Imagine if the windows in your home or office could quietly generate electricity while still letting daylight in.
That idea is moving closer to reality thanks to a new type of semi-transparent solar window developed by an international team of researchers led by University College London (UCL).
The new technology can capture energy not only from direct sunlight but also from indoor lighting, making it useful throughout the day and even when the weather is cloudy.
The findings were published in the journal Advanced Energy Materials.
Most buildings with solar power rely on rooftop panels, but windows make up a large part of the outside surface of many modern buildings.
Researchers believe these windows could become an important source of clean energy if they can produce electricity without becoming too dark.
The new solar windows allow about 30% of sunlight to pass through. While this is less transparent than ordinary glass, which usually lets through 80% to 90% of light, it still provides natural lighting while producing electricity.
The slight tint also helps reduce heat entering a building, which could lower air conditioning costs in warm climates.
The research team used a material called perovskite, which has attracted worldwide attention because it is cheaper and more versatile than traditional silicon used in most solar panels. One of perovskite’s biggest advantages is that its chemical makeup can be adjusted to absorb different types of light, including the wavelengths commonly found in indoor lighting.
Using computer simulations, the scientists carefully designed each layer of the solar cell to achieve the best balance between transparency and energy production. The light-absorbing perovskite layer they created was only 185 nanometers thick—about 500 times thinner than a human hair and several times thinner than those used in many conventional perovskite solar cells.
The researchers also added a special chemical compound called 3-trifluoromethyl-1H-1,2,4-triazole. This reduced tiny flaws, known as traps, inside the material that can prevent electricity from flowing efficiently. The compound also helped make the perovskite crystals more stable, improving the device’s durability.
Another important improvement involved the transparent electrode, which carries electricity out of the solar cell. Standard perovskite solar cells often use gold electrodes, but gold blocks much of the incoming light. To solve this problem, the team placed an extremely thin layer of gold between two transparent layers of molybdenum oxide. This design reduced light reflection and allowed more light to pass through while still conducting electricity.
The researchers built a demonstration panel measuring 30 by 30 centimeters. Tests showed it converted 22% of bright indoor light into electricity and achieved 14% efficiency under direct sunlight. In durability testing, the device maintained 80% of its original performance after 300 hours of continuous illumination.
The researchers hope that future versions can be made flexible enough to apply as films on windows, vehicle glass, sunroofs, backpacks, clothing, and other curved or lightweight surfaces.
If successful, this technology could one day transform ordinary windows into clean energy generators without major changes to building design.
