score:4
Yes, Tom is right, you'll get more out of Google.
Waka-Waka.com provides an example of such a common use solar panel as you might be a looking for.
Most gers though, I found on our trip through central Mongolia, have electricity through solar panels/car batteries, and the locals are really friendly; I can only imagine them being helpful when asked for some power.
I would recommend turning off your phone when not used and, if you were planning to take pictures with your phone, to bring a separate camera as well as your phone. A separate camera provides you with another battery, and typically uses that charge more efficiently (as there are no background processes running, like connecting to/searching for a mobile network).