A solar cell and a method for preparing a solar cell

Abstract

The present invention discloses a solar cell and a method for preparing the solar cell. The solar cell comprises: a silicon substrate, a passivation contact structure and a metal electrode; wherein the passivation contact structure is arranged on the back of the silicon substrate; the metal electrode is in ohmic contact with the passivation contact structure; wherein the metal electrode is a cuboid structure, and the aspect ratio of the cuboid structure is less than 0.05. The solar cell effectively reduces the difficulty of process manufacturing and the cost of solar cell components, and at the same time, further improves the efficiency of the solar cell.

Description

Technical Field

[0001] The invention relates to a solar cell and a method for preparing the solar cell. Background Art

[0002] Solar cells are devices that directly convert light energy into electrical energy through the photoelectric effect or photochemical effect. The main factors affecting the working efficiency of solar cells are: open circuit voltage, short circuit current and fill factor.

[0003] In the prior art, for bifacial solar cells with metal gate electrodes on the back, in order to prevent the back metal electrode from blocking the incident light from the back, the gate width of the metal electrode is often narrowed to ensure the absorption area of ​​the incident light from the back, thereby increasing the short-circuit current.

[0004] Although the gate line structure of the metal electrode in the existing method increases the short-circuit current, the narrower gate line also reduces the contact area between the metal electrode and the silicon wafer, resulting in increased contact resistance and reduced fill factor, thus having limited effect on improving the efficiency of the solar cell. Summary of the invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a solar cell and a method for preparing the solar cell, wherein the metal electrode of the solar cell is a wide and flat (aspect ratio is less than 0.05) rectangular parallelepiped structure, which reduces the difficulty of process manufacturing and the cost of solar cell modules. At the same time, the wider metal electrode can reflect sunlight that is incident from the front and passes through the silicon substrate, so that the silicon substrate reabsorbs the reflected light of the metal electrode, further improving the efficiency of the solar cell.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] In a first aspect, the present invention provides a solar cell, comprising: a silicon substrate, a passivation contact structure and a metal electrode; wherein:

[0008] The passivation contact structure is arranged on the back side of the silicon substrate;

[0009] The metal electrode is in ohmic contact with the passivation contact structure; wherein the metal electrode is a rectangular parallelepiped structure, and the aspect ratio of the rectangular parallelepiped structure is less than 0.05.

[0010] Furthermore, the width of the cuboid-like structure ranges from 65 to 200 μm;

[0011] and / or,

[0012] The height range is 3 to 8 μm.

[0013] Furthermore, the width of the metal electrode located on the front side of the silicon substrate is smaller than the width of the metal electrode located on the back side of the silicon substrate.

[0014] Furthermore, the passivation contact structure further includes: a first passivation layer disposed on the back side of the silicon substrate and a silicon thin film layer containing doping elements, wherein the first passivation layer is located between the silicon substrate and the silicon thin film layer, and the doping element is boron or phosphorus.

[0015] Furthermore, the first passivation layer is a single-layer film composed of a single non-metallic oxide, a stacked film composed of multiple non-metallic oxides, or a stacked film composed of at least one metal oxide and at least one non-metallic oxide; wherein the non-metallic oxide is silicon oxide, silicon nitride, silicon oxynitride, and the metal oxide is aluminum oxide, titanium oxide; the thickness of the first passivation layer is 0.5nm to 2.5nm.

[0016] Furthermore, the silicon thin film layer is a single layer film composed of any one of microcrystalline silicon, amorphous silicon, polycrystalline silicon, silicon oxide and silicon carbide, or a stacked layer film composed of any of the above, and the thickness of the silicon thin film layer is 5nm to 200nm.

[0017] Furthermore, the doping concentration of the doping element is 1.0E 19 atoms / cm 3 ~2.0E 21 atoms / cm 3 ,

[0018] The doping depth is less than or equal to the thickness of the silicon thin film layer.

[0019] Furthermore, a second passivation layer is provided on a side of the passivation contact structure away from the back side of the silicon substrate.

[0020] Furthermore, the second passivation layer is a single-layer film composed of a single non-metallic oxide, a stacked film composed of multiple non-metallic oxides, or a stacked film composed of at least one metal oxide and at least one non-metallic oxide; wherein the non-metallic oxide is silicon oxide, silicon nitride, silicon oxynitride, and the metal oxide is aluminum oxide, titanium oxide; the thickness of the second passivation layer is 30 to 300 nm.

[0021] In a second aspect, an embodiment of the present invention provides a method for preparing a solar cell, comprising:

[0022] forming a passivation contact structure on the back side of the silicon substrate;

[0023] The metal electrode is prepared by screen printing so that the metal electrode and the passivation contact structure achieve ohmic contact; wherein the metal electrode is a rectangular parallelepiped structure, and the aspect ratio of the rectangular parallelepiped structure is less than 0.05.

[0024] Furthermore, the width of the cuboid-like structure ranges from 65 to 200 μm;

[0025] and / or,

[0026] The height range is 3 to 8 μm.

[0027] Furthermore, a metal electrode is prepared on the front side of the silicon substrate, so that the width of the metal electrode located on the front side of the silicon substrate is smaller than the width of the metal electrode located on the back side of the silicon substrate.

[0028] Further, the passivation contact structure comprises: a first passivation layer disposed on the back side of the silicon substrate and a silicon thin film layer containing doping elements;

[0029] A passivation contact structure is formed on the back side of the silicon substrate, including:

[0030] forming a first passivation layer on the back side of the silicon substrate;

[0031] depositing a silicon thin film layer on the first passivation layer;

[0032] The silicon thin film layer is doped with a doping element, and the doped silicon thin film layer is annealed; wherein the doping element is boron or phosphorus.

[0033] Furthermore, the first passivation layer is a single-layer film composed of a single non-metallic oxide, a stacked film composed of multiple non-metallic oxides, or a stacked film composed of at least one metal oxide and at least one non-metallic oxide; wherein the non-metallic oxide is silicon oxide, silicon nitride, silicon oxynitride, and the metal oxide is aluminum oxide, titanium oxide, and the thickness of the first passivation layer is 0.5nm to 2.5nm.

[0034] Furthermore, the silicon thin film layer is a single layer film composed of any one of microcrystalline silicon, amorphous silicon, polycrystalline silicon, silicon oxide and silicon carbide, or a stacked layer film composed of any of the above, and the thickness of the silicon thin film layer is 5nm to 200nm.

[0035] Furthermore, the doping concentration of the doping element is 1.0E 19 atoms / cm 3 ~2.0E 21 atoms / cm 3 ,

[0036] The doping depth is less than or equal to the thickness of the silicon thin film layer.

[0037] Furthermore, a second passivation layer is formed on a side of the passivation contact structure away from the silicon substrate.

[0038] Furthermore, the second passivation layer is a single-layer film composed of a single non-metallic oxide, a stacked film composed of multiple non-metallic oxides, or a stacked film composed of at least one metal oxide and at least one non-metallic oxide; wherein the non-metallic oxide is silicon oxide, silicon nitride, silicon oxynitride, and the metal oxide is aluminum oxide, titanium oxide; the thickness of the second passivation layer is 30 to 300 nm.

[0039] The technical solution of the first aspect of the above invention has the following advantages or beneficial effects: In the solution provided by the embodiment of the present invention, since the metal electrode arranged on the back of the silicon substrate is a quasi-rectangular structure with an aspect ratio of less than 0.05, the wider metal electrode increases the contact area between the metal electrode and the silicon substrate, reduces the line resistance and contact resistance, improves the filling factor, and also reduces the difficulty of process manufacturing and the cost of solar modules. Compared with the metal electrode with a relatively large aspect ratio (generally not less than 0.25) in the prior art, although the solar cell provided by the present invention reduces the area of ​​the back of the silicon substrate absorbing the incident light to a certain extent, it is found through research that the metal electrode with a quasi-rectangular structure with an aspect ratio of less than 0.05 can reflect the incident light on the front of the silicon substrate, so that the front of the silicon substrate absorbs the reflected light for a second time, which can make up for the photoelectric loss caused by the reduction of the area of ​​the back of the silicon substrate absorbing the incident light, thereby effectively improving the efficiency of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a cross-sectional schematic diagram of a silicon substrate and a first passivation layer in a solar cell according to an embodiment of the present invention;

[0041] Figure 2 is a cross-sectional schematic diagram of a silicon substrate and a passivation contact structure in a solar cell according to another embodiment of the present invention

[0042] Figure 3 is a cross-sectional schematic diagram of a silicon substrate, a passivation contact structure and a second passivation layer in a solar cell according to another embodiment of the present invention;

[0043] Figure 4 is a schematic cross-sectional view of the back side of a solar cell according to an embodiment of the present invention;

[0044] Figure 5 It is a main flow chart of a method for preparing a solar cell according to an embodiment of the present invention.

[0045] The reference numerals are as follows:

[0046] 10 Silicon substrate 101 Silicon substrate front side 102 Silicon substrate back side

[0047] 20 Passivation contact structure 201 First passivation layer 202 Silicon film layer

[0048] 30 metal electrode 40 second passivation layer DETAILED DESCRIPTION

[0049] In the following description and the appended claims, ohmic connection refers to the contact between metal and semiconductor, and the resistance of the contact surface is much smaller than the resistance of the semiconductor itself, so that when the component is operated, most of the voltage drop is in the active area rather than at the contact surface.

[0050] The back side of the silicon substrate is used to set a silicon thin film layer containing doping elements and a back side metal electrode.

[0051] The front side of the silicon substrate refers to the side that can absorb more sunlight. A front metal electrode is provided on the front side of the silicon substrate. The front metal electrode is a conductive material that forms an ohmic contact with the silicon substrate. It is responsible for collecting carriers in the silicon wafer and transporting them to the external circuit.

[0052] A quasi-rectangular structure refers to a structure similar to a rectangular parallelepiped, including a rectangular parallelepiped structure. This arrangement is because in the actual manufacturing process, it is difficult to ensure that the prepared metal electrode is a completely regular rectangular parallelepiped structure, and a back metal electrode similar to a rectangular parallelepiped structure (with an aspect ratio of less than 0.05) can solve the problems existing in the prior art, thereby reducing the difficulty of process manufacturing and the cost of solar cell modules, allowing the silicon substrate to reabsorb the reflected light of the metal electrode, thereby improving the efficiency of solar cells.

[0053] The line resistance of the metal electrode is mainly related to the cross-sectional area of ​​the transmission when the transmission distance is the same. The larger the cross-sectional area, the smaller the line resistance. The cross-sectional area can be roughly regarded as the product of the grid line width and the grid line height of the metal electrode. In the prior art, in order to avoid the back metal electrode from blocking the incident light from the back, the grid line width of the metal electrode is often narrowed to ensure the light absorption area of ​​the incident light from the back, thereby increasing the short-circuit current. At the same time, in order to avoid the line resistance of the metal electrode being too large, that is, to avoid a small cross-sectional area, it is necessary to maintain the height of the grid line at a high level, which ultimately leads to the grid line metal electrode on the back being a "high and narrow" strip structure. However, the high and narrow grid lines often have uneven thickness and easy deformation corresponding to each grid line, which increases the difficulty of process manufacturing and increases the component cost of the solar cell.

[0054] In the prior art, the gate metal electrode disposed on the back of the silicon substrate is a "tall and narrow" long strip-shaped structure (the aspect ratio of the "tall and narrow" is generally greater than or equal to 0.25). Since the width of the gate metal electrode on the back of the silicon substrate is relatively narrow, the width of the gate metal electrode on the back of the silicon substrate is difficult to control in the process, which increases the difficulty of process manufacturing; and the high and narrow gate lines often cause the corresponding thickness of each gate line to be uneven and easy to deform, which increases the difficulty of process manufacturing and increases the component cost of the solar cell; at the same time, the narrower gate lines reduce the contact area between the metal electrode and the silicon wafer, resulting in an increase in contact resistance, which reduces the fill factor and has limited improvement in the efficiency of the solar cell.

[0055] In order to solve the problems of general efficiency of solar cells in the prior art and high assembly cost of solar cells due to uneven thickness and easy deformation of corresponding grid lines, the solar cell provided in the embodiment of the present invention increases the width of the metal electrode and reduces the height of the metal electrode to increase the contact area between the metal electrode and the silicon wafer, reduce the contact resistance, and then improve the fill factor. At the same time, it can also reflect the incident light from the front of the silicon substrate, so that the silicon substrate reabsorbs the reflected light of the metal electrode, thereby effectively improving the efficiency of the solar cell. The metal electrode with a rectangular structure provided in the embodiment of the present invention has a low aspect ratio, which reduces the difficulty of process manufacturing and the assembly cost of the solar cell.

[0056] Specifically, Figures 1 to 4 As shown, a solar cell provided by an embodiment of the present invention includes: a silicon substrate 10, a passivation contact structure 20 and a metal electrode 30, wherein the passivation contact structure 20 is arranged on the back side 102 of the silicon substrate 10; the metal electrode 30 is in ohmic contact with the passivation contact structure 20; wherein the metal electrode 30 is a rectangular parallelepiped structure, and the aspect ratio of the rectangular parallelepiped structure is less than 0.05.

[0057] Furthermore, the passivation contact structure 20 further includes: a first passivation layer 201 disposed on the back side 102 of the silicon substrate 10 and a silicon thin film layer 202 containing doped elements, wherein the first passivation layer 201 is located between the silicon substrate 10 and the silicon thin film layer 202, and the doped elements are boron or phosphorus.

[0058] Specifically, Figure 1 A schematic cross-sectional view of the silicon substrate 10 and the first passivation layer 201 is shown. Figure 1 As can be seen in FIG. 1 , a first passivation layer 201 is disposed on the back side 102 of the silicon substrate 10 . Figure 2 A schematic cross-sectional view of a silicon substrate 10 and a passivation contact structure 20 is shown. Figure 2It can be seen that the passivation contact structure 20 includes a first passivation layer 201 and a silicon thin film layer 202. The silicon thin film layer 202 is arranged on the side of the first passivation layer 201 away from the back of the silicon substrate 10. The first passivation layer 201 is located between the silicon substrate 10 and the silicon thin film layer 202. Figure 3 The cross-sectional view of the silicon substrate 10, the passivation contact structure 20 and the second passivation layer 40 is shown. Figure 3 As can be seen in FIG. 1 , the second passivation layer 40 is located on a side of the passivation contact structure 20 away from the back surface 102 of the silicon substrate 10 . Figure 4 The cross-sectional view of the silicon substrate 10, the passivation contact structure 20, the second passivation layer 40 and the metal electrode 30 is shown. Figure 4 It can be seen that the cross section of the metal electrode 30 is a rectangle, wherein the side of the rectangle parallel to the back side 102 of the silicon substrate 10 is the width of the metal electrode 30, and the side of the rectangle perpendicular to the back side 102 of the silicon substrate 10 is the height of the metal electrode 30. The height of the metal electrode 30 is less than the width of the metal electrode 30 (specifically, the aspect ratio is less than 0.05). It can be seen that the metal electrode 30 penetrates the second passivation layer 40 and contacts the passivation contact structure 20. It can be further seen that the metal electrode 30 is in contact with the silicon thin film layer 202 of the passivation contact structure 20, and the metal electrode 30 and the silicon thin film layer 202 achieve ohmic contact. Since the height-to-width ratio of the metal electrode is small, the wider metal electrode increases the contact area between the metal electrode and the silicon substrate, reduces the line resistance and contact resistance, and improves the filling factor. At the same time, the wider metal electrode can reflect the incident light on the front side of the silicon substrate, so that the front side of the silicon substrate absorbs the reflected light for a second time, which can make up for the photoelectric loss caused by the reduction in the area of ​​the back side of the silicon substrate absorbing the incident light, thereby effectively improving the efficiency of the solar cell. Furthermore, the manufacturing process of metal electrodes with a smaller aspect ratio is simpler and less prone to deformation, thereby reducing the component cost of solar cells.

[0059] In the embodiment of the present invention, the width of the metal electrode located on the front side 101 of the silicon substrate 10 is smaller than the width of the metal electrode 30 located on the back side 102 of the silicon substrate 10. That is, the metal electrode disposed on the front side 101 of the silicon substrate 10 is still prepared by the existing conventional method, and is in a "high and narrow" strip-shaped structure, so as to prevent the metal electrode on the front side from blocking the sunlight, so as to facilitate the silicon substrate 10 to absorb the incident light on the front side, thereby maintaining the conversion efficiency of the incident light on the front side. The back metal electrode 30 is wide and flat (the aspect ratio is less than 0.05), so that the back metal electrode 30 can reflect the sunlight incident on the front side and passing through the silicon substrate 10, so that the silicon substrate 10 absorbs the incident light on the front side for the second time, further improving the efficiency of the solar cell.

[0060] In an embodiment of the present invention, the aspect ratio of the rectangular parallelepiped structure corresponding to the metal electrode 30 is less than 0.05, and the width of the rectangular parallelepiped structure ranges from 65 to 200 μm. For example, the width of the rectangular parallelepiped structure may be: 65 μm, 120 μm, 150 μm, 180 μm, 200 μm. In addition, the height of the rectangular parallelepiped structure ranges from 3 to 8 μm. For example, the height of the rectangular parallelepiped structure may be: 3 μm, 5 μm, 6 μm, 8 μm. Such a setting, on the one hand, avoids the waste of metal slurry required for screen printing, and on the other hand, ensures that the shading area of ​​the back incident light is reduced as much as possible, so that the secondary absorption of the silicon substrate 10 to the front incident light is increased while sacrificing only part of the back incident light.

[0061] In the embodiment of the present invention, the silicon thin film layer 202 includes a doping element, and the doping element is boron or phosphorus. It can be understood that the selection of the doping element is related to the type of the silicon substrate. If the silicon substrate is N-Si, the doping element corresponding to the silicon thin film layer 202 is phosphorus; if the silicon substrate 10 is P-Si, the doping element corresponding to the silicon thin film layer is boron. Further, the doping concentration of the doping element is 1.0E 19 atoms / cm 3 ~2.0E 21 atoms / cm 3 , for example, the doping concentration of the doping element is 1.0E 19 atoms / cm 3 , 1.5E 19 atoms / cm 3 , 2E 19 atoms / cm 3 Generally speaking, the doping process may be performed by ion implantation, deposition, furnace diffusion, etc., wherein the doping depth is generally less than or equal to the thickness of the silicon thin film layer 202 .

[0062] In the embodiment of the present invention, the silicon thin film layer 202 is a single layer film composed of any one of microcrystalline silicon, amorphous silicon, polycrystalline silicon, silicon oxide and silicon carbide, or a stacked layer film composed of any of the above. The thickness of the silicon thin film layer 202 is 5nm to 200nm.

[0063] In the embodiment of the present invention, the first passivation layer 201 is a single-layer film composed of a single non-metallic oxide, a laminated film composed of multiple non-metallic oxides, or a laminated film composed of at least one metal oxide and at least one non-metallic oxide; wherein the non-metallic oxide is silicon oxide, silicon nitride, silicon oxynitride, and the metal oxide is aluminum oxide or titanium oxide; the thickness of the first passivation layer 201 is 0.5nm to 2.5nm. The second passivation layer 40 is a single-layer film composed of a single non-metallic oxide, a laminated film composed of multiple non-metallic oxides, or a laminated film composed of at least one metal oxide and at least one non-metallic oxide; wherein the non-metallic oxide is silicon oxide, silicon nitride, silicon oxynitride, and the metal oxide is aluminum oxide or titanium oxide; the thickness of the second passivation layer 40 is 30 to 300nm (preferably, the thickness of the second passivation layer 40 is 100 to 300nm to achieve a better surface passivation effect); the refractive index of the second passivation layer 40 is 1.2 to 2.8.

[0064] In the embodiment of the present invention, the metal electrode 30 is prepared by wire mesh brushing and sintering, and the sintering temperature ranges from 750°C to 1000°C.

[0065] In addition, the above Figures 2 to 4 The setting range corresponding to the silicon thin film layer 202 in the structure shown may not fully cover the first passivation layer 201. It can be combined with the position of the front electrode set on the silicon substrate 10 to correspondingly set the silicon thin film layer 202 containing doped elements to effectively reduce the damage caused by the metal electrode to the first passivation layer 201, thereby improving its electrical performance.

[0066] The solar cell can be applied to a single-glass solar module or a double-glass solar module. In a preferred embodiment, it is applied to a double-glass solar module.

[0067] The solar cell provided by each of the above embodiments has a metal electrode disposed on the back of the silicon substrate with a rectangular parallelepiped structure and a wide flat structure with an aspect ratio of less than 0.05, so that the wider metal electrode can increase the contact area between the metal electrode and the silicon substrate, reduce the line resistance and contact resistance, and thus improve the fill factor. At the same time, compared with the narrower metal electrode in the prior art, the wider metal electrode in the present invention also reduces the difficulty of process manufacturing and the cost of solar modules. Compared with the metal electrode with a tall and narrow strip structure in the prior art, although the absorption of incident light from the back is reduced to a certain extent, due to the small amount of incident light from the back, the metal electrode with a rectangular parallelepiped structure with an aspect ratio of less than 0.05 can reflect the sunlight incident from the front and passing through the silicon substrate, so that the silicon substrate reabsorbs the reflected light of the metal electrode, thereby effectively improving the efficiency of the solar cell.

[0068] In the embodiment of the present invention, Figure 5As shown, the preparation method of the solar cell provided in each of the above embodiments may include the following steps:

[0069] Step S501 : forming a passivation contact structure 20 on the back side 102 of the silicon substrate 10 .

[0070] The passivation contact structure 20 formed on the back side 102 of the silicon substrate in this step helps to enhance the passivation effect of the back side of the solar cell, reduce the recombination of minority carriers inside the silicon substrate, and improve the conversion efficiency of the solar cell.

[0071] Further, according to an embodiment of the present invention, the passivation contact structure 20 comprises: a first passivation layer 201 disposed on the back side 102 of the silicon substrate 10 and a silicon thin film layer 202 containing doping elements.

[0072] According to an embodiment of the present invention, the specific steps for forming a passivation contact structure 20 on the back side 102 of the silicon substrate 10 may be: depositing a first passivation layer 201 on the back side 102 of the silicon substrate 10; depositing a silicon thin film layer 202 on the first passivation layer 201; doping the silicon thin film layer 202 with doping elements, and annealing the doped silicon thin film layer 202; wherein the doping element is boron or phosphorus.

[0073] In addition, in an embodiment of the present invention, the deposition range corresponding to the above-mentioned silicon thin film layer 202 may not fully cover the first passivation layer 201. It can be combined with the position of the front electrode set on the silicon substrate 10 to correspondingly set a silicon thin film layer 202 containing doped elements to effectively reduce the damage caused by the metal electrode to the first passivation layer 201, thereby improving its electrical properties.

[0074] Specifically, according to an embodiment of the present invention, the first passivation layer 201 is a single-layer film composed of a single non-metallic oxide, a stacked film composed of multiple non-metallic oxides, or a stacked film composed of at least one metal oxide and at least one non-metallic oxide; wherein the non-metallic oxide is silicon oxide, silicon nitride, silicon oxynitride, and the metal oxide is aluminum oxide, titanium oxide, and the thickness of the first passivation layer (201) is 0.5nm to 2.5nm. The silicon thin film layer 202 is a single-layer film composed of any one of microcrystalline silicon, amorphous silicon, polycrystalline silicon, silicon oxide, and silicon carbide, or a stacked film composed of any of the above, and the thickness of the silicon thin film layer 202 is 5nm to 200nm.

[0075] Step S502: preparing the metal electrode 30 by screen printing, so that the metal electrode 30 and the passivation contact structure 20 achieve ohmic contact; wherein the metal electrode 30 is a rectangular parallelepiped structure, and the aspect ratio of the rectangular parallelepiped structure is less than 0.05.

[0076] In the process of preparing the metal electrode 30 by screen printing, a sintering treatment is required, and the sintering temperature ranges from 750°C to 1000°C.

[0077] In the embodiment of the present invention, before the step of preparing the metal electrode 30 by screen printing, a second passivation layer 40 can be formed on the side of the passivation contact structure 20 away from the silicon substrate 10. The second passivation layer 40 is a single-layer film composed of a single non-metallic oxide, a stacked film composed of multiple non-metallic oxides, or a stacked film composed of at least one metal oxide and at least one non-metallic oxide; wherein the non-metallic oxide can be silicon oxide, silicon nitride, silicon oxynitride, and the metal oxide is aluminum oxide, titanium oxide; the thickness of the second passivation layer 40 is 30 to 300 nm (preferably, the thickness of the second passivation layer 40 is 100 to 300 nm to achieve a better surface passivation effect).

[0078] In the embodiment of the present invention, the aspect ratio of the rectangular parallelepiped structure corresponding to the metal electrode 30 is less than 0.05, and the width of the rectangular parallelepiped structure is in the range of 65 to 200 μm; and / or the height is in the range of 3 to 8 μm. Such a setting, on the one hand, avoids the waste of metal slurry required for screen printing, and on the other hand, ensures that the shading area of ​​the back incident light is reduced as much as possible, so that the secondary absorption of the reflected light of the metal electrode by the silicon substrate 10 is increased while sacrificing only part of the back incident light.

[0079] In the embodiment of the present invention, the width of the prepared metal electrode located on the front side of the silicon substrate 10 is smaller than the width of the prepared metal electrode 30 located on the back side of the silicon substrate 10. That is, the metal electrode arranged on the front side of the silicon substrate 10 is still prepared by the existing conventional method, and is in a "high and narrow" strip-shaped structure, so as to prevent the metal electrode on the front side from blocking the sunlight, so as to facilitate the silicon substrate 10 to absorb the incident light on the front side, thereby maintaining the conversion efficiency of the incident light on the front side. The back metal electrode 30 is wide and flat (the aspect ratio is less than 0.05), so that the back metal electrode 30 can reflect the sunlight incident on the front side and passing through the silicon substrate 10, so that the silicon substrate 10 absorbs the incident light on the front side for the second time, further improving the efficiency of the solar cell.

[0080] The solar cell prepared by the above process has a rectangular parallelepiped structure and a wide flat structure with an aspect ratio of less than 0.05, so that the wider metal electrode can increase the contact area between the metal electrode and the silicon substrate, reduce the line resistance and contact resistance, thereby improving the filling factor, and reducing the difficulty of process manufacturing and the cost of solar modules. Compared with the metal electrode with a high and narrow strip structure in the prior art, although the absorption of the incident light from the back is reduced to a certain extent, due to the small amount of incident light from the back, the metal electrode with a rectangular parallelepiped structure with an aspect ratio of less than 0.05 can reflect the sunlight incident from the front through the silicon substrate, so that the silicon substrate reabsorbs the reflected light of the metal electrode, thereby effectively improving the efficiency of the solar cell.

[0081] The preparation process of the solar cell is described in detail below through several specific embodiments.

[0082] Embodiment 1:

[0083] Step s11: cleaning the N-type silicon wafer;

[0084] Step s12: on the back side of the silicon wafer, a first passivation layer with a thickness of 0.5 nm is prepared by an atomic layer deposition (ALD) process; the first passivation layer is a single-layer film composed of silicon oxide;

[0085] Step s13: depositing a 5 nm thick silicon thin film layer on the first passivation layer by low pressure chemical vapor deposition (LPCVD), wherein the silicon thin film layer is a single layer film composed of polycrystalline silicon;

[0086] Step s14: Using ion implantation to dope the silicon thin film layer to a concentration of 1.0E 19 atoms / cm 3 The phosphorus doping depth does not exceed the thickness of the silicon film layer;

[0087] Step s15: performing annealing treatment on the doped silicon thin film layer, and removing the oxide layer grown on the surface of the silicon thin film layer after the annealing treatment by using an HF solution;

[0088] Step s16: Prepare a metal electrode with a width of 65 μm, a height of 3 μm, and an aspect ratio of 0.046 by screen printing, and realize ohmic contact between the metal electrode and the silicon thin film layer.

[0089] Among them, annealing the doped silicon thin film layer not only helps to activate the doping elements, but also realizes crystallization heat treatment of the silicon thin film layer, thereby further improving the performance of the silicon thin film layer.

[0090] Embodiment 2:

[0091] Step s21: cleaning the N-type silicon wafer;

[0092] Step s22: on the back side of the silicon wafer, a first passivation layer with a thickness of 1 nm is prepared by an ozone oxidation process; the first passivation layer is a single-layer film composed of silicon nitride;

[0093] Step s23: on the first passivation layer, a silicon thin film layer with a thickness of 50 nm is deposited by plasma enhanced chemical vapor deposition (PECVD), wherein the silicon thin film layer is a single-layer film composed of microcrystalline silicon;

[0094] Step s24: Using ion implantation to dope the silicon thin film layer to a concentration of 1.5E 19 atoms / cm 3 The phosphorus doping depth does not exceed the thickness of the silicon film layer;

[0095] Step s25: performing annealing treatment on the doped silicon thin film layer, and removing the oxide layer grown on the surface of the silicon thin film layer after the annealing treatment by using HF solution;

[0096] Step s26: growing a second passivation layer with a thickness of 30 nm on the silicon thin film layer by a tubular plasma enhanced chemical vapor deposition method, wherein the second passivation layer is a single-layer film composed of silicon oxide.

[0097] Step s27: Use screen printing and sintering at 750° C. to prepare a metal electrode with a width of 120 μm, a height of 5 μm, and an aspect ratio of 0.042, and realize ohmic contact between the metal electrode and the silicon thin film layer.

[0098] Among them, during the sintering process, the glass in the screen-printed metal slurry will penetrate the second passivation layer, so that the metal electrode and the silicon thin film layer are in ohmic contact. The wide and flat shape of the metal electrode (the aspect ratio of the rectangular structure is less than 0.05) effectively increases the contact area between the metal electrode and the silicon thin film layer, thereby reducing the contact resistance and improving the fill factor. At the same time, the wider metal electrode can reflect the sunlight incident from the front through the silicon substrate, so that the silicon substrate absorbs the front incident light for a second time, increasing the short-circuit current. On the other hand, the wide and flat metal electrons will not increase the metal recombination due to the increase in the contact area between the metal electrode and the silicon thin film layer, resulting in a decrease in the open circuit voltage of the battery. Therefore, the contact resistance can be reduced without affecting the open circuit voltage, and the fill factor and short-circuit current can be improved, effectively improving the conversion efficiency of the solar cell.

[0099] Embodiment 3:

[0100] Step s31: cleaning the P-type silicon wafer;

[0101] Step s32: on the back side of the silicon wafer, a first passivation layer with a thickness of 1.5 nm is prepared by an ozone oxidation process; the first passivation layer is a laminated film composed of silicon oxide and aluminum oxide;

[0102] Step s33: on the first passivation layer, a silicon thin film layer with a thickness of 100 nm is deposited by low pressure chemical vapor deposition (LPCVD), wherein the silicon thin film layer is a laminated film composed of microcrystalline silicon and polycrystalline silicon;

[0103] Step s34: Using a furnace tube diffusion process to dope the silicon thin film layer with a concentration of 1.5E 19 atoms / cm 3 The boron doping depth does not exceed the thickness of the silicon film layer;

[0104] Step s35: annealing the doped silicon thin film layer, and removing the oxide layer grown on the surface of the silicon thin film layer after the annealing using an HF solution;

[0105] Step s36: growing a second passivation layer with a thickness of 100 nm on the silicon thin film layer by a tubular plasma enhanced chemical vapor deposition method, wherein the second passivation layer is a laminated film composed of silicon oxide and titanium oxide.

[0106] Step s37: Use screen printing and sintering at 850° C. to prepare a metal electrode with a width of 150 μm, a height of 6 μm, and an aspect ratio of 0.04, and realize ohmic contact between the metal electrode and the silicon thin film layer.

[0107] Embodiment 4:

[0108] Step s41: cleaning the P-type silicon wafer;

[0109] Step s42: on the back side of the silicon wafer, a first passivation layer with a thickness of 2 nm is prepared by an ozone oxidation process; the first passivation layer is a laminated film composed of silicon oxide, silicon nitride and aluminum oxide;

[0110] Step s43: on the first passivation layer, a silicon thin film layer with a thickness of 150 nm is deposited by low pressure chemical vapor deposition (LPCVD), wherein the silicon thin film layer is a laminated film composed of microcrystalline silicon, amorphous silicon and polycrystalline silicon;

[0111] Step s44: doping the silicon thin film layer with a concentration of 2E by ion implantation 19 atoms / cm 3 The boron doping depth does not exceed the thickness of the silicon film layer;

[0112] Step s45: performing annealing treatment on the doped silicon thin film layer, and removing the oxide layer grown on the surface of the silicon thin film layer after the annealing treatment by using HF solution;

[0113] Step s46: growing a second passivation layer with a thickness of 200 nm on the silicon thin film layer by plate-type plasma enhanced chemical vapor deposition, wherein the second passivation layer is a single-layer film composed of silicon oxide, silicon nitride and titanium oxide.

[0114] Step s47: Use screen printing and sintering at 950° C. to prepare a metal electrode with a width of 180 μm, a height of 8 μm, and an aspect ratio of 0.044, and realize ohmic contact between the metal electrode and the silicon thin film layer.

[0115] Embodiment 5:

[0116] Step s51: cleaning the P-type silicon wafer;

[0117] Step s52: on the back side of the silicon wafer, a first passivation layer with a thickness of 2.5 nm is prepared by a nitric acid oxidation process; the first passivation layer is a laminated film composed of silicon oxide, silicon nitride, titanium oxide and aluminum oxide;

[0118] Step s53: on the first passivation layer, a silicon thin film layer with a thickness of 200 nm is deposited by low pressure chemical vapor deposition (LPCVD), wherein the silicon thin film layer is a laminated film composed of microcrystalline silicon, silicon oxide, silicon carbide and polycrystalline silicon;

[0119] Step s54: doping the silicon thin film layer with a concentration of 2E by ion implantation 19 atoms / cm 3 The boron doping depth does not exceed the thickness of the silicon film layer;

[0120] Step s55: performing annealing treatment on the doped silicon thin film layer, and removing the oxide layer grown on the surface of the silicon thin film layer after the annealing treatment by using HF solution;

[0121] Step s56: growing a second passivation layer with a thickness of 300 nm on the silicon thin film layer by a tubular plasma enhanced chemical vapor deposition method. The second passivation layer is a stacked film composed of silicon oxide, silicon nitride, silicon oxynitride, titanium oxide and aluminum oxide.

[0122] Step s57: Use screen printing and sinter at 1000° C. to prepare a metal electrode with a width of 200 μm, a height of 8 μm, and an aspect ratio of 0.04, and realize ohmic contact between the metal electrode and the silicon thin film layer.

[0123] The embodiments of the present invention provide the following technical solutions and combinations of the technical solutions.

[0124] Technical solution 1, a solar cell, comprising: a silicon substrate 10, a passivation contact structure 20 and a metal electrode 30; wherein,

[0125] The passivation contact structure 20 is disposed on the back side 102 of the silicon substrate 10;

[0126] The metal electrode 30 is in ohmic contact with the passivation contact structure 20 ; wherein the metal electrode 30 is a cuboid-like structure, and the aspect ratio of the cuboid-like structure is less than 0.05.

[0127] Technical solution 2: The solar cell according to technical solution 1,

[0128] The width of the cuboid structure ranges from 65 to 200 μm;

[0129] and / or,

[0130] The height range is 3 to 8 μm.

[0131] Technical solution 3: The solar cell according to technical solution 1,

[0132] The width of the metal electrode located on the front side 101 of the silicon substrate 10 is smaller than the width of the metal electrode 30 located on the back side 102 of the silicon substrate 10 .

[0133] Technical solution 4: The solar cell according to technical solution 1,

[0134] The passivation contact structure 20 further includes: a first passivation layer 201 disposed on the back side 102 of the silicon substrate 10 and a silicon thin film layer 202 containing doping elements, wherein the first passivation layer 201 is located between the silicon substrate 10 and the silicon thin film layer 202, and the doping element is boron or phosphorus.

[0135] Technical solution 5. The solar cell according to technical solution 4,

[0136] The first passivation layer 201 is a single-layer film composed of a single non-metallic oxide, a stacked film composed of multiple non-metallic oxides, or a stacked film composed of at least one metal oxide and at least one non-metallic oxide; wherein the non-metallic oxide is silicon oxide, silicon nitride, silicon oxynitride, and the metal oxide is aluminum oxide, titanium oxide; the thickness of the first passivation layer 201 is 0.5nm to 2.5nm.

[0137] Technical solution 6. The solar cell according to technical solution 4,

[0138] The silicon thin film layer 202 is a single layer film composed of any one of microcrystalline silicon, amorphous silicon, polycrystalline silicon, silicon oxide and silicon carbide, or a stacked layer film composed of any of the above. The thickness of the silicon thin film layer 202 is 5nm to 200nm.

[0139] Technical solution 7. The solar cell according to technical solution 4,

[0140] The doping concentration of the doping element is 1.0E19 atoms / cm 3 ~2.0E 21 atoms / cm 3 ,

[0141] The doping depth is less than or equal to the thickness of the silicon thin film layer 202 .

[0142] Technical solution 8. The solar cell according to technical solution 1,

[0143] A second passivation layer 40 is disposed on a side of the passivation contact structure 20 away from the back surface 102 of the silicon substrate 10 .

[0144] Technical solution 9. The solar cell according to technical solution 8,

[0145] The second passivation layer 40 is a single-layer film composed of a single non-metallic oxide, a stacked film composed of multiple non-metallic oxides, or a stacked film composed of at least one metal oxide and at least one non-metallic oxide; wherein the non-metallic oxide is silicon oxide, silicon nitride, silicon oxynitride, and the metal oxide is aluminum oxide, titanium oxide; the thickness of the second passivation layer 40 is 30 to 300 nm.

[0146] Technical solution 10. A method for preparing a solar cell as described in any one of technical solutions 1 to 9, the method comprising:

[0147] A passivation contact structure 20 is formed on the back side 102 of the silicon substrate 10;

[0148] The metal electrode 30 is prepared by screen printing, so that the metal electrode 30 and the passivation contact structure 20 achieve ohmic contact; wherein the metal electrode 30 is a rectangular parallelepiped structure, and the aspect ratio of the rectangular parallelepiped structure is less than 0.05.

[0149] Technical solution 11. The preparation method according to technical solution 10,

[0150] The width of the cuboid structure ranges from 65 to 200 μm;

[0151] and / or,

[0152] The height range is 3 to 8 μm.

[0153] Technical solution 12. The preparation method according to technical solution 10,

[0154] A metal electrode is prepared on the front side 101 of the silicon substrate 10 , so that the width of the metal electrode on the front side 101 of the silicon substrate 10 is smaller than the width of the metal electrode 30 on the back side 102 of the silicon substrate 10 .

[0155] Technical solution 13. The preparation method according to technical solution 10,

[0156] The passivation contact structure 20 includes: a first passivation layer 201 disposed on the back side 102 of the silicon substrate 10 and a silicon thin film layer 202 containing doping elements;

[0157] The passivation contact structure 20 is formed on the back side 102 of the silicon substrate 10, including:

[0158] Forming a first passivation layer 201 on the back side 102 of the silicon substrate 10;

[0159] Depositing a silicon thin film layer 202 on the first passivation layer 201;

[0160] The silicon thin film layer 202 is doped with a doping element, and the doped silicon thin film layer 202 is annealed; wherein the doping element is boron or phosphorus.

[0161] Technical solution 14. The preparation method according to technical solution 13,

[0162] The first passivation layer 201 is a single-layer film composed of a single non-metallic oxide, a stacked film composed of multiple non-metallic oxides, or a stacked film composed of at least one metal oxide and at least one non-metallic oxide; wherein the non-metallic oxide is silicon oxide, silicon nitride, or silicon oxynitride, and the metal oxide is aluminum oxide or titanium oxide, and the thickness of the first passivation layer 201 is 0.5 nm to 2.5 nm.

[0163] Technical solution 15. The preparation method according to technical solution 13,

[0164] The silicon thin film layer 202 is a single layer film composed of any one of microcrystalline silicon, amorphous silicon, polycrystalline silicon, silicon oxide and silicon carbide, or a stacked layer film composed of any of the above. The thickness of the silicon thin film layer 202 is 5nm to 200nm.

[0165] Technical solution 16. The preparation method according to technical solution 13,

[0166] The doping concentration of the doping element is 1.0E 19 atoms / cm 3 ~2.0E 21 atoms / cm 3 ,

[0167] The doping depth is less than or equal to the thickness of the silicon thin film layer 202 .

[0168] Technical solution 17. The preparation method according to technical solution 10,

[0169] A second passivation layer 40 is formed on a side of the passivation contact structure 20 away from the silicon substrate 10 .

[0170] Technical solution 18. The preparation method according to technical solution 17,

[0171] The second passivation layer 40 is a single-layer film composed of a single non-metallic oxide, a stacked film composed of multiple non-metallic oxides, or a stacked film composed of at least one metal oxide and at least one non-metallic oxide; wherein the non-metallic oxide is silicon oxide, silicon nitride, silicon oxynitride, and the metal oxide is aluminum oxide, titanium oxide; the thickness of the second passivation layer 40 is 30 to 300 nm.

[0172] The introduction provided in the above steps is only used to help understand the method, structure and core idea of ​​the present invention. For ordinary technicians in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also belong to the scope of protection of the claims of the present invention.

Claims

1. A solar cell, characterized in that: include: A silicon substrate (10), a passivation contact structure (20) and a metal electrode (30); wherein: The passivation contact structure (20) is arranged on the back side (102) of the silicon substrate (10); The metal electrode (30) is in ohmic contact with the passivation contact structure (20); wherein the metal electrode (30) is a quasi-cuboid structure, and the aspect ratio of the quasi-cuboid structure is less than 0.05; The width of the rectangular parallelepiped structure is in the range of 65 to 200 μm, and the height is in the range of 3 to 8 μm; The passivation contact structure (20) further comprises: a first passivation layer (201) disposed on the back side (102) of the silicon substrate (10) and a silicon thin film layer (202) containing a doping element, wherein the first passivation layer (201) is located between the silicon substrate (10) and the silicon thin film layer (202), and the doping element is boron or phosphorus.

2. The solar cell according to claim 1, characterized in that The width of the metal electrode located on the front side (101) of the silicon substrate (10) is smaller than the width of the metal electrode (30) located on the back side (102) of the silicon substrate (10).

3. The solar cell according to claim 1, characterized in that The first passivation layer (201) is a single-layer film composed of a single non-metallic oxide, a stacked film composed of multiple non-metallic oxides, or a stacked film composed of at least one metal oxide and at least one non-metallic oxide; wherein the non-metallic oxide is silicon oxide, silicon nitride, or silicon oxynitride, and the metal oxide is aluminum oxide or titanium oxide; and the thickness of the first passivation layer (201) is 0.5 nm to 2.5 nm.

4. The solar cell according to claim 1, characterized in that The silicon thin film layer (202) is a single layer film composed of any one of microcrystalline silicon, amorphous silicon, polycrystalline silicon, silicon oxide and silicon carbide, or a stacked layer film composed of any of the above. The thickness of the silicon thin film layer (202) is 5nm to 200nm.

5. The solar cell according to claim 1, characterized in that: The doping concentration of the doping element is 1.0E 19 atoms / cm 3 ~2.0E 21 atoms / cm 3 , The doping depth is less than or equal to the thickness of the silicon thin film layer (202).

6. The solar cell according to claim 1, characterized in that A second passivation layer (40) is provided on a side of the passivation contact structure (20) away from the back side (102) of the silicon substrate (10).

7. The solar cell according to claim 6, characterized in that: The second passivation layer (40) is a single-layer film composed of a single non-metallic oxide, a stacked film composed of multiple non-metallic oxides, or a stacked film composed of at least one metal oxide and at least one non-metallic oxide; wherein the non-metallic oxide is silicon oxide, silicon nitride, silicon oxynitride, and the metal oxide is aluminum oxide, titanium oxide; and the thickness of the second passivation layer (40) is 30 to 300 nm.

8. The method for preparing a solar cell according to any one of claims 1 to 7, characterized in that: include, forming a passivation contact structure (20) on the back side (102) of the silicon substrate (10); The metal electrode (30) is prepared by screen printing, so that the metal electrode (30) and the passivation contact structure (20) achieve ohmic contact; wherein the metal electrode (30) is a quasi-rectangular parallelepiped structure, and the aspect ratio of the quasi-rectangular parallelepiped structure is less than 0.

05.

9. The preparation method according to claim 8, The width of the cuboid structure ranges from 65 to 200 μm; and / or, The height range is 3 to 8 μm.

10. The preparation method according to claim 8, A metal electrode is prepared on the front side (101) of the silicon substrate (10), so that the width of the metal electrode located on the front side (101) of the silicon substrate (10) is smaller than the width of the metal electrode (30) located on the back side (102) of the silicon substrate (10).

11. The preparation method according to claim 8, The passivation contact structure (20) comprises: A first passivation layer (201) and a silicon thin film layer (202) containing doping elements are arranged on the back side (102) of the silicon substrate (10); The method of forming a passivation contact structure (20) on the back side (102) of the silicon substrate (10) comprises: forming a first passivation layer (201) on the back side (102) of the silicon substrate (10); Depositing a silicon thin film layer (202) on the first passivation layer (201); The silicon thin film layer (202) is doped with a doping element, and the doped silicon thin film layer (202) is annealed; wherein the doping element is boron or phosphorus.

12. The preparation method according to claim 11, The first passivation layer (201) is a single-layer film composed of a single non-metallic oxide, a stacked film composed of multiple non-metallic oxides, or a stacked film composed of at least one metal oxide and at least one non-metallic oxide; wherein, The non-metallic oxide is silicon oxide, silicon nitride, or silicon oxynitride; the metal oxide is aluminum oxide or titanium oxide; and the thickness of the first passivation layer (201) is 0.5 nm to 2.5 nm.

13. The preparation method according to claim 11, The silicon thin film layer (202) is a single layer film composed of any one of microcrystalline silicon, amorphous silicon, polycrystalline silicon, silicon oxide and silicon carbide, or a stacked layer film composed of any of the above. The thickness of the silicon thin film layer (202) is 5nm to 200nm.

14. The preparation method according to claim 11, The doping concentration of the doping element is 1.0E 19 atoms / cm 3 ~2.0E 21 atoms / cm 3 , The doping depth is less than or equal to the thickness of the silicon thin film layer (202).

15. The preparation method according to claim 8, A second passivation layer (40) is formed on a side of the passivation contact structure (20) away from the silicon substrate (10).

16. The preparation method according to claim 15, The second passivation layer (40) is a single-layer film composed of a single non-metallic oxide, a stacked film composed of multiple non-metallic oxides, or a stacked film composed of at least one metal oxide and at least one non-metallic oxide; wherein, The non-metallic oxide is silicon oxide, silicon nitride, or silicon oxynitride; the metal oxide is aluminum oxide or titanium oxide; and the thickness of the second passivation layer (40) is 30 to 300 nm.

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