A solar cell is to be fabricated for efficient conversion of solar radiation to emf using material A. The solar cell is to be mechanically protected with the help of a coating using material B. If the band gap energy of materials A and B are `E_A` and `E_B` respectively, then which of the following choices is optimum for better performance of the solar cell.

Options

A. `E_A = 1.5 eV, E_B = 5 eV `
B. `E_A = 1.5 eV, E_B = 1.5 eV `
C. `E_A = 3 eV , E_B = 1.5 eV `
D. ` E_A = 0.5 eV ,E_B = 5 eV `

Answer

A

Explanation

Generally we want the electron to cross energy gaps in material A.
Not in material-B because its just covering. And Eg in the A should not be very small otherwise there will be huge heat loss because of large difference in `E_g` and energy of incident photon