# How do solar panels work? **URL:** \ **Category:** Factual Questions\ **Created:** [July 1, 2007, 3:55pm UTC](https://boards.straightdope.com/t/how-do-solar-panels-work/410126 "2007-07-01T15:55:49Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![CanTak3](https://avatars.discourse-cdn.com/v4/letter/c/f14d63/32.png) [@CanTak3](https://boards.straightdope.com/u/CanTak3)\ **Post date:** [July 1, 2007, 3:55pm UTC](https://boards.straightdope.com/t/how-do-solar-panels-work/410126/1 "2007-07-01T15:55:49Z")
I’m trying to figure out how photons hitting the solar panels create electricity. My first thought is that through E=mc^2 the photons could somehow actually be converted into electrons. This can’t be the case I reason because the electrons must travel back to the solar panel to complete the circuit. Therefore you’d always be adding more and more electrons to it which can’t be right… Next I start to think that somehow the electrons simply ‘knock loose’ an electron from it’s outer shell around some kind of atom that can be balanced by loosing an electron. If my periodic table days in school haven’t left me, this would be an atom with one electron in the outer shell. This also can’t be the case I reason, because why would this electron travel through the circuit to get back to where it started? Shouldn’t it just rebond with the same atom it was knocked loose from? Also, this would mean there’s a finite amount of energy produced from a solar panel. So what’s the straight dope? Where do the photons go? Where does the electric potential go? Is this unlimited or is there a finite limit to the panel? ---
**Author:** ![essell](https://avatars.discourse-cdn.com/v4/letter/e/34f0e0/32.png) [@essell](https://boards.straightdope.com/u/essell)\ **Post date:** [July 1, 2007, 4:12pm UTC](https://boards.straightdope.com/t/how-do-solar-panels-work/410126/2 "2007-07-01T16:12:00Z")
> [@wikipedia](#): > > Simple explanation > > 1. Photons in sunlight hit the solar panel and are absorbed by semiconducting materials, such as silicon. > 2. Electrons (negatively charged) are knocked loose from their atoms, allowing them to flow through the material to produce electricity. The complementary positive charges that are also created (like bubbles) are called holes and flow in the direction opposite of the electrons in a silicon solar panel. > 3. An array of solar panels converts solar energy into a usable amount of direct current (DC) electricity. Looks like you were almost right with your second guess. IIRC remember correctly from my school years the electrons in some metals are not tightly bound to their atoms, but exist in a kind of ‘haze’ or ‘soup’ in the metal, which is what makes the conductors in the first place. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [July 1, 2007, 4:18pm UTC](https://boards.straightdope.com/t/how-do-solar-panels-work/410126/3 "2007-07-01T16:18:18Z")
Basically, extra electrons are looking for empty holes. Then the process begins again. From [http://www.howstuffworks.com/solar-cell2.htm](http://www.howstuffworks.com/solar-cell2.htm) : > [@](#): > > Only part of our solar cell is N-type. The other part is doped with boron, which has only three electrons in its outer shell instead of four, to become P-type silicon. Instead of having free electrons, P-type silicon (“p” for positive) has free holes. Holes really are just the absence of electrons, so they carry the opposite (positive) charge. They move around just like electrons do. > > The interesting part starts when you put N-type silicon together with P-type silicon. Remember that every PV cell has at least one electric field. Without an electric field, the cell wouldn’t work, and this field forms when the N-type and P-type silicon are in contact. Suddenly, the free electrons in the N side, which have been looking all over for holes to fall into, see all the free holes on the P side, and there’s a mad rush to fill them in. AFAIK, there is no limit to the cycle, although other factors may cause the panel to age beyond a usable life. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [July 1, 2007, 4:25pm UTC](https://boards.straightdope.com/t/how-do-solar-panels-work/410126/4 "2007-07-01T16:25:53Z")
[Start here.](http://en.wikipedia.org/wiki/Solar_cell#Simple_explanation) The key behind it is the band gap. If you know how a solid-state diode works, think of the photon as knocking an electron to the “wrong side” of the junction. The poor electron can’t cross back. After a lot of photons have knocked a lot of electrons, you have a buildup of charge which you can use.