Your Next Solar Panel Could Be the Window You Look Through

Most windows spend their lives doing a fairly modest job: keeping the weather outside while letting you see through the wall.

Researchers want to give them another one—making electricity.

A study highlighted by University College London on 17 July 2026 shows why that idea is gaining attention. The team developed semi-transparent solar devices that work under sunlight and indoor lighting. These are research devices, not a new window range ready to order, but they point towards a building whose glass does more than frame the view. UCL’s research announcement explains the concept.

How can a window be a solar panel?

A conventional dark solar panel is designed to absorb light. A useful window must let some light pass through. Combining the two means deciding how much electricity to generate and how much view to preserve.

The material at the heart of this research is a perovskite: a member of a family of materials with a particular crystal structure. In solar cells, an extremely thin absorbing layer can use light to release electrical charges, which neighbouring layers collect as current. The US Department of Energy describes these thin films as a promising alternative or addition to familiar silicon technology. Source: DOE’s perovskite overview.

In this study, the researchers made the absorbing layer just 185 nanometres thick and improved how the surrounding layers handled light and electrical charge. UCL says the devices transmit roughly 30% of visible light, compared with around 80–90% for ordinary glass. Think tinted glazing, rather than an invisible coating that leaves the view completely unchanged. Source: UCL.

Solar window efficiency: small cells versus larger panels

The peer-reviewed paper in Advanced Energy Materials, first published on 4 January 2026, reports a best small-cell efficiency of 13.78% under simulated sunlight, with 31.1% average visible-light transmission.

Under 1,000-lux LED illumination, a small cell reached 22.41% efficiency. That higher percentage does not mean an office light produces more electricity than the Sun. It describes the fraction of incoming light energy converted; indoor lighting supplies much less energy in the first place.

The team also built a 30-by-30-centimetre module. Its efficiency under standard simulated sunlight was 8.2%. That is the figure to remember when thinking about the larger demonstration—not the small cell’s 13.78% or its indoor result.

Scaling up changes the outcome. A promising square of material and a useful pane of building glass are separate engineering achievements.

No, leaving the lights on will not power your home

Harvesting indoor light could be useful for small, low-power electronics. It is not a reason to keep a room illuminated.

If electricity powers a lamp, and a solar device then recovers some of that lamp’s light, energy is lost at each stage. The panel recycles a fraction of energy already supplied; it does not create a self-powering loop.

The stronger architectural idea is to capture daylight across surfaces that buildings already need. For a tall building with limited roof space, its walls offer an obvious area to investigate. Whether this makes economic sense depends on the actual installation, not just a laboratory efficiency percentage.

Solar window durability: the challenge beyond the lab

The paper reports that an unencapsulated device retained about 80% of its initial efficiency after 268 hours of continuous light exposure. That is useful experimental evidence, but it is not a demonstration of decades of service outdoors. Source: the original study.

Commercial glazing would also need reliable sealing, electrical connections, predictable colour and manufacturing quality. Buyers need to know what happens after years of heat, moisture and repeated temperature changes. DOE identifies durability, performance at scale, manufacturing and independent validation as central challenges for perovskite technology. Source: DOE.

The exciting possibility is not a skyscraper magically running on its own reflection. It is something more practical: giving a large, already necessary part of a building a second job. The next decisive result will be a window that keeps both jobs for years.