Extended theoretical modeling of reverse intersystem crossing for thermally activated delayed fluorescence materials.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 38295171.
- Also identified by DOI 10.1126/sciadv.adk3219 and PMC identifier 10830100.
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Abstract
Thermally activated delayed fluorescence (TADF) materials and multi-resonant (MR) variants are promising organic emitters that can achieve an internal electroluminescence quantum efficiency of ~100%. The reverse intersystem crossing (RISC) is key for harnessing triplet energies for fluorescence. Theoretical modeling is thus crucial to estimate its rate constant (<i>k</i><sub>RISC</sub>) for material development. Here, we present a comprehensive assessment of the theory for simulating the RISC of MR-TADF molecules within a perturbative excited-state dynamics framework. Our extended rate formula reveals the importance of the concerted effects of nonadiabatic spin-vibronic coupling and vibrationally induced spin-orbital couplings in reliably determining <i>k</i><sub>RISC</sub> of MR-TADF molecules. The excited singlet-triplet energy gap is another factor influencing <i>k</i><sub>RISC</sub>. We present a scheme for gap estimation using experimental Arrhenius plots of <i>k</i><sub>RISC</sub>. Erroneous behavior caused by approximations in Marcus theory is elucidated by testing 121 MR-TADF molecules. Our extended modeling offers in-depth descriptions of <i>k</i><sub>RISC</sub>.