If you try to make some solar thing work from a UV lamp, but it doesn't, does it mean that it's not a real UV? The lamp I tried smells like ozone when works, it emits light blue color when works.


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The short answer is: No, it won't. Traditional PV cells will not work with UV light.

First things first, lets remind overselves how photovoltaic (PV) panels work, as this will provide our answer. PV's are basically giant photodiodes: Light comes in, excites electrons in the semiconductor material, which in essence get knocked loose, and then move on as electrical current. Any time we talk bout exciting electronics, we need to remember out quantum physics: Electrons can only exist in certain energy states. If the electron is resting at low energy, and it needs to get bumped up to a higher energy state, then supply half the energy required does NOTHING. It can't "half way excited" the electron. You either provide enough energy, or you might as well provide nothing. The other bit of physics we need to remember is

E = hc/λ (in SI units) or E = 1.2/λ (in eV, if λ is in μm)

The energy of a photon is inversely proportional to it's wavelength. Photons with long wavelengths (infrared) have less energy, light with shorter wavelength (UV) have more. Infrared has a wavelength of > 1 μm, while UV is < 0.3 μm.

The energy necessary to excite the electrons in your typical PV panel is 1.1 eV, so if E = 1.2/λ , and E > 1.1, then λ < 1.1, So, so long as the photon have a wavelength less not infrared light, it's good. Right?

But, we need to remember that, our PV panels are coated in glass to protect them. And while it vaguely depends on the glass, most glass does not transmit UV light. Light below about 0.3μm will never get to the semiconductor. So what about light in the near UV/far violet... 0.3 μm to 0.4 μm? How does it compare to light at the far red end, of 0.7 μm up to our 1.1 μm cut off? After all, the photons have twice as much energy at the near UV than the near IR. My belief is that practically speaking, PER PHOTON, you get just as much electrical current with near UV as near IR light. Because you need 1.1 eV per photon to push the current, and a 0.4 μm near UV photon has 3 eV, you then waste about 1.9 eV of energy as heat. That is why when you look at current produced PER WATT of light power, UV light gives you less current.

So, per photon, near UV light is just as good. Far UV doesn't work at all, and far IR doesn't work at all.

However, research is being done to make PV cells that do work with non-visible spectrums such as UV and IR. In fact, a company claims to have developed fully transparent solar cells that work only in UV and IR light.

  • 1
    $\begingroup$ I have said that most glass don't let UV light through them $\endgroup$
    – AfiJaabb
    Commented Jun 14, 2020 at 6:04

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