Solar panels have a very large capital expense, they are cheap in the long run, but they are not feasible for running industry in poor countries.
Raw, ready-to-mount, single-crystal panels are down to $0.50/watt now, in pallets of ten at about 350 watts each, and have good lifetimes. Even adding the control electronics and batteries for nighttime and bad weather power, and replacing the batteries periodically, that's cheaper than building and running coal plants and their distribution infrastructure (even at third-world labor prices).
The control electronics is mostly semiconductor devices and still benefiting from Moore's Law. Solar panels are still improving, as are batteries (following their own Moore's Law like curves.) Solar has a factor of several in efficiency yet to go, and lot of room for cheaper manufacture. Batteries are pretty efficient, but still have lots of room for improvement in charge/discharge rates, lifetime, and manufacturing cost. Coal plants, meanwhile, are already close to as efficient and cheap to run as they can get. So solar will continue to improve its lead.
The main remaining advantage to coal plants is grid power gives suppliers an ongoing revenue stream and a captive market, while solar provides only an occasional capital purchase.
(But why do you never hear about the greenhouse effect of solar panels?)