Efficient and stable single-layer organic light-emitting diodes based on thermally activated delayed fluorescence

Abstract

From a design, optimization and fabrication perspective, an organic light-emitting diode consisting of only one single layer of a neat semiconductor would be highly attractive. Here, we demonstrate an efficient and stable organic light-emitting diode based on a single layer of a neat thermally activated delayed fluorescence emitter. By employing ohmic electron and hole contacts, charge injection is efficient and the absence of heterojunctions results in an exceptionally low operating voltage of 2.9 V at a luminance of 10,000 cd m−2. Balanced electron and hole transport results in a maximum external quantum efficiency of 19% at 500 cd m−2 and a broadened emission zone, which greatly improves the operational stability, allowing a lifetime to 50% of the initial luminance of 1,880 h for an initial luminance of 1,000 cd m−2. As a result, this single-layer concept combines high power efficiency with long lifetime in a simplified architecture, rivalling and even exceeding the performance of complex multilayer devices.

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Fig. 1: Device layout and molecular structure of the TADF emitter CzDBA.
Fig. 2: Charge transport in CzDBA and simulated recombination profile.
Fig. 3: Device performance of single-layer CzDBA OLEDs.
Fig. 4: Operational lifetime of single-layer CzDBA OLEDs.
Fig. 5: Ambient stability of a single-layer CzDBA OLED.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

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Acknowledgements

We thank C. Bauer, H.-J. Guttmann and F. Keller for technical support and Y. Ie for the synthesis of 4CzIPN. This project has received funding from the European Union Horizon 2020 research and innovation programme under grant agreement no. 646176 (EXTMOS).

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Contributions

G.-J.A.H.W. proposed the project. G.-J.A.H.W. and N.B.K. designed the experiments. N.B.K. carried out device fabrication and measurements. G.-J.A.H.W. performed simulations. G.-J.A.H.W. and P.W.M.B. supervised the project and wrote the manuscript.

Corresponding author

Correspondence to Gert-Jan A. H. Wetzelaer.

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Molecular structures and optoelectronic characterization.

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Kotadiya, N.B., Blom, P.W.M. & Wetzelaer, G.A.H. Efficient and stable single-layer organic light-emitting diodes based on thermally activated delayed fluorescence. Nat. Photonics 13, 765–769 (2019). https://doi.org/10.1038/s41566-019-0488-1

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