nanoHUB.org - Questions and Answers: is it possible to apply and use brass instead of aluminium in organic solar cells?
In general, the most important properties of an organic solar cell electrode material are the conductivity and the work function. Aluminum works well because it has high electronic conductivity and a work function of around 4.3eV which matches well with typical acceptor materials such as PCBM. If you are considering using any other metal or alloy you will need to keep these properties in mind.