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 1.34, 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.

Find the minimum film thickness that produces the least reflection at a wavelength of 606 nm. Answer in units of nm.

Answer 1

$\lambda$ = wavelength = 606 nm = 606 x 10^-9 m

n = 3.5

for destructive interference , the condition is

2t = (m + 0.5)( $\lambda$ /n)

since m =0

2t = $\lambda$ /2n

t = (606 x 10^-9 ) / (4 x 3.5)

t = 43.286 nm