Question

(a) In the following diagram, which bulb out of $B_1$ and $B_2$ will glow and why?
(b) Draw a diagram of an illuminated p-n junction solar cell.
(c) Explain briefly the three processes due to which generation of emf takes place in a solar cell.

Answer 1

A) In the diagram, daiod $D_1$ is in forward bias and daiod $D_2$ is in reverse bias, So current will flow through $D_1$ and $D_2$ will not allow flowing the current, So bulb $B_1$ will glow and bulb $B_2$ will not glow.

C)When the photodiode is illuminated with light, with energy greater than the energy gap of the semiconductor, then electron-hole pairs are generated due to the absorption of photons, in or near the depletion region. Due to the electric field of the junction, electrons and holes are separated before the recombine electrons reach n-side and holes reach p-side.Electrons are collected on n-side and holes are collected on p-side giving rise to an emf. When connected to an external load is current flows, whose magnitude depends on the intensity of incident light.

The photodiode can be used as a photodetector to detect optical signals.