Silicon variant could find use in solar cells and LEDs

Developed by a team of Carnegie scientists from the US, the silicon is a so-called allotrope, which means a different physical form of the same element, in the same way that diamonds and graphite are both forms of carbon. Unlike the conventional diamond structure, the silicon allotrope consists of an open framework, called a zeolite-type structure, which is comprised of channels with five, six and eight membered silicon rings. To create it, the researchers used a novel precursor process in which a compound of silicon and sodium, Na₄Si₂₄, was formed under high pressure conditions. The compound was then recovered to ambient pressure, and the sodium was completely removed by heating under vacuum. The resulting pure silicon allotrope, Si₂₄, is said to have the ideal band gap for solar energy conversion technology, and can absorb, and potentially emit, light far more effectively than conventional diamond structured silicon. What's more, it is stable at ambient pressure to at least 450°C. Researcher Duck Young Kim said: "Advanced electronic structure theory and experiment have converged to deliver a real material with exciting prospects. "We believe that high pressure research can be used to address current energy challenges, and we are now extending this work to different materials with equally exciting properties."