Open circuit voltage is an important parameter of solar cell. From Shockley Quiesser Model, i have seen that it depends on temperature, absorber thickness, short circuit current density, initial current density, doping concentration, effective carrier concentration. But can anyone please explain about the it or share the mathematical proof of it or have some other concept to share. Thanks
Dear Hassan,
Hope you are well!
It is my pleasure that you invite me to answer you question.
Your question is related to the maximum open circuit voltage or how to maximize the Voc. The maximum value of the open circuit voltage that can be theoretically achieved equal to the band gap energy of the absorber. The first loss from this value is that when one builds a junction its contact difference of potential will be less than Eg. The contact difference of potential phi = Vt log (NaNd/ni^2) for homojunctions. When the solar cells irradiated with solar radiation the the collected electrons and holes will accumulate on the cathode and anode of the solar cells and produce an opposing electric field to the built in electric field such that the net field decreases and then vanishes when the open circuit voltage reaches the contact difference of potential. So Voc max= phi.
This type of solar cell operation is not possible since when the solar cell is forward biased by the accumulated photo generated charges a internal diode current passes from the anode to the cathode counteracting the original photocurrent leading to the practical opencircuit condition which is
Iph= Id at open circuit
This leads to the equation of the opencircuit voltage
Voc- nVt ln ( Iph/ Id)
Id is the diode current
Id= I0 exp Voc/nVt),
I0 is the reverse saturation current,
n is the ideality factor ,
Vt is the thermal voltage.
For getting full information about the opencircuit voltage please follow the book chapter: Chapter Solar cells and arrays: Principles, analysis and design
If you find this chapter useful please recommend it for your colleagues and your students.
Best wishes
Solar cell parameters such as open circuit voltage, short circuit current, maximum voltage, maximum current, maximum power, fill factor, power conversion efficiency can be calculated from the current- voltage characteristics curve.
Many graph in the previous research reference articles explained the reason for your questions.
Hi
Please check the following work. It describes the process in details. I believe it will help you.
https://pubs.acs.org/doi/10.1021/acsenergylett.9b02262
Regards
Dear Hassan,
Hope you are well!
It is my pleasure that you invite me to answer you question.
Your question is related to the maximum open circuit voltage or how to maximize the Voc. The maximum value of the open circuit voltage that can be theoretically achieved equal to the band gap energy of the absorber. The first loss from this value is that when one builds a junction its contact difference of potential will be less than Eg. The contact difference of potential phi = Vt log (NaNd/ni^2) for homojunctions. When the solar cells irradiated with solar radiation the the collected electrons and holes will accumulate on the cathode and anode of the solar cells and produce an opposing electric field to the built in electric field such that the net field decreases and then vanishes when the open circuit voltage reaches the contact difference of potential. So Voc max= phi.
This type of solar cell operation is not possible since when the solar cell is forward biased by the accumulated photo generated charges a internal diode current passes from the anode to the cathode counteracting the original photocurrent leading to the practical opencircuit condition which is
Iph= Id at open circuit
This leads to the equation of the opencircuit voltage
Voc- nVt ln ( Iph/ Id)
Id is the diode current
Id= I0 exp Voc/nVt),
I0 is the reverse saturation current,
n is the ideality factor ,
Vt is the thermal voltage.
For getting full information about the opencircuit voltage please follow the book chapter: Chapter Solar cells and arrays: Principles, analysis and design
If you find this chapter useful please recommend it for your colleagues and your students.
Best wishes
- Badges
- Science topic