阅读说明：本技术 一种太阳能电池的扩散工艺、制备方法及硅片 (Diffusion process and preparation method of solar cell and silicon wafer ) 是由 刘泉 陈太昌 祁嘉铭 陈家健 方贵允 于 2021-06-25 设计创作，主要内容包括：本发明公开了一种太阳能电池的扩散工艺、制备方法及硅片,该扩散工艺包括：在扩散炉管内,将制绒后的硅片通入携带三氯氧磷的小氮,在第一温度下沉积磷源,并在第二温度下通入氧气和大氮进行高温推进得到PN结；通入携带三氯氧磷的小氮,二次沉积磷源,进而在硅片表面形成含低浓度磷源的磷硅玻璃层；通入大氮对进行吹扫,结束扩散,在硅片表面获得含低浓度磷源的发射极。本发明采用两步通源沉积的方式,使三氯氧磷均在低温环境下沉积,可以使硅片表面浓度充分降低,同时通过控制磷源沉积的大氮、氧气和小氮的气体流量比来保证PN结的均匀性,可以有效提高太阳能电池的转换效率。(The invention discloses a diffusion process, a preparation method and a silicon wafer of a solar cell, wherein the diffusion process comprises the following steps: in a diffusion furnace tube, introducing small nitrogen carrying phosphorus oxychloride into the silicon wafer after texturing, depositing a phosphorus source at a first temperature, and introducing oxygen and large nitrogen at a second temperature to carry out high-temperature propulsion to obtain a PN junction; introducing small nitrogen carrying phosphorus oxychloride, and depositing a phosphorus source for the second time to form a phosphorus-silicon glass layer containing a low-concentration phosphorus source on the surface of the silicon wafer; and introducing large nitrogen to purge, finishing diffusion and obtaining the emitter containing the low-concentration phosphorus source on the surface of the silicon wafer. The invention adopts a two-step source-through deposition mode to ensure that phosphorus oxychloride is deposited in a low-temperature environment, the surface concentration of the silicon wafer can be fully reduced, and meanwhile, the uniformity of the PN junction is ensured by controlling the gas flow ratio of large nitrogen, oxygen and small nitrogen deposited by a phosphorus source, and the conversion efficiency of the solar cell can be effectively improved.)

1. A diffusion process for a solar cell, comprising:

in a diffusion furnace tube, introducing small nitrogen carrying phosphorus oxychloride into a silicon wafer after texturing, depositing a phosphorus source for the first time at a preset first temperature, and introducing oxygen and large nitrogen at a preset second temperature to carry out high-temperature propulsion to obtain a PN junction;

introducing small nitrogen carrying phosphorus oxychloride into the PN junction, and depositing a phosphorus source for the second time, thereby forming a phosphorus-silicon glass layer containing a low-concentration phosphorus source on the surface of the silicon wafer;

and introducing large nitrogen to blow the phosphorosilicate glass layer, finishing diffusion and obtaining the emitter containing the low-concentration phosphorus source on the surface of the silicon wafer.

2. The diffusion process of the solar cell according to claim 1, wherein before introducing small nitrogen carrying phosphorus oxychloride into the PN junction to deposit a phosphorus source for the first time and form a phosphosilicate glass layer containing a low concentration of phosphorus source on the surface of the silicon wafer, the process comprises:

and cooling the temperature in the diffusion furnace tube to 750-770 ℃ under the conditions that the preset temperature reduction time is 1500-2000 s and the preset pressure is 90-110 mbar.

3. The diffusion process of the solar cell according to claim 1, wherein the predetermined first temperature is 750 ℃ to 780 ℃ and the predetermined second temperature is 860 ℃ to 870 ℃.

4. The diffusion process of the solar cell according to claim 1, wherein the deposition time for depositing the phosphorus source is 8-14 min.

5. The diffusion process of the solar cell according to claim 3, wherein the step of introducing small nitrogen carrying phosphorus oxychloride into the textured silicon wafer, depositing a phosphorus source for the first time at a preset first temperature, and introducing oxygen and large nitrogen at a preset second temperature to perform high-temperature propulsion to obtain a PN junction comprises the steps of:

introducing 800 sccm-1500 sccm oxygen and 600 sccm-1200 sccm big nitrogen, and forming a silicon dioxide film on the surface of the silicon wafer under the conditions that the temperature is 750-780 ℃ and the pressure is 90 mbar-110 mbar;

introducing 600 sccm-1200 sccm of small nitrogen carrying phosphorus oxychloride, 400 sccm-1000 sccm of oxygen and 600 sccm-1200 sccm of large nitrogen, and depositing a phosphorus source on the surface of the silicon wafer for the first time under the conditions that the temperature is 750-780 ℃ and the pressure is 90 mbar-110 mbar, wherein the deposition time is 3 min-4 min;

introducing oxygen of 200 sccm-600 sccm and macronitrogen of 600 sccm-1200 sccm, and performing high-temperature propulsion at 860-870 ℃ and under 90 mbar-110 mbar for 12 min-18 min to obtain the PN junction.

6. The diffusion process of the solar cell according to claim 1, wherein the introducing of the small nitrogen carrying phosphorus oxychloride for the second deposition of the phosphorus source to form the phosphosilicate glass layer containing the low concentration of the phosphorus source on the surface of the silicon wafer comprises:

introducing oxygen of 200 sccm-600 sccm, big nitrogen of 600 sccm-1200 sccm and small nitrogen carrying phosphorus oxychloride of 600 sccm-1200 sccm, and depositing the phosphorus source on the surface of the silicon wafer again under the conditions of the temperature of 750-780 ℃ and the pressure of 90 mbar-110 mbar for 7 min-15 min.

7. A silicon wafer suitable for a solar cell, characterized in that it is produced by the diffusion process of the solar cell according to any one of claims 1 to 6.

8. A method for manufacturing a solar cell, comprising the diffusion process of the solar cell according to any one of claims 1 to 6.

9. The method for manufacturing a solar cell according to claim 8, further comprising:

and carrying out laser doping, etching, annealing, back coating, front coating, laser grooving, printing and sintering, electrical injection and test sorting on the silicon wafer in sequence.

10. The method of claim 9, wherein the steps of laser doping, etching, annealing, back coating, front coating, laser grooving, printing and sintering, electrical injection, and test sorting are performed on the silicon wafer in sequence, and comprise:

heavily doping the contact part of the silicon chip by adopting a laser doping mode;

polishing the back surface of the silicon wafer by adopting nitric acid and hydrogen fluoride solution, and removing a phosphorosilicate glass layer on the front surface of the silicon wafer;

annealing the etched silicon wafer, and depositing a silicon dioxide layer on the surface of the silicon wafer;

depositing a layer of aluminum oxide and silicon nitride passivation film on the back of the silicon wafer by a deposition method;

growing and depositing a silicon nitride film on the front surface of the silicon wafer by a deposition method;

performing laser grooving on the back of the coated silicon wafer;

printing the back and the front of the silicon wafer by utilizing screen printing, and then performing a sintering process;

carrying out electrical injection on the silicon wafer through a light attenuation furnace or an electrical injection furnace to obtain a battery piece;

and performing battery test grading on the battery pieces.

Technical Field

The invention relates to the technical field of solar cells, in particular to a diffusion process and a preparation method of a solar cell and a silicon wafer.

Background

At present, the photovoltaic field is rapidly developed, and photovoltaic products which are suitable for various requirements continuously refresh the cognition of the outside to the photovoltaic. How to realize photovoltaic flat-price internet surfing is still a topic continuously explored in the photovoltaic field, and a solar cell with high efficiency and low cost gradually becomes a mainstream in the market. With the continuous updating of solar technology, the conversion efficiency of solar cells is also gradually increased. Among the emerging technologies, the PERC (Passivated Emitter and reader Cell) Cell, which superimposes Selective Emitter (SE) technology, is undoubtedly one of the hottest areas. SE cells can be doped with lasers, having mainly two features: 1) the contact area of the metal grid line and the silicon wafer is a heavily doped area which can form good ohmic contact and improve the filling factor; 2) the light receiving area is a lightly doped area, short wave response can be improved, and minority carrier recombination is reduced due to low surface concentration, so that open-circuit voltage and short-circuit current are increased.

The SE technology mainly uses phosphosilicate glass (PSG) as a phosphorus source, and injects the phosphorus source outside a PN junction into the surface layer of a silicon wafer in a laser ablation mode, so that a high-doping area is formed locally, therefore, a diffusion process is used as a pre-process of a laser doping process, and a necessary phosphorus source is provided for selective doping.

Although various methods have been proposed in the prior art to improve the conversion efficiency of solar cells, these methods all have certain drawbacks. For example, the prepared PN junction is shallow, but the existing slurry has generally strong corrosivity, so that the prepared PN junction is easily burnt through during silk-screen sintering to influence the performance of a battery piece; or in the operation process, the residual phosphorus source damages the surface of the silicon wafer, the phosphorus-silicon glass layer is too thick due to too many times of oxidation, and the concentration difference between the heavily doped region and the lightly doped region is too large, so that the recombination of current carriers is increased, and the improvement of the open-circuit voltage is not facilitated. Or the phosphorus source is deposited for too many times, so that the phosphorus source on the surface of the silicon wafer is redistributed for many times, the doping concentration of the whole silicon wafer is higher, the doping effect is influenced, and the conversion efficiency of the cell is not favorably and greatly improved.

Disclosure of Invention

The embodiment of the invention provides a diffusion process and a preparation method of a solar cell and a silicon wafer, and aims to improve the conversion efficiency of the solar cell.

The embodiment of the invention provides a diffusion process of a solar cell, which comprises the following steps:

in a diffusion furnace tube, introducing small nitrogen carrying phosphorus oxychloride into a silicon wafer after texturing, depositing a phosphorus source for the first time at a preset first temperature, and introducing oxygen and large nitrogen at a preset second temperature to carry out high-temperature propulsion to obtain a PN junction;

introducing small nitrogen carrying phosphorus oxychloride into the PN junction, and depositing a phosphorus source for the second time, thereby forming a phosphorus-silicon glass layer containing a low-concentration phosphorus source on the surface of the silicon wafer;

and introducing large nitrogen to blow the phosphorosilicate glass layer, finishing diffusion and obtaining the emitter containing the low-concentration phosphorus source on the surface of the silicon wafer.

Further, before introducing small nitrogen carrying phosphorus oxychloride and depositing a phosphorus source for the first time to form a phosphorus-silicon glass layer containing a low-concentration phosphorus source on the surface of the silicon wafer, the method comprises the following steps:

and cooling the temperature in the diffusion furnace tube to 750-770 ℃ under the conditions that the preset temperature reduction time is 1500-2000 s and the preset pressure is 90-110 mbar.

Further, the preset first temperature is 750-780 ℃, and the preset second temperature is 860-870 ℃.

Further, the deposition time of the first deposition of the phosphorus source is 8-14 min.

Further, the silicon wafer after the texturing is introduced with the small nitrogen carrying phosphorus oxychloride, the phosphorus source is deposited at a preset first temperature, and oxygen and large nitrogen are introduced at a preset second temperature for high-temperature propulsion to obtain the PN junction, including:

introducing 800 sccm-1500 sccm oxygen and 600 sccm-1200 sccm big nitrogen, and forming a silicon dioxide film on the surface of the silicon wafer under the conditions that the temperature is 750-780 ℃ and the pressure is 90 mbar-110 mbar;

introducing 600 sccm-1200 sccm of small nitrogen carrying phosphorus oxychloride, 400 sccm-1000 sccm of oxygen and 600 sccm-1200 sccm of large nitrogen, and depositing a phosphorus source on the surface of the silicon wafer for the first time under the conditions that the temperature is 750-780 ℃ and the pressure is 90 mbar-110 mbar, wherein the deposition time is 3 min-4 min;

introducing oxygen of 200 sccm-600 sccm and macronitrogen of 600 sccm-1200 sccm, and performing high-temperature propulsion at 860-870 ℃ and under 90 mbar-110 mbar for 12 min-18 min to obtain the PN junction.

Further, the introducing of the small nitrogen carrying phosphorus oxychloride to deposit the phosphorus source for the second time so as to form a phosphorus-silicon glass layer containing the low-concentration phosphorus source on the surface of the silicon wafer comprises the following steps:

introducing oxygen of 200 sccm-600 sccm, big nitrogen of 600 sccm-1200 sccm and small nitrogen carrying phosphorus oxychloride of 600 sccm-1200 sccm, and depositing the phosphorus source on the surface of the silicon wafer again under the conditions of the temperature of 750-780 ℃ and the pressure of 90 mbar-110 mbar for 7 min-15 min.

The embodiment of the invention provides a silicon wafer which is suitable for a solar cell and is manufactured by adopting the diffusion process of the solar cell.

The embodiment of the invention provides a preparation method of a solar cell, which comprises the diffusion process of the solar cell.

Further, the method also comprises the following steps:

and carrying out laser doping, etching, annealing, back coating, front coating, laser grooving, printing and sintering, electrical injection and test sorting on the silicon wafer in sequence.

Further, the silicon wafer is sequentially subjected to laser doping, etching, annealing, back coating, front coating, laser grooving, printing and sintering, electrical injection and test sorting operations, and the method comprises the following steps:

heavily doping the contact part of the silicon chip by adopting a laser doping mode;

polishing the back surface of the silicon wafer by adopting nitric acid and hydrogen fluoride solution, and removing a phosphorosilicate glass layer on the front surface of the silicon wafer;

annealing the etched silicon wafer, and depositing a silicon dioxide layer on the surface of the silicon wafer;

depositing a layer of aluminum oxide and silicon nitride passivation film on the back of the silicon wafer by a deposition method;

growing and depositing a silicon nitride film on the front surface of the silicon wafer by a deposition method;

performing laser grooving on the back of the coated silicon wafer;

printing the back and the front of the silicon wafer by utilizing screen printing, and then performing a sintering process;

carrying out electrical injection on the silicon wafer through a light attenuation furnace or an electrical injection furnace to obtain a battery piece;

and performing battery test grading on the battery pieces.

The embodiment of the invention provides a diffusion process, a preparation method and a silicon wafer of a solar cell, wherein the diffusion process comprises the following steps: in a diffusion furnace tube, introducing small nitrogen carrying phosphorus oxychloride into a silicon wafer after texturing, depositing a phosphorus source for the first time at a preset first temperature, and introducing oxygen and large nitrogen at a preset second temperature to carry out high-temperature propulsion to obtain a PN junction; introducing small nitrogen carrying phosphorus oxychloride into the PN junction, and depositing a phosphorus source for the second time, thereby forming a phosphorus-silicon glass layer containing a low-concentration phosphorus source on the surface of the silicon wafer; and introducing large nitrogen to blow the phosphorosilicate glass layer, finishing diffusion and obtaining the emitter containing the low-concentration phosphorus source on the surface of the silicon wafer. According to the embodiment of the invention, the phosphorus source is deposited at low temperature, oxygen and large nitrogen are introduced at high temperature for high-temperature propulsion to obtain the PN junction with lower surface concentration, and then the phosphorus source is continuously deposited at low temperature on the PN junction to obtain the phosphosilicate glass layer containing the phosphorus source with low concentration, so that selective doping by an SE (selective emitter SE) technology is facilitated. The embodiment of the invention adopts a two-step source-through deposition mode, so that phosphorus oxychloride is deposited in a low-temperature environment, the surface concentration of a silicon wafer can be fully reduced, and meanwhile, the uniformity of a PN junction is ensured by controlling the gas flow ratio of large nitrogen, oxygen and small nitrogen deposited by a phosphorus source, so that the low surface concentration and high-quality PN junction of a silicon wafer emitter region are ensured, the short-wave response is increased, the internal defects of the silicon wafer are reduced, the recombination of surface minority carriers is reduced, and the conversion efficiency of a solar cell is effectively improved.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a schematic flow chart of a diffusion process of a solar cell according to an embodiment of the present invention;

fig. 2 is a schematic sub-flow diagram of a diffusion process of a solar cell according to an embodiment of the present invention;

fig. 3 is a schematic flow chart of a method for manufacturing a solar cell according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It will be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

It is also to be understood that the terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the specification of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It should be further understood that the term "and/or" as used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

Referring to fig. 1, fig. 1 is a schematic flow chart of a diffusion process of a solar cell according to an embodiment of the present invention, which specifically includes: steps S101 to S103.

S101, in a diffusion furnace tube, introducing small nitrogen carrying phosphorus oxychloride into a textured silicon wafer, depositing a phosphorus source for the first time at a preset first temperature, and introducing oxygen and large nitrogen at a preset second temperature to perform high-temperature propulsion to obtain a PN junction;

s102, introducing small nitrogen carrying phosphorus oxychloride into the PN junction, depositing a phosphorus source for the second time, and further forming a phosphorus-silicon glass layer containing a low-concentration phosphorus source on the surface of the silicon wafer;

s103, introducing large nitrogen to blow the phosphorosilicate glass layer, finishing diffusion, and obtaining an emitter containing a low-concentration phosphorus source on the surface of the silicon wafer.

In this embodiment, the silicon wafer after texturing is first pushed into a diffusion furnace tube, and then phosphorus oxychloride (POCl) is introduced into the diffusion furnace tube₃) And (3) carrying out primary phosphorus source deposition on the small nitrogen, introducing oxygen and large nitrogen, and carrying out high-temperature propulsion on the silicon wafer to obtain the PN junction. Then introducing small nitrogen carrying phosphorus oxychloride into the obtained PN junction, and depositing the phosphorus source on the surface of the silicon wafer again so as to form a phosphorus-silicon glass layer containing a low-concentration phosphorus source on the surface of the silicon wafer. Then, the emitter containing a low concentration of phosphorus source is purged by introducing large nitrogen.

According to the embodiment of the invention, the phosphorus source is deposited at low temperature, oxygen and large nitrogen are introduced at high temperature for high-temperature propulsion to obtain the PN junction with lower surface concentration, and then the phosphorus source is continuously deposited at low temperature on the PN junction to obtain the phosphosilicate glass layer containing the phosphorus source with low concentration, so that selective doping by an SE (selective emitter SE) technology is facilitated. The embodiment of the invention adopts a two-step source-through deposition mode, so that phosphorus oxychloride is deposited in a low-temperature environment, the surface concentration of a silicon wafer can be fully reduced, and meanwhile, the uniformity of a PN junction is ensured by controlling the gas flow ratio of large nitrogen, oxygen and small nitrogen deposited by a phosphorus source, so that the low surface concentration and high-quality PN junction of a silicon wafer emitter region are ensured, the short-wave response is increased, the internal defects of the silicon wafer are reduced, the recombination of surface minority carriers is reduced, and the conversion efficiency of a solar cell is effectively improved. In a specific application scenario, the embodiment of the invention can improve the conversion efficiency of the solar cell by 0.18%.

In another specific application scenario, the silicon wafer is loaded into the diffusion furnace tube through a quartz boat, and after the diffusion is finished, the quartz boat is pushed out of the diffusion furnace tube, and the silicon wafer containing the emitter of the low-concentration phosphorus source is taken out.

In addition, in this embodiment, nitrogen carrying phosphorus oxychloride is referred to as small nitrogen, the small nitrogen functions as a carrier gas of phosphorus oxychloride to enhance the volatilization effect of phosphorus oxychloride, and nitrogen not carrying phosphorus oxychloride is referred to as large nitrogen.

In one embodiment, the preset first temperature is 750 ℃ to 780 ℃, and the preset second temperature is 860 ℃ to 870 ℃. Namely, small nitrogen carrying POCl3 is introduced into a diffusion furnace tube to deposit a phosphorus source at the low temperature of 750-780 ℃, and oxygen and large nitrogen are introduced at the high temperature of 860-870 ℃ to carry out high-temperature propulsion to obtain the PN junction.

Further, the deposition time of the first deposition of the phosphorus source is 8-14 min.

In one embodiment, as shown in fig. 2, the step S101 includes: steps S201 to S203.

S201, introducing 800-1500 sccm oxygen and 600-1200 sccm big nitrogen, and forming a silicon dioxide film on the surface of the silicon wafer under the conditions that the temperature is 750-780 ℃ and the pressure is 90 mbar-110 mbar;

in the step, because the diffusion coefficient of phosphorus in silicon dioxide is far smaller than that in silicon, the silicon dioxide film is formed to be used as a blocking surface, so that a phosphorus source is more uniformly diffused to the surface of a silicon wafer through an oxide film during diffusion, and particularly, the phosphorus source can effectively block phosphorus atoms with weak activity, thereby reducing a diffusion layer and slowing down the diffusion propulsion rate. The nitrogen gas is used as protective gas to maintain the inert environment of the diffusion furnace tube and expel the air in the diffusion furnace tube, so that the inside of the diffusion furnace tube is kept at certain cleanliness.

S202, introducing 600 sccm-1200 sccm of small nitrogen carrying phosphorus oxychloride, 400 sccm-1000 sccm of oxygen and 600 sccm-1200 sccm of large nitrogen, and depositing a phosphorus source on the surface of the silicon wafer for the first time under the conditions that the temperature is 750-780 ℃ and the pressure is 90 mbar-110 mbar, wherein the deposition time is 3 min-4 min;

in the step, the phosphorus oxychloride can be blown into the diffusion furnace tube by introducing the large nitrogen, so that the phosphorus oxychloride is uniformly distributed in the diffusion furnace tube, and the oxygen can fully decompose the phosphorus oxychloride, thereby preventing redundant phosphorus from corroding the silicon wafer.

S203, introducing oxygen of 200 sccm-600 sccm and big nitrogen of 600 sccm-1200 sccm, and performing high-temperature propulsion at 860-870 ℃ and under 90 mbar-110 mbar to obtain the PN junction, wherein the propulsion time is 12 min-18 min.

In the step, the main function of the oxygen is to fully react the phosphorus source deposited on the surface of the silicon wafer, which is beneficial to the propulsion of PN junctions, and the function of the large nitrogen is mainly to maintain the atmosphere environment in the tube and keep the oxygen uniformly distributed in the furnace tube.

In this embodiment, through steps S201 to S203, a PN junction with a low surface concentration can be obtained by advancing on a silicon wafer, and then a phosphorus source is deposited on the PN junction at a low temperature to obtain a phosphosilicate glass layer containing a phosphorus source with a low concentration, which is beneficial to SE technology for selective doping.

In one embodiment, before the secondary deposition of the phosphorus source, the temperature in the diffusion furnace tube is cooled to 750-770 ℃ through the preset temperature reduction time of 1500-2000 s and the preset pressure of 90-110 mbar.

Further, when the secondary deposition of the phosphorus source is carried out, 200 sccm-600 sccm of oxygen, 600 sccm-1200 sccm of large nitrogen and 600 sccm-1200 sccm of small nitrogen carrying phosphorus oxychloride are introduced into the cooled diffusion furnace tube, and the phosphorus source is deposited on the surface of the silicon wafer again under the conditions that the temperature is 750-780 ℃ and the pressure is 90 mbar-110 mbar, wherein the deposition time is 7 min-15 min.

In an embodiment, in order to verify the effect of the diffusion process of the solar cell provided in the embodiment of the present invention, the silicon wafer manufactured by the conventional diffusion process is used as comparative example 1, and the silicon wafer manufactured by the diffusion process of the embodiment of the present invention is used as embodiment 1.

The specific process of the traditional diffusion process is described as follows:

s11, introducing oxygen of 800-1500 sccm and macro nitrogen of 600-1200 sccm, setting the treatment temperature to 780 ℃, controlling the furnace tube pressure to 90-110 mbar, and controlling the treatment time to 200-300S.

S12, introducing oxygen of 400 sccm-1000 sccm, macro nitrogen of 600 sccm-1200 sccm, POCl carried by 600 sccm-1200 sccm₃The small nitrogen is diffused under the conditions of 750-780 ℃ and 90-110 mbar pressure, and the diffusion time is 3-4 min;

s13, introducing oxygen of 200 sccm-600 sccm and big nitrogen of 600 sccm-1200 sccm, and performing high-temperature propulsion at 840-850 ℃ under the pressure of 90 mbar-110 mbar to obtain the PN junction, wherein the propulsion time is 12 min-18 min.

S14, setting the temperature reduction time to 1200-1800S, fully cooling the temperature in the diffusion furnace tube to 780-790 ℃ under the condition that the pressure is 90-110 mbar, and then introducing 400-1000 sccm oxygen, 600-1200 sccm big nitrogen and 600-1200 sccm carried POCl₃The small nitrogen is diffused under the conditions of 780-790 ℃ and 90-110 mbar pressure, and the diffusion time is 2-4 min.

S15, setting the temperature reduction time to be 500-1000S, fully cooling the temperature in the diffusion furnace tube to 760-780 ℃ under the condition that the pressure is 90-110 mbar, and then introducing 400-1000 sccm oxygen, 600-1200 sccm big nitrogen and 600-1200 sccm carried POCl₃The small nitrogen is diffused under the conditions of 760 ℃ to 780 ℃ and the pressure of 90mbar to 110mbar, and the diffusion time is 4min to 10 min.

The silicon wafers after the diffusion treatment described in comparative example 1 and example 1 were subjected to the sheet resistance measurement, and further subjected to laser doping under the same conditions, and the sheet resistance data at this time were measured, and the results are shown in table 1.

TABLE 1

As can be seen from the data in Table 1, the sheet resistance reduction amplitude (the difference between the sheet resistance of the silicon wafer after diffusion and the sheet resistance after laser doping) of the comparative example 1 is generally between 80 and 95, while the sheet resistance reduction amplitude of the example 1 is generally between 60 and 75, and according to the comparison of the data of the comparative example 1 and the data of the example 1, the sheet resistance reduction amplitude of the example 1 is obviously smaller, and the smaller the sheet resistance reduction amplitude is, the lower the surface concentration of the battery piece is, the less the recombination of the battery piece is, the corresponding open-circuit voltage, short-circuit current and filling factor are increased, and further the efficiency of the battery piece is increased.

After the silicon wafer is further prepared into a selective emitter cell, the electrical performance parameters of the silicon wafer are measured, and the results are shown in table 2.

	Uoc(V)	Isc(A)	Rs(Ω)	Rsh(Ω)	FF	Ncell
							Comparative example 1	0.6820	10.1287	0.0018	309.07	81.23	22.26％
Example 1	0.6831	10.1600	0.0017	319	81.48	22.44％

TABLE 2

As can be seen from table 2, the electrical performance of the silicon wafer for the PERC (Passivated Emitter and Rear Cell) solar Cell obtained by the diffusion process of the solar Cell provided in the embodiment of the present invention is improved by 0.18% compared with the conventional process. It should be noted that, this is data for improving performance of a single silicon wafer, and in practical applications, the PERC solar cell is combined with a plurality of silicon wafers (for example, 72), so that the generated power of the whole solar cell set can be greatly improved.

The embodiment of the invention also provides a silicon wafer which is suitable for a solar cell and is manufactured by adopting the diffusion process of the solar cell.

The embodiment of the invention also provides a preparation method of the solar cell, which comprises the diffusion process of the solar cell.

Further, the preparation method of the solar cell further comprises the following steps:

and carrying out laser doping, etching, annealing, back coating, front coating, laser grooving, printing and sintering, electrical injection and test sorting on the silicon wafer in sequence.

Specifically, as shown in fig. 3, the sequentially performing laser doping, etching, annealing, back surface coating, front surface coating, laser grooving, printing and sintering, electrical injection, and test sorting operations on the silicon wafer includes: steps S301 to S309.

S301, heavily doping the contact part of the silicon wafer in a laser doping mode;

s302, polishing the back of the silicon wafer by adopting nitric acid and hydrogen fluoride solution, and removing a phosphorosilicate glass layer on the front of the silicon wafer;

s303, annealing the etched silicon wafer, and depositing a silicon dioxide layer on the surface of the silicon wafer;

s304, depositing a layer of aluminum oxide and silicon nitride passivation film on the back of the silicon wafer by a deposition method;

s305, growing and depositing a silicon nitride film on the front surface of the silicon wafer by a deposition method;

s306, performing laser grooving on the back of the coated silicon wafer;

s307, printing the back and the front of the silicon wafer by utilizing screen printing, and then performing a sintering process;

s308, performing electric injection on the silicon wafer through a light attenuation furnace or an electric injection furnace to obtain a battery piece;

and S309, performing battery test grading on the battery pieces.

In this embodiment, after the diffusion process of the solar cell is performed on the textured silicon wafer, the operations of laser doping (SE), etching, annealing, back coating, front coating, laser grooving, printing and sintering, electrical injection, test sorting and the like are sequentially performed on the silicon wafer.

The preparation steps of the PERC solar cell will now be described in detail:

1) texturing: the monocrystalline silicon wafer is subjected to surface texturing to obtain a good textured structure.

2) Diffusion: the diffusion process of the solar cell provided by the embodiment of the invention is utilized to carry out diffusion treatment on the silicon wafer.

3) And SE: the laser doping method is adopted, namely heavy doping is carried out on the contact part of the metal grid line (electrode) and the silicon wafer, and light doping is carried out on the position between the electrodes.

4) Etching: by HNO₃And polishing the back surface of the silicon wafer with HF solution, and removing the phosphorosilicate glass layer on the front surface.

5) Annealing: and annealing the etched silicon wafer, and depositing a silicon dioxide layer on the surface of the silicon wafer.

6) Back passivation: and depositing an aluminum oxide and silicon nitride passivation film layer on the back of the silicon wafer in an ALD (atomic layer deposition) or PECVD (plasma enhanced chemical vapor deposition) mode.

7) Film preparation: and growing and depositing a silicon nitride film on the front surface of the silicon wafer.

8) Laser grooving: and carrying out laser grooving on the back of the coated silicon wafer.

9) Printing and sintering: and (4) finishing back and front printing through screen printing, and then performing a sintering process.

10) Electric injection: and performing electric injection through the light attenuation furnace or the electric injection furnace.

11) Testing and sorting: and finally, performing battery test grading on the battery piece.

The embodiments are described in a progressive manner in the specification, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description. It should be noted that, for those skilled in the art, it is possible to make several improvements and modifications to the present application without departing from the principle of the present application, and such improvements and modifications also fall within the scope of the claims of the present application.

It is further noted that, in the present specification, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.