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ORGANIC RADICAL EMITTERS

Radically more stable

Nature Materials volume 18, pages 917–918 (2019)Cite this article

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Violating the Aufbau principle is shown to be a successful strategy to improve the stability of neutral organic radicals used in organic light-emitting diodes.

Organic light-emitting diodes (OLEDs) have come a long way since their first demonstration in 19871. It has been realized very early that the organic emitters at the heart of such devices bear a major limitation to the internal quantum efficiency, related to the way charges combine to occupy the available exciton states. Conventional organic emitters are closed-shell molecules that sport one singlet and three triplet excitons, randomly occupied by the spin S = 1/2 electrons and holes that meet up in the emission layer. Unfortunately, the decay of triplet excitons is quantum mechanically forbidden as the Pauli exclusion principle calls for a spin flip during the transition. Consequently, OLEDs utilizing conventional organic emitters are left with about 75% of non-emissive triplet excitons limiting their internal quantum efficiency to a disappointing 25%2. Special material concepts have been developed to overcome these unique and limiting spin statistics of OLEDs. Among these, a recent approach has been the use of emitting neutral organic radicals. Writing in Nature Materials, Haoqing Guo and colleagues3 show how to obtain stable emission from these radicals by violating a fundamental principle of quantum mechanics — the Aufbau principle.

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Fig. 1: Neutral radical molecules.

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Authors and Affiliations

  1. Institute of Applied Physics, Technische Universität Dresden, Dresden, Germany

    Sebastian Reineke

  2. Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP), Technische Universität Dresden, Dresden, Germany

    Sebastian Reineke

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  1. Sebastian Reineke
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Correspondence to Sebastian Reineke.

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Reineke, S. Radically more stable. Nat. Mater. 18, 917–918 (2019). https://doi.org/10.1038/s41563-019-0453-x

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