Semiconductors such as silicon are used to fabricate solar cells — devices that

Question

Semiconductors such as silicon are used to fabricate solar cells — devices that generate electricity when exposed to sunlight. Solar cells are coated with a transparent thin film, whose index of refraction is 1.46, in order to minimize reflective losses from the surface. A silicon solar cell (index of refraction 3.5) is coated with a thin film for this purpose, sd in the figure.

1) Find the minimum film thickness that produces the least reflection at a wavelength of 578 nm.

Answer in units of nm to 6 significant digits! Please show work!

Explanation / Answer

the reflection is least when rays 1 and 2 in given figure meet the condition for destructive interference is             2nt = /2    .............. (1) where , t = thickness of the film             = wavelength = 578 nm             n = refractive index of transparent thin film = 1.46 therefore , thickness t = / 4n                  = 578 nm / 4*1.46                  = 98.9726 nm

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