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Author Topic: Photovoltaics at much lower energies (room temperature/ energy)  (Read 1344 times)

Offline McKay

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Ordinary photovoltaics work by depleting phosphorus and boron doped silicon in each other and creating a permanent electric field, which then separates any pair of hole and electron induced to the conducting band by a incoming photon, creating an additional electric potential difference, which can discharge only trough an external circuit. Right, close, correct?

Ok, so, from what i have been told and understand, the electrons in a phosphorus doped silicon crystal are, at room temperature (even lower, but how much lower?) or higher, are close to or already at the conduction band energy level (as the so called "free electrons", swimming from atom to atom..). That is, effectively, that low energy photons, room temperature kinetic energy is enough to rise them to the conduction band (?)
So, why deplete the doped silicon to throw the electrons in lower energies, when we could leave them at high energy and, potentially, generating usable electric energy from low level temperature, IR and even room temperature itself?

How to do that? Well, I want to ask about one arrangement here I thought up.
Simply, charge the boron doped silicon from another source of electrons, instead of connecting it to the phosphorus doped silicon, creating a negatively charged block of silicon. Now, just take the charged block and connect it to the phosphorus doped silicon with a thin, isolating layer between them (or, maybe, even without isolating layer?) --- would the electric field from charged block be enough to separate the hole from electron (push away electrons and attract holes) doing kinda the same as an ordinary PV cell, but at much lower energies (much more effective and useful)?


 

Offline wolfekeeper

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If I've understood you correctly, no, the photovoltaic works when a high energy photon moves the electron up to a quantum state where it is conductive.

The photon is high energy because it comes from the Sun, which is at about 6000K. Near room temperature photons wouldn't be nearly as good, but have been proposed.
 

Offline McKay

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Yes, normal photovoltaic cells work with relatively hight energy level photons, but what I am asking here is - what is the energy required to get and electron from room temperature phosphorus doped silicon to the conduction level?
And I mean not-discharged phosphorus doped silicon. Just the phosphorus doped silicon block.
 

Offline wolfekeeper

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Don't know, but you can't use IR photons from something at the same temperature as the silicon; solar panels can't beat Carnot efficiency, so the lower the energy/temperature of the photons you're designing for the lower the efficiency and the lower the power output.
 

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