2022 Fiscal Year Annual Research Report
Development of High Performance Thin Film Encapsulation by VUV Photochemical Gel Conversion
| Project/Area Number |
20K05317
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| Research Institution | Yamagata University |
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Principal Investigator |
吉田 麗娜 (孫麗娜) 山形大学, 有機エレクトロニクスイノベーションセンター, 研究員 (30813555)
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| Project Period (FY) |
2020-04-01 – 2023-03-31
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| Keywords | solution processing / perhydropolysilazane / SiN layer / VUV irradiation / WVTR / polymeric precursor / high gas barrier / thin film devices |
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| Outline of Annual Research Achievements |
This research has successfully developed room temperature fast solution-processed high performance thin film encapsulation (TFE) using perhydropolysilazane (PHPS)-derived SiNy layers by vacuum ultraviolet (VUV) irradiation methods. Barrier performance can be affected by the film density, thickness, and the presence of defects (cracks, pinholes, etc.). It was found that the density of SiNy layers increased with increasing VUV dose due to the formation of Si-N networks and atomic rearrangement, resulting in a decrease of free volume in the bulk layer. But it is independent of the VUV intensity and the temperature of the substrate. The denser the film, the higher its barrier performance became. However, cracks occurred as the VUV irradiation dose and film thickness increased due to the internal strain caused by the volume shrinkage, eventually resulting in low barrier performance. Therefore, the barrier performance can be optimized by controlling the film thickness and VUV dose. After examining various film thicknesses and VUV conditions, it was determined that a film thickness of 200 nm and a VUV dose of 12 J/cm2 provided the best barrier property and achieved extremely low water vapor transmission rate (WVTR) values of 2.2 × 10－4 g m－2d-1 for 1 unit coating with 330 nm thick, and 4.8 × 10－5 g m－2 d－1 for 3 units coatings with 990 nm thick. Such excellent barrier properties against oxygen and water vapor make them suitable for use in flexible thin film devices, as well as in other applications.
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