Martin Green and His Fellow Scientists Silicon Nature, but Must Be Extracted from Other Substances and Processed in a Factory

Specialising in microelectronics MMarartintin GGreereenn After completing his engineering degree, Martin travelled to Canada to study for a PhD. On his first day at McMaster University, in 1971, he was shown experiments using the semiconductor silicon. Martin was struck with curiosity about how the silicon in these experiments semiconductors Breaking world could turn sunlight into electricity, but at first he concentrated on other materials that sometimes allow aspects of semiconductors. By the time he had finished his PhD, he was a electricity to pass specialist in microelectronics, a branch of physics which concentrates on through them, and records with the tiny electrical parts inside appliances, such as radios, telephones and sometimes stop computers. These parts are often made with semiconductors. solarcells electricity from flowing

Silicon is a hard, dark grey, shiny material. olar cells turn sunlight into electricity. It does not occur in a pure form in Martin Green and his fellow scientists Silicon nature, but must be extracted from other substances and processed in a factory. Sat the University of New South Wales Some materials, including many metals and are famous for inventing new types of water, allow electricity to pass through them solar cells made from silicon, the most easily, but others, such as plastic, rubber or commonly used material for making solar glass, do not allow electricity to pass through cells. For more than 20 years, Martin and easily. Materials that allow electricity to pass through easily are called his team have held the world record for Martin is internationally recognised conductors, while those that for his work on silicon solar cells. the amount of energy in sunlight that a don’t are called insulators. Billions of the solar cells he has silicon solar cell can turn into electricity. invented have been manufactured Materials in between in factories around the world. conductors and insulators are called semiconductors. They Switched on to electricity are widely used for making electrical appliances because Martin Andrew Green was born in Brisbane. As scientists can treat them in a young boy, he always did well at school, but certain ways to control how well Born: 20 July 1948 especially liked playing Rugby League football. At electricity passes through them. Schooling: (Queensland) Coorparoo secondary school, he took study more seriously. A Some semiconductors are useful for State School, Brisbane State High physics teacher, who conducted experiments about making solar cells because they strongly School electricity, particularly inspired him. In his final year absorb light. Selected achievements: exams, Martin was awarded the Lilley Medal for Silicon is the most commonly used Australian Museum Eureka Prizes, gaining the highest marks in Queensland. 1991, 2010 semiconductor material in today’s electrical appliances, and it is used to Australia Prize (shared), 1999 Studying semiconductors make most solar cells. Right Livelihood Award, 2002 Martin began studying electrical engineering at the World Technology Award for Energy, University of Queensland in 1966. He most enjoyed 2004 his hardest subject – the physics of materials such as silicon, which are called semiconductors .

8 9 Starting in solar research Inventing the ‘buried contact solar cell’ In 1973, an oil crisis caused petrol shortages in many countries of the world. In 1983, Martin started working with Stuart Wenham, who had previously The Australian Government began looking for alternative ways to generate been working as a scientist for a business making silicon solar cells. Martin and energy. It started supporting research into renewable forms of energy, such Stuart invented a new type of cell, called the ‘buried contact solar cell’. Like as solar energy, which created new jobs for scientists. Martin began research earlier cells, it is made by slicing a block of solid silicon into ‘wafers’, but in into solar energy at the University of New South Wales (UNSW) in 1974. this cell the wafer has metal contacts ‘buried’ into it, rather than sitting on top of it. This increases the amount of electricity the cell produces. A new theory on solar cells The first main use of silicon solar cells, in the 1950s, was to power spacecraft. Then, in the 1960s and 1970s, companies began to manufacture silicon solar cells for use on Earth. At the time when Martin started at UNSW, scientists believed 20 per cent of the Sun’s energy was the most a cell could ever change into electricity. According to the laws of physics, the remaining energy would have to be reflected, or lost as heat. Silicon solar cells An early achievement of Martin’s was to work out that if a particular In a silicon solar cell, sunlight is turned into electricity. The famous scientist loss of energy in the cell was avoided, it might eventually be possible, Albert Einstein solved the mystery of how this occurred when he showed that in theory, to make a cell that changed 30 per cent of the Sun’s energy light is made up of packets of energy, now called photons. into electricity. The amount of solar In a silicon solar cell, the energy of photons is absorbed and turned into energy that reaches electricity inside a layer of silicon. The silicon has been specially treated to make it easier for electricity to flow. When the cell is connected by metal wires to an Australia in one summer electrical device, such as a lightbulb or washing machine, the electricity flows day is about the same out of it through metal contacts. amount of energy used by everyone on Earth Solar cells can be connected to each other to provide more electricity. Large over six months. groupings of thousands of cells can be used to make a power plant. Smaller groupings, called solar panels, are often found on rooftops. Strips of just a few cells are used to power household objects such as toys, calculators or radios.

Solar cells can be used In a silicon solar cell, sunlight to power calculators, changes into electricity inside a or provide energy for a layer of specially treated silicon. home. As part of a large Cells can be connected to each power plant they can other to provide more electricity. generate much more electricity. In space, they ﬂow of electricity power satellites. photons

glass layer protecting cell

specially treated silicon front metal contacts

roughened silicon surface – the sides of the tiny pyramid shapes back metal reﬂect light down into the cell contacts

10 11 12 processing. and undergo careful to ahightemperature silica mustbeheated used insolarcells, obtain thepure silicon silica andsilicate.To of substancescalled with oxygenaspart it isalwayscombined a pure form.Instead, rocks, butitisneverin sand, soilandnearlyall in nature, occurringin Silicon iseasytofind Si l i con producing siliconforsolar cellsisexpensive. vapour ismadesolidbyheatinginafurnace. sheet withanextremely thinlayerofsilicon,intheformavapour.The being madebycuttingupsolidsilicon,thiscelliscoatingaglass Martin’s teamstartedtodevelopanewtypeofsolarcellin1988.Instead of D break manyfurtherrecords. changed 18percentoftheSun’s energy intoelectricity, andtheywentonto 1983, theyhadbecomethefirstinworldtomakeasiliconsolarcellthat Meanwhile, Martin’s teamwasbreaking worldrecords forsiliconsolarcells.In the worldbeganmanufacturingit. Stuart lodgedapatentfortheburiedcontactsolarcell.Companiesaround In 1984,through theUniversityofNewSouthWales (UNSW),Martinand S ales successandworldrecords eveloping silicon-on-glasscells the energy. Theymaybecomemore commoninthefuture, because These ‘silicon-on-glass’cellsuselessthanonehundredth theamount Percentage of the Sun’s energy turned of siliconthatwafercellsuse,buttheyproduce more thanhalf

efficiency almostcontinuously since1983. the worldrecord forsilicon solarcell Martin andscientistsatUNSW haveheld into electricity in a silicon solar cell % 10 15 20 25 1940 0 5 1950 9017 1980 1970 1960 Year Martin’s teamatUNSW World record heldby by otherscientists World record held 9020 2010 2000 1990 KEY energy insunlightintoelectricity. one dayitmaybepossibletomakesolarcellsthatturn74percentofthe nanotechnology tocontinueimprove solarcells.Martinnowbelievesthat around theworldtostudythiscourseandworkwithMartin.Histeamisusing focused entirely onsolarenergy engineering.Today, scientistscomefrom At UNSW, MartinhelpedStuartestablishtheworld’s firstuniversitycourse C world’s biggestmanufacturer ofsiliconsolarcells. Zhengrong, becameabillionaire byfoundingSuntechPower, the expertise tostartmanufacturingbusinesses.Onescientist,Shi have inventednewtypesofsolarcells.Othersusedtheir make importantcontributionstothesolarpowerindustry. Some Many scientistswhohavetrainedwithMartingoneonto An influentialteacher ontinuing toimprove solar cells and easierto harnessrenewable energy from the Sun. continue todevelopeven bettercellstomakeitcheaper some ofthebestsilicon solarcellsintheworld.They on siliconsolarcells.His teamatUNSWhasdeveloped Martin Green isinternationallyrecognised forhiswork to sustainable energy Martin’s contribution 7 October2008 at theAustralianAcademyofScience, Power source forthefuture?’, talkgiven – MartinGreen, ‘Solarphotovoltaics: Gladwrap. that canberolled outlike we willdevelop asolarcell The hopeisthatoneday osmr/video.htm business.nsw.gov.au/media/ and MedicalResearch: ww3. Wales OfficeforScience made bytheNewSouth his workinthisvideoclip Watch Martintalkabout invented atUNSW. the raceusedacell car butonethatwon 1990 to1999,every and Adelaide.From between Darwin 3021 kilometres cars, runover for solar-powered Challenge isarace The World Solar 13