Question

Solar cells are given antireflection coatings to maximize their efficiency. Consider a silicon solar cell (n=3.50) coated with a layer of silicon dioxide (n=1.45). What is the minimum coating thickness that will minimize the reflection at the wavelength of 700 nm where solar cells are most efficient?

Answer 1

Answer:

t = 121 nm

Explanation:

given,

silicon solar cell = n = 3.50

layer of silicon dioxide = n = 1.45

minimum coating of silicon layer thickness = ?

wavelength of reflection = 700 nm

using condition of destructive interference

$2nt = (m+\dfrac{1}{2})\lambda_{vaccum}$

$2nt = (m+\dfrac{1}{2})\lambda_{vaccum}$

n is refractive index of silicon

m is order of fringe

λ is wavelength

m = 0,1,2..

$t = \dfrac{(m+\dfrac{1}{2})\lambda_{vaccum}}{2n}$

for minimum m = 0

$t = \dfrac{(0+\dfrac{1}{2})\times 700}{2\times 1.45}$

t = 121 nm

hence, the minimum thickness of the coating is equal to t = 121 nm