Producing Less Expensive Solar Panels
The islands absorb photons and convert them to electrons, while light striking the empty areas passes through. The result was a transparent solar cell with a grayish tint. As the transparency of the film increases, efficiency decreases. The most transparent cells, which let through about 30% of incoming light, converted light to electricity with efficiencies of 3.5%. The darkest films, only 7% transparent, had efficiencies near 8%. Snaith says the ideal coating would let through about half the light and have a 5% conversion efficiency. We think theres a lot of scope to improve it further, he says. Hes formed a company, Oxford Photovoltaics , with the hope of commercializing a device by 2017. Snaith says the next step is to determine the stability of the material. A practical solar cell should function for several years. But even if it stops generating electricity, the window containing the cell should maintain its color and transparency for at least a decade.
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Laser processing can lower temperatures used in solar cell production
In a newly released report (fee charged), the researchers stated that use of a thin film of a mineral called perovskite could form see-through, flat solar cells with comparatively high efficiencies. Perovskite is an oxide used in ceramic superconductors. Using a transparent oxide, researchers were able to create see-through solar cells (Source: Oxford University). The thin-film photovoltaics are dispersed like “islands” throughout the glass and are small enough “to appear continuous to the eye yet large enough to enable unattenuated transmission of light between the islands,” the researchers stated. Photovoltaic technology converts light into electrical energy. The photovoltaic islands are also thick enough to absorb most visible light. “Using these films, we fabricate thin-film solar cells with respectable power conversion efficiencies,” the researchers said. “Remarkably, we find that such discontinuous films still have good rectification behavior and relatively high open-circuit voltages.” The scientists said they were also able to easily tint the photovoltaic arrays with colored dye and have no reduction in performance.
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HZB Scientists Upgrade Chalcopyrite Solar Cells
In typical solar cell manufacturing , the surface of the cell is doped in a process that involves heating the entire silicon wafer to a temperature in the range of 800 to 900C. The process can damage the silicon and wastes considerable energy. Laser doping works by firing a focused laser beam on the wafer. A small amount of dopant is initially sitting on the surface. The laser beam actually melts the silicon, which then re-solidifies, usually in less than one microsecond. The microsecond, however, is enough time to accomplish the doping. Because the laser delivers energy to a very localized area, it would heat only that portion of the wafer that needs to be heated and can lead to more efficient solar cells.
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They are typically made by blending two materials together. Using a combination of sophisticated laser measurements and very high resolution microscopy, the team were able to see the differences between a highly efficient and a less efficient solar cell. They found that the materials were arranged in a fibre-like structure in the efficient solar cells, but as tiny balls in the less efficient cells. The results are important because they suggest how to make even better solar cells. They are published in the journal Nature Communications. Professor Samuel said: “The results are important because they suggest how to make efficient, low cost solar cells.” Team member Dr Hedley added: “Seeing fibre-like structures was an interesting surprise.” Organic solar cells are a promising renewable energy technology made of a thin (100 nanometre) layer that absorbs most incoming sunlight. The absorbing layer is a mixture of a light-absorbing plastic and a football-shaped carbon molecule. The solar cell is fabricated by dissolving the two materials in a liquid and then depositing them onto a substrate. Current record efficiency organic solar cells are competitive with amorphous silicon photovoltaic cells.
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Transparent solar cells could turn windows into generators
Layer properties were measured as a function of the S/(S+O) ratio and initial solar cells were produced that ended up working rather well. As soon as the optimal ratio had been determined, a properly mixed target was built in. Says Klenk: We were able to show that this actually works. For production, you would really only need to replace the ZnO target with a ZnO/ZnS target at a set mix ratio, which would allow you to do without any preceding deposition of a dedicated buffer layer. Meaning we would have realized a dry, Cd-free, in-line process without a major investment. In the lab, this now works without having to compromise efficiency. The HZB researchers were able to get up to 18.3 per cent, a number that was confirmed by measurements taken at the renowned ISE Fraunhofer Institute in Freiburg, Germany . Compared with other approaches to producing cadmium-free solar cells, with this process, pretreating the surface or following up with a temperature treatment have become obsolete.
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