Quantitative prediction of rate constants and its application to organic emitters

Abstract

Abstract Many phenomena in nature consist of multiple elementary processes. If we can predict all the rate constants of each process quantitatively, we can comprehensively predict and understand various phenomena in nature. Here, we report that it is possible to quantitatively predict all related rate constants and quantum yields without conducting experiments, using multiple-resonance thermally activated delayed fluorescence (MR–TADF) as an example. MR–TADF is desirable for practical application in organic light-emitting diodes (OLEDs) because of their narrow emission spectra, high luminescence efficiency, and chemical stability. However, MR–TADF emitters have one drawback: slow reverse intersystem crossing (RISC), leading to efficiency roll-off and reduced device lifetime. We first showed a quantum chemical calculation method for quantitatively reproducing all experimentally obtained rate constants and quantum yields for previously synthesized MR–TADF emitters. Next, this method was applied to presently unsynthesised molecules. This study reveals a strategy to improve RISC without compromising other important factors: rate constant of radiative decay, photoluminescence quantum yields, and emission linewidth. Our method is robust and can be applied in a wide range of research fields—not only for quantitative prediction of rate constants and quantum yields but also for a comprehensive understanding of the mechanism including the time evolution of excitons.