materials science

For cheap solar cells, use ‘spray paint’

U. SHEFFIELD (UK) — Making solar cells with a process similar to spray-painting could significantly lower their cost and make them available to people in developing countries.

The method spray-coats a photovoltaic active layer by an air based process—similar to spraying regular paint from a can—to develop a cheaper technique which can be mass produced.

“Spray coating is currently used to apply paint to cars and in graphic printing,” says David Lidzey, professor at the University of Sheffield.  “We have shown that it can also be used to make solar cells using specially designed plastic semiconductors. Maybe in the future surfaces on buildings and even car roofs will routinely generate electricity with these materials.

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“We found that the performance of our spray coated solar cells is the same as cells made with more traditional research methods, but which are impossible to scale in manufacturing. We now do most of our research using spray coating.

“The goal is to reduce the amount of energy and money required to make a solar cell. This means that we need solar cell materials that have low embodied energy, but we also need manufacturing processes that are efficient, reliable, and consume less energy.”

Most solar cells are manufactured using special energy intensive tools and using materials like silicon that themselves contain large amounts of embodied energy.

Plastic, by comparison, requires much less energy to make. By spray-coating a plastic layer in air, the team hopes the overall energy used to make a solar cell can be significantly reduced. Their research is published in Advanced Energy Materials.

At present, devices are coated onto flat surfaces; however there is nothing to stop coating curved surfaces that could be used in a number of applications. The main restriction is that presently such surfaces need to be very smooth.

A downside to using the plastic as solar cell materials needed for the spray technique is that they are currently not as efficient at generating electricity as cells made from silicon.

The vast majority of solar panels found in the UK are made from silicon and are expected to last more than 25 years. It is unlikely that plastic cells will ever be this stable, but if the energy cost of plastic cells can be lowered enough they will become more effective than silicon over their life cycle.

“Increasing the energy conversion efficiency and lifetime of plastic cells are significant issues that many groups are working on, Lidzey says. “It should also be noted that the cost of silicon solar panels have reduced significantly over the last few years so plastic solar cells will have to catch up with these improvements.”

Researchers from the University of Cambridge contributed to the study.

Source: University of Sheffield

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