Web Application for Calculating Short Circuit Current Density (Jsc) from External Quantum Efficiency (EQE).

 

Now, this app is published as an open-source tool on nanoHUB.org, and you can cite it as well. Have a look https://nanohub.org/tools/jscfromeqe

External Quantum Efficiency (EQE) is defined as the ratio of number of charge carriers collected at the electrode to the number of photons incident on the solar cell. Low EQE can be attributed to several optical and electrical loss mechanisms for charge carriers such as:

1.) The absorber layer is too thin and does not absorb all of the photons.
2.) Photons are not absorbed as they may have energy smaller than the bandgap.
3.) Photons can be reflected back from the solar cell.
4.) Parasitic absorption losses in the inactive layers of the cell. 
5.) Recombination of light excited charge carriers before they are collected at the contacts.

Jsc is an important performance parameter to study solar cells of all available technologies. Calculating this requires a lot of effort as interpolation (for matching EQE data with AM 1.5G spectra{https://www.nrel.gov/grid/solar-resource/spectra-am1.5.html}) and integration are to be performed with precision. To calculate short circuit current density (Jsc), EQE measurement is performed under short circuit conditions. Since Jsc can also be calculated fom JV measurement, EQE holds the advantage of independent spectral shape of light source and is also independent of cell area. 

    For Jsc calculation, photon flux is multiplied with EQE, leading to the flow of electrons leaving the solar cell at corresponding wavelength. If we integrate  (photon flux * EQE) throughout the wavelength range, Jsc is obtained. For crystalline silicon, the important range would be from 300 to 1200 nm.

I have made this web application using Python, Streamlit and Heroku to quickly review EQE data. Check it out in the link given below:

https://jscfromeqe.streamlit.app/

Just drag and drop your .csv file with first column "Wavelength" and second column "EQE". 

Note : Wavelength must be in nm and EQE must be in percentage.

Result is displayed as shown below with variable Wavelength range.

For an ideal solar cell, EQE is 100% above the bandgap. We can compare our solar cell with ideal as well. For crystalline silicon bandgap is 1.12 eV, which equals wavelength of 1107 nm give a theoretical Jsc of 43.8 mA/Cm². Integrated loss represents loss in Jsc due to :

1) Reflection of photons

2) Recombination of light excited charge carriers before they are collected at the contacts.

If we have a solar cell with EQE of 100% throughout the solar spectrum, we could theoretically generate Jsc of 68.9 mA/Cm².