DE19611410C1 - Climate-stable electrical thin film structure - Google Patents

Abstract

Electrical thin film structure consists of a thin film device (2) located on a support (1) and covered by a glass sheet (5), at least the edge region of which is bonded or laminated by a plastic layer (4) to the support (1) and has a thin vapour barrier layer (7) comprising a 50-100 nm thick Si3N4 or Al2O3 layer. Also claimed is a method of producing the above thin film structure, in which (a) the electrical thin film device (2) is produced or positioned on the support (1); (b) the thin vapour barrier layer (7) is deposited on at least the edge region of the glass sheet; and (c) the device is covered with the glass sheet and at least the edge region is bonded by an adhesive layer (4) to the support such that the entire edge region is in contact with the adhesive layer.

Description

The invention relates to an electrical thin-film arrangement, in particular an electrical thin-film component, which laminated between a carrier and a glass cover plate is. Examples of such thin-film components are strah tion-sensitive components, for example detectors or Solar cells, or optoelectronic components as in for example 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 called steam-heat climate test. According to the well-known IEC standard The modules will be 1215 for 1000 hours, among other things a temperature of 85 ° C with 85 percent relative air exposed to moisture.

Laminated solar modules with boron-doped zinc oxide electrodes layers show an unusual in this test procedure severe degradation, i.e. an impermissibly high decrease in Efficiency after the climate test. Mainly responsible for it is the instability regarding the conductivity of the bordo cated CVD zinc oxide layers against water vapor at elevated Temperature. As could be shown on test laminates, the surface resistance of such zinc oxide layers increases the test by a factor of more than 10³ to a value of more than 1 kΩ / square. To achieve a high fill factor tors for solar modules is, however, less than 10 Ω / square required. This can be done by a simple ver encapsulation by lamination with the help of an adhesive film and egg ner second glass pane can not be reached.  

To solve this problem, WO 93/19491 A1 knows, rf-sputtered aluminum-doped zinc oxide as trans Parente front electrode to use. This has been in the steam-heat test proven stable and shows no change of the sheet resistance.

A disadvantage of sputtered ZnO: Al layers is, however high effort that this reactive sputtering process requires. When transferring the process to large-scale applications conditions as desired for thin-film solar modules also had problems that led to significant effects lead to degree losses. It can only be an unsatisfactorily low separation rate can be realized. In contrast, un equally cheaper CVD processes for generating (climate sensitive Licher) boron-doped zinc oxide layers is essentially simple cher perform and can be without loss of efficiency Carry out large areas with a high deposition rate.

Another way of diffusing in moisture Prevention in the solar module consists in the extension the diffusion path for moisture. At La minate with a sufficiently wide margin of more than 15 cm the degradation of the boron-doped zinc oxide front electrode sufficiently delayed. However, such a wide margin is we unacceptable due to the high proportion of inactive module surfaces.

An electrical, climate-stable thin-film arrangement is over JP 59-61971 A known. In this known arrangement is an electrical thin-film component on a carrier ordered, and the component is abge with a glass pane covers. Before the glass pane is glued to the carrier the edge of the glass sheet with concave and convex unevenness provided by containing a glass paste with one in it inorganic filler powder in the edge area of the glass disc is applied and heated for fusion welding. The bumps cause an improved bond and there  through greater resistance to intrusion Humidity.

The object of the present invention is a climate-stable Specify thin film arrangement that is simple and without too high Manufacturing effort is to manufacture and the specified Test conditions survive without inadmissible degradation.

This object is achieved by a thin Layer arrangement according to claim 1. Preferred configurations of the invention and a method for producing the thin layer arrangement can be found in the subclaims.

Surprisingly, it was found that one on a carrier ordered electrical thin-film component by gluing or laminating a first glass pane in a climate-stable manner can be covered if the first glass pane at least in Edge area a thin vapor barrier layer made of silicon nitride Si₃N₄ or aluminum oxide Al₂O₃ with a layer thickness of 50 to 100 nm. Such a layer can be in simpler Way and in sufficiently high deposition rates from one ent speaking target are sputtered on. Such a process can be easily installed in conventional production lines and requires, for example, in an inline continuous system due to the high deposition rate in Verbin with the small layer thickness no additional time expenditure.

Already a just about 5 mm wider with such a steam Barrier-coated peripheral edge area leads to a significantly increased stability of the thin-film component. Even a component that is special moisture-sensitive zinc oxide electrode layer, shows with a vapor barrier layer in an edge area from approx. 10 mm width and an additional full-surface cover the ZnO layer with approx. 100 nm another vapor barrier layer so high a climate stability that after the above  Damp-heat climate test (according to IEC 1215) is only an insignificant one Reduction of the conductivity of the zinc oxide electrode layer can be observed. After this test, the surface resistance increases such zinc oxide layers stood at values of less than 10 Ω / square. For solar cells, this value is sufficient to a high fill factor even for modules connected in series and therefore to achieve maximum efficiencies.

In one embodiment of the invention, the carrier also comprises a glass pane that runs around at least in the edge area  the said vapor barrier layer is provided. The thin ones Layer arrangement then has a layer sequence in the edge region Glass pane (carrier) / vapor barrier layer / plastic cling layer / vapor barrier layer / glass pane on. Under edge area a surface area on the first pane of glass understood the entire scope of an approximately con constant given width. Provided carrier and first glass are congruent, this definition applies analogously also for the edge area of the carrier. In the case of different Sizes of the carrier and the first glass pane are shown under Randbe always reach the edge of the part with the smaller area che understood. On the part with the larger area is the edge area provided with a vapor barrier layer Area that matches the edge area of the part with the smaller one Surface overlaps.

In a preferred embodiment of the invention, additionally directly above the electrical thin-film component another one before laminating on the first glass Vapor barrier layer applied in a thickness of 50 to 100 nm brings, for example by sputtering Al₂O₃.

The method for producing the thin films according to the invention Layer arrangement is described in the following with the help of exemplary embodiments play and the associated five figures explained in more detail.

Fig. 1 shows a thin layer arrangement in a conventional laminate construction in schematic cross section

Fig. 2 and 3 show two designs having vapor barrier layers

Fig. 4 shows measurement curves for the sheet resistance of the test structures after a climate test and

Fig. 5 shows an air-stable thin-film solar cell.

A test structure made of boron-doped zinc oxide is the best resistance layer produced on a carrier and by Laminating encapsulated with a sheet of glass. The area wi the state of this zinc oxide layer is an excellent indicator kator for the climate stability of the entire (encapsulated) Thin film arrangement.

Fig. 1 shows a thin-film element (test pattern) with known encapsulation. On a carrier 1 , consisting of egg ner 2 mm thick window glass (soda-lime glass), a 1.5 µm thick boron-doped zinc oxide layer 2 is applied with the CVD method so that the carrier 1 remains free in the entire circumferential area. On two mutually opposite sides metal contact strips 3 are now brought up so that the electrical surface conductivity of the zinc oxide layer 2 can be determined reliably. Additional attachment can be done using ultrasound soldering. An adhesive film 4 is now placed on this structure, for example a 0.5 mm thick EVA film with a bonding temperature of approximately 150 ° C. Another glass pane 5 serves as cover, for example in turn a 2 mm thick window glass pane.

This structure is now under pressure at a temperature of laminated at approx. 160 ° C.

Fig. 2 shows a first thin film arrangement according to the invention, which corresponds to the known from Fig. 1 conventional laminate with the difference that both the serving as a carrier de glass 1 and the cover plate 5 were previously provided with vapor barrier layers 6 , 7 . For this purpose, the glass panes 1 and 5 are provided with a 50 to 100 nm thick aluminum oxide layer in a sputtering system using an aluminum oxide target. The laminate is produced as described, the surfaces of the glass panes 1 and 5 which are not provided with vapor barrier layers facing outwards.

Fig. 3 shows a further thin film arrangement according to the invention, which was produced analogously in accordance with the previous exemplary embodiments until the zinc oxide layer 2 was produced. After the application of the zinc oxide layer 2 , however, a further vapor barrier layer 8 is generated over the entire surface by sputtering a 50 to 100 nm thick aluminum oxide layer. The further laminate structure with the adhesive film 4 and the first glass pane 5 provided with the aluminum oxide layer 7 is carried out as described.

The three laminates corresponding to the structures shown in FIGS. 1 to 3 are now subjected to a steam-heat climate test in accordance with IEC 1215. For this purpose, the laminates are kept in a water vapor-containing atmosphere of 85 percent relative humidity at 85 ° C for 1000 hours. By means of the applied contact strips 3, the surfaces of the zinc oxide layer 2 conductivity determined at regular intervals.

FIG. 4 shows the corresponding measurement curves, the measured surface resistance R being plotted in hours against the continuous test duration under climatic test conditions. Curve a corresponds to the measured values which were determined on the conventional laminate according to FIG. 1. The surface resistance increases steeply after just a few hours, starting with an initial value of approx. 5 ohms, and reaches a resistance value of 1010 Ω after 1000 hours of testing. The measurement curve b is measured on the laminate structure according to FIG. 2, in which two glass panes 1 and 5 provided with aluminum oxide layers 6 and 7 were used. As can be seen from the measurement curve ve b, the surface resistance remains approximately constant up to half of the test duration, in order to then also increase steeply. However, the increase in the structure according to FIG. 2 is significantly less than that with the known structure according to FIG. 1.

The measurement curve c is the measured value of the sheet resistance on the laminate structure according to FIG. 3. Samples with this structure showed only a relatively small change in resistance during the entire climate test, during which the surface resistance rose only slightly from 6 to 9 Ω. This thin-film arrangement can therefore be described as climate-stable, especially since the observed increase in surface resistance can possibly also be attributed to a purely thermal influence, which is completely independent of the quality of the climate-stable encapsulation.

Fig. 5 shows a schematic cross section as a further exemplary embodiment of a thin-film arrangement, an encapsulated solar cell according to the invention based on a chalcopyrite semiconductor as an absorber. This thin layer arrangement is also constructed on a support 1 which, as in the exemplary embodiments already described, consists of 2 mm thick window glass. A vapor barrier layer 6 made of 100 nm aluminum oxide is sputtered over the entire surface of the carrier 1 . Over this vapor barrier layer 6 , a solar cell is now produced in known process steps, which essentially consists of a 0.7 μm thick molybdenum back electrode 9 , a 1 to 2 μm thick chalcopyrite absorber layer 10 , an n-type window layer 11 from an approx. 10 to 50 nm thick cadmium sulfide layer and an electrode layer 12 consists of an approximately 1.5 µm thick boron-doped zinc oxide layer.

In the case of large-area application, the solar cell is preferably integrated in series connection, with each of the layers being applied over the entire area and being structured in strips in a subsequent structuring step such that a series connection of the strips results between the individual strips with the aid of overlapping electrode regions. The solar cell assembly 9 , 10 , 11 and 12 is then removed in an approximately 10 mm wide edge strip. In example with a sandblasting process, the carrier 1 can be exposed. The thin layer arrangement shown in FIG. 5 is based on the latter structure. At closing, the contact strips (not shown in the figure), which ensure the external electrical connection of the solar cell or of the integrated interconnected solar module to the outside, are applied, for example by dissolving.

This structure is now sealed like the embodiment already described in connection with Fig. 3 by means of a wide ren vapor barrier layer 8 made of 100 nm thick sputtered aluminum oxide, whereby the exposed edge of carrier 1 is coated with Al₂O₃. A first glass pane 5 made of 3 mm thick low-iron window glass (soda-lime glass) is used as the cover pane, onto which an approximately 100 nm thick vapor barrier layer made of aluminum oxide is sputtered. The lamination takes place by means of an adhesive foil 4 made of EVA.

The So obtained according to the invention encapsulated in a climate-stable manner larzelle shows compared to a conventionally laminated solar cell no additional loss of efficiency. This is on the high transparency and the favorable refractive index of the Attributed to alumina sputter layers. In high chip nungstest (isolation test) perform the invention Vapor barrier layers even improve results. The encapsulated solar cell according to the invention already shows be written climate test no loss of efficiency on the ZnO degradation would be attributable.

In addition to the specified embodiments, the Er on other solar cells, for example from amor phem or crystalline silicon or other thin film  transmit orders that contain aggressive chemical or kli are exposed to and against special influences who have to be protected. Possible application for the Er In particular, optoelectronic components are therefore found represents, for example radiation-sensitive components such as Sensors or thin-film display elements such as, for example LCD screens.

Claims (10)

1. Electrical thin-film arrangement with the features:

• - An electrical thin-film component ( 2 ) is arranged on a carrier ( 1 );
• - The component ( 2 ) is covered with a first glass pane ( 5 );
• - The carrier ( 1 ) is glued or laminated to the first glass pane ( 5 ) at least in the edge area with the aid of a plastic layer ( 4 ); and
• - The first glass pane ( 5 ) has at least in the edge area a thin coating with a vapor barrier layer ( 7 ) which comprises a 50 to 100 nm thick layer of Si₃N₄ or Al₂O₃.

2. Thin-film arrangement according to claim 1, wherein the carrier ( 1 ) comprises a further glass pane which has a thin vapor barrier layer ( 6 ) at least in the edge region. 3. Thin-film arrangement according to claim 2, in which a further vapor barrier layer ( 8 ) is arranged over the electrical thin-film component ( 2 ). 4. Thin-film arrangement according to one of claims 1 to 3, wherein the thin-film component ( 2 ) comprises a solar cell with a ZnO: B layer ( 12 ). 5. A method for producing a thin-film arrangement according to claim 1,

• - In which an electrical thin-film component ( 2 ) on egg nem carrier ( 1 ) is generated or arranged;
• - In which a thin vapor barrier layer ( 7 ) is deposited on a first glass pane, at least in the Randbe, which holds a 50 to 100 nm thick layer of Si₃N₄ or Al₂O₃; and
• - In which the component is covered with the first glass pane and at least in the entire edge area with an adhesive layer ( 4 ) is glued to the carrier so that the entire edge area is in contact with the adhesive layer.

6. The method according to claim 5, in which the first glass pane ( 5 ) and the carrier ( 1 ) are laminated and glued at elevated temperature with the aid of an adhesive film ( 4 ) arranged between them. 7. The method according to claim 5 or 6, in which a further glass pane with a vapor barrier layer ( 6 ) applied thereon is used as the carrier ( 1 ), which, prior to bonding, has layers ( 2 , 9 , 10 , 11 , 12 ) of the thin-film component is freed. 8. The method according to claim 7, in which a vapor barrier layer ( 8 ) is deposited over the entire surface on the carrier ( 1 ) arranged or generated electrical construction element ( 2 ). 9. The method according to any one of claims 5 to 8, wherein the vapor barrier layer ( 7 , 6 , 8 ) is applied by sputtering aluminum oxide in a thickness of 50 to 100 nm. 10. Use of the method according to one of claims 5 to 9 for the production of climate-stable thin-film solar modules.