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A question about photoconductivity and photoresistors

  1. May 10, 2013 #1

    ShayanJ

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    In the process of photoconductivity,light incident on a semiconductor,causes some of its electrons to jump to the conduction band and so,increases the semiconductor's conductivity.Now my question is,Is there a material for which,such process may happen by incident lights in the visible spectrum,more specifically,by red light?If yes,how can I find out what is it?
    Thanks
     
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  3. May 10, 2013 #2

    DrDu

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    E.g. silicon. Never used a solar cell?
    More generally this works with any semiconductor for which the band gap is lower than the photon energy of the light.
     
  4. May 10, 2013 #3

    ShayanJ

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    I think you're talking about photoelectric effect and the word «band gap» in your post,must be replaced by «work function».
    I don't think photoelectric effect can help me,especially that a red light photon has an energy near 2eV,but if you look at http://en.wikipedia.org/wiki/Work_function#Measurement ,you will see that the work function of all of the elements listed,is greater than 2.
    The thing I was talking about is different from photoelectric effect.In photoelectric effect,the electrons struck by photons,are kicked out of the metal and by reaching the conductor on the opposite side,create a current.But in photoconductivity,electrons remain in the semiconductor and just change their energy level,reaching the conduction band.
     
  5. May 10, 2013 #4

    DrDu

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    No, I was not talking about the photoelectric effect. In solar cells, photoresistors etc, electrons are lifted to the conduction band.
     
  6. May 10, 2013 #5

    ShayanJ

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    Oh...I thought they just use photoelectric effect...thanks...
    Anyway,the material I need,should have a band gap which is lower than or equal to the energy of a red light photon,i.e. 1.67eV-2eV.How can I find such specific materials?
    Thanks
     
  7. May 10, 2013 #6

    ShayanJ

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    I searched a little and...Well,looks like,as you said in the first place,silicon is OK.
    Thanks
     
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