Since you have to backpack it, it doesn't lend itself to be convenient, other than already made or get an idea from what you see.
Google using these keywords: solar backpack setup
You'll find already made setups. I suggest that because whatever is required is already there. If you decide to make you're own, then find a typical folding clam-type charger and use cabling to get what you need and regulator. Solar setups are all over the place but very few are packable, maybe luggable is more the term. On top of that it has to be "durable" in order to take the bumps and grinds of traveling and brush, etc. and be weather-proof, etc.. Also, take my advise don't ever let your battery run down too low, you find the weakness of the amps to push or turn-ON the charging unit to the device may need a little juice left in order to get turned-ON. Which leads to it all about the "amps" so it better be rated for whatever use you plan to use it for or be higher. The minor electronics should not be tasked to work at its extremes either hi/low ends because they are just too simple and can be burnt out.
I use solar only to keep batteries "topped" for my tractor or vehicles left outside for long periods(winter), friends use for boats. Thus, check any outdoor RV/boating/camping vendors for possible hints/clues/tips besides actual solar devices for sale.
one of my friends bought a solar panel and put together a solar phone charger.
As you can tell, it could be very useful (I go camping) and I'd like to put together something similar.
What I'm thinking is a solar panel to strap on my backpack, with a battery in one of the unused outer pockets. either USB at 2.1 amps or 12V DC, with the latter being better because I can buy a simple inverter to use with a laptop.
I assume that 12V DC would require a larger battery with a much higher risk, so I'm okay with USB.
Currently, I have a multimeter and an old USB extension cable.
What I'm really asking for is design help. I want to buy a solar panel and a battery to asseble a DIY solar USB charger for my phone. I also have a new 12000mah battery that performs rather well, but won't last forever in an emergency (also not homemade).
I want a real project other than my homebuilt PC to be proud of and show off. my family was impressed with the homebuilt PC, so I wonder how this project will look in my college essay for an engineering school.