Photovoltaics materials and devices

The current status of research and technology of photovoltaic materials and devices are reviewed briefly. The review includes a discussion of fundamental concepts underlying the operation of photovoltaics. Photovoltaic power sources are the best opportunity to provide energy for the world of tomorrow. The technology is changing rapidly and the price of power produced by photovoltaics is dropping while the industry is growing at 25% or more per year. Alternative renewable energy sources will provide some of our energy but photovoltaics are the most efficient at converting sunlight to useable power. A variety of technologies are available including those operating under unconcentrated and concentrated sunlight. Single junction devices are the most common, while multijunction designs are more efficient. Much of the progress in some technologies in recent years has been due primarily to a shift from single junction to multijunction devices. The performance of the devices can be understood based on conventional mathematical descriptions of diodes and the trapping and recombination of carriers. Novel technologies such as organic photovoltaics, nanoparticle devices, and photoelectrochemical cells are also under development, although these face significant obstacles. Production methods for conventional technologies include bulk crystal growth methods such as the Czochralski method and the more common thin film deposition methods are described.