While simulating perovskite solar cells we normally take defect density as 1E14 or 1E15. Is there any specific reason for this?Can we take the value lesser than this like 1E10 or 2E11.
Thank you
Dear Romana Yousuf ,
Hope you are well!
Yes you can take the defect density smaller than 10^14 /cm^3. The origin of the defects are either added impurities and or crystallographic defects such as vacancies or dislocations. These defects are generated during the fabrication of the device. One has to reduce these defects to the limit such that they will not affect the photocurrent of the solar cells.
So, the limit of the defects is determined by on set of its effect on the shortcircuit current. Which means that Nt< Ntmax for Isc to be not less than the photocurrent.
These defects can act as a effective recombination centers reducing the minority carrier lifetime and thereby can lead to decreasing the the short-circuit current and increasing the dark current.
Both detracts the photo conversion efficiency.
I would like that you refer to the following works:Chapter Solar cells and arrays: Principles, analysis and design
and
Conference Paper Generic Analytical Models for Organic and Perovskite Solar Cells
and
Article Investigating the performance of formamidinium tin-based per...
Best wishes
Thank you very much Prof. Abdelhalim abdelnaby Zekry sir....
You are the most active expert on Research Gate. You always helped me to clear my doubts related to solar cells....
I am very much interested in reading your research work, two papers and a book chapter mentioned above are already with me and i always refer them whenever i m in need of.
Thank you once again sir....
Actually, it totally depends what type of film you are considering. For single crystal perovskite film, the carrier diffusion length can be as long as 100um(micrometer), for which, with the typical mobility the defect density can be put in the range of 1010- 1012 cm-3. But to me its too much ideal, too optimistic. Moreover, in this range there is hardly any change found in the simulation results. To observe the effect of defects ( if that is the main intention), defect levels need to be made higher.
You may check one of our team's following for for reference for perovskite materials.
Conference Paper Simulation based Investigation of Inverted Planar Perovskite...
It may help.
Thank you.
Dear Colleagues! Romana Yousuf and Md. Sazzadur Rahman
In materials having high absorption coefficient they need a thin layer to absorb the incident solar radiation. This because one needs only a thickness = 1/alpha
the absorption coefficient. The perovskites are characterized by high absorption coefficient and therefore it need only about a half micrometer to absorb the radiation. The second issue is that the solar cells are based on pin structure.
So the perovskite region will be also the built in field region.
On the other side the mobility of such material is relatively high. Therefore it allows much lower lifetime than that in crystalline silicon. This allows for much higher defect density than the single crystal silicon.
This is the secret of good working solar cells in spite of much higher defect density in the material.
Bes wishes
Abdelhalim abdelnaby Zekry Dear Sir, Thank you very much fr the insightful explanation
Abdelhalim abdelnaby Zekry Sir...
Thank you so much for this detailed explanation.....
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