Therefore, taking advantages of the transparency and flexibility, polymer matrices can be utilized as a quality barrier by incorporating nanoparticles. Hence, the use of a monolayer coatings is still of great interest in the polymeric industry, along with enhanced barrier and mechanical characteristics. Moreover, they need unique adhesives for their bonding, which further complicates their formation and are very hard to recycle. Though these two techniques, polymer blending and multilayer development, possess good barrier characteristics and are economical packaging materials, they have high production costs. Other than using multilayers, direct blending of polymers is also an important technique to achieving barrier characteristics. This strategy can effectively be utilized to reduce the permeation of both, the moisture and oxygen. Hence, multilayers are created with alternating layers of hydrophilic and hydrophobic materials. To protect EVOH from water, it must be sandwiched in between a material that is hydrophobic and insoluble in water. For instance, EVOH film is used in humid environments to provide a barrier against oxygen, although EVOH is a hydrophilic material it serves as a decent barrier against oxygen. In general, no pure polymer exists that shows all the required mechanical and barrier characteristics for all packaging applications, so combinations of different layers or blends of polymers are used for particular applications. However, in a moist environment (e.g., >75% relative humidity), its rate of oxygen transmission can be increased by one order of magnitude, owing to the swelling of the polymer in a water environment. The barrier characteristics against any specific permeating molecule can be enhanced by various factors, for instance, ethylene vinyl alcohol (EVOH) offers outstanding barrier characteristics to oxygen in a dry environment. Except for polymers, all other materials are extremely rigid but offer high-quality barrier characteristics. In the food packaging industry, 40% of the market share is being performed by polymers. One of the main advantages of polymers is their easy processability, since they can be processed using simple coating techniques, such as spin coating, doctor blading, spray coating, etc. Among all these options, polymers are presently widely used due to their inherent low density, cost effectiveness, as well as the diversity of their physiochemical stabilities. Lots of materials are being used and have been demonstrated for solar cell encapsulation, including metals, polymers, glass, and ceramics. The lifetime results confirmed that the stability of the OSCs was extended from few hours to over 240 h in a sun test (65 ☌, ambient RH%) which corresponds to an enhanced lifetime by a factor of 9 compared to devices encapsulated with pristine PVB. Finally, optimized barrier layers were used as encapsulation for organic solar cell (OSC) devices. The P3HT films coated with PVB/mica composite showed improved stability under constant light irradiation and exhibited a loss of <20% of the initial optical density over the period of 150 h. In the second step, a PVB/mica composite layer was applied on top of the P3HT film and subjected to photo-degradation. The resultant protective layers showed ultra-flexibility, as no significant degradation in protective characteristics were observed after 10 K bending cycles. The developed protective layer maintained a high transparency in the visible region and improved oxygen and moisture barrier quality by the factor of ~7. In the first step we developed a protective layer with cost effective and environmentally friendly methods and optimized its properties in terms of transparency, barrier improvement factor, and bendability. In this work we demonstrate solution-based effective barrier coatings based on composite of poly(vinyl butyral) (PVB) and mica flakes for the protection of poly (3-hexylthiophene) (P3HT)-based organic solar cells (OSCs) against photobleaching under illumination conditions. Organic photovoltaics (OPVs) die due to their interactions with environmental gases, i.e., moisture and oxygen, the latter being the most dangerous, especially under illumination, due to the fact that most of the active layers used in OPVs are extremely sensitive to oxygen.
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