ABSTRACT
Early activity in solar PV was closely tied to curiosity, basic science, and fundamental understanding—with barely any consideration of its practical applications. Despite decades of observations of electrical currents’ affects by light, progress in this early period was extremely slow. It took 115 years from Becquerel’s discovery of the photoelectric effect in 1839 until Bell Labs demonstration of the first efficient solar cell in 1954. In between—in 1905—Einstein described light as packets of waves, or photons. If the photons contain enough energy to exceed a material’s band-gap, or activation energy, they will dislodge an electron, which is why experimenters were detecting a current in their photosensitive devices. This fundamental understanding led to the development of the p–n junction, a combination of two semi-conductor materials that could generate a current when exposed to light. Bell Labs exploited this phenomenon and announced the world’s first practical solar cell in 1954 with an efficiency of 6%. Commercialization quickly followed and the first commercial cell powered the Vangaurd-1 satellite in 1957. Additional niche markets followed including maritime buoys, oil rigs, and telecom repeater stations.
