Which part are you stuck on?
Have you decided how the tracking will work and how you'll drive the wiper motor?
For tracking, you can use LDRs or other light sensors. Use LDRs placed in multiple positions and take readings of light intensity using the LDRs. Whichever LDR gives highest reading consistently over a defined period of time is the direction towards which you must move the panel.
For control of the wiper motor, use an H-bridge controlled by the microcontroller. You can thus control the direction as well as speed (if needed) of the wiper motor.
Hope this helps.
Tahmid.