Conjugated polymer-based organic solar cells.

Photovoltaics (PVs) consists of the harvesting of energy from sunlight and its conversion into electrical power. This technology is being increasingly recognized as one of the key components in our future global energy scenario. Limited fossil fuel resources and steadily increasing costs of supplying fossil fuels to the market induce a natural limit where renewable energies will begin to kick in as major energy suppliers. In addition, the detrimental long-term effects of CO2 and other emissions from burning fossil fuels into our atmosphere underscore the multiple benefits of developing renewable energy resources and commercializing them. The worldwide photovoltaics (PV) industry reached a cell/module production of 1200 MWp in 2004, exhibiting an average annual growth of 40% over the last 5 years [1]. The same year, this market recorded a spectacular increase of 58.5% (US$ 5.8 billion), making the industry one of the fastest growing worldwide at present. As shown in Fig. 11.1, this development is not only in Japan, but also in Europe and the USA. Besides, most Japanese, USA and European forecasts seem to agree on one point: This trend is expected to last at least for the next 30 years to come [1]. A significant capacity of about 200 GWp is forecast to be operational around the globe in 2020. This number is the equivalent of 200 state-of-the-art nuclear power plants. PV technology is only one of many alternative renewable energies such as wind, biomass, and water. However, though all of these technologies are expected to contribute significantly to the world’s energy supply in the next century, PVs possesses three key properties which make it unique: 455