2021 Fiscal Year Research-status 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 | amorphous TiOx films / Titanium(IV) alkoxides / Titanocene Dichloride / water vapor treatment |
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| Outline of Annual Research Achievements |
The project aims to develop low temperature solution processed high performance thin film encapsulation (TFE) by photochemical conversion of metal-organic precursors to metal oxides using vacuum ultraviolet (VUV) irradiation.in 2021,three kinds of titanium-organic precursors were investigated.
(ⅰ): Titanocene Dichloride (Cp2TiCl2). preferential hydrolysis of ionic Ti-Cl bonds is anticipated for Cp2TiCl2 to result in 1D polymer of [Ti(Cp)2O]n, which then to obtain dense and void-free thin films by its entanglement. Conditions to achieve controlled hydrolysis of Cp2TiCl2 have been explored, and VUV irradiation decreasing the bonds of organic ligands have also been confirmed by FTIR. However, low solubility of precursor make it difficult to have a homogeneous solution.
(ⅱ): Tetra-buthoxide (TTBO, Ti(OC4H9)4 ). The precursor solution was prepared from TTBO with a catalyst, which is to control polycondensation of hydrolyzed titanium alkoxides. Precursor layers with a thickness of 200 nm could be converted into much thinner TiOx of 129 nm and denser films with a high refractive index of n = 1.85 (at λ = 800 nm) by 30 min VUV irradiation at RT. In turn, crack-free films with smooth surface were obtained.
(ⅱ): Titanium(IV) ethoxide (Ti(OEt)4 ). Effect of exposure to water vapor on the formation of TiOx films was investigated. It is found that water vapor promote the conversion of the alkoxide coating to an extended M－O film network.
In addition, I have also extensively studied metal-alkoxides precursor as an efficient electron injection layer for improved performance of iOLEDs.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
Basically, the work has been carried on according to the original plan. In 2021, we have investigated the effects of different precursor solutions, the concentration of water, exposure to water vapor, and VUV irradiation time on the formation of metal oxides and their influences on the properties of obtained thin films.
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| Strategy for Future Research Activity |
Based on the knowledge we obtained from the current study, both exposure to water vapor and VUV irradiation promote the formation of -M-O-M- network. In order to realize amorphous TiOx thin films with high density, combination of water vapor treatment and VUV irradiation would be the efficient approach. Therefore, effect of processing conditions on the properties of thin films are to be investigated. Water vapor transmission rate (WVTR) of the thin films prepared under optimized conditions are to be tested.
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