Many of our classroom chemistry teachers might have mentioned at least once that silicon is the second most abundant element present in the earth’s crust. Now, beyond its quantitative availability, the element is useful for a variety of human technologies – with the most notable examples being the integrated circuits used in a bevy of electronic products, including mobile phones and computers. But as the commercial need dictates, such contraptions utilize the purified form of silicon, which has a diamond structure (that prevents it from being effective in high-efficiency purposes). However, this time around, a group of Carnegie scientists (headed by Timothy Strobel) have successfully synthesized a new ‘type’ of silicon that can potentially account for more applications, like LEDs, transistors and even solar cells.
In a more technical term, the conventional form of purified silicon has indirect band gap semiconducting properties that are not conducive to either absorbing or emitting light. From the perspective of theoretical chemistry, semiconducting materials do have conductivity credentials, but they are depended on the specific energy received by the material that could excite the bound electrons to transcend to a higher energy, conducting state. This particular magnitude of energy is known as the band gap; and as such, indirect band gap materials like the diamond-structured silicon, cannot practically conduct light.
However, in this case, the scientists were able to create an allotrope of silicon, which essentially pertains to a variant physical form of the same element (like diamond and graphite being the variants of carbon). This new silicon allotrope eschews its regular diamond-structure, in favor of what is called the zeolite-type structure. The zeolite boasts of an open framework that accounts for a quasi-direct band gap, which in turn is ideal for the higher efficiency scope required in solar energy conversion technologies.
The allotrope, Si24, was derived from the compound NaSi24 that was created by using an advanced high-pressure precursor process. This contrived compound was then brought down to an optimized temperature level, and the sodium (Na) was completely removed by the procedure of vacuum heating. This ultimately resulted in the pure form of Si24, with its effective capacity to both absorb and emit light, while also showcasing stability up to the temperature of 842 degrees Fahrenheit (or 450 degrees Celsius).
This is what Timothy Strobelh had to say about the potentiality of their achievement –
High-pressure precursor synthesis represents an entirely new frontier in novel energy materials. Using the unique tool of high pressure, we can access novel structures with real potential to solve standing materials challenges. Here we demonstrate previously unknown properties for silicon, but our methodology is readily extendible to entirely different classes of materials. These new structures remain stable at atmospheric pressure, so larger-volume scaling strategies may be entirely possible.