October 31, 2024
A trick of light: UC Irvine researchers turn silicon into direct bandgap semiconductor
Discovery enables manufacturing of ultrathin solar panels, advanced optoelectronics

Irvine, Calif., Oct. 31, 2024 — By creating a new way for light and matter to interact, researchers at the University of California, Irvine have enabled the manufacturing of ultrathin silicon solar cells that could help spread the energy-converting technology to a vast range of applications, including thermoelectric clothing and onboard vehicle and device charging.

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Co-author Ara Apkarian, UC Irvine Distinguished Professor emeritus of chemistry, said: “This phenomenon fundamentally changes how light interacts with matter. Traditionally, textbooks teach us about so-called vertical optical transitions, where a material absorbs light with the photon changing only the electron’s energy 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.”

According to the researchers, the development creates an opportunity to exploit recent advances in semiconductor fabrication techniques at the sub-1.5-nanometer scale, which has the potential to affect photo-sensing and light-energy conversion technologies.

“With the escalating effects of climate change, it’s more urgent than ever to shift from fossil fuels to renewable energy. Solar energy is key in this transition, yet the commercial solar cells we rely on are falling short,” Potma said. “Silicon’s poor ability to absorb light means that these cells require thick layers – almost 200 micrometers of pure crystalline material – to effectively capture sunlight. This not only drives up production costs but also limits efficiency due to increased charge carrier recombination. The thin-film solar cells that are one step closer to reality due to our research are widely seen as the solution to these challenges.”

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