DE19707280A1 - Climate and corrosion-stable layer structure - Google Patents

Abstract

The invention relates to a weather- and corrosion-resistant layer structure whereby a layer structure which has at least one corrosion- and/or moisture-sensitive layer, such as a solar cell, is encapsulated in such a way that it is weather- and corrosion-resistant by placing a barrier layer over said corrosion- or moisture-sensitive layer. Thin-layers consisting of titanium- or molybdenum nitride, aluminum oxide, silicon nitride and silicon oxynitride are provided for this purpose. The barrier layer can be combined with a supplementary laminate structure of the type found in solar cells.

Description

The invention relates to a layer structure with at least one egg ner arranged on a substrate moisture and / or corrosion-sensitive layer, especially an optical one and / or electrically active thin film. Such layers be can be found, for example, in optical or electrical construction elements. Examples of this are radiation-sensitive construction elements such as detectors, solar cells or so Larmodule, or optoelectronic components such as wise display devices and in particular LCD screens.

In order to meet the quality requirements in demand on the market, solar modules need a number of different test procedures run through successfully. One of these procedures that the Kli is to check the dimensional stability of the solar modules Damp heat climate test. According to the well-known standard IEC 1215 among other things, the modules for 1000 hours of a tempe temperature of 85 ° C at 85 percent relative humidity exposed.

Laminated solar modules with boron-doped zinc oxide electrodes show an unusually strong degradation in this test method, i.e. an inadmissibly high decrease in efficiency after the climate test. The main reason for this is their instability with regard to the conductivity of the boron-doped CVD zinc oxide layers against water vapor at elevated temperatures. As could be shown on test laminates consisting only of a laminated zinc oxide layer provided with test electrodes, the surface resistance of such layers increases after the test by a factor of more than 10 ^{3 to a} value of more than 1 kΩ / square. To achieve a high fill factor in solar modules, however, a value of less than 10 Ω / square is required. This cannot be achieved by a simple encapsulation with a laminate structure with the aid of an adhesive film and possibly a second glass pane.

Find more climate and corrosion sensitive components thin-film solar modules made of copper indium (Gallium) diselenide (CIGS). There the absorber shows Degradati Signs of appearance on the surfaces that are unprotected or only covered the climate with a conventional laminate structure test conditions are suspended. The best made of molybdenum rear electrode there are additional climate-independent De gradations at the interface to the CIGS absorber layer.

One way of diffusing moisture into one To prevent laminate and in particular in a solar module, be stands for the extension of the diffusion distance Humidity. For laminates with a sufficiently wide Edge of more than 15 cm will degradation of a board dope sufficiently delayed zinc oxide layer. Such a wider one Edge is however with a solar module because of the then high to partly inactive module surface unacceptable.

The object of the present invention is to keep a moist layer structure that is insensitive to corrosion and / or corrosion admit that simple and without too high additional ferti production effort is to be produced and both compared to the specified test conditions as well as with a conventional Use has increased stability.

According to the invention, this object is achieved by a Layer structure according to claim 1. Preferred embodiments of the Invention and a method for producing the layer construction can be found in further claims.

Surprisingly, it has been shown that a moisture and / or corrosion-sensitive layer by an additional and applied directly above the layer in simple way in front of a climate and especially damp  degradation or corrosion-related degradation can. With such an additional barrier layer can for example, thin-film solar modules can be obtained that the Damp-heat climate test mentioned at the beginning without any noteworthy lei overlap and without visible corrosion damage hen.

In a preferred embodiment of the invention Layer structure Part of an electrical or optical component ment, in which the barrier layers a vapor barrier and / or have a corrosion protection effect, being optically active and / or working with electrical potential differences Parts of the component with electrically insulating lock layers are covered, layers with no potential difference against with conductive barrier layers.

The moisture and / or corrosion sensitive layer in the sense of the invention is a substrate-bound layer, which can be applied as a thin or thick layer and is amorphous, polycrystalline or metallic.

In a preferred embodiment of the invention, the additional barrier layer is a thin layer which is selected from aluminum oxide Al ₂ O ₃ , silicon nitride Si ₃ N ₄ , titanium nitride TiN, molybdenum nitride MoN and silicon oxynitride SiO _x N _y . Such a thin layer is simple and inexpensive to manufacture and can be easily integrated into the manufacturing process of the moisture or corrosion-sensitive layer or the layer structure or component containing this layer, especially if the layer structure itself is a thin layer structure.

This is used to produce the layer according to the invention no additional equipment is required. Since the Barrier layer adapts to the function of the covered layer and for example optically transparent, electrically conductive or isolating, it shows no negative influence on the  Layer structure. It does not affect the operation of any Layer structure containing optical or electrical construction elements still deteriorates its properties.

The thin-film barrier layers mentioned can be used as density, d. H. pore-free, optically transparent and edged Deposit opaque layers in known processes. In Ab dependence on the density or freedom from pores with which egg ne such a layer can be created, can already Barrier layer of 100 nm thickness should be sufficient to a complete protection against moisture and / or corrosion guarantee. A thicker barrier layer is of course possible but not required. With deposition processes that are not too completely non-porous or not completely homogeneous or not will not lead to barrier layers covering the edges well preferably selected a higher layer thickness. If high topo There are graphical levels on the layer structure for good edge coverage of the barrier layer a layer thickness up to approx. 2 µm.

Good edge coverage is achieved with a CVD process enough. Particularly preferred for making both you barrier layers that cover the edges as well Layer thickness at the lowest possible deposition temperatures are plasma-assisted CVD processes.

The barrier layer points to most as electrical or materials used optical functional layer a good Liability on. If necessary, an adhesion promoter can also be used layer may be required.

Since the layer structure according to the invention as the barrier layer additional layer to the conventional one or any has many layers comprising layer structure, it can still with a conventional cover, for example with be covered with a laminate structure. It is with solar modules especially a laminate, which is at least still an art  layer of material and optionally a protective film and / or includes a glass cover plate. Art is preferred a hot melt adhesive layer on which the Ab cover film and optionally laminated the glass pane are. Other components can additionally over the barrier layer Lich or alternatively with other covers, for example covered with cast resin layers or other potting compounds or be wrapped.

In an application of the invention for space-related or The only barrier is the use of solar cells layer as the top and covering layer for protection sufficient for the solar cell.

The barrier layer according to the invention is in particular for one Suitable for laminate construction, since they adhere well under conventional hot melt adhesive used for this purpose has layers. The good adhesion of the hot melt adhesive film and thus the entire laminate structure leads to an additional Lich improved seal that the diffusion of Moisture along the interfaces between the layer structure and Laminate or between barrier layer and laminate other.

In the layer structure according to the invention, the barrier layer is edge-covering so arranged above the layer to be protected net that their entire surface including the pages walls is covered. On the side of the sensitive layer closes the barrier layer with a climate-stable layer. Such layers are resistant to moisture and / or hot and damp environments are dense and also show long distances no corrosion or other disadvantageous exposure change.

The barrier layer preferably encloses the moisture sensitive thin film from above and from the side and excludes on the bottom edge with the example  Glass existing substrate, a metal layer or a Passivation layer. The passivation layer can if there is a barrier layer. In addition to those already for the Materials called barrier layer is also for special Applications still suitable for silicon oxide. Titanium and molybdenum nitride can and are set to be electrically conductive also particularly hard and scratch-resistant. It is therefore as a pas sivierungsschicht for especially metallic and therefore principally corrosion-sensitive electrode layer net, especially as a lower electrode for thin layered components are used. On all of the above The barrier layers show good adhesion and layers thus form moisture-tight and chemically stable interfaces level out to these layers.

In one embodiment of the invention, the layer structure is an electrical component with at least two electrodes, where an electrode is made from a directly above the substrate orderly electrode layer is formed. This electro The layer can be used to manufacture the above-mentioned electrode be structured and thus represent an electrode structure len, as they are especially for integrated series-connected Thin-film solar modules is suitable.

In addition to the required electrode structure, you can also the electrical connections for the at least two elec formed from this lower electrode layer and led out laterally from the area of the component the. Such an arrangement has the advantage that it is opposite a conventional arrangement with, for example, soldered electrical connections particularly flat without additional Structural levels can be formed. This makes it easier edge covering covering with the barrier according to the invention layer.

That from the layer structure of the component under the barrier layer led out and from the first electrode layer  trained electrical connections can be made from one corrosion-resistant metal. They are preferably however with the electrically conductive passivation mentioned layer, in particular a titanium or molybdenum nitride layer covered. The passivation layer can be the lower electro Completely cover the layer and according to this be structured. It is also possible to lower the electric layer only in the field of electrical applications cover with the passivation layer, and esp special only in the area of making connections under the barrier layer.

Another advantageous embodiment of the invention be meets the aforementioned CIGS thin-film solar modules. How for example from the German patent DE 44 42 824 C1 is a defined alka in the CIGS absorber layer content for maximum efficiency of the solar cell conducive. Because a defi The alkali content of the CIGS absorber layer is only one Alkali barrier layer directly over the glass substrate or over the back electrode layer can be achieved for such a barrier layer in an advantageous manner barrier designed according to the invention as a passivation layer Insert layer over the base or back electrode. A Barrier layer made of titanium or molybdenum nitride can be the same early as a passivation layer for those leading to the outside electrical connections or as a barrier for serve the entire lower electrode. An additional It has a special barrier layer over the solar cell good adhesion and thus forms a particularly good and dense interface to the barrier layer.

The process according to the invention is subsequently Development of a climate-stable thin-film arrangement using Aus examples and the accompanying eight figures explained.  

Fig. 1 shows a schematic cross section through a test arrangement with a climate-sensitive thin layer.

FIGS. 2 to 5 show schematic cross-sections through cli mastabile layer arrangements.

Fig. 6 shows by way of schematic cross-section of a layer arrangement with joints prior to the applications of the barrier layer.

FIGS. 7 and 8 show reference to schematic cross-sections through a series-connected thin-film solar cell is a special application of the invention.

Fig. 1 shows a structure serving as a test thin-film element with a known encapsulation. On a carrier 1 , consisting of a 2 mm thick window glass (soda-lime glass), a 1.5 µm thick boron-doped zinc oxide layer 2 is applied by means of the CVD method so that the carrier 1 remains free in the entire peripheral edge area. On two opposite sides, metal contact strips 3 are now soldered so that the electrical surface conductivity of the zinc oxide layer 2 can be determined reliably. A conventional laminate structure 5 is now produced, for example by laminating an approximately 0.5 mm thick EVA film at approximately 160 ° C. The laminate structure with the substrate on the side of the thin-film arrangement has an overlap area of 1 cm.

This test setup is now 1000 hours at 85 ° C in one At exposed to 85 percent humidity. Here shows that the sheet resistance of the boron-doped zinc oxide layers after the climate test from previously unknown Reasons increases by two to three orders of magnitude.  

Fig. 2 now shows a first structure according to the invention, in which a boron-doped zinc oxide layer 2 arranged on a substrate 1 with strips 3 applied thereon is used as the test structure. According to the invention, a barrier layer 4 is now brought up over this arrangement. In the exemplary embodiment, a plasma CVD method is used for application, which can be carried out at low process temperatures of, for example, 200 to 300 ° C. In the example, a barrier layer 4 of approximately 0.5 to 2 μm and in particular 0.8 μm thick silicon nitride is deposited at 200 ° C. in a plasma CVD process. The barrier layer is deposited in such a way that the thin layer 2 is completely covered with the barrier layer 4 . Using a similar process, the likewise electrically insulating Al ₂ O ₃ and SiO _x N _y layers can also be used as barrier layers. In addition, as already described in FIG. 1, a laminate structure 5 is brought up.

The thin-layer arrangement according to the invention survives the Kli matest without detectable degradation, i.e. without the initial surface conductivity of the thin film is reduced. Because this parameter is an excellent probe as set out for the detection of exposure to moisture this measurement result the high effectiveness of the invention Encapsulation.

Fig. 3 shows a schematic cross section of a layer structure in which a moisture-sensitive layer and in particular a thin layer 2 is arranged between a lower electrode 3 a and an upper electrode 3 b on a substrate 1 . To avoid additional topography steps and to achieve a planar arrangement as possible, electrical specific terminals 6 are provided which are formed directly on the substrate by patterning the lower electrode layer 3 a being. While the lower electrode 3 a is contacted via an electrical connection 6 , the upper electrode 3 b is connected to the electrical connection 6 ', which is iso liert by a structure line electrically from the lower electrode 3 a. A barrier layer 4 is now applied over this arrangement, which completely covers the upper electrode 3 b and the thin layer 2 . By masking or by subsequent structuring of the barrier layer, the electrical connections 6 and 6 'are exposed and not covered by the barrier layer 4 .

By applying a laminate structure 5 according to FIG. 1 or 2, the climate-tight encapsulation of the component shown here can be reinforced. In the execution example, the electrical connections 6 and 6 'remain free of laminate. The thin-film component can, for example, be a solar cell.

Fig. 4 shows a further embodiment of the invention. This differs from the embodiment according to FIG. 3 in that the lower electrode layer 3 a is completely covered with a metallically conductive coating layer 7 before structuring. The further structure speaks ent the game described with reference to FIG. 3.

In this way it is achieved that the lower electrode layer, which may consist of a corrosion-sensitive metal, for example, by the electrically conductive passivation layer 7 is also protected against moisture and other external corrosion-promoting effects.

This arrangement is realized, for example, in a CIGS solar cell which, for example, a glass substrate 1 , a Mo lybdenum back electrode 3 a, a titanium or molybdenum nitride passivation layer 7 , the thin layer 2 with the semiconductor transition CIGS absorber layer, and an upper electrode 3 b , for example, includes a boron-doped zinc oxide electrode. The barrier layer 4 is a thin layer of aluminum oxide, silicon nitride or silicon oxynitride applied by CVD or plasma CVD.

The embodiment according to FIG. 5 differs from the embodiment described with reference to FIG. 4 because the lower electrode layer 3 a is only covered with an electrically conductive passivation layer 7 and 7 ′ in the area of the electrical connections 6 and 6 ′. For this purpose, the passivation layer can be applied directly before the structuring of the lower electrode layer 3 a either masked or applied over the entire area and then structured. However, it is also possible to generate the passivation layer 7 and 7 'after the application of the thin layer 2 or after the application of the upper electrode layer 3 b.

In all cases, the passivation layer is thin layering processes such as reactive sputtering or with deposited using a plasma-assisted CVD process or sputtered on. For a titanium nitride layer, for example 100 to 150 nm layer thickness is sufficient.

Fig. 6 shows on the basis of a schematic cross section a possibility of structuring a thin layer 2 arranged between two electrodes 3 a and 3 b by means of two separating joints 8 extending to a climate-stable layer, in order to subsequently apply a barrier layer 4 (not shown) in the joints 8 to achieve a climate-tight seal or a climate-tight adhesion of the barrier layer on the underlying climate-stable layer. In the example of Fig. 6, a passivation layer 7 serves to the unte ren electrode 3 a as a climate-stable layer. It is also possible, however, to expose the substrate 1, for example made of glass, or a corrosion-resistant electrode layer 3 a in the parting lines 8 . In these cases, the application of the passivation layer 7 over the entire surface can be omitted.

FIGS. 7 and 8 show reference to schematic cross sections of a solar module with series-connected integrated Thus, a further embodiment larzellen in thin-film structure of the invention. The solar cell is applied, for example, to a substrate 1 and comprises a lower electrode 3 a, a thin layer 2 with the semiconductor structure and an upper electrode 3 b. The solar cells are structured, for example, in the form of strips, a series connection with the respectively adjacent strip-shaped solar cell being achieved by leading down a strip-shaped upper electrode 3 b to the respectively adjacent strips of the lower electrode 3 a.

To structure the thin-film solar cell arrangement shown in FIG. 7, three structuring steps are necessary. The first structuring step serves for structuring the lower electrode 3 a, the second for structuring the semiconductor layers (thin layer) 2 and the third for separating the upper electrode 3 b. In the latter structuring step, either the semiconductor layer (thin layer 2 ) or the lower electrode layer 3 a is exposed. In FIG. 7, a patterning trenches reaching P3 shown to the lower electrode 3.

Fig. 8 now shows how the patterning trenches are filled by depositing a barrier layer 4 kantenbedeckenden P3 and leveled by clogging. The barrier layer 4 is applied to a surface that extends beyond the layer structure on all sides and also overlaps the electrical connections 6 and 6 '. Over the electrical connections 6 and 6 ', the barrier layer 4 can then be partially removed again, so as to enable an external electrical connection, for example by soldering metal strips 9 .

Provided that the deposition conditions for the barrier layer 4 bezüg Lich the deposition temperature are chosen so that Lötstel len remain undamaged, in a further embodiment of the invention, the barrier layer can also be done after soldering the metal strip 9 so that the solder joint is covered by the barrier layer 4 becomes. In this way, the passivation layer ( 7 ) for the lower electrode 3 a can be omitted. With the invention, the climate- and corrosion-stable encapsulation of any layer structures and in particular large-area thin-layer arrangements that have climate- and corrosion-sensitive layers succeed. It is particularly suitable for the climate-tight encapsulation of solar cells, but of course it is not restricted to such. The invention is particularly suitable for those thin-film arrangements which are exposed to hot and / or humid environments. Of course, this also applies to layer structures that are usually not exposed to such corrosion-supporting environmental conditions.

Claims (12)

1. layer structure,

• - which is optically and / or electrically active and is arranged above a substrate ( 1 ),
• - With at least one corrosion and / or moisture sensitive layer ( 2 ) and
• - With at least one barrier layer ( 4 ) which is arranged on the corrosion and / or moisture-sensitive layer ( 2 ).
• - In which the barrier layer ( 4 ) is a thin layer and is selected from Al ₂ O ₃ , Si ₃ N ₄ , TiN, MoN and SiO _x N _y .

2. Layer structure according to claim 1, in which a laminate structure ( 5 ) with at least one plastic layer is arranged over the barrier layer ( 4 ). 3. Layer structure according to claim 1 or 2, in which the barrier layer ( 4 ) forms tight and edge-covering. 4. Layer structure according to one of claims 1 to 3, wherein the barrier layer ( 4 ) to the side of the corrosion and / or moisture-sensitive layer ( 2 ) containing the structure with the substrate ( 1 ), with a metal layer or a passivation layer ( 7 ) . 5. layer structure according to one of claims 1 to 4,

• - is part of an electrical or optical component,
• - In the case of optically active and / or differences in electrical potential working parts of the component are covered with insulating vapor barrier or corrosion protection layers,
• - in which layers with no potential difference are covered with conductive vapor barrier or corrosion protection layers.

6. Layer structure according to one of claims 1 to 5, wherein the lower electrode layer ( 3 a) at least in the loading area of the electrical connections ( 6 , 6 ') is covered with an electrically conductive barrier or passivation layer ( 7 ). 7. layer structure according to claim 6, which is designed as a solar cell or solar module. 8. Process for the production of a climate and corrosion-stable layer structure,

• - in which a barrier layer ( 4 ) is deposited to cover the edges over a heat-sensitive and / or moisture-sensitive layer ( 2 ) arranged on a substrate ( 1 ),
• the barrier layer is selected from MoN, TiN, Al ₂ O ₃ , Si ₃ N ₄ and SiO _x N _y ,
• - The barrier layer is deposited in a thickness of 100 nm to 2 microns.

9. The method according to claim 8, wherein the barrier layer ( 4 ) is deposited with an optionally plasma-assisted CVD process. 10. The method according to any one of claims 8 or 9,

• - In which in the thin layer ( 2 ) a circumferential self-contained parting line ( 8 ) is first produced, in which the surface of a climate-stable layer of the thin-film structure is exposed
• - With the thin layer ( 2 ) superficially and on all sides edges with the barrier layer ( 4 ) is covered so that the barrier layer in the joint closes with the surface of the kli mastable layer.

11. The method according to any one of claims 8 to 10, in which a laminate structure ( 5 ) with at least one plastic layer is applied over the barrier layer ( 4 ). 12. Use of the method according to one of claims 8 to 11 for climate-stable encapsulation of solar cells and solar modules.