阅读说明：本技术 双面太阳能电池、太阳能模块及双面太阳能电池的制造方法 (Bifacial solar cell, solar module, and method for manufacturing bifacial solar cell ) 是由 A·施瓦贝迪森 J·切斯拉克 V·默滕斯 M·容塔内尔 于 2019-03-27 设计创作，主要内容包括：本发明涉及一种双面太阳能电池,其具有背面的层堆叠,其特征在于,所述背面的层堆叠具有AlOx层(1)、一个或多个SiNx层(2、3、5)和SiOxNy层(4)。此外,本发明涉及一种太阳能模块,其具有多个这样的双面太阳能电池。此外,本发明涉及一种用于双面太阳能电池的制造方法,其中,在将石墨舟作为晶片载体的管式PECVD设备中沉积由AlOx层(1)、SiNx层(2、3、5)和SiOxNy层(4)组成的背面的层堆叠,并将这些层相继涂覆在同一个管中。(The invention relates to a bifacial solar cell having a rear-side layer stack, characterized in that the rear-side layer stack has an AlOx layer (1), one or more SiNx layers (2, 3, 5) and an SiOxNy layer (4). The invention further relates to a solar module having a plurality of such bifacial solar cells. The invention further relates to a method for producing a bifacial solar cell, wherein a rear layer stack of an AlOx layer (1), a SiNx layer (2, 3, 5) and a SiOxNy layer (4) is deposited in a tubular PECVD apparatus using a graphite boat as a wafer carrier, and the layers are applied one after the other in the same tube.)

1. A bifacial solar cell having a backside layer stack, characterized in that the backside layer stack comprises an AlOx layer (1), one or more SiNx layers (2, 3, 5) and a SiOxNy layer (4).

2. Bifacial solar cell according to 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 the side of the AlOx layer (1) facing away from the substrate, and the SiOxNy layer (4) is arranged on the side of the SiNx layer (2, 3) facing away from the substrate.

3. The bifacial solar cell of claim 1 or 2, wherein said SiNx layer (2, 3) is a SiNx bilayer having a first SiNx layer (2) and a second SiNx layer (3).

4. Bifacial solar cell according to claim 2 or 3, characterized in that a third SiNx layer (5) is arranged on the side of the SiOxNy layer (4) facing away from the substrate.

5. The bifacial solar cell according to claim 3 or 4, characterized in that the refractive index of said first SiNx layer (2) is lower than the refractive index of said second SiNx layer (3), wherein said first SiNx layer (2) is arranged on the side of said second SiNx layer (3) facing away from said substrate and said second SiNx layer (3) is arranged on the side of said AlOx layer (1) facing away from said substrate.

6. The bifacial solar cell of any one of the preceding claims, wherein 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, the refractive index of the SiOxNy layer (4) is in the range of 1.5 to 1.9 measured according to DIN at a wavelength of 632nm, wherein preferably the refractive indices of the first and third SiNx layers (2, 5) are 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.

7. The bifacial solar cell of any one of the preceding claims, wherein the total layer thickness of the layer stack is at least 95nm, preferably at least 105nm, more preferably at least 115nm, still more preferably at least 120 nm.

8. The bifacial solar cell according to any of the preceding claims, characterized in that the thickness of the AlOx layer (1) is in the range of 5 to 20nm, the thickness of the SiNx layer (2, 3) arranged on the side of the AlOx layer (1) facing away from the substrate is in the range of 20 to 50nm, 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 30nm, and the thickness of the SiOxNy layer (4) is in the range of 40 to 80nm, wherein preferably the thickness of the first SiNx layer (2) is in the range of 20 to 40nm, the thickness of the second SiNx layer (3) is in the range of 10 to 30nm, and the thickness of the third SiNx layer (5) is in the range of 10 to 20 nm.

9. A solar module comprising a plurality of bifacial solar cells according to any of the preceding claims.

10. The solar module of claim 9 configured as a single-sided solar module.

11. The solar module of claim 10, characterized by a white back side encapsulant element.

12. A method for producing a bifacial solar cell as claimed in one of claims 1 to 8, characterized in that the layer stack of the rear side consisting of AlOx layer (1), SiNx layer (2, 3, 5) and SiOxNy layer (4) is deposited in a tubular PECVD apparatus using a graphite boat as wafer carrier and these layers are applied one after the other in the same tube.

Technical Field

The invention relates to a bifacial solar cell, a solar module and a method for manufacturing a bifacial solar cell. The invention relates in particular to a bifacial solar cell with a layer stack on the rear side and to a solar module with such a bifacial solar cell and to a method for producing a bifacial solar cell.

Background

Solar cells generally have a front side and a rear side, which may each have a layer stack. It is an electrical structural element that directly converts sunlight incident on its front face into electrical energy.

To avoid light losses due to reflection, the solar cell may have an anti-reflection coating. Such a solar cell is described, for example, in DE102009056594a1, which proposes an anti-reflection 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.

Furthermore, a photovoltaic module having solar cells each having a cell layer system arranged between the laminate and the light-receiving surface of the solar cell is known from DE102006062092B4, the cell layer system having a varying refractive index and consisting of at least three different layers having different refractive indices.

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

In addition to single-sided solar cells, bifacial solar cells (also commonly expressed in english as: bifacial solar cells) are known. Such a bifacial solar cell is a solar cell capable of utilizing sunlight incident from both sides. Bifacial solar cells can utilize not only direct light incidence on the front side, but also direct or indirect light incidence on the back side, the latter for example in the form of reflected sunlight. This achieves a higher efficiency of the solar cell than in a single-sided solar cell. For example, light from the back of a bifacial solar cell reflected by a bright house wall can thus be utilized.

For example, dualburber et al describes in conference EUPVSEC 2015, Haberburg Paper press 2B0.4.3, page 345-350, at conference 31, a bifacial solar cell with a bilayer layer stack that is back-coated onto a substrate. 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.

Disclosure of Invention

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

According to the invention, this object is achieved by a bifacial solar cell having the features of claim 1, a solar module having the features of claim 8 and a production method for a bifacial solar cell having the features of claim 11. Advantageous developments and modifications are given in the dependent claims.

The invention relates to a bifacial solar cell having a back-side layer stack, wherein the back-side layer stack has 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.

By such a layer stack on the rear side, the efficiency of the bifacial solar cell is increased. Compared to a bifacial solar cell with a layer stack having a back side consisting of an AlOx layer and a SiNx layer, there is a higher efficiency and reduced PID degradation at both front side (+ 0.2%) and back side light incidence (+0.8 to 1.0%). PID (potential induced degradation) is a phenomenon that attacks the solar cells of a solar module device. PID causes the power of the solar module to deteriorate over time.

Depending on the production process of the SiNx and SiOxNy layers, for example in the PECVD process (plasma enhanced chemical vapor deposition process), hydrogen is stored (einlagern) when the layers are deposited, that is to say the SiNx or SiOxNy layer is hydrogenated, which is done by the name SiNx: h layer or SiOxNy layer: and H layer. The hydrogen contained in such a layer passivates recombination centers at the SiNx/Si interface and SiOxNy interface and in the volume of the silicon substrate. Thereby, the efficiency of the solar cell is positively influenced. The production of the rear layer stack according to the invention is possible in a PECVD apparatus in one process without ventilation or apparatus exchange. Thereby saving costs. Preferably, all layers of the back side stack are deposited by means of direct plasma in a tubular PECVD apparatus with a graphite boat as wafer carrier. However, it is also possible to deposit AlOx by means of "atomic layer deposition" (ALD) or microwave remote plasma and to deposit SiNx and SiOxNy layers in a tubular PECVD apparatus.

The bifacial solar cell is preferably a monocrystalline or polycrystalline solar cell having a silicon substrate. Preferably, the bifacial solar cell is a PERC cell (PERC-passive emitter and rear unit).

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 arranged on a 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 one another, i.e. without further intermediate layers.

Preferably, the SiNx layer is a SiNx bi-layer having a first SiNx layer and a second SiNx layer. Therefore, the layer stack preferably has four layers. More preferably, the layer stack consists of four layers in the following order: AlOx layer/SiNx bilayer/SiOxNy layer. It is always to be noted here that an additional back-side metallization can be present on the back side of the solar cell.

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 is also to be noted here that an additional back-side metallization may be present on the back side of the solar cell.

Advantageously, the refractive index of the first SiNx layer is lower than the refractive index of the second SiNx layer, wherein the first SiNx layer is arranged on a side of the second SiNx layer facing away from the substrate and the second SiNx layer is arranged on a 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: the structure comprises a substrate, an AlOx layer, a second SiNx layer, a first SiNx layer and an SiOxNy layer, or the substrate, the AlOx layer, the second SiNx layer, the first SiNx layer, the SiOxNy layer and a third SiNx layer. The refractive index of the third SiNx layer is preferably smaller than that of the second SiNx layer.

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

Advantageously, the refractive index of the SiOxNy layer is less than the refractive index of the SiNx layer, i.e., 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.

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 double layer, it is preferable that a refractive index of the first SiNx layer is in a range of 2.0 to 2.2, and a refractive index of the second SiNx layer is in a range of 2.2 to 2.4. When the layer stack includes the third SiNx layer, it is preferable that the refractive index of the third SiNx layer is in a range of 2.0 to 2.2. Within these value ranges, bifacial solar cells have high light incoupling and achieve a high passivation effect.

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

Preferably, the layer thickness of the SiOxNy layer is larger than the layer thickness of the SiNx layer. When the SiNx layer is a SiNx double layer, it is preferable that 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 smaller than that of the SiNx layer. In a preferred embodiment, the layer thickness of the AlOx layer lies in the range from 5 to 20nm, the layer thickness of the SiNx layer arranged on the side of the AlOx layer facing away from the substrate lies in the range from 20 to 50nm, the layer thickness of the third SiNx layer arranged on the side of the SiOxNy layer facing away from the substrate lies in the range from 5 to 30nm, and the layer thickness of the SiOxNy layer lies in the range from 40 to 80 nm. The thickness of the first SiNx layer is preferably in the range of 20 to 40nm, 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. Within these value ranges, bifacial solar cells have high light incoupling and achieve a high passivation effect.

In a preferred embodiment, the layer stack of the rear side consists of the following four layers: the semiconductor device comprises an AlOx layer arranged on a substrate, a second SiNx layer arranged on the side, facing away from the substrate, of the AlOx layer, a first SiNx layer arranged on the side, facing away from the substrate, of the SiNx layer, and a SiOxNy layer arranged on the side, facing away from the substrate, of the first SiNx layer. 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.

In a further preferred embodiment, the layer stack on the rear side consists of the following five layers: the SiOxNy layer comprises an AlOx layer arranged on the substrate, a second SiNx layer arranged on the side, away from the substrate, of the AlOx layer, a first SiNx layer arranged on the side, away from the substrate, of the SiNx layer, an SiOxNy layer arranged on the side, away from the substrate, of the first SiNx layer, and a third SiNx layer arranged on the side, away from the substrate, of the SiOxNy layer. 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 indices of the first and third SiNx layers are 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 "the layer stack is composed of the mentioned layers" means that, in addition, a rear-side metallization can be provided on the rear-side layer stack.

Preferably, the total layer thickness of the layer stack is in the range of 100 to 130nm, more preferably 125 nm. This results in improved paste crack resistance in the manufacture of bifacial solar cells. In addition, more hydrogen is quantitatively provided for chemical passivation of surfaces and volumes. At the same time, good optical (anti-reflection) properties for light incidence from the back side (double-sided > 70% or efficiency > 16%) are achieved with this layer stack. After encapsulation of the bifacial solar cell in a solar module, the visual impression of the back side is extremely homogeneous compared to a bifacial solar cell with a layer stack of the back side of about 75-80nm thickness, which consists of an AlOx layer (layer thickness of about 15-20nm, refractive index of 1.6) and a SiNx layer (layer thickness of about 60nm, refractive index of 2.05).

The bifacial solar cell according to the invention having a four-layer stack has a higher Voc (open voltage, +3mV) and a higher η at incidence from the front side, in comparison to a solar cell having a two-layer stack consisting of an AlOx layer and a SiNx layer_{Front side}(positive efficiency, + 0.2%); at incidence from the back side, a Voc (open circuit voltage) gain of up to 5mV and an η of + 0.8% were measured even in the bifacial solar cell according to the invention with a layer stack of four layers, compared to the bifacial solar cell with a layer stack of two layers according to the prior art_{Back side of the panel}(backside efficiency). Another advantage of the layer stack according to the invention is the improved tolerance of the bifacial solar cell with respect to PID from the backside.

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 improved. The solar module can be constructed double-sided or single-sided. In the latter case, bifacial solar cells are therefore arranged in solar modules which are actually used for single-sided current acquisition.

The double-sided solar module has a characteristic that not only light incident on the front surface but also light incident on the rear surface is used for power generation. In a double-sided solar module, a transparent film or glass is used as the back-side encapsulation element. Thus, light that passes through the module unutilized and reflected light from the surroundings on the rear side can be utilized. The single-sided solar module has a characteristic in that only light incident on the front surface is used for power generation. In single-sided solar modules, largely light-tight back-side encapsulation elements with a transmission of less than 2% are used.

In a preferred embodiment, the solar module is designed as a single-sided solar module. Furthermore, the solar module preferably has a white rear-side encapsulation element. It is thus possible to achieve currents Isc (short-circuit current) which are higher by about 90mA (about 1% relative), and thus are typically 2-3W_{Peak value}Higher module power.

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

Aluminum paste is also saved in bifacial solar cells compared to single-sided solar cells, since only about 10-20% of the sides are metallized. Thereby saving costs.

Furthermore, it has been found that in a bifacial solar cell, a higher Jsc (short circuit current density) is obtained compared to a single-sided solar cell, which may be caused by back reflections of radiation in the near IR range (700-. This radiation is then coupled into the bifacial solar cell again and can generate charge carriers.

The invention also relates to a method for producing a bifacial solar cell according to one or more of the exemplary embodiments, wherein a layer stack of the rear side, consisting of an AlOx layer, a SiNx layer and a SiOxNy layer, is deposited in a tubular PECVD apparatus using a graphite boat as wafer carrier and these layers are applied one after the other in the same tube.

Drawings

Other features and advantages of the present invention will be shown in the drawings and described below by way of example. The figures show schematically and not to scale:

fig. 1 shows a layer stack according to the prior art;

fig. 2a shows a layer stack according to the invention;

fig. 2b shows another layer stack according to the invention;

fig. 3a to 3e show variants of the layer stack according to the invention shown in fig. 2 a;

fig. 3f shows a variant of the layer stack according to the invention shown in fig. 2 b; and

fig. 4 and 5 show graphs comparing with two bifacial solar cells for Jsc, Voc, FF and Eta, respectively.

Detailed Description

Fig. 1 shows a layer stack according to the prior art. This known layer stack is applied bilaterally and on the rear side to a substrate (not shown). 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 measured as above and a layer thickness of 60 nm. The total layer thickness of the layer stack is thus 76 nm.

Fig. 2a shows a layer stack according to the invention. The layer stack according to the invention is applied to a substrate (not shown) in the form of four layers and on the rear 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.

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. The total layer thickness of the layer stack is therefore 89 to 170nm, preferably 110 to 140 nm.

Fig. 2b shows another layer stack according to the invention. The layer stack shown in fig. 2b corresponds to the layer stack shown in fig. 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 has a layer thickness in the range of 10 to 20 nm.

Fig. 3a to 3e show variants of the layer stack according to the invention shown in fig. 2 a.

Fig. 3a shows a layer stack of the rear side according to fig. 2a, in which AlOx layer 1 has a layer thickness of 16nm and a refractive index of 1.6, the second SiNx layer 3 has a layer thickness of 40nm and a refractive index of 2.40, the first SiNx layer 2 has a layer thickness of 20nm and a refractive index of 2.05, and the SiOxNy layer 4 has a layer thickness of 60nm and a refractive index of 1.7. The total layer thickness of the layer stack was 136 nm.

Fig. 3b shows a layer stack of the rear side according to fig. 2a, in which AlOx layer 1 has a layer thickness of 16nm and a refractive index of 1.6, the second SiNx layer 3 has a layer thickness of 20nm and a refractive index of 2.40, the first SiNx layer 2 has a layer thickness of 20nm and a refractive index of 2.05, and the SiOxNy layer 4 has a layer thickness of 70nm and a refractive index of 1.7. The total layer thickness of the layer stack was 126 nm.

Fig. 3c shows a layer stack of the rear side according to fig. 2a, in which AlOx layer 1 has a layer thickness of 16nm and a refractive index of 1.6, the second SiNx layer 3 has a layer thickness of 20nm and a refractive index of 2.10, the first SiNx layer 2 has a layer thickness of 30nm and a refractive index of 2.05, and the SiOxNy layer 4 has a layer thickness of 50nm and a refractive index of 1.7. The total layer thickness of the layer stack is 116 nm.

Fig. 3d shows a layer stack of the rear side according to fig. 2a, in which AlOx layer 1 has a layer thickness of 16nm and a refractive index of 1.6, the second SiNx layer 3 has a layer thickness of 20nm and a refractive index of 2.20, the first SiNx layer 2 has a layer thickness of 30nm and a refractive index of 2.05, and the SiOxNy layer 4 has a layer thickness of 50nm and a refractive index of 1.7. The total layer thickness of the layer stack is 116 nm.

Fig. 3e shows a layer stack of the rear side according to fig. 2a, in which AlOx layer 1 has a layer thickness of 10nm and a refractive index of 1.6, the second SiNx layer 3 has a layer thickness of 20nm and a refractive index of 2.20, the first SiNx layer 2 has a layer thickness of 30nm and a refractive index of 2.05, and the SiOxNy layer 4 has a layer thickness of 80nm and a refractive index of 1.7. The total layer thickness of the layer stack was 140 nm.

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

Fig. 4 and 5 show graphs in which a comparison of 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 is made, respectively. These graphs are so-called block diagrams with a median (also depicted as a number around it) and upper and lower quartiles. Which is the result of a group experiment with typically hundreds of bifacial solar cells.

Fig. 4 shows a block diagram for a comparison of two bifacial solar cells with short-circuit current density (Jsc), open-circuit voltage (Voc), Fill Factor (FF) and efficiency (Eta) for the case of front side illumination of the bifacial solar cells. B1 denotes the bifacial solar cell according to the present invention shown in fig. 3B, and C1 denotes the bifacial solar cell according to the related art shown in fig. 1. As shown in fig. 4, the bifacial solar cell according to the present invention has a higher short current density, a higher no-load voltage by about 3mV, a higher fill factor, and an efficiency by about 0.2% as compared to the bifacial solar cell according to the prior art.

Fig. 5 shows a block diagram with a comparison of two bifacial solar cells for short-circuit current density (Jsc), open-circuit voltage (Voc), Fill Factor (FF) and efficiency (Eta) upon backside illumination of bifacial solar cells. B1 denotes the bifacial solar cell according to the present invention shown in fig. 3B, and C1 denotes the bifacial solar cell according to the related art shown in fig. 1. As shown in FIG. 5, the bifacial solar cell according to the present invention has a height of about 1.2mA/cm higher than that of the bifacial solar cell according to the prior art²Short circuit current density of 5mV higher, no-load voltage of 5mV higher, higher fill factor and efficiency of 0.75% higher.

List of reference numerals

1 AlOx layer

2 first SiNx layer

3 second SiNx layer

4 SiOxNy layer

5 a third SiNx layer.