boz
CEO
the solar cell was upsidedown right? Bit weird question, is that why the top p type layer was transparent. Any comments.
Solar Cell Q (1 Viewer)
- Thread starter boz
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boz
CEO
i killed it relatively
die your physics teacher
die your physics teacher
Gomer
Member
I remember my teacher going over this in detail in a study lesson before the last holidays. I forgot to study it, and i think i got the jist of it down onto the paper. I hope i did well.
I talked about how a photon of light hits the electrons in the valence energy band in the p-type conductor, and causes them to 'jump' up into the conducting energy band, and they moved down to the end closest to the n-type, this caused the other end of the p-type to become slightly positive, and the other negative. Setting up a potentional difference and electrons would flow from the n-type and pass through the filament of the globe causing resistance and making the globe emitt light. And a current would flow. Or something along those lines.
I agree, wasn't the n-type ment to be incident to the light, not the p-type. Or am i just tripping?
-- Gomer
I talked about how a photon of light hits the electrons in the valence energy band in the p-type conductor, and causes them to 'jump' up into the conducting energy band, and they moved down to the end closest to the n-type, this caused the other end of the p-type to become slightly positive, and the other negative. Setting up a potentional difference and electrons would flow from the n-type and pass through the filament of the globe causing resistance and making the globe emitt light. And a current would flow. Or something along those lines.
I agree, wasn't the n-type ment to be incident to the light, not the p-type. Or am i just tripping?
-- Gomer
equiski
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I said that due to the photoelectric effect, electrons jump from the n-type layer to the p-type layer. They are unable to return due to the p/n junction so an EMF is formed, with the p-layer becoming negatively charged and the n-type becomes positive. Then i described how the EMF causes a current to flow through the external circuit. I haven't read anythng about the workings of a Photocell, our teacher set those dot ponts as an assignment but i never did it. I just figured out how i thought the thing would work from looking at the diagrams coupled with my limited knowledge of semiconductors and the photoelectric effect.
I probably got it completely wrong though...
I probably got it completely wrong though...
The reaon the teacher is spewing is the dot point removed was
gather, process and analyse secondary information to describe the relationship in solar cells between the photoelectric effect, semiconductors, electric fields and current.
Kept, which was in both
identify data sources gather, process and present information to summarise the use of the photoelectric effect in:
– solar cells
– photocells
The question asked the first not the second. If they still wanted the first they shouldn't have removed it.
gather, process and analyse secondary information to describe the relationship in solar cells between the photoelectric effect, semiconductors, electric fields and current.
Kept, which was in both
identify data sources gather, process and present information to summarise the use of the photoelectric effect in:
– solar cells
– photocells
The question asked the first not the second. If they still wanted the first they shouldn't have removed it.
Gesus
Member
muahah, thank god for success one book, i've done the whole macquarie book a few times and it never talked really about solarcells, success (which i only foundout i had a couple of weeks ago 
) gave like 5 questions on it, and detailed the answers
I talked about how the p-n junction thingy led to a emf as the electrons and holes canceled each other out, making n-type slightly positive and p-type slightly negative, so when a photon (with suffiecient energy ofcourse) hits a atom in the middle, it will release a electron and a hole, and how the electron is attracted to the n-side, and the hole to the p-side, this makes a electron from the n-side goto to the pside via the external circuit
hmm. but for some reason now i think i answered the question wrong :S, i gotta check when it gets uploaded
) gave like 5 questions on it, and detailed the answers I talked about how the p-n junction thingy led to a emf as the electrons and holes canceled each other out, making n-type slightly positive and p-type slightly negative, so when a photon (with suffiecient energy ofcourse) hits a atom in the middle, it will release a electron and a hole, and how the electron is attracted to the n-side, and the hole to the p-side, this makes a electron from the n-side goto to the pside via the external circuit
hmm. but for some reason now i think i answered the question wrong :S, i gotta check when it gets uploaded
Komaticom
Bored Member
Yeah the solar cell was upside down town.
I assumed that although the p-type is electron deficient, light can still liberate electrons, causing LOTS of electrons from n-type to fill holes, blah blah you know the procedure.
I assumed that although the p-type is electron deficient, light can still liberate electrons, causing LOTS of electrons from n-type to fill holes, blah blah you know the procedure.
S
Shuter
Guest
Oh get fucked.SeDaTeD said:
Yeah, I looked at it and went "this looks upside down". So I just wrote it as I normally would be replaced p with n, and n with p. At least they can only dock me some marks, because I described the whole process correctly, just backwards.
Jezzabelle
Member
yeh .. i was trying to forget the exam.. but you just made me remember that dodgy question, i thought it was upside down too... but since the p type was a thin sheet i just crapped on that the rays still infiltrated the n type and the electrons passed through the crystal lattice of n-type and their excess energy after they have passed into the holes of the p-type goes around the circuit.. or somthing...Komaticom said:
gordo
Resident Jew
hold on...
for a solar cell to work in actuality, the p-type can not be exposed to any sunlight at all, or it liberates electrons in the p-type and lowers the potential voltage across the junction at the same rate it increases from the n-type being exposed to light...remember n-type and p-type only differ by an extra electron for every 1.2 million in there (1 in 200000 atoms doped, every atom has 6 electrons)
I think its possible they labelled the diagram incorrectly, or that it is possible for the solar cell still to work by applying light only to the p-type.... i.e. testing a band 6 students knowledge who isn't jsut regurgitating from the book.
i dunno, i wrote that there is already a potential voltage set up in the junction and the n-type becomes positively ionised and the p-type negatively ionised by the respective electron transfer into holes at the junction. The photons then liberate electrons in the p-type and these electrons get attracted to the poisitive ions in the n-type side of the junction, the holes get repelled away from the positive ions in the p-type junction and hence u have electrons flowing out the bottom of the n-type, through the circuit and back up to the holes in the top of the p-type.
i dunno, it was my best guess when they gave a stupi question. Because if both wafers are exposed to photons (and how do u get transparent silicon anyway?) the solar cell will not actually work in real circumstances.
meh, its over
but that paper was exceedingly...'bizarre' at times
for a solar cell to work in actuality, the p-type can not be exposed to any sunlight at all, or it liberates electrons in the p-type and lowers the potential voltage across the junction at the same rate it increases from the n-type being exposed to light...remember n-type and p-type only differ by an extra electron for every 1.2 million in there (1 in 200000 atoms doped, every atom has 6 electrons)
I think its possible they labelled the diagram incorrectly, or that it is possible for the solar cell still to work by applying light only to the p-type.... i.e. testing a band 6 students knowledge who isn't jsut regurgitating from the book.
i dunno, i wrote that there is already a potential voltage set up in the junction and the n-type becomes positively ionised and the p-type negatively ionised by the respective electron transfer into holes at the junction. The photons then liberate electrons in the p-type and these electrons get attracted to the poisitive ions in the n-type side of the junction, the holes get repelled away from the positive ions in the p-type junction and hence u have electrons flowing out the bottom of the n-type, through the circuit and back up to the holes in the top of the p-type.
i dunno, it was my best guess when they gave a stupi question. Because if both wafers are exposed to photons (and how do u get transparent silicon anyway?) the solar cell will not actually work in real circumstances.
meh, its over
but that paper was exceedingly...'bizarre' at times
reecepilgrim
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Yes but both of them were WRONG