Nice idea, but...
...you can't exactly use and charge the netbook at the same time, the back of the screen has to be pointed directly at the sun to gain maximum power meaning looking at the front of the screen will be somewhat difficult because you'll be looking in the direction of the sun.
A detachable solar panel with retractable cable may be the better option, that way the panel could be foldable, doubling the area of light captured.