I am researching on solar cell system and very new in this field. I came to know that the imaginary part of dielectric function somehow relates to the absorption spectra of a material. I read some papers but somehow it is still not clear to me. Any one that can kindly tell me the main relationship between those two?
Thank you in advance,
Best regard
Hello,
Essentially the dielectric function is the more fundamental quantity as it links the dielectric displacement to the electric field in Maxwells equations and can be directly related to . The relationship between the complex dielectric function (e_1+ie_2) and the complex optical constant (n + ik) is simply (e_1+ie2) = (n + ik)^2, so e1=n^2-k^2 and e2=2nk.
If now k is much smaller the n and there is little dispersion such as in transparent media you can say the e1 relates to the refractive index as it is e1~=n^2 and e2 is proportional to k as n is approximately constant. For strong absorbers however both real and imaginary part of epsilon will contribute to the spectral shape of k and n.
Hope this clarifies things a bit.
Karsten
Hello,
Essentially the dielectric function is the more fundamental quantity as it links the dielectric displacement to the electric field in Maxwells equations and can be directly related to . The relationship between the complex dielectric function (e_1+ie_2) and the complex optical constant (n + ik) is simply (e_1+ie2) = (n + ik)^2, so e1=n^2-k^2 and e2=2nk.
If now k is much smaller the n and there is little dispersion such as in transparent media you can say the e1 relates to the refractive index as it is e1~=n^2 and e2 is proportional to k as n is approximately constant. For strong absorbers however both real and imaginary part of epsilon will contribute to the spectral shape of k and n.
Hope this clarifies things a bit.
Karsten
You should give an example where the refractive index is used
It is standard to use absorption because the strength of the absorption is proportional to the imaginary part of the RI
However since almost a century now the absorption (spectrum) can be calculated / estimated or else understood from the quantum molecular structure of a compound.
Adding to the colleagues: The complex dielectric constant is useful for calculating the the reflection coefficient of the incident radiation with specific wavelength. It can be used o calculate the characteristic wave impedance of the material. As for the absorption of the incident solar radiation one uses the photon absorption coefficient of the material as a function of lambda to calculate the photo generated electron hole pairs and then the photo generated current.
Best wishes
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