The article by [Kris De Decker] tells of George Cove and includes a picture from 1910 of the inventor standing next to what looks suspiciously like a solar panel (the picture above is from a 1909 issue of Technical World Magazine). His first demonstration of the technology was in 1905 and there is a picture of another device from 1909 that produced 45 watts of power using 1.5 square meters with a conversion efficiency of 2.75%. That same year, a new prototype had 4.5 square meters and used its 240-watt output to charge 5 lead-acid batteries. The efficiency was about 5%.
Of course, 5% doesn't sound so great today. But to put it in context, the original Bell solar cells in 1954 had about 6% efficiency. Oddly enough, Cove didn't set out to build solar electric generators. He was actually trying to build a thermoelectric generator to produce electricity from a wood stove.