Forget large, bulky solar panels. Soon anything from clothing to cars could be used to harness energy from the sun.
Scientists from Sheffield have developed low-cost, spray-on solar cells that can be applied to surfaces in a similar way to paint.
The cells are made of a material called perovskite, which is cheap to produce and, when used as a spray, produces very little waste.
This, along with the fact the spray can be easily mass produced, means manufacturing costs are low, which ultimately means prices would be lower for customers.
In theory, the spray could be used on any surface that the cells can stick to, however, its efficiency is likely to be affected on flexible surfaces, or fabrics.
Around 85 per cent of photovoltaics currently used are made from crystalline silicon, which has a conversion rate of 25 per cent, on average.
Perovskite is a term used to describe the mineral crystal structure found in the calcium titanium oxide mineral species, made of calcium titanate.
It was first used for solar cells in 2009, but efficiency was low.
Oxford researchers then used polymers to make solid cells, which were eventually engineered to efficiencies of 16 per cent.
The team of scientists from the University of Sheffield is the first to make perovskite solar cells using this spray painting technique.
Experts from the University’s Department of Physics and Astronomy and Department of Chemical and Biological Engineering previously used the method to produce solar cells using organic semiconductors – but using perovskite is considered 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 because they combine high efficiency with low materials costs.
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, perovskites, by comparison, require much less energy to make.
By spray-painting the perovskite layer in the air, the team hope the overall energy used to make a solar cell can be reduced further.
Professor Lidzey added: ‘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.’
He added: ‘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 is a significant step towards efficient, low-cost solar cell devices made using high volume roll-to-roll processing methods.
‘I believe that new thin-film photovoltaic technologies are going to have an important role to play in driving the uptake of solar-energy, and that perovskite based cells are emerging as likely thin-film candidates.’
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