Jun. 25, 2018

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There is something new under the sun. Conventionally, “solar energy" conjures images of the generation of heat, electricity or fuel, toward supplanting familiar fossil-fuel production methods. But an invited paper in the latest issue of one of the premier scientific journals in materials science, Advanced Materials (impact factor of 20) - authored by BGU faculty members Eugene A. Katz, Iris Visoly-Fisher, Daniel Feuermann and Jeffrey Gordon of the Jacob Blaustein Institutes for Desert Research, in collaboration with the Weizmann Institute's Reshef Tenne - recounts advances for two distinct, novel and unorthodox solar paradigms, for which the common denominator is the special role of highly concentrated sunlight.

The first paradigm is in nanotechnology: solar at the service of advancing materials science. Immensely concentrated solar radiation is exploited for the production of singular nanomaterials at temperatures that approach 3,000°C. Many of these nanomaterials - with extraordinary lubricant, optical and catalytic properties - had eluded experimental realization via conventional methods. So the special value of solar here lies in creating valued materials at the service of society, rather than for solar's traditional applications. The advantages of the solar strategy - relative to existing procedures for nanomaterial generation - are the absence of dangerous or toxic substances, far less time being required for the syntheses, simplicity, low cost, and the potential to be scaled up. These represent a unique combination in the world of nanotechnology.

The other paradigm involves taking advantage of concentrated sunlight as an inventive diagnostic tool to significantly accelerate the ability to probe the stability and degradation of organic and perovskite materials that constitute the latest generations of advanced photovoltaic technologies. Concentrated solar is used to elucidate how the processes were governing solar cell performance change over time. The time required for meaningful tests is dramatically reduced from years to hours. It also turns out that accelerated testing with concentrated solar reveals subtle aspects of degradation processes, which cannot be deciphered with tests under unconcentrated sunlight - of immense value to the solar-cell industry and researchers involved in photovolatic research and development.

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Figure caption: Illustration of one of the experimental configurations used in the two novel, unorthodox solar energy paradigms developed by BGU researchers. Outdoors, an optical system tracking the apparent trajectory of the sun concentrates sunlight to about 10,000 times its peak ambient intensity, and couples it into a highly-transmissive optical fiber that transports it to an indoor lab where experiments can be conducted under controlled conditions.

The irradiation of ordinary commercial chemical reactants inside an evacuated quartz ampule is shown in the upper right, along with a high-magnification electron-microscope image confirming the first experimental realization of a nanostructure comprising alternating layers of lead sulfide (PbS) and tin sulfide (SnS2) that are ordinarily misfit one to the other, but, at the nanoscale, can come together to form unique nanoparticles with special optical properties that open new possibilities in light detection and light-catalyzed chemical reactions. The drawing shows a cut-away view of the molecules and layers constituting the nanostructure.

The lower parts of the graphic show an organic solar cell being subjected to elevated solar intensities, toward studying highly accelerated performance degradation and  cell diagnostics, with valuable results that can be generated in hours rather than years.