Question

List two advantages of solar cells.

Answer 1

Solar Cells

1. A solar cell is a pn-junction diode that converts sunlight directly to electricity with large conversion efficiency.
2. When a pn-junction diode is exposed to sunlight, the incident photons create electron-hole pairs in both p- and n- regions, of the junctions.
3. The generated electron-hole pairs over a small distance from the junction move to the space charge region $X$ through diffusion.
4. Then the strong electric field existing in the $X$ region separates the electron-hole pairs.
5. The electrons in the p-region slide down the barrier potential to move to the n-region.
6. Similarly, the holes in the n-region move towards the p-region.
7. In an open-circuit condition, the accumulated electrons and holes in the two sides of the pn-junction diode produce an open circuit voltage $V_0$.
8. If a road resistance $R_L$ is connected across the diode, a current will flow through the load.
9. The magnitude of current through $R_L$ is directly proportional to the light intensity.

Advantages of Solar Cell

1. There is an unlimited source of energy, from the sun, for the working of a solar cell.
2. They use renewable energy and hence is very good for the environment.
3. Solar cells do not have any maintenance costs once installed.