You can perform a simulated photoelectric effect experiment with this java applet.
You can adjust 1. photon energy 2. light intensity 3. work function of the metal and 4. the voltage of the circuit (can be positive or negative).
The I-V current will be shown. The default mode is auto (The voltage of the circuit will start from cutoff voltage and increase with 0.3V every 10 seconds.) .
The simulation will be paused when it is more than 2.5 V.
You can adjust one of the parameters and press the play button again.
You can turn off "auto" mode and try the experiment by yourself,too.