While the majority of the solar devices on market today are conventional solar panels that are installed on rooftops or in-field to produce power, there’s a lot of research and effort going into other types of photovoltaic (PV) devices. One of the most exciting areas is invisible photovoltaics. These are devices that you can see through, yet they are still able to provide power for lighting, charging smartphones, laptops, or other purposes. For instance, imagine if your smartphone could charge up purely through leaving it in your window, or your window could power a nearby lamp after dark. That’s the promise of see-through solar.
While the conversion power of such devices isn't anywhere close to that of conventional PV devices, the University of California, Los Angeles (UCLA) moved one step closer to commercializing its technology on July 29 by announcing that it has doubled the efficiency of its unique, see-through PV devices. The university said it accomplished the doubling in efficiency by creating a two-layered solar film. “The new device is composed of two thin polymer solar cells that collect sunlight and convert it to power,” the university said. Since the device uses two cells, it can absorb a wider spectrum of the sun’s light. The new device can convert about 7.3 percent of sunlight to electric power.
"Using two solar cells with the new interfacial materials in between produces close to two times the energy we originally observed," said Yang Yang, the Carol and Lawrence E. Tannas, Jr., professor of engineering at the UCLA Henry Samueli School of Engineering and Applied Science. "We anticipate this device will offer new directions for solar cells, including the creation of solar windows on homes and office buildings."
The new cells developed at UCLA are tandem polymer solar cells made of a photoactive plastic. “A single-cell device absorbs only about 40 percent of the infrared light that passes through,” the university said. “The tandem device — which includes a cell composed of a new infrared-sensitive polymer developed by UCLA researchers — absorbs up to 80 percent of infrared light plus a small amount of visible light.”
While the cells that researchers are currently working on are transparent, the team can also produce colored PV cells that are light gray, green or brown, the university said. As such, they could be useful in building-integrated photovoltaics — or even to power shaded versions of Google Glass or even solar-powered 3-D glasses. Yang and principal author, UCLA graduate student Chun-Chen, published the work online July 26 in Energy & Environmental Science, a Royal Society of Chemistry journal.
UCLA isn’t the only group working on transparent PV technologies. Sharp recently showed off its transparent PV modules at the PV Japan show earlier this month and plans to introduce them commercially this fall. Meanwhile other companies, like SunPartner Group, have already developed working prototypes of transparent PV. SunPartner Group’s WYSIP (What You See is Solar Power) was functionally demonstrated in an iPhone, with a functional touchscreen as early as 2011. As of 2013, however, no company has integrated such technology as a feature in a smart device.
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