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Thin Film Solar Cells for Windows

thin film solar cells

What if your windows could be solarized? It's on the horizon, and we're not talking big bulky solar panels doubling as windows. The technology behind "solar window covering thin film" involves tiny, transparent solar cells applied directly onto glass. In other words, it looks just like a regular window, slightly tinted, that you can see in and out of, but doing double-duty as an invisible solar system.

Yet for all the hype surrounding solar window covering thin film, the information out there is just that - thin. You'll see a number of sources linked throughout this article, but overall they're lacking in depth. Not only would it be nice to have more detailed, reader-friendly explanations of the technology itself, but also specifics on the production process, anticipated cost and availability. The basics gleaned from online information is outlined below, starting with a general discussion of solar cell technology and thin film solar cells in particular.

What Are Solar Cells?

Solar cells, or photovoltaic (PV) cells, utilize semi-conductors that conduct electricity when heated by the sun and/or combined with other materials. Most solar applications utilize traditional silicon solar cells, however, thin-film solar cells are finding a respectable niche in the solar market.

What Are Thin Film Solar Cells?

Thin film solar cells are made from one of three semi-conducting materials:

  1. Amorphous Silicon (a-Si) is essentially a mini-version of the traditional silicon solar cell technology. The least efficient of the thin-film solar cells, a-Si is best-suited to small-scale applications, like calculators.
  2. Cadmium Telluride (CdTe), though energy efficient, poses an environmental hazard as cadmium is highly toxic and can accumulate in food chains.
  3. Copper Indium Gallium Diselenide (CIGS) is the most energy efficient of the thin-film technologies. However, it is also the most variable, as it utilizes four metal alloys and processes that leave a lot of room for impurities to interfere with quality.

As the name implies, thin-film solar cells are extremely thin at just 1 micron thick, compared to the 350 micron thickness of traditional silicon cells. Thin-film solar cell efficiency levels vary. For instance, CdTe solar cells may get as much as 15 percent efficiency, and CIGS as much as 20 percent, though levels may also be significantly lower depending on the manufacturer and manufacturing process.

How are Thin Film Solar Cells Applied to Windows?

Thin film solar cells can be sprayed directly onto windows, creating a transparent layer of solar power generators that harness the energy of the sun and turn it into usable electricity.

What Are the Major Developments in Solar Window Covering Thin Film Technology?

Though there is no current mass-production of solar window covering thin film technology, five organizations - from four different countries - seem to represent the most significant developments on the horizon:

  • In partnership with the Los Alamos National Laboratory and the Brookhaven National Laboratory, the U.S. Department of Energy has developed a solar window covering thin film from "fullerines". As explained at, fullerines are "molecules composed of 60 carbon atoms, shaped roughly like a soccer ball. Fullerines have the ability to assemble themselves into a honeycomb-like pattern of hexagons. When they are applied to a polymer they end up pushing the polymer chains to the edges of the hexagons, and that makes the resulting material transparent."

  • Japan's Kyosemi Corporation has developed solar window covering thin film from "Sphelar cells", which are solidified silicon drop-based solar cells measuring 1.8 millimeters in diameter. In addition to flat window panes, Sphelar cell technology can be applied to flexible surfaces as well, so that these surfaces can be bent and otherwise manipulated so as to harness maximum solar energy at various times of the day.

  • China's Chin Hua solar company makes double-glazed window units designed to drop in as replacements for regular windows. As explained by, "Chin Hua claims that a normal-sized window will generate around 2W of energy not a massive amount, its true, but enough to take the edge off your energy bills. Where the technology really gets interesting is if you multiply it across a building with lots of windows for example, a skyscraper. Assuming a building of a similar size to the Empire State building which has 6,500 windows adorning its surface it could be possible to generate around 13KW of power."

  • In partnership with the University of Leicester's Department of Physics and Astronomy, Norway's Ensol, Inc., has developed a unique solar window covering thin film, in that it utilizes a "vapor deposition" process in conjunction with metal nanoparticles embedded in a transparent composite matrix. Ensol also anticipates being able to apply this same spray-on technology to the sides of buildings. Currently, the production of this technology is limited to 16-square-centimeter prototypes.

  • U.S.-based New Energies Technologies Inc., produces the SolarWindow which may go one step further than other technologies currently in development - solar window covering thin film that harnesses energy from artificial light sources as well. However, the claims of New Energies Technologies may need to be taken with a grain of salt. Though the SolarWindow is among the most high-profile of products in the solar window covering thin film market, there is some controversy surrounding the integrity of New Energies Technologies' leadership, as reported by

When Will Solar Window Covering Thin Film Technology be Commercially Available?

The only company that has committed to an availability date of solar window covering thin film is Ensol, with projected availability in 2016.


Though the energy harnessed by solar window covering thin film may be just a fraction of that captured by rooftop solar panels, it's an inspiring step in the right direction - exploring every possible way of maximizing solar power. Let's just hope the technology proves viable for mass-market distribution. If so, the aesthetic appeal of floor-to-ceiling windows may be surpassed by the eco-friendly, economical benefits of window-covered walls