Science & Technology (Commonwealth Union) – As solar energy demand increases, the need to improve its efficacy becomes even more crucial.
A global research team led by the University College London (UCL) scientists have developed semi-transparent solar cells that can be integrated into windows to capture energy from both indoor lighting and sunlight.
The innovation, detailed in a study published in Advanced Energy Materials, could transform buildings into sources of renewable power by enabling them to generate electricity not only in direct sunlight but also at night and during overcast conditions.
The researchers created solar windows that allow around 30% of sunlight to pass through — compared with the 80% to 90% typically transmitted by conventional glass — while achieving record-breaking energy generation from indoor light and maintaining efficient solar power production outdoors.
Dr Mojtaba Abdi-Jalebi, senior author from the UCL Institute for Materials Discovery, indicated that while solar panels are widely installed on rooftops, the large glass surfaces of modern buildings remain an underused opportunity for renewable energy generation.
He pointed out that in their study, they showed it is feasible to maintain the window transparency so it is possible to permit light through while keeping the efficiency of the solar cells’.
Dr Abdi-Jalebi further indicated that the next step is to engineer flexible solar cells that have the ability to be used in curved structures such as windows on the Shard or on cars and non-rigid surfaces like clothes or backpacks. He pointed out that they would like to build solar cells over larger scales than they achieved in this research as well.
“The longer-term vision is to make semi-transparent photovoltaics as easy to integrate as a window film. As the technology matures, these devices could potentially be developed into flexible films that can be applied directly on to vehicle glass, sunroofs, and other transparent surfaces to generate clean electricity without major structural changes.”
Lead author Siming Huang, a PhD researcher at UCL’s Institute for Materials Discovery, indicated that the technology offers an additional benefit: by blocking part of the sunlight, it functions similarly to tinted glass, reducing the amount of energy needed to cool buildings. This could be particularly valuable in warmer regions where air conditioning accounts for a significant share of energy consumption.
The researchers relied on a material known as perovskite, which is becoming increasingly common in outdoor solar panels. Unlike conventional silicon solar cells, perovskite-based technology can potentially produce electricity from indoor lighting because its structure can be modified to absorb the specific wavelengths found in indoor environments.
Using computer simulations, the team identified the most effective combination of layer thicknesses and configurations to achieve a balance between maintaining transparency and maximizing energy conversion efficiency.
Guided by these simulations, they developed a light-absorbing perovskite layer measuring just 185 nanometres in thickness — roughly 500 times thinner than a human hair. In conventional perovskite solar cells, this active layer is typically three to four times thicker.
The researchers introduced a molecule called 3-trifluoromethyl-1H-1,2,4-triazole, which helped minimise imperfections in the perovskite material known as “traps.” These defects can capture electrons and prevent them from contributing to electricity generation. The added molecule also improved the stability of the perovskite crystal structure, helping to slow deterioration over time.
The team also developed a more transparent electrode design. In conventional perovskite solar cells, the electrode — the component responsible for extracting electrical current from the device — is usually made from gold, which limits the amount of light that can pass through. To overcome this issue, the researchers placed a very thin gold layer between two transparent molybdenum oxide layers. This structure increased light transmission by reducing the amount of light reflected by the gold.
