Crystalline silicon method could benefit the solar industry

Silicon dioxide, found in nature as sand, makes up about 40 per cent of the Earth’s crust, but the industrial method for converting it into crystalline silicon is expensive and has a major environmental impact due to the extreme processing conditions.

‘The crystalline silicon in modern electronics is currently made through a series of energy-intensive chemical reactions with temperatures in excess of 2,000°F that produces a lot of carbon dioxide,’ said Stephen Maldonado, professor of chemistry and applied physics at the University of Michigan.

Recently, Maldonado and chemistry graduate students Junsi Gu and Eli Fahrenkrug discovered a way to make silicon crystals directly at 180°F.

Maldonado and colleagues made a solution containing silicon tetrachloride and layered it over a liquid gallium electrode. Electrons from the metal are said to have converted the silicon tetrachloride into raw silicon, which then dissolved into the liquid metal.

‘The liquid metal is the key aspect of our process,’ Maldonado said in a statement. ‘Many solid metals can also deliver electrons that transform silicon tetrachloride into disordered silicon, but only metals such as gallium can additionally serve as liquids for silicon crystallisation without additional heat.’