Spray-on solar cells

Solar cells could soon be produced more cheaply using nanoparticle ‘inks’ that allow them to be printed like newspaper or painted onto the sides of buildings or rooftops to absorb electricity-producing sunlight.

Brian Korgel, a University of Texas at Austin chemical engineer, is hoping to cut costs to one-tenth of their current price by replacing the standard manufacturing process for solar cells, gas-phase deposition in a vacuum chamber, which requires high temperatures and is relatively expensive.

‘That’s essentially what’s needed to make solar-cell technology and photovoltaics widely adopted,’ Korgel said. ‘The sun provides a nearly unlimited energy resource, but existing solar energy harvesting technologies are prohibitively expensive and cannot compete with fossil fuels.’

Korgel and his team have been working for two years on this low-cost, nanomaterials solution to photovoltaics manufacturing. Korgel is collaborating with professors Al Bard and Paul Barbara, both of the Department of Chemistry and Biochemistry, and Prof Ananth Dodabalapur of the Electrical and Computer Engineering Department.

The inks could be printed on a roll-to-roll printing process on a plastic substrate or stainless steel. The prospect of being able to paint the ‘inks’ onto a rooftop or building is said to be viable too.

‘You’d have to paint the light-absorbing material and a few other layers as well,’ said Korgel. ‘This is one step in the direction towards paintable solar cells.’

Korgel used the light-absorbing nanomaterials because their microscopic size allows for new physical properties that can help enable higher-efficiency devices.

In 2002, he co-founded a California-based company called Innovalight, which is producing inks using silicon as the basis. Now, Korgel and his team are using copper indium gallium selenide (CIGS), which is cheaper and has less environmental impact.

‘CIGS has some potential advantages over silicon,’ said Korgel. ‘It’s a direct band gap semiconductor, which means that you need much less material to make a solar cell, and that’s one of the biggest potential advantages.’

His team has developed solar-cell prototypes with efficiencies at one per cent; however, they need to be about 10 per cent.

‘If we get to 10 per cent, then there’s real potential for commercialisation,’ Korgel added. ‘If it works, I think you could see it being used in three to five years.’

He also said that the inks, which are semi-transparent, could help realise the prospect of having windows that double as solar cells. Korgel said his work has attracted the interest of industrial partners.