That's exactly my point. Efficient solar cells being mass produced cheaply will be world changing, but no one is going to try sticking one on a phone unless they're a little dim. You have a solar cell at your home/town center that you recharge at.

I am too lazy too look but I remember reading a story where an $80 or so solar panel system (with some sort of battery, no doubt) from China enabled villagers in Africa to turn a light on at night and maybe recharge a phone. Simple but life changing.

When you have very few things, people get creative. In USA for example for the most part mechanics change a car part with a new one, in the third world they open it up, fix and get another decade out of it.