Functional polycrystalline silicon tunnel oxide passivated contact structure and preparation method therefor

Abstract

Provided in the present invention are a functional polycrystalline silicon tunnel oxide passivated contact structure (TOPCon) and a preparation method therefor. The functional polycrystalline silicon tunnel oxide passivated contact structure comprises a crystalline silicon substrate, nano silicon oxide and a functional polycrystalline silicon structure which are arranged in a stacked manner in sequence, wherein the functional polycrystalline silicon structure is composed of a carbon and nitrogen co-doped polycrystalline silicon layer, or is formed by means of the alternate lamination of a carbon-doped polycrystalline silicon layer and a nitrogen-doped polycrystalline silicon layer. In the present invention, new polycrystalline silicons having different functions, namely carbon-doped polycrystalline silicon, nitrogen-doped polycrystalline silicon and carbon and nitrogen co-doped polycrystalline silicon, are prepared by utilizing doping engineering, and a functional polycrystalline silicon structure is formed and exerts different functions of carbon- and nitrogen-doped atoms, and also achieves internal passivation and surface passivation of a silicon wafer, thereby further obtaining a TOPCon structure having an ultra-high passivation performance. The structure has ultra-high minority carrier lifetime, an ultra-high implicit open-circuit voltage and an ultra-low surface recombination current, and can enhance the mechanical strength of the silicon wafer to a certain extent.

Description

A functional polysilicon tunneling silicon oxide passivation contact structure and its preparation method Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a functional polysilicon tunneling oxidation passivation contact structure and a preparation method thereof. Background Art

[0002] Tunneling oxide passivation contact (TOPCon) technology is a representative passivation contact technology. Its key feature is to grow an ultra-thin nano-silicon oxide (SiO) layer on the surface of the silicon wafer. x ) is used to eliminate dangling bonds on the surface by depositing a heavily doped polysilicon layer on ultra-thin silicon oxide to achieve a field passivation effect. Thanks to the excellent passivation performance of the TOPCon structure, the efficiency of mass-produced cells has now exceeded 25%. Coupled with the compatibility of production processes, the planned production capacity of TOPCon cells is currently increasing rapidly, and it has become the mainstream technology for industrial silicon cell expansion.

[0003] However, in terms of efficiency improvement, the current TOPCon technology has shown certain limitations. First, the passivation performance of the TOPCon structure based on conventional polycrystalline silicon is slightly inferior to that of another representative passivation contact technology - heterojunction (HJT). The passivation performance of the TOPCon structure needs to be further improved. Second, according to research, the silicon wafer thickness corresponding to the highest photoelectric conversion efficiency of crystalline silicon solar cells is about 110μm. When the silicon wafer thickness is thin, the cell performance is more sensitive to surface recombination, that is, it is more dependent on surface passivation. Therefore, how to further improve the surface passivation capability is an important direction for the development of TOPCon technology. In addition, studies have also shown that the improvement of silicon cell efficiency is limited by the quality of the silicon wafer, that is, the minority carrier lifetime. For example, the theoretical efficiency of a cell with a minority carrier lifetime of 15ms is at least 1% higher than that of a cell with a minority carrier lifetime of 4.5ms. Therefore, improving the minority carrier lifetime of the silicon wafer is also conducive to improving cell efficiency. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of the present invention is to develop a new tunneling oxide passivation contact structure that can simultaneously improve the surface passivation performance and minority carrier lifetime of silicon wafers.

[0005] To solve the above problems, the present invention provides a functional polysilicon tunneling silicon oxide passivation contact structure, comprising a crystalline silicon substrate, nano-silicon oxide and a functional polysilicon structure stacked in sequence, wherein the functional polysilicon structure is composed of a carbon and nitrogen co-doped polysilicon layer, or is composed of an alternating stack of carbon-doped polysilicon layers and nitrogen-doped polysilicon layers.

[0006] The present invention utilizes doping engineering to prepare new polysilicon with different functions, namely carbon-doped (C) polysilicon, nitrogen-doped (N) polysilicon and carbon and nitrogen co-doped polysilicon layers, and forms a functional polysilicon structure, which plays different functional roles of carbon and nitrogen doping atoms, and simultaneously realizes passivation in the silicon wafer body and surface, thereby obtaining a TOPCon structure with ultra-high passivation performance. This structure has an ultra-high minority carrier lifetime (τ eff ), implicit open circuit voltage (iV oc ) and ultra-low surface recombination current (J0), and can enhance the mechanical strength of the silicon wafer to a certain extent.

[0007] Furthermore, the functional polysilicon structure has active doping atoms, which are phosphorus or boron. Doping the polysilicon layer with n-type or p-type active doping atoms can achieve excellent field passivation effect.

[0008] Furthermore, the near-surface region of the crystalline silicon substrate close to the nano-silicon oxide contains nitrogen, carbon, hydrogen, phosphorus / boron elements, and the nitrogen concentration at the surface of the crystalline silicon substrate is higher than 1×10 20 cm -3 , the carbon concentration is higher than 1×10 20 cm -3 , the hydrogen concentration is higher than 1×10 19 cm -3 , the phosphorus concentration range is 1×10 17 ~5×10 20 cm -3 Or the boron concentration range is 0.5×10 17 ~1×10 20 cm -3 As the depth increases, the concentrations of nitrogen, carbon, hydrogen, phosphorus / boron elements in the crystalline silicon substrate gradually decrease.

[0009] Furthermore, the carbon atom doping concentration of the carbon and nitrogen co-doped polysilicon layer is 0.1at% to 50at%, the nitrogen atom doping concentration is 0.1at% to 50at%, the carbon atom doping concentration of the carbon-doped polysilicon layer is 0.1at% to 50at%, and the nitrogen atom doping concentration of the nitrogen-doped polysilicon layer is 0.1at% to 50at%.

[0010] Furthermore, the distribution form of carbon atoms and nitrogen atoms in the carbon and nitrogen co-doped polysilicon layer is uniform doping or gradient doping, the distribution form of carbon atoms in the carbon-doped polysilicon layer is uniform doping or gradient doping, and the distribution form of carbon atoms in the nitrogen-doped polysilicon layer is uniform doping or gradient doping.

[0011] Furthermore, the thickness of the carbon and nitrogen co-doped polysilicon layer is 1 nm to 2000 nm, the thickness of the carbon-doped polysilicon layer is 1 nm to 1000 nm, and the thickness of the nitrogen-doped polysilicon layer is 1 nm to 1000 nm.

[0012] The mechanism of action of the functional polysilicon structure is as follows: C atoms diffuse into the silicon wafer, where they effectively prevent the formation of cluster defects such as phosphorus and boron clusters. Furthermore, C atoms inhibit the formation of oxygen thermal donor defects or render them electrically inactive. Furthermore, C atoms have a strong ability to capture hydrogen atoms, so more H atoms in the silicon wafer can passivate more defects. Together, these mechanisms help reduce the density of defect states within the silicon wafer. N atoms also diffuse into the silicon wafer. N impurities within the silicon wafer effectively suppress the formation of vortex and D defects. Furthermore, N impurity atoms effectively pin dislocations, preventing them from moving, thereby improving the wafer's mechanical strength. N atoms also have a strong ability to capture H atoms, allowing more H atoms to remain in the silicon wafer to passivate defect states. More importantly, N atoms are enriched at the nano-silicon oxide interface, significantly increasing the concentration of H atoms there, thereby passivating more defect states and achieving a lower interface state density. In short, by using carbon and nitrogen co-doped polysilicon or C-doped and N-doped polysilicon stacked structures, the different functions of C and N atoms can be brought into play, while achieving passivation inside and on the surface of the silicon, reducing the recombination current, increasing the minority carrier lifetime, and improving the mechanical strength of the silicon wafer.

[0013] Furthermore, a conventional polysilicon layer is provided on the functional polysilicon structure, wherein the conventional polysilicon layer is made of polysilicon not doped with carbon or nitrogen. Adding another layer of conventional polysilicon on the carbon-doped and nitrogen-doped functional polysilicon structure can improve contact performance.

[0014] The present invention also provides a method for preparing the functional polysilicon tunneling silicon oxide passivation contact structure, comprising the following steps:

[0015] S1, cleaning the crystalline silicon substrate;

[0016] S2, depositing nano-silicon oxide on the surface of the crystalline silicon substrate;

[0017] S3, depositing a carbon and nitrogen co-doped amorphous silicon layer on the surface of the nano-silicon oxide, or depositing a carbon-doped amorphous silicon layer and a nitrogen-doped amorphous silicon layer in alternating layers;

[0018] S4. High-temperature annealing to crystallize the amorphous silicon, form a functional polysilicon junction, and push carbon atoms and nitrogen atoms into the crystalline silicon substrate.

[0019] Furthermore, in step S4, the high temperature annealing temperature is 800° C. to 1100° C. Selecting a suitable high temperature annealing temperature can activate the active dopants while pushing the C and N atoms of the functional polysilicon structure into the silicon body, thereby achieving simultaneous passivation of the body and the surface.

[0020] Furthermore, in step S3, an amorphous silicon layer is deposited in situ using PECVD. The functional polysilicon structure simultaneously introduces C and N atoms into the silicon body and increases the H content in the crystalline silicon body to reduce body defect states and increase body life.

[0021] In summary, the present invention has the following beneficial effects compared to the prior art:

[0022] (1) The present invention achieves good passivation in the silicon wafer. This is because C and N atoms will enter the silicon body. C atoms can effectively reduce the concentration of self-interstitial silicon atoms and avoid the formation of cluster defects. C atoms can also form CO complexes with O atoms to inhibit the formation of thermal donor defects. N atoms can effectively inhibit vortex defects and D defects in the body. . The generation of defects; in addition, C and N atoms have strong ability to capture H atoms, which can retain more H atoms in the silicon body, which is beneficial to defect passivation.

[0023] (2) The present invention achieves excellent passivation on the silicon wafer surface. Because nitrogen atoms are enriched at the ultrathin silicon oxide interface, the hydrogen content at the interface increases due to their excellent hydrogen trapping ability, which passivates more defect states and reduces the interface state density. Furthermore, the hydrogen content in C-doped and N-doped polysilicon is also increased, which is beneficial for surface passivation.

[0024] (3) The present invention combines C-doped and N-doped polysilicon to play different functional roles, while achieving both internal and surface passivation, thereby obtaining a TOPCon structure with ultra-high passivation performance. The implicit open-circuit voltage can reach 760mV, and the minority carrier lifetime can reach more than 20ms (110μm thick, 1-7Ω·cm resistivity n-type CZ silicon wafer substrate). This index is significantly higher than the highest index achievable by conventional polysilicon TOPCon structures.

[0025] (4) The present invention can also improve the mechanical strength of silicon wafers and reduce the risk of warping of thin silicon wafers after high-temperature treatment. This is because N atoms have a strong pinning ability for dislocations and can effectively prevent the movement of dislocations. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG1 is a schematic structural diagram of a functional polysilicon tunneling oxidation passivation contact structure in a specific embodiment of the present invention.

[0027] FIG2 is a schematic diagram of a process for preparing a functional polysilicon tunneling oxide passivation contact structure in a specific embodiment of the present invention.

[0028] FIG3 is a comparison diagram of the implicit open circuit voltage of the TOPCon structure of the embodiment of the present invention and the comparative example.

[0029] FIG4 is a comparison diagram of the single-sided composite current of the TOPCon structure of the embodiment of the present invention and the comparative example.

[0030] FIG5 is a comparison diagram of the minority carrier lifetime and SRH recombination current of the TOPCon structure of the embodiment of the present invention and the comparative example.

[0031] FIG6 is a comparison diagram of the interface state density distribution of the TOPCon structure of the embodiment of the present invention and the comparative example.

[0032] Description of reference numerals:

[0033] 1-crystalline silicon substrate, 2-nano silicon oxide, 3-first polysilicon layer, 4-second polysilicon layer, 5-internal diffusion layer, 6-passivation anti-reflection layer. DETAILED DESCRIPTION

[0034] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. It should be noted that the following embodiments are only intended to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter ranges described in the present invention. Reasonable variations derived therefrom are still within the scope of protection of the claims of the present invention.

[0035] It should be noted that the endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

[0036] A specific embodiment of the present invention provides a functional polysilicon tunneling silicon oxide passivation contact structure, comprising a crystalline silicon substrate, nano-silicon oxide and a functional polysilicon structure stacked in sequence, wherein the functional polysilicon structure is composed of a carbon and nitrogen co-doped polysilicon layer, or is composed of an alternating stack of carbon-doped polysilicon layers and nitrogen-doped polysilicon layers.

[0037] A typical structure of a functional polysilicon tunneling silicon oxide passivation contact structure is shown in Figure 1, comprising a crystalline silicon substrate 1, nano-silicon oxide 2, a first polysilicon layer 3, and a second polysilicon layer 4. The first polysilicon layer 3 and the second polysilicon layer 4 constitute the functional polysilicon structure. The first polysilicon layer 3 is made of carbon-doped / nitrogen-doped polysilicon, and the second polysilicon layer 4 is made of nitrogen-doped / carbon-doped polysilicon. The distribution of carbon atoms or nitrogen atoms in the two polysilicon layers is either uniformly doped or gradient-doped. The carbon-doped polysilicon and nitrogen-doped polysilicon form a stacked structure, where the carbon and nitrogen-doped atoms play different functional roles, enabling simultaneous passivation of the silicon wafer both internally and on its surface, thereby achieving a TOPCon structure with ultra-high passivation performance and enhancing the mechanical strength of the silicon wafer to a certain extent.

[0038] In a specific embodiment, the crystalline silicon substrate 1 is n-type or p-type crystalline silicon. The thickness of the nano-silicon oxide 2 is less than 3 nm, and is used to eliminate surface dangling bonds and provide good chemical passivation.

[0039] In a specific embodiment, the doping concentration of carbon atoms / nitrogen atoms in the first polysilicon layer 3 is 0.1 at% to 50 at%, and the doping concentration of nitrogen atoms / carbon atoms in the second polysilicon layer 4 is 0.1 at% to 50 at%. The thickness of the first polysilicon layer 3 is 1 nm to 1000 nm, and the thickness of the second polysilicon layer 4 is 1 nm to 1000 nm. The first polysilicon layer 3 and the second polysilicon layer 4 contain active doping atoms, typically boron, with a doping concentration range of 1E17 to 5E20 cm -3 The typical n-type active dopant atom is phosphorus, with a doping concentration range of 1E18 to 1E21 cm -3 , which can achieve an excellent field passivation effect. Preferably, the material of the first polysilicon layer 3 is carbon-doped polysilicon, and the material of the second polysilicon layer 4 is nitrogen-doped polysilicon. A layer of conventional polysilicon without carbon / nitrogen doping can also be deposited on the second polysilicon layer 4 as a third polysilicon layer to improve contact performance. As shown in Figure 2, the typical preparation method of the above-mentioned functional polysilicon tunneling silicon oxide passivation contact structure includes the following steps:

[0040] S1. Perform standard RCA cleaning on the crystalline silicon substrate 1.

[0041] S2. PECVD is used to perform N2O plasma oxidation to deposit ultra-thin silicon oxide on the surface of the crystalline silicon substrate 1 to form nano-silicon oxide 2.

[0042] S3, using PECVD in-situ deposition to sequentially deposit a first polysilicon layer and a second amorphous silicon layer on the surface of the nano-silicon oxide 2.

[0043] S4. High temperature annealing, with a typical temperature range of 800°C to 1100°C, and a preferred temperature range of 900°C to 950°C, to crystallize the first polysilicon layer and the second amorphous silicon layer to form a first polysilicon layer 3 and a second polysilicon layer 4, activate active doping and push carbon atoms and nitrogen atoms into the crystalline silicon substrate 1, and form an inner diffusion layer 5 on the surface of the crystalline silicon substrate 1.

[0044] S5 , depositing aluminum oxide / silicon nitride / aluminum oxide on the second polysilicon layer 4 by using ALD and PECVD to form a passivation anti-reflection layer 6 .

[0045] The above preparation method can simultaneously introduce C and N atoms into the crystalline silicon body and increase the H content in the body, thereby reducing the defect states in the crystalline silicon body and improving the body life; N atoms are enriched in the ultra-thin silicon oxide during diffusion, thereby capturing more H atoms at the interface and reducing the interface state density; during the annealing process, the silicon body is slightly doped with N to improve the mechanical strength of the silicon wafer and avoid silicon wafer warping caused by uneven thermal stress. After diffusion, the near-surface area of ​​the crystalline silicon substrate 1 near the nano-silicon oxide 2 contains nitrogen, carbon, hydrogen, and phosphorus / boron elements. The concentration of each element gradually decreases with increasing depth. The nitrogen concentration on the surface of the crystalline silicon substrate 1 is higher than 1×10 20 cm -3 , which can usually exceed 1×10 21 cm -3 ; Carbon concentration is higher than 1×10 20 cm - 3 , which can usually exceed 1×10 21 cm -3 ; Hydrogen concentration is higher than 1×10 19 cm -3 , which can usually exceed 1×10 20 cm -3 , and the hydrogen concentration is correlated with the distribution of C and N elements. The doping depth of phosphorus / boron is usually between 10 and 1000 nm. By optimizing the annealing temperature and time, the doping depth can be controlled within 400 nm. Usually, the phosphorus concentration on the surface of the crystalline silicon substrate 1 is in the range of 1×10 17 ~5×10 20 cm -3 , the boron concentration range is 0.5×10 17 ~1×10 20 cm -3 .

[0046] The functional polysilicon tunneling silicon oxide passivation contact structure prepared has ultra-high passivation performance. For an n-type silicon wafer substrate with a thickness of 110um (resistivity 1-7Ωcm), its SRH composite current can be as low as 0.1fA / cm 2 Below, the single-sided recombination current can be as low as 0.6fA / cm2 Below this value, the minority carrier lifetime can reach more than 20ms.

[0047] The technical solutions and effects of the present invention are described below through specific embodiments.

[0048] Example 1

[0049] Prepare an N-type crystalline silicon substrate and perform standard RCA cleaning on the crystalline silicon substrate; use PECVD to deposit an ultra-thin silicon oxide layer with a thickness of 2 nm on the surface of the crystalline silicon substrate; use PECVD to deposit a carbon-doped amorphous silicon layer with a thickness of 100 nm and a carbon atom doping concentration of 5 at% on the surface of the ultra-thin silicon oxide layer; use PECVD to deposit a nitrogen-doped amorphous silicon layer with a thickness of 100 nm and a nitrogen atom doping concentration of 5 at% on the surface of the carbon-doped amorphous silicon layer; perform high-temperature annealing in a tubular annealing furnace at a temperature of 900°C for 30 minutes to form a carbon-doped polysilicon layer and a nitrogen-doped polysilicon layer; and deposit an aluminum oxide / silicon nitride / aluminum oxide layer on the nitrogen-doped polysilicon layer.

[0050] Example 2

[0051] Prepare an N-type crystalline silicon substrate and perform standard RCA cleaning on the crystalline silicon substrate; use PECVD to deposit an ultra-thin silicon oxide layer with a thickness of 2nm on the surface of the crystalline silicon substrate; use PECVD to deposit a first carbon-doped amorphous silicon layer with a thickness of 50nm and a carbon atom doping concentration of 5at% on the surface of the ultra-thin silicon oxide layer; use PECVD to deposit a first nitrogen-doped amorphous silicon layer with a thickness of 50nm and a nitrogen atom doping concentration of 5at% on the surface of the carbon-doped amorphous silicon layer; use PECVD to deposit a first nitrogen-doped amorphous silicon layer with a thickness of 50nm and a nitrogen atom doping concentration of 5at% on the surface of the carbon-doped amorphous silicon layer; A second carbon-doped amorphous silicon layer with a thickness of 50 nm and a carbon atom doping concentration of 5 at % is deposited on the surface of the amorphous silicon layer; a second nitrogen-doped amorphous silicon layer with a thickness of 50 nm and a nitrogen atom doping concentration of 5 at % is deposited on the surface of the carbon-doped amorphous silicon layer by PECVD; high-temperature annealing is performed in a tubular annealing furnace at a temperature of 950°C for 30 minutes to form an alternating stacked structure of carbon-doped polycrystalline silicon layers and nitrogen-doped polycrystalline silicon layers; and an aluminum oxide / silicon nitride / aluminum oxide layer is deposited on the nitrogen-doped polycrystalline silicon layer.

[0052] Example 3

[0053] Prepare an N-type crystalline silicon substrate and perform standard RCA cleaning on the crystalline silicon substrate; use PECVD to deposit an ultra-thin silicon oxide layer with a thickness of 2 nm on the surface of the crystalline silicon substrate; use PECVD to deposit a nitrogen-doped amorphous silicon layer with a thickness of 100 nm and a nitrogen atom doping concentration of 5 at% on the surface of the ultra-thin silicon oxide layer; use PECVD to deposit a carbon-doped amorphous silicon layer with a thickness of 100 nm and a carbon atom doping concentration of 5 at% on the surface of the nitrogen-doped amorphous silicon layer; perform high-temperature annealing in a tubular annealing furnace at a temperature of 900°C for 30 minutes to form a nitrogen-doped polysilicon layer and a carbon-doped polysilicon layer; and deposit an aluminum oxide / silicon nitride / aluminum oxide layer on the carbon-doped polysilicon layer.

[0054] Example 4

[0055] An N-type crystalline silicon substrate was prepared and subjected to standard RCA cleaning. An ultra-thin silicon oxide layer with a thickness of 2 nm was deposited on the surface of the crystalline silicon substrate using PECVD. A carbon and nitrogen co-doped amorphous silicon layer with a thickness of 300 nm and a doping concentration of 5 at% carbon atoms and 15 at% nitrogen atoms was deposited on the surface of the ultra-thin silicon oxide layer using PECVD. The layer was annealed at a high temperature of 1000°C for 30 minutes in a tubular annealing furnace to form a carbon and nitrogen co-doped amorphous silicon layer. An aluminum oxide / silicon nitride / aluminum oxide layer was deposited on the carbon and nitrogen co-doped amorphous silicon layer.

[0056] Comparative Example 1

[0057] Prepare an N-type crystalline silicon substrate and perform standard RCA cleaning on the crystalline silicon substrate; use PECVD to deposit an ultra-thin silicon oxide layer with a thickness of 2nm on the surface of the crystalline silicon substrate; use PECVD to deposit a carbon-doped amorphous silicon layer with a thickness of 200nm and a carbon atom doping concentration of 5at% on the surface of the ultra-thin silicon oxide layer; perform high-temperature annealing in a tubular annealing furnace at a temperature of 900°C for 30 minutes to form a carbon-doped polycrystalline silicon layer; and deposit an aluminum oxide / silicon nitride / aluminum oxide layer on the carbon-doped polycrystalline silicon layer.

[0058] Comparative Example 2

[0059] An N-type crystalline silicon substrate was prepared and subjected to standard RCA cleaning. A 2nm-thick ultrathin silicon oxide layer was deposited on the surface of the crystalline silicon substrate using PECVD. A 200nm-thick nitrogen-doped amorphous silicon layer with a nitrogen doping concentration of 5at% was deposited on the surface of the ultrathin silicon oxide layer using PECVD. The layer was annealed in a tubular annealing furnace at 900°C for 30 minutes to form a nitrogen-doped polysilicon layer. An aluminum oxide / silicon nitride / aluminum oxide layer was deposited on the nitrogen-doped polysilicon layer.

[0060] Comparative Example 3

[0061] Prepare an N-type crystalline silicon substrate and perform standard RCA cleaning on the crystalline silicon substrate; use PECVD to deposit an ultra-thin silicon oxide layer with a thickness of 2nm on the surface of the crystalline silicon substrate; use PECVD to deposit an amorphous silicon layer with a thickness of 200nm on the surface of the ultra-thin silicon oxide layer; perform high-temperature annealing in a tubular annealing furnace at a temperature of 900°C for 30 minutes to form a conventional polycrystalline silicon layer; and deposit an aluminum oxide / silicon nitride / aluminum oxide layer on the polycrystalline silicon layer.

[0062] The performance of the passivation sheets prepared in the above examples and comparative examples was tested. The implicit open circuit voltage (iV) of the sample in Example 1 and the samples in Comparative Examples 1-3 was oc As shown in Figure 3, the single-sided composite current J 0,s A comparison is shown in Figure 4, and a comparison of the minority carrier lifetime and SRH recombination current is shown in Figure 5. These results demonstrate that the TOPCon structure with carbon- and nitrogen-doped laminated polysilicon exhibits higher implicit open-circuit voltage, lower single-sided recombination current, higher minority carrier lifetime, and lower SRH recombination current than the TOPCon structure with single-layer carbon-doped polysilicon, nitrogen-doped polysilicon, or conventional polysilicon, demonstrating superior passivation performance. A comparison of the interface state density distribution of the sample from Example 1 and the sample from Comparative Example 3 is shown in Figure 6, demonstrating that carbon- and nitrogen-doped laminated polysilicon can reduce the interface state density, resulting in excellent passivation of the silicon wafer surface.

[0063] TOPCon cells were prepared using the methods of Examples 1-4 and Comparative Examples 1-3, and the performance of each cell was tested. The results are shown in Table 1. The results show that the functional polycrystalline silicon structure can improve the open circuit voltage, fill factor, and cell conversion efficiency of the TOPCon cell.

[0064] Table 1 Comparison of battery performance of Examples 1-3 and Comparative Examples 1-3

[0065] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined by the claims.

Claims

1. A multifunctional polysilicon tunneling silicon oxide passivation contact structure, characterized in that, It includes a crystalline silicon substrate, nano-silicon oxide, and a functional polysilicon structure that are sequentially stacked. The functional polysilicon structure is composed of a carbon and nitrogen co-doped polysilicon layer, or is composed of an alternately stacked carbon-doped polysilicon layer and a nitrogen-doped polysilicon layer.

2. The functional polysilicon tunneling silicon oxide passivation contact structure according to claim 1, wherein The functional polysilicon structure has active doping atoms, and the active doping atoms are phosphorus or boron.

3. [Corrected according to Rule 26 on 20.01.2025] The multi-functional polysilicon tunneling silicon oxide passivation contact structure according to claim 2, characterized in that, The near-surface region of the crystalline silicon substrate close to the nano-silicon oxide contains nitrogen, carbon, hydrogen, phosphorus / boron elements, and the nitrogen concentration in the surface part of the crystalline silicon substrate is higher than 1×10 20 cm -3 , the carbon concentration is higher than 1×10 20 cm -3 , the hydrogen concentration is higher than 1×10 19 cm -3 , the phosphorus concentration ranges from 1×10 17 ~5×10 20 cm -3 or the boron concentration ranges from 0.5×10 17 ~1×10 20 cm -3 . With the increase of depth, the concentrations of nitrogen, carbon, hydrogen, phosphorus / boron elements in the crystalline silicon substrate gradually decrease.

4. [Corrected according to Rule 26 on 20.01.2025] The functional polysilicon tunneling silicon oxide passivation contact structure according to any one of claims 1-3, characterized in that, The carbon atom doping concentration in the carbon and nitrogen co-doped polysilicon layer is 0.1 at% to 50 at%, the nitrogen atom doping concentration is 0.1 at% to 50 at%, the carbon atom doping concentration in the carbon-doped polysilicon layer is 0.1 at% to 50 at%, and the nitrogen atom doping concentration in the nitrogen-doped polysilicon layer is 0.1 at% to 50 at%.

5. The functional polysilicon tunneling silicon oxide passivation contact structure according to claim 4, characterized in that, The distribution form of carbon atoms and nitrogen atoms in the carbon and nitrogen co-doped polysilicon layer is uniform doping or gradient doping, the distribution form of carbon atoms in the carbon-doped polysilicon layer is uniform doping or gradient doping, and the distribution form of carbon atoms in the nitrogen-doped polysilicon layer is uniform doping or gradient doping.

6. The functional polysilicon tunneling silicon oxide passivation contact structure according to claim 4, characterized in that, The thickness of the carbon and nitrogen co-doped polysilicon layer is 1 nm to 1000 nm, the thickness of the carbon-doped polysilicon layer is 1 nm to 1000 nm, and the thickness of the nitrogen-doped polysilicon layer is 1 nm to 1000 nm.

7. The functional polysilicon tunneling silicon oxide passivation contact structure according to any one of claims 1-3, characterized in that, A conventional polysilicon layer is further provided on the functional polysilicon structure, and the material of the conventional polysilicon layer is polysilicon without carbon / nitrogen doping.

8. A method for preparing a functional polysilicon tunneling oxide passivation contact structure according to any one of claims 1-7, characterized in that, It includes the following steps: S1. Clean the crystalline silicon substrate; S2. Deposit nano-silicon oxide on the surface of the crystalline silicon substrate; S3. Deposit a carbon and nitrogen co-doped amorphous silicon layer on the surface of the nano-silicon oxide, or deposit an alternately stacked carbon-doped amorphous silicon layer and a nitrogen-doped amorphous silicon layer; S4. Perform high-temperature annealing to crystallize the amorphous silicon, form a functional polysilicon structure, and push carbon atoms and nitrogen atoms into the body of the crystalline silicon substrate.

9. The preparation method of the functional polysilicon tunneling silicon oxide passivation contact structure according to claim 8, characterized in that, In the step S4, the high-temperature annealing temperature is 800 °C to 1100 °C.

10. The preparation method of the functional polysilicon tunneling oxide passivation contact structure according to claim 9, characterized in that, In the step S3, PECVD is used to in-situ deposit the amorphous silicon layer.

Images