Normal metal is a slinky on it’s end: very rigid and a poor material for producing power. But if you use particular materials (like the ones used in solar panels) you have a slinky that usually stays in the stretched out position. When a photon comes in from the sun carrying energy it strikes this slinky of metal like a marble would. The energy is absorbed and causes ripples along the slinky. Conservation of energy.

I’m not sure if it is possible for photons to knock electrons out of their orbits but this isn’t the case as far as solar panels go.
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It’s like Formula 1 racing or NASCAR. The car will be sitting in the Pit, just waiting to go, then will tear out, run a few laps until it requires more fuel, then stops in the Pit again, gets refueled, and just waits for the signal from the Pit Boss to get going again.

The limiting factor on solar cells isn’t the cell itself, as in the electrical circuits and semiconductors, but rather the very slow degradation of the (usually plastic) that holds each small cell in place, so that it can create a useful photovoltaic cell. Since modern plastics can be treated with UV coatings to prevent degradation, and are practically immune to water, the only thing that can really hurt them is somebody whacks it with a hammer or drops it while installing it on the roof.

They’re excellent. The south face of my roof is sufficient, along with a small vertical-axis wind turbine, to generate more power than I need, and it actually gets sold back to Sempra Energy/SDG&E.
References :
Experienced engineering geologist.

http://science.nasa.gov/headlines/y2002/solarcells.htm
http://www.howstuffworks.com/solar-cell.htm