I am on the same quest. So far, it seems that a feasible, fairly light rig for overnights and short trips where you might want to perk up your phone and maybe a headlamp would involve a power bank and not a solar panel.

My favorite power bank for this niche usage is a Goal Zero micro Charge lantern which also functions as a flashlight, lantern (with two power settings) and a usb port for charging other items. Very limited capacity because the 'power bank" is an 18650 battery with a capacity of 2600 mAh....But probably OK for short trips.

You can get larger power banks and at some point it will make sense to throw in a solar panel. From what I have read, solar panels hung on your pack are not really all that effective.