You should state the voltage and current capability of your project; there is plenty of choices like the electric bicycles hub motors.
Here is some: http://www.electricscooterparts.com/motors.html
It's very challenging to capture enough solar energy with a vehicle, to move that same vehicle. Everything in between the sunlight and the road must be carefully integrated to get a useful result. High schools and college engineering departments engage in competitions to do this, and their results should help you no matter what scale you are working at.