Physical Limitations to Photovoltaic Energy Conversion

This is a collection of papers from a seminar held in October 1989 to deal with the physical limits of the photovoltaic solar energy conversion and aims to determine the limits of efficiency of solar cells. An introductory chapter analyzes the efficiency of a solar cell and studies the role of light confinement. The following chapter presents the physical bounds of light concentration, resulting from the conservation of the space of phases, but also underlines how the resonance effects based on the wave nature of light can lead to high luminous intensities in certain structures. The book then discusses the limits of absorption of light by a given cell volume and studies the confinement of light in external cavities, studying the conditions for maximal light absorption. The thermodynamic treatment of an ideal solar cell is then considered and the limits of efficiency of cells under radiative recombination are examined, including aspects related to the restriction, by angular, spatial or spectral limitations, of the interchange of luminescent photons with the surroundings. A general description of the different mechanisms of recombination in solar cells, which includes simple formulas that allow us to guess the order of magnitude of the recombination mechanisms in materials of which we have little information, is included. As is an analysis of the surface recombination mechanisms, particularly in the interface Si-SiO2.