How Does the Fermi Level Influence Solar Cell Voltage?

[Max.Planck]

Hello,

Im working on a paper on solar cells and i came across the term "Fermi level". What exactly is the Fermi level in this context:

"The working voltage produced by the device is the difference
between the chemical potential of the titanium dioxide (Fermi
level) and the redox potential of the mediator (I-/I3-)."

Thank you!

Max Planck

 

[f95toli]

"in this context"?
Is there are any particular reason why you think they are referring to anything but the "normal" Fermi level?

 

[Max.Planck]

Hi,

I already read this topic: https://www.physicsforums.com/showthread.php?t=239923

The first reply states that there are 2 definitions of fermi level.
Its a bit confusing, can anyone explain?

 

[DrDu]

Chemical potential and Fermi level are synonyms.

 

[Max.Planck]

What exactly is the chemical potential?

 

[Max.Planck]

I read that the chemical potential of a semiconductor is in the middle of the band gap, is this true?

 

[DrDu]

No, generally not.
Its the derivative of e.g. energy U with respect to particle number (here of electrons) at fixed S and V or of G at fixed T and p. In a semiconductor it is usually somewhere inside the gap, but seldomly in the middle. In a metal at absolute zero it is the borderline between the occupied levels and the empty energy levels.
Have a look at a book on thermodynamics or solid state physics.

 

[LewisEE]

In general the Fermi level and the (electro)chemical potential are not the same, but in a semiconductor we regard them as being synonymous.

 

[Max.Planck]

Thanks