How to wire this solar cell?

Hey there!
I'm a beginner in solarbots and I just acquired a couple of paper thin solar cells that are paper thin and about 5 by 5 cm. The backside seems to be plain paper or something. I already broke one! I can't figure out how to wire or solder it, that is where the plus and minus poles are. Can someone give me a hint?
Thanks!
Sebar

Picture of How to wire this solar cell?
sebarr (author) 6 years ago
I just tried soldering to the big stripe and the back and it worked. I wired 4 of those in series and glued them in a CD case for protection. But hell those things are hard to solder! It came off a hundred times! Any ideas why this is and how to prevent it?
Kiteman6 years ago
Are those lines metallic? Could they be the contacts you need to solder to?
sebarr (author)  Kiteman6 years ago
I find it hard to tell... the broad line in the middle seems metallic, but the fine ones are white. Could it be I just have to pick any fine line + the broad one?
Kiteman sebarr6 years ago
I would get hold of a multimeter and prod around to see where to connect it.