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The World of Silicon Solar Cells

Material Choices in Silicon Solar Cells

Silicon solar cells are predominantly made from silicon wafers, which come in two main types: single-crystalline and multi-crystalline. Single-crystalline wafers offer superior material properties but come at a higher cost. The crystal structure of crystalline silicon is ordered, with atoms arranged in a specific pattern. While crystalline silicon shows consistent behavior, its production processes are meticulous and slow, making it the most expensive silicon option.

Crystal Orientation and Doping

In single-crystalline silicon, crystal orientation is denoted by Miller indices, with specific crystal planes indicated by parentheses, such as (100). The cubic symmetry of silicon results in equivalent planes like (100) and (010) collectively represented as {100}. Crystal directions are identified using square brackets, for example, [100], and collectively referred to using triangular brackets, <100>.

For solar cells, the preferred orientation is <100> as it allows for easy texturing to create pyramids that reduce surface reflectivity. However, certain crystal growth methods, like dendritic web <111>, may yield materials with different orientations.

Single crystal wafers often feature flats to indicate wafer orientation and doping. The SEMI standard is commonly used for this purpose.

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