CN210897294U - Solar cell - Google Patents

Abstract

The present application provides a solar cell, comprising a semiconductor substrate, a metal electrode, a tunneling layer and a doped polysilicon layer sequentially stacked on one surface of the semiconductor substrate, the doped polysilicon layer having a first part and a second part part, the metal electrode is in contact with the first part, the thickness of the first part is larger than the thickness of the second part, and the doping concentration of the first part is larger than that of the second part. The thickness of the first part is set to be large and the doping concentration is high, which can effectively reduce the recombination loss of the metal electrode region; the thickness of the second part is small and the doping concentration is low, which can passivate the non-electrode region of the semiconductor substrate. At the same time, reduce the absorption of light.

Description

Solar battery

technical field

The present application relates to the technical field of solar power generation, and in particular, to a solar cell.

Background technique

With the rapid development of photovoltaic technology, the market demand for high-efficiency cells and modules is also growing. As far as crystalline silicon cells are concerned, in order to reduce the recombination loss on the cell surface and reduce the contact resistance of metal electrodes, a passivation structure combining a tunnel oxide layer and a polysilicon film layer is disclosed in the industry.

However, the polysilicon film layer in the above-mentioned passivation structure has a strong light absorption coefficient, which reduces the short-circuit current of the battery, thereby limiting the improvement of the battery efficiency. At present, the current loss is mainly reduced by reducing the thickness of the polysilicon film layer as much as possible; or the above-mentioned tunnel oxide layer and polysilicon film layer are only provided in the metal electrode area of the battery, which is difficult to take into account the light absorption and passivation effects of the battery. The industry also discloses a scheme of disposing polysilicon layers with different thicknesses in the metal electrode area and the non-electrode area, and reducing the light loss in the non-electrode area by reducing the thickness of the polysilicon layer in the non-electrode area. However, in order to ensure the uniformity and stability of the film structure, the thickness of the polysilicon film in the non-electrode area cannot be reduced infinitely. Under the existing process, how to further optimize the cell structure and improve the cell conversion efficiency has become an urgent technical problem to be solved in the industry. .

Utility model content

The purpose of the present application is to provide a solar cell, which can improve the surface passivation performance of a semiconductor substrate, ensure light absorption, and improve conversion efficiency.

In order to achieve the above purpose, an embodiment of the present application provides a solar cell, comprising a semiconductor substrate, a metal electrode, a tunneling layer and a doped polysilicon layer sequentially stacked on one surface of the semiconductor substrate, the doped polysilicon The layer has a first portion and a second portion, the metal electrode is in contact with the first portion, the thickness of the first portion is greater than the thickness of the second portion, and the doping concentration of the first portion is greater than that of the second portion. doping concentration.

As a further improvement of the embodiments of the present application, the doping concentration of the first part is 1E20-8E20 cm ^-3 ; the doping concentration of the second part is 2E19-8E19 cm ^-3 .

As a further improvement of the embodiments of the present application, the thickness of the first part is set to be 80-300 nm, and the thickness of the second part is set to be 10-80 nm.

As a further improvement of the embodiments of the present application, the tunneling layer is set to be a silicon oxide film or a silicon oxynitride film or a composite film obtained by stacking a silicon oxide film and a silicon oxynitride film on each other. The thickness of the tunneling layer is Set to 0.5 to 3 nm.

As a further improvement of the embodiments of the present application, the solar cell further includes an anti-reflection layer disposed on the surface of the doped polysilicon layer on the side facing away from the semiconductor substrate, and the metal electrode penetrates the anti-reflection layer and communicates with the anti-reflection layer. contact with the first part.

As a further improvement of the embodiments of the present application, the anti-reflection layer includes a first anti-reflection film layer and a second anti-reflection film layer stacked on the surface of the first anti-reflection film layer on the side facing away from the semiconductor substrate. The thickness of the first anti-reflection film layer is smaller than the thickness of the second anti-reflection film layer, and the refractive index of the first anti-reflection film layer is greater than the refractive index of the second anti-reflection film layer.

As a further improvement of the embodiments of the present application, the tunneling layer and the doped polysilicon layer are sequentially stacked on the front side of the semiconductor substrate; the solar cell further includes a back passivation layer formed on the back side of the semiconductor substrate , a back electrode passing through the back passivation layer and in contact with the semiconductor substrate.

As a further improvement of the embodiments of the present application, the semiconductor substrate is a P-type silicon wafer; the back passivation layer is set to be an Al ₂ O ₃ film layer, and the thickness of the Al ₂ O ₃ film layer is set to 3-20 nm .

As a further improvement of the embodiments of the present application, the solar cell is configured as a double-sided cell, and the backside of the solar cell is sequentially provided with a backside tunneling layer, a backside doped polysilicon layer and a backside anti-reflection layer.

As a further improvement of the embodiment of the present application, the backside doped polysilicon layer has a third part and a fourth part, the thickness of the third part is greater than the thickness of the fourth part, and the doping of the third part The concentration is greater than the doping concentration of the fourth part; the solar cell further includes a back surface electrode penetrating the back surface anti-reflection layer and in contact with the third part.

The beneficial effects of the present application are: using the solar cell of the present application, by optimizing the structure of the doped polysilicon layer, the thickness of the first part is set larger and the doping concentration is higher, which can effectively reduce the recombination of the metal electrode region. loss and contact resistance; the second part has a small thickness and a low doping concentration, which reduces the absorption of light while passivating the non-electrode region of the semiconductor substrate, which is beneficial to the improvement of the conversion efficiency of the solar cell.

Description of drawings

1 is a schematic structural diagram of a first embodiment of a solar cell of the present application;

2 is a schematic structural diagram of a second embodiment of the solar cell of the present application;

3 is a schematic structural diagram of a third embodiment of the solar cell of the present application;

FIG. 4 is a schematic structural diagram of a fourth embodiment of the solar cell of the present application.

10-semiconductor substrate; 11-diffusion layer; 20-tunneling layer; 30-doped polysilicon layer; 31-first part; 32-second part; 20'-backside tunneling layer; 30'-backside doped polysilicon layer; 33-third part; 34-fourth part; 40-anti-reflection layer; 50-metal electrode; 60-back passivation layer; 70-back electrode, 80-back anti-reflection layer.

Detailed ways

The present application will be described in detail below with reference to the embodiments shown in the accompanying drawings. However, this embodiment does not limit the present application, and the structural, method, or functional transformations made by those of ordinary skill in the art according to this embodiment are all included in the protection scope of the present application.

1 , the solar cell 100 provided by the present application includes a semiconductor substrate 10, a tunneling layer 20, a doped polysilicon layer 30, an anti-reflection layer 40, and a tunneling layer 20 sequentially stacked on one side of the semiconductor substrate 10. The metal electrode 50 which penetrates the anti-reflection layer 40 and is in contact with the doped polysilicon layer 30 .

The tunneling layer 20 can isolate the metal electrode 50 from contacting the semiconductor substrate 10 without affecting the current transfer. It is combined with the doped polysilicon layer 30 to improve the surface passivation effect of the semiconductor substrate 10 and reduce the reverse saturation current. J0. Here, the tunneling layer 20 is configured as a silicon oxide film, a silicon oxynitride film, or a composite film obtained by stacking both of the silicon oxide film and the silicon oxynitride film. The thickness of the tunneling layer 20 is set to be 0.5˜3 nm, and more preferably, the thickness of the tunneling layer 20 is set to be 1˜2 nm.

The doped polysilicon layer 30 has a first portion 31 and a second portion 32 beside the first portion 31 , and the metal electrode 50 is disposed on the first portion 31 . The thickness of the first portion 31 is greater than that of the second portion 32, and the doping concentration of the first portion 31 is greater than that of the second portion 32, so that the absorption of incident light by the second portion 32 is smaller than that of the second portion 32. Absorption of incident light by a portion 31. In other words, the first portion 31 is disposed in the electrode region of the semiconductor substrate 10 , which is located between the metal electrode 50 and the tunneling layer 20 ; the second portion 32 is disposed in the non-electrode region of the semiconductor substrate 10 . electrode area. For the electrode area and the non-electrode area, the doped polysilicon layer 30 can be designed by distinguishing thickness and doping concentration, which can not only reduce the recombination loss and contact resistance at the position of the metal electrode 50, but also reduce the light absorption of the non-electrode area. influences.

The thickness of the first part 31 can be set to 80-300 nm; the second part 32 is usually obtained by partial etching. If the uniform stability of the film layer needs to be ensured under the existing process conditions, the second part 32 The thickness is preferably 10 to 80 nm. Moreover, the doping concentration of the first portion 31 is 1E20˜8E20 cm ⁻³ ; the doping concentration of the second portion 32 is 2E19˜8E19 cm ⁻³ . In the actual preparation process, we can set the thickness of the first part 31 to 80 nm, 120 nm, 170 nm or 200 nm; and set the thickness of the second part 32 to 10 nm, 20 nm or 30 nm. It should be noted that the set thicknesses of the first part 31 and the second part 32 are not exact value points in the strict sense, but the corresponding film thicknesses are controlled to be within a reasonable fluctuation range of the corresponding set thicknesses according to the on-site process.

In order to improve the film performance and anti-reflection effect of the anti-reflection layer 40, and at the same time take into account the "burn-through" performance of the anti-reflection layer 40, the anti-reflection layer 40 is adjusted by process parameters such as gas flow rate, reaction time, and temperature. 40 A layered or graded film structure can be provided. Here, the anti-reflection layer 40 has a first anti-reflection film layer, a second anti-reflection film layer stacked on the surface of the first anti-reflection film layer away from the semiconductor substrate 10, the first anti-reflection film layer The thickness of the reflection film layer is smaller than the thickness of the second anti-reflection film layer, and the refractive index of the first anti-reflection film layer is greater than the refractive index of the second anti-reflection film layer. The anti-reflection layer 40 is composed of several silicon nitride film layers with different refractive indices and thicknesses, and the thickness is preferably 70-85 nm. Of course, the anti-reflection layer 40 can also be provided with silicon oxide and silicon oxynitride film layers with relatively small refractive indices. In this case, the thickness of the anti-reflection layer 40 needs to be appropriately increased, preferably 80-100 nm.

In this embodiment, the semiconductor substrate 10 is set as a P-type silicon wafer, and its resistivity is set at 0.5-6 Ω·cm. The tunneling layer 20 , the doped polysilicon layer 30 , and the anti-reflection layer 40 are sequentially disposed on the front surface of the semiconductor substrate 10 , and the metal electrode 50 is the front electrode of the solar cell 100 . The metal electrode 50 is preferably a silver electrode.

The solar cell 100 further includes a back passivation layer 60 formed on the back surface of the semiconductor substrate 10 , and a back electrode 70 passing through the back passivation layer 60 and in contact with the semiconductor substrate 10 . Wherein, the back passivation layer 60 can be set to be an Al ₂ O ₃ film layer, and the thickness of the Al ₂ O ₃ film layer is set to be 3-20 nm. Here, the solar cell 100 is configured as a double-sided cell, and the solar cell 100 further includes a backside anti-reflection layer 80 stacked on the surface of the backside passivation layer 60 away from the semiconductor substrate 10, so The backside anti-reflection layer 80 can also use a silicon nitride film, and the thickness of the backside anti-reflection layer 80 is set to 60-150 nm.

Referring to FIG. 2 , in another embodiment of the present application, after the surface treatment of the semiconductor substrate 10 is completed, front-side diffusion is first performed to obtain a corresponding diffusion layer 11 , and the diffusion layer 11 can avoid doping the polysilicon layer. 30 damage will affect the transmission of surface current, and the corresponding structure of the solar cell 100 is more stable and reliable. In actual preparation, HF solution is used to clean and dry the diffused semiconductor substrate 10 , and then the tunneling layer 20 and the doped polysilicon layer 30 are sequentially prepared on the diffusion layer 11 . The doping type is consistent with the doping type of the doped polysilicon layer 30 .

Referring to FIG. 3 , in another embodiment of the present application, the solar cell 100 is configured as a double-sided cell, and the backside of the solar cell 100 is further stacked with a backside tunneling layer 20 ′, a backside doped polysilicon layer 30 ′, backside anti-reflection layer 80 . The backside doped polysilicon layer 30 ′ has a third portion 33 and a fourth portion 34 , the thickness of the third portion 33 is greater than that of the fourth portion 34 , and the doping concentration of the third portion 33 is greater than Doping concentration of the fourth portion 34 , the back electrode 70 penetrates the back anti-reflection layer 80 and is in contact with the third portion 33 . The doping type of the backside doped polysilicon layer 30 ′ is opposite to that of the doped polysilicon layer 30 . The above design achieves passivation of the backside of the semiconductor substrate 10 while reducing the influence on the backside light absorption.

As shown in FIG. 4 , for a double-sided cell, the above-mentioned back-side tunneling layer 20 ′ and back-side doped polysilicon layer 30 ′ can also be provided only on the back surface of the semiconductor substrate 10 . The backside electrode 70 penetrates the backside anti-reflection layer 80 and is in contact with the backside doped polysilicon layer 30 ′; the front surface of the semiconductor substrate 10 is formed with a diffusion layer 11 , and the metal electrode 50 penetrates the backside doped polysilicon layer 30 ′. The anti-reflection layer 40 forms ohmic contact with the diffusion layer 11 . Of course, the diffusion layer 11 and the anti-reflection layer 40 can also be directly provided with a front passivation film layer, which will not be repeated here.

To sum up, in the solar cell 100 of the present application, the surface of the semiconductor substrate 10 is effectively passivated through the tunneling layer 20 and the doped polysilicon layer 30 . The first part 31 is thicker and has a higher doping concentration, which can effectively reduce the recombination loss and contact resistance of the metal electrode 50 region; While passivating the non-electrode region of the solar cell, the absorption of light is reduced, which is beneficial to the improvement of the conversion efficiency of the solar cell 100 .

It should be understood that although this specification is described in terms of embodiments, not every embodiment only includes an independent technical solution, and this description in the specification is only for the sake of clarity, and those skilled in the art should take the specification as a whole, and each The technical solutions in the embodiments can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

The series of detailed descriptions listed above are only specific descriptions for the feasible embodiments of the present application, and they are not intended to limit the protection scope of the present application. Changes should be included within the scope of protection of this application.

Claims (9)

1. A solar cell, comprising a semiconductor substrate and a metal electrode, characterized in that: the solar cell further comprises a tunneling layer and a doped polycrystalline silicon layer which are sequentially stacked on the surface of one side of the semiconductor substrate, the doped polycrystalline silicon layer is provided with a first part and a second part, the metal electrode is in contact with the first part, the thickness of the first part is larger than that of the second part, and the doping concentration of the first part is larger than that of the second part.

2. The solar cell of claim 1, wherein: the thickness of the first part is set to be 80-300 nm, and the thickness of the second part is set to be 10-80 nm.

3. The solar cell of claim 1, wherein: the tunneling layer is a silicon oxide film or a silicon oxynitride film or a composite film formed by mutually laminating the silicon oxide film and the silicon oxynitride film, and the thickness of the tunneling layer is set to be 0.5-3 nm.

4. The solar cell of claim 1, wherein: the solar cell further comprises an antireflection layer arranged on the surface of the doped polycrystalline silicon layer on the side away from the semiconductor substrate, and the metal electrode penetrates through the antireflection layer and is in contact with the first part.

5. The solar cell of claim 4, wherein: the antireflection layer comprises a first antireflection film layer, a second antireflection film layer stacked on the first antireflection film layer and deviating from the first antireflection film layer on the surface of one side of the semiconductor substrate, the thickness of the first antireflection film layer is smaller than that of the second antireflection film layer, and the refractive index of the first antireflection film layer is larger than that of the second antireflection film layer.

6. The solar cell of claim 1, wherein: the tunneling layer and the doped polycrystalline silicon layer are sequentially stacked on the front surface of the semiconductor substrate; the solar cell further includes a back passivation layer formed on the back surface of the semiconductor substrate, and a back electrode penetrating the back passivation layer and contacting the semiconductor substrate.

7. The solar cell of claim 6, wherein: the semiconductor substrate is a P-type silicon wafer; the back passivation layer is set to be Al₂O₃Film layer of said Al₂O₃Of a film layerThe thickness is set to be 3-20 nm.

8. The solar cell of claim 1, wherein: the solar cell is a double-sided cell, and a back tunneling layer, a back doped polycrystalline silicon layer and a back antireflection layer are sequentially stacked on the back of the solar cell.

9. The solar cell of claim 8, wherein: the back side doped polycrystalline silicon layer is provided with a third part and a fourth part, the thickness of the third part is greater than that of the fourth part, and the doping concentration of the third part is greater than that of the fourth part; the solar cell further includes a back electrode penetrating the back anti-reflective layer and contacting the third portion.

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