CN115513335A - N-TOPCon solar cell preparation method and cell - Google Patents
N-TOPCon solar cell preparation method and cell Download PDFInfo
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- 238000002360 preparation method Methods 0.000 title claims abstract description 14
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 claims abstract description 68
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 57
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 57
- 239000010703 silicon Substances 0.000 claims abstract description 57
- 230000005641 tunneling Effects 0.000 claims abstract description 49
- 238000000151 deposition Methods 0.000 claims abstract description 35
- 239000011787 zinc oxide Substances 0.000 claims abstract description 32
- 238000009792 diffusion process Methods 0.000 claims abstract description 27
- 229910052796 boron Inorganic materials 0.000 claims abstract description 22
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims abstract description 20
- 229910017107 AlOx Inorganic materials 0.000 claims abstract description 17
- 238000000034 method Methods 0.000 claims abstract description 17
- 238000007781 pre-processing Methods 0.000 claims abstract description 7
- 238000001465 metallisation Methods 0.000 claims abstract description 4
- 229910007667 ZnOx Inorganic materials 0.000 claims description 38
- 229910021420 polycrystalline silicon Inorganic materials 0.000 claims description 25
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 24
- 238000006243 chemical reaction Methods 0.000 claims description 23
- 238000002161 passivation Methods 0.000 claims description 21
- 239000012153 distilled water Substances 0.000 claims description 14
- 239000002243 precursor Substances 0.000 claims description 12
- 239000011701 zinc Substances 0.000 claims description 12
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 7
- 229910052739 hydrogen Inorganic materials 0.000 claims description 7
- 239000001257 hydrogen Substances 0.000 claims description 7
- 229910052698 phosphorus Inorganic materials 0.000 claims description 6
- 239000011574 phosphorus Substances 0.000 claims description 6
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 5
- 229910052782 aluminium Inorganic materials 0.000 claims description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 4
- 238000000137 annealing Methods 0.000 claims description 3
- 238000002834 transmittance Methods 0.000 abstract description 11
- 239000010408 film Substances 0.000 description 58
- 229910021419 crystalline silicon Inorganic materials 0.000 description 9
- HQWPLXHWEZZGKY-UHFFFAOYSA-N diethylzinc Chemical compound CC[Zn]CC HQWPLXHWEZZGKY-UHFFFAOYSA-N 0.000 description 8
- 229920005591 polysilicon Polymers 0.000 description 7
- 239000010409 thin film Substances 0.000 description 6
- 238000005530 etching Methods 0.000 description 5
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 4
- 238000004140 cleaning Methods 0.000 description 4
- 229910000040 hydrogen fluoride Inorganic materials 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 239000004065 semiconductor Substances 0.000 description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 3
- 239000003513 alkali Substances 0.000 description 3
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- 238000005215 recombination Methods 0.000 description 3
- 229910052814 silicon oxide Inorganic materials 0.000 description 3
- 229910004205 SiNX Inorganic materials 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
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- 230000005540 biological transmission Effects 0.000 description 1
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- 239000012535 impurity Substances 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 238000000608 laser ablation Methods 0.000 description 1
- 238000004518 low pressure chemical vapour deposition Methods 0.000 description 1
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- 238000009740 moulding (composite fabrication) Methods 0.000 description 1
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- RLOWWWKZYUNIDI-UHFFFAOYSA-N phosphinic chloride Chemical compound ClP=O RLOWWWKZYUNIDI-UHFFFAOYSA-N 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
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Abstract
The invention relates to a preparation method of an N-TOPCon solar cell and the solar cell, wherein the method comprises the following steps: s1, preprocessing an N-type silicon wafer; s2, depositing a front tunneling oxide layer on the boron diffusion layer of the N-type silicon wafer, wherein the front tunneling oxide layer is made of AlOx; s3, depositing a first doping layer on the tunneling oxide layer on the front surface of the N-type silicon wafer, wherein the first doping layer is an aluminum-doped zinc oxide film; s4, depositing a second doping layer on the first doping layer, wherein the second doping layer is a hydrogen-doped zinc oxide film; s5, depositing a third doping layer on the second doping layer, wherein the third doping layer is an aluminum-doped zinc oxide film; and S6, carrying out metallization treatment on the front surface and the back surface of the N-type silicon wafer. The preparation method provided by the invention realizes low resistivity and high light transmittance of the film, reduces tunneling resistance, and improves FF of the solar cell; the process is simple; the battery has higher open-circuit voltage, short-circuit current and battery efficiency.
Description
Technical Field
The invention particularly relates to a preparation method of an N-TOPCon solar cell and the cell.
Background
TOPCon (Tunnel Oxide Passivated Contact) is a tunneling Oxide layer passivation Contact solar cell technology based on the selective carrier principle. A layer of ultrathin silicon oxide is prepared on the back of the cell, then a doped silicon thin layer is deposited, and the ultrathin silicon oxide and the doped silicon thin layer form a passivation contact structure together, so that surface recombination and metal contact recombination are effectively reduced. However, since the doped silicon thin layer is mainly polysilicon, which has a larger optical absorption coefficient than crystalline silicon, the passivation contact structure is generally applied to the back surface of the solar cell at present. If the TOPCon structure is applied to the front side of the solar cell, light irradiated to the front side of the crystalline silicon solar cell is excessively absorbed in the layer of polycrystalline silicon thin film, so that the absorption of the light by the crystalline silicon substrate of the absorption layer is remarkably reduced.
When TOPCon is applied to the front side of a solar cell, in order to eliminate the parasitic absorption of light, a local passivation contact/emitter structure is usually adopted, i.e. a tunneling silicon oxide and polysilicon thin film is deposited only in the metal grid line region, and is not deposited in other regions. At present, a local tunneling oxidation passivation layer and a local polycrystalline silicon layer are arranged on the surface of a silicon substrate in a mask or laser ablation mode, and a front metal electrode is prepared in the area where the tunneling oxidation passivation layer and the polycrystalline silicon layer are located through a screen printing technology.
Therefore, many researchers are now looking for alternatives to doped polysilicon thin films that can be used on the front side of solar cells that must satisfy the following conditions:
1. has good surface passivation effect to avoid surface recombination;
2. has high light transmission, namely, low light absorptivity;
3. lower contact resistance;
4. the preparation method is simple, has no environmental pollution and is easy to obtain in nature.
Disclosure of Invention
The invention aims to provide an improved N-TOPCon solar cell and a preparation method thereof, which can reduce tunneling resistance and improve FF of the solar cell.
In order to achieve the purpose, the invention adopts a technical scheme that:
a preparation method of an N-TOPCon solar cell comprises the following steps:
s1, preprocessing an N-type silicon wafer, depositing a boron diffusion layer on the front surface of the N-type silicon wafer after preprocessing, and sequentially depositing a back tunneling oxide layer, a phosphorus-doped polycrystalline silicon layer and a passivation anti-reflection layer on the back surface of the N-type silicon wafer;
s2, depositing a front tunneling oxide layer on a boron diffusion layer of the N-type silicon wafer, wherein the front tunneling oxide layer is made of AlOx;
s3, depositing a first doping layer on the tunneling oxide layer on the front surface of the N-type silicon wafer, wherein the first doping layer is an aluminum-doped zinc oxide film;
s4, depositing a second doping layer on the first doping layer, wherein the second doping layer is a hydrogen-doped zinc oxide film;
s5, depositing a third doping layer on the second doping layer, wherein the third doping layer is an aluminum-doped zinc oxide film;
and S6, carrying out metallization treatment on the front surface and the back surface of the N-type silicon wafer.
Preferably, in step S3, when depositing the first doping layer:
s31, adopting distilled water and Zn (C) 2 H 5 ) 2 Reacting the precursor to obtain a ZnOx film at the reaction temperature of 180-250 ℃;
s32, adopting distilled water and Al (CH) 3 ) 3 The reaction is carried out, an aluminum-doped zinc oxide film is generated on the surface of the ZnOx film, and the reaction temperature is controlled to be 150-200 ℃.
Preferably, in step S4, when depositing the second doping layer:
s41, distilled water and Zn (C) are adopted 2 H 5 ) 2 Reacting the precursor to obtain a ZnOx film at the reaction temperature of 180-250 ℃;
and S42, introducing hydrogen to enable the hydrogen to be adsorbed on the ZnOx film, so as to obtain the hydrogen-doped zinc oxide film.
Preferably, in step S5, when depositing the third doping layer:
s51, adopting distilled water and Zn (C) 2 H 5 ) 2 Reacting the precursor to obtain a ZnOx film, wherein the reaction temperature is 180-250 ℃;
s52, adopting distilled water and Al (CH) 3 ) 3 Reaction is carried out, an aluminum-doped zinc oxide film is generated on the surface of the ZnOx film, and the reaction temperature is controlled to be 150-200 ℃.
Preferably, in step S3, the content of aluminum in the first doped layer is 0.1 to 6.9at%; in step S5, the content of aluminum in the third doped layer is 0.1 to 6.9at%.
Preferably, in step S2, when depositing the front tunneling oxide layer: using distilled water and Al (CH) 3 ) 3 As a precursor.
Preferably, the thickness of the third doped layer is greater than the thickness of the first doped layer.
Preferably, the thickness of the first doping layer is 10-20nm; the thickness of the second doped layer is 55-70nm; the thickness of the third doping layer is 20-30nm; the thickness of the front tunneling oxide layer is 1-3nm.
Preferably, in step S1, the preprocessing includes:
s11, double-sided texturing;
s12, boron diffusion;
s13, removing the boron diffusion layer and the BSG layer which are wound and expanded on the back and the side of the N-type silicon wafer;
s14, growing a tunneling oxide layer and an intrinsic polycrystalline silicon layer on the front side and the back side of the N-type silicon wafer, performing phosphorus diffusion on the front side and the back side of the N-type silicon wafer, and annealing to form a phosphorus-doped polycrystalline silicon layer and PSG on the front side and the back side;
s15, removing the PSG on the front surface and the side surface of the N-type silicon wafer and the phosphorus-doped polycrystalline silicon layer on the front surface.
The other technical scheme adopted by the invention is as follows:
the N-TOPCon solar cell prepared by the preparation method of the N-TOPCon solar cell.
Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages:
according to the preparation method of the N-TOPCon solar cell, the front tunneling oxide layer, the first doping layer, the second doping layer and the third doping layer are deposited on the front surface, so that the low resistivity and the high light transmittance of the film are realized, the tunneling resistance is reduced, and the FF of the solar cell is improved; the process is simple and suitable for large-scale production; the solar cell prepared by the N-TOPCon solar cell preparation method has higher open-circuit voltage, short-circuit current and cell efficiency.
Drawings
FIG. 1 is a schematic structural diagram of an N-TOPCon solar cell of the present invention.
Reference numerals are as follows:
the solar cell comprises a 1-N type silicon chip, a 2-boron diffusion layer, a 3-front tunneling oxide layer, a 4-first doping layer, a 5-second doping layer, a 6-third doping layer, a 7-back tunneling oxide layer, an 8-phosphorus doped polycrystalline silicon layer, a 9-passivation antireflection layer, a 10-front electrode and a 11-back electrode.
Detailed Description
The invention will be further described with reference to examples of embodiments shown in the drawings to which the invention is attached.
A preparation method of an N-TOPCon solar cell comprises the following steps:
s1, pretreating an N-type silicon wafer 1, and after pretreatment, depositing a boron diffusion layer 2 on the front surface of the N-type silicon wafer 1, and sequentially depositing a back tunneling oxide layer 7, a phosphorus-doped polycrystalline silicon layer 8 and a passivation anti-reflection layer 9 on the back surface of the N-type silicon wafer 1;
the pretreatment specifically comprises the following steps:
s11, double-sided texturing: the method comprises the following steps of immersing an original N-type silicon wafer 1 into KOH or NaOH solution with the mass fraction of 1-3% at the temperature of 60-85 ℃ by adopting a conventional texturing process to carry out double-sided texturing, wherein the control time of the texturing is 20-30 min;
s12, boron diffusion: loading the textured silicon wafer obtained after double-sided texturing into a tubular low-pressure boron diffusion furnace tube to complete the front surface boron diffusion doping process, wherein a boron diffusion source adopts BCl 3 The diffusion temperature is 900-1100 ℃, the diffusion time is 2-3 hours, the diffusion sheet resistance is 150-180 omega/sq, and the junction depth is 0.5-1 um;
s13, removing the boron diffusion layer 2 and the BSG layer around the back surface and the side surface of the N-type silicon wafer 1, and specifically comprising the following steps: firstly, carrying out single-sided HF cleaning on an N-type silicon wafer 1 by using a chain type etching machine, removing BSG layers on the back surface and the side surface of the N-type silicon wafer 1, reserving the BSG layer on the front surface of the N-type silicon wafer 1, then carrying out alkali polishing on the back surface of the N-type silicon wafer 1 by using a groove type etching machine, and generally carrying out polishing treatment on the back surface by using a mixed solution of KOH and an additive, so that on one hand, a boron doped layer wound and expanded to the back surface in a boron diffusion process is removed, the front surface and the back surface of the boron doped layer are insulated, and on the other hand, the polished surface is beneficial to depositing a more uniform tunneling oxide layer and a polysilicon layer;
s14, growing tunneling oxide layers and intrinsic polycrystalline silicon layers on the front side and the back side of the silicon wafer by adopting LPCVD equipment at the temperature of 400-550 ℃; loading the silicon wafer into a tube type phosphorus diffusion furnace tube by using POCl 3 Performing phosphorus diffusion on the front and back surfaces of the silicon wafer by diffusion and annealing, and forming phosphorus-doped polysilicon layer 8 and PSG on the front and back surfaces, wherein the tunneling oxide layer (SiOx) has a thickness of 1-2nm and phosphorus doping concentration of 0.9 × 10 21 –3*10 21 /cm 3 ；
S15, removing the PSG on the front surface and the side surface of the N-type silicon wafer 1, the phosphorus-doped polycrystalline silicon layer 8 on the front surface and the tunneling oxide layer (made of SiOx) on the front surface, and specifically comprising the following steps: firstly, carrying out single-sided HF (hydrogen fluoride) cleaning on an N-type silicon chip 1 by using a chain type etching machine table, removing a PSG layer on the front side of the N-type silicon chip 1, reserving the PSG layer on the back side of the N-type silicon chip 1, then carrying out alkali cleaning on the front side of the N-type silicon chip 1 by using a groove type etching machine table, generally removing a polycrystalline silicon layer on the front side by using a mixed solution of KOH and an additive, wherein the polycrystalline silicon layer on the back side basically does not react with an alkali solution because the PSG exists on the back side, and then carrying out HF cleaning on the N-type silicon chip 1 by using the groove type etching machine table to remove a tunneling oxide layer (made of SiOx) and BSG on the front side and PSG on the back side;
and S16, plating a passivation anti-reflection layer 9 on the back surface, wherein the passivation anti-reflection layer 9 can be made of SiNx, and can improve the passivation property and the light absorption property of the back surface.
Next, steps S2, S3, and S4 are performed in an ALD furnace, where ALD is a chemical vapor deposition technique, ALD reacts by alternately pulsing reactant gases into a reaction chamber while the surface reactions occurring in ALD are self-limiting, growing the film layer by layer, and when the surface is saturated, the surface reactions will not increase with time, so that the film grown in each cycle is only one monoatomic layer, and the thickness increase remains constant. The cycle number referred to below refers to the number of grown atomic layers.
Specifically, the method comprises the following steps:
s2, depositing a front tunneling oxide layer on the boron diffusion layer 2 of the N-type silicon wafer 1, wherein the front tunneling oxide layer is made of AlOx, and the thickness of the front tunneling oxide layer is 1-3nm.
When depositing the front tunneling oxide layer: using DI H 2 O (distilled water) and Al (CH) 3 ) 3 (TMA) is used as a precursor, the reaction temperature is controlled to be 150-200 ℃, and the thickness of the front tunneling oxide layer is 0.05nm-0.12 nm/period.
The front side tunnel oxide (AlOx) has a high negative fixed charge density Qf = -5 x 10^12q/cm ^2 to-5 x 10^13q/cm ^2, and the high density of negative fixed charges on the interface results in the formation of holes on the c-Si/AlOx interface, similar to a diffused p-n junction, in the inversion layer, the conductivity of the holes is much higher than that of the electrons. Under the condition that the AlOx thin film is thin, electrons in a ZnO conduction band tunnel through the combination of holes in the AlOx thin film and a Si valence band to generate tunneling current, and a hole selective contact structure is formed.
Besides surface passivation and selectivity of passivation contact to holes, the front tunneling oxide layer (AlOx) is used as a dielectric medium and bears a large amount of energy band distortion, so that a ZnO conduction band is aligned with a valence band of c-Si, the whole c-Si/AlOx/doped ZnO structure forms a tunneling diode structure, tunneling resistance is reduced, and FF of a solar cell is improved.
And S3, depositing a first doping layer 4 on the tunneling oxide layer on the front surface of the N-type silicon wafer 1, wherein the first doping layer 4 is an aluminum-doped zinc oxide film, and the thickness of the first doping layer 4 is 10-20nm.
When depositing the first doping layer 4:
1) Firstly, introducing a precursor Zn (C) into ALD 2 H 5 ) 2 (DEZ) and then introducing DI water (distilled water) into the ALD, the DI water and Zn (C) adsorbed on the surface of the silicon wafer 2 H 5 ) 2 (DEZ) reacting to generate a single atomic layer of ZnOx, and repeating the previous operation steps for m times to obtain a ZnOx film with m layers, wherein m can be 30-50 times, the reaction temperature is controlled at 180-250 ℃, and the thickness of one ZnOx atomic layer is 0.15-0.25 nm/cycle;
2) Then Al (CH) is introduced into the ALD 3 ) 3 Introducing DI water, DI water and Al (CH) 3 ) 3 A reaction is carried out to generate a monoatomic layer of the AlOx film on the surface of the ZnOx film, wherein the cycle number of the AlOx film is 1, and the reaction temperature is controlled to be 150-200 ℃;
repeating the steps 1) and 2), generally repeating the steps 1) and 2) as a cycle, firstly performing the step 1) and then performing the step 2)) for 3-4 times, and obtaining the first doping layer 4 with the thickness of 10-20nm, wherein the doping content of Al in the zinc oxide film is 0.1-6.9at%.
S4, depositing a second doping layer 5 on the first doping layer 4, wherein the second doping layer 5 is a hydrogen-doped zinc oxide film, and the thickness of the second doping layer 5 is 55-70nm;
deposition of the second doped layer 5:
1) Firstly, introducing a precursor Zn (C) into ALD 2 H 5 ) 2 (DEZ, diethyl zinc), then introducing DI water to ALD, the DI water and Zn (C) adsorbed on the surface of the silicon wafer 2 H 5 ) 2 (DEZ) reacting to generate a single atomic layer of ZnOx, and repeating the previous operation steps for m times to obtain m layers of ZnOx films, wherein m can be 25-45 times, the reaction temperature is controlled at 180-250 ℃, and the thickness of one ZnOx atomic layer is 0.15-0.25 nm/cycle (m is 1) generally;
2) Then, introducing hydrogen into ALD to enable the hydrogen to be adsorbed on the surface of the ZnOx film;
3) Repeating the steps 1) and 2) (step 1) and step 2) as a cycle, firstly performing step 1) and then performing step 2)), and generally repeating the steps for about 7 to 12 times to obtain the hydrogen-doped zinc oxide film with the thickness of 55 to 70nm;
s5, depositing a third doping layer 6 on the second doping layer 5, wherein the third doping layer 6 is an aluminum-doped zinc oxide film;
deposition of the third doped layer 6:
1) Firstly, introducing a precursor Zn (C) into ALD 2 H 5 ) 2 (DEZ, diethyl zinc) and then DI water (distilled water) with Zn (C) adsorbed on the wafer surface was introduced into ALD 2 H 5 ) 2 (DEZ) reacting to generate a single atomic layer of ZnOx, and repeatedly cycling the previous operation steps for m times to obtain m layers of ZnOx films, wherein m can be 30-50 times, the reaction temperature is controlled to be 180-250 ℃, and the thickness of one ZnOx atomic layer is 0.15-0.25 nm/cycle generally;
2) Then Al (CH) is introduced into the ALD 3 ) 3 Introducing DI water, DI water and Al (CH) 3 ) 3 A reaction is carried out to generate a monoatomic layer of the AlOx film on the surface of the ZnOx film, wherein the cycle number of the AlOx film is 1, and the reaction temperature is controlled to be 150-200 ℃;
repeating the steps 1) and 2), generally repeating the steps 1) and 2) as a cycle, firstly performing the step 1) and then performing the step 2)) for 3-4 times, and obtaining the third doped layer 6 with the thickness of 20-30nm, wherein the doping content of Al in the zinc oxide film is 0.1-6.9at%.
And S6, performing metallization treatment on the front surface and the back surface of the N-type silicon wafer 1 in a screen printing, electroplating or laser transfer mode, wherein the front surface of the N-type silicon wafer 1 is provided with a front electrode 10, and the back surface of the N-type silicon wafer 1 is provided with a back electrode 11.
In this example, the zinc oxide film can replace the existing doped polysilicon film, specifically:
1. zinc oxide (ZnO) is a group II-VI wide bandgap oxide semiconductor material. The zinc oxide film material only absorbs light with the wavelength less than 368nm, so that the transmittance of the zinc oxide (ZnO) film light exceeds 90% in a visible light region;
2. the refractive index of zinc oxide at 620nm is about 2, and the thickness of zinc oxide is controlled within the range of 60nm-80nm, and the zinc oxide can be used as an excellent anti-reflection coating of a solar cell
3. Zinc oxide (ZnO) can increase its conductivity by doping group III elements (i.e., znO: X, where X = Al, B, ga, in), and is an excellent transparent conductive film that can reduce the lateral transfer resistance of a solar cell.
It is known that the back tunneling oxide passivation contact structure of the currently mass-produced N-TOPCon cell is an electron selective contact structure, and therefore, in order to deposit the tunneling oxide passivation contact structure on the front side, the passivation contact structure should be a hole selective contact structure. In the embodiment, a front hole selective contact structure is formed by adopting a c-Si/AlOx/doped ZnOx laminated film (superposition of a first doped layer, a second doped layer and a third doped layer).
Characteristics of the first doped layer 4: the film is a key layer of a hole selective structure, wherein a c-Si/AlOx/Al doped ZnOx film structure forms a structure of a tunnel diode, the structure can greatly reduce tunnel resistance and improve the FF of a solar cell, and the doping amount of Al in the ZnOx film in the layer of structure is very important for forming the structure of the tunnel diode, because only the ZnOx film heavily doped with Al can form a degenerate semiconductor, so that the degenerate semiconductor can have the possibility of overlapping holes and electrons in c-Si at the same energy level, and the structure of the tunnel diode is formed. Therefore, the layer is required to be a heavily doped ZnOx film; however, the light transmittance of the ZnOx film is seriously influenced by heavily doped Al, so that the influence of the heavy doping on the light transmittance of the film is reduced by thinning the ZnOx film.
Characteristics of the second doped layer 5: the thickness of this rete is great, and the luminousness is high while the resistivity is low: although ZnOx is a semiconductor material, its resistivity is very high without impurity doping, and there are two main decisions to obtain a lower resistivity: 1) The higher the doping concentration is, the higher the carrier concentration is, and the lower the resistivity is, but the doping concentration affects the light transmittance; 2) Is the mobility of carriers, the higher the mobility, the lower the resistivity. The second doping layer 5 has high carrier mobility, and since hydrogen is doped, the influence on the light transmittance is not great, and the film layer not only does not influence the light transmittance problem, but also can improve the carrier mobility.
Characteristics of the third doped layer 6: the second doping layer 5 is a hydrogen-doped ZnOx film, if the film is directly contacted with the outermost metal electrode, the contact resistance is larger, the electrical property of the battery is greatly influenced, but the third doping layer 6 is deposited on the second doping layer 5, the contact resistance of the ZnOx film heavily doped with Al can be reduced, and the characteristics of the third doping layer 6 are the same as those of the first doping layer 4.
In this example, the first doped layer 4, the second doped layer 5, and the third doped layer 6 were provided to prepare a doped zinc oxide thin film having low resistivity and high light transmittance. The hydrogen-doped ZnOx film is not directly used instead of the Al-doped ZnOx film because although the mobility of the hydrogen-doped ZnOx film is high, its resistivity is higher compared to the Al-doped ZnOx film. Therefore, the mode of overlapping three layers of films is adopted to realize the low resistivity and high light transmittance of the film.
In this example, the thickness of the third doped layer 6 is greater than the thickness of the first doped layer 4, and if the thickness of the first doped layer 4 is greater, the transmittance of light is affected.
In another embodiment of the present invention, an N-TOPCon solar cell prepared by an N-TOPCon solar cell preparation method is provided, referring to fig. 1, a boron diffusion layer 2, a front tunneling oxide layer 3, a first doping layer 4, a second doping layer 5, a third doping layer 6 and a front electrode 10 are sequentially disposed on a front surface of an N-type silicon wafer 1, and a back tunneling oxide layer 7, a phosphorus-doped polysilicon layer 8 (Poly-Si (phosphorus-doped)), a passivation anti-reflection layer 9 and a back electrode 11 are sequentially disposed on a back surface of the N-type silicon wafer 1, wherein the front tunneling oxide layer 3 is made of AlOx, the first doping layer 4 is an aluminum-doped zinc oxide film, the second doping layer 5 is a hydrogen-doped zinc oxide film, and the third doping layer 6 is an aluminum-doped zinc oxide film; the back tunneling oxide layer 7 is made of SiOx, and the passivation anti-reflection layer 9 is SiNx.
The performance of the N-TOPCon solar cell of this example was compared to existing N-TOPCon solar cells, see Table 1:
TABLE 1 comparison of the performance of the N-TOPCon solar cell of the present example with that of a conventional N-TOPCon solar cell
As seen from the table, the TOPCon cell of this example has improved Uoc, isc, FF and Eta compared to the performance of the conventional N-TOPCon solar cell.
The above embodiments are only for illustrating the technical idea and features of the present invention, and the purpose of the present invention is to enable those skilled in the art to understand the content of the present invention and implement the present invention, and not to limit the protection scope of the present invention by this means. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
Claims (10)
1. A preparation method of an N-TOPCon solar cell is characterized by comprising the following steps:
s1, preprocessing an N-type silicon wafer, depositing a boron diffusion layer on the front surface of the N-type silicon wafer after preprocessing, and sequentially depositing a back tunneling oxide layer, a phosphorus-doped polycrystalline silicon layer and a passivation anti-reflection layer on the back surface of the N-type silicon wafer;
s2, depositing a front tunneling oxide layer on a boron diffusion layer of the N-type silicon wafer, wherein the front tunneling oxide layer is made of AlOx;
s3, depositing a first doping layer on the tunneling oxide layer on the front surface of the N-type silicon wafer, wherein the first doping layer is an aluminum-doped zinc oxide film;
s4, depositing a second doping layer on the first doping layer, wherein the second doping layer is a hydrogen-doped zinc oxide film;
s5, depositing a third doping layer on the second doping layer, wherein the third doping layer is an aluminum-doped zinc oxide film;
and S6, carrying out metallization treatment on the front surface and the back surface of the N-type silicon wafer.
2. The method of claim 1, wherein in step S3, when depositing the first doped layer:
s31, adopting distilled water and Zn (C) 2 H 5 ) 2 Reacting the precursor to obtain a ZnOx film, wherein the reaction temperature is 180-250 ℃;
s32, adopting distilled water and Al (CH) 3 ) 3 The reaction is carried out, an aluminum-doped zinc oxide film is generated on the surface of the ZnOx film, and the reaction temperature is controlled to be 150-200 ℃.
3. The method of claim 1, wherein in step S4, when depositing the second doping layer:
s41, distilled water and Zn (C) are adopted 2 H 5 ) 2 Reacting the precursor to obtain a ZnOx film, wherein the reaction temperature is 180-250 ℃;
and S42, introducing hydrogen to enable the hydrogen to be adsorbed on the ZnOx film, so as to obtain the hydrogen-doped zinc oxide film.
4. The method of claim 1, wherein in step S5, when depositing the third doped layer:
s51, adopting distilled water and Zn (C) 2 H 5 ) 2 Reacting the precursor to obtain a ZnOx film at the reaction temperature of 180-250 ℃;
s52, adopting distilled water and Al (CH) 3 ) 3 Reaction is carried out, an aluminum-doped zinc oxide film is generated on the surface of the ZnOx film, and the reaction temperature is controlled to be 150-200 ℃.
5. The method of claim 1, wherein in step S3, the aluminum content in the first doped layer is 0.1-6.9at%; in step S5, the content of aluminum in the third doped layer is 0.1 to 6.9at%.
6. The method as claimed in claim 1, wherein in step S2, when depositing the front tunneling oxide layer: by usingDistilled water and Al (CH) 3 ) 3 As a precursor.
7. The method of claim 1, wherein the third doped layer has a thickness greater than a thickness of the first doped layer.
8. The method of claim 7, wherein the first doped layer has a thickness of 10-20nm; the thickness of the second doped layer is 55-70nm; the thickness of the third doping layer is 20-30nm; the thickness of the front tunneling oxide layer is 1-3nm.
9. The method of claim 1, wherein the pre-processing step S1 comprises:
s11, double-sided texturing;
s12, boron diffusion;
s13, removing the boron diffusion layer and the BSG layer which are wound and expanded on the back and the side of the N-type silicon wafer;
s14, growing a tunneling oxide layer and an intrinsic polycrystalline silicon layer on the front side and the back side of the N-type silicon wafer, performing phosphorus diffusion on the front side and the back side of the N-type silicon wafer, annealing, and forming a phosphorus-doped polycrystalline silicon layer and PSG on the front side and the back side;
s15, removing the PSG on the front surface and the side surface of the N-type silicon wafer and the phosphorus-doped polycrystalline silicon layer on the front surface.
10. A N-TOPCon solar cell prepared by the method of preparing a N-TOPCon solar cell of any one of claims 1-9.
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