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EETE SEP 2014

ENERGY HARVESTING Spray-on solar cells reduce solar power costs By Paul Buckley A team of scientists at the University of Sheffield are claiming to be the first to fabricate perovskite solar cells using a spray-painting process which could help cut the cost of solar electricity. Experts from Sheffield Universitys Department of Physics and Astronomy and Department of Chemical and Biological Engineering have previously used the spraypainting method to produce solar cells using organic semiconductors - but using perovskite is a major step forward. Efficient organometal halide perovskite based photovoltaics were first demonstrated in 2012. They are now a promising new material for solar cells as they combine high efficiency with low materials costs. The spray-painting process wastes little of the perovskite material and can be scaled to high volume manufacturing similar to applying paint to cars and graphic printing. Lead researcher Professor David Lidzey said: There is a lot of excitement around perovskite based photovoltaics. Remarkably, this class of material offers the potential to combine the high performance of mature solar cell technologies with the low embedded energy costs of production of organic photovoltaics. While most solar cells are manufactured using energy intensive materials like silicon, perovskites, by comparison, requires much less energy to make. By spray-painting the perovskite layer in air the team hope the overall energy used to make a solar cell can be reduced further. Professor Lidzey said: The best certified efficiencies from organic solar cells are around 10 per cent. Perovskite cells now have efficiencies of up to 19 per cent. This is not so far behind that of silicon at 25 per cent - the material that dominates the worldwide solar market. The perovskite devices we have created still use similar structures to organic cells. What we have done is replace the key light absorbing layer - the organic layer - with a spray-painted perovskite.” Using a perovskite absorber instead of an organic absorber gives a significant boost in terms of efficiency. The Sheffield team found that by spray-painting the perovskite they could make prototype solar cells with efficiency of up to 11 per cent. Professor Lidzey said: This study advances existing work where the perovskite layer has been deposited from solution using laboratory scale techniques. Its a significant step towards efficient, low-cost solar cell devices made using high volume roll-to-roll processing methods. Tattoo biobatteries produce power from sweat By Paul Buckley Researchers University of California San Diego have designed a sensor in the form of a temporary tattoo that can both monitor a person’s progress during exercise and the tattoo biobatteries can also produce power from the perspiration. The research team described their work at the 248th National Meeting & Exposition of the American Chemical Society (ACS). The device works by detecting and responding to lactate, which is naturally present in sweat. Lactate is a very important indicator of how you are doing during exercise, explained Wenzhao Jia, Ph.D. In general, the more intense the exercise, the more lactate the body produces. During strenuous physical activity, the body needs to generate more energy, so it activates a process called glycolysis. Glycolysis produces energy and lactate, the latter of which scientists can detect in the blood. 20 Electronic Engineering Times Europe September 2014 www.electronics-eetimes.com


EETE SEP 2014
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