Megan Fellman, reporting for Northwestern University in Evanston, Illinois, explains a possible breakthrough in obtaining power conversion efficiency for polymer (plastic) solar cells close to those for more expensive silicon cells. Fellman lists the benefits of the plastic cells: “Among the various photovoltaic technologies, polymer (plastic) solar cells offer unique attractions and opportunities. These solar cells contain Earth-abundant and environmentally benign materials, can be made flexible and lightweight, and can be fabricated using roll-to-roll technologies similar to how newspapers are printed. But the challenge has been improving the cells’ power-conversion efficiency.” Faculty members and students led by Professor Tobin J. Marks designed and synthesized new polymer semiconductors, “and reports the realization of polymer solar cells with fill factors of 80 percent – a first. This number is close to that of silicon solar cells.” “Fill factor” is a measure of the ratio of the maximum power from the solar cell to the product of Voc (open-circuit voltage) and Isc (short-circuit current). The link …
Nanowire Solar Cells Surprise and Excite
Long-time friend of the blog, and occasional corrector of the editor’s attempts at incorporating French into the proceedings, Colin Rush sent this link to a story about photonics in the Christian Science Monitor. “Wires 1/10,000th the diameter of a human hair can absorb more of the sun’s power than previously thought possible, a new study in Nature Photonics suggests,” writes David Unger, an energy correspondent for the Monitor. Unger’s lead paragraphs pushed your editor to look up several related terms and look further into the researchers’ own writing. “Although still years away from production, nanowire solar cells could push the conversion efficiency of the sun’s energy past the so-called Shockley-Queisser limit, which for decades has served as a fixed ceiling in solar energy research. “Such a breakthrough would be significant because the sun’s power is wildly abundant, but diffuse, and difficult to harvest. Even increasing the limit by a few percent would go a long way in making solar a more viable alternative to …
There’s Light at the End of the Funnel
Solar cells are relatively inefficient at gathering the total range of sunlight’s spectrum that falls on them every day. Trying to find a way to capture more than a single wavelength or narrow band of the solar light, scientists at Massachusetts Institute of Technology (MIT) and at Peking University in China propose putting a strain on solar cells, creating a spatially varying bandgap that would react to more of the colors in light and thus give off more electricity. Changing the bandgap in a solar collector’s material enables excitation of electrons from not just visible light, but from energy sources such as infrared radiation. This has the potential to increase the cell’s energy output enormously since most of the sun’s radiation is in invisible form. Bandgap is a complex concept, and MIT provides a brief tutorial here. MIT’s news office reports: “’We’re trying to use elastic strains to produce unprecedented properties,’ says Ju Li, an MIT professor and corresponding …
Spinach, Photosynthesis, and Solar Energy
Spinach is the Rodney Dangerfield of the vegetable kingdom, and despite the best efforts of nutritionists, Popeye, and school lunch ladies to boost its respect levels, goes unwanted by many. But not by the team at Vanderbilt University who have combined it with silicon in a “biohybrid” solar cell. According to Vanderbilt’s David Cliffel, associate professor of chemistry, “This combination produces current levels almost 1,000 times higher than we were able to achieve by depositing the protein on various types of metals. It also produces a modest increase in voltage.” Cliffel collaborated on the project with Kane Jennings, professor of chemical and biomolecular engineering. “If we can continue on our current trajectory of increasing voltage and current levels, we could reach the range of mature solar conversion technologies in three years.” Over 40 years ago, scientists found that Photosystem 1 (PS1), a protein involved in photosynthesis, continued to produce photosynthetic energy even after it was removed from its host plant. …