CN202210533U - Back-contact heterojunction solar cell structure based on N-type silicon wafer - Google Patents

Abstract

The utility model relates to a solar cell, and specifically to a back-contact heterojunction solar cell structure based on an N-type silicon wafer. The back side is divided into an N-type region and a P-type region, wherein the N-type region forms an N+a-si/ia-si/Nc-si/N+c-si heterojunction structure, and the P-type region forms an N+a-si/ia-si/Nc-si/N+c-si/ia-si/Pa-si heterojunction structure, which has a better spectral response, a longer optical path for sunlight to propagate in the cell, and a cell that is much thinner than a conventional crystalline silicon solar cell; all electrodes are printed on the back side of the cell, which avoids the problem of light shading on the front side electrodes of conventional solar cells, and greatly improves the conversion efficiency of the solar cell; the low-temperature sintering process greatly simplifies the production process, reduces production costs, and is suitable for industrialized production.

Description

Back-contact heterojunction solar cell structure based on N-type silicon wafer

technical field

The utility model relates to a solar battery structure, in particular to a back contact heterojunction solar battery structure based on an N-type silicon wafer. the

Background technique

In the 21st century, energy crisis and environmental pollution have become global problems that need to be solved urgently. The development of green energy has become the main method to solve the crisis. Among them, solar cells have become the goal of competing development of countries all over the world because of their cleanliness, safety and renewability. At present, the main development direction of solar cells is to reduce costs and increase efficiency. the

The heterojunction solar cell composed of new amorphous silicon and crystalline silicon has a simple structure and simple process. It combines the advantages of high carrier mobility of crystalline silicon with the advantages of low-temperature chemical vapor deposition of amorphous silicon technology, and has become the leading solar cell in the solar industry. Hotspot development direction. For example, the replacement efficiency of the HIT battery laboratory developed by Japan's Sanyo Group with N-type crystalline silicon as the substrate has exceeded 22%, and the conversion efficiency of industrialized cells has reached 19%. the

The solar cells with the above-mentioned HIT structure have the following problems: the first amorphous silicon film has many defects, which increases the carrier recombination defect density in the film body and affects the collection and transmission of photo-generated current; The light-receiving area is reduced, thereby reducing the short-circuit current and affecting the final conversion efficiency of the solar cell. the

Contents of the invention

The purpose of this utility model is to provide a back-contact heterojunction solar cell structure based on N-type silicon wafers in view of the above-mentioned defects, which will not cause light-induced attenuation of conventional P-type crystalline silicon solar cells; it has better spectrum Response, sunlight travels in the battery with a longer optical path, and the thickness of the battery is greatly thinner than that of conventional crystalline silicon solar cells; all electrodes are printed on the back of the battery, which avoids the problem of shading the front electrodes of conventional solar cells and improves the short-circuit current of solar cells , greatly improving the conversion efficiency of solar cells; the low-temperature sintering process greatly simplifies the production process, reduces production costs, and is suitable for industrial production. the

The technical solution adopted by the utility model is, a back-contact heterojunction solar cell structure based on N-type silicon wafers, which is divided into N-type area and P-type area from the back features, and the N-type area includes sequential stacking from top to bottom Combined light-receiving surface anti-reflection film, N+ a-Si N+ amorphous silicon film, i-a-Si intrinsic amorphous silicon film, N-C-Si N-type crystalline silicon, N+ c-Si N+ crystalline silicon layer, transparent conductive film TCO and The back electrode forms an N+ a-si/ i- a-si/N-c-si/N+c-si heterojunction structure; the P-type region includes an anti-reflection film on the light-receiving surface and an N+ a -Si N+ amorphous silicon film, i-a-Si intrinsic amorphous silicon film, N-C-Si N-type crystalline silicon, N+ c-Si N+ crystalline silicon layer, i-a-Si intrinsic amorphous silicon film, P-a-Si amorphous Silicon film, transparent conductive film TCO and back electrode form N+ a-si/ i- a-si/N-c-si/N+c-si/i-a-si/P-a-si heterojunction structure. the

The anti-reflection film on the light-receiving surface is SiO ₂ , Si ₃ N ₄ , Ta ₂ O ₅ or TiO ₂ , the thickness of the anti-reflection film is 70-90 nm, and the refractive index is 1.5-2.5.

A chemical vapor deposition process is used to form an intrinsic amorphous silicon film on the N-type crystalline silicon and under the N+ crystalline silicon layer in the P-type region, with a thickness of 1-50nm. the

The N-type crystalline silicon is monocrystalline silicon, solar-grade or metal-grade polycrystalline silicon, and strip-shaped silicon, with a thickness of 120-220um and a doping concentration of 1×10 ¹⁵ to 5×10 ¹⁷ /cm ³ .

The N ⁺ -type crystalline silicon layer under the N-type crystalline silicon has a thickness of 0.1-0.5um and a concentration of phosphorus doping of 1×10 ¹⁸ -5×10 ²⁰ /cm ³ .

In the P-type region, a P-a-Si amorphous silicon film is deposited under the intrinsic amorphous silicon film by a chemical vapor deposition process, with a thickness of 1-50 nm. the

Transparent conductive film TCO is an oxide transparent conductive material system, including In ₂ O ₃ , SnO ₂ , ZnO, In ₂ O ₃ :Sn(ITO), In ₂ O ₃ :Mo(IMO), SnO ₂ :Sb(ATO) , SnO ₂ :F(FTO), ZnO:Al(ZnO), ZnO·SnO ₂ , ZnO·In ₂ O ₃ , CdSb ₂ O ₆ , MgIn ₂ O ₄ , In ₄ Sn ₃ O ₁₂ , Zn ₂ In ₂ O _5. CdIn ₂ O ₄ , Cd ₂ SnO ₄ , Zn ₂ SnO ₄ , GaInO ₃ , the thickness of which is 50Nm~900nm.

Described back electrode is Al, Ag, Au, Ni, Cu/Ni, Al/Ni or Ti/Pd/Ag electrode, and its thickness is 50nm～600um. the

The N-type silicon wafer-based back-contact heterojunction solar cell structure of the utility model has the following beneficial effects: first, there will be no light-induced attenuation phenomenon of conventional P-type crystalline silicon solar cells; second, it has better spectral response characteristics, The sunlight travels in the battery with a longer optical path, and the thickness of the battery is much thinner than that of conventional crystalline silicon solar cells; the third is that all electrodes are printed on the back of the battery, which avoids the problem of shading the front electrodes of conventional solar cells and improves the short-circuit current of solar cells , which greatly improves the conversion efficiency of solar cells; the fourth is the low-temperature sintering process, which simplifies the production process of solar cells, reduces production costs, and is suitable for industrial development. the

The back-contact heterojunction solar cell structure based on N-type silicon wafers of the utility model is divided into N-type area and P-type area from the back features, and the N-type area includes light-receiving surface anti-reflection films stacked sequentially from top to bottom , N+ a-Si N+ amorphous silicon film, i-a-Si intrinsic amorphous silicon film, N-C-Si N-type crystalline silicon, N+ c-Si N+ crystalline silicon layer, transparent conductive film TCO and back electrode, forming N+ a- si/ i- a-si/N-c-si/N+c-si heterojunction structure; the P-type region includes an anti-reflection film on the light-receiving surface, N+ a-Si N+ amorphous silicon thin film stacked sequentially from top to bottom , i-a-Si intrinsic amorphous silicon thin film, N-C-Si N-type crystalline silicon, N+ c-Si N+ crystalline silicon layer, i-a-Si intrinsic amorphous silicon thin film, P-a-Si amorphous silicon thin film, transparent conductive thin film TCO And the back electrode, forming N+ a-si/ i- a-si/N-c-si/N+c-si/i-a-si/P-a-si heterojunction structure. The specific functions are as follows:

The transparent conductive film TCO has high light transmittance and electrical conductivity, mainly plays the role of collecting current, and also reflects back the sunlight passing through the battery body to increase the light absorption of the solar battery.

A chemical vapor deposition process is used to fabricate an intrinsic amorphous silicon film on the N-type crystalline silicon and under the N+ crystalline silicon layer in the P-type region, with a thickness of 1-50nm. It mainly serves to reduce the interface defect state and increase the surface passivation effect. the

A layer of P-a-Si amorphous silicon film is deposited on the intrinsic amorphous silicon film by chemical vapor deposition process, with a thickness of 1-50nm. The P-a-si amorphous silicon film is deposited on the i-a-si intrinsic amorphous silicon film layer to form a core structure HIT heterojunction with the N-type crystalline silicon cell. the

The thickness of the N+ type crystalline silicon layer is 0.1-0.5um, and the doping concentration of concentrated phosphorus is 1×10 ¹⁸ ˜5×10 ^20/ cm ³ . The function is to form high and low junctions, increase the open circuit voltage, and at the same time play the role of back passivation.

The anti-reflection film is one of SiO ₂ , Si ₃ N ₄ , Ta ₂ O ₅ , and TiO ₂ , the thickness of the anti-reflection film is 70-90 nm, and the refractive index is 1.5-2.5. Its function is mainly to increase light absorption and reduce the reflection loss of sunlight on the surface of the battery. In addition, the anti-reflection film also has the function of surface passivation.

The N-type silicon wafer back-contact HIT solar cell produced by the above technical scheme has a simple preparation method and can be rapidly industrialized. In addition, its back contact structure has no grid line coverage on the light-receiving surface of the solar cell, which not only increases the light-receiving area of the solar cell, but also simplifies the appearance requirements of the welding process in module production, saves production time and reduces module production costs. the

Description of drawings

Fig. 1 shows the schematic diagram of the battery structure of the present utility model;

Figure 2 is a schematic diagram of the back electrode in Example 1 of the present utility model;

Fig. 3 is a schematic diagram of the technological process of the utility model embodiment 1.

In the figure, 1. Antireflection film; 2. N+ a-Si amorphous silicon thin film; 3. Intrinsic amorphous silicon thin film; 4. N-type crystalline silicon; 5. N+ crystalline silicon layer; 6. p-a-Si amorphous Silicon film; 7. Transparent conductive film TCO; 8. Back electrode; a. N-type silicon wafer detection, cleaning and surface texturing; b. Diffusion of a N+-type heavily doped layer on the lower surface; c. Deposition on the upper and lower surfaces A thin layer of intrinsic amorphous silicon; d. Deposit a thin layer of N+ type amorphous silicon on the upper surface; e. Deposit a layer of p-type amorphous silicon film on the lower surface; f. Prepare silicon nitride on the upper surface by PECVD Anti-reflection coating; g. Use etching slurry to etch to expose the N-type silicon substrate; h. Sputter a layer of TCO conductive layer on the lower surface, and use laser to separate the P area and N area; i. Screen-print electrodes and sinter at low temperature. the

Detailed ways:

The technical scheme of the utility model will be described below in conjunction with the accompanying drawings and examples, but the utility model is not limited thereto.

Example 1

N-type crystalline silicon 4 is selected from N-type single crystal silicon wafers, and the surface of N-type crystalline silicon 4 is pre-cleaned and surface textured by using semiconductor cleaning technology. The thickness of the N-type crystalline silicon 4 used is 200um, the resistivity is 0.5~3Ω.cm, the silicon dioxide layer on the surface of the N-type crystalline silicon 4 is removed with 1~5% hydrofluoric acid, and the concentration is less than 3% NaOH and IPA (isopropanol) mixed liquid at about 80°C to prepare pyramid-shaped suede. Increase the absorption of sunlight, increase the area of the PN junction, and increase the short-circuit current. The subsequent N-type crystalline silicon 4 is cleaned by an acid cleaning process and dried. Put the N-type crystalline silicon 4 after texturing into a diffusion furnace and use (POCl ₃ ) to carry out single-sided heavy phosphorus diffusion at about 850°C, and form a layer of N+ crystalline silicon layer 5 on the lower surface of the N-type crystalline silicon 4. After etching, remove phosphorus silicon glass (PSG), wash with deionized water and dry;

Using the plasma enhanced chemical vapor deposition (PECVD) process, a layer of intrinsic amorphous silicon film 3 is deposited on the upper and lower surfaces of the crystalline silicon after diffusion at 250°C, with a thickness of about 5nm, which has a passivation effect; deposited on the upper surface of the crystalline silicon High-concentration N+ a-Si amorphous silicon film 2 with a thickness of 5-10nm; deposit a layer of P-a-Si amorphous silicon thin layer 6 on the back surface with a thickness of 5-10nm; Silicon nitride light-receiving surface anti-reflection film 1 is grown on the front surface, the thickness is 85nm, and the refractive index is 2.05; its function reduces the reflection loss on the surface of the battery, and the light reflection loss of the solar battery after coating can be reduced to less than 4%; Effective surface passivation and bulk passivation, reducing recombination centers, improving minority carrier lifetime, and increasing photocurrent. Print the corrosive paste on the back of the silicon wafer, etch away the P-a-Si amorphous silicon thin layer 6 and intrinsic amorphous silicon thin film 3 in the printed area, exposing the surface of the N+ crystalline silicon layer 5, and the HIT structure in the unetched area is preserved down. Finally, after ultrasonic cleaning with deionized water, dry. A transparent conductive layer film TCO 7 with a thickness of 30-100 nm is deposited on the back of the silicon wafer by magnetron sputtering process. The P-type area and the N-type area are then divided by laser. The back electrode 8 is formed by screen-printing conductive paste on the N-type area and the P-type area of the back surface, respectively, and sintering at a low temperature. The back of the battery is shown in Figure 2. The electrode printing material used in the N-type area is silver paste; the electrode printing material used in the P-type area is silver paste, silver-aluminum paste, or a structure similar to the silver-aluminum paste on the back of a conventional solar cell.

The electrical performance output parameters of the back-contact heterojunction solar cells based on N-type single crystal silicon wafers prepared in this example: under standard measurement conditions: measurement temperature 25 ^o C, light intensity 1000W/m ² , AM1.5 spectrum test , short circuit current density 42mA/cm ² ; open circuit voltage 683mV, fill factor 79.5%; photoelectric conversion efficiency 21.6%.

Claims (8)

1. back of the body contact heterojunction solar battery structure based on N type silicon chip; Characteristic is divided into N type zone and p type island region territory from the back side; It is characterized in that: N type zone comprises from top to bottom sensitive surface antireflective coating, N+ a-Si N+ amorphous silicon membrane, i-a-Si intrinsic amorphous silicon film, N-C-Si N type crystalline silicon, N+ c-Si N+ crystal silicon layer, transparent conductive film TCO and the back electrode of lamination combination successively, forms N+ a-si/ i-a-si/N-c-si/N+c-si heterojunction structure; The p type island region territory comprises from top to bottom sensitive surface antireflective coating, N+ a-Si N+ amorphous silicon membrane, i-a-Si intrinsic amorphous silicon film, N-C-Si N type crystalline silicon, N+ c-Si N+ crystal silicon layer, i-a-Si intrinsic amorphous silicon film, P-a-Si amorphous silicon membrane, transparent conductive film TCO and the back electrode of lamination combination successively, forms N+ a-si/ i-a-si/N-c-si/N+c-si/i-a-si/P-a-si heterojunction structure.

2. the back of the body contact heterojunction solar battery structure based on N type silicon chip according to claim 1, it is characterized in that: described sensitive surface antireflective coating is SiO2, Si3N4, Ta2O5 or TiO2, and antireflective coating thickness is 70 ~ 90nm, and refractive index is 1.5 ~ 2.5.

3. the back of the body contact heterojunction solar battery structure based on N type silicon chip according to claim 1 is characterized in that: described i-a-Si intrinsic amorphous silicon film thickness is 1 ~ 50nm.

4. the back of the body contact heterojunction solar battery structure based on N type silicon chip according to claim 1; It is characterized in that: described N type crystalline silicon is monocrystalline silicon, solar level or levels of metal polysilicon, banded silicon; Its thickness is 120 ~ 220um, and doping content is 1 * 1015～5 * 1017/cm3.

5. the back of the body contact heterojunction solar battery structure based on N type silicon chip according to claim 1 is characterized in that: the N+ type crystalline silicon layer of described N type crystalline silicon lower floor, its thickness is 0.1 ~ 0.5um.

6. the back of the body contact heterojunction solar battery structure based on N type silicon chip according to claim 1 is characterized in that: in the described p type island region territory, P-a-Si amorphous silicon membrane thickness is 1 ~ 50nm.

7. the back of the body contact heterojunction solar battery structure based on N type silicon chip according to claim 1; It is characterized in that: transparent conductive film TCO is an oxidic transparent electric conducting material system; A kind of among In2O3, SnO2, ZnO, In2O3:Sn (ITO), In2O3:Mo (IMO), SnO2:Sb (ATO), SnO2:F (FTO), ZnO:Al (ZnO), ZnOSnO2, ZnOIn2O3, CdSb2O6, MgIn2O4, In4Sn3O12, Zn2In2O5, CdIn2O4, Cd2SnO4, Zn2SnO4, the GaInO3, its thickness is 50nm ~ 900nm.

8. the back of the body contact heterojunction solar battery structure based on N type silicon chip according to claim 1 is characterized in that: described back electrode is Al, Ag, Au, Ni, Cu/Ni, Al/Ni or Ti/Pd/Ag electrode, and its thickness is 50nm ~ 600um.

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