PySintonAnalysis

To make sure it is all clear, here are all the main equations that define how these parameters are analysed.

Please read the Equations.docx file to understand the workflow and figure labels.

See more on

• RS Bonilla, et al (2017), Phys. Status Solidi A, 214: 1700293
• A. Kimmerle, J. Greulich, and A. Wolf, Sol. Energy Mater. Sol. Cells 142, 116–122 (2015).
• H. M€ackel and K. Varner, Prog. Photovolt. Res. Appl. 21, 850–866 (2013).
• B. Hammann et al., IEEE Journal of Photovoltaics, vol. 13, no. 4, pp. 535-546, July 2023.)

Starting from the effective lifetime measured in a Sinton tester

$\frac{1}{\tau_{eff}}=\frac{1}{\tau_{bulk_int}}+\frac{1}{\tau_{SRH}}+\frac{1}{\tau_{surf}} $.

Effective recombinaiton velocity is: $S_{eff}=\sqrt{D(\frac{1}{\tau_{surf}})}*\tan(W/2\sqrt{(\frac{1}{D\tau_{surf}})})$. Which is often approximated to $S_{eff}=W/2(\frac{1}{\tau_{surf}})$

Then, J0 can be estimate from the average of the flat region of a plot of: $\frac{\partial}{\partial \Delta n}(n_i^2(S_{eff}))$ which requires the algorithm implemented for getting $J_{0S-avg}$, since we need to calculate an SRH recombination that makes $J_{0s-avg}=\frac{qn_i^2S_{eff}}{N_{dop}+\Delta n}$ a true equation. Here $J_0$ would be a single value parameter, but it is of course possible to simply calculate S and then obtain a J0 as a function of minority carriers.

Some useful advice for extracting J0:

• Start by letting the software fit the tn, tp, and E_t values.
• Check that the fit makes sense in the figure. Remember this code does not fit lifetime, it finds the SRH term that is most compatible with a carrier-independent J_0s average term, as per Kimmerle's method.
• If you are doing many samples at the same time, and you cannot check all of them, start on the assumption that they all have the same bulk lifetime.
• This means setting a strict value of the SRH bulk via tn, tp, and E_t.
• Often you can find out how much defect mediated recombination sample have based on a sample with reasonable passivation (J0s<10 fA/Cm2)
• Then use this to fit the best possible SRH, and analyse all samples with a single value of SRH bulk.
• Conversely, if your processes aim to change the bulk, but you have a good confidence of the surface passivation, then set the value of J0s and allow the fitted to find the best recombination parameters it can find.