en.Wedoany.com Reported - Imagine this scenario: a car parked in the sun, with its windows and sunroof conveniently charging the battery; or smart glasses you wear, where the lenses themselves can harvest light and directly power the electronic components within the frame.

These sci-fi-like visions are one step closer to reality, thanks to a new ultra-thin transparent solar cell developed by scientists at Nanyang Technological University, Singapore (NTU Singapore).

Led by Associate Professor Annalisa Bruno, the research team has developed an ultra-thin transparent perovskite solar cell. Its thickness is merely one ten-thousandth of a human hair, making it fifty times thinner than conventional perovskite cells.

More notably, despite the significant reduction in thickness, this cell has achieved a new record in photoelectric conversion efficiency among similar ultra-thin perovskite solar cells to date.

The findings have been published in ACS Energy Letters. Researchers believe that in the future, this technology could be widely applied in buildings, automobiles, and wearable devices with almost no change to their original appearance.

The cell is semi-transparent and neutral in color, allowing it to be embedded in windows or building facades, enabling an entire building to generate electricity with virtually no change in appearance.

"Approximately 40% of global energy consumption comes from the building sector. Therefore, there is an increasingly urgent market demand for technologies that can transform building facades into power-generating carriers," said Associate Professor Bruno from NTU's School of Physical and Mathematical Sciences and School of Materials Science and Engineering.

Professor Bruno, who also directs the Renewable and Low-Carbon Solutions and Energy Storage Clusters at the Energy Research Institute @ NTU (ERI@N), added: "Our perovskite cell has clear advantages: the manufacturing process is simple and can be done at low temperatures. Furthermore, it can be tailored to absorb specific wavelengths of light while maintaining transparency. It also holds the potential for large-area mass production, thereby reducing overall carbon emissions."

Unlike traditional silicon-based solar panels, these perovskite cells can generate electricity even under indirect sunlight and diffuse light conditions. This is particularly suitable for high-density urban environments like Singapore, where numerous high-rise buildings with vertical curtain walls, coupled with frequent cloud cover, often prevent traditional solar panels from fully utilizing sunlight.

The research team cited an example: if scaled up in the future, large-area glass curtain walls would no longer be just building shells but could become urban power stations.

According to preliminary estimates, if this technology were applied to glass-curtain-walled office buildings in areas like Raffles Place or Marina Bay, the theoretical annual electricity generation could reach hundreds of thousands of kilowatt-hours.

The exact amount of electricity generated depends on the glass area and building orientation, but its annual generation capacity could be sufficient to meet the yearly electricity needs of approximately 100 standard four-room HDB flats in Singapore.

Manufacturing Nearly Invisible Solar Cells

Perovskite solar cells are actually composed of multiple layers, with the core being a semiconductor layer that absorbs sunlight and converts it into electricity.

To create this ultra-thin cell, the NTU team employed an industry-compatible fabrication method: thermal evaporation. Simply put, raw materials are heated in a vacuum chamber until they evaporate, then condense and deposit onto a substrate surface, forming an extremely thin film.

The advantage of this method is that it allows for the deposition of a uniform and ultra-thin perovskite layer over large areas. Moreover, the entire process does not require toxic solvents, while also reducing defects within the cell, leading to higher photoelectric conversion efficiency.

By precisely adjusting the process parameters, the researchers successfully controlled the thickness of the perovskite layer and fabricated both opaque and semi-transparent cell devices.

The team stated that this is the world's first ultra-thin perovskite solar cell fabricated entirely using a vacuum process. This means the technology has taken a significant step closer to future large-scale industrial production.

With this technology, the researchers successfully reduced the perovskite absorption layer to just 10 nanometers thick while still maintaining considerable power generation performance.

When the perovskite layer thickness was 10 nm, 30 nm, and 60 nm respectively, the photoelectric conversion efficiency of the opaque cells reached approximately 7%, 11%, and 12%.

A semi-transparent cell with a thickness of 60 nm, while allowing about 41% of visible light to pass through, still achieved a power generation efficiency of 7.6%.

The research team stated that this performance is already among the leading levels for similar semi-transparent perovskite solar cells.

This means that in the future, building windows can maintain natural lighting and a sense of transparency while simultaneously generating electricity. This holds significant implications for solar windows, glass curtain walls, or tinted building facades.

Dr. Luke White, the first author of the paper and a former PhD student at ERI@N, said: "By precisely controlling the thermal evaporation process, researchers have been able to freely adjust the transparency of the solar cell. This opens up new possibilities for green buildings, such as installing tinted windows that can both provide shade and generate electricity."

Professor Sam Stranks, an expert in energy materials and optoelectronics from the Department of Chemical Engineering and Biotechnology at the University of Cambridge, commented as a third-party expert: "This method offers excellent control over film thickness and uniformity, which is precisely a key prerequisite for the future large-area commercialization of semi-transparent solar cells."

"Semi-transparent perovskite cells are an exciting technological pathway, allowing us to harvest energy from places where traditional silicon panels struggle to be effective, such as windows, building facades, and even lightweight electronic devices."

"The current results achieve a good balance between transparency and power output. However, the next step that will truly determine whether the technology can be deployed will be its performance in terms of long-term stability, durability, and large-area application."

Sustaining Urban Energy Supply

Professor Bruno has long been dedicated to the field of perovskite solar cells. Her previous research on thermally evaporated perovskite cells has already begun moving towards industrialization. This has not only advanced the entire industry but also paved the way for future commercial implementation.

Her innovations have also received strong support from NTU's Innovation and Entrepreneurship Initiative. This program aims to help research teams accelerate the transition of cutting-edge technologies from the lab to industrial application.

Currently, the team has filed a patent for this novel ultra-thin perovskite film structure through NTUitive, the university's technology transfer company.

Now, the researchers are engaging with industry partners to validate and standardize the thermal evaporation process used in this study. Before officially bringing it to market, they will continue to improve the cell's long-term stability, durability, and performance in large-area production.

As cities become more crowded and electricity demand grows, buildings are being redefined—they are no longer just energy consumers but potential clean energy producers.

Today, rooftop solar panels are relatively common, but the vertical surfaces of buildings, such as windows and entire glass curtain walls, represent a vast, untapped blue ocean.

This breakthrough marks a critical step towards integrating transparent solar cells into buildings, automobiles, and wearable devices. It also means that future cities could generate more clean electricity on their own without requiring additional land.

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