effects of shading on solar panels

Wow! This is an old one, post that is, but what the hay.
Take a good look at any PV module and you can see that it is made up of individual cells. Some modules let you see just how they are soldered together in series/parallel. Just for example: One cell may only have an output of 0.1 amps at 9 volts. So if 36 of them are "wired" in parallel the amperage increases to 3.6 while the voltage stays the same. If a second "string" of cells is "wired" to the first in series then the amperage stays the same and the voltage doubles. Now we have 72 cells wired in series/parallel for a combined putput of 3.6 amps at 18 volts. So now maybe one can see that if a PV module is partically shaded its output will diminish. Its like removing cells from the strings. What diode do are to isolate one string from another because the one in the Sun will "drive" the one in the shade.