
Black silicon photodetector breaks the 100% efficiency limit - Malic
https://phys.org/news/2020-08-black-silicon-photodetector-efficiency-limit.html
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pmdulaney
When they say that the photodetector achieves 130% efficiency, red flags pop
up for anyone trained in science. Is this device creating energy ex nihilo --
like a perpetual motion machine only more so?

It turns out what they mean is that each photon impinging on the device
produces, on average, 1.3 electrons. So there is not an explicit claim from an
energy perspective that the device is more than 100% efficient.

But it does raise the question: Could this technology be used to significantly
boost the efficiency of solar cells? The article does not address that.

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Koshkin
It is just another photomultiplier. These devices in various forms have been
in existence since 1934.

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aijony
I don't think multiple exciton generation (which is what you find searching
for EQE > 100%) is exactly the same as the photoelectric effect. However, your
point more or less stands.

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amerine
> 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.

130% seems really interesting. Is it really just the color change?

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Koshkin
> _earlier been considered as the theoretical maximum_

So... Was the theory (quantum electrodynamics) wrong?

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aijony
No, the theory describes it (well mostly):
[https://en.wikipedia.org/wiki/Multiple_exciton_generation](https://en.wikipedia.org/wiki/Multiple_exciton_generation)

Someone please inform me if I'm missing a subtlety, but this seems like news
for this specific kind of photodetector not physics in general.

