Besides measurements uncertainties suggested above. This is a common phenomenom that is seen in thin film Pv devices.

Explanations can be found in a book of Roland Scheer and Hans-Werner Schock, Chalcogenide Photovoltaics (Ed. Wiley). Below are explanations found in the book. Effects can occur in many PV devices.

"With EQE lower than Jsc.

1) Barrier for the photocurrent which is large under low light intensity or monochromatic illumination but becomes lowered by photodoping of the buffer at AM1.5 illumination.

2) Large number of micro shunts. If the cell is irradiated only on a limited area (as in QE measurement), the non-illuminated part acts as a shunting load. Seen from the active solar cell, this load is in parallel with the input resistance of the QE current amplifier. Although the total shunt resistance of the cell (measured as a macroscopic quantity by JV analysis) is high, the local shunt resistance seen from the active solar cell part may be small. Thus, the current is drained throughout the shunting load. Reducing the cell area to the area of illumination may increase the QE.

With Jsc lower than EQE.

1) A Barrier for the photo current exists. Due to a limited thermionic emission current after, the small current density of a quantum efficiency measurement can pass the barrier. In contrast the high current density under AM1.5 illumination can not pass the barrier."

Dear Arjun

It is possible to calculate the short-circuit current of the OPV cell using the spectral response of the cell  using the equation:

J sc= q ∫ ϕ (λ) ⋅ EQE (λ ) dλ

where q is the charge of the electron, and ϕ is the photon flux. This calculation however assumes that the EQE used is representative of the entire cell. If significant variation in performance over the cell area is present this calculated Jsc will not be representative.  There are several factors that could lead to incorrect estimation of the EQE such as  1) the different spectral response between the reference cell (which  is often used to determine the irradiance of the solar simulator) and the measured  cell, 2) all photons reaching anOPV device are not transmitted only to the active region where the conversion process occurs.

Due to the refractive index of the materials used, light shall be reflected

from the front surface of the device. The total reflectance (diffuse and specular), and the total transmittance (diffuse and normal), of the device should  be measured with the aid of an integrating sphere.

Regards

Maria

I agree with the above. One more thing though: a difference is not unusual. Even, for silicon solar cells, which are well understood and reproducible, there is a slight difference. The reason is that most solar simulators don't have a perfect solar spectrum. This means that for Si, jsc from EQE is actually more reliable than jsc from IV because you can put the exact solar spectrum into the equation. However, for reasons outlined above errors in EQE may outweigh errors in the spectrum for other types of cells.

Dear Arjun,

Can you please provide me the details how you have simulated Jsc from from EQE ? Thanks in advance

Ashraful - check Maria's answer. And read carefully the explanation why it is inaccurate - and can only serve as a rough estimate.

What has been said by the colleagues is okay and cover most of the aspects of the possible answers of the question. However ,there is a fundamental and intrinsic factor that may cause a difference  between the calculated and the measured shortcircuit current of a solar cell, namely the measuring error. Also, there is also basic calculation errors due to  discretization, interpolation, defining  precisely the integration limit and the numerical integration process itself. All these processes brings APPROXIMATIONS in the solution. This is apart from the not identical incident radiation in the two cases, the external quantum efficiency and the the i-v curve measurements.

Happy new year

The person who down voted my answer do not deserve to be a member of the research community. I am very disappointed of such people.Sure, my answer do not deserve that.

It is also important to light bias the sample to 1 sun if there is any differences in carrier lifetime or collection efficiency due to illumination level which I have heard can be a problem in non silicon PV cells.  The EQE measurement is almost always performed well below 1 sun and thus this can raise inssues due to charge carrier dynamics.

Besides measurements uncertainties suggested above. This is a common phenomenom that is seen in thin film Pv devices.

Explanations can be found in a book of Roland Scheer and Hans-Werner Schock, Chalcogenide Photovoltaics (Ed. Wiley). Below are explanations found in the book. Effects can occur in many PV devices.

"With EQE lower than Jsc.

1) Barrier for the photocurrent which is large under low light intensity or monochromatic illumination but becomes lowered by photodoping of the buffer at AM1.5 illumination.

2) Large number of micro shunts. If the cell is irradiated only on a limited area (as in QE measurement), the non-illuminated part acts as a shunting load. Seen from the active solar cell, this load is in parallel with the input resistance of the QE current amplifier. Although the total shunt resistance of the cell (measured as a macroscopic quantity by JV analysis) is high, the local shunt resistance seen from the active solar cell part may be small. Thus, the current is drained throughout the shunting load. Reducing the cell area to the area of illumination may increase the QE.

With Jsc lower than EQE.

1) A Barrier for the photo current exists. Due to a limited thermionic emission current after, the small current density of a quantum efficiency measurement can pass the barrier. In contrast the high current density under AM1.5 illumination can not pass the barrier."

Please help me:

I got the raw data of EQE maesurent include of current at each illuminated wavelength but I dont know how to calculate (integrating) photocurrent for that device!

Please reffer the attached files. Thank you very much!

When I calculated Jsc with your submitted EQE data, the resultant Jsc value is around 3.9 mA/cm2.

Is this similar to your value derived from J-V solar cell data?

If not, we need to consider on the measurement method more correctly.

Dear Arjun,

According to your question there is a difference in current density values calculated from EQE measurement system and measured directly with the I-V solar simulator. Several points have been already discussed for this discrepancy. Here are some possible reasons for different current density values:

1.) Since in EQE system we use small illumination area than in a solar simulator therefore the generation of charge carrier will be from small area in EQE and large area in IV system. Since whole area is not free from contacts ( and we feed full area of the device in the software of solar simulator for calculation of Jsc) therefore in I-V system generation will not be from complete device since some of the cell area is covered with fingers and bus bar but in EQE measurement system we do not consider any shaded area while calculating the Jsc from the small illumination spot which is generally free from contacts.  

2.) The AM 1.5 used in EQE system is standard data but in case of solar simulator this is simulated by a Xenon lamp. So it is quite possible to have different values in both systems. 

3.) The shunting paths can also play their role in this discrepancy of Jsc values. In EQE system we illuminate a small area and collect the charge carrier through bus bar. Generated charge carrier can diffuse to the  dark region that works as low resistance path and act as shunt for the generated current.  

Hope all this information discussed for answering your question is helpful for all those who are working on these measurements. 

I was trying to calculate the Jsc from EQE. I am working out the unit of:

Jsc = q ∫ ϕ (λ) ⋅ EQE (λ ) dλ. It is basically 1.6×10^-19 C*(W/m^2*nm)*nm => 1.6×10^-19 (C*W/m^2) => 1.6×10^-19 (C*J/s*m^2) => 1.6×10^-19 (A/m^2)*J. Is this correct? What should be done to cancel out the J (joule)? Also, if we multiply the result of this integration ∫ ϕ (λ) ⋅ EQE (λ ) dλ by 1.6×10^-19, the total Jsc will become extremely small. What is the problem here?

Thanks!

dear Amirhossein

I suggest to check the dimension of electron flux. maybe it works

Hi, im also having difficulty in calculating Jsc from IPCE. can someone help me asap..please show me how to integral it. really appreciate your help.