Smartphone is pretty much the only thing for me to consider in this regard. It's typically my camera and GPS and book reader and ...
I did carry a separate GPS last year, but lithium AA backup batteries for this were quite light. Ditto headlamp, a lithium spare isn't heavy. Ditto an MP3 player, I've carried one, but a single AAA battery backup is light, and if I run out of battery power on that temporarily it's not a big deal.
For my primary device, it's not difficult to find a smartphone with replaceable batteries and just carry spare batteries and a wall charger. I used and sort of liked a solar charger in California on the PCT (for my smartphone), but wouldn't go that route again. For the latter part of the trail and for more recent long trips I've since become convinced that I can do almost any trip better just with one or more spare batteries, and a wall charger if the trip is one where I resupply in towns or the like along the way.
Bottom line for me is that the cost, inconsistency, time required to mess with it on trail, "fiddle factor", all make me disinclined to attempt to recharge with solar on a backpacking trip. I'm sure there are situations where it makes great sense, but not so much for my style of hiking.