Here are some samples of damaged solar panels, some due to lightning and some due to storms knocking trees onto solar panels. Thanks to Ottawa Solar Power for the use of most of these photos.
Shattered glass on solar panels
The photos below are of a solar panel that had a tree fall on it when the tree fell onto the roof during a storm. You can see the one spot where the tree hit, the whitish spot, but since it hit tempered glass the whole glass shattered.
Solar panels have tempered glass glued to the front side the panel, with the solar cells and tinned strips of metal for connecting the cells together immediately behind the glass. Tempered glass is designed to shatter in many small pieces instead of large dangerous shards as you get with normal window glass. Car windows are also tempered glass.
When the glass of a solar panel breaks, it breaks into many small pieces, but because the tempered glass has glue on the inside face, the many small pieces stay in place. But even if the solar cells behind are not damaged, not nearly as much light can get to them due to the misshapen glass.
Repairable solar panel with shattered glass
However, with the solar panel below, the shattering occured on only a small portion of the bottom left face. There was still enough light getting through to produce a usuable output and so the owner simply repaired the solar panel by waterproofing it. See the link for details.
The following solar panel came from a system that was struck by lightning somewhere and no longer works. As well as damaging the electronics in the box in the back of the panel where the connecting wires go to, it produced enough heat to cause visible damage to the box itself. You can see where it got hot enough from the high electrical current to melt a round hole in the box.
You usually can't fix a solar panel that's been struck by lightning. However, inside the plastic box behind the solar panel are some diodes. I once fixed a solar panel by replacing those diodes, as it was one of the diodes that was damaged. If the diodes are encased in epoxy then you can't get at them. In the one I repaired the diodes were visible, and removable using screws. It was a customer's panel and I don't know if the cause was lightning or something else.
Below are photos showing how lightning damaged one solar power system. The lightning struck the tree, and you can see the physical damage to the tree where it was split in places. The electricity then move down the tree to a thick root where it passed near some buried cables of a solar system. It then entered the cables and damaged some nearby inverters. The event even blew a rock out of the hole, uncovering the cables, inadvertently making it easier to find out what happened.