| A seminar was conducted on renewable sources of energy, where Romilla gave an motivating speech on 'solar cell' to create awareness among students guided by her Physics teacher. |
| Read the above passage and answer the following questions : |
| (i) State the reason, why GaAs is most commonly used in making a solar cell. |
| (ii) What values are exhibited by Romilla? |
| (iii) How does photocurrent is produced by solar cells? |
Answer:
(i) For fabricating solar cell, incident photon energy must be greater than band gap energy, i.e. \[(hv>{{E}_{g}}).\] For GaAs, \[{{E}_{g}}=1.43\,eV\] and high optical absorption \[\approx {{10}^{4}}c{{m}^{-1}},\] which are the main criteria for fabrication of solar cell. (ii) Community service, scientific awareness and a good student. (iii) When photon of light \[(hv>{{E}_{g}})\] falls at the GaAs p-n junction, electron-hole pairs are generated near the junction and move in opposite directions due to junction field. A photovoltage will be produced between the top and bottom metal electrodes acting as positive and negative terminal producing photocurrent, supplies it to load connected externally.
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