As there are no power points on Mount Kilimanjaro, a solar charger is your best option if you want to be able to power up your devices during your entire climb.
A solar charger provides an endless supply of electricity as long as the sun is shining. However, the weather on Kilimanjaro can be erratic. Therefore, it is potentially interesting to combine a solar charger with a battery pack.
Also, keep in mind that the panels need direct sunlight to be able to charge your devices. While you walk, you are moving and potentially changing direction which disrupts and, as a result, slows down the charging process.
When choosing a solar charger, do not only pay attention to how many Watts of power they offer. You should also pay attention to their size and weight. These are important aspects to consider since you can only take a limited amount of weight on your climb.