Development program,. Sector 20 facilities at the Advanced Photon Source (APS), the DOE BES, the Canadian Light Source and its funding partners, the University of Washington, and the APS.\u00a0 \u00a0Electron microscopy was carried out in parts at the SuperSTEM Laboratory, the U.K. National Facility for Aberration-Corrected scanning transmission electron microscopy, which is supported by the Engineering and Physical Sciences Research Council (EPSRC). The research leading to these results has received funding from the European Union Seventh Framework Program.<\/p>\n

The team\u2019s paper, “Interface-Induced Polarization in SrTiO3-LaCrO3\u00a0Superlattices,”<\/a> was authored by Ryan B. Comes1,*,\u00a0Steven R. Spurgeon1,Steve M. Heald2,\u00a0Despoina M. Kepaptsoglou3,\u00a0Lewys Jones4, Phuong Vu Ong1,\u00a0Mark E. Bowden5,\u00a0Quentin M. Ramasse3,\u00a0Peter V. Sushko1\u00a0and Scott A. Chambers, and published in \u00a0Advanced Materials Interfaces<\/em>.<\/p>\n