Modern cities are wrapped in glass — towers, facades, and curtain walls stretching across entire skylines. Most of that surface does one thing: let light in, while quietly driving up cooling costs inside. Researchers at Nanyang Technological University in Singapore say they may have found a way to change that equation, with solar cells so thin they effectively disappear into the glass itself.
A solar cell thinner than a whisper
The numbers behind the NTU team’s achievement are worth pausing on. The perovskite absorber layers at the heart of these devices measure just 10 nanometers thick — approximately 10,000 times thinner than a human hair, and about 50 times thinner than conventional perovskite solar cells. At that scale, the material functions less as a physical layer and more as a molecular coating on glass.
Thickness is also adjustable. By controlling how much material is deposited during manufacturing, researchers can tune the cells’ transparency to suit different applications — from nearly clear window glass to lightly tinted architectural panels. The cells are described as color-neutral, meaning they wouldn’t visibly alter a building’s facade.
The semi-transparent version — using a 60-nanometer perovskite layer — achieved 7.6% power conversion efficiency while transmitting roughly 41% of visible light, ranking among the best reported for this category of device. Unlike conventional silicon panels, which depend heavily on direct sunlight, perovskite cells can generate electricity under diffuse or indirect light. That’s a meaningful advantage in the shadowed corridors between urban towers.
Why cities desperately need a new solar strategy
The problem with solar in dense cities has never really been about the technology. It’s been about geometry. Skyscrapers consume enormous amounts of electricity — a modern office tower can draw several gigawatt-hours annually — but their rooftop footprints are small relative to their total surface area. Rooftop solar, however well-deployed, can’t come close to meeting that demand.
Mounting conventional panels on vertical glass facades creates its own complications. Standard residential panels weigh between 18 and 23 kilograms each, and attaching them across curtain-wall skyscrapers would significantly alter a building’s structural load, thermal performance, and appearance. For most towers, it simply isn’t practical.
What cities do have, in abundance, is vertical glass. Entire city blocks are wrapped in it, permanently exposed to sky and ambient light — a surface that has historically been a liability, admitting light while driving up cooling costs. The NTU research is essentially an attempt to convert that liability into an asset.
The manufacturing method that could make it real
The thinness of these cells is notable. But the production method may matter just as much for whether this technology ever moves beyond the laboratory.
The NTU team used thermal evaporation — a vacuum-based process in which materials are heated until they vaporize and settle onto a surface as an ultrathin film. The researchers suggest this may be the first time ultrathin perovskite solar cells have been fabricated entirely through vacuum processing, a distinction that carries real industrial weight. Most experimental perovskite cells are produced using liquid chemical methods, which involve toxic solvents and can yield uneven films at larger scales. Thermal evaporation avoids both problems, enabling highly uniform, large-area deposition with precise thickness control and no solvent waste.
Thermal evaporation is already standard practice in semiconductor and display manufacturing, meaning the infrastructure, expertise, and supply chains to scale the process already exist. NTU has filed a patent through its commercialization arm, NTUitive, and says it’s actively working with industry partners to validate and standardize the approach.
From skyscrapers to smart glasses: the range of possible applications
The researchers offer a concrete illustration of the technology’s potential scale. If applied to the glass facade of One World Trade Center in New York, they estimate the coating could theoretically generate several hundred megawatt-hours of electricity per year — roughly enough to power around 40 average US homes annually.
That figure is theoretical, and the caveats are real. It still points toward something significant: distributed urban power generation that requires no additional land, no structural modification, and no visible hardware.
The potential extends beyond architecture. The NTU team identifies vehicle sunroofs, wearable electronics, and smart glasses as candidate applications — devices that could recharge continuously from ambient light without any visible solar component. Associate Professor Annalisa Bruno, who led the research, noted that the built environment accounts for roughly 40% of global energy consumption, giving technologies like this considerable long-term relevance.
The hurdle that has tripped up perovskites before
Excitement about perovskite solar cells isn’t new. The material has been generating attention for over a decade, and for good reason — its efficiency has climbed rapidly, and its manufacturing costs could undercut silicon. Commercialization, though, has consistently stalled at the same obstacle: durability.
Perovskites are sensitive. Moisture, oxygen, heat, and prolonged UV exposure can all degrade performance, and maintaining efficiency over years of real-world conditions remains one of the field’s central unsolved problems. A lab prototype producing strong results is a long way from thousands of square meters of solar glass on a skyscraper in a humid coastal city.
Professor Sam Stranks of the University of Cambridge, who wasn’t involved in the NTU research, acknowledged the work as promising while identifying the next critical tests as “long-term stability, durability and performance over larger areas.” That assessment reflects the field’s broader consensus: the science is advancing, but the engineering gap between prototype and product remains wide.
For now, the NTU technology is firmly in the research stage. What comes next — extended stability testing, larger-area fabrication trials, and real-world performance validation with industry partners — will determine whether these near-invisible cells can survive the transition from controlled laboratory conditions to the exposed, weathered surfaces of a living city. If they can, the glass already wrapping the world’s skylines may eventually start giving something back.