Excessively large exciton diffusion length calculated from the exciton diffusion test

[yangwc123]

I have been trying to use Excimontec to study exciton diffusion in nonfullerene acceptor materials. First I used the dynamic test to reproduce the transients obtained from the pump-probe experiments. With appropriate choice of simulation parameters, such as the hopping rates, the energetic disorder, and the exciton lifetime, the experimental transients can be well reproduced. Then with these parameters I run the exciton diffusion test to calculate the diffusion lengths. However the results turn out to be much larger than the ones obtained by directly fitting the experimental transients. An extreme case is the NFA material IT4F, the calculated value is 48 nm while the experimental value is 27nm. For other cases, I find that the calculated value divided by $\sqrt{2}$ can be very close to the experimental value. But we cannot explain this $\sqrt{2}$ factor. It might be somehow related to the algorithm. Can you explain more about the algorithm in the User Manual? One question is that if the $L_d$ is calculated by first reaction algorithm directly, or the diffusion constant $D$ is calculated, and $L_d$ is obtained by $L_d=\sqrt{2dD\tau}$. Thank you!

[MikeHeiber]

The diffusion length is calculated using the mean displacement distance of the excitons in the simulation. I can't say for sure what might be going on. I am not actively developing this simulation right now, so you'll have to dig into the code and figure out what's going on. If you find any bugs and fix them, please consider submitting a pull request.

[yangwc123]

Dear Mike, Thank you very much for your reply! I found that the difference between the calculated diffusion length and measured one is due to the different definition. Taking into account this difference, they agree with each other fairly well. Have you got the recent email I sent to you regarding the higher-than-initial exciton density in the dynamic test? I think in this case the program generates some unphysical results. Thank you. best regards, Wenchao

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On Sun, Feb 6, 2022 at 3:20 AM Michael C. Heiber ***@***.***> wrote: The diffusion length is calculated using the mean displacement distance of the excitons in the simulation. I can't say for sure what might be going on. I am not actively developing this simulation right now, so you'll have to dig into the code and figure out what's going on. If you find any bugs and fix them, please consider submitting a pull request. — Reply to this email directly, view it on GitHub <https://urldefense.com/v3/__https://github.com/MikeHeiber/Excimontec/issues/120*issuecomment-1030719422__;Iw!!Nmw4Hv0!jClVMGLW-2lQOLQDL4yQgR068jWQ9m6O8EcsRabkvETEsyru4eEC5iqTYgRQ-A9aWeuExOY$>, or unsubscribe <https://urldefense.com/v3/__https://github.com/notifications/unsubscribe-auth/AOKIT6F7CKPHDZN654HA3N3UZW5EXANCNFSM5DGVS7AA__;!!Nmw4Hv0!jClVMGLW-2lQOLQDL4yQgR068jWQ9m6O8EcsRabkvETEsyru4eEC5iqTYgRQ-A9ar4yA-s4$> . Triage notifications on the go with GitHub Mobile for iOS <https://urldefense.com/v3/__https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675__;!!Nmw4Hv0!jClVMGLW-2lQOLQDL4yQgR068jWQ9m6O8EcsRabkvETEsyru4eEC5iqTYgRQ-A9a9TFn04c$> or Android <https://urldefense.com/v3/__https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign*3Dnotification-email*26utm_medium*3Demail*26utm_source*3Dgithub__;JSUlJSU!!Nmw4Hv0!jClVMGLW-2lQOLQDL4yQgR068jWQ9m6O8EcsRabkvETEsyru4eEC5iqTYgRQ-A9aza89n2A$>. You are receiving this because you authored the thread.Message ID: ***@***.***>

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