DE19722474A1 - Production of copper-indium-selenium solar cell - Google Patents

Abstract

Production of a copper-indium-selenium (CIS) solar cell comprises depositing a Se layer or a layer containing selenium in contact with an electrically conducting layer. The selenium layer or layer containing selenium is produced by galvanising.

Description

The invention relates to a method for producing a CIS thin-film solar cell, which is a layer of a ternary copper-indium-selenium alloy has as an absorption layer.

A solar cell is a device that converts light energy into electrical energy converts and generally comprises an electrically conductive substrate, on which an absorption layer is provided, which has a photoelectric Has conversion semiconductor, and on which also transmit a light turing electrode layer is provided. As a photoelectric conversion tion semiconductor layer (absorption layer) would have a thin layer of egg ner ternary copper-indium-selenium alloy (CuInSe₂; hereinafter referred to as "CIS" designated), in which the Cu / In / Se atomic ratio is 1/1/2, the highest photoelectric conversion efficiency.

JP-A-61-237476 describes a process for producing the above terna ren alloy (the abbreviation "JP-A" used here stands for an "unexamined published Japanese patent application"). The procedure includes the stages of galvanic deposition of copper and indium an electrically conductive substrate to form a precursor and that then heating the precursor in an inert gas stream, the selenium  contains hydrogen, forming a ternary copper indium selenium (CuInSe₂) alloy layer.

Although the electrically conductive substrate used above is titanium or platinum a molybdenum plate or carrier is generally used, on which a molybdenum layer is arranged. The reason for this is that the Thermal expansion coefficient and the lattice constant of molybdenum close with those of CIS and this is therefore a satisfactory one Adheres to a CIS layer.

The method for producing a CIS layer for use in a conventional CIS thin-film solar cell is explained in more detail below with reference to FIG. 4.

A molybdenum layer B, a copper layer C, an indium layer D and a selenium layer E are applied to a soda-lime glass (soda-lime glass) A as a substrate in the order mentioned by sputtering or the like, as shown in Fig. 4 (a). This multilayer structure is heated in the presence of hydrogen sulfide to give a CIS layer (see Fig. 4 (b)).

It would have been expected that the CIS layer adheres sufficiently to the molybdenum layer for the reasons given above. The CIS layer produced in this way, however, easily peels off and separates from it. A closer examination has shown that between the molybdenum layer of the substrate and the CIS layer, molybdenum selenide (represented by Mo _x Se _y , in which x and y each stand for a natural number) is arranged.

Fig. 5 shows the results of checking the distribution of copper, indium, selenium and molybdenum in the depth direction in cross section of a sample prepared by the above-described method using an energy dispersion X-ray analyzer. The results of FIG. 5 show the presence of a molybdenum selenide layer which is arranged between a CIS layer and a molybdenum layer.

The molybdenum selenide has a layer structure and this is the reason why the CIS layer provided on the molybdenum selenide layer separates from the substrate. The influence of the thickness of a layer between the molybdenum layer, which is an electrically conductive layer, and a CIS layer arranged on the molybdenum selenide layer on the adhesion of the CIS layer was examined (the thickness was determined using a scanning electron microscope and an energy dispersion X-ray analyzer ). The results obtained are shown in FIG. 6. The percentage of the detached area, as shown in Fig. 6, was determined by applying a commercially available pressure-sensitive (self-adhesive) adhesive tape (mending tape, manufactured by Sumitomo 3M Ltd., Japan) and then peeling it off and calculating the Ratio between the area on which the CIS layer had peeled off and the area on which the tape was applied.

Fig. 6 shows that the percentage of the detached area increases with increasing thickness of the molybdenum selenide layer. The tendency of a CIS layer to detach is disadvantageous in that solar cells which have such a CIS layer are difficult to handle, which leads to reduced yield in their production and to increased cell costs and in that the CIS obtained in this way Solar cells have inadequate performance and low durability.

To prevent the detachment of a CIS layer, JP-A-6-188444 describes Process for forming a layer containing selenium in contact with a Molybdenum layer described. This process creates during the Heat treatment to produce a ternary copper indium selenium Alloy layer Ternary alloy seed crystals around a layer in contact with the molybdenum layer and they grow towards the  Surface, and the surface of the alloy so produced layer has an excessively high degree of crystallinity and orientation on and as a result you get a solar cell with an excellent th conversion efficiency. Those described in JP-A-6-188444 Process actually obtained solar cell, however, shows an unsatisfactory Performance, although the CIS layer is prevented from becoming detached takes off and separates from it.

In order to solve the above problems, an object of the present is Invention to provide a method for manufacturing a solar cell, the has excellent photoelectric conversion efficiency while preventing detachment of the CIS layer.

These and other objects of the present invention are achieved by a method of manufacturing a CIS thin film solar cell comprising the step of:
Production of a selenium layer or a selenium-containing layer in contact with an electrically conductive layer, the selenium layer or the selenium-containing layer being produced by electroplating.

In addition, this and other objects of the present invention are accomplished by a method of forming a ternary copper-indium-selenium alloy in contact with an electrically conductive layer, which comprises the following steps:
Production of a selenium layer or a layer containing selenium on the electrically conductive layer by galvanization and
Application of a copper layer and an indium layer in the order mentioned or in the reverse order or a copper indium layer on the selenium layer or the layer containing selenium and
then heating in an atmosphere containing selenium.

The invention will now be described with reference to the accompanying Drawings explained in more detail.  

Fig. 1 shows views showing the step of the process according to the invention for producing a CIS type thin-film solar cell in accordance of one embodiment of explain (1: soda-lime glass; 2: chromium layer; 3: molybdenum layer (electrically conductive layer), 4: selenium layer; 5: Copper indium layer; 6 : CIS layer; 7 : cadmium sulfide layer; 8 : zinc oxide layer).

FIG. 2 shows the results of an analysis of a cross section of the CIS layer and the molybdenum layer, which were determined in Example 1 with an energy dispersion X-ray analyzer in the direction of the depth.

Fig. 3 shows curves IV for a solar cell A according to the invention and comparison solar cells E and F.

Fig. 4 explains a method for producing a CIS layer using a known method.

FIG. 5 shows the results of an analysis of a cross section of the CIS layer and the molybdenum layer, which have been produced using a known method, using an energy dispersion X-ray analyzer in the direction of the depth.

Fig. 6 is a graph showing the results of testing the influence of the thickness of a molybdenum selenide layer on the adhesion of a CIS layer.

As a result of extensive investigations with the be in JP-A-6-188444 The method described was found to be on a molybdenum layer arranged selenium layer has a fine surface roughness.

The surface roughness of the selenium layer (thickness: 15 nm) was measured with a Surface roughness knife of the tracer type determined and the obtained  Results are shown in Table I. The surface roughness of the Iybdenum layer (which is arranged on a soda-lime glass surface) also checked before the application of the selenium layer and is in Table I. given.

Table I

It is believed that the selenium layer surface roughness, such as that shown in Fig. 1, causes fine component unevenness during the manufacture of a ternary copper-indium-selenium alloy, and that the unevenness causes the growth of the CIS seed crystals formed near the selenium layer are inhibited, so that their orientation becomes insufficient. It is therefore believed that a solar cell with high photoelectric conversion efficiency can be obtained if such selenium layer surface roughness is eliminated. The present invention is based on this.

The application of a selenium layer or a layer containing selenium by electroplating as described above is effective with respect to the achievement of a CIS thin film solar cell with a high photoelectri conversion efficiency, as it is when using the conventional Vacuum deposition processes including vapor deposition are not is achievable. Since the resulting CIS layer has a high peel or peel resistance, the solar cell can also during manufacture position can be handled easily and it can be done at a low cost in high Yield can be made.  

Under the term "selenium layer" used here a layer is to be ver stand, which consists essentially of selenium, and under the use here The term "layer containing selenium" is understood to mean a layer which contains a selenium compound or elemental selenium, for example one Selenium alloy layer or a selenium dispersion layer.

Under the term "galvanization" used here is any Wet electroplating, for example a conventional electroplating, a Electroless plating and a method for producing a thin film by adsorption of colloidal particles (hereinafter referred to as "colloidal gal vanization "referred to) to understand.

An embodiment of the present invention is explained below with reference to FIG. 1.

Fig. 1 illustrates the steps of the process for producing a CIS solar cell of the present invention. The substrate which is used in the method shown in FIG. 1 comprises soda lime glass 1 as a support, onto which a chromium layer 2 and also a molybdenum layer 3 are applied as an electrically conductive layer; however, other substrates can also be used. For example, a substrate comprising molybdenum (e.g. a molybdenum plate) or a substrate having a chrome layer (a chrome plate) on which a molybdenum layer is arranged can be used. The use of soda-lime glass is advantageous in that the CIS layer which is arranged on the glass hardly detaches due to its coefficient of thermal expansion during the heat treatment for producing the CIS layer, which is described in more detail below.

As shown in Fig. 1 (a), soda-lime glass 1 having a chromium layer 2 and a molybdenum layer 3 (as an electrically conductive layer), which were applied by de by sputtering, is used as the substrate. On the molybdenum layer 3 , a selenium layer or a layer containing selenium is applied by electroplating as shown in Fig. 1 (b). In the embodiment shown in Fig. 1, it is not a selenium-containing layer, but a selenium layer and this selenium layer is indicated by the reference number 4 .

Although the galvanization (coating) to produce a selenium layer or a layer containing selenium a chemical coating (chemical electroplating), electro-coating (electro-electroplating) or can be a colloidal coating (colloidal electroplating), it is required to select the coating conditions so that a Thickness unevenness is reduced. At this stage the application is one Electroplating (electroplating) is desirable because it is a selenium layer with a smoother surface.

When using electroplating to create a layer that elemental selenium or a selenium alloy, it is preferred to use a To use electroplating bath acidified with sulfuric acid and contains an aqueous selenium dioxide solution (selenic acid). In this case it is Adding a brightener such as trisodium citrate is preferred because it is effective in for further reduction in thickness unevenness.

It can also be used to perform the dispersion coating together with copper or indium, or with both, a coating bath is used the one containing selenium powder or colloidal selenium dispersed therein. It is also possible the coating using a combination of these ben perform, for example a selenium coating bath, the Contains selenium powder or colloidal selenium dispersed therein.

Examples of substances that are absorbed together with selenium can be separated include indium and copper. Any of these sub punch or a combination of two or more of the same can be made on one  electrically conductive layer along with selenium are deposited under Formation of a layer containing selenium.

The coating described above is useful among such Conditions performed that the resulting selenium layer or selenium containing layer has a thickness of 50 nm to 1 micron. If their thickness is below 50 nm, the effects achieved according to the invention are insufficient. If on the other hand, if its thickness exceeds 1 µm, the excess selenium evaporates during the heat treatment described below, resulting in the first of cavities leading to detachment and cracking fen.

A copper layer and an indium layer are applied in the order mentioned or in the reverse order to the selenium layer or layer containing selenium thus produced. Alternatively, a copper indium layer is applied to the selenium layer or the layer containing selenium. The copper and indium layers or the copper indium layer is applied by electroplating (coating) or another film deposition technique, for example by sputtering. The incorporation of selenium powder or fine selenium particles in the deposited layer (in at least one layer in the case of the deposition of two layers, ie a copper layer and an indium layer) is effective to achieve a satisfactory CIS layer that is free of cracking and detachment. The fine selenium particles to be incorporated can be obtained from a selenium colloid. In the embodiment shown in FIG. 1 (c), a copper indium layer 5 was applied to the selenium layer 4 . According to the invention, the copper indium layer is a galvanized layer that has been applied by coating from a galvanizing bath that contains copper and indium.

From the viewpoint of the photoelectric conversion efficiency of the The thickness of the CIS solar cell to be manufactured is considered  Copper layer and the indium layer or that of the copper indium layer preferably set such that the one described below Heat treatment produced CIS layer has a thickness of 1 to 3 microns.

The resulting multilayer structure is heat-treated in an atmosphere containing selenium to grow the CIS crystals so as to obtain a CIS layer (see Fig. 1 (d)). Examples of the selenium-containing atmosphere include an inert gas (z. B. He, Ar, N₂) containing Selenwas serstoff or selenium vapor. However, it should be noted that the use of selenium vapor is preferred because selenium hydrogen is highly toxic.

Selenium vapor can be obtained by using solid selenium such as selenium powder in a closed container in which the precursor is heat-treated should be delt.

The heat treatment can be carried out at 350 to 500 ° C. A be preferred range of temperature for heat treatment is 400 to 500 ° C, because such a heat treatment turns a solar cell with a particularly high conversion efficiency is available. The treatment the duration is usually around 30 to 120 minutes.

As a result of this heat treatment, seed crystals grow out of a ternary Copper-indium-selenium alloy around a layer made with the molybdenum is in contact as a result of the presence of selenium, which affects the Selenium layer or the layer containing selenium, which is due to the electrically conductive layer is in contact. Because the selenium layer or the Selenium-containing layer produced by galvanization (coating) has a reduced thickness unevenness, the grow CIS seed crystals slightly towards the surface during heat act, creating a CIS layer with an extraordinarily high degree Crystallinity and orientation is maintained. Because the applied CIS layer  is impermeable to selenium because of the high stability of the CIS crystals, ver the CIS layer prevents selenium from penetrating into the molybdenum layer the gas phase. As a result, the formation of molybdenum selenide is prevented different.

Thereafter, a layer comprising cadmium sulfide (CdS), which is is an n-type semiconductor, or a layer, the zinc selenide which is also an n-type semiconductor the CIS layer thus produced is applied, for example by vapor deposition dung. To produce the n-type CdS semiconductor layer, in addition to Vapor deposition is the separation from a chemical bath (CBD) be turned.

The thickness of the CdS layer is preferably 0.02 to 0.3 μm. If the Thickness of the CdS layer is less than 0.02 µm, the CIS layer is included CdS not completely covered. If its thickness exceeds 0.3 µm, the CdS layer has a reduced light transmission. Hence thicknesses lead the same, which are outside the above range, into one reduced photoelectric conversion efficiency.

Finally, a layer of an aluminum-doped zinc oxide (ZnO) is applied as a window layer by sputtering to improve the electrical conductivity in order to complete a thin-film solar cell (see FIG. 1 (e)).

The thickness of the ZnO layer is preferably 0.5 to 2 μm. If the fat the ZnO layer is less than 0.5 µm, the series resistance increases, resulting in a leads to increased loss. If its thickness exceeds 2 µm, the light will take off transmission and this not only leads to a reduced conversion efficiency, but also to increase costs.  

If the thin film solar cell thus obtained is used, if it required to apply an anti-reflective layer and the like, and An end wires attached to this layer and with the electrically conductive Substrate connected.

The present invention has the following effects. Seed crystals a ternary copper-indium-selenium alloy grow around a layer to be in contact with the molybdenum layer as a result of the presence of selenium, that on the selenium layer or the layer containing selenium, which with the elec tric conductive layer is in contact. Because the selenium layer or the layer containing selenium, which is produced by coating has a reduced thickness unevenness, grow the CIS seed crystals slightly towards the surface, creating a CIS layer with an extraordinarily high degree of crystallinity and orientation tion is obtained. As a result, CIS solar cells are used with a recorded photoelectric conversion efficiency in good yield receive.

The present invention is illustrated below by the following examples explained in more detail without being limited thereto.

Example 1 and Comparative Example 1 Generation of an electrically conductive layer

On a soda lime glass with a thickness of 1 mm were 0.2 µm thick Chromium layer and a 2.0 µm thick molybdenum layer applied by sputtering brings. The average centerline surface roughness of the molybdenum layer determined with a tracer type surface roughness meter 0.7 nm.  

Generation of a selenium-containing copper indium layer in contact with the electrically conductive layer

An electrical coating (galvanization) was carried out in a gal for 2 min Vanization bath carried out, which was prepared by dissolving 10 mmol / l copper sulfate (CuSO₄), 50 mmol / l indium sulfate (In₂ (SO₄) ₃), 10 mmol / l Selenium dioxide (SiO₂), 50 mmol / l trisodium citrate and 500 mmol / l sulfuric acid in water, using a platinum plate as the counter electrode and one Mercury (I) sulfate electrode as a reference electrode at a constant Potential of -1.0 V, based on the mercury (I) sulfate electrode. To this A copper indium layer containing selenium (thickness: 50 nm) was formed the thin layer of molybdenum is applied.

The average centerline surface roughness of those containing selenium The copper indium layer was measured to be 2.6 nm.

Creation of a CIS layer

The coating (electroplating) was in a copper electroplating for 2 minutes Sierungsbad carried out, which had been prepared by dissolving 0.2 mol / l copper sulfate (CuSO₄) and 0.1 mol / l sodium sulfate (Na₂SO₄) in water using a copper plate as a counter electrode at a constant Current density of 30 mA / cm². In this way, a copper layer was placed on the Above mentioned, selenium-containing copper indium layer applied.

Another coating (electroplating) was carried out for 2.5 min in an In dium electroplating bath made by Dissolve 50 mmol / l indium sulfate (In₂ (SO₄) ₃), 80 mmol / l sodium sulfate (Na₂SO₄) and 25 mmol / l trisodium citrate in water, using a Platinum electrode as counter electrode with a constant current density of 10 mA / cm². In this way, an indium layer was applied to the copper layer brought.  

The resulting multilayer film, which contains the selenium-containing copper indium layer, the copper layer and the indium layer was covered on his Composition analyzed with a fluorescence X-ray spectrometer. As a result, it was found that the atomic ratio of copper / indium / selenium Was 37/41/22.

This multilayer film was made in nitrogen together with selenium powder 60 heated to 500 ° C for min and then in terms of its composition analyzed. As a result, it was obtained that the atomic ratio Kup fer / indium / selenium was 23/25/52, which was close to the stoichiometric zu composition for the ternary copper-indium-selenium alloy. The so CIS layer obtained (thickness: 2 µm) was in a satisfactory state before without detachment and without cracks.

Assessment of the CIS layer

On each of the five samples prepared in the same manner as described above, a commercially available self-adhesive tape (mending tape manufactured by Sumitomo 3M Ltd.) was applied to the CIS layer and then peeled off to determine whether the CIS layer has peeled off (this peeling resistance evaluation method is hereinafter referred to as "tape test"). As a result, detachment only occurred in one of the five samples, which shows that the CIS layer applied by the process according to the invention had extraordinarily good adhesion to the electrically conductive layer (Example 1). A cross-section of the CIS layer remaining in the sample where peeling had occurred was examined with an energy dispersion X-ray analyzer. The results obtained are shown in FIG. 2.

As shown in Fig. 2, in this sample of Example 1, the CIS layer was in direct contact with the electrically conductive layer (molybdenum layer) and no molybdenum selenide layer had formed between the two layers.

The same method for producing a CIS layer as in Bei game 1 carried out, with the exception that no selenium-containing Copper indium layer in contact with the electrically conductive layer was brought. This time five samples (Comparative Example 1) were made which each had a CIS layer (in which the atomic ratio Kup fer / indium / selenium was 23/25/52). The five samples were the same Kle belt test. As a result, peeling occurred in four samples.

In addition, the same method for creating a CIS layer as that carried out in Example 1, except that instead of Erzeu a copper indium layer containing selenium by electroplating a selenium layer (thickness: 15 nm) directly on the electrically conductive layer was applied by vapor deposition. In this way, five Samples (Comparative Example 2) obtained. These samples were the same Duct tape test. As a result, peeling occurred in two samples on. The average centerline surface roughness of-by sputtering The applied selenium layer was measured to be 3.2 nm.

Example 2 Generation of a selenium layer in contact with the electrically conductive layer

A chrome layer was placed on a soda lime glass with a thickness of 1 mm and then a layer of molybdenum by sputtering in the same way as in Example 1 deposited. The coated glass plate was left in for 30 minutes a solution of colloidal selenium immersed to produce a selenium  layer (thickness: 100 nm) on the molybdenum layer by colloidal coating tung (galvanization).

The colloidal selenium solution used was prepared from a Stock solution of colloidal selenium by diluting the stock solution to to a selenium concentration of 10 mmol / l.

The colloidal selenium stock solution was prepared by mixing 4 ml of an aqueous gelatin solution (4 g / l) with 10 ml of an aqueous selenium acid solution (0.1 mol / l), 10 ml of an aqueous hydrazinium sulfate solution (0.1 mol / l) and 30 ml of water, heating the mixture for 45 min at 40 ° C and on then adjust the pH to 2 to close the resulting colloid stabilize. The addition of gelatin served to stabilize the colloid. Col loidal particles of the colloidal selenium solution thus prepared were examined with a scanning electron microscope. As a result found that the colloidal selenium particles had an average portion Chen diameter of 10 to 100 nm. The stock solution was extreme stable and no precipitation of selenium particles occurred even if they were left to stand for a long period of time.

The average centerline surface roughness of the selenium so produced layer was 4.0 nm as measured. On this selenium layer a copper layer and an indium layer by electroplating on the same che manner as in Example 1 applied. The resulting multilayer film (consisting of the selenium layer, the copper layer and the indium layer) was determined with a fluorescence X-ray for its composition spectrometer analyzed. As a result, it was found that the atomic ver ratio copper / indium / selenium was 48/45/7.

Production and evaluation of the CIS layer

This multilayer film was made in a nitrogen atmosphere together with Selenium powder heated to 500 ° C for 60 minutes and then with respect to its composition analyzed. As a result, it was found that the atomic ratio Copper / indium / selenium was 24/26/50. The CIS layer thus obtained (Thickness: 2 µm) was in a satisfactory condition without detachment and without cracks. As a result of the tape test, it was found that none of the five samples detached.

A cross section of the CIS layer of one of these samples was made with an ener x-ray analyzer analyzed. As a result, it was found that there is no between the CIS layer and the electrically conductive layer Molybdenum selenide layer had formed.

Example 3 Production of a selenium-containing copper layer in contact with the elec tric conductive layer

On a soda lime glass with a thickness of 1 mm a chrome layer and then a layer of molybdenum by vapor deposition in the same way applied as in Example 1. Then electroplating was carried out for 1 min a galvanizing bath carried out by dissolving 10 mmol / l Copper sulfate (CuSO₄), 10 mmol / l selenium dioxide (SeO₂), 50 mmol / l trisodium citrate and 500 mmol / l sulfuric acid had been prepared in water Use of a platinum plate as a counter electrode at a current density the substrate surface of 10 mA / cm². In this way it became a selenium containing copper layer (thickness: 15 nm) on the thin molybdenum layer brought.

The average center line surface roughness of the Se thus produced copper layer was measured to be 2.6 nm The copper layer containing selenium became an indium layer by electroplating  sation applied in the same manner as in Example 1, but with the Exception that the electroplating time was regulated. The resulting one Multilayer film (consisting of the copper layer containing selenium and the indium layer) was compared with its composition with a Fluorescence X-ray spectrometer analyzed. As a result, it was found that the atomic ratio copper / indium / selenium was 23/25/52.

Production and evaluation of the CIS layer

This multilayer film was heated in the same manner as in Example 1 and then analyzed for its composition. As a result de found that the atomic ratio copper / indium / selenium was 23/25/52. The CIS layer thus obtained (thickness: 2 μm) was satisfactory Condition before without detachment and without cracks. As a result of the tape test it was found that no detachment occurred in four of the five samples, detachment only occurred in the remaining sample (Example 3).

A section (cross section) of the remaining, non-detachable CIS layer in the sample where peeling occurred was used of an energy dispersion X-ray analyzer. As a result de confirms that there is between the CIS layer and the electrically conductive Layer had not formed a molybdenum selenide layer.

Example 4 Production of a selenium-containing indium layer in contact with the elec tric conductive layer

On a soda lime glass with a thickness of 1 mm a chrome layer and then a layer of molybdenum by sputtering in the same way as in Bei game 1 upset. Then a coating was placed in a galva for 2 min nization bath prepared by dissolving 50  mmol / l indium sulfate (In₂ (SO₄) ₃, 10 mmol / l a solution of colloidal selenium (It became the stock solution of colloidal selenium used in Example 2 used), 25 mmol / l trisodium citrate and 500 mmol / l sulfuric acid in Was ser, using a platinum plate as a counter electrode for a current density of 30 mA / cm². In this way, an indium containing selenium layer applied to the thin molybdenum layer.

The average center line surface roughness of the Se thus produced len containing indium layer was 50 nm. On this containing selenium Indium layer was a copper layer by electroplating on the same Applied as in Example 1, except that the Gal vanization time was regulated. The resulting multilayer film (best from the indium layer containing selenium and the copper layer) with regard to its composition with a fluorescence X-ray spectro meters analyzed. As a result, it was found that the atomic ratio Copper / indium / selenium was 37/41/22.

Production and evaluation of the CIS layer

This multilayer film was heated in the same manner as in Example 1 and then analyzed for its composition. As a result de found that the atomic ratio copper / indium / selenium was 23/25/52. The CIS layer thus obtained (thickness: 2 μm) was satisfactory Condition before without detachment and without cracks. As a result of the tape test it was found that no detachment occurred in three of the five samples, detachment only occurred in the two remaining samples (Example 4).

A section (cross section) of the remaining CIS layer in one of the both samples with detachment were treated with an energy Dispersion X-ray analyzer examined. As a result, it was found that between the CIS layer and the electrically conductive layer Molybdenum selenide layer had formed.  

Assessment as a solar cell

Among those in Examples 1 to 4 and Comparative Examples 1 and 2 The samples obtained were selected for those with no interference including a detachment. For each of the selected A cadmium sulfide layer was deposited from a sample chemical bath, as described below, applied to the CIS layer brings:

The soda lime glass with the above described thin layers were placed in a 0.01 mol / l aqueous solution of Cadmium sulfate (CdSO₄) (with a pH of 8.5, with ammonia water had been immersed) of 70 ° C. Then a 0.01 mmol / l added aqueous solution of thiourea and the glass was placed in the resulting mixture kept immersed for 5 min to a cadmium to let the sulfide layer grow. Then the glass was rinsed with water washed and dried in nitrogen. The cadmium sul obtained in this way fidschicht had a thickness of 0.05 microns.

For each sample, a 2 µm thick zinc oxide layer, with 2 wt .-% Aluminum was doped, applied to the cadmium sulfide layer. To this Thin film solar cells A to F were thus obtained. Among the solar obtained cells occurred only in those in which the samples of Comparative Example 1 had been used (thin-film solar cell E), a relatively strong detachment and cracking in a peripheral portion thereof. Also kicked one of the four solar cell samples in which the samples of the comparison game 2 had been used (thin-film solar cell F), cracking in a peripheral portion thereof. In contrast, they were conditions in which the samples of Examples 1 to 4 had been used (Thin film solar cells A to D), free from such defects.  

In each of the CIS thin film solar cells A to D, the properties of a circular portion with a diameter of 2 mm, which was in the center of the cell, were determined with a solar cell output property analyzer (manufactured by WACOM Co.) . The results obtained are given in Table II. The IV curves for solar cells A, E and F are shown in FIG. 3.

Table II

Table II and FIG. 3 show that the CIS thin-film solar cells according to the invention were superior in terms of their output properties to the solar cells E and F according to the prior art.

While the invention has been described above with reference to specific be preferred embodiments explained in more detail, but it is for the expert it goes without saying that it is by no means limited to this, but that these can be changed and modified in many ways without thereby leaving the scope of the present invention.

Claims (11)

1. A method for producing a CIS thin film solar cell, characterized in that it comprises the deposition of a selenium layer or a selenium-containing layer in contact with an electrically conductive layer, wherein the selenium layer or the selenium-containing layer is generated by electroplating. 2. The method according to claim 1, characterized in that the selenium containing layer containing copper or indium. 3. The method according to claim 1 and / or 2, characterized in that the layer containing selenium contains copper and indium. 4. The method according to at least one of claims 1 to 3, characterized ge indicates that a copper layer and an indium layer in the genann order or in reverse order or a copper-in dium layer on the selenium layer or the layer containing selenium be brought, which is followed by heating in an atmosphere containing selenium re connects. 5. The method according to at least one of claims 1 to 4, characterized ge indicates that at least one layer from the group copper layer and Indium layer or the copper-indium layer contains selenium. 6. The method according to at least one of claims 1 to 5, characterized ge indicates that the electrically conductive layer is a molybdenum layer or is a chrome layer on which a molybdenum layer has been applied. 7. A method of forming a ternary copper-indium-selenium alloy in contact with an electrically conductive layer, characterized in that it comprises the following steps:
Generation of a selenium layer or a layer containing selenium on the electrically conductive layer by electroplating and
Application of a copper layer and an indium layer in the order mentioned or in the reverse order or a copper indium layer on the selenium layer or the layer containing selenium and
then heating in an atmosphere containing selenium. 8. The method according to claim 7, characterized in that the selenium containing layer containing copper or indium. 9. The method according to claim 7 and / or 8, characterized in that the layer containing selenium contains copper and indium. 10. The method smelled at least one of claims 7 to 9, characterized ge indicates that at least one layer from the group copper layer and Indium layer or the copper-indium layer contains selenium. 11. The method according to at least one of claims 7 to 10, characterized ge indicates that the electrically conductive layer is a molybdenum layer or is a chrome layer on which a molybdenum layer has been applied.