Transparent solar cells turn windows into power sources
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Transparent solar cells could be mounted right on windows
By Etiido Uko
May 26, 2026
Transparent solar cells could be mounted right on windows
Assoc. Prof. Annalisa Bruno examines one of the ultrathin perovskite solar cells, which is just 10 nanometers thick<br>NTU Singapore
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From left: NTU scientists, Dr. Herlina A. Dewi; Assoc. Prof. Annalisa Bruno; Mr. Edoardo Albanesi; and Dr. Daniela De Luca<br>NTU Singapore
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Assoc. Prof. Annalisa Bruno examines one of the ultrathin perovskite solar cells, which is just 10 nanometers thick<br>NTU Singapore
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NTU research fellow Dr. Daniela De Luca examining a prototype ultrathin perovskite solar cell in the vacuum chamber in the lab<br>NTU Singapore
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One of the hindrances to large-scale solar adoption, especially in cities, is where to install the chunky panels. Rooftops? Skyscraper walls? Vast open spaces that dense urban centers barely have in the first place? Researchers from Nanyang Technological University (NTU) Singapore say they may have solved part of this problem with solar cells so thin they are invisible enough to install directly onto windows.<br>The team claims to have developed ultrathin, semi-transparent perovskite solar cells that are roughly 10,000 times thinner than a strand of human hair and about 50 times thinner than conventional perovskite solar cells, while still retaining some of the highest efficiencies yet reported for devices in this ultrathin category.<br>Their work, recently published in ACS Energy Letters, could eventually pave the way for electricity-generating windows, glass facades, smart glasses, vehicle sunroofs, and other surfaces that currently sit passively in the sunlight.<br>The idea of transparent solar cells is not entirely new. Researchers around the world have spent years trying to create photovoltaics that can blend into glass and urban infrastructure. The problem is that solar panels are fundamentally designed to absorb sunlight. The more light a solar cell captures, the less transparent it tends to become.<br>Existing commercial solar panels are also physically bulky systems consisting not just of photovoltaic materials but also of thick protective glass, encapsulation layers, metallic contacts, mounting hardware, and structural framing. Typical residential solar panels weigh around 18 to 23 kg (40 to 50 lb) each and generate roughly 350 to 450 W of power under ideal conditions.<br>A modern office tower can easily consume several gigawatt-hours of electricity annually. Now, imagine the sheer amount and weight of solar panels powering such a building independently. Where could they possibly be mounted? In this context, the roofs appear ridiculously small. An alternative would be vast open land, but many cities simply do not have it.<br>What of the walls, you ask? They are everywhere and in abundance. Well, mounting heavy opaque panels across glass skyscraper facades radically changes the appearance, weight, and thermal characteristics of the building itself. But what if they didn’t have to be heavy, or bulky, or even visible at all?<br>These questions form the basis of NTU researchers’ technology aimed at turning glass surfaces that already dominate modern cities into active power-generating systems.<br>The team, led by Associate Professor Annalisa Bruno from NTU’s School of Physical and Mathematical Sciences and School of Materials Science and Engineering, developed the new devices using perovskites: a class of crystalline materials that have become one of the hottest areas in solar research over the last decade due to their potentially low manufacturing costs, high efficiencies, and ability to function under lower-light conditions.
From left: NTU scientists, Dr. Herlina A. Dewi; Assoc. Prof. Annalisa Bruno; Mr. Edoardo Albanesi; and Dr. Daniela De LucaNTU Singapore
The researchers fabricated ultrathin perovskite absorber layers measuring just 10 nanometers thick while still retaining useful photovoltaic performance. For perspective, a human hair is typically around 80,000 to 100,000 nanometers thick.<br>Unlike conventional silicon solar cells, which perform best under direct sunlight, perovskite-based devices can continue generating electricity even under indirect or diffuse lighting conditions. That is particularly relevant in high-rise cities, where skyscrapers create heavily shaded urban canyons and cloud cover frequently reduces direct solar exposure. Instead of relying solely on rooftops facing the sun, vertical glass surfaces across entire city blocks could theoretically generate power throughout the day.<br>The researchers tested multiple thicknesses. Opaque devices with 10-, 30-, and 60-nanometer perovskite layers achieved power conversion...