Dear Abdelghani,

Do you want to extract the revere saturation current of the solar cell from the measurement of the quasi steady state photoconduction method?

If it is so, then:

The base doping concentration is chosen to maximize the efficiency of the solar cell. It is about one ohm.cm. Concerning the reverse saturation current you can measure it directly by measuring the opencircuit voltage and the corresponding shortcircuit current for different illumination intensities. Then plot the the shortcircuit current versus the opencircuit voltage in a semilog scale. You get a straight line at the lower current densities. Extrapolating this straight line to zero opencircuit voltage gives you J0 of the solar cell

Wish you uccess

I would like to to thank Jan for his valuable contribution. If the minority carrier lifetime in the substrate is much higher than that in the emitter and the excess carrier concentration at the boundaries of the junction are nearly equal, then the cell current will be dominated by the recombination in the emitter. This condition may be achieved by excessive high injection in the base region. Under this condition, the effective lifetime is prevailed by the recombination in the emitter. To reach the high injection at relatively lower current densities, it is preferred to use relatively lower doped substrates.

However in practical solar cells. the revere saturation current of the emitter is made much smaller then that of the substrate to reduce the photogenerated charges in it and increase the open circuit voltage.

I would like to thank you for your contributions, but the problem is that we can not reach a high injection level with our wafers (HEM, mc-Si), max MCD= 7 x 10^16 cm-3.

Not at all Abdelghani, it is my pleasure. In fact your question is very interesting. It seems that the lifetime of minority carriers in your substrate is low because of the presence of the defect at the boundaries between the crystallites. Even when you increase the illumination intensities to many suns you may not achieve the the required high injection level for the dominance of the emitter recombination current.`

You have to passivate the grain boundaries and or gettering process for the metallic impurities. You have to avoid reducing the lifetime during fabricating the solar cells.

If these methods are not working to elevate the lifetime i will tell you a method to separate the the recombination in the emitter from that in the base.

wish you success.

I will be very gratfull if you suggest me a method to separate recombination in emitter from that in base

Dear Abelghani,

May be one of the easiest method is to prepare two solar cells with different substrate thicknesses W1 and W2. Then you measure the revere saturation current of the solar cells as explained in my previous comment. Assume you get I01 and I02, respectively.If the condition of the base width W < the diffusion length Ln in the base region, then the reverse saturation current in the base is inversely proportional to W.

That is I0b = K/w. where K is a constant. Then you have two algebraic equations in two unknowns as follows:

I01 = I0e + k /w1,

I02 = I0e + k/ w2

Solving these two equations you can get I0e and k. Consequently you can get the reverse saturation current in the bases.

I used such idea before. see the linkhttps://www.researchgate.net/publication/3059043_Reduction_of_the_current_gain_of_the_n-p-n_transistor_component_ofa_thyristor_due_to_the_doping_concentration_of

Article Reduction of the Current Gain of the n-p-n Transistor Compon...

any value as measured gives directly the J0 if you are using Sinton.