A Study of Thin Film Encapsulation on Improving Electrical Characteristics and Reliability for Flexible OLEDs

Abstract:

In this work, we investigated the effect of thin film encapsulation on V_th shift in a-IGZ0 TFTs. The result shows that decreasing the NH₃ flow rate of deposited SiON films, the trend of V_th shift under the operation mode can vary from negative to positive direction, which can be attributed to lower amount of hydrogen diffused from SiON to the a-IGZO TFTs. Beside, we designed the TFE with stable inorganic-organic-inorganic stack structure, of which the CVD1 deposited with low NH₃ flow rate and the CVD2 with high barrier property, and a 16.9-inch high performance flexible OLED panel with controlled V_th shift and RA lifetime over 475 h was achieved at the condition of 85 °C and 85% RH. This study demonstrates the influence of TFE on a-IGZO TFTs, and offers an optimized TFE structure which promises both electrical characteristics and reliability for flexible OLEDs.

• Periodical: Materials Science Forum (Volume 1058)
• Pages: 93-98
• DOI: https://doi.org/10.4028/p-1w1unq
• Online since: April 2022
• Authors: Qing Wu Yin*, Wen Dong Lian, Jin Chuan Li, Jia Jia Qian, Sheng Dong Zhang, Wei Ran Cao
• Keywords: Flexible OLEDs, Reliability, Thin Film Encapsulation, V_th Shift

References

[1] Reineke, S., Lindner, F., Schwartz, G. et al. White Organic Light-emitting Diodes with Fluorescent Tube Efficiency. Nature 459, 234–238 (2009). https://doi.org/10.1038/nature08003.

DOI: 10.1038/nature08003

[2] M. Wang, P. Chen and C. Lin, Novel a-IGZO Pixel Circuit Adopting External Circuit for Use in 3-D AMOLED Displays. 2016 23rd International Workshop on Active-Matrix Flat-panel Displays and Devices (AM-FPD), (2016), pp.69-71,.

DOI: 10.1109/am-fpd.2016.7543622

[3] Jae Kyeong Jeong, Hui Won Yang, Jong Han Jeong, Yeon-Gon Mo, Origin of Threshold Voltage Instability in Indium-gallium-zinc Oxide Thin Film Transistors. Applied Physics Letters 93, 123508 (2008) https://doi.org/10.1063/1.2990657.

DOI: 10.1063/1.2990657

[4] P. Görrn, P. Hölzer, T. Riedl, and W. Kowalsky. Stability of Transparent Zinc Tin Oxide Transistors under Bias Stress. Applied Physics Letters 90, 063502 (2007) https://doi.org/10.1063/1.2458457.

DOI: 10.1063/1.2458457

[5] Kenji Nomura, Toshio Kamiya, Masahiro Hirano, and Hideo Hosono1, Origins of threshold voltage shifts in room-temperature deposited and annealed 𝑎-In–Ga–Zn–O thin-film transistors, Applied Physics Letters 95, 013502 (2009) https://doi.org/10.1063/1.3159831.

DOI: 10.1063/1.3159831

[6] Nahm, HH., Park, C. & Kim, YS. Bistability of Hydrogen in ZnO: Origin of Doping Limit and Persistent Photoconductivity. Science Report 4, 4124 (2014). https://doi.org/10.1038/srep04124.

DOI: 10.1038/srep04124

[7] Jaeseob Lee, Jin-Seong Park, et al. The Influence of the Gate dielectrics on Threshold Voltage Instability in Amorphous Indium-gallium-zinc Oxide Thin Film Transistors. Applied Physics Letters 95, 123502 (2009) https://doi.org/10.1063/1.3232179.

DOI: 10.1063/1.3232179

[8] W.J. Potscavage, S. Yoo1, B. Domercq, B. Kippelen, Encapsulation of Pentacene/C60 Organic Solar Cells with Al2O3 Deposited by Atomic Layer Deposition. Applied Physics Letters 90, 253511 (2007).

DOI: 10.1063/1.2751108

[9] Park, Kyoung & Lee, Seunghee & Lee, Hyunkoo & Cho, Yong-Hwan & Park, Yong & Im, Sung & Park, Sang-Hee. High-performance thin H:SiON OLED encapsulation layer deposited by PECVD at low temperature. RSC Advances. 9. 58-64 (2019). 10.1039/C8RA08449A.

DOI: 10.1039/c8ra08449a

[10] Y. C. Park, W. B. Jackson, D. L. Smith, and N. M. Johnson, Deposited silicon nitride with low electron trapping rates. Journal of Applied Physics 74, 381-386 (1993) https://doi.org/10.1063/1.354121.

DOI: 10.1063/1.354121

[11] Han, Yun & Jeong, Eun Gyo & Kim, Hyuncheol & Kwon, Seonil & Im, Hyeon-Gyun & Bae, Byeong-Soo & Choi, Kyung. Reliable thin-film encapsulation of flexible OLEDs and enhancing their bending characteristics through mechanical analysis. RSC Advance, 6. (2016).

DOI: 10.1039/c6ra06571f