Thickness, composition and properties of solar cells
Originally developed to provide electrical power for orbiting space satellites in the 1960s, photovoltaic (PV or solar cell) technology is now mostly used for grid-connected utility power generation. In typical form, solar cells are packaged in photovoltaic modules and are often connected in multiples, as solar photovoltaic arrays, to directly convert energy from the sun into electricity. The term photovoltaic denotes the unbiased operating mode of a photodiode in which current through the device is entirely due to absorbed light energy.
By far, the most prevalent bulk material for solar cells is crystalline silicon. Cadmium telluride (CdTe), copper indium gallium selenide (CIGS) and amorphous silicon (A-Si) are three thin-film technologies often used as outdoor photovoltaic solar power production. In addition, other photovoltaic technologies span from light-absorbing dyes (DSSC) to organic/polymer and silicon thin-films.
X-ray fluorescence (XRF) is typically used to measure the thickness and composition of metal-containing thin-film layers as part of production process control. X-ray diffraction (XRD) and X-ray reflectometry (XRR) are used in R&D to physically characterize layer properties like roughness, density, porosity, and crystal structure.