Don't know for sure but this is a cut and paste from Wikipedia
http://en.wikipedia.org/wiki/Solar_photovoltaic
Copied from the Overview section
"The term photovoltaic denotes the unbiased operating mode of a photodiode in which current through the device is entirely due to the transduced light energy. Virtually all photovoltaic devices are some type of photodiode."
I would lean toward the side of caution and as I said I have never been through an EMP. I just remember hearing Richard Allen Miller, this teen whiz kid who got snatched up by the government in the 60's to do research in solid state physics mention that wouldn't it be clever if the were an alien intelligence to get the planet into a technology that could be wiped out in an instant. There are some interviews with Miller at this web site.
http://www.mikehagan.com/radiOrbit_Archives.htm
interesting stuff!