The following layered semiconductors were given. Solar energy with the following

Question

The following layered semiconductors were given. Solar energy with the following structure of 435nm single wavelength was illuminated from the top floor. Each layer has enough thickness. 1) In Structure 1, does material C generate an absorption (excess carrier)? Give reasons for the answer. 2) In Structure 2, does material C generate an absorption (excess carrier)? Give reason 3) In Structure 3, does material C generate an absorption (excess carrier)? Give reasons for the answer. s for the answer Eg-5eV Eg-4eV C(Eg= 1.2eV) Eg-1.2eV Eg= 1.5eV C(Eg 2.0eV) Eg-5eV Eg-1.5eV C(Eg= 1.2eV) Structure 1 Structure 2 Structure 3

Explanation / Answer

As we know the incident photon energy of light is given by:

E= hv, where h is Plank's Coefficient and v is the frquency of light

we can write the above equation :

E= h(C/lambda), here h= Plank's Coefficient =4.16x10-15 eV.s, C= Speed of light= 3X108 m/s, lambda= wavelenth of light= 435nm= 435X10-9 m(given)

For calculating E putting all values what we have calculated.

we get, E= 4.16x10-15 eV.sX3X108/(435 X 10-9) = 2.86 eV

therefore this photon energy can be used for the materials have energy band gaps below than 2.86 eV

In all structures the photon energy is higher than band gap level of the material C, so the material C generate excess carriers in all the structures.

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