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As a material transitions from the amorphous state to the fully crystalline state, the broad maximum sharpens up and other sharp peaks start to appear in the n(λ) and k(λ) spectra. This is demonstrated for the case of amorphous silicon progressing to poly-silicon and further progressing to crystalline silicon.
Amorphous silicon (a-Si) is the non-crystalline form of silicon used for solar cells and thin-film transistors in LCDs.. Used as semiconductor material for a-Si solar cells, or thin-film silicon solar cells, it is deposited in thin films onto a variety of flexible substrates, such as glass, metal and plastic.
Refraction at interface. Many materials have a well-characterized refractive index, but these indices often depend strongly upon the frequency of light, causing optical dispersion. Standard refractive index measurements are taken at the "yellow doublet" sodium D line, with a wavelength (λ) of 589 nanometers.
These parameters approximate amorphous silicon. [1] The Forouhi–Bloomer model is a mathematical formula for the frequency dependence of the complex-valued refractive index. The model can be used to fit the refractive index of amorphous and crystalline semiconductor and dielectric materials at energies near and greater than their optical band gap.
The refractive index of materials varies with the wavelength (and frequency) of light. [27] This is called dispersion and causes prisms and rainbows to divide white light into its constituent spectral colors. [28] As the refractive index varies with wavelength, so will the refraction angle as light goes from one material to another.
Crystalline silicon has a metallic luster and a grayish color. Single crystals can be grown with the Czochralski process. Crystalline silicon can be doped with elements such as boron, gallium, germanium, phosphorus or arsenic. Doped silicon is used in solid-state electronic devices, such as solar cells, rectifiers and computer chips. [1]
Silicon is transparent to infrared light with wavelengths above about 1.1 micrometres. [58] Silicon also has a very high refractive index, of about 3.5. [58] The tight optical confinement provided by this high index allows for microscopic optical waveguides, which may have cross-sectional dimensions of only a few hundred nanometers. [10]
Thin-film solar cells, a second generation of photovoltaic (PV) solar cells: Top: thin-film silicon laminates being installed onto a roof. Middle: CIGS solar cell on a flexible plastic backing and rigid CdTe panels mounted on a supporting structure Bottom: thin-film laminates on rooftops Thin-film solar cells are a type of solar cell made by depositing one or more thin layers (thin films or ...