Electricity-generating windows follow solar cell breakthrough

Australian researchers have revealed that 2 m² of solar window will generate the same amount of power as a standard rooftop solar panel.

Semitransparent solar cells incorporated into window glass have been tipped by Australian scientists as a game changer that could transform architecture, urban planning and electricity generation, as outlined in a paper published in Nano Energy.

Led by Professor Jacek Jasieniak from the ARC Centre of Excellence in Exciton Science (Exciton Science) and Monash University, the researchers have produced next-generation perovskite solar cells that generate electricity while allowing light to pass through. The team is now investigating how the technology could be built into commercial products with Australian glass manufacturer Viridian Glass.

The idea of semitransparent solar cells is not new, but previous designs have failed because they were very expensive, unstable or inefficient. Professor Jasieniak and colleagues from Monash’s Materials Science and Engineering Department and Australia’s national science agency, CSIRO, used a different approach.

Using an organic semiconductor that can be made into a polymer, the team replaced a commonly used solar cell component known as Spiro-OMeTAD, which shows very low stability because it develops an unhelpful watery coating. The substitute produced astonishing results.

“Rooftop solar has a conversion efficiency of between 15 and 20%,” Professor Jacek said. “The semitransparent cells have a conversion efficiency of 17%, while still transmitting more than 10% of the incoming light, so they are right in the zone. It’s long been a dream to have windows that generate electricity, and now that looks possible.”

Co-author and CSIRO research scientist Dr Anthony Chesman said the team is now working on scaling up the manufacturing process.

“We’ll be looking to develop a large-scale glass manufacturing process that can be easily transferred to industry so manufacturers can readily uptake the technology,” he said.

Professor Jasieniak explained that there is a trade-off: “The solar cells can be made more, or less, transparent. The more transparent they are, the less electricity they generate, so that becomes something for architects to consider,” he said.

He added that solar windows tinted to the same degree as current glazed commercial windows would generate about 140 watts of electricity per square metre.

The first application is likely to be in multistorey buildings. Large windows deployed in high-rise buildings are expensive to make. The additional cost of incorporating the semitransparent solar cells into them will be marginal.

“But even with the extra spend, the building then gets its electricity free!” Professor Jasieniak said.

“These solar cells mean a big change to the way we think about buildings and the way they function. Up until now, every building has been designed on the assumption that windows are fundamentally passive. Now they will actively produce electricity.

“Planners and designers might have to even reconsider how they position buildings on sites, to optimise how the walls catch the sun.”

Lead author Dr Jae Choul Yu, also from Exciton Science and Monash, added that more efficiency gains would flow from further research.

“Our next project is a tandem device,” he said. “We will use perovskite solar cells as the bottom layer and organic solar cells as the top one.”

As to when the first commercial semitransparent solar cells will be on the market, Professor Jasieniak explained that it will depend on the success of scaling the technology.

“We are aiming to get there within 10 years,” he said.

Image caption: A semitransparent perovskite solar cell with contrasting levels of light transparency. Image credit: Dr Jae Choul Yu.