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Nano Research Energy 2024, 3: e9120109 https://doi.org/10.26599/NRE.2024.9120109
Research Article | Open Access | Issue | Published: 10 January 2024

Investigation into charge carrier dynamics in organic light-emitting diodes

Show Author's Information Dong-Guang Zheng1,§,  Hyeon-Dong Lee2,§,  Gyeong Won Lee3,  Dong-Soo Shin3,  Jeongwon Kim4,  Jong-In Shim3( ),  Zhiqun Lin5( ),  Tae-Woo Lee2,6( ),  Dong Ha Kim4,7,8( )
Information Engineering College, Hangzhou Dianzi University, Hangzhou 311305, China
Department of Materials Science and Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea
Department of Photonics and Nanoelectronics, Hanyang University ERICA, 55 Hanyangdeahak-ro, Sangnok-gu, Ansan, Gyeonggi 15588, Republic of Korea
Department of Chemistry and Nanoscience, Ewha Womans University, 52, Ewhayeodae-gil, Seodaemun-gu, Seoul 03760, Republic of Korea
Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117585, Singapore
School of Chemical and Biological Engineering, Institute of Engineering Research, Research Institute of Advanced Materials, Soft Foundry, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea
Basic Sciences Research Institute (Priority Research Institute), Ewha Womans University, Seoul 03760, Republic of Korea
Nanobio∙Energy Materials Center (National Research Facilities and Equipment Center), Ewha Womans University, Seoul 03760, Republic of Korea

§ Dong-Guang Zheng and Hyeon-Dong Lee contributed equally to this work.

Keywords:
degradation mechanism, organic light-emitting diodes, ideality factor, carrier transport processes
Cite this article:
Zheng D-G, Lee H-D, Lee GW, et al. Investigation into charge carrier dynamics in organic light-emitting diodes. Nano Research Energy, 2024, 3: e9120109. https://doi.org/10.26599/NRE.2024.9120109
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Abstract Full text Electronic supplementary material About this article

Organic light-emitting diodes (OLEDs) have demonstrated remarkable advancements in both device lifetime and luminous efficiency. However, insufficient operation lifetime due to device degradation remains a major hurdle, especially for brighter devices. Understanding the degradation mechanisms of OLEDs due to the degradation of functional materials and the formation of defects in device architectures continues to be a significant challenge. Herein, we evaluate the degradation characteristics by scrutinizing the electrical and optical properties, as well as analyzing the charge carrier dynamics in pristine and aged states of phosphorescent OLEDs (PhOLEDs). We show that degradation mechanisms in PhOLEDs can be elucidated in terms of the ideality factors of current and luminance in pristine and aged device states. The consistent shifts in distinct ideality factors across various states points out that the device degradation is attributed to the deterioration of the guest material, i.e. green-light-emitting phosphorescent material. Conversely, the incongruity in ideality factor changes between the two states indicates that the degradation results from the deterioration of non-light-emitting material. Subsequent characterization experiments provide further evidence that this degradation is primarily attributed to the deterioration of CBP-host material. The thorough understanding of degradation mechanisms established in this study can contribute to realizing the highly reliable PhOLEDs with a long lifetime.


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Abstract
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Electronic supplementary material
About this article

Investigation into charge carrier dynamics in organic light-emitting diodes

Show Author's information Dong-Guang Zheng1,§, Hyeon-Dong Lee2,§, Gyeong Won Lee3, Dong-Soo Shin3, Jeongwon Kim4, Jong-In Shim3( ), Zhiqun Lin5( ), Tae-Woo Lee2,6( ), Dong Ha Kim4,7,8( )
Information Engineering College, Hangzhou Dianzi University, Hangzhou 311305, China
Department of Materials Science and Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea
Department of Photonics and Nanoelectronics, Hanyang University ERICA, 55 Hanyangdeahak-ro, Sangnok-gu, Ansan, Gyeonggi 15588, Republic of Korea
Department of Chemistry and Nanoscience, Ewha Womans University, 52, Ewhayeodae-gil, Seodaemun-gu, Seoul 03760, Republic of Korea
Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117585, Singapore
School of Chemical and Biological Engineering, Institute of Engineering Research, Research Institute of Advanced Materials, Soft Foundry, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea
Basic Sciences Research Institute (Priority Research Institute), Ewha Womans University, Seoul 03760, Republic of Korea
Nanobio∙Energy Materials Center (National Research Facilities and Equipment Center), Ewha Womans University, Seoul 03760, Republic of Korea

§ Dong-Guang Zheng and Hyeon-Dong Lee contributed equally to this work.

Abstract

Organic light-emitting diodes (OLEDs) have demonstrated remarkable advancements in both device lifetime and luminous efficiency. However, insufficient operation lifetime due to device degradation remains a major hurdle, especially for brighter devices. Understanding the degradation mechanisms of OLEDs due to the degradation of functional materials and the formation of defects in device architectures continues to be a significant challenge. Herein, we evaluate the degradation characteristics by scrutinizing the electrical and optical properties, as well as analyzing the charge carrier dynamics in pristine and aged states of phosphorescent OLEDs (PhOLEDs). We show that degradation mechanisms in PhOLEDs can be elucidated in terms of the ideality factors of current and luminance in pristine and aged device states. The consistent shifts in distinct ideality factors across various states points out that the device degradation is attributed to the deterioration of the guest material, i.e. green-light-emitting phosphorescent material. Conversely, the incongruity in ideality factor changes between the two states indicates that the degradation results from the deterioration of non-light-emitting material. Subsequent characterization experiments provide further evidence that this degradation is primarily attributed to the deterioration of CBP-host material. The thorough understanding of degradation mechanisms established in this study can contribute to realizing the highly reliable PhOLEDs with a long lifetime.

Keywords: degradation mechanism, organic light-emitting diodes, ideality factor, carrier transport processes

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Publication history

Received: 12 September 2023
Revised: 13 November 2023
Accepted: 22 November 2023
Published: 10 January 2024
Issue date: June 2024

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© The Author(s) 2024. Published by Tsinghua University Press.

Acknowledgements

Acknowledgements

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean Government (2020R1A2C3003958), the Basic Science Research Program (Priority Research Institute) through the NRF grant funded by the Ministry of Education (2021R1A6A1A10039823), and the Korea Basic Science Institute (National Research Facilities and Equipment Center) grant funded by the Ministry of Education (2020R1A6C101B194).

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