I have learned about the formulas to calculate fluorescent/radiative decay rate as given in the attached files. I found this article through the mentioned link. But I'm unable to find the source of this article/equation.
Please share the source of this article or equation. Thanks
https://www.researchgate.net/post/How-to-determine-fluorescent-radiative-decay-rate-tau-of-a-TADF-material-theoretically