As I know for solar cells, minority carrier lifetimes are one of the most important parameters and majority carrier lifetime is not important for photovoltaics under low level injection. Still I found a confusing comment from some expert that majority carrier lifetime is important too. I tried to find out some reference values for majority lifetime for p-type but failed to get anything.
Can someone please share some references on this topic?
Is it by mistake that the expert had mentioned majority carrier lifetime instead of minority carrier lifetime?
Does "majority carrier lifetime" mean the relaxation time of the majority carriers? The majority carrier mobility is proportional to the relaxation time divided by the carrier effective mass. The relaxation time is mostly determined by extrinsic factors causing carrier scattering such as crystal defects, impurities etc. while effective mass is intrinsic determined by the band structure. The relaxation time is therefore an important parameter indicating material quality particularly for TCO window layers.
@Manjunatha: No it's not by mistake.
@ Eric: Yes I guess what you are saying is right. But I'm not sure if that is important for electron-hole pair separation in the bulk region.
Som does not the recombination rates of majority carriers equals that of minority carriers, because a recombination process involves an equal number of holes and electrons? However, at high injection the recombination rate is no longer determined primarily by the excess minority carrier concentration. The recombination lifetime does depend upon the injection level and also the resistivity thus majority carrier concentration.
Exactly. the recombination rate will be same. But since carrier concentration are different at a particular injection level, the lifetimes are different. Now if you just consider low level injection (which is the case for solar cell for typical resistivity of substrate used), it's only minority carrier concentration that should be important. But what is the value majority carrier lifetime? I want to know some value of it and fit them into simulation. For example, if for a Cz wafer, minority carrier lifetime value is 1 micro-s, what would be typical value of majority carrier lifetime. Will it be 10 mico-s or 100 micro-s or 10 ms? I am searching for this reference...Thanks Eric for the discussion.
I don't think it was a mistake,I had a similar discussion with my professor not too long ago and i asked him why most solar cell devices have a thinner n-type and thicker p-type material for the P-N junction.
He explained to me in terms of the fact that a solar cell is a minority carrier device and he went on to state the obvious reasons concerning the lifetime and diffusion lengths of holes and electrons.
He further stated that currently,there is an hot issue where researchers are trying to utilize the majority carriers for the same purpose we currently use minority carriers in a solar cell and methods are currently being developed that will see the configuration in terms of P and N type thicknesses being either same or the other way round.He stated that,it is one of the critical issues under serious investigation but very little progress has been made.He encouraged me to check it online but just like the person who asked the question pointed out,i haven't been able to find anything so far.
Therefore,@Som Mondal,am sure the expert who made that comment did not make a mistake but could be because,currently the issue is in it's infancy.
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