Mild momentum turns pure silicon from an oblique to a direct bandgap semiconductor – Uplaza

UC Irvine-led analysis reveals that the optical properties of supplies may be dramatically enhanced—not by altering the supplies themselves, however by giving the sunshine new properties.

The researchers demonstrated that by manipulating the momentum of incoming photons, they may essentially change how gentle interacts with matter. One hanging instance from their findings is that the optical properties of pure silicon, a extensively used and important semiconductor, may be enhanced by an astonishing 4 orders of magnitude.

This breakthrough holds nice promise to remodel photo voltaic power conversion and optoelectronics at giant. The research, featured as the quilt story of the September concern of ACS Nano, was performed in collaboration with Kazan Federal College and Tel Aviv College.

“In this study, we challenge the traditional belief that light-matter interactions are solely determined by the material,” stated Dmitry Fishman, senior creator and adjunct professor of chemistry. “By giving gentle new properties, we will essentially reshape the way it interacts with matter.

“As a result, existing or optically ‘underappreciated’ materials can achieve capabilities we never thought possible. It’s like waving a magic wand—rather than designing new materials, we enhance the properties of existing ones simply by modifying the incoming light.”

“This photonic phenomenon stems directly from the Heisenberg uncertainty principle,” stated Eric Potma, co-author and professor of chemistry. “When light is confined to scales smaller than a few nanometers, its momentum distribution widens. The momentum increase is so substantial, that it surpasses that of free-space photons by a factor of a thousand, making it comparable to the electron momenta in materials.”

Ara Apkarian, a distinguished professor of chemistry, expanded on this, saying, “This phenomenon essentially modifications how gentle interacts with matter. Historically, textbooks train us about vertical optical transitions, the place a fabric absorbs gentle with the photon altering solely the electron’s power state.

“However, momentum-enhanced photons can change both the energy and momentum states of electrons, unlocking new transition pathways we hadn’t considered before. Figuratively speaking, we can ’tilt the textbook’ as these photons enable diagonal transitions. This dramatically impacts a material’s ability to absorb or emit light.”

Fishman continued, “Take silicon, for instance—the second most considerable aspect in Earth’s crust and the spine of contemporary electronics. Regardless of its widespread use, silicon is a poor absorber of sunshine, which has lengthy restricted its effectivity in units like photo voltaic panels.

“It is because silicon is an oblique semiconductor, which means it depends on phonons (the lattice vibrations) to allow digital transitions. The physics of sunshine absorption in silicon is such that whereas a photon modifications the electron’s power state, a phonon is concurrently wanted to vary the electron’s momentum state.

“Since the likelihood of a photon, phonon, and electron interacting at the same place and time is low, silicon’s optical properties are inherently weak. This has posed a significant challenge for optoelectronics and has even slowed progress in solar energy technology.”

Potma emphasised, “With the escalating results of local weather change, it is extra pressing than ever to shift from fossil fuels to renewable power. Photo voltaic power is essential on this transition, but the industrial photo voltaic cells we depend on are falling quick.

“Silicon’s poor capacity to soak up gentle means these cells require thick layers—nearly 200 micrometers of pure crystalline materials—to successfully seize daylight. This not solely drives up manufacturing prices but in addition limits effectivity because of elevated service recombination.

“Thin-film solar cells are widely seen as the solution to both of these challenges. While alternative materials like direct bandgap semiconductors have demonstrated thin solar cells with efficiencies exceeding 20%, these materials are often prone to either rapid degradation or come with high production costs, making them impractical at the moment.”

“Guided by the promise of Si-based thin-film photovoltaics, researchers have been searching for ways to improve light absorption in silicon for more than four decades,” Apkarian added. “But a true breakthrough has remained elusive.”

Fishman continued, “Our strategy takes a radically completely different step ahead. By enabling diagonal transitions via momentum-enhanced photons, we successfully rework pure silicon from an oblique to a direct bandgap semiconductor—with out altering the fabric itself. This results in a dramatic enhance in silicon’s capacity to soak up gentle, by a number of orders of magnitude.

“This means we can reduce the thickness of silicon layers by the same factor, opening the door to ultra-thin devices and solar cells that could outperform current technologies at a fraction of the cost. Moreover, because the phenomenon does not require any changes to the material, the approach can be integrated into existing fabrication technologies with little to no modifications.”

Apkarian concluded, “We’re simply starting to discover the wide selection of phenomena related to gentle confinement on the nanoscale and past. The physics concerned is wealthy with potential for basic and utilized discoveries. Nevertheless, the instant influence is already clear.

“Transforming silicon into a direct bandgap semiconductor through enhanced photon momentum has the potential to revolutionize energy conversion and optoelectronics.”

Co-authors on this research included Jovany Merham, a UC Irvine junior specialist in chemistry, Kazan Federal College researchers Sergey Kharintsev, Aleksey Noskov, Elina Battalova, and Tel Aviv College researchers Liat Katrivas and Alexander Kotlyar.