Bifacial solar cell, solar module and method for manufacturing bifacial solar cell

Abstract

The invention relates to a bifacial solar cell having a back-side layer stack, characterized in that the back-side layer stack comprises an AlOx layer (1), one or more SiNx layers (2, 3, 5) and a SiOxNy layer (4). The invention also relates to a solar module having a plurality of such bifacial solar cells. The invention also relates to a method for producing a bifacial solar cell, wherein the back-side layer stack consisting of an AlOx layer (1), a SiNx layer (2, 3, 5) and a SiOxNy layer (4) is deposited in a tubular PECVD system using a graphite boat as a wafer carrier and the layers are applied successively in the same tube.

Description

Technical Field

[0001] The present invention relates to a bifacial solar cell, a solar module and a method for producing a bifacial solar cell. In particular, the present invention relates to a bifacial solar cell with a layer stack on the back side, a solar module with such a bifacial solar cell and a method for producing a bifacial solar cell. Background Art

[0002] A solar cell generally has a front side and a back side, each of which may have a layer stack. It is an electrical structural element which converts sunlight incident on its front side directly into electrical energy.

[0003] In order to avoid light losses due to reflection, solar cells can have an antireflection coating. Such solar cells are described, for example, in DE 10 2009 056 594 A1, which proposes an antireflection coating for the front side of a solar cell with a first SiNx layer having a high refractive index and a second SiNx layer having a lower refractive index.

[0004] Furthermore, DE 10 2006 062 092 B4 discloses a photovoltaic module having solar cells, each of which has a cell layer system arranged between a laminate and a light-receiving surface of the solar cell, which has a varying refractive index and consists of at least three different layers with different refractive indices.

[0005] The solar cell according to the prior art is a single-sided solar cell. A single-sided solar cell can only utilize light incident on its front side. Therefore, its efficiency is limited.

[0006] In addition to single-sided solar cells, bifacial solar cells (also often expressed in English as: double-sided solar cells) are known. Such bifacial solar cells are solar cells that are able to utilize sunlight incident from both sides. Bifacial solar cells can utilize not only direct light incident on the front side, but also direct or indirect light incident on the back side, the latter in the form of reflected sunlight, for example. This results in a higher efficiency of the solar cell than in single-sided solar cells. For example, light reflected from a bright house wall from the back side of a bifacial solar cell can thus be utilized.

[0007] For example, Dürweber et al. describe in 2B0.4.3, pp. 345-350, 31st Conference EUPVSEC 2015, Haberburg Paper Publishers, a bifacial solar cell having a double-layer layer stack, which is applied to a substrate on the back side. The layer stack consists of an AlOx layer arranged on the substrate and a SiNx layer arranged on the side of the AlOx layer facing away from the substrate. However, there is still a need to improve the efficiency of solar cells. Summary of the invention

[0008] The object of the present invention is to provide a solar cell and a solar module with optimized efficiency and a production method for a solar cell.

[0009] The invention relates to a bifacial solar cell with a back-side layer stack, wherein the back-side layer stack comprises an AlOx layer, one or more SiNx layers and one or more SiOxNy layers. The respective SiNx and SiOxNy layers may differ in their refractive index.

[0010] By means of this back-side layer stack, the efficiency of the bifacial solar cell is increased. Compared to bifacial solar cells with a back-side layer stack consisting of an AlOx layer and a SiNx layer, higher efficiencies are achieved both at the front side (+0.2%) and at the back side with light incidence (+0.8 to 1.0%) as well as reduced PID degradation. PID (potential induced degradation = potential induced degradation) is a phenomenon that attacks the solar cells of solar module devices. PID causes the power of the solar module to deteriorate over time.

[0011] Depending on the manufacturing process of the SiNx layer and the SiOxNy layer, for example in the PECVD method (plasma enhanced chemical vapor deposition method), hydrogen is stored (einlagern) when the layer is deposited, that is to say, the SiNx layer or the SiOxNy layer is hydrogenated, which is indicated by the name SiNx:H layer or SiOxNy layer:H layer. The hydrogen contained in this layer passivates the recombination centers at the SiNx / Si interface and the SiOxNy interface and in the volume of the silicon substrate. As a result, the efficiency of the solar cell is affected positively. The manufacture of the back layer stack according to the present invention is possible in a PECVD device in one process without ventilation or equipment replacement. Costs can be saved thereby. Preferably, all layers of the back stack are deposited by direct plasma in a tubular PECVD device with a graphite boat as a wafer carrier. However, AlOx can also be deposited by means of "atomic layer deposition" (ALD) or microwave remote plasma, and SiNx layers and SiOxNy layers can be deposited in a tubular PECVD device.

[0012] The bifacial solar cell is preferably a monocrystalline or multicrystalline solar cell with a silicon substrate. Preferably, the bifacial solar cell is a PERC cell (PERC - Passive Emitter and Rear Cell).

[0013] In a preferred embodiment, an AlOx layer is arranged on the substrate of the solar cell, a SiNx layer is arranged on the side of the AlOx layer facing away from the substrate, and a SiOxNy layer is arranged on the side of the SiNx layer facing away from the substrate. In this embodiment, the bifacial solar cell has the following structure on the back side: substrate / AlOx layer / SiNx layer / SiOxNy layer. Preferably, the layers of the layer stack are arranged directly or indirectly on top of each other, i.e. without further intermediate layers.

[0014] Preferably, the SiNx layer is a SiNx bilayer having a first SiNx layer and a second SiNx layer. The layer stack therefore preferably has four layers. More preferably, the layer stack consists of four layers in the following order: AlOx layer / SiNx bilayer / SiOxNy layer. It should always be noted here that an additional rear metallization may be present on the rear side of the solar cell.

[0015] In another preferred embodiment, the third SiNx layer is arranged on the side of the SiOxNy layer facing away from the substrate. In this embodiment, the layer stack preferably has five layers. More preferably, the layer stack consists of five layers in the following order: AlOx layer / SiNx bilayer / SiOxNy layer / SiNx layer. It should also be noted here that an additional back metallization may be present on the back side of the solar cell.

[0016] Advantageously, the refractive index of the first SiNx layer is less than the refractive index of the second SiNx layer, wherein the first SiNx layer is arranged on the side of the second SiNx layer facing away from the substrate, and the second SiNx layer is arranged on the side of the AlOx layer facing away from the substrate. In this embodiment, the solar cell preferably has the following structure on the back side: 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 less than the refractive index of the second SiNx layer.

[0017] More preferably, the refractive index of the third SiNx layer is equal to or substantially equal to the refractive index of the first SiNx layer.

[0018] Advantageously, the refractive index of the SiOxNy layer is less than the refractive index of the SiNx layer, ie the first, second and third SiNx layers. In particular, the refractive index of the SiOxNy layer may be greater than the refractive index of the AlOx layer.

[0019] In a preferred embodiment, the refractive index of the AlOx layer is in the range of 1.5 to 1.7, the refractive index of the SiNx layer is in the range of 2.0 to 2.4, and the refractive index of the SiOxNy layer is in the range of 1.5 to 1.9 measured according to DIN at a wavelength of 632 nm. When the SiNx layer is a SiNx bilayer, preferably, the refractive index of the first SiNx layer is in the range of 2.0 to 2.2 and the refractive index of the second SiNx layer is in the range of 2.2 to 2.4. When the layer stack comprises a third SiNx layer, preferably, the refractive index of the third SiNx layer is in the range of 2.0 to 2.2. In these value ranges, the bifacial solar cell has a high light coupling-in and achieves a high passivation effect.

[0020] Preferably, the total layer thickness of the layer stack is at least 95 nm, preferably at least 105 nm, more preferably at least 115 nm, even more preferably at least 120 nm. Thus, a higher no-load voltage and a higher efficiency are achieved both when incident light from the front and when incident light from the rear side.

[0021] Preferably, the layer thickness of the SiOxNy layer is greater than the layer thickness of the SiNx layer. When the SiNx layer is a SiNx double layer, preferably, the layer thickness of the SiOxNy layer is equal to or greater than the layer thickness of the SiOx double layer. The layer thickness of the AlOx layer is preferably less than the layer thickness of the SiNx layer. In a preferred embodiment, the layer thickness of the AlOx layer is in the range of 5 to 20 nm, the layer thickness of the SiNx layer arranged on the side of the AlOx layer facing away from the substrate is in the range of 20 to 50 nm, the layer thickness of the third SiNx layer arranged on the side of the SiOxNy layer facing away from the substrate is in the range of 5 to 30 nm, and the layer thickness of the SiOxNy layer is in the range of 40 to 80 nm. The thickness of the first SiNx layer is preferably in the range of 20 to 40 nm, and the thickness of the second SiNx layer is preferably in the range of 10 to 30 nm. The thickness of the third SiNx layer is more preferably in the range of 10 to 20 nm. In these value ranges, the bifacial solar cell has a high light coupling and achieves a high passivation effect.

[0022] In a preferred embodiment, the back layer stack consists of the following four layers: an AlOx layer arranged on the substrate, a second SiNx layer arranged on the side of the AlOx layer facing away from the substrate, a first SiNx layer arranged on the side of the SiNx layer facing away from the substrate, and a 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 of 1.5 to 1.7, more preferably 1.6, the refractive index of the second SiNx layer is preferably in the range of 2.2 to 2.4, the refractive index of the first SiNx layer is in the range of 2.0 to 2.1, and the refractive index of the SiOxNy layer is in the range of 1.5 to 1.7, as measured above.

[0023] In another preferred embodiment, the back layer stack consists of the following five layers: an AlOx layer arranged on the substrate, a second SiNx layer arranged on the side of the AlOx layer facing away from the substrate, a first SiNx layer arranged on the side of the SiNx layer facing away from the substrate, a SiOxNy layer arranged on the side of the first SiNx layer facing away from the substrate, and a 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 of 1.5 to 1.7, more preferably 1.6, the refractive index of the second SiNx layer is preferably in the range of 2.2 to 2.4, the refractive index of the first and third SiNx layers is in the range of 2.0 to 2.1, and the refractive index of the SiOxNy layer is in the range of 1.5 to 1.7, as measured above. As already mentioned above, the term "layer stack consisting of the mentioned layers" means that a back metallization can also be provided on the back layer stack.

[0024] Preferably, the total layer thickness of the layer stack is in the range of 100 to 130 nm, more preferably 125 nm. This results in improved resistance to paste cracking in the manufacture of bifacial solar cells. In addition, more hydrogen is quantitatively provided for chemical passivation of the surface and volume. At the same time, good optical (anti-reflection) properties (bifaciality>70% or efficiency>16%) for light incident from the back are achieved using this layer stack. After the bifacial solar cell is encapsulated in a solar module, the visual impression of the back is extremely uniform compared to a bifacial solar cell with a layer stack of about 75-80 nm thick on the back, the layer stack of the back being composed of an AlOx layer (layer thickness of about 15-20 nm, refractive index of 1.6) and a SiNx layer (layer thickness of about 60 nm, refractive index of 2.05).

[0025] Compared to a solar cell with a two-layer layer stack consisting of an AlOx layer and a SiNx layer, the bifacial solar cell according to the invention with a four-layer layer stack has a higher Voc (open circuit voltage, +3 mV) and a higher η when incident from the front. 正面 (front efficiency, + 0.2%); at incidence from the back, even in the case of bifacial solar cells according to the invention with a layer stack of four layers, a Voc (no-load voltage) gain of up to 5 mV and an η of + 0.8% were measured compared to bifacial solar cells with a layer stack of two layers according to the prior art. 背面 (Rear side efficiency). A further advantage of the layer stack according to the invention is the improved resistance of the bifacial solar cell to PID from the rear side.

[0026] The invention also relates to a solar module having a plurality of bifacial solar cells according to one or more of the above-described embodiments. The efficiency of the solar module is increased. The solar module can be constructed bifacially or unifacially. In the latter case, the bifacial solar cells are therefore arranged in a solar module which is actually used for unifacial current extraction.

[0027] Bifacial solar modules have the property that both the light incident on the front side and the light incident on the back side are used for power generation. In bifacial solar modules, transparent films or glass are used as back side encapsulation elements. Thus, light that would otherwise pass through the module and reflected light from the surroundings on the back side can be utilized. Single-sided solar modules have the property that only the light incident on the front side is used for power generation. In single-sided solar modules, a largely light-impermeable back side encapsulation element with a transmittance of less than 2% is used.

[0028] In a preferred embodiment, the solar module is designed as a single-sided solar module. It is also preferred that the solar module has a white rear encapsulation element. This allows a current Isc (short-circuit current) that is approximately 90 mA higher (approximately 1% relative) and thus typically 2-3 W. 峰值 Higher module power.

[0029] A white backside encapsulation element in the sense of the present invention is a backside encapsulation element that is largely opaque in the wavelength range of 300 to 1200 nm. Therefore, when using a white backside encapsulation element, only a small amount of light is expected to be incident on the bifacial solar cell (<2%). However, after evaluating the so-called encapsulation measurements (cell-to-module encapsulation loss, Cell-To-Module encapsulation loss) on single-sided and bifacial solar cells with different encapsulation element materials (glass-glass, glass-transparent backside encapsulation element, glass-white backside encapsulation element), the inventors found that, in the case of illumination from the front, i.e., in the case of light incident on the front side, an approximately 1% higher Isc current (short-circuit current) per solar cell was measured compared to a single-sided solar cell, which in the case of a solar module with 72 solar cells under standard test conditions resulted in a solar module power of approximately 2 W higher.

[0030] Compared to monofacial solar cells, bifacial solar cells also save on aluminum paste, since only about 10-20% of the surface is metallized. This can save costs.

[0031] Furthermore, it has been found that in bifacial solar cells, a higher Jsc (short-circuit current density) is achieved compared to monofacial solar cells, which can be caused by the back reflection of radiation in the near IR range (700-1200 nm) that meets the white rear encapsulation element. This radiation is then coupled back into the bifacial solar cell and can generate charge carriers.

[0032] The present invention also relates to a method for manufacturing a bifacial solar cell according to one or more of the described embodiments, wherein a back-side layer stack consisting of an AlOx layer, a SiNx layer and a SiOxNy layer is deposited in a tubular PECVD device using a graphite boat as a wafer carrier, and these layers are coated successively in the same tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Other features and advantages of the present invention will be shown in conjunction with the accompanying drawings and described below by way of example. The accompanying drawings show schematically and not to scale:

[0034] FIG1 shows a layer stack according to the prior art;

[0035] Figure 2a A layer stack according to the invention is shown;

[0036] Figure 2b Another layer stack according to the invention is shown;

[0037] Figures 3a to 3e Shown in Figure 2aA variant of the layer stack according to the invention shown in;

[0038] Figure 3f Shown in Figure 2b The variant of the layer stack according to the invention shown in FIG.

[0039] Figure 4 and Figure 5 Graphs with a comparison of two bifacial solar cells are shown for Jsc, Voc, FF and Eta respectively. DETAILED DESCRIPTION

[0040] FIG. 1 shows a layer stack according to the prior art. This known layer stack is applied to a substrate (not shown) in a double layer and on the back side. The layer stack consists of an AlOx layer 1 arranged on a substrate (not shown) and a first SiNx layer 2 arranged on the side of the AlOx layer 1 facing away from the substrate. The AlOx layer 1 has a refractive index of 1.6 as measured above, and a layer thickness of 16 nm. The first SiNx layer 2 has a refractive index of 2.05 as measured above and a layer thickness of 60 nm. The total layer thickness of the layer stack is therefore 76 nm.

[0041] Figure 2a A layer stack according to the invention is shown. The layer stack according to the invention is applied to a substrate (not shown) in the form of four layers and on the back side. The layer stack has an AlOx layer 1 arranged on a substrate (not shown), a SiNx bilayer 2, 3 arranged on the side of the AlOx layer 1 facing away from the substrate, and a SiOxNy layer 4 arranged on the side of the SiNx bilayer facing away from the substrate. The SiNx bilayer 2, 3 has a first SiNx layer 2 and a second SiNx layer 3, wherein the first SiNx layer 2 is arranged on the side of the second SiNx layer 3 facing away from the substrate, and the second SiNx layer 3 is arranged on the side of the AlOx layer 1 facing away from the substrate.

[0042] The AlOx layer 1 has a refractive index of 1.6 as measured above and a layer thickness of 5 to 20 nm. The first SiNx layer 2 has a refractive index in the range of 2.0 to 2.2 as measured above, and has a layer thickness in the range of 20 to 40 nm. The second SiNx layer 3 has a refractive index in the range of 2.1 to 2.4 as measured above, and has a layer thickness in the range of 10 to 30 nm. The SiOxNy layer 4 has a refractive index in the range of 1.5 to 1.9 as measured above, and a layer thickness in the range of 50 to 80 nm. Therefore, the total layer thickness of the layer stack is 89 to 170 nm, preferably 110 to 140 nm.

[0043] Figure 2b Another layer stack according to the invention is shown. Figure 2b The layer stack shown in corresponds to the Figure 2a , with the difference that a third SiNx layer 5 is also arranged on the side of the SiOxNy layer 4 facing away from the substrate. The third SiNx layer 5 has a refractive index in the range of 2.0 to 2.2 as measured above and a layer thickness in the range of 10 to 20 nm.

[0044] Figures 3a to 3e Shown in Figure 2a A variant of the layer stack according to the invention is shown in FIG.

[0045] Figure 3a Shown according to Figure 2a , wherein the AlOx layer 1 has a layer thickness of 16 nm and a refractive index of 1.6, the second SiNx layer 3 has a layer thickness of 40 nm and a refractive index of 2.40, the first SiNx layer 2 has a layer thickness of 20 nm and a refractive index of 2.05, and the SiOxNy layer 4 has a layer thickness of 60 nm and a refractive index of 1.7. The total layer thickness of the layer stack is 136 nm.

[0046] Figure 3b Shown according to Figure 2a , wherein the AlOx layer 1 has a layer thickness of 16 nm and a refractive index of 1.6, the second SiNx layer 3 has a layer thickness of 20 nm and a refractive index of 2.40, the first SiNx layer 2 has a layer thickness of 20 nm and a refractive index of 2.05, and the SiOxNy layer 4 has a layer thickness of 70 nm and a refractive index of 1.7. The total layer thickness of the layer stack is 126 nm.

[0047] Figure 3c Shown according to Figure 2a , wherein the AlOx layer 1 has a layer thickness of 16 nm and a refractive index of 1.6, the second SiNx layer 3 has a layer thickness of 20 nm and a refractive index of 2.10, the first SiNx layer 2 has a layer thickness of 30 nm and a refractive index of 2.05, and the SiOxNy layer 4 has a layer thickness of 50 nm and a refractive index of 1.7. The total layer thickness of the layer stack is 116 nm.

[0048] Figure 3d Shown according to Figure 2a , wherein the AlOx layer 1 has a layer thickness of 16 nm and a refractive index of 1.6, the second SiNx layer 3 has a layer thickness of 20 nm and a refractive index of 2.20, the first SiNx layer 2 has a layer thickness of 30 nm and a refractive index of 2.05, and the SiOxNy layer 4 has a layer thickness of 50 nm and a refractive index of 1.7. The total layer thickness of the layer stack is 116 nm.

[0049] Figure 3e Shown according to Figure 2a , wherein the AlOx layer 1 has a layer thickness of 10 nm and a refractive index of 1.6, the second SiNx layer 3 has a layer thickness of 20 nm and a refractive index of 2.20, the first SiNx layer 2 has a layer thickness of 30 nm and a refractive index of 2.05, and the SiOxNy layer 4 has a layer thickness of 80 nm and a refractive index of 1.7. The total layer thickness of the layer stack is 140 nm.

[0050] Figure 3f Shown in Figure 2b , a variant of the layer stack according to the invention is shown in which the AlOx layer 1 has a layer thickness of 16 nm and a refractive index of 1.6, the first SiNx layer 2 has a layer thickness of 20 nm and a refractive index of 2.05, the second SiNx layer 3 has a layer thickness of 20 nm and a refractive index of 2.4, the SiOxNy layer 4 has a layer thickness of 70 nm and a refractive index of 1.5, and the third SiNx layer 5 has a layer thickness of 10 nm and a refractive index of 2.05.

[0051] Figure 4 and 5 The following graphs are shown in which the short-circuit current density (Jsc), the no-load voltage (Voc), the fill factor (FF) and the efficiency (Eta) of two bifacial solar cells according to the invention are compared. These graphs are so-called box diagrams with the median (the numbers around it are also plotted) and the upper and lower quartiles. They are the result of a group experiment with typically hundreds of bifacial solar cells.

[0052] Figure 4 A block diagram showing a comparison of two bifacial solar cells with short circuit current density (Jsc), no-load voltage (Voc), fill factor (FF) and efficiency (Eta) under frontal illumination of the bifacial solar cell is shown. B1 represents the bifacial solar cell according to the present invention shown in FIG3B , and C1 represents the bifacial solar cell according to the prior art shown in FIG1 . Figure 4 As shown, compared with the bifacial solar cell according to the prior art, the bifacial solar cell according to the present invention has a higher short-circuit current density, a no-load voltage that is about 3 mV higher, a higher fill factor, and an efficiency that is about 0.2% higher.

[0053] Figure 5A diagram is shown which shows a comparison of two bifacial solar cells for short circuit current density (Jsc), no-load voltage (Voc), fill factor (FF) and efficiency (Eta) when the back side of the bifacial solar cell is illuminated. B1 represents the bifacial solar cell according to the present invention shown in FIG3B , and C1 represents the bifacial solar cell according to the prior art shown in FIG1 . Figure 5 As shown, compared with the bifacial solar cell according to the prior art, the bifacial solar cell according to the present invention has a higher power consumption of about 1.2 mA / cm 2 The results are as follows: higher short-circuit current density, 5 mV higher no-load voltage, higher fill factor and 0.75% higher efficiency.

[0054] Reference numerals list

[0055] 1 AlOx layer

[0056] 2. First SiNx layer

[0057] 3 Second SiNx layer

[0058] 4 SiOxNy layer

[0059] 5 The third SiNx layer.

Claims

1. A bifacial solar cell having a layer stack on the back side, wherein: The back-side layer stack comprises an AlOx layer (1), one or more SiNx layers (2, 3, 5) and a SiOxNy layer (4), The refractive index of the AlOx layer (1) is in the range of 1.5 to 1.7, the refractive index of the SiNx layer (2, 3, 5) is in the range of 2.0 to 2.4, and the refractive index of the SiOxNy layer (4) is in the range of 1.5 to 1.9 measured at a wavelength of 632 nm according to DIN. wherein the thickness of the AlOx layer (1) is in the range of 5 to 20 nm, the thickness of the SiNx layers (2, 3) arranged on the side of the AlOx layer (1) facing away from the substrate is in the range of 20 to 50 nm, the thickness of the third SiNx layer (5) arranged on the side of the SiOxNy layer (4) facing away from the substrate is in the range of 5 to 30 nm, and the thickness of the SiOxNy layer (4) is in the range of 40 to 80 nm, The AlOx layer (1) is arranged on a substrate of the solar cell, the SiNx layers (2, 3) are 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.

2. The double-sided solar cell according to claim 1, characterized in that: The SiNx layer (2, 3) is a SiNx double layer having a first SiNx layer (2) and a second SiNx layer (3).

3. The double-sided solar cell according to claim 1, characterized in that: The third SiNx layer (5) is arranged on the side of the SiOxNy layer (4) facing away from the substrate.

4. The double-sided solar cell according to claim 2, characterized in that: The refractive index of the first SiNx layer (2) is smaller than the refractive index of the second SiNx layer (3), wherein the first SiNx layer (2) is arranged on a side of the second SiNx layer (3) facing away from the substrate, and the second SiNx layer (3) is arranged on a side of the AlOx layer (1) facing away from the substrate.

5. The double-sided solar cell according to claim 2, characterized in that: The refractive index of the first SiNx layer (2) and the third SiNx layer (5) is in the range of 2.0 to 2.2, and the refractive index of the second SiNx layer (3) is in the range of 2.2 to 2.

4.

6. The bifacial solar cell according to claim 1, characterized in that: The total layer thickness of the layer stack is at least 95 nm, at least 105 nm, at least 115 nm or at least 120 nm.

7. The bifacial solar cell according to any one of claims 4 to 5, characterized in that: The thickness of the first SiNx layer (2) is in the range of 20 to 40 nm, the thickness of the second SiNx layer (3) is in the range of 10 to 30 nm, and the thickness of the third SiNx layer (5) is in the range of 10 to 20 nm.

8. A solar module comprising a plurality of bifacial solar cells according to any one of claims 1 to 7. 9 . The solar module according to claim 8 , which is designed as a single-sided solar module.

10. The solar module according to claim 9, characterized in that White backside package components.

11. A method for manufacturing a bifacial solar cell according to any one of claims 1 to 7, characterized in that: The back-side layer stack consisting of an AlOx layer (1), a SiNx layer (2, 3, 5) and a SiOxNy layer (4) is deposited in a tubular PECVD system using a graphite boat as a wafer carrier and these layers are applied successively in the same tube.

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