Laplace Transform Fitting as a Tool To Uncover Distributions of Reverse Intersystem Crossing Rates in TADF Systems

Kelly, Daniel; Gomes Franca, Larissa; Stavrou, Kleitos; Danos, Andrew; Monkman, Andrew P.

Abstract

Donor–acceptor (D–A) thermally activated delayed fluorescence (TADF) molecules are exquisitely sensitive to D–A dihedral angle. Although commonly simplified to an average value, these D–A angles nonetheless exist as distributions across the individual molecules embedded in films. The presence of these angle distributions translates to distributions in the rates of reverse intersystem crossing (krISC), observed as time dependent spectral shifts and multiexponential components in the emission decay, which are difficult to directly quantify. Here we apply inverse Laplace transform fitting of delayed fluorescence to directly reveal these distributions. Rather than a single average value, the crucial krISC rate is instead extracted as a density of rates. The modes and widths of these distributions vary with temperature, host environment, and intrinsic D–A torsional rigidity of different TADF molecules. This method gives new insights and deeper understanding of TADF host–guest interactions, as well as verifies future design strategies that target D–A bond rigidity.

Citation

Kelly, D., Gomes Franca, L., Stavrou, K., Danos, A., & Monkman, A. P. (2022). Laplace Transform Fitting as a Tool To Uncover Distributions of Reverse Intersystem Crossing Rates in TADF Systems. Journal of Physical Chemistry Letters, 13(30), 6981-6986. https://doi.org/10.1021/acs.jpclett.2c01864

• Journal Article Type: Article
• Acceptance Date: Jul 18, 2022
• Online Publication Date: Jul 26, 2022
• Publication Date: Aug 4, 2022
• Deposit Date: Aug 16, 2022
• Publicly Available Date: Aug 16, 2022
• Journal: The Journal of Physical Chemistry Letters
• Electronic ISSN: 1948-7185
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 13
• Issue: 30
• Pages: 6981-6986
• DOI: https://doi.org/10.1021/acs.jpclett.2c01864