More than a billion. About a zillion. PV is often cheaper than extending a utility connection to a remote location. PV panels are dangerous, so they must be placed in remote locations. PV only works when it can be located close to where the electricity is used.
Solar panels look cool sitting off by themselves.
More than 1000. More than 200,000. More than a million. Japan b. Europe c. Many materials are currently used to make PV modules.