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Organic Molecules with Inverted Gaps between First Excited Singlet and Triplet States and Appreciable Fluorescence Rates

submitted on 29.10.2020, 00:36 and posted on 29.10.2020, 19:00 by Robert Pollice, Pascal Friederich, Cyrille Lavigne, Gabriel dos Passos Gomes, Alan Aspuru-Guzik
One of the recent proposals for the design of state-of-the-art emissive materials for organic light emitting diodes (OLEDs) is the principle of thermally activated delayed fluorescence (TADF). The underlying idea is to enable facile thermal upconversion of excited state triplets, which are generated upon electron-hole recombination, to excited state singlets by minimizing the corresponding energy difference resulting in devices with up to 100% internal quantum efficiencies (IQEs). Ideal emissive materials potentially surpassing TADF emitters should have both negative singlet-triplet gaps and appreciable fluorescence rates to maximize reverse intersystem crossing (rISC) rates from excited triplets to singlets while minimizing ISC rates and triplet state occupation leading to long-term operational stability. However, molecules with negative singlet-triplet gaps are extremely rare and, to the best of our knowledge, not emissive. In this work, based on computational studies, we describe the first molecules with negative singlet-triplet gaps and considerable fluorescence rates and show that they are more common than hypothesized previously.


DARPA Accelerated Molecular Discovery Progam HR00111920027

Marie Skłodowska-Curie 795206

Dr. Anders G. Frøseth

Natural Resources Canada and the Canada 150 Research Chairs program

Compute Canada


Email Address of Submitting Author


University of Toronto



ORCID For Submitting Author


Declaration of Conflict of Interest

The University of Toronto has filed a provisional application for a US patent based on the technology described in this paper, naming R.P., P.F., C.L., G.d.P.G. and A.A.-G. as inventors.