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Solar cells are made of the semiconductor that has a band gap close to:

Solar cells are made of the semiconductor that has a band gap close to: Correct Answer 1.5 eV

CONCEPT:

Solar Cell:

  • A solar cell is basically a p-n junction that generates emf when solar radiation falls on the p-n junction.
  • It works on the same principle (photovoltaic effect) as the photodiode, except that no external bias is applied and the junction area is kept much larger for solar radiation to be incident because we are interested in more power.
  • A p-Si wafer of about 300 μm is taken over which a thin layer (~0.3 μm) of n-Si is grown on one side by the diffusion process.
  • The other side of p-Si is coated with a metal (back contact). On the top of the n-Si layer, a metal finger electrode (or metallic grid) is deposited. This acts as a front contact.
  • The metallic grid occupies only a very small fraction of the cell area (<15%) so that light can be incident on the cell from the top.
  • The generation of emf by a solar cell, when light falls on, it is due to the following three basic processes: generation, separation, and collection:
    1. Generation of e-h pairs due to light (with hν > Eg) close to the junction.
    2. Separation of electrons and holes due to electric field of the depletion region. Electrons are swept to n-side and holes to p-side.
    3. The electrons reaching the n-side are collected by the front contact and holes reaching the p-side are collected by the back contact.
  • Thus p-side becomes positive and the n-side becomes negative giving rise to photovoltage.
  • When an external load is connected a photocurrent flows through the load.

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EXPLANATION:

  • We know that solar cell is made of the semiconductor that has a bandgap close to 1.5 eV. Hence, option 1 is correct.

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