SadaNews – The idea of generating electricity from building facades is no longer confined to traditional solar panels on rooftops. Researchers from Nanyang Technological University in Singapore have developed a new type of ultra-thin, semi-transparent solar cells that could pave the way for integrating solar energy into windows, glass facades, and potentially cars and wearable devices, without significantly altering their external appearance.
Cells That Are Almost Invisible
The research team is led by Professor Annalisa Bruno from Nanyang Technological University. The researchers managed to produce solar cells from perovskite with an absorption layer thickness of only 10 nanometers, making them about 10,000 times thinner than a human hair and about 50 times thinner than traditional perovskite cells. Despite this limited thickness, the cells achieved efficiency levels that are among the best recorded in the category of ultra-thin solar cells of this kind.
The significance of these cells comes not only from their thinness but also from their semi-transparent and color-neutral nature. This means that they can be integrated into glass and windows without turning buildings into dark surfaces or significantly altering the appearance of facades. Practically, windows could become part of the energy-producing infrastructure rather than just an architectural element that lets in light.
Why Perovskite?
Traditional solar cells often rely on silicon, but they tend to be opaque and require dedicated spaces such as rooftops or solar fields. On the other hand, perovskite cells can be manufactured using simpler methods and at relatively low temperatures, and can be tuned to absorb specific wavelengths of light while allowing some visible light to pass through.
Professor Bruno states that the built environment consumes about 40 percent of global energy, so there is an increasing need for technologies that can convert the surfaces of buildings themselves into sources of energy. She sees the new perovskite cells as providing a significant advantage because they can be manufactured through relatively simple processes, and their optical properties can be adjusted to remain partially transparent, with potential scalability over large areas.
This point is crucial for dense cities, where rooftops are not always sufficient for installing a large number of solar panels. The glass facades in towers and commercial buildings represent a vast area that is often underutilized for electricity generation.
Performance Under Indirect Light
One of the advantages of perovskite cells is their ability to generate electricity even in conditions of indirect or diffuse light. This makes them suitable for urban environments where shadows, clouds, or the angle of sunlight may limit the effectiveness of traditional panels, particularly on vertical facades.
According to preliminary estimates provided by the researchers, if this technology is scaled up while maintaining similar performance, a large glass facade in an office building could generate several hundred megawatt-hours annually. This amounts to, as cited in the study, the annual electricity consumption of about 100 four-room apartments in Singapore, with results varying based on the usable glass area and the building’s orientation.
Manufacturing without Toxic Solvents
To produce these ultra-thin cells, the researchers used an industrial method known as thermal evaporation. In this process, materials are heated inside a vacuum chamber until they vaporize, then deposited on a specific surface to form a uniform thin layer. This method helps in precisely controlling the thickness of the perovskite layers, avoids the use of some toxic solvents, and reduces defects within the cell, which can improve its ability to convert light into electricity.
The team believes that this is the first time ultra-thin perovskite cells have been made entirely using vacuum-based processes. If the scalability of this process is proven, it could become more suitable for large-scale industrial production compared to some other laboratory-based techniques.
Efficiency and Transparency Figures
The researchers successfully manufactured opaque perovskite cells with varying thicknesses. The cells achieved a power conversion efficiency of around 7 percent at a thickness of 10 nanometers, 11 percent at 30 nanometers, and 12 percent at 60 nanometers. The semi-transparent cell with a layer thickness of 60 nanometers allowed about 41 percent of visible light to pass through, with a conversion efficiency of 7.6 percent.
These figures do not imply that the technology competes with traditional silicon panels in absolute efficiency, but they offer a degree of transparency while generating useful electricity. This is the essence of applications like solar windows or energy-producing glass facades, where dark or opaque panels cannot always be used.
Potential Uses
The most obvious application is in buildings, as these cells can be used in windows, glass facades, and architectural surfaces that are difficult to cover with traditional solar panels. However, the researchers also point to other potentials, such as car windows or glass roofs that help charge the battery while parked under the sun, or smart glasses that exploit lenses to power small electronic components.
These uses are still within the realm of research potential and are not yet ready for commercial products. However, they reflect a broader trend in solar energy where the focus shifts from installing panels in specific places to integrating electricity generation within everyday materials and surfaces.
What Is Still Missing?
Despite the promising results, there are still challenges to reach commercial use. An independent comment from Professor Sam Stranks of the University of Cambridge notes that the results provide a promising balance between transparency and energy generation, but the next critical tests will focus on long-term stability, durability, and performance over larger areas.
These points are essential because windows and facades do not operate inside a laboratory. They are exposed to heat, humidity, dust, sunlight, and constant cleaning, and need a long operational life. Therefore, the success of the cell in the lab is not sufficient on its own to prove its ability to function in a building, car, or wearable device for years.
Nanyang University has filed a patent application related to the development of these ultra-thin films, and the researchers are in discussions with companies to verify and standardize the manufacturing process while continuing to work on improving stability, durability, and performance over large areas.
City Energy from Glass
This study comes at a time when cities are under increasing pressure to generate clean energy without needing additional land. Solar panels on rooftops are important, but they do not utilize all available spaces in high-density urban areas. Glass and vertical facades could potentially become an additional layer for electricity generation in the future if transparent or semi-transparent cells successfully overcome challenges of efficiency, durability, and large-scale production.

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