Landolt-Börnstein - Group VIII Advanced Materials and Technologies
4.2 Photovoltaic power generation
This chapter photovoltaic power generation describes the principles of photovoltaic cells, potential and relevance of photovoltaic solar energy, physics of solar cells, and solar cell technology. The conversion of solar radiation into electricity occurs by the photovoltaic effect. The main motivation for developing solar energy is the desire to reduce dependence on depletable fossil fuels with their adverse effect on the environment. Schematic diagram of pn-junction solar cell is shown. Maximum conversion efficiency for different semiconductors versus band gap for T = 300K, examples of the daily and seasonal fluctuations of radiation, and the I/V characteristics with and without illumination are illustrated. Silicon material, cell and module technology, production of pn- and pp-junctions, oxidation process, electrical contacts, antireflection technologies, and thin film materials such as copper indium diselenide and related compounds, and cadmium telluride are described. Further development of this technology towards even lower cost proceeds in two major directions, ribbon technology, and crystalline silicon thin films. The world market for the different applications, their past development, and forecast for the next decade is listed, and a survey of all PV applications is shown. A photovoltaic power supply for standalone systems in its simplest form consists of the solar generator, a charge controller, energy storage, and a DC/DC voltage converter. The fastest developing application is decentralized grid-connected systems.