Barrier layers, especially those that block gases such as water vapor, are a common type of coating on the surface of electronic and optical devices. In one study, barrier layers were developed using PHPS, which together with adhesive layers formed adhesive sheets. The surface density of the barrier layer ranges from 2.4 to 4.0g·cm⁻³, in which the proportion of oxygen, nitrogen and silicon accounts for 60% to 75%, 0% to 10% and 25% to 35%, respectively. This is one of the early patents for the development of barrier layers using PHPS. Another study investigated the effect of PHPS structure on gas barrier properties and found that by adjusting the ratio of SiH3 to SiH and SiH2 to 1:(10 to 30), gas barrier films with excellent stability under high temperature and high humidity conditions can be prepared.

In addition to the use of PHPS alone, it is often used in combination with modified materials to prepare barrier layers. For example, a silicon-containing film was prepared using PHPS and a metal compound such as tris-sec-buxy aluminum with the structural formula SiOxNyMz, showing excellent stability under high temperature and humidity conditions. Other studies have described several additives used in combination with PHPS, including alkyl substituted guanidine, oxyn-containing crown ether amines, amino substituted polycyclic cycloalkyl, and alkyl substituted oxime, which significantly improve the gas barrier properties of the resulting films.

The composition of the solution also affects the performance of PHPS barrier layer. By limiting the specific structural units of PHPS and the ratio of Si-R bond to Si-H bond, PHPS can be dissolved in aliphatic hydrocarbon solvent to prepare a silica-like glass barrier layer with low water vapor permeability.

In addition, the effect of preparation method on the properties of barrier layer is also the focus of research. The barrier films with specific refractive index range were prepared by heating and plasma treatment, and the films with excellent gas barrier and phase difference function were prepared by PHPS on a variety of polymer substrates under vacuum ultraviolet irradiation. Finally, SaSaki et al. investigated the effects of Si-N bond number, PHPS film composition and free volume on the film densification process under vacuum ultraviolet (VUV) induction, and found that VUV irradiation can promote the rapid release of hydrogen and the film densification, providing valuable guidance for the development of nano SiN films with high density and excellent gas barrier properties.

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