Earth solar cells are thick and heavy mostly because of the protective glass, frames, etc.

The actual silicon is under a millimeter thick, and presumably could be made even thinner.

On Mars, with a super thin atmosphere, there may be no need to protect the cells. Just laying plain cells on the ground might prove cheapest. Sure, they'd be super fragile (imagine potato chips the size of a person and how hard they would be to lay flat on the ground without breaking) and you'd probably have to come up with special techniques to lay them whilst breaking as few as possible.

Wiring is probably the next heaviest component. But with no atmosphere, there is no need for wires to be waterproof or have insulation. Wires could be bare aluminium.