The photovoltaic effect was observed as early as 1890 by Henri Becquerel, and was the subject of scientific inquiry through the early 20th century; Albert Einstein's only Nobel Prize, in fact, arose from solar power research.
In 1954, Bell Labs in the United States introduced the first solar photovoltaic device that produced a useful amount of electricity, and by 1958, solar cells were being used in small-scale scientific and commercial applications (especially for the space program).
The energy crisis of the 1970s saw the beginning of major interest in using solar cells for power here on Earth, but prohibitive prices (approximately 30 times current prices) made large scale applications unfeasible.
However, industry developments and research during this period made PV feasible for remote applications (especially for the telecommunications industry), and a cycle of increasing production and decreasing costs began which continues today.
The new millennium has seen PV become cost-effective in a rapidly growing number of areas as research and production advances continue everyday. Global PV market growth has averaged a stunning 25%+ annually over the last 10 years, with worldwide growth rates for the last 5 years well over 35% (meaning installed power doubles every 4 years or less). However, this rapid growth is from a very small base; PV still accounts for a small percentage of electricity generation worldwide.
Given appropriate policies, the coming years will continue to see rapid increase in the use of PV for homes and businesses, including the increased usage of new commercial systems of 500,000 watts or more, as well as small, standardized systems for rooftops, and attractive "building-integrated" devices in commercial buildings. The "virtuous cycle" of increased sales volume and decreased prices will continue to drive itself, and attempts to bring electricity to the developing world will frequently employ solar as the lowest-cost alternative. New, next-generation PV materials currently under research may bring dramatic, unexpected decreases in price.
Source: Solar Energy Industries Association