I have solar lawn lights in my back yard that has failed after sitting in the harsh outdoor environment for several years. Their weakest point appear to be their NiMH batteries which I'm willing to replace. But some of them also have failed solar cells or crumbling internal structure, and replacing a battery won't bring those back. I'll have to buy new replacements. I went online shopping for solar lawn lights and failed to find an exact match. I expected this but it was worth a few minutes to look. If I wanted to maintain a consistent appearance, I should have bought a second box at the time and stash it away.

As soon as I had that thought, an echo of memory came up in the back of my head. I went looking in the cabinet where I might keep such things and... yes! I had that same thought earlier, bought a second box, and forgot about it until now.

Putting an old sun-beaten unit next to a fresh one out of the box provided quite the contrast. Both in their painted metal surfaces and in the condition of their solar cells.

Here's a close-up view of a fresh solar cell. I now know the clear top section is not glass, but I don't know much else beyond that. Someone more knowledgeable about solar cell construction can probably look at this and foresee all the ways it will break down with age and exposure.

What I have now reflects real world long duration outdoor exposure. The clear top layer has yellowed and developed a rough surface texture. And I can't tell if the outer edges have eroded or if the clear layer material has shrunk. I don't know if the white visible patches are in the clear top material or in the solar cell underneath. I do know this solar cell stopped producing power some time back and will have to be replaced by a new one.