[sdiy] Eu might be banning Vactrols and LDRs??

[Scott Nordlund]

Solar cells are actually the same as photodiodes, only with a much
larger junction.  Where photodiodes are usually optimized for speed,
a solar cell will have a large junction capacitance and thus a slow
response time.  

If you reverse bias it, I'd guess you could get some sort of resistor
effect out of it.  Just remember that photocurrent goes the "wrong 
way".



----------------------------------------
> From: lanterma at ece.gatech.edu
> To: synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] Eu might be banning Vactrols and LDRs??
> Date: Thu, 10 Sep 2009 21:30:23 -0400
>
> On Sep 10, 2009, at 9:23 PM, Scott Nordlund wrote:
>
>> A solar cell is basically a large diode, where a CdS photoresistor
>> is just a piece of semiconductor with no junction. In both cases
>> the incident photons generate electron-hole pairs, but in a solar
>> cell the electrons and holes are separated by the electric field in
>> the junction's depletion region and travel to the cathode/anode,
>> thus producing a voltage potential. In a photoresistor, the
>> electron-hole pairs just facilitate conduction (reducing resistance).
>
>
> It's been a good, uhm, 18 or so years since I last looked at this
> device physics stuff, so this is probably a silly question, but...
> would be it possible to "hack" a solar cell to make it act as a
> photoresistor? Chop off part of it and attach some wires or something?
>
> Just idly curious.
>
> - Aaron
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