On the Inverted Singlet-Triplet Gaps and Their Relevance to Organic Light-Emitting Diodes

09 August 2019, Version 2
This content is a preprint and has not undergone peer review at the time of posting.


The basic design principle for emitters exhibiting thermally activated delayed fluorescence (TADF) is the minimization of the singlet-triplet gap. While typically this gap is positive, a possible inversion of states has been proposed as a pathway to improve the efficiency of organic light-emitting diodes. Despite the efforts to design such emitters, there are very few reports indicating that it is at all possible. We analyze the problem of gap inversion from the perspective of the electronic structure theory. The key result is that inversion is possible but requires a substantial contribution of double excitations and that commonly used cheap electronic structure methods would fail to predict it.


singlet-triplet gap
electronic structure
double excitations

Supplementary materials



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