Researchers at Michigan State University have created a fully transparent solar concentrator, which could turn any window or sheet of glass like a smartphone’s screen into a photovoltaic solar cell.
Unlike other “transparent” solar cells that are not truly transparent, the newly developed panel is fully transparent. According to Richard Lunt, who led the research, the team are confident that the transparent solar panels can be efficiently deployed in a wide range of settings, from “tall buildings with lots of windows or any kind of mobile device that demands high aesthetic quality like a phone or e-reader.”
Scientifically, a transparent solar panel is something of an oxymoron. Solar cells, specifically the photovoltaic kind, make energy by absorbing photons (sunlight) and converting them into electrons (electricity). If a material is transparent, however, by definition it means that all of the light passes through the medium to strike the back of the human eye. This is why previous transparent solar cells have actually only been partially transparent — and, to add insult to injury, they usually cast a colorful shadow too.
To get around this limitation, the Michigan State researchers use a slightly different technique for gathering sunlight. Instead of trying to create a transparent photovoltaic cell (which is nigh impossible), they use a transparent luminescent solar concentrator (TLSC). The TLSC consists of organic salts that absorb specific non-visible wavelengths of ultraviolet and infrared light, which they then luminesce (glow) as another wavelength of infrared light (also non-visible). This emitted infrared light is guided to the edge of plastic, where thin strips of conventional photovoltaic solar cell convert it into electricity. [Research paper: DOI: 10.1002/adom.201400103 – “Near-Infrared Harvesting Transparent Luminescent Solar Concentrators”]
The organic salts absorb UV and infrared, and emit infrared — processes that occur outside of the visible spectrum, so that it appears transparent.
Michigan’s TLSC currently has an efficiency of around 1%, but are aiming for 5% efficiency, which they see as ‘possible’. Non-transparent luminescent concentrators (which bathe the room in colorful light) max out at around 7%. While small by itself, the story is different on a larger scale — every window in a house or office block — the numbers quickly add up and becomes more significant.
The researchers are confident that the technology can be scaled all the way from large industrial and commercial applications, down to consumer devices, while remaining “affordable.” So far, one of the larger barriers to large-scale adoption of solar power is the intrusive and ugly nature of solar panels — aesthetically this would be a game changer if the TLSD can be produced in large amounts to exploit all the solar power in the environment while having the look of normal sheets of glass and plastic.