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posted by Fnord666 on Sunday August 16 2020, @05:38PM   Printer-friendly
from the Wait,-what? dept.

Black silicon photodetector breaks the 100% efficiency limit:

Aalto University researchers have developed a black silicon photodetector that has reached above 130% efficiency. Thus, for the first time, a photovoltaic device has exceeded the 100% limit, which has earlier been considered as the theoretical maximum for external quantum efficiency.

"When we saw the results, we could hardly believe our eyes. Straight away we wanted to verify the results by independent measurements," says Prof. Hele Savin, head of the Electron Physics research group at Aalto University.

The independent measurements were carried out by the German National Metrology Institute, Physikalisch-Technische Bundesanstalt (PTB), which is known to provide the most accurate and reliable measurement services in Europe.

Head of the PTB Laboratory of Detector Radiometry, Dr. Lutz Werner comments, "After seeing the results, I instantly realized that this is a significant breakthrough—and at the same time, a much-welcomed step forward for us metrologists dreaming of higher sensitivities."

[...] The results leading to the record efficiency has been accepted for publication in Physical Review Letters in an article titled "Black-silicon ultraviolet photodiodes achieve external quantum efficiency above 130%."

Garin et al. Black-silicon ultraviolet photodiodes achieve external quantum efficiency above 130%, Physical Review Letters (2020). arxiv.org/abs/1907.13397


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  • (Score: 3, Informative) by c0lo on Monday August 17 2020, @01:25AM

    by c0lo (156) Subscriber Badge on Monday August 17 2020, @01:25AM (#1037687) Journal

    So how does this dovetail with Einstein's photoelectric effect and theories?

    It doesn't contradict it, in solid/liquid phase the energy levels are smeared into large absorption bands (in contrast with rarefied gasses, with a nice emission/absorption narrow lines).

    See also Compton scattering [wikipedia.org], where the "collision" of an X-ray photon leads to an emergent photon with lower energy. Compton scattering works at higher energies (X-ray), enough for the electrons to be considered "quasi-free" (the binding energy of the electron being so much smaller than the incident photons). Even if UV energy is lower, it has at least twice of the band-gap energy of the silicon (3eV+ for UV, 1.1eV for bandgap of silicon).

    Supplementary, these guys used a nanostructured silicon photodiode, far from the homogeneous medium usually assumed by the basic theories. See also black silicone [wikipedia.org] (nano-patterned for a very low-reflectivity/high-absorption)

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