CN111416002A - Silicon nitride film layer on back of battery, PERC battery and preparation method - Google Patents

Silicon nitride film layer on back of battery, PERC battery and preparation method Download PDF

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CN111416002A
CN111416002A CN202010329604.6A CN202010329604A CN111416002A CN 111416002 A CN111416002 A CN 111416002A CN 202010329604 A CN202010329604 A CN 202010329604A CN 111416002 A CN111416002 A CN 111416002A
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film layer
silicon nitride
layer
nitride film
battery
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朱浩
万柳斌
吴朋朋
张基勇
蒋柱
方雯
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Tongwei Solar Hefei Co Ltd
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Tongwei Solar Hefei Co Ltd
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Abstract

The invention discloses a silicon nitride film layer on the back of a battery, a PERC battery and a preparation method, and belongs to the field of manufacturing of single crystal PERC batteries. The invention provides a PERC battery, aiming at the problems of low battery back film reflectivity, low battery conversion efficiency, high back film manufacturing process temperature requirement and high energy consumption cost in the prior art, the battery comprises a front silicon nitride film layer, a back aluminum oxide film layer and a back silicon nitride film layer, wherein the back silicon nitride film layer is of a five-layer structure, the back aluminum oxide film layer is deposited firstly, the front silicon nitride film layer is deposited secondly, and the back silicon nitride film layer is deposited finally.

Description

Silicon nitride film layer on back of battery, PERC battery and preparation method
Technical Field
The invention relates to the field of manufacturing of single crystal PERC batteries, in particular to a battery back silicon nitride film layer, a PERC battery and a preparation method.
Background
The mainstream technology of crystalline silicon solar cells is perc (passivated Emitter reader cell) -Emitter and back passivated cell technology, which increases the conversion efficiency by adding a dielectric passivation layer on the back side of the cell. The passivation technology is implemented on the back of the battery, so that the internal back reflection of light on a silicon substrate is enhanced, the back recombination is reduced, the potential gradient of a P-N junction is maximally spanned, electrons flow more stably, and the electron recombination is reduced, so that the efficiency of the PERC battery is effectively improved.
The back of the single crystal PREC battery is covered by aluminum oxide and silicon nitride, and the aluminum oxide passivation layer deposited on the silicon substrate through the back film is thin, so that the silicon nitride needs to be deposited on the aluminum oxide film for protection, the reflectivity of the back is increased, and a better passivation surface is obtained, so that the long-wave response effect is improved, the Isc/Uoc is improved, and the conversion efficiency of the battery is improved.
The good and bad film forming quality of the back coating film has important influence on the passivation effect of the back surface of the cell and the protection of the aluminum oxide, in the process of depositing the silicon nitride by the tubular PECVD, the hydroxyl in the aluminum oxide film is decomposed along with the rise of the temperature, the H content in the film is reduced, the surface passivation effect of the cell is weakened, the effective minority carrier lifetime is reduced, and the crystallization degree of the film can reach the best by selecting the proper growth temperature. The back film in the prior art is mainly a single-layer film or a three-layer film, the back reflection effect is a bottleneck, short-circuit current cannot be removed, and meanwhile, the process temperature of the back film is about 530 ℃, so that the energy consumption is large and the cost is high.
The Chinese patent application, application number CN 201910067978.2, published 2019, 5, 21 and discloses a back side anti-reflection passive film of a double-sided PERC battery with anti-PID, a double-sided PERC battery and a preparation method thereof, wherein the back side anti-reflection passive film comprises a SiO2 layer; an aluminum oxide layer in contact with the SiO2 layer; the n layer SiNx is in contact with the aluminum oxide layer, wherein x is more than or equal to 1 and less than or equal to 1.5; the refractive index of the n-layer SiNx is in a descending trend from inside to outside; the thickness of the n layers of SiNx is increased; n is a positive integer. According to the invention, the SiO2 layer and the n-layer SiNx layer are arranged on the back surface of the silicon wafer, so that the refractive index of the n-layer SiNx layer is in a descending trend; the thickness of the n-layer SiNx is increased, so that the passivation film has a good PID (potential induced degradation) resistance effect. Under the test conditions of-1500V, 85% humidity and 85 ℃ of the double-sided PERC battery, the attenuation ratio of the front side is 0.34% and the attenuation ratio of the back side is 0.66% after 96 hours; the front attenuation ratio is 1.65% after 192h, the back attenuation ratio is 2.10%, the silicon nitrogen ratio of the invention is gradually reduced, namely the refractive index of the film layer is gradually reduced from the inner side to the outer side from the silicon substrate layer, the film layer thickness is gradually increased, and the film layer has relatively poor response matching to wavelength.
Disclosure of Invention
1. Technical problem to be solved
The invention provides a silicon nitride film layer on the back of a battery, a PERC battery and a preparation method, aiming at the problems of low battery back film reflectivity, low battery conversion efficiency, high temperature requirement of a back film manufacturing process and high energy consumption cost in the prior art.
2. Technical scheme
The purpose of the invention is realized by the following technical scheme.
A silicon nitride film layer on the back of a battery comprises a five-layer structure, wherein the thickness of the five-layer silicon nitride film layer on the back is α 1, α, α 03, α and α from inside to outside in sequence, the thickness of the five-layer silicon nitride film layer from α 31 to α is α not less than α not less than α 1 not less than α not less than α or α not less than α 3 not less than α 1 not less than α 4, the refractive index of the five-layer silicon nitride film layer on the back is α, α 04 and α from inside to outside in sequence, the refractive index of the five-layer silicon nitride film layer on the back of the battery is α from α 41 not less than α and more than α, the five-layer structure is designed to achieve the best battery conversion efficiency, the thickness and the refractive index of the five-layer on the back of the silicon nitride film layer on the back are gradually increased compared with the traditional thickness, the refractive index is gradually reduced, the film layer is correspondingly better matched with.
Furthermore, the thickness of the back five-layer silicon nitride film layer is 25nm +/-5 nm, 10nm +/-5 nm, 30nm +/-5 nm, 20nm +/-5 nm and 45nm +/-5 nm from inside to outside in sequence, and the refractive index of the back five-layer silicon nitride film layer is 2.6 +/-0.2, 2.1 +/-0.1, 2.5 +/-0.1, 2.3 +/-0.05 and 2.1 +/-0.1 from inside to outside in sequence.
Furthermore, the thickness of the back five-layer silicon nitride film layer is 25nm, 10nm, 30nm, 20nm and 45nm from inside to outside in sequence, and the refractive index of the back five-layer silicon nitride film layer is 2.6, 2.1, 2.5, 2.3 and 2.1 from inside to outside in sequence.
The PERC battery comprises a silicon nitride film layer on the back of the battery, a silicon wafer and a back aluminum oxide film layer arranged on the back of the silicon wafer, wherein the back aluminum oxide film layer is positioned between the silicon wafer and the back silicon nitride film layer. The back silicon nitride film layer is deposited on the back alumina film layer to protect the back alumina film layer, meanwhile, the reflectivity of the back is increased, a better passivation surface is obtained, and the conversion efficiency of the battery is improved.
Furthermore, the battery also comprises a front silicon nitride film layer arranged on the front surface of the silicon wafer. The front silicon nitride film layer is a reflection reducing passivation film.
A preparation method of a PERC battery comprises the following steps:
step 1: obtaining a pretreated silicon wafer through texturing, diffusion, primary annealing, etching and secondary annealing operations;
step 2: depositing a back alumina film layer on the back of the pretreated silicon wafer;
and step 3: depositing a front silicon nitride film layer on the front surface of the pretreated silicon wafer;
and 4, step 4: depositing a back silicon nitride film layer on the back alumina film layer;
and 5: grooving the back surface by adopting laser, and forming a back electrode, a back electric field and a positive electrode by silk-screen printing; sintering and finishing the preparation.
According to the invention, the battery is manufactured by firstly coating the back film and then coating the back film, the back alumina is conveyed by an automatic belt and is wiped by a graphite boat under the condition of no coating, the E L defect is possibly increased by high-frequency physical contact, and the E L defect is equal to the technological mode of firstly coating the back film and then coating the back film through a research experiment of equipment and an automatic manufacturer.
The invention changes the back-to-back coating sequence of the original coating process into the back-to-back coating sequence, prolongs the annealing time of the back alumina, improves the negative charge density of the back alumina, promotes the field passivation effect of the alumina and passivates the generated Al by changing the coating sequence2O3Containing a high density of fixed negative charges, the resulting electric field can reduce surface recombination. Under the condition of not increasing any additional input, the conversion efficiency of the cell piece is improved by 0.05-0.07%.
Furthermore, the process temperature for depositing the back silicon nitride film layer in the step 4 is 470 ℃ +/-20 ℃. According to the invention, by comparing the influences of different back film temperature conditions on the efficiency of the battery piece and researching the structural matching of different temperatures and different back film layers, the photoelectric conversion efficiency of the battery piece is further improved, the process matching of the low temperature of the back film and the five-layer film of the back film is verified, and a new direction is developed for the optimization of the back film process; compared with the conventional process, the photoelectric conversion efficiency of the new matching process is improved remarkably.
Annealing at 500 ℃ after back passivation, wherein the tetrahedron is obviously superior to the octahedron in terms of density, can obtain more negative charges, enhances the back passivation effect and is beneficial to H2Is released. The low-temperature manufacturing process shortens the annealing time of the back film and improves the production efficiency.
Furthermore, in step 4, the back silicon nitride film layer is deposited by plasma enhanced chemical vapor deposition.
Further, the plasma enhanced chemical vapor deposition is tubular plasma enhanced chemical vapor deposition.
Furthermore, the front silicon nitride film layer in step 2 is deposited by plasma enhanced chemical vapor deposition. And the compactness of the back alumina is improved during the manufacturing process, so that the competitiveness of the battery is improved.
Furthermore, the back side alumina film layer in the step 3 is formed by using an atomic layer deposition method.
Furthermore, in step 3, the back silicon nitride film layer is made of NH3And SiH4Providing raw material in equal atmosphere, and adjusting NH during preparation3And SiH4The flow ratio controls the refractive index of each layer of the five-layer film.
Compared with the traditional back film three-layer battery, the back film five-layer battery manufactured at low temperature is improved by 0.05-0.07% in conversion efficiency under the condition of not adding any additional investment, and related parameters such as open-circuit voltage Uoc, short-circuit battery Isc and filling factor FF are obviously improved. The low-temperature manufacturing process has the advantages of better battery conversion efficiency, reduction of the annealing time of the back film, improvement of the production efficiency and suitability for wide application.
3. Advantageous effects
Compared with the prior art, the invention has the advantages that:
(1) the refractive index of the five silicon nitride film layers of the back film is high-low from inside to outside, the thickness of the film layers from inside to outside is thick-thin-thick, and compared with the traditional film layers of which the thickness is gradually increased and the refractive index is gradually reduced, the five silicon nitride film layers on the back surface of the back film have better corresponding matching on the wavelength, the performance efficiency is better, and the current performance advantage is obvious.
(2) The PERC solar cell uses the film coating sequence of a front film and a back film, adopts a low-temperature process, and has the process temperature of 470 +/-20 ℃ when a back silicon nitride film layer is deposited. The five-layer structure of the back film is beneficial to the effects of back surface contact and surface passivation, the open-circuit voltage is improved, meanwhile, a gradient mirror surface is formed on the back surface, the internal reflection of long waves is increased, the reflectivity of the back surface is enhanced, the minority carrier lifetime of the battery is prolonged, and the short-circuit current is increased, so that the photoelectric conversion efficiency is improved.
The manufacturing method can realize the preparation of the back film with matching the five-layer film of the back film under the low-temperature condition on different PECVD deposition equipment, and has simple process steps, stable process and easy control; the temperature of the back film process is 50 degrees lower than that of the conventional process, and the energy consumption is obviously reduced. The low-temperature manufacturing process enables the annealing time of the back film to be compressed for 3 minutes, the capacity to be increased by 4 ten thousand sheets/shift, and the production efficiency is improved.
Drawings
FIG. 1 is a schematic diagram of a cell according to the present invention;
fig. 2 is a schematic diagram of a five-layer structure of the battery back film of the invention.
Detailed Description
The invention is described in detail below with reference to the drawings and specific examples.
Example 1
In this embodiment, a five-layer structure of a backside film of a PERC solar cell and a corresponding low-temperature preparation method are described by taking P-type monocrystalline silicon as an example.
Firstly, the cell structure of the invention is as shown in fig. 1, the front surface of the single crystal cell is plated with a front silicon nitride film layer for reducing reflection, the back film of the cell comprises a back alumina film layer and a back silicon nitride film layer, the back silicon nitride film layer protects the back alumina film layer, and simultaneously increases the reflectivity of the back surface, obtains a better passivated surface and improves the conversion efficiency of the cell.
TABLE 1
Back silicon nitride film layer Film thickness Refractive index
First layer 25nm±5nm 2.6±0.2
Second layer 10nm±5nm 2.1±0.1
Third layer 30nm±5nm 2.5±0.1
The fourth layer 20nm±5nm 2.3±0.05
The fifth layer 45nm±5nm 2.1±0.1
As shown in fig. 2, the back surface silicon nitride film layer in this embodiment is a five-layer film, and NH is used for the five-layer silicon nitride film layer3And SiH4Making special gas cabinet by adjusting NH3And SiH4The flow proportioning controls the refractive indexes of the five layers of films, the thickness of the five silicon nitride film layers on the back surface is α, α 2, α, α and α from inside to outside in sequence, the thickness of α to α from α 31 to 69556 is α to 8663 from not less than α 1 from not less than α from not less than α or α from not less than α from the fifth layer, the first layer, the third layer and the fifth layer are all higher than the fourth layer, the refractive indexes of the silicon nitride film layers on the back surface are α from inside to outside, α from α to α from α to α, and the test shows that the thickness of the five silicon nitride film layers from α from high as shown in the test, and the test results of the testThe average value of the five-layer film is determined, and the thickness and the refractive index of the five-layer film have corresponding ranges on the basis of testing the average value.
The back silicon nitride film layer is optimized on the basis of structures such as single-layer films and double-layer films in the prior art by adjusting different flow ratios of silane or ammonia gas, the deposition passivation effect is increased by setting different thicknesses and refractive index data of the five-layer film structure, the open-circuit voltage Uoc and the short-circuit current Isc of the battery are improved, and the conversion efficiency of the battery is further improved. The five-layer structure of the back film is matched with a 470 ℃ low-temperature deposition process, and the battery performance test verifies that the battery conversion efficiency is remarkably improved.
According to the thickness and the refractive index of the five-layer film of the back silicon nitride film shown by the parameters in table 1, the refractive index from the first layer to the fifth layer from the inside to the outside is high-low, and the thickness of the film is thick-thin-thick, respectively. Through finite times of experimental data analysis, compared with the film with the gradually-reduced refractive index and the gradually-increased thickness, the film with the thickness and the refractive index is qualified in PID, good in corresponding matching to wavelength, better in performance efficiency and obvious in current performance advantage.
Example 2
The back film five-layer structure battery described in embodiment 1 is specifically manufactured by the following steps:
step I: obtaining a pretreated silicon wafer through texturing, diffusion, primary annealing, etching and secondary annealing operations;
a) and (3) texturing:
the surface structure with a plurality of pits on the surface is obtained by using acid solution for isotropic corrosion, and meanwhile, the surface structure can play a good light trapping role, and the monocrystalline silicon wafer is subjected to texturing treatment to form a pyramid textured surface, so that a uniform pyramid-shaped structure is formed on the surface of the silicon wafer, the light absorption is enhanced, and the short-circuit current and the conversion efficiency of the battery are improved.
The reaction equation is: si +4HNO3+6HF＝H2SiF6+4NO3+4H2O。
b) And preparing a PN junction by diffusion:
the surface phosphorus source is advanced, and the surface phosphorus source is advanced,forming PN junction by thermal propulsion, and carrying POC L by gas3The solution enters a diffusion furnace tube to react to generate phosphorus which is deposited on the surface layer, and the phosphorus permeates into the silicon chip to form an N area at high temperature.
The reaction equation is 4POC L3+5O2＝2P2O5+6CL2↑
2P2O5+5Si＝4P↓+5SiO2
4PCL5+5O2＝2P2O5+10CL2↑
4PCL3+5O2＝2P2O5+6CL2↑
c) Carrying out primary annealing;
at about 450 ℃, oxygen in silicon can be converted into oxygen donors, which affects the correct measurement of resistivity, so that the resistivity of the P-type monocrystalline silicon is increased and even inverted; the resistivity of the N-type monocrystalline silicon is reduced. Annealing at about 700 ℃ can return oxygen donors to the interstitial oxygen state, eliminating the effect of oxygen donors on resistivity testing.
The reaction equation is: si + O2＝SiO2(high temperature)
d) Etching;
polishing the back, etching and removing phosphorosilicate glass; using HNO3And corroding the lower surface and the edge of the diffused silicon wafer by using the mixed liquid of HF (hydrogen fluoride) and removing N-type silicon at the edge, so that the upper surface and the lower surface of the silicon wafer are mutually insulated.
e) Carrying out secondary annealing;
and c) annealing treatment to make the oxygen donor return to the interstitial oxygen state and eliminate the influence of the oxygen donor on the resistivity test.
The reaction equation is: si + O2＝SiO2(high temperature)
Step II: depositing a back alumina film layer on the back of the pretreated silicon wafer;
a L D is Atomic layer deposition (Atomic layer deposition), which is a method by which a substance can be deposited on a substrate surface layer by layer in the form of a monoatomic film.
The backside A L D prepares a double-sided aluminum oxide film by alternately pulsing vapor phase precursors into the reactor and chemisorbing and reacting on the deposition substrate to form a deposited film.
Atomic layer deposition surface reactions are self-limiting, i.e., chemisorption self-limiting (CS) and sequential reaction self-limiting (RS) processes, and in fact this self-limiting feature is the basis of atomic layer deposition techniques2O3A certain amount of A L-OH bonds exist in the film, the A L-OH bonds are converted into A L-O bonds after annealing, H atoms are released, a part of the H atoms enter the silicon surface, surface dangling bonds are passivated, and a part of the H atoms are polymerized to form H2。
Step III: depositing a front silicon nitride film layer on the front surface of the pretreated silicon wafer;
plasma Enhanced Chemical Vapor Deposition (PECVD) is a process in which a gas containing atoms of a film component is ionized by means of microwave or radio frequency to locally form a Plasma, and the Plasma is chemically very reactive and easily reacts to deposit a desired film on a substrate.
The method comprises the steps of using low-temperature plasma as an energy source, placing a sample on a cathode of glow discharge under low pressure, heating the sample to a preset temperature by using glow power generation (or adding a heating element), introducing a proper amount of reaction gas, and carrying out a series of chemical reactions and plasma reactions on the gas to form a solid film on the surface of the sample.
The reaction equation is: 4HN3+3SiH4＝Si3N4↓+12H2↑
Step IV: depositing a back silicon nitride film layer on the back alumina film layer;
based on the step II back film alumina, the step III front film silicon nitride film and the step IV back film silicon nitride film, NH is used as the silicon nitride film with a five-layer film structure on the back surface3And SiH4Making special gas cabinet by adjusting NH3And SiH4Controlling the refractive index of each layer of the five-layer film according to the flow ratio; the process is matched with a low-temperature five-layer film silicon nitride film process and is implemented at the temperature of 470 +/-20 ℃.
In the process of depositing silicon nitride by tubular PECVD, along with the increase of temperature, hydroxyl in an alumina film is decomposed, the H content in the film is reduced, the surface passivation effect of a battery piece is weakened, the effective minority carrier lifetime is reduced, the crystallization degree of the film can be optimized by selecting proper growth temperature, different process temperature gradients are tried in the process, and the efficiency at 470 ℃ is optimized.
Al in A L D Process2O3The Al alloy is in two coordination forms of octahedral central position with 6 nitrogen atoms and tetrahedral central position with 4 oxygen atoms, and after annealing heat treatment, the octahedral structure is converted into tetrahedral structure, and the tetrahedron has one more negative charge of oxygen, so that the Al content is increased2O3The negative charge density of the aluminum oxide film is changed from back-to-back coating sequence in the preparation process, so that the annealing time is prolonged, the formation of tetrahedral aluminum oxide is facilitated, and the passivation effect is improved. The positive film is firstly coated and then the back film is coated, the conversion efficiency of the battery is improved by 0.05 percent, the reliability of the battery is unchanged, the efficiency gain is larger, and the cost reduction and the efficiency improvement are obvious.
Step V: grooving the back surface by adopting laser, and forming a back electrode, a back electric field and a positive electrode by silk-screen printing; sintering and finishing the preparation.
i) Laser local grooving on the back;
the current on the back surface of the silicon chip is led out through the photoetching groove, absorbed by the back electric field and conducted to the back electric field.
ii) screen printing to form a back electrode, a back electric field and a positive electrode, and printing positive silver by adopting ozone single-sided polymerization slurry;
the silk screen printing mainly utilizes the basic principle that the meshes of the image-text part of the screen plate are ink-permeable and the meshes of the non-image-text part are ink-impermeable to print.
The single-side silver paste is adopted for matching in printing, the experiment takes the matching of the polymerization slurry as an example, and specifically, the ozone single-side polymerization slurry W L698 has the etching-through performance on aluminum oxide and the matching reduces the thickness of the front-side aluminum oxide.
iii) sintering to form a good ohmic contact between the metal and the silicon.
The electrical performance of the cells fabricated by the process of the invention was tested.
In the detection of the battery performance, the following three sets of experiments are designed in the present example, and the parameter measurement is performed on the three-layer structure of the back membrane and the five-layer structure of the back membrane at different temperatures.
The experiment is a temperature gradient experiment of a three-layer film of a back film, the process temperature is respectively 450 degrees, 470 degrees and 530 degrees, wherein 530 degrees is the temperature of the existing production line, and the experiment result is shown in table 2.
The second experiment is a temperature gradient experiment of the five-layer back film, the process temperatures are respectively 450 degrees, 470 degrees and 530 degrees, wherein 530 degrees is the temperature of the existing production line, and the experiment results are shown in table 3.
Experiment three is a low-temperature process amount experiment matched with a three-layer film structure of the back film and a five-layer film structure of the back film, and the experimental results are shown in table 4.
In tables 2, 3 and 4, Eta represents the conversion efficiency of the battery, which is an important parameter for measuring the quality and technical level of the battery, and is related to the structure, junction characteristics, material properties, operating temperature, radioactive particle radiation damage, environmental changes, and the like of the battery. Uoc represents an open circuit voltage, which is an output voltage value of a solar cell when the solar cell is exposed to a light source of 100mW/cm2 and both ends are open. The Isc represents a short-circuit current, the circuit current is the current which flows through two ends of the solar cell when the output end is short-circuited when the solar cell is placed under the irradiation of a standard light source, and the Isc and the Uoc represent the conversion efficiency of the cell. FF represents a fill factor, also called a curve factor, which is a ratio of the maximum power of the solar cell to the product of the open-circuit voltage and the short-circuit current, and is an important parameter for evaluating the output characteristics of the solar cell. Rser is series resistance, Rshunt is leakage parallel resistance, and Irevmax is dark current.
TABLE 2
Figure BDA0002464463470000081
TABLE 3
Figure BDA0002464463470000082
TABLE 4
Figure BDA0002464463470000083
According to the experimental data in tables 2 and 3, the process efficiency is the highest at 470 degrees, which is mainly reflected in the improvement of the short-circuit current Isc. According to the experimental data in table 4, the experimental process efficiency of the temperature gradient of the five-layer film of the back film is about 0.05% higher than the conversion efficiency of the three-layer film battery of the back film in the production line process, and the parameters such as open-circuit voltage Uoc, short-circuit battery Isc and filling factor FF are all advantageous.
The conversion efficiency of the cell refers to the proportion of the solar cell converting light energy into electric energy, according to the records of related documents, the cell conversion rate of the single crystal cell is improved to be close to 20% from 19% in 2013 to 2018, and experiments prove that the back silicon nitride film layer cell with the five-layer structure, which is manufactured at 470 ℃, of the preparation method disclosed by the invention is improved by about 0.05%, so that the conversion rate is greatly broken through, and the efficiency is remarkably increased.
The manufacturing sequence of the battery is as follows: front-back passivation-front film-back film; the original back-to-back coating procedure is changed into the back-to-back coating sequence, the annealing time of the back alumina film layer is prolonged, the negative charge density of the back alumina film layer is improved, the field passivation effect of alumina is improved, and Al generated by passivation is added2O3Containing a high density of fixed negative charges, the resulting electric field can reduce surface recombination.
Compared with a single-layer film single-crystal PERC battery with a PECVD back surface, the single-crystal PERC battery prepared by the preparation method has the advantages that the short-circuit current is improved, the open-circuit voltage is improved, and the battery conversion efficiency is improved by 0.05-0.07 percent.
The invention and its embodiments have been described above schematically, without limitation, and the invention can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The representation in the drawings is only one of the embodiments of the invention, the actual construction is not limited thereto, and any reference signs in the claims shall not limit the claims concerned. Therefore, if a person skilled in the art receives the teachings of the present invention, without inventive design, a similar structure and an embodiment to the above technical solution should be covered by the protection scope of the present patent. Furthermore, the word "comprising" does not exclude other elements or steps, and the word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. Several of the elements recited in the product claims may also be implemented by one element in software or hardware. The terms first, second, etc. are used to denote names, but not any particular order.

Claims (12)

1. The battery back silicon nitride film layer is characterized by comprising a five-layer structure, wherein the back five-layer silicon nitride film layer has the thicknesses of α, α 2, α 03, α and α from inside to outside in sequence, the thicknesses of α 31 to α from α to α from α from 8653 from 861 from α to α from or α from α to α from α.
2. The battery back silicon nitride film layer of claim 1, wherein the back five-layer silicon nitride film layer has a thickness ranging from 25nm ± 5nm, 10nm ± 5nm, 30nm ± 5nm, 20nm ± 5nm and 45nm ± 5nm from inside to outside, and a refractive index ranging from 2.6 ± 0.2, 2.1 ± 0.1, 2.5 ± 0.1, 2.3 ± 0.05 and 2.1 ± 0.1 from inside to outside.
3. The battery back silicon nitride film layer of claim 2, wherein the back five-layer silicon nitride film layer has a thickness of 25nm, 10nm, 30nm, 20nm and 45nm from inside to outside, and the refractive index of the back five-layer silicon nitride film layer is 2.6, 2.1, 2.5, 2.3 and 2.1 from inside to outside.
4. A PERC cell comprising a cell back side silicon nitride film layer according to any one of claims 1 to 3, further comprising a silicon wafer and a back side alumina film layer disposed on the back side of the silicon wafer, said back side alumina film layer being disposed between the silicon wafer and said back side silicon nitride film layer.
5. The PERC cell of claim 4, further comprising a front side silicon nitride film layer disposed on the front side of the silicon wafer.
6. A method of making the PERC cell of any of claims 4-5, comprising the steps of:
step I: obtaining a pretreated silicon wafer through texturing, diffusion, primary annealing, etching and secondary annealing operations;
step II: depositing a back alumina film layer on the back of the pretreated silicon wafer;
step III: depositing a front silicon nitride film layer on the front surface of the pretreated silicon wafer;
step IV: depositing a back silicon nitride film layer on the back alumina film layer;
step V: grooving the back surface by adopting laser, and forming a back electrode, a back electric field and a positive electrode by silk-screen printing; sintering and finishing the preparation.
7. The method of claim 6, wherein the deposition of the back silicon nitride film in step 4 is performed at a temperature of 470 ℃ ± 20 ℃.
8. The method of claim 7, wherein the step 4 of depositing the backside silicon nitride film layer is performed by plasma enhanced chemical vapor deposition.
9. The method of claim 8, wherein the plasma enhanced chemical vapor deposition is a tube plasma enhanced chemical vapor deposition.
10. The method of claim 6, wherein the front silicon nitride film layer in step 2 is deposited by plasma enhanced chemical vapor deposition.
11. The method of claim 6, wherein the backside alumina film layer in step 3 is formed by atomic layer deposition.
12. The method of claim 11, wherein the backside silicon nitride film layer in step 3 is formed of NH3And SiH4Providing raw material in equal atmosphere, and adjusting NH during preparation3And SiH4The flow ratio controls the refractive index of each layer of the five-layer film.
CN202010329604.6A 2020-04-24 2020-04-24 Silicon nitride film layer on back of battery, PERC battery and preparation method Pending CN111416002A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114497240A (en) * 2022-03-30 2022-05-13 浙江晶科能源有限公司 Solar cell, preparation method thereof and photovoltaic module
WO2022110613A1 (en) * 2020-11-27 2022-06-02 浙江贝盛光伏股份有限公司 Perc cell preparation method

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2022110613A1 (en) * 2020-11-27 2022-06-02 浙江贝盛光伏股份有限公司 Perc cell preparation method
CN114497240A (en) * 2022-03-30 2022-05-13 浙江晶科能源有限公司 Solar cell, preparation method thereof and photovoltaic module

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