[yk]

The cost of solar is dropping fast, and for the time being the largest emitters per capita are developed economies. So we should start in developed economies, were we can spare the effort and then work on developing economies.

On the poorest economies, quite a few of them are close to the equator were solar looks very good, plus a rather nice thing about solar is, that it scales very well. In countries were malnutrition is still a wide spread problem, a solar powered lamp enables people to work outside of daylight hours, and a solar oven prevents them from sitting in kerosene fumes while cooking. This are small appliances with a rather minimal footprint, but improves their lives in ways it is hard to imagine for us, who are just used to always having electricity.

Plus, there is not reason to assume that they have to take the same development path as the developed economies. They have the second mover advantage, that is developing economies can avoid the problems western industrialization did create, simply because they can see these problems in the west.