Let's Make Robots!

Driving a motor with solar cells (without a solar engine)

What I want to do is this: I have a basic bicore hooked up to a vibration motor.  He kind of flops around, but it isn't totally random.  Anyway, I was wondering how I could power him with some solar cells that I have without using a solar engine.  If that's possible, I would really like to hear some ideas.