1839 French physicist Edmond Becquerel's experiments with 'wet cell' batteries show increased voltage when the batterie's silver plates are exposed to sunlight.

1877 Adams and Day observe variations in the electrical properties of selenium when exposed to light.

1883 Charles Edgar Fritts constructs a selnium solar cell. However efficiency is very low. less than one percent of light energy falling on the cell is converted to electrical energy.

Early 19th centuary Various physicists further understanding of the fundamental properties of materials and of radiation.

1948 Bardeen and Brattain's research leads to the first transistors. Devices that use semiconductors in crystalline form that have specific impurities added in order to give them spec ific electrical properties.

1950's Scientists at Bell Labs apply the technology used in the new transisitors to produce much more efficent solar cells.

1958 Solar cells are used succesfully in Space satelite Vanguard I, demonstrating their potenital.

Since then solar cells have been getting more efficient (many commercially available ones have 17% efficiency and costs are coming down. Only recently has this now pushed them into the bracket where they are affordable for many domestic applications. We all are lucky enough to now reap the benefit of technology that has been steadly devolped over the last century and a half.   Make the most of it!