CN115579403A - Solar cell, preparation method thereof and photovoltaic module - Google Patents

Abstract

The invention discloses a solar cell, a preparation method thereof and a photovoltaic module, wherein the solar cell comprises: a substrate having a front surface and a back surface, the front surface and the back surface being disposed opposite to each other in a thickness direction of the substrate; a dielectric layer on the back surface; the back doping layer is positioned on the surface of the dielectric layer; the n silicon nitride layers are arranged on the back doping layer; the m layers of silicon oxynitride layers are arranged on the surface of the outermost silicon nitride layer; and the k-layer silicon oxide layer is arranged on the surface of the outermost silicon oxynitride layer. Compared with the prior art, the laminated film structure of the silicon nitride layer, the silicon oxynitride layer and the silicon oxide layer replaces the traditional silicon nitride layer, so that the solar cell has the advantages of high conversion efficiency, high process compatibility, high double-sided rate and the like, the back reflectivity is reduced, and the double-sided rate of the cell is improved.

Description

Solar cell, preparation method thereof and photovoltaic module

Technical Field

The invention relates to the technical field of photovoltaic cells, in particular to a solar cell, a preparation method thereof and a photovoltaic module.

Background

TOPCon is a Tunnel Oxide Passivated Contact (TUNNEL OXIDE Passivated Contact) solar cell technology based on the selective carrier principle, the cell structure is an N-type silicon substrate cell, a layer of ultrathin silicon Oxide is prepared on the back of the cell, then a layer of doped polysilicon layer is deposited, and the passivation Contact structure is formed by the two, so that the surface recombination and the metal Contact recombination are effectively reduced. After preparing the ultra-thin silicon oxide and the doped polysilicon layer from the back of TOPCon, silicon nitride needs to be deposited for passivating defects in an N-type silicon substrate and the doped polysilicon layer

How to further improve the efficiency of the TOPCon battery is a technical problem to be solved.

Disclosure of Invention

The invention aims to provide a solar cell, a preparation method thereof and a photovoltaic module, which are used for solving the technical problems in the prior art and can further improve the efficiency of a TOPCon cell.

In a first aspect, the present invention provides a solar cell comprising:

a substrate having a front surface and a back surface, the front surface and the back surface being disposed opposite to each other in a thickness direction of the substrate;

a dielectric layer on the back surface;

the back doping layer is positioned on the surface of the dielectric layer;

the n layers of silicon nitride layers are arranged on the back doping layer;

the m layers of the silicon oxynitride layers are arranged on the surface of the outermost layer of the silicon nitride layer;

and the k layer of the silicon oxide layer is arranged on the surface of the outermost silicon oxynitride layer.

The solar cell as described above, preferably, a value of n ranges from 1 to 3, a value of m ranges from 1 to 2, and a value of k ranges from 1.

In the above solar cell, preferably, the value of n is 3, and the value of m is 2.

The solar cell as described above, wherein the total thickness of the m layers of the silicon oxynitride layer is preferably 20 to 30nm, and the total refractive index is preferably 1.75 to 1.9.

A solar cell as described above, wherein preferably, the silicon oxide layer has a thickness of 5 to 10nm and an overall refractive index of 1.6 to 1.75.

In the above solar cell, the thickness of the dielectric layer is preferably 0.85nm to 1.9nm, and the material of the dielectric layer includes at least one of silicon oxide, aluminum oxide, hafnium oxide, silicon nitride, and silicon oxynitride.

The solar cell as described above, wherein the material of the back side doping layer preferably includes doped polysilicon, amorphous silicon or microcrystalline silicon.

The solar cell as described above, wherein preferably, the solar cell further comprises:

the first electrode penetrates through the silicon oxide layer, the silicon oxynitride layer and the silicon nitride layer in sequence and then forms electric contact with the back doped layer;

a front side doping layer on the front surface;

a front side passivation layer positioned on the front side doping layer;

and the second electrode penetrates through the front passivation layer and then forms electric contact with the front doped layer.

In a second aspect, the present application further provides a method for manufacturing a solar cell, which is used for manufacturing the foregoing solar cell, and includes the following steps:

depositing a dielectric layer after polishing the back surface of the substrate;

depositing to form a back doped layer;

depositing 1-3 silicon nitride layers;

depositing 1-2 layers of silicon oxynitride layers;

1 silicon oxide layer was deposited.

In a third aspect, the present application further provides a photovoltaic module, comprising:

the solar cell comprises a cell string and a solar cell, wherein the cell string is formed by connecting the solar cells;

an encapsulation layer for covering a surface of the battery string;

and the cover plate is used for covering the surface of the packaging layer far away from the battery string.

Compared with the prior art, the laminated film structure of the silicon nitride, the silicon oxynitride layer and the silicon oxide layer replaces the traditional silicon nitride layer, so that the solar cell has the advantages of high conversion efficiency, high process compatibility, high double-sided rate and the like, the back surface reflectivity is reduced, and the double-sided rate of the cell is improved.

Drawings

Fig. 1 is a schematic structural diagram of a solar cell provided in an embodiment of the present invention;

fig. 2 is a schematic structural diagram of a photovoltaic module according to an embodiment of the present invention.

Description of the reference numerals:

1-substrate, 2-front surface, 3-back surface, 4-dielectric layer, 5-back surface doping layer, 6-first electrode, 7-silicon nitride layer, 8-silicon oxynitride layer, 9-silicon oxide layer, 10-front surface doping layer, 11-front surface passivation layer, 12-second electrode, 13-battery string, 14-packaging layer and 15-cover plate.

Detailed Description

The embodiments described below with reference to the drawings are illustrative only and should not be construed as limiting the invention.

The TOPCon (Tunnel Oxide passivation Contacts) cell is a solar cell with a passivated contact of a tunneling Oxide layer based on the selective carrier principle. The back surface of the TOPCon cell is usually in a structure formed by combining an ultrathin tunneling silicon oxide layer and a doped polycrystalline silicon layer, so that a passivation contact effect is realized, a metal electrode is not in direct contact with c-Si, the direct contact is facilitated to reduce the recombination of carriers, the separation and collection of the carriers are realized, the efficiency of the TOPCon cell is further improved, and the TOPCon cell is a technical problem to be solved.

In order to further improve the efficiency of the TOPCon cell, as shown in fig. 1, an embodiment of the invention provides a solar cell, which includes a substrate 1, and a dielectric layer 4, a back-doped layer 5, a silicon nitride layer 7, a silicon oxynitride layer 8 and a silicon oxide layer 9 sequentially disposed on the back of the substrate 1 along the irradiation direction of sunlight, wherein:

the substrate 1 has a front surface 2 and a back surface 3, the front surface 2 and the back surface 3 are disposed opposite to each other in a thickness direction of the substrate 1, the front surface 2 is a light receiving surface facing a sunlight irradiation direction, the back surface 3 is a surface opposite to the front surface 2, in the embodiment provided in the present application, the solar cell is a bifacial cell, and the back surface 3 also serves as a light receiving surface. The substrate 1 may be, for example, a crystalline semiconductor including a dopant having a first conductivity type. The crystalline semiconductor may be polycrystalline silicon, single crystalline silicon, or single crystalline-like silicon, a specific type of the crystalline semiconductor is not limited by the embodiment of the present invention, and the first conductive type dopant may be an N-type dopant such As a V-group element including phosphorus (P), arsenic (As), bismuth (Bi), antimony (Sb), or a P-type dopant including a III-group element such As boron (B), aluminum (Al), gallium (Ga), indium (In).

The dielectric layer 4 is located on the back surface 3, and the dielectric layer 4 is used for performing interface passivation on the back surface 3 of the substrate 1, so that the recombination of carriers at the interface is reduced, and the transmission efficiency of the carriers is ensured.

In the embodiments provided herein, the dielectric layer 4 comprises one or more of silicon oxide, aluminum oxide, hafnium oxide, silicon nitride, or silicon oxynitride. The materials have good interface dangling bond passivation effect and tunneling effect, and the thickness of the dielectric layer 4 is 0.85nm-1.9nm. Specifically, the thickness of the dielectric layer 4 is 0.85nm, 0.9nm, 1.0nm, 1.2nm, 1.4nm, 1.6nm, 1.8nm, 1.9nm, or the like, but may be other values within the above range, and is not limited thereto.

The dielectric layer 4 allows many photons to tunnel into the back doping layer 5 and simultaneously blocks few photons from passing through, so that many photons are transversely transported in the back doping layer 5 and collected by the first electrode 6, the dielectric layer 4 and the back doping layer 5 form a tunneling oxide layer passivation contact structure, excellent interface passivation and carrier selective collection can be achieved, carrier recombination is reduced, and photoelectric conversion efficiency of the solar cell is improved. It is noted that the dielectric layer 4 may not in practice have a perfect tunnel barrier, since it may for example contain defects such as pinholes, which may cause other charge carrier transport mechanisms (e.g. drift, diffusion) to dominate over the tunnel effect.

The back doping layer 5 is disposed on the surface of the dielectric layer 4, and in the embodiment provided herein, the back doping layer 5 is formed by doping amorphous silicon, microcrystalline silicon, polycrystalline silicon, etc. with N-type dopants. In the embodiment provided by the present application, the back side doping layer 5 is a doped polysilicon layer, and a first doping element of the doped polysilicon layer is adapted to the first conductive type dopant of the substrate 1; in one possible embodiment, when the substrate 1 is an N-type crystalline silicon substrate 1, the first doping element of the doped polysilicon layer is phosphorus; when the substrate 1 is a P-type crystalline silicon substrate 1, the first doping element of the doped polysilicon layer is boron. The thickness of the back surface doping layer 5 is 20nm to 300nm, and may be, for example, 20nm, 40nm, 50nm, 80nm, 100nm, 120nm, 150nm, 200nm, 220nm, 250nm, or 300nm. Other values within the range are also possible and are not limited herein.

The n-layer silicon nitride layer 7 is arranged on the back doping layer 5, the m-layer silicon oxynitride layer 8 is arranged on the surface of the outermost silicon nitride layer 7, the k-layer silicon oxide layer 9 is arranged on the surface of the outermost silicon oxynitride layer 8, the silicon nitride layer 7, the silicon oxynitride layer 8 and the silicon oxide layer 9 jointly form a multilayer passivation film structure, the back surface 3 of the battery is passivated, H atoms are prevented from overflowing through the silicon oxynitride layer 8 and the silicon oxide layer 9, the H passivation effect is improved, the back reflectivity is reduced, and the double-side rate of the battery piece is improved.

In the embodiment provided by the application, the total thickness of the m layers of silicon oxynitride layers 8 is 20-30nm, the total refractive index is 1.75-1.9, the total thickness of the silicon oxide layers is 5-10nm, and the total refractive index is 1.6-1.75. The light is refracted from low to high to reduce the reflectivity, the photoelectric conversion efficiency is improved, and the silicon oxynitride layer 8 and the silicon oxide layer 9 are more compact than the silicon nitride layer 7, have better and more stable chemical properties, and have an effect of blocking H atoms. And partial H overflows when the silicon nitride is sintered at high temperature, so that passivation is reduced, the silicon oxynitride layer 8 and the silicon oxide layer 9 are required to block, so that the content of H entering the silicon body is higher, and the passivation effect is better.

In the embodiment provided by the application, the value range of n is 1-3, including end values, the silicon nitride layer 7 has high refractive index and good passivation, in a feasible implementation mode, the value of n is 3, namely, the silicon nitride layer 7 is set into three layers to form a composite optical structure design, and the three layers of the silicon nitride layer 7 play a good optical absorption role to increase the absorption rate. Beyond the three silicon nitride layers 7, the efficiency of the cell is not significantly improved, but the cost and the manufacturing difficulty are increased.

In the embodiment provided by the application, the value range of m is 1-2, including the endpoint value, in a feasible implementation mode, the value of m is 2, namely, the silicon oxynitride layer 8 is set into two layers to form a composite optical structure design, the refractive index of the silicon oxynitride layer 8 is greater than that of the silicon oxide layer 9, light can absorb light from the silicon oxide layer to the silicon oxynitride layer 8 to the silicon nitride layer 7, the battery efficiency is improved, if the silicon oxynitride layer 8 is set into more than two layers, no obvious gain is generated, but the cost and the manufacturing difficulty are increased.

In a feasible implementation mode, the thickness of the silicon nitride layer 7 is 15 nm, 30nm and 20nm from bottom to top along the thickness direction of the substrate 1, the refractive index of each layer is 2.25-2.30 nm, 2.15-2.25 nm and 2.05-2.15 nm, the thickness of each layer of the silicon oxynitride layer 8 is 10mm, the refractive index of each layer is 1.75 and 1.90 mm, the refractive index of each layer is increased along the incident light direction, the optical gain is achieved, the short-flow is improved, the H overflow is blocked, and the passivation efficiency is improved.

In the embodiment provided by the present application, the value of k is 1, that is, the silicon oxide layer 9 is set as one layer, so as to avoid that the silicon oxide layer 9 is set too thick, and the too thick slurry is not burnt through, which affects the contact.

The solar cell that this application embodiment provided still includes:

and a first electrode 6 which penetrates through the silicon oxide layer 9, the silicon oxynitride layer 8 and the silicon nitride layer 7 in sequence and is electrically contacted with the back doped layer 5, wherein the material of the first electrode 6 comprises at least one conductive metal material such as silver, aluminum, copper, nickel and the like. As an optional technical solution of the present application, openings may be formed in corresponding positions of the silicon oxide layer 9, the silicon oxynitride layer 8, and the silicon nitride layer 7, so that the first electrode 6 is electrically contacted with the back doped layer 5 after passing through the openings, thereby reducing a contact area between the metal electrode and the back polysilicon layer, further reducing contact resistance, and increasing open-circuit voltage.

A front surface doping layer 10 on the front surface 2, a second doping element of the front surface doping layer 10 being opposite to the first conductivity type dopant of the substrate 1; in a possible embodiment, when the substrate 1 is an N-type crystalline silicon substrate 1, the second doping element of the front-side doping layer 10 is boron; when the substrate 1 is a P-type crystalline silicon substrate 1, the second doping element of the front-doped layer 10 is phosphorus.

The front passivation layer 11 is located on the front doped layer 10, and the front passivation layer 11 can play a role in passivating the front surface 2 of the substrate 1, so that the recombination of carriers at an interface is reduced, the transmission efficiency of the carriers is improved, and the photoelectric conversion efficiency of the cell is further improved. Optionally, the front passivation layer 11 includes a stacked structure of at least one or more of a silicon oxide layer, a silicon nitride layer, an aluminum oxide layer, and a silicon oxynitride layer.

A second electrode 12 penetrating the front passivation layer 11 and making electrical contact with the front doped layer 10, wherein in some embodiments, the material of the second electrode 12 includes at least one conductive metal material such as silver, aluminum, copper, nickel, etc.

Based on the above embodiment, the present application also provides a method for manufacturing a solar cell, which is used for manufacturing the solar cell and includes the following steps:

s101, after polishing the back surface of the substrate 1, depositing a dielectric layer 4, in a feasible embodiment, after alkali polishing the back surface of the battery piece, depositing a 0.85-1.9nm dielectric layer 4 by using LPCVD high-temperature furnace tube equipment, wherein the flow rate of the dielectric layer 4 is 30-40slm, the oxidation time is 400-450S, and the tube closing time is 400-450S.

S102, depositing to form a back doped layer 5, and in a feasible implementation mode, depositing a 60-200nm amorphous silicon layer, wherein SiH of the amorphous silicon layer ₄ The flow is 1200-1600sccm, the deposition time is 1000-2000s, a high-temperature furnace tube is used for amorphous silicon crystallization and doping to form a back doping layer 5, the crystallization temperature is 850-950 ℃, the doping POCl3 is 1000-1500sccm, and the source connection time is 100-300s;

s103, depositing 3 silicon nitride layers 7, specifically, including the following steps.

Step S1031: placing the graphite boat in a PECVD furnace tube at 520-570 ℃, starting a radio frequency source, with the pressure of 240Pa, the power of 22850W, the pulse on-off ratio of 6/120, depositing for 135s, and introducing 2270sccm silane and 9090sccm ammonia gas;

step S1032: starting a radio frequency source, with the pressure of 255Pa, the power of 24800W and the pulse on-off ratio of 7/119, depositing 115s, and introducing 1720sccm silane and 12310sccm ammonia gas;

step S1033: the RF source was turned on at a pressure of 255Pa, at a power of 24800W, at a pulse ON/OFF ratio of 7/119, for a deposition of 215s, and silane at 1350sccm and ammonia at 12720sccm was introduced.

S104, depositing 2 layers of silicon oxynitride layers 8, wherein the ratio of silane to ammonia to laughing gas is 1: (7-15): (45-65), specifically, comprising the steps of:

step S1041: starting a radio frequency source, wherein the pressure is 255Pa, the power is 24000W, the pulse switching ratio is 4/100, depositing for 98s, and introducing 1020sccm silane, 420sccm ammonia gas and 6290sccm laughing gas;

step S1042: and starting a radio frequency source, wherein the pressure is 255Pa, the power is 24000W, the pulse on-off ratio is 4/100, depositing 91s, and introducing 765sccm of silane, 3435sccm of ammonia gas and 7565sccm of laughing gas.

S105, depositing 1 silicon oxide layer 9, wherein the ratio of silane to laughing gas is 1: (10-35), specifically, turning on the radio frequency source, the pressure is 255Pa, the power is 24000W, the pulse on-off ratio is 4/120, depositing for 98s, and introducing 765sccm silane and 9945sccm laughing gas.

Based on the above embodiment, referring to fig. 2, the present application further provides a photovoltaic module, including: a battery string 13, the battery string 13 being formed by connecting the aforementioned solar cells, adjacent battery strings 13 being connected to each other via a conductive tape such as a solder ribbon; an encapsulation layer 14, the encapsulation layer 14 being used to cover the surface of the battery string 13; and the cover plate 15 is used for covering the surface of the packaging layer 14 far away from the battery string 13.

In some embodiments, the number of the battery strings 13 is at least two, and the battery strings 13 are electrically connected in parallel and/or in series.

In some embodiments, the encapsulant layer 14 includes encapsulant layers 14 disposed on the front and back sides of the battery string 13, and the material of the encapsulant layer 14 includes, but is not limited to, EVA, POE, or PET.

In some embodiments, the cover plates 15 include cover plates 15 disposed on the front and back sides of the battery string 13, and the cover plates 15 are selected from materials having good light transmission capacity, including but not limited to glass, plastic, and the like.

The construction, features and functions of the present invention are described in detail in the embodiments illustrated in the drawings, which are only preferred embodiments of the present invention, but the present invention is not limited by the drawings, and all equivalent embodiments modified or changed according to the idea of the present invention should fall within the protection scope of the present invention without departing from the spirit of the present invention covered by the description and the drawings.

Claims (10)

1. A solar cell, comprising:

a substrate having a front surface and a back surface, the front surface and the back surface being disposed opposite to each other in a thickness direction of the substrate;

a dielectric layer on the back surface;

the back doping layer is positioned on the surface of the dielectric layer;

the n layers of silicon nitride layers are arranged on the back doping layer;

the m layers of the silicon oxynitride layers are arranged on the surface of the outermost layer of the silicon nitride layer;

and the k layer of the silicon oxide layer is arranged on the surface of the outermost layer of the silicon oxynitride layer.

2. The solar cell of claim 1, wherein n has a value in a range of 1-3, m has a value in a range of 1-2, and k has a value of 1.

3. The solar cell of claim 2, wherein n has a value of 3 and m has a value of 2.

4. The solar cell according to claim 1, wherein the total thickness of the m layers of the silicon oxynitride layer is 20 to 30nm, and the total refractive index is 1.75 to 1.9.

5. The solar cell of claim 1, wherein the silicon oxide layer has a thickness of 5-10nm and an overall refractive index of 1.6-1.75.

6. The solar cell of claim 1, wherein: the thickness of the dielectric layer is 0.85nm-1.9nm, and the material of the dielectric layer comprises at least one of silicon oxide, aluminum oxide, hafnium oxide, silicon nitride and silicon oxynitride.

7. The solar cell of claim 1, wherein: the material of the back surface doping layer comprises doped polycrystalline silicon, amorphous silicon or microcrystalline silicon.

8. The solar cell of claim 1, wherein: the solar cell further includes:

the first electrode penetrates through the silicon oxide layer, the silicon oxynitride layer and the silicon nitride layer in sequence and then forms electric contact with the back doped layer;

a front side doping layer on the front surface;

a front side passivation layer on the front side doped layer;

and the second electrode penetrates through the front passivation layer and then forms electric contact with the front doped layer.

9. A method for manufacturing a solar cell sheet for manufacturing the solar cell according to any one of claims 1 to 8, comprising the steps of:

depositing a dielectric layer after polishing the back surface of the substrate;

depositing to form a back doped layer;

depositing 1-3 silicon nitride layers;

depositing 1-2 layers of silicon oxynitride layers;

1 silicon oxide layer was deposited.

10. A photovoltaic module, comprising:

a battery string formed by connecting the solar cells according to any one of claims 1 to 8;

an encapsulation layer for covering a surface of the battery string;

and the cover plate is used for covering the surface of the packaging layer far away from the battery string.

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