Regardless if you select solar or dyno I'd recommend charging into a power bank rather than the phone directly.

In my experience, if you have a power source that is intermittent this will tend to cause the phone to turn its screen off and on repeatedly when the power "appears" or "disappears". This extra screen time can burn off a significant amount of that new power.

The power bank is also more flexible in providing a buffer, you can leave on your trip fully charged and also take advantage of power outlets when they are available.

Having power in the separate battery is useful too because smart phones sometimes get caught up in a background process or hunting for service and will burn a battery much quicker than normal. This always seems to come up more while travelling. Having the power bank keeps energy in reserve if you need to make an emergency call but your phone has wasted its power unexpectedly.