A UK-based company is developing solar-cell technology that could help advance the market for integrating solar energy-harvesting glass into commercial buildings.
Oxford Photovoltaics (PV) -- co-founded by Oxford University physicist Henry Snaith -- is using a material called perovskite to develop thin-film solar cells that can be printed directly onto glass to be used as semi-transparent, solar-energy harvesting material in large buildings. This potentially new market for solar cells -- the so-called building integrated photovoltaic, or BIP, market -- is in its nascent stages, but is poised to become a key commercial use of solar energy in the future.
"Once integrated in a glass-clad building, the technology is capable of powering much of the building's lighting and IT infrastructure using solar power," Ed Crossland, a senior development scientist at Oxford Photovoltaics, told Design News.
Using perovskite -- a calcium titanium oxide mineral composed of calcium titanate -- in the production of these cells has several advantages over other silicon-based thin-film cells, including higher efficiency and less cost in cell production. "The remarkable fact is that despite being so easy to manufacture, the solar-harvesting properties of perovskite films compare very favorably to other PV technologies, which require more expensive and energy-intensive manufacture," Crossland told us. "The perovskite is a very strong absorber of light in the solar spectrum. High-charge mobility means that electronic charges can move quickly to the cell terminals, and the material tends to minimize the energy loss inside the cell. Put simply, the perovskite is a very strong absorber of sunlight, and electronic charges generated inside the cell are very efficiently collected at the cell terminals to give useful power out."
The current material sets and design of Oxford PV's cells have already taken power conversion efficiencies to above 16%, which Crossland said is "significantly ahead" of amorphous silicon, which has a 12% efficiency. This percentage also has perovskite-based cells closing in on other thin-film technologies like Cadmium telluride, or CDTe, which is currently at 17% efficiency, and Copper indium gallium (di)selenide, or CIGS, which has 20% efficiency. "With further material development and design optimization, single-layer perovskite solar cells will deliver efficiencies above 20%," Crossland said.
To produce the cells, the company applies a wet coating of the perovskite-based material onto architectural glass, and then seals it with another sheet of glass to protect it. Oxford PV is licensing this process and technology to third parties to produce the cells and plans to demonstrate samples from its first licensees in about two years. Following that, volume production of the cells should begin in 2017, Crossland told us.
The company initially is targeting the commercial sector with its technology, where the potential for use of thin-film solar cells is greatest.
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