Ultra high barrier materials for encapsulation of flexible organic electronics

Abstract

The encapsulation of the active layers (organic semiconductors, electrodes, transparent conductive oxides, etc.) of Organic Electronic devices developed onto flexible polymeric substrates is one of the most challenging issues in the rapidly emerging area of Organic Electronics. The importance for the protection of the active layers arises from the fact that these are very sensitive when they are subjected to the atmosphere, since the permeation of the atmosphere's water vapour (H 2 O) and oxygen (O 2 ) gases induces corrosion effects, film delamination and finally, failure of the organic electronic device. In addition, the encapsulation layers contribute to the long-term stability of the whole device enabling its use in outdoor environments (e.g. in the case of flexible photovoltaic cells-OPVs). A promising approach for the encapsulation of flexible organic electronics includes the development of multilayers that consist of hybrid polymer materials and inorganic layers onto flexible polymeric substrates, such as Poly(Ethylene Terephthalate) (PET). This approach leads to a significant improvement of the barrier performance of the whole structure, due to the synergetic effect of the confinement of the permeation to the defect zones of the inorganic layer, and the formation of chemical bonds between the hybrid polymer and the inorganic layer. The knowledge of their optical properties and their correlation with their barrier performance are of major importance since it will contribute Supprimé : response Supprimé : response 2 towards the optimization of their functionality. In this work, we provide an overview on the results concerning the use of hybrid polymers as ultra high barrier materials and moreover we discuss on the effect of inclusion of SiO 2 nano-particles on their optical properties and barrier performance.

High-barrier films for flexible organic electronic devices

“…Although this method is effective, it can be used only for applications that do not require transparency. Moreover, metal foils exhibit high surface roughness and different thermal expansion coefficients compared with other materials used in OEs (Logothetidis et al, 2010). • Glass: To be flexible, the thickness of the glass should be less than 100 mm and its mechanical properties are not desirable.…”

“…• Glass: To be flexible, the thickness of the glass should be less than 100 mm and its mechanical properties are not desirable. Moreover, its implementation in roll-to-roll processes increases the cost because a high-purity process is required (Logothetidis et al, 2010). • Inorganic thin films of metal oxides such as silicon oxide and aluminum oxide deposited onto a polymeric substrate.…”

Thickness Measurement Methods for Physical Vapor Deposited Aluminum Coatings in Packaging Applications: A Review

“…Those are applied via a sol-gel process in order to achieve a nanometer thin coating [11,12]. The very basic form of a sol-gel process is the draining and evaporation of the solvent, followed by condensation reactions [13].…”

“…When the evaporated material arrives on the surface, the thickness and mass increase. Therefore, Sauerbrey [68] introduced the mass density (ME) for the evaporated material and for the quartz material (MQ) which is defined by the thickness (d) and density (δ) as in Equations (10) and (11). Accordingly, when the thickness (d) increases, also the mass density (ME) increases.…”

“…Consequently, the change in frequency (∆f ) is related to the mass density (M E ) as in Equation (12). By combining Equations (8), (11) and (12), Equation (13) can be derived and it becomes obvious, that (∆f ) directly relates to the mass density of aluminum (M E ), as (v s ), (δ Q ) and (f ) are constant. This correlation was first mentioned by Sauerbrey [68] and is therefore denoted as the Sauerbrey-equation [66].…”