Designing encapsulation film with both high barrier property and excellent flexibility has been challenging for the current brittle inorganic films owing to the strain-induced cracking. Inorganic/organic multilayer has been proposed due to the organic layer can function as buffers of the inorganic layer and defect-decoupling layer, realizing the improvement of flexibility and maintaining barrier property. Polydimethylsiloxane (PDMS) was widely used as an organic encapsulation layer due to its high stability, elasticity, and transparency. The introduction of PDMS helps the barrier film to resist distorting under the bending motions. However, the delamination and cracking occurred under bending motion in a small curvature radius due to the mismatched strain and coefficient of thermal expansion (CTE) between PDMS and inorganic films such as Al₂O₃. Realization of improving their strain and CTE mismatch is possible by doping nanoparticles into PDMS. The Al₂O₃/PDMS hybrid film with the doping of SiO₂ fabricated via atomic layer infiltration (ALI) method showed mechanical stability and endure 1000 repetitive stretch tests with 1%, but the water vapor transmission rate (WVTR) was only 10^-3 g/m²/day, which was attributed to the lower crosslinking density of PDMS result in higher free volume and chain mobility. It’s a challenge to develop a strategy for improving the crosslink density of PDMS. In this work, the PDMS-based composite substrate with engineered stiffness was developed by employing the addition of silane coupling agent and SiO₂. Atomic layer infiltration (ALI) coupled with UV-curing was introduced for sub-surface cross-linking of PDMS in Al₂O₃/SiO₂/PDMS hybrid film, and the resulted Al₂O₃/SiO₂/PDMS hybrid film showed highly stretchable and barrier properties. The result indicates that Al₂O₃/SiO₂/PDMS hybrid film is a promising encapsulation film applicable to flexible electronics.

Keywords: atomic layer infiltration (ALI), flexible film, encapsulation, UV-curing method, water vapor transmission rate (WVTR)

Refs.

1. Y. Li, D. Wen, Y. Zhang, Y. Lin, K. Cao, F. Yang, R. Chen, Highly-stable PEN as a gas-barrier substrate for flexible displays via atomic layer infiltration, Dalt. Trans. (2021) 16166–16175. https://doi.org/10.1039/d1dt02764f.
2. Zhang, D. Wen, M. Liu, Y. Li, Y. Lin, K. Cao, F. Yang, R. Chen, Stretchable PDMS Encapsulation via SiO₂ Doping and Atomic Layer Infiltration for Flexible Displays, Adv. Mater. Interfaces. 9 (2022) 1–9. https://doi.org/10.1002/admi.202101857.