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bio website daniel.farrell.name
location Tokyo, Japan
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visits member for 4 years, 7 months
seen 58 mins ago

I know how to use the grey square -- do you?


13h
comment What is a n-type doped solar cell?
@Mareck can you provide a reference of where this n-type only solar cell comes from? In principle it is possible because electric field is not needed for photovoltaic action. Only a way of selecting the carrier types on extraction is needed. However, minority carriers (the holes in n-type materials) will have short lifetime so efficiency may not be great.
22h
comment Expression for spontaneous emission in solids
You explicitly conduction and valence bands in your questions. Please make your question accurate as not to waste people's time.
1d
comment Can I use an IV curve alone to differentiate between metallic, semiconducting and insulating materials?
This would allow you to measure the resistance, that's about it.
1d
comment Expression for spontaneous emission in solids
To answer the second part of your comment. $g_{12}$ tells you the density of states that can participate in optical transitions by conserving momentum. The formula I showed above is derived assuming direct band gap materials. In these materials there is a one to one correspondence between photon energy and k-space location which conserves momentum.
1d
comment Expression for spontaneous emission in solids
No, only for direct semiconductors. Equations assume vertical transitions in the E-k diagram.
1d
comment Expression for spontaneous emission in solids
This is the calculation for direct semiconductors where the transitions are vertical. This means that the initial and final k vectors are the same. For direct semiconductors there is a one to one correspondence between photon energy and k, no summation needed.
1d
revised Expression for spontaneous emission in solids
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1d
answered Expression for spontaneous emission in solids
1d
comment Expression for spontaneous emission in solids
OK, do you know the hole concentration of the valence band? Or do you assume a state is available?
1d
comment Expression for spontaneous emission in solids
Does you value of $W$ correspond to the blackbody emission rate? You can test this using Planck's Law.
2d
comment entropy balance equation in thermodynamics
Units incorrect?
Aug
28
comment Definition of luminescence
I think that is a good definition within the context of solid state physics. You could also say something like, "emission resulting in radiation with chemical potential", but this is perhaps too narrow a definition! I generally think of luminescence as radiation resulting from electronic recombination where the electronic population is in an excited state (i.e. not in chemical equilibrium).
Aug
25
comment What is the relationship between entropy and work?
Yes, it's called the Carnot Efficiency, en.m.wikipedia.org/wiki/Carnot%27s_theorem_(thermodynamics) but to derive it you have to assume conservation of energy and entropy.
Aug
25
revised What is the relationship between entropy and work?
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Aug
25
comment What is the relationship between entropy and work?
Yeah that's better phrasing, thanks. Updated.
Aug
25
revised What is the relationship between entropy and work?
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Aug
25
revised What is the relationship between entropy and work?
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Aug
25
answered What is the relationship between entropy and work?
Aug
20
comment Spherical and chromatic aberration correction
Why not use a microscopy lens? Internally they have multiple lenses which can correct for abbreviation.
Aug
20
answered Sign convention for mirror and lens formulas