DE102018114800A1 - Monofacial solar cell, solar module and manufacturing process for a monofacial solar cell - Google Patents

Abstract

The invention relates to a monofacial solar cell with a layer stack on the back, the layer stack on the back having an AlOx layer (1), one or more SiNx layers (2, 3, 5) and a SiOxNy layer (4). The invention further relates to a solar module which has a plurality of such monofacial solar cells. Furthermore, the invention relates to a manufacturing method for the monofacial solar cell, in which the back layer stack of AlOx layer (1), SiNx layer (s) (2, 3, 5) and SiOxNy layer (4) in a pipe PECVD system be deposited with a graphite boat as a wafer holder and the layers are applied in succession in one and the same tube.

Description

The invention relates to a monofacial solar cell, a solar module and a production method for a monofacial solar cell. In particular, the invention relates to a monofacial solar cell with a layer stack on the back and a solar module which has such a monofacial solar cell and a production method for the monofacial solar cell.

A solar cell usually has a front side and a back side, which can each have layer stacks. It is an electrical component that converts incident sunlight directly into electrical energy. Monofacial solar cells can only utilize light incident on their front, while bifacial solar cells can exploit incident sunlight from two sides. The bifacial solar cell can not only utilize direct incidence of light from the front but also direct or indirect incidence of light from the back, the latter for example in the form of reflected sunlight.

From the DE 10 2007 054 384 A1 a solar cell is known in which two dielectric layers and a metallization are arranged on a substrate such as a wafer. The two dielectric layers are an AlOx layer arranged on the substrate and SiNx, SiOx, or SiC layer arranged on the AlOx layer. However, there is still a need to increase the efficiency of the solar cell.

It is an object of the invention to provide a solar cell and a solar module as well as a manufacturing method for a solar cell which have an optimized efficiency.

According to the invention the object is achieved by a monofacial solar cell with the features of patent claim 1, a solar module with the features of patent claim 10 and a manufacturing method for a monofacial solar cell with the features of patent claim 11. Advantageous further developments and modifications are specified in the subclaims.

The invention relates to a monofacial solar cell with a back layer stack, in which it is provided according to the invention that the back layer stack has an AlOx layer, one or more SiNx layers and one or more SiOxNy layers. The respective SiNx or SiOxNy layers can differ in their refractive index.

This layer stack on the back increases the efficiency of the monofacial solar cell. Compared to a monofacial solar cell with a layer stack on the back consisting of an AlOx layer and a SiNx layer, this results in higher efficiency.

Due to the manufacturing process of SiNx and SiOxNy layers, for example in the PECVD process (plasma enhanced chemical vapor deposition process), hydrogen is deposited during the deposition of the layers, i. H. the SiNx layer or SiOxNy layer is hydrogenated, which is represented by the designation SiNx: H layer or SiOxNy layer: H layer. This hydrogen contained in such a layer passivates recombination centers at the SiNx / Si interface or SiOxNy interface and in the volume of the silicon substrate. This has a positive influence on the efficiency of the solar cell. The hydrogen content of the SiNx layer is preferably in the range from 10 to 25%, more preferably in the range from 15 to 20%. The hydrogen content of the SiOxNy layer is preferably below 10%. The production of the rear layer stack according to the invention is possible in a PECVD system in one process without ventilation or system change. This can save costs. All layers of the rear side stack are preferably deposited in a tube PECVD system with a graphite boat as a wafer holder by means of a direct plasma. However, it is also possible to deposit the AlOx using “atomic layer deposition” (ALD) or microwave remote plasma, and to only deposit the SiNx and SiOxNy layers in a tube PECVD system.

The monofacial solar cell is preferably a monocrystalline or multicrystalline solar cell which has a silicon substrate.

In a preferred embodiment, the AlOx layer is arranged on a substrate of the solar cell, the SiNx layer is arranged on a side of the AlOx layer facing away from the substrate and the SiOxNy layer is on a side of the SiNx layer facing away from the substrate arranged. In this embodiment, the rear of the monofacial solar cell has the following structure: substrate / AlOx layer / SiNx layer / SiOxNy layer. The layers of the layer stack are preferably arranged directly or directly one above the other, i.e. without another intermediate layer.

The SiNx layer is preferably a SiNx double layer which has a first SiNx layer and a second SiNx layer. The layer stack therefore preferably has four layers. The layer stack preferably consists of these four layers in the following order: AlOx layer / SiNx double layer / SiOxNy layer. It should always be noted that there is a. On the back of the solar cell additional backside metallization is present because it is a monofacial solar cell. That is, a metal layer is also arranged on the SiOxNy layer.

In a preferred embodiment, a third SiNx layer is arranged on a side of the SiOxNy layer facing away from the substrate. This can further increase the efficiency of the monofacial solar cell. In addition, the compatibility of such a layer stack with a screen printing paste, in particular an aluminum screen printing paste, for realizing the rear side metallization of the monofacial solar cell is further improved. The metal layer arranged on the third SiNx layer is therefore preferably an aluminum layer.

In a preferred embodiment, the layer stack has four layers. The layer stack preferably consists of the four layers in the following order: AlOx layer / SiNx layer / SiOxNy layer / SiNx layer. In another preferred embodiment, the layer stack has five layers. The layer stack preferably consists of the five layers in the following order: AlOx layer / SiNx double layer / SiOxNy layer / SiNx layer. It should also be noted here in each case that there is still an additional rear side metallization on the rear side of the solar cell.

A refractive index of the first SiNx layer is advantageously smaller than a refractive index of a second SiNx layer, the first SiNx layer being arranged on a side of the second SiNx layer facing away from the substrate and the second SiNx layer on one of the substrate facing away from the AlOx layer. In this embodiment, the solar cell preferably has the following structure on the back: substrate / AlOx layer / second SiNx layer / first SiNx layer / SiOxNy layer or substrate / AlOx layer / second SiNx layer / first SiNx layer / SiOxNy- Layer / third SiNx layer. The refractive index of the third SiNx layer is preferably smaller than the refractive index of the second SiNx layer. More preferably, the refractive index of the third SiNx layer is the same or substantially the same as the refractive index of the first SiNx layer.

Advantageously, a refractive index of the SiOxNy layer is smaller than a refractive index of the SiNx layer, i.e. the first, second and third SiNx layers. In particular, the refractive index of the SiOxNy layer can be greater than a refractive index of the AlOx layer.

In a preferred embodiment, the refractive index of the AlOx layer is in the range from 1.5 to 1.7, the refractive index of the SiNx layer is in the range from 2.0 to 2.4 and the refractive index of the SiOxNy layer is in the range from 1.5 to 1.9, measured by means of laser or white light / spectral ellipsometry at a wavelength of 632 nm. If the SiNx layer is an SiNx double layer, a refractive index of the first SiNx layer is preferably in the range of 2, 0 to 2.2 and a refractive index of the second SiNx layer in the range from 2.2 to 2.4. If the layer stack has the third SiNx layer, a refractive index of the third SiNx layer is preferably in the range from 2.0 to 2.2. In the range of these values, the monofacial solar cell has a high level of light coupling and a high passivation effect is achieved.

A total layer thickness of the layer stack is preferably at least 80 nm, preferably at least 105 nm, more preferably at least 115 nm, even more preferably at least 120 nm. As a result, a higher open-circuit voltage and a higher efficiency are achieved both when incident light from the front and when incident from the rear. The total layer thickness of the layer stack is preferably in the range from 100 to 210 nm, more preferably in the range from 110 to 140 nm, more preferably at 125 nm. This results in improved resistance to paste corrosion in the production of the monofacial solar cell. In addition, quantitatively more hydrogen is provided for a chemical passivation of the surface and the volume.

A layer thickness of the SiOxNy layer is preferably greater than a layer thickness of the SiNx layer. If the SiNx layer is a SiNx double layer, a layer thickness of the SiOxNy layer is preferably equal to or greater than the layer thickness of the Sinx double layer. A layer thickness of the AlOx layer is preferably smaller than the layer thickness of the SiNx layer. In a preferred embodiment, a thickness of the AlOx layer is in the range from 5 to 20 nm, a thickness of the SiNx layer arranged on a side of the AlOx layer facing away from the substrate is in the range from 15 to 70 nm, and a thickness is of the SiOxNy layer in the range from 20 to 200 nm, more preferably in the range from 50 to 170 nm. A thickness of the first SiNx layer is preferably in the range from 10 to 40 nm, and a thickness of the second SiNx layer is in the range of 5 to 30 nm and the thickness of the third SiNx layer is in the range from 5 to 55 nm. In the range of these values, the monofacial solar cell has a high level of light coupling and a high passivation effect is achieved.

In a preferred embodiment, the back layer stack consists of the following four layers: an AlOx layer arranged on the substrate, the second SiNx layer arranged on the side of the AlOx layer facing away from the substrate, the first on that of the substrate SiNx layer arranged away from the side of the SiNx layer and the SiOxNy layer arranged on the side of the first SiNx layer facing away from the substrate. In this embodiment, the refractive index of the AlOx layer is preferably in the range from 1.5 to 1.7, more preferably at 1.6, the refractive index of the second SiNx layer is preferably in the range from 2.2 to 2.4, the refractive index the first SiNx layer in the range from 2.0 to 2.1, and the refractive index of the SiOxNy layer in the range from 1.5 to 1.9, measured as indicated above.

In another preferred embodiment, the back layer stack consists of the following five layers: an AlOx layer arranged on the substrate, the second SiNx layer arranged on the side of the AlOx layer facing away from the substrate, the first on the side of the SiNx facing away from the substrate Layer arranged SiNx layer, the SiOxNy layer arranged on the side of the first SiNx layer facing away from the substrate and the third SiNx layer arranged on the side of the SiOxNy layer facing away from the substrate. In this embodiment, the refractive index of the AlOx layer is preferably in the range from 1.5 to 1.7, more preferably at 1.6, the refractive index of the second SiNx layer is preferably in the range from 2.2 to 2.4, the refractive index the first and third SiNx layers in the range from 2.0 to 2.1, and the refractive index of the SiOxNy layer in the range from 1.5 to 1.9, as measured above.

In yet another preferred embodiment, the back layer stack consists of the following four layers: an AlOx layer arranged on the substrate, the first or second SiNx layer arranged on the side of the AlOx layer facing away from the substrate, and on the side facing away from the substrate the first or second SiNx layer arranged SiOxNy layer and the third SiNx layer arranged on the side of the SiOxNy layer facing away from the substrate. In this embodiment, the refractive index of the AlOx layer is preferably in the range from 1.5 to 1.7, more preferably at 1.6, and the refractive index of the second SiNx layer is preferably in the range from 2.2 to 2.4, if appropriate. the refractive index of the optionally first and third SiNx layers in the range from 2.0 to 2.1, and the refractive index of the SiOxNy layer in the range from 1.5 to 1.9, measured as indicated above.

As already mentioned above, the expression that the layer stack consists of the layers mentioned means that a back-side metallization is also provided on the back layer stack.

The invention further relates to a solar module, comprising a plurality of monofacial solar cells according to one or more of the above embodiments. The efficiency of the solar module is increased. The solar module is preferably monofacial.

The invention further relates to a manufacturing method for the monofacial solar cell according to one or more of the described embodiments, in which the rear layer stack of AlOx layer, SiNx layer (s) and SiOxNy layer is deposited in a pipe PECVD system with a graphite boat as a wafer holder and the layers are applied in succession in one and the same tube.

• 1 einen Schichtstapel gemäß dem Stand der Technik;
• 2 einen erfindungsgemäßen Schichtstapel;
• 3 einen weiteren erfindungsgemäßen Schichtstapel;
• 4a einen noch weiteren erfindungsgemäßen Schichtstapel;
• 4b eine Variante des in 4a gezeigten Schichtstapels;
• 5a einen noch weiteren erfindungsgemäßen Schichtstapel;
• 5b-5d jeweils eine Variante des in 5a gezeigten Schichtstapels.

Further properties and advantages of the invention are shown in connection with the figures and are described below by way of example. They show schematically and not to scale:

• 1 a layer stack according to the prior art;
• 2 a layer stack according to the invention;
• 3 a further layer stack according to the invention;
• 4a a still further layer stack according to the invention;
• 4b a variant of the in 4a layer stack shown;
• 5a a still further layer stack according to the invention;
• 5b -5d each a variant of the in 5a layer stack shown.

1 shows a layer stack according to the prior art. This known layer stack is applied in two layers and on the back of a substrate (not shown). The layer stack consists of an AlOx layer 1, which is arranged on the substrate (not shown), and a first SiNx layer 2, which is arranged on a side of the AlOx layer 1 facing away from the substrate. Furthermore, a metal layer (not shown) is arranged on the SiNx layer 2.

2 shows a layer stack according to the invention. The layer stack according to the invention is applied in three layers and on the back to a substrate (not shown). The layer stack has an AlOx layer 1, which is arranged on the substrate (not shown), an SiNx layer 2, which is arranged on a side of the AlOx layer 1 facing away from the substrate, and an SiOxNy layer 4, which is on a side of the SiNx layer 2 facing away from the AlOx layer 1 is arranged. A metal layer of the monofacial solar cell arranged on a side of the SiOxNy layer 4 facing away from the SiNx layer 2 is not shown.

The AlOx layer 1 has a refractive index of 1.6, as measured above, and a layer thickness of 16 nm. The SiNx layer 2 has a refractive index of 2.05, as measured above, and a layer thickness of 20 nm. The SiOxNy layer 4 has a refractive index of 1.7, as measured above, and a layer thickness of 70 nm.

3 shows a further layer stack according to the invention. The in 3 layer stack shown corresponds to that in 2 layer stack shown on the back, with the difference that a further SiNx layer 3 is arranged between the AlOx layer 1 and the SiNx layer 2. The SiNx layer 2 and the SiNx layer 3 form an SiNx double layer 2, 3, which is arranged on a side of the AlOx layer 1 facing away from the substrate. The second SiNx layer 3 has a refractive index of 2.4, as measured above, and a layer thickness of 20 nm.

4a shows yet another layer stack according to the invention. The in 4a layer stack shown corresponds to that in 2 Layer stack shown with the difference that a third SiNx layer 5 is further arranged on a side of the SiOxNy layer 4 facing away from the substrate. The third SiNx layer 5 has a refractive index of 2.05, as measured above, and a layer thickness in the range of 20 nm.

4b shows a variant of the in 4a layer stack shown. The in 4b layer stack shown corresponds to that in 4a Layer stack shown with the difference that instead of the SiNx layer 2, an SiNx layer 3 is arranged with a refractive index of 2.4, as measured above, and a layer thickness of 20 nm.

5a shows yet another layer stack according to the invention. The in 5a layer stack shown corresponds to that in 3 Layer stack shown with the difference that a third SiNx layer 5 is further arranged on a side of the SiOxNy layer 4 facing away from the substrate. The third SiNx layer 5 has a refractive index of 2.05, as measured above, and a layer thickness in the range of 50 nm.

5b -5d each shows a variant of the in 5a layer stack shown.

5b shows a back layer stack according to 5a with the difference that the layer thickness of the third SiNx layer 5 is 20 nm.

5c shows a back layer stack according to 5a with the difference that a refractive index of the SiOxNy layer 5 is 1.5, as measured above.

5d shows a back layer stack according to 5a with the difference that the layer thickness of the SiOxNy layer 5 is 150 nm.

LIST OF REFERENCE NUMBERS

1

AlOx layer

2

first SiNx layer

3

second SiNx layer

4

SiOxNy layer

5

third SiNx layer

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102007054384 A1 [0003]

Claims (11)

Monofacial solar cell with a back layer stack, characterized in that the back layer stack has an AlOx layer (1), one or more SiNx layers (2, 3, 5) and a SiOxNy layer (4). Monofacial solar cell after Claim 1 , characterized in that the AlOx layer (1) is arranged on a substrate of the solar cell, the SiNx layer (2, 3) is arranged on a side of the AlOx layer (1) facing away from the substrate and the SiOxNy layer (4) is arranged on a side of the SiNx layer (2, 3) facing away from the substrate. Monofacial solar cell after Claim 1 or 2 , characterized in that the SiNx layer (2, 3) is a SiNx double layer which has a first SiNx layer (2) and a second SiNx layer (3). Monofacial solar cell after Claim 2 or 3 , characterized in that a third SiNx layer (5) is arranged on a side of the SiOxNy layer (4) facing away from the substrate. Monofacial solar cell after Claim 3 or 4 , characterized in that a refractive index of the first SiNx layer (2) is smaller than a refractive index of a second SiNx layer (3), the first SiNx layer (2) on a side of the second SiNx layer facing away from the substrate (3) is arranged and the second SiNx layer (3) is arranged on a side of the AlOx layer (1) facing away from the substrate. Monofacial solar cell according to one of the preceding claims, characterized in that a refractive index of the AlOx layer (1) is in the range from 1.5 to 1.7, a refractive index of the SiNx layer (2, 3, 5) in the range of 2.0 to 2.4 and a refractive index of the SiOxNy layer (4) is in the range from 1.5 to 1.9, measured by means of ellipsometry at a wavelength of 632 nm, preferably a refractive index of the first and third SiNx Layer (2, 5) is in the range from 2.0 to 2.2 and a refractive index of the second SiNx layer (3) is in the range from 2.2 to 2.4. Monofacial solar cell according to one of the preceding claims, characterized in that a total layer thickness of the layer stack is at least 80 nm, preferably at least 105 nm, more preferably at least 115 nm, even more preferably at least 120 nm. Monofacial solar cell according to one of the preceding claims, characterized in that a thickness of the AlOx layer (1) is in the range from 5 to 20 nm, a thickness of the SiNx arranged on a side of the AlOx layer (1) facing away from the substrate Layer (2, 3) is in the range from 15 to 70 nm and a thickness of the SiOxNy layer (4) is in the range from 20 to 200 nm. Monofacial solar cell according to one of the preceding Claims 3 to 8th , characterized in that a thickness of the first SiNx layer (2) is in the range from 10 to 40 nm, a thickness of the second SiNx layer (3) is in the range from 5 to 30 nm and a thickness of the third SiNx layer (5) is in the range of 5 to 55 nm. Solar module, comprising a plurality of monofacial solar cells according to one of the preceding claims. Manufacturing process for a monofacial solar cell according to one of the Claims 1 to 9 , characterized in that the back layer stack of AlOx layer (1), SiNx layer (s) (2, 3, 5) and SiOxNy layer (4) are deposited in a pipe PECVD system with a graphite boat as a wafer holder and the Layers are applied in succession in one and the same tube.

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