UC Irvine research: Slowing the speed of light (With Groundbreaking UC Irvine Research) Groundbreaking UC Irvine research shows how to boost pure silicon’s optical properties by controlling light momentum, a discovery that could transform solar energy and optoelectronics.
Peeling Away the Silicon
As the workhorse of modern electronics, silicon is ubiquitous: It’s the most abundant element in Earth’s crust and an essential component of computer chips. Despite this, its low ability to absorb light has been a major obstacle in the creation of more effective solar cells and optoelectronic devices.
Silicon is traditionally an indirect semiconductor, which works through coupling with phonons (lattice vibrations) to give access to electronic transitions. So a photon is required to scatter off both an electron and a phonon simultaneously in order to promote the electron to an excited energy level. For example, silicon absorbs photons emitted from the sun due only to its weak absorption coefficients, making the optical properties of this material unsuitable for many applications in solar energy technology and more lucrative and rare processes.
Optical Twisting Based on Momentum
Researchers at UC Irvine, in collaboration with colleagues from Kazan Federal University and Tel Aviv University, have uncovered an innovative solution to this ongoing roadblock through their breakthrough study.
Using this quirk of photons, the researchers have been able to transform the way that light interacts with silicon. Basically, when light is trapped at the scale measured in nanometers, its momentum distribution becomes a thousand times broader than that of free-space photons. Silicon can now be excited directly by this momentum-boosted photon, without the requirement of phonon interactions.
So, in effect, the researchers have tuned pure silicon from an indirect to a direct bandgap semiconductor, without changing the material itself. The discovery has now created new transition pathways for light–matter interactions and increases silicon’s absorption and emission of light by many orders of magnitude.
Conclusion
Such a discovery has immense potential to radically alter the field of solar energy conversion and optoelectronics. This improves the optical properties of silicon – which is essential for processing solar cells, amongst other devices – in such a way that the researchers have written “opening the door” to realistic high efficiency thin cost-efficiently produced thin silicon based (<300µm) for different applications outshining current technologies. With the world in desperate need for clean energy solutions, this silicon photonics breakthrough is a major advancement on the all-important global energy and climate front.
