MATERIALS | PHOTOVOLTAICS
“This lamination method works with many
different combinations of polymer, and the energy efficiency is just as high as that obtained by conventional manufacturing,” he said. The solar cell modules are being developed and manufactured by a spin-off company called Epishine, which has chosen to aim at the market for indoor cells. The cells absorb indoor illumination and create enough current to power, for example, sensors that measure the indoor humidity or temperature.
Above: Australian researchers are developing solar energy heliostats that use plastics instead of glass
Organic boost Scientists at Linköping University in Sweden have developed a new, simpler method to manufacture organic solar cell modules. The results have been published in the scientific
journal npj Flexible Electronics. “The organic solar cells can be used in many
contexts, not least those in which their special properties are useful,” said Olle Inganäs, professor of biomolecular and organic electronics at Linköping University, who heads the research group. “They are can be semi-transparent, soft and flexible, can be obtained in different colours, and are cheap to manufacture.” In a semi-transparent solar cell module, elec-
trodes with two variants of the polymer PEDOT:PSS (commonly used in organic electronics) are used: one acts as the anode and the other as the cathode. The active layer that absorbs light and produces electrons is located between the electrodes. When the electrodes and the active layer are printed as thin films on top of each other, defects in one layer will act as points of attack for the next layer to be printed. These defects cause short- circuits between the top and bottom, which until now has been solved by passing a current through the cell. “The defects in each individual cell must be burned away,” said Inganäs. “This is time-consum- ing, and it’s not easy to gain access to all cells – so the reject rate for faulty units is quite high.” The researchers have now tested a method
Right: Two Quentis grades of PP from Borealis were used in a co-extruded solar backsheet
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where the active polymer material is used as glue. Two plastic films, one with the anodes and the other with the cathodes, are covered by the active material before the complete unit is laminated together. Since only two layers are printed, there are fewer defects – and the chance of them being located exactly opposite each other during the lamina- tion is negligible.
FILM & SHEET EXTRUSION | May 2018
www.filmandsheet.com
Bright idea Australian researchers have begun field trials to develop highly efficient solar energy heliostats that use plastics in place of glass. Car parts manufacturer Precision Components
has teamed up with the University of South Australia to open the concentrated solar research field in Adelaide. The trial includes 25 heliostats each measuring 7.2 sq m and a 16m tall concen- trated solar photovoltaic (PV) receiver, which can generate about 30kW of electricity per hour. Heliostats concentrate sunlight onto a tower and – depending on the type of receiver unit – either heat molten salt (to generate steam to drive turbines that generate electricity), or convert sunlight directly into electricity. The tower at the site can be adapted to trial both technologies. The heliostats are currently made of traditional
glass, but the researchers are adapting their thin film coating technology to make lightweight, durable polycarbonate mirrors. Tanya Monro, the university’s deputy vice chancellor of research and innovation, said that all heliostats installed worldwide currently use glass with a thin layer of silver located at the rear of the glass. This means that the sunlight must travel twice through the glass – a material that is heavy, fragile and hard to install. “If we can make plastic heliostats – where the
coatings are on the front – they will be lighter, less fragile, cheaper and stay cleaner for longer,” she said.
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