id	author	title	date	pages	extension	mime	words	sentences	flesch	summary	cache	txt
work_7gfl5pcgirgmxcf3hp5jw4icla	Kevin J. Anderson	Photovoltaic Materials	1992	1	.pdf	application/pdf	1166	60	50	sources, including "clean and inexhaustible" solar power. Unlike electric generators, solar cells have no moving parts, thus The theory behind solar cells was first touched on in 1839 by the external battery to provide a positive potential, this cell produced an electric current when illuminated by visible light. solar cell had been made of copper and the photoelectric effect in selenium barrierlayer cells. later, however, did an engineer—Paul Rappaport in America—conceive of using silicon photovoltaic cells as relatively efficient cell capable of 6% energy conversion efficiency when used in direct sunlight. While selenium and copper-oxide photovoltaic cells use a semitransparent metallic semiconductor surface to create the necessary potential barrier, silicon solar cells use Current manufacturing techniques make silicon solar cells about 1 cm Until the early 1960s, silicon solar cells Solar cells are now frequently used in are possible only during days of total sunlight, solar cells are impractical in cloudy	./cache/work_7gfl5pcgirgmxcf3hp5jw4icla.pdf	./txt/work_7gfl5pcgirgmxcf3hp5jw4icla.txt