Cheaper silicon means cheaper solar cells

By using silicon fibres coated in glass, researchers have been able to make solar cells from silicon that is 1000 times less pure, and thus much cheaper, than the current industry standard. Photo: Fredrik A. Martinsen

A new method of producing solar cells could reduce the amount of silicon per unit area by 90 per cent compared to the current standard. With the high prices of pure silicon, this will help cut the cost of solar power.

“We’re using less expensive raw materials, and smaller amounts of them,  we have fewer production steps and our total energy consumption is potentially lower,” explain PhD candidate Fredrik Martinsen and Professor Ursula Gibson, from NTNU’s Department of Physics.

They recently published their technique in Scientific Reports. Their processing technique allows them to make solar cells from silicon that is 1000 times less pure, and thus less expensive, than the current industry standard.

Glass fibres with a silicon core

The researchers’ solar cells are composed of silicon fibres coated in glass. A silicon core is inserted into a glass tube about 3 mm in diameter. This is then heated up, so that the silicon melts and the glass softens. The tube is stretched out into a thin glass fibre filled with silicon. The process of heating and stretching makes the fibre up to 100 times thinner.

This is the widely accepted industrial method used to produce fibre optic cables. But researchers at the Department of Physics at NTNU, working with collaborators at Clemson University in the USA, are the first to use silicon-core fibres made this way in solar cells. The active part of these solar cells is the silicon core, which has a diameter of about 100 micrometres.

Lower energy consumption

This production method also enabled them to solve another problem: traditional solar cells require pure silicon. The process of manufacturing a pure silicon wafers is laborious, energy-intensive and expensive.

“We can use relatively dirty silicon, and the purification occurs naturally as part of the process of melting and re-solidifying in fibre form. This means that you save energy, and several production steps.”

It is estimated that it will take roughly one-third of the energy to produce solar cells with this method compared to the traditional approach of producing silicon wafers.

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