Advances in solar cell and low-energy lighting technologies have led to a variety of new net-zero lighting applications. Simone Giostra's GreenPix zero-energy media wall and Meidad Marzan's UrbanTile solar-powered high-rise envelope, for example, allow buildings to deliver nocturnal illumination and information at no additional energy cost, demonstrating the synergistic combination of the two capabilities.
But both of these ideas use separate technology for light harvesting and transmission. Scientists at Singapore's Nanyang Technological University (NTU), however, recently discovered the potential for harvesting and emission to exist within a single material. According to a university news release, the NTU researchers stumbled upon the finding while shining a laser on a new solar cell they made from perovskite—a mineral made of calcium titanate, an ore reduced to titanium or ferrotitanium alloy—to find that it luminesced brightly in response. This material has been used in solar cells before, but, to my knowledge, it has not been used to both generate light and harness energy.
"What we have discovered 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," said Sum Tze Chien, an assistant professor at NTU's School of Physical and Mathematical Sciences, in the release. "By tuning the composition of the material, we can make it emit a wide range of colours, which also makes it suitable as a light emitting device, such as flat screen displays." Not only does the new perovskite cell technology harness and emit light, but its translucency could lead to further applications. The NTU researchers imagine it as a replacement to conventional window glass, capable of generating electricity while allowing views during the day and delivering multicolored illumination at night.
The dual capability of harnessing and emitting is what makes this so unique. MIT researchers have developed a transparent electronics display, but it does not harness energy. Another technology, the Starpath surfacing product, harnesses energy and emits light within the same material because it is photoluminescent; however, the harnessed energy can only be used for this purpose, and the process cannot be reversed.
"Such a versatile yet low-cost material would be a boon for green buildings," said Nripan Mathews, an assistant professor at NTU's School of Materials Science and Engineering. "Since we are already working on the scaling up of these materials for large-scale solar cells, it is pretty straightforward to modify the procedures to fabricate light emitting devices as well. More significantly, the ability of this material to lase has implications for on-chip electronic devices that source, detect, and control light."
The likely application for this technology would be a replacement window or skylight. The multifunctional capabilities, coupled with the diminishing cost, are compelling. However, perovskite does include a small amount of toxic lead, thus complicating manufacture and recycling.
Blaine Brownell, AIA, is a regularly featured columnist whose stories appear on this website each week. His views and conclusions are not necessarily those of ARCHITECT magazine nor of the American Institute of Architects.
