This is my take on a already well documented little project. Very simple to make and a good introduction to electronics and solar powered stuff. Works just fine too. You need to generate 5-6V to charge a phone.
You will need:
Solar panels. I used 2 panels. (3V I think )
5V voltage regulator
USB female jack/connector
Epoxy or hot glue
Step 1: Bits & Pieces
The regulator keeps the power output to 5v.
Step 2: A series of solar panels
Step 3: Solder it all together
The positive wire from the solar panels goes to the LEFT pin of the regulator. (mine is upside down in the photo)
The negative wire from the panels goes to the MIDDLE pin of the regulator and is also connected to the RIGHT pin of the USB plug. (Again, mine is upside down in the photos)
Then connect the last pin of the regulator to the other outside pin of the USB connector.
The 2 middle pins are not needed.
If you follow my pictures it will be OK....
Step 4: Glue
Next time I would make it so that the 2 panels hinged in some way so that it could fold together.