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What is the function of a solar cell? Briefly explain its working and draw its I-V characteristic curve. |
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Answer» Solution :The function of a solar cell is to transform solar energy directly into electrical energy. A solar cellis BASICALLY a p-n junction which generates emf when solar radiations fall on the junction. In a solar cell no external bias is applied and the junction area is kept LARGE for more solar radiation to be incident. When light (with photon energy `hv gt E_(g)`) falls at the junction, electron-hole pairs are generated which move in mutually opposite directions due to the junction field. If no external load is connected of if the circuit of solar cell is open, electrons and holes are collected at the two sides of the junction giving a photo-voltage `V_(oc )`. When external load R is connected, a photo-current `I_(L)` flows. For R = 0, the current has a maximum VALUE `I_(sc)`, which is known as short circuit current. V-I characteristics is shown in figure. The graph is in the fourth QUADRANT because a solar cell not draw current but supplies current to the load. 
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