Abstract
Silica is one of the most efficient gas barrier materials, and hence is widely used as an encapsulating material for electronic devices. In general, the processing of silica is carried out at high temperatures, i.e., around 1000 °C. Recently, processing of silica has been carried out from a polymer called Perhydropolysilazane (PHPS). The PHPS reacts with environmental moisture or oxygen and yields pure silica. This material has attracted many researchers and has been widely used in many applications such as encapsulation of organic light-emitting diodes (OLED) displays, semiconductor industries, and organic solar cells. In this paper, we have demonstrated the process optimization of the conversion of the PHPS into silica in terms of curing methods as well as curing the environment. Various curing methods including exposure to dry heat, damp heat, deep UV, and their combination under different environments were used to cure PHPS. FTIR analysis suggested that the quickest conversion method is the irradiation of PHPS with deep UV and simultaneous heating at 100 °C. Curing with this method yields a water permeation rate of 10−3 g/(m2⋅day) and oxygen permeation rate of less than 10−1 cm3/(m2·day·bar). Rapid curing at low-temperature processing along with barrier properties makes PHPS an ideal encapsulating material for organic solar cell devices and a variety of similar applications.
Highlights
Introduction published maps and institutional affilMany applications such as: solar cells [1] light-emitting diodes (LEDs) [2], organic transistors [3], and photodetectors [4] require encapsulating materials that should be transparent, and an excellent barrier against the diffusion of oxygen and moisture at the same time [5,6,7,8,9,10]
PHPS layers were coated on polyethylene/PET substrates via doctor blading with applicator gap set at 50 μm and coating speed of 5 mm·s−1
The optimization of the PHPS processing is performed in terms of curing method including treating the PHPS with room temperature, dry heating at 100 ◦ C, irradiation with deep UV, exposing the films to damp heat in controlled conditions of 65 ◦ C temperature along with fixed relative humidity level of 85% and simultaneous deep
Summary
Perhydropolysilazane (PHPS NN 120-20) diluted in di-n-butyl ether was received from. PET Melinex ST504 with a thickness of 125 μm was obtained from DuPont Teijin Films (Chester, PA, USA) and was used as a substrate after proper cleaning. Used low density polyethylene was obtained from local market and were used as the substrate. The films were deposited by blade coating (ZAA 2300, manufactured by Zehntner Testing Instruments, Sissach, Switzerland)
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