Question

(i) Why are Si and GaAs preferred materials for solar cells?(ii) Describe briefly with the help of a necessary circuit diagram, the working principle of a solar cell.

Answer 1

these materials are preffered because of their lower value of energy gap. SO that they can be activated using solar radiation. b) their V-I characteristics are similar to a semiconductor. ... And GaAS and Si are the semiconductors and preffered so.

A circuit diagram is a graphical representation of an electrical circuit. A pictorial circuit diagram uses simple images of components, while a schematic diagram shows the components and interconnections of the circuit using standardized symbolic representations.

Answer 2

The answers to the above questions are:--

(i) Si, Ga and As are preferred materials for solar cell because

• semiconductors with band gap close to 1.5 eV are suitable and ideal material for this purpose as all the three have band gap near to 1.5 with silicon with 1.1 eV GaAs with 1.43 eV so are ideal material for solar cells.                                                                  
• They also have high optical absorption and high electrical conductivity so are suitable for solar cells.

(ii) Working of solar cells is:--

• When light rays fall on the depletion layer the photons excite electrons valence band to conduction band, leaving holes in valence band.
• Field in depletion layer separates them and these electrons holes move in opposite direction.
• Electrons move towards n side and holes move towards p side, so the potential of p side increases and potential of n side decreases.
• When load resistance is connected between p type and n type,the current flowing from p ton type and current is proportional to intensity of illumination.
• Energy gap of solar cell is 1.5 eV.