Problem is the panels are framed in aluminium, which has scrap value as metal. As well the wire is copper so also has value. If somebody can get 50c US for stealing something off a wall, or off a rooftop, they will do it. Cardboard is worth money, and is something that people have been killed over, just to get 2kg of it.
Your panel would have to be a glass plate with amorphous film on the back, laminated with a plastic membrane on the rear, with a frame made from GRP composite. The wire would have to be copper coated steel, with fixed connectors. Electronics inside would have to use minimal copper on the board, and the battery would have to be a 12V 7Ah SLA battery ( very common here and affordable to people) to be relatively theft proof. Cost would have to be under $30, to make it affordable to people yet worth the manufacturing cost.
As I am currently in the middle of replacing manhole covers, stolen because the cast iron is worth something as scrap metal ( and the thieves get a very low price because the unscrupulous yard owners know they are stolen but still take them at a big profit), and am using GRP composite covers and frames, so as to have minimal scrap value. The thieves might get $3 for the one they stole, but a replacement cast iron is $300, excluding the fitting costs, and the GRP one was cheaper at $200, including courier charges from half way across the country. Thus I am doing the labour work, as there is no budget for this, and insurance is not worth claiming as the excess is $400, and the loss of the no claim is worth more. Thus me out with a jackhammer, chisel and pickaxe, and mixing some tilefix and bonding liquid to improve the adhesion and smooth off the process.