Question

In solar cells, a silicon solar cell $(\mu =3.5)$ is coated with a thin film of silicon monoxide $SiO(\mu =1.45)$ to minimise reflective losses from the surface. Determine the minimum thickness of $SiO$ that produces the least reflection at a wavelength of $550nm$, near the centre of the visible spectrum.

Answer 1

Given $x=550nm$

$SiO\left(\mu \right)=1.45$

Solar Cell $\left(\mu \right)=3.5$

To find,

Thickness$\left(t\right)=?$

Since the reflection is least when rays $1$ and $2$ meet the condition for destructive interferance.

Both rays undergoes ${180}^o$ phase change on reflection .The condition for a reflection minimum is therefore $2\mu t=\frac{\lambda }{2}$

$\Rightarrow t=\frac{\lambda }{2\left(2\mu \right)}=\frac{\lambda }{4\mu }$

$\Rightarrow t=\frac{550}{4\left(1.45\right)}=\frac{550}{5.8}=94.82nm$

So, the mnimum thickness of $SiO$ that produces the least reflection at a wavelenght of $550nm$ is $94.82nm$