Thank you very much as usual!

Ok thank you, that makes perfect sense since the Fermi level difference is relative! In that case, can I assume `E_{F,B}=E_F`

in Q2.5? The way I see it is -- as you mentioned in another issue I believe -- I consider `E_{F,B}`

to be stationary with respect to the reference before and after contact (and only `E_{F,A}`

would move to align). Is this reasoning correct?

Is it correct to say that `\psi_{B0}=-E_{F,B}/e`

since `\frac{E_{F,A}-E_{F,B}}{e}=-\psi_{A0}+\psi_{B0}`

?

Yes thank you, it is indeed higher than niB

Hi,

I'm unsure how to go about question 2.5 (and as far as I've seen, other people are having the same problem as well). I'm guessing it's the LHS of the conditions we have to rewrite, so I've managed to find a relation between both `E_{CB}(x\rightarrow\infty)`

and `E_{CB}(x=0)`

based on `\psi_{B0}`

but struggle to make use of the bandgap and especially `n_{B0}`

(do we even need it in the expression since B is intrinsic?).
What I have so far is the following:

`\psi_{B0}=-E_{FB}/e`

with `E_{FB}=E_{CB}-1/2*E_{gB}`

-- but here `E_{CB}`

corresponds to conduction band energy before contact, so this is where I get stuck (unless we can assume that it's equal to the `E_{CB}`

far from the interface after contact??)...

Could you please let me know if I'm going in the right direction, or if there's something wrong in my reasoning?

Are we assuming n-doping of B as well in this case then?

Hi,

I'm unsure how to go about question 2.5 (and as far as I've seen, other people are having the same problem as well). I'm guessing it's the LHS of the conditions we have to rewrite, so I've managed to find a relation between both `E_{CB}(x\rightarrow\infty)`

and `E_{CB}(x=0)`

based on `\psi_{B0}`

but struggle to make use of the bandgap and especially `n_{B0}`

(do we even need it in the expression since B is intrinsic?).
What I have so far is the following:

`\psi_{B0}=-E_{FB}/e`

with `E_{FB}=E_{CB}-1/2*E_{gB}`

-- but here `E_{CB}`

corresponds to conduction band energy before contact, so this is where I get stuck (unless we can assume that it's equal to the `E_{CB}`

far from the interface after contact??)...

Could you please let me know if I'm going in the right direction, or if there's something wrong in my reasoning?

Thank you very much, it does! I didn't realize we weren't looking at the specific case where B is intrinsic but rather at the problem on a more general level.

Hi,

I'm unsure how to go about question 2.5 (and as far as I've seen, other people are having the same problem as well). I'm guessing it's the LHS of the conditions we have to rewrite, so I've managed to find a relation between both `E_{CB}(x\rightarrow\infty)`

and `E_{CB}(x=0)`

based on `\psi_{B0}`

but struggle to make use of the bandgap and especially `n_{B0}`

(do we even need it in the expression since B is intrinsic?).
What I have so far is the following:

`\psi_{B0}=-E_{FB}/e`

with `E_{FB}=E_{CB}-1/2*E_{gB}`

-- but here `E_{CB}`

corresponds to conduction band energy before contact, so this is where I get stuck (unless we can assume that it's equal to the `E_{CB}`

far from the interface after contact??)...

Could you please let me know if I'm going in the right direction, or if there's something wrong in my reasoning?

Hi,

I have a question about the band diagram asked in Q3.3. Firstly, I have trouble understanding how it should be fundamentally different from Figure 3 given in the homework. In addition, I don't see how this could fulfill the condition where the conduction band offset `\Delta E_C`

should remain the same (before contact `\Delta E_C > 0`

, after contact - as shown in Fig.3 - it seems that `\Delta E_C > 0`

).

Thanks!

Thanks a lot!

Hi,

I have a question about the band diagram asked in Q3.3. Firstly, I have trouble understanding how it should be fundamentally different from Figure 3 given in the homework. In addition, I don't see how this could fulfill the condition where the conduction band offset `\Delta E_C`

should remain the same (before contact `\Delta E_C > 0`

, after contact - as shown in Fig.3 - it seems that `\Delta E_C > 0`

).

Thanks!

Hi again, I have a question regarding the solar cell power conversion efficiency.

According to the lecture, to calculate this value, we should also take into account the photons that are not absorbed by the semiconductor due to their energy being lower than the bandgap.

However, in the question itself, it says to calculate the number of photons radiated by the blackbody as a function of frequency "which are all absorbed by the solar cell" -- I take this as meaning we should only consider the energy of the photons within the light frequency range referred to in Question 3.2.

Which approach should we take here? In principle I would assume we should consider the entire solar spectrum (ie. including the energy of photons which do not get absorbed) to compute the overall conversion efficiency...

I hope this makes sense!

Thank you!

Hi again, I have a question regarding the solar cell power conversion efficiency.

According to the lecture, to calculate this value, we should also take into account the photons that are not absorbed by the semiconductor due to their energy being lower than the bandgap.

However, in the question itself, it says to calculate the number of photons radiated by the blackbody as a function of frequency "which are all absorbed by the solar cell" -- I take this as meaning we should only consider the energy of the photons within the light frequency range referred to in Question 3.2.

Which approach should we take here? In principle I would assume we should consider the entire solar spectrum (ie. including the energy of photons which do not get absorbed) to compute the overall conversion efficiency...

I hope this makes sense!

Hi, I have a question with respect to Question 2.1, where we have to calculate the Fermi energies of A (n-doped) and B (intrinsic).

In principle, to do this we would need the density of states of the conduction and valence bands Nc and Nv, which are in turn related to the effective carrier masses... Can we assume those to be the same in those calculations, such that Nc=Nv? If not, I would be unsure how to proceed in order to answer the question.

Thank you very much for the clarification!

Hi, I have a question with respect to Question 2.1, where we have to calculate the Fermi energies of A (n-doped) and B (intrinsic).

In principle, to do this we would need the density of states of the conduction and valence bands Nc and Nv, which are in turn related to the effective carrier masses... Can we assume those to be the same in those calculations, such that Nc=Nv? If not, I would be unsure how to proceed in order to answer the question.