When was Solar Cell Technology developed?

Modern solar cells with practical efficiency were invented in the early 1950’s and has been used to power satellites since 1959.  Their popularity in terrestrial use came in the mid-70s and was mostly for remote telecommunications, navigational aides and other remote industrial use which included the microwave, TV, radio and cellular repeater stations.  Since the mid 80s they’ve been used to power urban applications such as roadside emergency telephones and traffic signs.  With prices steadily dropping, they are now becoming more and more affordable for urban or remote homes and businesses.