Q.Explain the construction and working of solar cell.

[!TLDR] A solar cell is a large p-n junction with a thin, front-contacted n-side facing the sun; incident light generates carrier pairs that the junction field separates, building up a voltage that drives current through an external load. [!ANSWER] Construction: thin n-side (front contact/antireflection coating) facing light, over a thick p-side (back contact). Working: photo-gene …

CONSTRUCTION (Fig. 16.13a): a solar cell is a large-area p-n junction. Its n-side is made THIN and faces the incoming solar radiation, coated on its outer face with an antireflection coating that doubles as the electrical FRONT CONTACT -- this coating passes visible light through to the junction while reflecting away IR (heat) radiation, protecting the semiconductor's temperature-sensitive electronic properties. Its p-side is made relatively THICK, forming the bulk/back of the cell, with a solid conducting BACK (rear) contact on its outer face. The material chosen must be photosensitive (able to absorb light and promote electrons to a higher energy state) and must allow those higher-energy electrons to be extracted usefully into an external circuit. WORKING: (1) incident photons with energy greater than the material's band gap generate electron-hole pairs within the depletion region; (2) the junction's own built-in electric field immediately separates these pairs (Fig. 16.13b) before recombination can occur -- sweeping the photo-generated electrons into the n-region (where they become majority carriers) and the photo-generated holes into the p-region (where they become majority carriers); (3) these separated charges accumulate on the two sides of the junction, building up a voltage across the cell; (4) when an external load is connected across the cell's terminals, this accumulated charge drives a current -- the light-generated (photo-generated) current -- through the load, delivering usable electrical power. If the junction's field did NOT separate the carriers this way, the photo-generated electrons and holes would simply recombine with n …

Describe the layered p-n junction structure (thin n-side/front contact facing light, thick p-side/back contact behind), then trace the four-step working sequence: photon absorption, field-driven carrier se …

Omitting the role of the junction's built-in electric field in SEPARATING the photo-generated carriers -- without this separation step, simply generating electron-hole pairs would …