The solar cell used in the power window has a lifespan of 30 years

Solar energy is the cheapest form of energy produced by mankind since the Industrial Revolution. By using these devices on the windows, your building becomes a power plant.

Although silicon is still the king of solar panel efficiency, it is not transparent. For window-friendly solar panels, researchers have been exploring organic or carbon-based materials. The challenge facing the Forrest team is how to prevent the very efficient organic light conversion materials from rapidly degrading during use.

The advantages and disadvantages of these materials lie in the molecules that transport photo-generated electrons to the electrodes, the entry points of circuits that use or store solar energy. These materials are often referred to as "non-fullerene receptors" to distinguish them from the more robust but less efficient "fullerene receptors" made of nanoscale carbon mesh. Solar cells made of sulfur-doped non-fullerene acceptors can achieve 18% efficiency equivalent to silicon, but their service life is not long.

"Non-fullerene receptors have very high efficiency, but contain weak bonds that are easily dissociated under high-energy photons, especially ultraviolet [ultraviolet] photons that are common in sunlight," Assistant Research Scientist in Electrical Engineering and Computer Science at the University of Michigan Li Yongxi said. Author of Nature Communications paper.

By studying the degraded nature of those unprotected solar cells, the team realized that they only need support in a few places. First, they need to block ultraviolet rays. To this end, they added a layer of zinc oxide, a common sunscreen ingredient, to the side of the glass facing the sun.

The thinner zinc oxide layer near the light-absorbing area helps to conduct solar-generated electrons to the electrode. Unfortunately, it also destroyed the fragile light absorber, so the team added a layer of carbon-based material called IC-SAM as a buffer.

In addition, the electrodes that draw positively charged "holes" (essentially the space vacated by electrons) into the circuit can also react with light absorbers. To protect that side, they added another buffer layer, which is a fullerene shaped like a football.

The team then tested their new defenses under simulated sunlight of varying intensities, from the typical light of 1 sun to 27 suns, and temperatures as high as 150 degrees Fahrenheit. By studying how performance drops under these conditions, the team inferred that solar cells can still operate at 80% efficiency after 30 years.

Forrest sees the future of these devices "coming to a window near you." His team has increased the transparency of the module to 40%. They believe they can approach 60% transparency.

They are also working to increase efficiency from the 10% achieved in the translucent module of the report to close to the 15% that is believed to be possible with high transparency. Since the material can be made into liquid, the manufacturing cost is expected to be relatively low.