Photoelectrics

Hey, can anyone please explain the difference between work function and energy band gap for semiconductors such as silicon? I understand that they both are significant as to the type of EM radiation that PV cells can absorb, but I don't understand why they have different values? Thanks so much

Hey, can anyone please explain the difference between work function and energy band gap for semiconductors such as silicon? I understand that they both are significant as to the type of EM radiation that PV cells can absorb, but I don't understand why they have different values? Thanks so much

Hello and welcome to TSR.

Energy bands are the quantum energy levels allowed for electrons associated with any given atom. i.e. the shell distribution of electrons obeying the Pauli exclusion.

Thus energy absorption to promote an electron to a higher energy band can only be accomplished by photons of sufficient energy. (E=hv)
Photons are emitted when electrons drop energy bands and those photons are quantised to have a wavelength equivalent to the energy band-gap.

The definition of the work function is the minimum energy required to remove an electron from the highest filled level in the Fermi distribution at absolute zero such that it is STATIONARY at a point just outside the solid where no other field exists. i.e. to remove an electron from the surface of the material.

So far so good.

Extend the concept of energy bands to include a conduction band. i.e. electrons acquiring sufficient energy to be promoted out of the valence band so that they become free of the parent atom and able to drift within the lattice.

The band gap between the valence and conduction bands is markedly different for conductors, semiconductors and insulators and also temperature dependent.

Semiconductors have the property that some electrons will acquire enough thermal energy to enter the conduction band at room temperature. Thermal emission occurs.

The photoelectric effect is such that if the absorbed photon has greater energy than the work function then photoelectric emission will occur.

Would it be worth mentioning the equations for his favour?

Hey, can anyone please explain the difference between work function and energy band gap for semiconductors such as silicon? I understand that they both are significant as to the type of EM radiation that PV cells can absorb, but I don't understand why they have different values? Thanks so much

Heya, I'm going to put this in the physics forum for you as you should get more responses there.

You should also check out the forum to see if there's any other threads there which might be helpful to you! http://www.thestudentroom.co.uk/forumdisplay.php?f=131

Would it be worth mentioning the equations for his favour?

This has helped so much, thank you!

Hello and welcome to TSR.

Energy bands are the quantum energy levels allowed for electrons associated with any given atom. i.e. the shell distribution of electrons obeying the Pauli exclusion.

Thus energy absorption to promote an electron to a higher energy band can only be accomplished by photons of sufficient energy. (E=hv)
Photons are emitted when electrons drop energy bands and those photons are quantised to have a wavelength equivalent to the energy band-gap.

The definition of the work function is the minimum energy required to remove an electron from the highest filled level in the Fermi distribution at absolute zero such that it is STATIONARY at a point just outside the solid where no other field exists. i.e. to remove an electron from the surface of the material.

So far so good.

Extend the concept of energy bands to include a conduction band. i.e. electrons acquiring sufficient energy to be promoted out of the valence band so that they become free of the parent atom and able to drift within the lattice.

The band gap between the valence and conduction bands is markedly different for conductors, semiconductors and insulators and also temperature dependent.

Semiconductors have the property that some electrons will acquire enough thermal energy to enter the conduction band at room temperature. Thermal emission occurs.

The photoelectric effect is such that if the absorbed photon has greater energy than the work function then photoelectric emission will occur.