Alta Devices, named as one of America’s top performing solar start-up companies of 2011, has achieved a new record sunlight conversion efficiency of 23.5 percent with its most recent solar panel; a result verified by the National Renewable Energy Laboratory (NREL).
Alta produced the new panel using the same solar cell technology as the company announced last year, which achieved record solar cell conversion efficiencies of 28.2 percent. The theoretical maximum solar cell efficiency limit (called the "Shockley-Queisser Limit") for a single junction device has been shown to be 33.5%.
The company says that by harnessing the high efficiency characteristics of the solar material gallium arsenide (GaAs) – which has the ability to generate electricity at high temperatures and in low light conditions – it hopes to push the boundaries of solar power to the point where it can compete, without subsidies, with fossil fuels.
The major drawback with GaAs, according to Alta, is not the energy conversion potential, but the cost. Compared to silicon-based solar panels that enjoy worldwide market dominance due to cheap manufacturing techniques and plentiful supply of materials, gallium arsenide is a rare and precious substance, and expensive to apply for mass-production.
To address this challenge, Alta pioneered a manufacturing technique which produces extremely thin slivers of GaA material that are a fraction of the thickness of earlier GaAs solar cells. The example used in a company statement is of cells about one micron thick – a human hair is approximately 40 microns thick.
This technique results in a very thin, flexible solar panel, capable of producing the highest energy density possible, while the cost of the materials remains low and the potential costs of an entire solar power system based on Alta’s technology could be dramatically reduced.
Alta says that, unlike traditional solar panels, the density and strength of GaAs panels means they could be integrated into building materials and utilised in military and transport applications.
