PHOTOVOLTAICS | MATERIALS
Organic photovoltaic (OPV) devices – based on plastic substrates – offer an alternative to
traditional silicon-based solar cells. Lou Reade reports on some of the latest progress
Shining examples: latest news in organic solar cells
Plastics are often used to substitute more robust engineering materials, such as metals. Another substitution that is gathering pace is using plastics in place of silicon, in a new breed of photovoltaic (solar) cells. These organic photovoltaic (OPV) devices
generally consist of a plastic film substrate printed with electronic circuits and incorporating highly specialised semiconducting plastic materials. This makes them far cheaper than traditional silicon- based solar cells. They are also highly flexible – meaning OPVs can be used in potentially new applications. Traditionally OPVs have typically been far less
efficient than silicon solar cells. However, this can often be justified thanks to their lower cost. Many researchers are studying OPVs in an
attempt to understand their mechanisms, raise their efficiency and look for new ways of deploying them at a time when solar power is becoming a greater part of the energy mix.
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Good vibrations For instance, scientists at Germay’s TU Dresden and Belgium’s Hasselt University have investigat- ed the physical causes that limit the efficiency of solar cells based on OPVs. The low voltage of the cells is a reason for their low efficiencies. However, the scientists found that fundamental quantum effects – called zero point vibrations – make a significant contribution to voltage losses. The study, published in Nature Communications, found a direct relationship between molecular properties and macroscopic device properties. This provides important information for developing and improving novel organic materials for OPVs, said the researchers. The researchers found that the zero-point
vibrations caused a large amount of absorbed energy – from sunlight – to be re-emitted, which was a factor in reducing the open-circuit voltage. “These voltage losses can now be predicted from electronic and vibronic molecular param-
May 2020 | FILM & SHEET EXTRUSION 33
Main image: Linköping University researchers say that under- standing a quantum
phenomenon could help them increase OPV efficiency
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