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Reliable high temperature, high humidity flexible thin film encapsulation using Al2O3/MgO nanolaminates for flexible OLEDs

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Abstract

Since most organic materials are very sensitive to moisture and oxygen, organic light emitting diodes (OLEDs) require an encapsulation layer to protect the active layer from these gases. Since light, flexible and portable OLEDs are being employed in more diverse climates and environmental conditions, the OLED encapsulation layer must retain robust mechanical properties and stability in high temperature/high humidity conditions. Al2O3 films have demonstrated excellent barrier performance, but they readily hydrolyze when exposed to prolonged harsh environments. In this study, we fabricated a thin film encapsulation (TFE) film that was resistant to hydrolysis, using Al2O3/MgO (AM) nanolaminates. MgO has superior resistance to harsh environments, and the aluminate phase generated by the chemical reaction of Al2O3 and MgO provided excellent barrier performance, even after storage in harsh conditions. A multi-barrier fabricated using the AM nanolaminate showed excellent barrier performance, close to the level required by OLEDs. It did not significantly deteriorate even after a bending test of 1,000 iterations at 0.63% strain. After 1,000 cycle of bending, the electrical properties of the passivated OLEDs were not significantly degraded at shelf-lifetime test where the fabricated device was stored for 50 days in a harsh environment of 60 °C, 90% relative humidity. The multi-barrier shows the best performance compared to previous studies on flexible encapsulation that can be used in harsh environments.

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Acknowledgements

This research was supported by the Engineering Research Center of Excellence (ERC) Program supported by the National Research Foundation (NRF) of the Korean Ministry of Science, ICT & Future Planning (MSIP) (Grant No. NRF-2017R1A5A1014708). The authors express sincere gratitude to National NanoFab (NNFC) for the measurements. We also thank Prof. Byeong-Soo Bae from KAIST for help in synthesis of the polymers.

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Authors and Affiliations

  1. School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea

    Ki Suk Kang, So Yeong Jeong & Kyung Cheol Choi

  2. Department of Clothing and Textiles, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwangju, 61186, Republic of Korea

    Eun Gyo Jeong

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  1. Ki Suk Kang
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  2. So Yeong Jeong
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Correspondence to Eun Gyo Jeong or Kyung Cheol Choi.

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Reliable high temperature, high humidity flexible thin film encapsulation using Al2O3/MgO nanolaminates for flexible OLEDs

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Kang, K.S., Jeong, S.Y., Jeong, E.G. et al. Reliable high temperature, high humidity flexible thin film encapsulation using Al2O3/MgO nanolaminates for flexible OLEDs. Nano Res. 13, 2716–2725 (2020). https://doi.org/10.1007/s12274-020-2915-5

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