Solar cells absorb light and screens emit light. Scientists at Nanyang Technological University (NTU) in Singapore have developed a material that does both. This new material — based on perovskite, a mineral first discovered in 19th century Russia — absorbs sunlight and glows when electricity passes through it.
The discovery came when assistant professor Sum Tze Chien and a team of physicists were working on a new type of solar cell. He asked postdoctoral researcher Xing Guichuan to shine a laser on the material and, to their surprise, it glowed.
“What we have discovered,” said Sum in a press release, “is that because it is a high quality material, and very durable under light exposure, it can capture light particles and convert them to electricity, or vice versa.” It could be a viable replacement for the silicon-based solar cells in use now, making possible a new breed of electronic devices and lighting displays.
Silicon versus perovskite solar cells
Crystalline silicon comprises over 85 percent of photovoltaic materials used in solar panels today. Yet silicon is not an efficient conductor of electricity, converting less than 15 percent of captured solar energy into watt hours. It is also bulky and expensive.
Perovskite may provide an alternative. It is a type of mineral defined by a particular crystal structure. Its use as solar cell material was first reported in 2009, though it had low efficiency and could only be used in liquid form. Scientists at Oxford University discovered 18 months later how to make solid perovskite solar cells, improving efficiency levels to nearly 20 percent.
The mineral was still poorly understood until last October, when the same NTU researchers became the first to explain its properties. They discovered that its crystalline structure caused electrons generated by sunlight to travel a long way within the material, producing electricity more efficiently per mass and purity than silicon.
Building silicon-based solar cells is costly and energy intensive, due to the high degree of purity required for them to function. The material developed at NTU, meanwhile, is created through a relatively simple manufacturingprocess. A commercially available form of perovskite will be five times cheaper than silicon cells.
Screens that charge by day, glow by night
Adoption of the material would be a huge step forward in developing green buildings, says Nripan Mathews, also an assistant professor at NTU.
“Since we are already working on the scaling up of these materials for large-scale solar cells,” he told Gizmag, “it is pretty straightforward to modify the procedures to fabricate light emitting devices as well.” Perovskite can be made semi-transparent, so cells based on it are also more suitable than silicon cells for incorporating into windows and roofing materials. The material is also lightweight enough that it could conceivably be incorporated into fabric or wearable devices.
The light-emitting properties of the new material give it a variety of potential uses beyond traditional solar cells. It can be made to give off a wide range of colors by adjusting its composition, opening up the possibility of glowing signs or touch screens that double as solar panels.
Mathews predicts it could be useful in light decorations, building facades or advertising displays that collect energy during the day and come alive at night. Simply exposing the screen to sunlight could recharge cell phones with perovskite screens.
Perovskite is an excellent material for lasers, as well, with the Oxford scientists making significant advances in using it to convert electricity into light.