Google solar powered garden lights, there will be plenty of schematics im sure.
There is a way of using the solar panel as a light detector, so that it charges and no power is given to your circuit when there is light, and when there is no light it stops charging and gives power to your circuit.
I should crack open our little garden lights. I know that its very simple to do that.
You might have to have a pretty big solar panel to turn a motor all night long though.