If absorber layer material of solar cell has donor defect concentration comparable to the acceptor hole concentration, Then what will happen to the cell efficiency with increase in absorber layer thickness and why?
I am getting first increase in efficiency and then it decreases with increase in thickness of absorber material.
Dear Goutam,
welcome,
Adding to the respected colleague Tony and Jan-Martin, what you obtained is a typical performance of any absorber material of the solar radiation. This point is investigated in many papers and discussed in the researchgate.
It is so that as the material thickness increases, it absorbs more incident radiation as the incident photons decay exponentially with the distance traveled in the absorber. The thickness required to absorb an incident radiation with absorption coefficient alpha is = 1/alpha. If one increases the thickness beyond this thickness one would not gain nothing.
On the other side the generated electron hole pairs must be collected to affect an electric current of the cell. As the thickness of the abosrber increases the the electrons hole pairs getting recombined increase. The maximum distance that can be traveled to be collected is smaller equal to the diffusion length.
AS the thickness increases one generates and collects more carriers until we reach a peak and then as the thickness increases further the collection efficiency will decrease while the photoabsorption remains the same.
Best wishes
As you increase the absorber thickness from zero, you capture light proportional to the area of the cell. As the layer becomes thick, you lose photoelectrons proportional to the volume of the cell. So you get the effect you notice, and increase in efficiency followed by a decrease.
I have some questions, because the absorption coefficient and internal light reflection may play a role: What type of semiconductor do you have in mind as absorber: direct-gap or indirect-gap material? What kind of cell architecture do you have in mind: thin-film or bulk?
Dear Goutam,
welcome,
Adding to the respected colleague Tony and Jan-Martin, what you obtained is a typical performance of any absorber material of the solar radiation. This point is investigated in many papers and discussed in the researchgate.
It is so that as the material thickness increases, it absorbs more incident radiation as the incident photons decay exponentially with the distance traveled in the absorber. The thickness required to absorb an incident radiation with absorption coefficient alpha is = 1/alpha. If one increases the thickness beyond this thickness one would not gain nothing.
On the other side the generated electron hole pairs must be collected to affect an electric current of the cell. As the thickness of the abosrber increases the the electrons hole pairs getting recombined increase. The maximum distance that can be traveled to be collected is smaller equal to the diffusion length.
AS the thickness increases one generates and collects more carriers until we reach a peak and then as the thickness increases further the collection efficiency will decrease while the photoabsorption remains the same.
Best wishes
The tendency of dependence a solar cell efficiency on the “absorber layer” thickness commonly is the same as described in the answers above, especially in the sufficiently detailed answer of Abdelhalim Zekry. But term “absorber layer” requires qualification. The Abdelhalim Zekry aswer refers to semiconductor solar cells with p-n junctions. In a perovskite or organic solar cells, which based on a Gratzel Cells, efficiency drop with absorber layer thickness may be connected with increase in the series resistance of a solar cell. The same reason decreases an efficiency of p-n junction solar cells in some cases, so the questions of Jan-Martin Wagner are important too. For my opinion, the main question is – the absorbed layer is inorganic semiconductor materials or it is organic/perovskite semiconductor? The ratio of donors and acceptors in these two cases has a different effect on the efficiency
Dear Svetlana,
I would like that you revise this white paper for me:Data Advanced solar cell materials and solar cells analytical modeling
Thank you for your effort
Best wishes
In thin film solar cells, why the thickness of absorber layer isn't be 200nm or 100nm? and what the relation between the absorber layer thickness and series, shunt resistance?
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