One used solar grade silicon to produce high efficiency solar cells. Solar grade silicon has a doping concentration of about 10^17/cm^3. If one succeeds to make such cells, then he can use less pure silicon than solar grade silicon.
Please share with your opinions.
Hi Zekry. I think for high efficiency solar cell, we should consider the optimum doping of the silicon. As, the ultrahigh doping may cause the crystal deformation and increase the recombination and ultimately reduces solar cell efficiency. Thanks.
The researchgate notified me that a researcher named Chie Sheng Liu has up voted my question. But as you see the question is down voted. Would you please Mr. Liu tell us the truth.
Thank you
Dear Sanjay,
Yes, as the doping increases, the crystallographic defects increases and the minority carrier lifetime decreases. The diffusion coefficient consequently decreases. There are other high doping effects which may equally detract the solar cell operation. The most pronounced effect is the band gap narrowing which cause a decrease in the open circuit voltage of a solar cell. It is found that the optimum doping concentration of silicon leading to the highest cell efficiency as i said in my question is 10^17/cm^3.
I mean by my question to propose new solar cell structures that may be used to increase solar cell efficiency at higher doping than 10^17/cm^3. This would save purification cost of silicon.
Thank you for your share! I appreciate it.
Thanks for the invitation Prof. Abdelhalim. It is certanly true that high doping can results in the creation of a dead layer and as a consequence a loss in efficicency.
Altough there are solar cells such as the back contact cell (Sunpower) in which you heavily doped the zone of the contact to reduce the series resistence.
Dear Dr. Claudio, I know that the conventional solar cell has two a two heavily doped layers, namely the top n+ layer and the back surface field p+layer in addition to the substrate player with an optimum doping of 10^17/cm^3. I mean with the high doping is that of the substrate.
Thank you
Dear Prof. Abdelaihaim the subtrate concentration of 10^17/cm3 is based on the fact the you should get a maximum of lifetime and as a consequence a maximum current in outuput. The trend in silicon is toward thinner film so a decrese in lifetimewill not impact the effciciency. Granted that there is nomuch space for getting higher efficiency than if can save money avoiding the purification cost that will ertanly help. One question needs to be addressed: Is the purification cost higher in cost than the quantity of As or B necessary for the overdoping of the silicon wafer?
Dear Dr. Claudio
Yes you approached the solution by one step for thin film you donot need such large minority carrier lifetime realized at 10^17/cm3. because you need a diffusion length equal to the material thickness.Therefore ,one can use higher doped material but one must reduce the material thickness. Reducing the material thickness reduces the absorbed photons from the incident solar radiation.I would like to use single crystal silicon. Then the required thickness to absorb the major part of the solar radiation is about 150 micrometer.
ON purifying the metallurgical grade silicon to reach the required degree of purification,you purify it to the required impurity concentration. You do not add any impurities.
Thank You for the fruitful discussion.
Dear Colleagues,
It is my turn to share in answering my question. My purpose to ask this question is to attract the colleagues specializing in solar cells to share their ideas about the possibility to use silicon with a purity grade lower than the solar grade silicon. This subject unfortunately did not find the right response except few scientists with thankful contribution. We are driving research in using less qualified silicon in producing relatively high efficiency solar cells. This is achieved by changing the geometrical structure of the solar cells to allow the collection of the photo-generated electron hole pairs.This is achieved by making vertical grooves in the wafer and making pn junctions at the wall of the vertical grooves. The groove to groove must be made smaller equal double the diffusion length.
For more details go to the link:
http://www.ier-institute.org/2070-1918/lnit13/v13/349.pdf
As we have no fabrication facility we are ready to cooperate with scientists having such facilities and see that project is promising.
I would like to thank every scientist shared or followed this question.
Thank you
Dear colleagues,
I would like to pay your attention to our new trials of using heavily doped silicon as relatively cheap material for producing high efficiency solar cells. I would like to invite our esteemed colleagues specializing in solar cells to our proposed heavily doped silicon solar cell and how it really could be promising. The problem that i do not a have a laboratory. We welcome other efforts to realize technologically such solar cells. For the details of such developed solar cells please follow the recent paper:
Article Performance Enhancement of a Proposed Solar Cell Microstruct...
Best wishes
Dear Rerhab,
welcome,
This type of silicon with lower doping in this range has a photoconversion efficiency PCE less than that with the optimum doping. The optimum doping is 10^17/cm^3 before which and after which the PCE decreases than that at the optimum doping concentration of 10^17.
You can find more information in the book chapter in the link: https://www.researchgate.net/publication/323309527_Solar_cells_and_arrays_Principles_analysis_and_design
Abdelhalim Zekry
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