Can energy, and so information, be transferred between silicon atoms and an organic molecule? It is a question technologists have been asking for forty years. Finally, researchers from The University of Texas at Austin and the University of California, Riverside have answered that question in the affirmative. Their discovery could have implications for information storage in quantum computing devices as well as energy conversion. [Roberts, S. et al., Nature Chem. (2019); DOI: 10.1038/s41557-019-0385-8]
All information and communications technology pivots on a grain of sand, well, strictly spreaking, the purified and crystalline element silicon present in the silica of sand. But, silicon is compromised when it comes to converting light into electricity, it works really well with low-energy red light photons, but not higher-energy blue. In contrast, organic materials can absorb blue light and even high frequencies well. So the obvious workaround is to couple the two. A hybrid material that exploits the organic to trap the energy of blue light and pass it on as pairs of red photons to the silicon would be very useful for energy conversion. Conversely, it could absorb red light on the silicon side and convert that into blue photons for medical imaging applications and quantum computing.
The team has coupled the polyaromatic hydrocarbon anthracene, a molecule present in soot, to nanocrystalline silicon surfaces. "We now can finely tune this material to react to different wavelengths of light," explains Roberts. "Imagine, for quantum computing, being able to tweak and optimize a material to turn one blue photon into two red photons or two red photons into one blue. It's perfect for information storage."
The team's approach does not rely on the simple layer of the two materials. That method never brought about the desired spin-triplet exciton transfer. Instead, the team functionalized the silicon nanocrystal surface with the anthracene and saw the predicted energy transfer between them for the first-time.
"The challenge has been getting pairs of excited electrons out of these organic materials and into silicon," Roberts explains. "It can't be done just by depositing one on top of the other." The team's "nanowiring" between nanocrystal and organic, allowed about 90% of the energy to be transferred from the former to the latter. Because the materials science has sidestepped toxic heavy metals, applications in human medicine, bioimaging, and environmentally sustainable technologies are now more feasible.