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Issue 29, 2019
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Locking excitons in two-dimensional emitting layers for efficient monochrome and white organic light-emitting diodes

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Abstract

Simplified organic light-emitting diodes (OLEDs) with high efficiency are key for successful products. Here, we demonstrate simplified OLEDs by combining ultra-thin non-doped emitting layers (UN-EMLs) with charge-transfer (CT)-type mixed donor–acceptor recombination layers. The CT recombination layers provide a bipolar recombination zone and improved long-range coupled Förster energy transfer. The UN-EMLs not only remain similar in optical properties compared to the doped-EMLs including photoluminescence quantum yield and emitter orientation but also mitigate charge trapping by the emitters in the CT-host systems despite the large energy level differences. The results of time-resolved photoluminescence decay reveal that although a five times smaller volume emitter is used in the UN-EMLs, the intensity of triplet–triplet annihilation stays comparably low by restricting the exciton migration to the two-dimensional plane. Making use of the excellent optoelectronic properties of the proposed system, green OLEDs with extremely simplified structures reach an external quantum efficiency (EQE) of 23.2%, nicely matching with the optical simulation results. Furthermore, white OLEDs with the same structure achieve a maximum EQE of 18.7% with considerably low efficiency roll-off. The combined system demonstrated here provides a novel approach for significantly simplified and tunable device structures of OLEDs, while maintaining high performance.

Graphical abstract: Locking excitons in two-dimensional emitting layers for efficient monochrome and white organic light-emitting diodes

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Supplementary files

Article information


Submitted
23 May 2019
Accepted
24 Jun 2019
First published
24 Jun 2019

This article is Open Access

J. Mater. Chem. C, 2019,7, 8929-8937
Article type
Paper

Locking excitons in two-dimensional emitting layers for efficient monochrome and white organic light-emitting diodes

Y. Liu, C. Hänisch, Z. Wu, P. Will, F. Fries, J. Wu, S. Lenk, K. Leo and S. Reineke, J. Mater. Chem. C, 2019, 7, 8929 DOI: 10.1039/C9TC02768H

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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