Windows of the future would not only bring in light, they will convert it into electricity. Scientists are working to make that happen sooner than we might think.

Throughout history and across pretty much all civilizations, windows have been a trademark architectural feature with a vital functionality. Regardless of their style and size, windows have always been used to bring in light and air, and seal out the elements.

Dye sensitized solar cells will bring us power-generating windows.Click To Tweet

For eons, windows were made primarily from wood, steel, and aluminum framing, with glass as the main component that ensures the integrity of the thermal envelope while transmitting brightness.

Future windows would embrace solar power, and by “solar windows”, we’re not speaking of windows powered by solar, but windows that harvest this power.

Dye Sensitized Solar Cells

The dye sensitized solar cell (DSSC), a.k.a. the Grätzel cell, was invented by Michael Grätzel and Brian O’Regan at the EPFL (École Polytechnique Fédérale de Lausanne).

DSSCs mimic the natural phenomenon of photosynthesis by which cells absorb light energy.

To convert sunlight into electricity, DSSCs use organic dyes that are photoactive, meaning they get sensitized by light, from natural or artificial sources, and excite coming electrons in a similar way to natural chlorophylls. A semiconductor then carries the excited electrons through a closed circuit.

While less efficient than conventional photovoltaic cells, DSSCs are more efficient in dim-light conditions, like in the morning and in the evening, or when the weather is cloudy or indoors.

What’s more, DSSC production is more cost-effective, flexible and consumes less power, compared to silicon-based solar panels.

This opens up solar power to new horizons, as DSSCs could be incorporated into windows, once their efficiency comes close to or exceed that of conventional photovoltaic panels (26.3% with a theoretical maximum of 29%).

Right now, after over two decades of development, DSSCs have achieved a record efficiency rate of 14.1%, thanks to the work of their inventor, Michael Grätze, and his team.

DSSC-Based Solar Windows Closer to Becoming a Reality

If 14% efficiency doesn’t seem like much, the first cell invented, in 1991, by Grätzel et al. had only ∼7% efficiency. By the year 2000, DSSCs efficiency increased to about 10%, then to 13% in 2014.

With the increase in efficiency, there was an increase in research dedicated to DSSCs and overall interest in the technology. Over two decades (1996-2016), thousands of scientific studies related to DSSC technology have been published.

To achieve higher energy-conversion rates and make the production process even more economical, scientists are investigating the underlying mechanisms of DSSC.

The findings of a study by materials scientists from the University of Cambridge pave the way towards engineering efficient DSSC energy-producing windows.

Another team at the U.S. Department of Energy’s NREL (The National Renewable Energy Laboratory) has developed a prototype of a “smart window” with an efficiency rate of 11.3%.

The NREL switchable photovoltaic window can shift from transparent to tinted, to lower building temperatures, while generating electricity.

“There is a fundamental tradeoff between a good window and a good solar cell,” said NREL’s Lance Wheeler, a scientist at. “This technology bypasses that. We have a good solar cell when there’s lots of sunshine and we have a good window when there’s not.”

With over 11% efficiency, this solar window could be already competitive with photovoltaic panels.

In waiting for the development of this innovation for future smart, energy-sustainable, cities, could we see DSSC films on the glass roofs of electric cars?

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