I bought some surplus solar panels years ago but only used a small number of them in a test to run an attic cooling fan for a year or so. The test worked pretty well but one panel broke in two probably after it got hit by a piece of hail.
The panels are about 8 inches by 8 inches and consist of a glass panel with a aluminum foil back with some sort of coating. The directions that came with the panel said scrap the coating off the foil side to expose the metal on the edges and the attach a U shaped metal piece on either side of the panel. One goes to the positive side and the other to the negative. Next solder the wires to the these metal pieces to get the power.
I looked for a better method and tried to find a conductive epoxy that would allow the wires to attach to the plate. I never found one that was cheap.
I came up with another method for attaching the conductors. Use copper foil tape from 3M that sticks to the aluminum and then solder the wires to that. See the picture for a better explanation.