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LED photodetector IV curves

  1. Jun 8, 2009 #1
    I was wondering if anybody could help me understand my measurements. I was interested in measuring the photo current and voltage of a red LED placed in room light and sun light. I measured the voltage across the LED and the current through in both conditions.

    In the room measurement, I am measuring the diode while it is being illuminated by the room incandescent lighting. I see voltages anywhere from 30mV to 90mV. The current is too small for my cheap meter to measure.

    In the sun measurement, I am measuring the diode while is being illuminated in sunlight. I see correlation to the room measurement in that the room samples with the lowest open circuit voltage have the lowest short circuit current. However the strange thing is that the open circuit voltage measurements in sunlight are larger for the units with lower current.

    I was hoping someone could either explain or point me to a good reference. I have enclosed the measurements below.

    Thanks in advance,

    Incandescent Sun
    Diode Voc (V) Isc (A) Voc (V) Isc (A)
    D1 7.80E-02 to low to measure 1.402E+00 9.40E-06
    D2 7.20E-02 to low to measure 1.403E+00 9.00E-06
    D3 6.60E-02 to low to measure 1.398E+00 8.30E-06
    D4 6.30E-02 to low to measure 1.392E+00 8.20E-06
    D5 8.90E-02 to low to measure 1.390E+00 9.90E-06
    D6 7.90E-02 to low to measure 1.394E+00 9.10E-06
    D7 3.10E-02 to low to measure 1.483E+00 6.90E-06
    D8 7.30E-02 to low to measure 1.400E+00 8.70E-06
    D9 7.70E-02 to low to measure 1.408E+00 9.30E-06
    D10 3.90E-02 to low to measure 1.479E+00 6.40E-06
  2. jcsd
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