Windows capable of harvesting energy from the sun have been on the horizon for a number of years, but they’re yet to help cut down a building’s energy costs. A new development from Australian researchers may change that. The semi-transparent solar cells have been produced by researchers from Monash University and CSIRO (Australia’s national science agency), and led by members of the ARC Centre of Excellence in Exciton Science. The cells make use of perovskite, which can efficiently convert ultraviolet and visible light into electricity, and feature an organic semiconductor that replaces a hole-transport material known as Spiro-OMeTAD for improved stability. And the design is said to have resulted in a conversion efficiency to rival rooftop solar too. “Rooftop solar has a conversion efficiency of between 15 and 20 percent,” said Professor Jacek Jasieniak of Exciton Science and Monash University. “The semi-transparent cells have a conversion efficiency of 17 percent, while still transmitting more than 10 percent 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.” The researchers say that windows tinted to the same level as current commercial glazing could generate around 140 watts of electricity per square meter. And they reckon that the additional costs of implementing the technology into the kinds of large windows used in multi-story buildings would be marginal. “But even with the extra spend, the building then gets its electricity free,” added Jasieniak. The team is now looking at incorporating the technology into commercial products together with Australia’s largest glass manufacturer, Viridian Glass. “The development of such solar windows presents an opportunity that could translate into the new glass innovations and technologies going forward,” said the company’s Jatin Khanna. Though it could be up to 10 years before we see the first commercial application, depending on how well the technology scales up. But lead author on the study Dr. Jae Choul Yu is already looking to improve on the conversion efficiency in a new design. “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.” And as we saw recently, tandem solar cells can be very efficient. A paper on the research will be published next month in the journal Nano Energy, but an early release is available online.