Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Short circuit photocurrent

  1. Jan 29, 2012 #1
    In my phototelectrochemical setup I have a working electrode, reference electrode and a counter electrode . Now I need to measure the short circuit photocurrent so that I can calculate IPCE (incident photon to photocurrent efficiency). How will I measure this current ?
     
  2. jcsd
  3. Feb 1, 2012 #2

    Bobbywhy

    User Avatar
    Gold Member

    It is not possible to answer you because you have listed three electrodes. We measure current beteween TWO points, and you've listed three. I can't know what they mean, or what signals they connect to. Can you give us a schematic diagram? Usually a
    Digital Multimeter would be used to measure the current.
     
    Last edited: Feb 1, 2012
  4. Feb 2, 2012 #3
    Actually, you do NOT want to use a digital multimeter. Most digital multimeters pass the current through a shunt resistor and measure the voltage drop. If the meter has good documentation, the amount of this voltage drop will be specified somewhere, but it can often be a tenth of a volt or more, which is enough to affect the output current of many photoelectric devices. To get a good measure of short circuit photocurrent, you want an op-amp circuit designed to force zero voltage across the device--a true short circuit. The most basic such circuit has the non-inverting input of the op-amp grounded, a calibrated resistor between the output and the inverting input, and you hook your photoelectric device up between ground and the inverting output of the op-amp. The two terminals of the device will be at ground and virtual ground, and all of the current from the device will be flowing through the calibrated resistor thanks to negative feedback. The voltage across this calibrated resistor tells you the current. Keep the direction of the current in mind, as that will determine whether the output of the op-amp is trying to go positive or negative. Chose a value for your calibrated resistor such that the largest and the smallest current that you will need to measure result in output voltages for the op-amp that are not too close to the rails.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook