The 1999 Australia Prize was awarded to Martin Green and Stuart Wenham
for their work in photovoltaics
Martin Green and Stuart Wenham, from the University of New South Wales, have invented or co-invented seven distinct cell technologies over the past 15 years. These solar cells have held the world efficiency record for converting sunlight into electricity for more than a decade and last year achieved an efficiency of 24.5 per cent, the current world record by a large margin.
The awarding of the 1999 Australia Prize in Energy Science and Technology to Martin Green and Stuart Wenham represents only the second time in the 10 year history of the Prize that it’s been won by an all-Australian team – an indication of the pair’s dominance in the world of photovoltaic research.
There is more information about the winners and their research at the ABC's The Lab.
Read on to find out how photovoltaic cells work.
Photovoltaic cells convert light directly into electricity. It has been known for more than 150 years that light can have an effect on the electrical properties of some materials. This is known as the photoelectric effect. In 1921, Einstein received the Nobel prize for his work explaining this. Photovoltaic cells are based on a related phenomenon called the photovoltaic effect, and interest in this has increased greatly during this century. The generation of electricity from light relies upon the separation of positive and negative electric charges – electrons and positively charged 'holes', both generated by the light – at the junction between two parts of a semiconductor crystal. Silicon is a semiconductor that can be mixed with tiny quantities of impurities (such as phosphorus and boron) in a process called doping. Doping can produce P (for positive) and N (for negative) materials. A photovoltaic cell is simply a wafer of semiconductor in which there is a junction between N and P materials. On exposure to light, a photovoltaic cell produces a voltage of about 1 volt, comparable with that of a torch battery. The silicon, which is expensive to make in pure form, is in the form of a thin wafer, to catch as much light as possible. The ultimate efficiency of a silicon photovoltaic cell in converting sunlight to electrical energy is less than 30 per cent, and the Photovoltaic Research Centre at the University of New South Wales holds the present world record with a cell efficiency of about 25 per cent. But cells like this, made from single-crystal silicon, are expensive, and large areas of them are needed to produce useful amounts of power. The search is therefore on for much cheaper cells without too much sacrifice in efficiency. In 1997 the National Australia Day Council acknowledged the importance of this work when it named Professor Martin Green, Director of the Photovoltaic Special Research Centre, as an Australian Achiever. Several promising lines are being pursued by the University of New South Wales and by Pacific Solar, a joint company formed by the University and Pacific Power, the major New South Wales electricity supply authority. Instead of cutting slices from specially grown silicon single crystals, one possibility involves growing thin films of silicon on much cheaper polycrystalline silicon wafers; another involves evaporating thin films of silicon onto glass plates. Initial results for both of these techniques are very encouraging, and the efficiency is already approaching 20 per cent. Another approach is to use amorphous (glassy) silicon (which can be produced fairly cheaply) instead of crystalline material. While expensive photovoltaic cells can be used in solar car races, and solar photovoltaic modules on the roofs of houses may also become common, the ultimate aim of photovoltaic technology is to produce large amounts of electrical power from cheap photovoltaic cells, connected together to give a high voltage, and to convert this to alternating current to feed into the power grid. This has already been done on an experimental scale in Sydney, and Australia is a leader in the race. Related sites
Other boxes Box 5. Chemical fuels from the sun
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Page updated September 2003.
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