Orientation-regulated contact passivation crystalline silicon solar cell and preparation method thereof

Abstract

The invention discloses a contact passivation crystalline silicon solar cell with orientation regulation and control. The contact passivation crystalline silicon solar cell comprises a silicon substrate, a silicon oxide tunneling contact growing in a vertical orientation mode is deposited on the back face of the silicon substrate. The invention further discloses a preparation method of the crystalline silicon solar cell, the preparation method comprises a process of depositing silicon oxide tunneling contact growing in a vertical orientation mode on the back face of the silicon substrate, and the process specifically comprises the following steps that 1, impurity removal and hydroxylation treatment are conducted on the back face of the silicon substrate in sequence; 2, preparing a precursor sol based on an organosilicon compound or an inorganic silicon compound, and coating the precursor sol on the back surface of the silicon substrate by spin coating, spray coating, brush coating or roller coating; and step 3, reacting in a constant-temperature and constant-humidity environment, heating after the reaction, removing by-products generated by hydrolysis, and obtaining high-crystallinity silicon oxide tunneling contact growing along the vertical direction on the back surface of the silicon substrate.

Description

Technical Field

[0001] The present invention relates to a crystalline silicon solar cell and also to a method for preparing the crystalline silicon solar cell. Background Art

[0002] Tunneling oxide passivation contact (TOPCon) technology is a solar cell technology based on the principle of selective carriers. It is the third generation of solar cell technology after back surface field (BSF) technology and passivated emitter and back contact (PERC) technology. Tunneling oxide passivation contact (TOPCon) technology inserts an ultra-thin SiO2 layer between crystalline silicon (c-Si) and doped contact. x layer (1-2nm), which can effectively reduce surface recombination and metal contact recombination.

[0003] However, most existing tunnel oxide contact technologies are based on the preparation of hydrogenated amorphous SiO on crystalline silicon (c-Si) by chemical vapor deposition (CVD). x (a-SiO x :H) nanolayer, hydrogenated amorphous SiO prepared by the above process x (a-SiO x :H) The nanolayer has many holes, many defects, and low charge mobility, which leads to the loss of photoelectric conversion efficiency of TOPCon solar cells. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a crystalline silicon solar cell with high photoelectric conversion efficiency; another purpose of the present invention is to provide a method for preparing the above-mentioned crystalline silicon solar cell.

[0005] Technical solution: The crystalline silicon solar cell described in the present invention comprises a silicon substrate; a vertically oriented silicon oxide tunneling contact is deposited on the back of the silicon substrate.

[0006] Wherein, the thickness of the silicon oxide tunneling contact is not higher than 1.5 nm.

[0007] The crystalline silicon solar cell further comprises a p-type emitter, an aluminum oxide layer and a silicon nitride layer sequentially deposited on the front side of the silicon substrate; and an n-type polysilicon layer and a silicon nitride layer sequentially deposited on the silicon oxide tunneling contact on the back side of the silicon substrate; and metal electrodes are printed on the silicon nitride layers on both sides.

[0008] The method for preparing the crystalline silicon solar cell comprises a process for depositing a vertically oriented silicon oxide tunneling contact on the back of a silicon substrate. The process specifically comprises the following steps:

[0009] Step 1, performing de-doping and hydroxylation treatments on the back side of the silicon substrate in sequence;

[0010] Step 2, preparing a precursor sol based on an organic silicon compound or an inorganic silicon compound, and spin coating, spray coating, brush coating or roller coating the precursor sol on the back side of a silicon substrate;

[0011] Step 3, reacting in a constant temperature and humidity environment, heating after the reaction, removing by-products produced by hydrolysis, and obtaining a high-crystallinity silicon oxide tunnel contact grown in a vertical direction on the back side of the silicon substrate.

[0012] Wherein, in step 1, the back side of the silicon substrate is subjected to de-doping and hydroxylation treatments in sequence, specifically: the back side of the silicon substrate is plasma cleaned for 3 to 4 minutes, and then immersed in an alkaline solution with a pH of 8 to 10 for 2 to 3 minutes.

[0013] Wherein, in step 2, the precursor sol is prepared by dissolving an organic silicon compound or an inorganic silicon compound in anhydrous ethanol, and the concentration of the organic silicon compound or the inorganic silicon compound in the precursor sol is 5 to 6 μL / mL.

[0014] Wherein, the organic silicon compound or inorganic silicon compound is TEOS (tetraethyl silicate), butyl orthosilicate or silicon tetrachloride.

[0015] Wherein, in step 2, the precursor sol is spin-coated onto the back side of the silicon substrate, specifically, the precursor sol is dropped onto the back side of the silicon substrate, and the precursor sol is first spin-coated at a low speed, and then spin-coated at a high speed.

[0016] The low-speed spin coating refers to spin coating at a rotation speed of 500 to 1000 r / min for 15 to 18 s; the high-speed spin coating refers to spin coating at a rotation speed of not less than 2000 r / min for 55 to 60 s.

[0017] Wherein, in step 3, during the reaction, the ambient humidity is not less than 50%; and the heating temperature after the reaction is not less than 100°C.

[0018] The organosilicon compound or inorganic silicon compound undergoes a condensation reaction with the hydroxyl groups on the surface of crystalline silicon, so that the organosilicon compound or inorganic silicon compound molecules are grafted onto the surface of crystalline silicon. The organosilicon compound or inorganic silicon compound grafted onto the surface of crystalline silicon undergoes a hydrolysis reaction with water molecules in the environment, and then undergoes a condensation reaction with other organosilicon compound or inorganic silicon compound molecules. As the hydrolysis-condensation chain reaction occurs, the silicon-oxygen chain continues to extend, and finally a silicon oxide tunneling contact with high crystallinity and low resistance is obtained that grows in a vertical direction. The ethanol byproduct produced by the hydrolysis is then completely evaporated by heating.

[0019] Organic silicon compound or inorganic silicon compound molecules react with hydroxyl groups on the surface of silicon wafers to form a condensation reaction. Taking TEOS as an example, the reaction equation is as follows:

[0020]

[0021] The spin-coated sample is placed in an air environment and allowed to stand for a period of time. After continuous hydrolysis and condensation chain reactions, the silicon-oxygen chain grows and extends. The reaction equation is as follows:

[0022]

[0023] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: the present invention optimizes SiO x The crystal structure of the tunneling contact can effectively solve the existing hydrogenated amorphous SiO x The nanolayer has multiple holes, multiple defects, and low charge mobility. The method of the present invention can prepare uniform and directional (vertically oriented) SiO2 on the back of the silicon substrate. x (v-SiO x ) polycrystalline tunnel passivation contact, so that the silicon oxide tunnel contact has good uniformity and density at a low thickness (no more than 1.5nm), thereby effectively improving its electron transmission efficiency, reducing current loss, and reducing the recombination of electrons and holes, thereby effectively improving the photoelectric conversion efficiency of TOPCon solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 For traditional SiO x Schematic diagram of the structure of a TOPCon solar cell with tunneling contact;

[0025] Figure 2 The v-SiO prepared in Example 1 x Schematic diagram of the structure of a TOPCon solar cell with polycrystalline tunneling contact;

[0026] Figure 3 For existing SiO x Scanning electron microscope photos and high-resolution transmission electron microscope FFT images of tunneling contacts;

[0027] Figure 4 For existing SiO x High-resolution transmission electron microscopy image of the tunneling contact;

[0028] Figure 5 The v-SiO prepared in Example 1 x Scanning electron microscope photos and high-resolution transmission electron microscope FFT images of polycrystalline tunneling contacts;

[0029] Figure 6 The v-SiO prepared in Example 1 x High-resolution transmission electron microscopy image of a polycrystalline tunneling contact;

[0030] Figure 7 For existing SiO xConductive atomic force microscopy image of a tunneling contact;

[0031] Figure 8 The v-SiO prepared in Example 1 x Conductive atomic force microscopy images of polycrystalline tunneling contacts;

[0032] Fig. 9 For traditional SiO x Output characteristics of TOPCon solar cell junction with tunneling contact;

[0033] Fig.10 The v-SiO prepared in Example 1 x Output characteristics of TOPCon solar cell junction with polycrystalline tunneling contact;

[0034] Fig.11 The v-SiO prepared in Example 2 x Scanning electron microscope image of a polycrystalline tunneling contact;

[0035] Fig.12 The v-SiO prepared in Example 3 x Scanning electron microscope image of a polycrystalline tunneling contact;

[0036] Among them, there are silicon base layer 1; p-type emitter 2; aluminum oxide layer 3; silicon nitride layer 4; existing amorphous silicon oxide tunneling contact 5-1; directionally grown polycrystalline silicon oxide tunneling contact 5; n-type polysilicon layer 6; and metal electrode 7. DETAILED DESCRIPTION

[0037] like Figure 1 As shown, traditional SiO x The TOPCon solar cell with tunneling contact comprises a silicon substrate 1; a p-type emitter 2, an aluminum oxide layer 3 and a silicon nitride layer 4 are sequentially deposited on the front side of the silicon substrate 1; and disordered hydrogenated amorphous SiO x (a-SiO x :H) nano layer 5-1, n-type polysilicon layer 6 and silicon nitride layer 4; metal electrodes 7 are printed on the silicon nitride layer 4 on both sides of the silicon substrate 1.

[0038] like Figure 2 As shown, the TOPCon solar cell of the present invention comprises a silicon substrate 1; a p-type emitter 2, an aluminum oxide layer 3 and a silicon nitride layer 4 are sequentially deposited on the front side of the silicon substrate 1; a high-crystallinity and vertically oriented silicon oxide tunneling contact 5, an n-type polysilicon layer 6 and a silicon nitride layer 4 are sequentially deposited on the back side of the silicon substrate 1; metal electrodes 7 are printed on the silicon nitride layers 4 on both sides of the silicon substrate 1.

[0039] The TOPCon solar cell is prepared by the following method, and the specific steps are as follows:

[0040] Step 1, the silicon substrate is selected from an n-type Cz single crystal silicon wafer with a thickness of 120 μm and a size of M6 (166×166 mm±0.25), a (100) orientation, and a resistivity of less than 1.0 Ω·cm, and is cleaned by an RCA standard cleaning method and texturing is performed in a texturing liquid to reduce front light reflection; it is soaked and washed with a large amount of clean water to obtain a silicon substrate 1 after texturing;

[0041] Step 2, using BCl3 to diffuse boron on the light-trapped surface of the silicon wafer pyramid, diffusing for 120 minutes at 1100°C to form a p-type emitter 2, and the diffusion depth of the p-type emitter 2 is 35nm; using a pulsed laser to selectively heavily dope the surface of the diffused p-type emitter 2 to form a heavily doped area;

[0042] Step 3, etching the silicon wafer with a mixed solution consisting of HNO3 solution, HF solution and water to remove the BSG on the back and sides, and then using an alkaline etchant to remove the pn junction on the back and sides;

[0043] Step 4, using the sol substrate induction method to prepare a vertically oriented silicon oxide tunneling contact 5: first plasma clean the back of the silicon wafer for 3 minutes, and then soak it in an alkaline solution with a pH of 8 to 10 for 2 minutes; use a pipette to absorb 50 μL of TEOS and dissolve it in 10 mL of anhydrous ethanol, and stir it continuously for 10 minutes to prepare a precursor sol; then vacuum adsorb the dried silicon wafer into a glue spreader, use a dropper to absorb the precursor sol and drop it on the back of the silicon wafer, first spin-coat it at a low speed of 500 r / min for 18 seconds, and then spin-coat it at a high speed of 2000 r / min for 60 seconds, and the TEOS molecules react with the surface of the silicon wafer. The reaction equation is as follows:

[0044]

[0045] The spin-coated sample was placed in an air environment with a humidity of not less than 50% for 10 minutes. After continuous hydrolysis and condensation chain reactions, the silicon-oxygen chain grew and extended. The reaction equation is as follows:

[0046]

[0047] The sample that has completed the chain reaction is transferred to a constant temperature heating table, and the temperature is gradually raised to 100° C. and maintained for 5 minutes to remove the ethanol byproducts produced by the hydrolysis and condensation chain reactions, thereby obtaining a directionally grown silicon oxide tunneling contact 5; the silicon oxide tunneling contact 5 obtained in Example 1 of the present invention is a polycrystalline nanolayer grown in a vertical direction, with a thickness of about 1.5 nm;

[0048] Step 5, using SiH4, PH3 and N2 as source gases, PECVD is used to deposit an n-type polysilicon layer 6 on the silicon oxide tunneling contact 5, the RF power is 50W, the temperature is 400°C, the deposition time is 40min to form an n-type polysilicon layer 6 with a thickness of about 100nm, and annealing is performed at 600-800°C;

[0049] Step 6, using an alkaline etching solution to remove the n-type polysilicon layer on the front and side surfaces, using trimethylaluminum and water as Al source and O source respectively, and using the ALD method to deposit an aluminum oxide layer 3 on the p-type emitter 2: depositing an aluminum oxide film with a thickness of about 3 nm at 150° C.;

[0050] Step 7, transfer the silicon wafer to a PECVD environment, introduce SiH4 and NH3 at a flow ratio of 1:5, deposit for 4 minutes at 50W RF, then gradually change the flow ratio to 1:10, deposit for 8 minutes, and form a silicon nitride layer 4 with a thickness of about 80nm;

[0051] Step 8, before metallization, using an ultraviolet pulse laser with a wavelength of 355 nm, a PWM accuracy of 10 ps, ​​a frequency of 1 MHz, and a size of 40 μm×40 μm, to etch the silicon nitride layer 4 at a speed of 10000 mm / s;

[0052] Step 9, screen-printing silver paste on the front and back sides of the silicon wafer respectively, and then rapidly firing at 760° C. to form metal electrodes 7 .

[0053] Scanning electron microscope and high-resolution transmission microscope observations show that the conventional silicon oxide tunneling contact 5-1 is amorphous and has many holes and defects, such as Figures 3-4 As shown; the silicon oxide tunneling contact 5 prepared by Example 1 is polycrystalline, with few grain boundaries and defects in the vertical direction. Figures 5-6 As shown; in addition, the characterization of conductive atomic force microscopy proves that the longitudinal conductivity of the conventional silicon oxide tunneling contact 5-1 is much lower than the longitudinal conductivity of the silicon oxide tunneling contact 5 obtained in Example 1, as shown in FIG. Figures 7-8 shown.

[0054] From the performance test, it was found that the photoelectric conversion efficiency of TOPCon solar cells using traditional amorphous silicon oxide tunneling contacts is about 25.77% ( Fig. 9 ), while the photoelectric conversion efficiency of the TOPCon solar cell with vertical polycrystalline silicon oxide tunneling contact prepared in Example 1 is 26.01% ( Fig.10 ), and obtained a high open circuit voltage of 746 mV and a high current density of 41.54 mA cm-2, indicating that it has small current loss and large electron transfer efficiency.

[0055] Example 2

[0056] The only difference between Example 2 and Example 1 is that in step 4: the precursor sol is roller-coated on the back of the silicon substrate, specifically:

[0057] Step 1, the silicon substrate is selected from an n-type Cz single crystal silicon wafer with a thickness of 120 μm and a size of M6 (166×166 mm±0.25), a (100) orientation, and a resistivity of less than 1.0 Ω·cm, and is cleaned by an RCA standard cleaning method and texturing is performed in a texturing liquid to reduce front light reflection; it is soaked and washed with a large amount of clean water to obtain a silicon substrate 1 after texturing;

[0058] Step 2, using BCl3 to diffuse boron on the light-trapped surface of the silicon wafer pyramid, diffusing for 120 minutes at 1100°C to form a p-type emitter 2, and the diffusion depth of the p-type emitter 2 is 35nm; using a pulsed laser to selectively heavily dope the surface of the diffused p-type emitter 2 to form a heavily doped area;

[0059] Step 3, etching the silicon wafer with a mixed solution consisting of HNO3 solution, HF solution and water to remove the BSG on the back and sides, and then using an alkaline etchant to remove the pn junction on the back and sides;

[0060] Step 4, using the sol substrate induction method to prepare a vertically oriented silicon oxide tunneling contact 5: first plasma clean the back of the silicon wafer for 3 minutes, and then soak it in an alkaline solution with a pH of 8 to 10 for 2 minutes; use a pipette to absorb 500 μL of TEOS and dissolve it in 100 mL of anhydrous ethanol, and stir it continuously for 10 minutes to prepare a precursor sol; filter the precursor sol and evenly adhere it to the coating roller, fix the dried silicon wafer on the operating table, use the coating roller with the precursor sol to apply it to the back of the silicon wafer (0.5 to 10 m / min), and use a high-speed inert air knife (50 to 100 m / s) to reduce the film to a thickness of 1.5 nm; TEOS molecules undergo a condensation reaction with the surface of the silicon wafer, and the reaction equation is as follows:

[0061]

[0062] The sample was placed in an air environment with a humidity of not less than 50% for 10 minutes. After a hydrolysis-condensation chain reaction, the silicon-oxygen chain grew and extended. The reaction equation is as follows:

[0063]

[0064] The sample that has completed the chain reaction is transferred to a constant temperature heating table, and the temperature is gradually raised to 100° C. and maintained for 5 minutes to remove the ethanol byproducts produced by the hydrolysis and condensation chain reactions, thereby obtaining a directionally grown silicon oxide tunneling contact 5; the silicon oxide tunneling contact 5 obtained in Example 2 of the present invention is a polycrystalline nanolayer grown in a vertical direction, with a thickness of about 1.5 nm;

[0065] Step 5, using SiH4, PH3 and N2 as source gases, PECVD is used to deposit an n-type polysilicon layer 6 on the silicon oxide tunneling contact 5, the RF power is 50W, the temperature is 400°C, the deposition time is 40min to form an n-type polysilicon layer 6 with a thickness of about 100nm, and annealing is performed at 600-800°C;

[0066] Step 6, using an alkaline etching solution to remove the n-type polysilicon layer on the front and side surfaces, using trimethylaluminum and water as Al source and O source respectively, and using the ALD method to deposit an aluminum oxide layer 3 on the p-type emitter 2: depositing an aluminum oxide film with a thickness of about 3 nm at 150° C.;

[0067] Step 7, transfer the silicon wafer to a PECVD environment, introduce SiH4 and NH3 at a flow ratio of 1:5, deposit for 4 minutes at 50W RF, then gradually change the flow ratio to 1:10, deposit for 8 minutes, and form a silicon nitride layer 4 with a thickness of about 80nm;

[0068] Step 8, before metallization, using an ultraviolet pulse laser with a wavelength of 355 nm, a PWM accuracy of 10 ps, ​​a frequency of 1 MHz, and a size of 40 μm×40 μm, to etch the silicon nitride layer 4 at a speed of 10000 mm / s;

[0069] Step 9, screen-printing silver paste on the front and back sides of the silicon wafer respectively, and then rapidly firing at 760° C. to form metal electrodes 7 .

[0070] Scanning electron microscope observations show that the silicon oxide tunneling contact 5 prepared in Example 2 has nano-scale defects and pinholes on its surface, and its uniformity and compactness are not as good as those of the spin coating method used in Example 1. Fig.11 Therefore, the photoelectric conversion efficiency of the TOPCon solar cell with vertical polycrystalline silicon oxide tunneling contact prepared in Example 2 is 25.80%.

[0071] Example 3

[0072] The only difference between Example 3 and Example 1 is that in step 4: the precursor sol is sprayed onto the back of the silicon substrate, specifically:

[0073] Step 1, the silicon substrate is selected from an n-type Cz single crystal silicon wafer with a thickness of 120 μm and a size of M6 (166×166 mm±0.25), a (100) orientation, and a resistivity of less than 1.0 Ω·cm, and is cleaned by an RCA standard cleaning method and texturing is performed in a texturing liquid to reduce front light reflection; it is soaked and washed with a large amount of clean water to obtain a silicon substrate 1 after texturing;

[0074] Step 2, using BCl3 to diffuse boron on the light-trapped surface of the silicon wafer pyramid, diffusing for 120 minutes at 1100°C to form a p-type emitter 2, and the diffusion depth of the p-type emitter 2 is 35nm; using a pulsed laser to selectively heavily dope the surface of the diffused p-type emitter 2 to form a heavily doped area;

[0075] Step 3, etching the silicon wafer with a mixed solution consisting of HNO3 solution, HF solution and water to remove the BSG on the back and sides, and then using an alkaline etchant to remove the pn junction on the back and sides;

[0076] Step 4, using the sol substrate induction method to prepare a vertically oriented silicon oxide tunneling contact 5: first plasma clean the back of the silicon wafer for 3 minutes, and then soak it in an alkaline solution with a pH of 8 to 10 for 2 minutes; use a pipette to absorb 50 μL of TEOS and dissolve it in 10 mL of anhydrous ethanol, and stir it continuously for 10 minutes to prepare a precursor sol; then put the precursor sol in a spray gun, connect it to high-pressure nitrogen, adjust the spray gun pressure to 0.1 to 0.2 MPa, and evenly spray the sol on the back of the soaked and dried silicon wafer, and use a high-speed inert air knife (50 to 80 m / s) to reduce the film layer to a thickness of 1.5 nm; TEOS molecules undergo a condensation reaction with the surface of the silicon wafer, and the reaction equation is as follows:

[0077]

[0078] The evenly coated sample is placed in an air environment with a humidity of not less than 50% for 10 minutes. After the hydrolysis-condensation chain reaction, the silicon-oxygen chain grows and extends. The reaction equation is as follows:

[0079]

[0080] The sample that has completed the chain reaction is transferred to a constant temperature heating table, and the temperature is gradually raised to 100° C. and maintained for 5 minutes to remove the ethanol byproducts produced by the hydrolysis and condensation chain reactions, thereby obtaining a directionally grown silicon oxide tunneling contact 5; the silicon oxide tunneling contact 5 obtained in Example 3 of the present invention is a polycrystalline nanolayer grown in a vertical direction, with a thickness of about 1.5 nm;

[0081] Step 5, using SiH4, PH3 and N2 as source gases, PECVD is used to deposit an n-type polysilicon layer 6 on the silicon oxide tunneling contact 5, the RF power is 50W, the temperature is 400°C, the deposition time is 40min to form an n-type polysilicon layer 6 with a thickness of about 100nm, and annealing is performed at 600-800°C;

[0082] Step 6, using an alkaline etching solution to remove the n-type polysilicon layer on the front and side surfaces, using trimethylaluminum and water as Al source and O source respectively, and using the ALD method to deposit an aluminum oxide layer 3 on the p-type emitter 2: depositing an aluminum oxide film with a thickness of about 3 nm at 150° C.;

[0083] Step 7, transfer the silicon wafer to a PECVD environment, introduce SiH4 and NH3 at a flow ratio of 1:5, deposit for 4 minutes at 50W RF, then gradually change the flow ratio to 1:10, deposit for 8 minutes, and form a silicon nitride layer 4 with a thickness of about 80nm;

[0084] Step 8, before metallization, using an ultraviolet pulse laser with a wavelength of 355 nm, a PWM accuracy of 10 ps, ​​a frequency of 1 MHz, and a size of 40 μm×40 μm, to etch the silicon nitride layer 4 at a speed of 10000 mm / s;

[0085] Step 9, screen-printing silver paste on the front and back sides of the silicon wafer respectively, and then rapidly firing at 760° C. to form metal electrodes 7 .

[0086] Scanning electron microscope observation shows that the silicon oxide tunneling contact 5 prepared in Example 3 is uniform and dense, but there are a certain number of nanocrystalline particles on the surface, such as Fig.12 Therefore, the photoelectric conversion efficiency of the TOPCon solar cell with vertical polycrystalline silicon oxide tunneling contact prepared in Example 3 is 25.97%.

[0087] Example 4

[0088] The only difference between Example 4 and Example 1 is that an equal amount of silicon tetrachloride (SiCl4) is used to replace TEOS in step 4. The photoelectric conversion efficiency of the TOPCon solar cell prepared in Example 4 is 25.94%.

[0089] Example 5

[0090] The only difference between Example 5 and Example 1 is that an equal amount of butyl orthosilicate is used to replace TEOS in step 4. The photoelectric conversion efficiency of the TOPCon solar cell prepared in Example 5 is 25.88%.

[0091] Comparative Example 1

[0092] Comparative Example 1 is different from Example 1 only in that in step 4, the back of the silicon wafer is directly dried after plasma cleaning for 3 minutes, without being immersed in alkaline solution; specifically, the back of the silicon wafer is plasma cleaned for 3 minutes; 50 μL TEOS is taken with a pipette and dissolved in 10 mL anhydrous ethanol, and stirred continuously for 10 minutes to prepare a precursor sol; then the dried silicon wafer is vacuum adsorbed in a sizing machine, and the precursor sol is taken with a dropper and dripped on the back of the silicon wafer, and first spin-coated at a low speed of 500 r / min for 18 seconds, and then spin-coated at a high speed of 2000 r / min for 60 seconds. The photoelectric conversion efficiency of the TOPCon solar cell prepared in Comparative Example 1 is 25.79%.

[0093] Comparative Example 2

[0094] The only difference between Comparative Example 2 and Example 1 is that in step 4, the spin-coated sample is placed in an air environment with a humidity of 10-20% for 10 minutes. The photoelectric conversion efficiency of the TOPCon solar cell prepared in Comparative Example 2 is 25.78%.

[0095] Comparative Example 3

[0096] The only difference between Comparative Example 3 and Example 1 is that in step 4, the dried silicon wafer is vacuum adsorbed in a coating machine, and the precursor sol is dripped on the back of the silicon wafer with a dropper during the high-speed spin coating process of 2000 r / min, and the high speed of 2000 r / min is maintained for 60 seconds. The photoelectric conversion efficiency of the TOPCon solar cell prepared in Comparative Example 3 is 25.63%.

[0097] The method of the present invention uses a c-Si substrate as a template and grows a high-crystallinity, vertically oriented SiO2 on the c-Si surface through a hydrolysis-condensation chain reaction of an organic silicon compound or an inorganic silicon compound (especially TEOS). x (v-SiO x ) Polycrystalline tunneling passivation contact results in fewer grain boundaries, fewer defects, and lower resistance in the vertical direction, thereby effectively improving electron transmission efficiency, reducing current loss, and further improving the photoelectric conversion efficiency of TOPCon solar cells.

Claims

1. An orientation-controlled contact-passivated crystalline silicon solar cell, comprising a silicon substrate (1); characterized in that: A vertically oriented silicon oxide tunneling contact (5) is deposited on the back side of the silicon substrate (1).

2. The orientation-controlled contact-passivated crystalline silicon solar cell according to claim 1, characterized in that: The thickness of the silicon oxide tunneling contact (5) is 1-1.5 nm.

3. The orientation-controlled contact-passivated crystalline silicon solar cell according to claim 1, characterized in that: The crystalline silicon solar cell further comprises a p-type emitter (2), an aluminum oxide layer (3) and a silicon nitride layer (4) deposited in sequence on the front side of a silicon substrate (1); and an n-type polycrystalline silicon layer (6) and a silicon nitride layer (4) deposited in sequence on a silicon oxide tunneling contact (5) on the back side of the silicon substrate (1); and metal electrodes (7) are printed on the silicon nitride layers (4) on both sides.

4. The method for preparing a contact passivated crystalline silicon solar cell according to claim 1, characterized in that: The process includes depositing a vertically oriented growth silicon oxide tunneling contact on the back of a silicon substrate, and the process specifically includes the following steps: Step 1, performing de-doping and hydroxylation treatments on the back side of the silicon substrate in sequence; Step 2, preparing a precursor sol based on an organic silicon compound or an inorganic silicon compound, and spin coating, spray coating, brush coating or roller coating the precursor sol on the back side of a silicon substrate; Step 3, reacting in a constant temperature and humidity environment, and heating after the reaction to obtain a high-crystallinity silicon oxide tunnel contact grown in a vertical direction on the back side of the silicon substrate.

5. The preparation method according to claim 4, characterized in that: In step 1, the back side of the silicon substrate is subjected to de-doping and hydroxylation treatments in sequence, specifically, the back side of the silicon substrate is plasma cleaned for 3 to 4 minutes, and then immersed in an alkaline solution with a pH of 8 to 10 for 2 to 3 minutes.

6. The preparation method according to claim 4, characterized in that: In step 2, the precursor sol is prepared by dissolving an organic silicon compound or an inorganic silicon compound in anhydrous ethanol. In the precursor sol, the concentration of the organic silicon compound or the inorganic silicon compound is 5 to 6 μL / mL.

7. The preparation method according to claim 6, characterized in that: The organic silicon compound or inorganic silicon compound is TEOS, butyl orthosilicate or silicon tetrachloride.

8. The preparation method according to claim 4, characterized in that: In step 2, the precursor sol is spin-coated onto the back side of the silicon substrate, specifically, the precursor sol is dropped onto the back side of the silicon substrate, and the precursor sol is first spin-coated at a low speed, and then spin-coated at a high speed.

9. The preparation method according to claim 8, characterized in that: The low-speed spin coating refers to spin coating at a rotation speed of 500 to 1000 r / min for 15 to 18 s; the high-speed spin coating refers to spin coating at a rotation speed of not less than 2000 r / min for 55 to 60 s.

10. The preparation method according to claim 4, characterized in that: In step 3, during the reaction, the ambient humidity is not less than 50%; and the heating temperature after the reaction is not less than 100°C.

Images