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Seeing the Light
The inventors developed solar cells with the highest efficiency ever achieved. They also invented a method for increasing the concentration of light sent to solar cells.
The innovation of Buried Contact Solar Cell by Australians Martin Green and Stuart Wenham may play an important role as the world develops alternative energy sources. Discovered at the University of New South Wales (EP156366, patent published on March 25, 1992), the inventors formed Unisearch (later renamed NewSouth Innovations) to exploit the discovery’s commercial potential.
The key innovation in this patent is that a series of contacts is formed not directly on the front surface of the solar cells – as had been done previously – but in a groove, going deep into the substrate of the cell. Green and Stuart found this greatly increased the contact surface compared to a non-buried contact. More light was trapped using this method, creating an increase in the energy conversion efficiency of the solar cell.
The second patent by Green and Wenham is Optical Design For Photo-Cell (EP607251, patent published on December 27, 2000) which is concerned with the concentration of light sent to solar cells.
The inventors created a light guide for solar cells that traps the incoming light and does not allow it to leave the device. As light enters from outside, it is internally reflected many times on the surfaces of the device, irrespective of the angle at which the light enters. This process increases energy production from the solar cells.
The two innovations have very different stories when it comes to commercial
Optical Design For Photo-Cell reached the stage of advanced prototypes but has not yet been used commercially. The first problem was that the invention required solar cells that responded to light falling on both sides, and such cells were not being produced in volume at the time. The second issue was money: No cost-effective method of producing the optical elements had been devised.
The same cannot be said for Buried Contact Solar Cell, which was famously used in the 1990 World Solar Challenge, a solar car race across Australia. The winning car was powered by cells created using Green and Wenham’s patent.
The profile of the patent continued to grow when in 1994 BP Solar used the cells in what was then Europe's largest solar system, in Toledo, Spain. “The skills and technology extensions we have developed around the processes used for the buried contact solar cell provide a solid foundation for our future generation technologies,” said a spokesperson for BP Solar. “The buried contact cell technology enabled us to develop a leading high efficiency cell process.”
For their work in photovoltaics/solar cells Martin Green and Stuart Wenham won the 1999 Australia Prize – the country’s most prestigious science award. Both inventors are still closely linked to the University of New South Wales, with Green acting as director of the university’s photovoltaics special research centre, and Wenham director of the centre of excellence for advanced photovoltaics.
Wenham spent nine years as the co-director of Research at Pacific Solar Pty where Green – author of four books on solar cells – is currently a research director.
It may be decades before the world has to be powered by solar, but if that time comes, two men from Australia may become household names.