Tom Markvart, School of Engineering Sciences,
University of Southampton, UK
Luis Castaner, Universidad Politecnica de Catalunya,
Solar cell modelling is fundamental to a detailed understanding of the device operation, and a comprehensive model require a detailed knowledge of the material parameters. A brief overview of the semiconductor properties relevant to solar cell operation is given in this chapter, including the semiconductor band structure and carrier statistics, transport and optical properties, recombination processes, material aspects of radiation damage to solar cells in space and effects observed under heavy doping, with special attention given to the properties of hydrogenated amorphous silicon. The principal semiconductor parameters encountered in photovoltaic applications are summarised in Tables 1 and 2. The refractive indices of materials used for antireflection coating can be found in Table 3.
Numerous computer programs that use the material parameters to model solar cell operation have been developed over the years, and several are now available commercially:
• PC1D developed by P. A. Basore and colleagues at the University of New South Wales, Australia, is the standard one-dimensional simulator used by the PV community.
• ATLAS, a Device Simulation Software by SILVACO International, uses physical models in two and three dimensions. It includes the Luminous tool which computes ray tracing and response of solar cells. It allows the use of monochromatic or multi-spectral sources of light.
• MEDICI by Technology Modelling Associates models the two-dimensional distribution of potential and carrier concentration in a semiconductor device. It also includes an Optical device advanced application module where photogeneration can be computed for multi-spectral sources.
Some programs are available free of charge. These include, for example, SimWindows which can be downloaded from http://www-ocs. colorado. edu/ SimWindows/simwin. html.
A discussion of the main principles of the numerical techniques can be found in specialised texts which deal with the modelling of solar cells (see, for example, the review ) or with the modelling of semiconductor devices in general .