Persistent luminescence materials are used in everyday glow-in-the-dark applications and show high potential for medical imaging, night-vision surveillance and enhancement of solar cells. The materials that make these applications possible contain rare earths and heavy metals that are expensive. Researchers at the University of Turku in Finland have developed a low-cost synthetic material that emits luminescence closer to sunlight than that of the currently used lanthanides. The hackmanite developed by researchers at the University of Turku. Courtesy of University of Turku. The synthetic material is based on the natural hackmanite mineral that produces broad spectrum white light in lamps; it uses only highly abundant and nontoxic elements, lowering production costs and reducing health risks. “Because of its persistent luminescence, hackmanite does not require expensive time-resolved spectrometers to measure luminescence,” said Mika Lastusaari from the University of Turku. Lamps that produce white light imitating sunlight are used in lighting applications. At the moment, fluorescent lamps and LEDs produce white light with luminescent materials that contain lanthanides. White light is produced with lanthanides by mixing three narrow spectrum primary colors — red, green and blue — making things look different in their light than in the sunshine. Until now, there have been no materials that produce good white persistent luminescence. “Our hackmanite material can produce observable white persistent luminescence for seven hours in the dark. With a spectrometer, the luminescence can be detected for more than 100 hours," said Lastusaari. He said their material can be used in ordinary lamps to produce natural white light, and in the event of a power outage they will glow, making them suitable for exit and emergency signs. The research has been published in the journal Advanced Functional Materials (doi: 10.1002/adfm.201606547).