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In the current times, I see that most solar panels work fully on 'photo voltaic' effect (visible light -> semiconductor). The manufacturers even ensure to block UV as much as possible to increase the panel lifespan.

On the other hand, Photoelectric effect is when we shine a high frequency/energy light (UV) on a 'metal'. Even though Ozone blocks most UV, I read that around 5% of UV reaches us.

At first, I thought it makes sense to design a system around 'visible light' (photovoltaic effect) coz that is what we get 95%. But when i tried to calculate the 'Power', I see that even the 5% UV ends up giving the same or more power when compared to 95% visible light.

$$ \text{power}=\frac{\text{energy}}{\text{time}}=(\text{photon energy})\times\frac{\text{no. of photons}}{\text{unit time}}. $$

So, my question is: What is the major challenge in building a hybrid solar panel that uses both PE and PV effects? I understand that it cannot be done efficiently in semiconductor panels due to heating issues. But I am thinking more in terms of 2 layers/levels where the first will use up the visible light (photovoltaic) and the second will use 'UV' (photoelectric) or vice versa. This would also ensure we get some output even during cloudy days.

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  • $\begingroup$ What we see in Photovoltaics IS the (inner) photoelectric effect. Of course, we could use a different layerwith a bigger bandgap to harves UV light, too. I am unsure if you asking about that or about somehow using the "classical" PE effect and ejecting the electrons fully from their material. $\endgroup$ Jul 10, 2023 at 8:58
  • $\begingroup$ hi @sir_khorneflakes, I was siding with the 'classical' PE effect, but even the other method is fine. my question is, why is it not incorporated in the solar panels currently and make it a hybrid one? I see most panels come with a coating to completely block UV. so, i understand there must be some major challenge in utilizing both UV and 'visible light' at the same time? I first thought that UV's contribution could be negligible, but it turns to be equal to what 'visible light' gives out. $\endgroup$
    – Janaaaa
    Jul 10, 2023 at 9:06
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    $\begingroup$ Thanks :) have you checked the bandwith of the UV light in question? UV is a rather broad spectrum; when you build PV, you coose one energy. Photons with lower energy contribute nothing, photons with higher energy ae capped to this energy. so, if you use e.g. Zinc oxide with its Bandgap at 3.4 eV, all 10eV photons will only contribute 3.4 eV; the rest goes into heating and damage. Also, the cross section is reduced and not each photon will trigger this effect (fermis golden rule). But using more of the spectrum is something discussed in the field. $\endgroup$ Jul 10, 2023 at 9:23
  • $\begingroup$ So you arrange a panel to possibly eject photoelectrons from the front surface. And you arrange to have an electric field (somehow) to collect them. (1) How does that impact the normal PV operation? (2) How will you actually get energy out of the PEs over and above the energy to collect them? (3) If not in outer space, how do you expect to collect any PEs? $\endgroup$
    – Jon Custer
    Jul 10, 2023 at 14:43
  • $\begingroup$ hi @JonCuster: (1): I am not sure. I was just curious to understand if this is the major challenge stopping us from doing it at present. For (2 & 3): from what i have read, it looks like we get 5% UV at earth's surface level (at our rooftops). So, I assumed that there would be 5 high-energy photons (UV) in every 100 photons which hits the solar panels. Hence, I will not need any additional field to collect them. coz this 5% provides the same power output as 95% visible light photons. I see there are folks doing this already but as a separate product called "UV panels", not as hybrid. $\endgroup$
    – Janaaaa
    Jul 10, 2023 at 17:26

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