The interest in hybrid materials as barrier systems has beenincreased in the last decades as a result of the requirements to develop much more sophisticated materials in fields such as solar cells, optics, electronics, food packaging, etc. New barrier coating materials based on ORMOCER1 have been developed by Fraunhofer ISC which together with a vapour-deposited SiOx layer guarantee sufficient protection to ensure a long durability of encapsulated solar cells (see Fig. 11(a)).
This new inorganic–organic hybrid coating represents a whole encapsulation system since apart from the physical encapsulation it acts as an adhesive/sealing layer barrier against water vapour and gases, as well as an outside layer for weatherability. All these functions are combined in one composite (''one component encapsulant'') and in this way the overall cost reduction for encapsulation reaches about 50 per cent. The flexible nature of this hybrid material results in an optimized encapsulation process and especially in good protection of the edge area, the most difficult part for protection. Furthermore, this new material can be used from the roll, thus providing easy handling and automation in the production of flexible modules (Fig. 11(b)). Thin barrier layers like SiOx combined with ORMOCER1 based barrier coatings save material and energy consumption in the production of the new encapsulating material. Therefore, a material and energy saving encapsulation technology is achieved. This result should encourage the application of thin film solar cells in the building industry as well as the number of users of solar cells.
Especially flexible thin film solar cells cover broader fields of application because they can be adapted to non-planar surfaces. This means that photovoltaic (PV) devices could be a standard integrated part of construction components, in e.g. roofing materials, fac¸ades, and balustrades. Thus, a larger number of potential users could benefit from solar technology. Upcoming and future products require flexible films that have high barrier or even ultra-high barrier properties. The encapsulation film for solar modules is one important example which illustrates that there is still a great need for the development of improved polymer barrier systems. The basis of most of the barrier coatings are polycondensates of some percentage of Al alkoxides with phenyl- and epoxyfunctionalised alkoxysilanes.
Further developments on patternable barriers/passivation with good dielectric properties for application in roll-to-roll processing of polymer-electronic devices and systems are on the way for up-scaled technology and production at Fraunhofer ISC.141 Sol–gel chemistry has been extensively applied to produce thin oxide coatings with appropriate protective behavior onto metal substrates.142 Nevertheless, protection of metallic silver reflectors, for example, should resist not only gaseous oxidation but also mechanical and chemical attacks during handling, cleaning or weathering of the metal parts. Laser labs have developed a silica-based hybrid material to protect silvercoated light reflectors installed in laser pumping cavities as shown in Fig. 12.143 These metallic reflectors require a protective overlayer in order to preserve the high-reflectivity front surfaces for long periods of operation under intense broadband flashlamp light and typical airborne contaminants.
The organically modified silica coating has been optimized in terms of thickness and composition to enhance metal resistance to oxidation and tarnishing under UV-irradiation and ozone-attack. To fulfil these requirements, the hybrid sol– gel material not only must act as an oxidation dense barrier but also needs to be chemical-resistant, time-stable and to remain transparent. On the other hand, industrial protective coating deposition onto large-sized and multi-shaped metallic parts is allowed by using the dip-coating technique. The protection efficiency is mainly related to the density of the hybrid coating, and can be managed varying the sol–gel chemistry conditions (hydrolysis rate) and oxide content.
Furthermore, hybrid material compared to pure inorganic allows one to enhance the chemical resistance through incorporation of hydrophobic surface functions, such as methyl groups, which also reduce coating stress allowing a thicker film deposition onto eventually deformable substrates. This hybrid layer preserves the high reflectance of silver over a broad spectral range and enables silver reflectors to withstand a very corrosive medium with no appreciable degradation.
This new inorganic–organic hybrid coating represents a whole encapsulation system since apart from the physical encapsulation it acts as an adhesive/sealing layer barrier against water vapour and gases, as well as an outside layer for weatherability. All these functions are combined in one composite (''one component encapsulant'') and in this way the overall cost reduction for encapsulation reaches about 50 per cent. The flexible nature of this hybrid material results in an optimized encapsulation process and especially in good protection of the edge area, the most difficult part for protection. Furthermore, this new material can be used from the roll, thus providing easy handling and automation in the production of flexible modules (Fig. 11(b)). Thin barrier layers like SiOx combined with ORMOCER1 based barrier coatings save material and energy consumption in the production of the new encapsulating material. Therefore, a material and energy saving encapsulation technology is achieved. This result should encourage the application of thin film solar cells in the building industry as well as the number of users of solar cells.
Especially flexible thin film solar cells cover broader fields of application because they can be adapted to non-planar surfaces. This means that photovoltaic (PV) devices could be a standard integrated part of construction components, in e.g. roofing materials, fac¸ades, and balustrades. Thus, a larger number of potential users could benefit from solar technology. Upcoming and future products require flexible films that have high barrier or even ultra-high barrier properties. The encapsulation film for solar modules is one important example which illustrates that there is still a great need for the development of improved polymer barrier systems. The basis of most of the barrier coatings are polycondensates of some percentage of Al alkoxides with phenyl- and epoxyfunctionalised alkoxysilanes.
Further developments on patternable barriers/passivation with good dielectric properties for application in roll-to-roll processing of polymer-electronic devices and systems are on the way for up-scaled technology and production at Fraunhofer ISC.141 Sol–gel chemistry has been extensively applied to produce thin oxide coatings with appropriate protective behavior onto metal substrates.142 Nevertheless, protection of metallic silver reflectors, for example, should resist not only gaseous oxidation but also mechanical and chemical attacks during handling, cleaning or weathering of the metal parts. Laser labs have developed a silica-based hybrid material to protect silvercoated light reflectors installed in laser pumping cavities as shown in Fig. 12.143 These metallic reflectors require a protective overlayer in order to preserve the high-reflectivity front surfaces for long periods of operation under intense broadband flashlamp light and typical airborne contaminants.
The organically modified silica coating has been optimized in terms of thickness and composition to enhance metal resistance to oxidation and tarnishing under UV-irradiation and ozone-attack. To fulfil these requirements, the hybrid sol– gel material not only must act as an oxidation dense barrier but also needs to be chemical-resistant, time-stable and to remain transparent. On the other hand, industrial protective coating deposition onto large-sized and multi-shaped metallic parts is allowed by using the dip-coating technique. The protection efficiency is mainly related to the density of the hybrid coating, and can be managed varying the sol–gel chemistry conditions (hydrolysis rate) and oxide content.
Furthermore, hybrid material compared to pure inorganic allows one to enhance the chemical resistance through incorporation of hydrophobic surface functions, such as methyl groups, which also reduce coating stress allowing a thicker film deposition onto eventually deformable substrates. This hybrid layer preserves the high reflectance of silver over a broad spectral range and enables silver reflectors to withstand a very corrosive medium with no appreciable degradation.
Asignatura: CRF
Fuente: www.rsc.org/materials Journal of Materials Chemistry
Ver: http://nanocompositescrf.blogspot.com/
Fuente: www.rsc.org/materials Journal of Materials Chemistry
Ver: http://nanocompositescrf.blogspot.com/
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