US-12622088-B2 - Functional polycrystalline silicon tunneling silicon oxide passivated contact structure and preparation method thereof

US12622088B2US 12622088 B2US12622088 B2US 12622088B2US-12622088-B2

Abstract

A functional polycrystalline silicon tunneling silicon oxide passivated contact structure (TOPCon) and a preparation method thereof are provided. The functional polycrystalline silicon tunneling silicon oxide passivated contact structure includes a crystalline silicon substrate, a nano silicon oxide, and a functional polycrystalline silicon structure laminated in sequence. The functional polycrystalline silicon structure includes a carbon and nitrogen co-doped polycrystalline silicon layer, or alternating layers of a carbon-doped polycrystalline silicon layer and a nitrogen-doped polycrystalline silicon layer. The present invention uses doping engineering to prepare new polycrystalline silicon with different functions, namely, carbon-doped polycrystalline silicon, nitrogen-doped polycrystalline silicon, and carbon and nitrogen co-doped polycrystalline silicon, and forms a functional polycrystalline silicon structure, exerting different functional effects of carbon and nitrogen doped atoms, and simultaneously realizing passivation in the bulk and surface of the silicon wafer, thereby obtaining a TOPCon structure with ultra-high passivation performance.

Inventors

Jichun Ye
Zunke LIU
Yuheng ZENG
Ruoyi Wang
Hongkai Zhou
Zhenhai YANG
Wei Liu
Mingdun LIAO

Assignees

NINGBO INSTITUTE OF MATERIALS TECHNOLOGY AND ENGINEERING, CHINESE ACADEMY OF SCIENCES

Dates

Publication Date: 20260505
Application Date: 20250630
Priority Date: 20231229

Claims (20)

1 . A functional polycrystalline silicon tunneling silicon oxide passivated contact structure, comprising a crystalline silicon substrate, a nano silicon oxide on a surface of the crystalline silicon substrate, and a functional polycrystalline silicon structure on the nano silicon oxide and laminated in sequence, wherein the functional polycrystalline silicon structure comprises a carbon and nitrogen co-doped polycrystalline silicon layer, or alternating layers of a carbon-doped polycrystalline silicon layer and a nitrogen-doped polycrystalline silicon layer; and wherein a near surface region of the crystalline silicon substrate adjacent to the nano silicon oxide comprises a nitrogen element, a carbon element, a hydrogen element, and a phosphorus element or a boron element; a nitrogen concentration at a surface of the crystalline silicon substrate is higher than 1×10 20 cm −3 , a carbon concentration at the surface of the crystalline silicon substrate is higher than 1×10 20 cm −3 , and a hydrogen concentration at the surface of the crystalline silicon substrate is higher than 1×10 19 cm −3 .
2 . The functional polycrystalline silicon tunneling silicon oxide passivated contact structure according to claim 1 , wherein the carbon and nitrogen co-doped polycrystalline silicon layer or the alternating layers of the carbon-doped polycrystalline silicon layer and the nitrogen-doped polycrystalline silicon layer in the functional polycrystalline silicon structure further comprises an active dopant atom, and the active dopant atom is phosphorus or boron.
3 . The functional polycrystalline silicon tunneling silicon oxide passivated contact structure according to claim 1 , wherein a phosphorus concentration range at the surface of the crystalline silicon substrate is 1×10 17 -5×10 20 cm −3 or a boron concentration range at the surface of the crystalline silicon substrate is 0.5×10 17 -1×10 20 cm −3 ; and a concentration of the nitrogen element, the carbon element, the hydrogen element, and the phosphorus element or the boron element in the crystalline silicon substrate gradually decreases as depth increases in a direction away from the near surface region of the crystalline silicon substrate adjacent to the nano silicon oxide.
4 . The functional polycrystalline silicon tunneling silicon oxide passivated contact structure according to claim 1 , wherein, when the functional polycrystalline silicon structure comprises the carbon and nitrogen co-doped polycrystalline silicon layer, a carbon atom doping concentration of the carbon and nitrogen co-doped polycrystalline silicon layer is 0.1-50 at % and a nitrogen atom doping concentration of the carbon and nitrogen co-doped polycrystalline silicon layer is 0.1-50 at %; and wherein, when the functional polycrystalline silicon structure comprises the alternating layers of the carbon-doped polycrystalline silicon layer and the nitrogen-doped polycrystalline silicon layer, a carbon atom doping concentration of the carbon-doped polycrystalline silicon layer is 0.1-50 at % and a nitrogen atom doping concentration of the nitrogen-doped polycrystalline silicon layer is 0.1-50 at %.
5 . The functional polycrystalline silicon tunneling silicon oxide passivated contact structure according to claim 4 , wherein, when the functional polycrystalline silicon structure comprises the carbon and nitrogen co-doped polycrystalline silicon layer, a distribution of carbon atoms and nitrogen atoms in the carbon and nitrogen co-doped polycrystalline silicon layer is a uniform doping or a gradient doping; and wherein, when the functional polycrystalline silicon structure comprises the alternating layers of the carbon-doped polycrystalline silicon layer and the nitrogen-doped polycrystalline silicon layer, a distribution of carbon atoms in the carbon-doped polycrystalline silicon layer is the uniform doping or the gradient doping, and a distribution of nitrogen atoms in the nitrogen-doped polycrystalline silicon layer is the uniform doping or the gradient doping.
6 . The functional polycrystalline silicon tunneling silicon oxide passivated contact structure according to claim 4 , wherein, when the functional polycrystalline silicon structure comprises the carbon and nitrogen co-doped polycrystalline silicon layer, a thickness of the carbon and nitrogen co-doped polycrystalline silicon layer is 1 nm-1000 nm; and wherein, when the functional polycrystalline silicon structure comprises the alternating layers of the carbon-doped polycrystalline silicon layer and the nitrogen-doped polycrystalline silicon layer, a thickness of the carbon-doped polycrystalline silicon layer is 1 nm-1000 nm, and a thickness of the nitrogen-doped polycrystalline silicon layer is 1 nm-1000 nm.
7 . The functional polycrystalline silicon tunneling silicon oxide passivated contact structure according to claim 1 , wherein a conventional polycrystalline silicon layer is further provided on the functional polycrystalline silicon structure, and a material of the conventional polycrystalline silicon layer is a polycrystalline silicon not doped with carbon or nitrogen.
8 . The functional polycrystalline silicon tunneling silicon oxide passivated contact structure according to claim 2 , wherein, when the functional polycrystalline silicon structure comprises the carbon and nitrogen co-doped polycrystalline silicon layer, a carbon atom doping concentration of the carbon and nitrogen co-doped polycrystalline silicon layer is 0.1-50 at % and a nitrogen atom doping concentration of the carbon and nitrogen co-doped polycrystalline silicon layer is 0.1-50 at %; and wherein, when the functional polycrystalline silicon structure comprises the alternating layers of the carbon-doped polycrystalline silicon layer and the nitrogen-doped polycrystalline silicon layer, a carbon atom doping concentration of the carbon-doped polycrystalline silicon layer is 0.1-50 at % and a nitrogen atom doping concentration of the nitrogen-doped polycrystalline silicon layer is 0.1-50 at %.
9 . The functional polycrystalline silicon tunneling silicon oxide passivated contact structure according to claim 3 , wherein, when the functional polycrystalline silicon structure comprises the carbon and nitrogen co-doped polycrystalline silicon layer, a carbon atom doping concentration of the carbon and nitrogen co-doped polycrystalline silicon layer is 0.1-50 at % and a nitrogen atom doping concentration of the carbon and nitrogen co-doped polycrystalline silicon layer is 0.1-50 at %; and wherein, when the functional polycrystalline silicon structure comprises the alternating layers of the carbon-doped polycrystalline silicon layer and the nitrogen-doped polycrystalline silicon layer, a carbon atom doping concentration of the carbon-doped polycrystalline silicon layer is 0.1-50 at % and a nitrogen atom doping concentration of the nitrogen-doped polycrystalline silicon layer is 0.1-50 at %.
10 . The functional polycrystalline silicon tunneling silicon oxide passivated contact structure according to claim 2 , wherein a conventional polycrystalline silicon layer is further provided on the functional polycrystalline silicon structure, and a material of the conventional polycrystalline silicon layer is a polycrystalline silicon not doped with carbon or nitrogen.
11 . The functional polycrystalline silicon tunneling silicon oxide passivated contact structure according to claim 3 , wherein a conventional polycrystalline silicon layer is further provided on the functional polycrystalline silicon structure, and a material of the conventional polycrystalline silicon layer is a polycrystalline silicon not doped with carbon or nitrogen.
12 . A preparation method of the functional polycrystalline silicon tunneling silicon oxide passivated contact structure according to claim 1 , comprising the following steps: S1, cleaning the crystalline silicon substrate; S2, depositing the nano silicon oxide on a surface of the crystalline silicon substrate; S3, depositing a carbon and nitrogen co-doped amorphous silicon layer or alternating layers of a carbon-doped amorphous silicon layer and a nitrogen-doped amorphous silicon layer on a surface of the nano silicon oxide; and S4, performing a high-temperature annealing to crystallize an amorphous silicon to form the functional polycrystalline silicon structure, and pushing carbon atoms and nitrogen atoms into a bulk of the crystalline silicon substrate.
13 . The preparation method of the functional polycrystalline silicon tunneling silicon oxide passivated contact structure according to claim 12 , wherein in the step S4, a temperature of the high-temperature annealing is 800° C.-1100° C.
14 . The preparation method of the functional polycrystalline silicon tunneling silicon oxide passivated contact structure according to claim 13 , wherein in the step S3, the carbon and nitrogen co-doped amorphous silicon layer or the alternating layers of the carbon-doped amorphous silicon layer and the nitrogen-doped amorphous silicon layer are deposited in situ by a plasma-enhanced chemical vapor deposition.
15 . The preparation method of the functional polycrystalline silicon tunneling silicon oxide passivated contact structure according to claim 12 , wherein in the functional polycrystalline silicon tunneling silicon oxide passivated contact structure, the carbon and nitrogen co-doped polycrystalline silicon layer or the alternating layers of the carbon-doped polycrystalline silicon layer and the nitrogen-doped polycrystalline silicon layer further comprises an active dopant atom, and the active dopant atom is phosphorus or boron.
16 . The preparation method of the functional polycrystalline silicon tunneling silicon oxide passivated contact structure according to claim 15 , wherein in the functional polycrystalline silicon tunneling silicon oxide passivated contact structure a phosphorus concentration range at the surface of the crystalline silicon substrate is 1×10 17 -5×10 20 cm −3 or a boron concentration range at the surface of the crystalline silicon substrate is 0.5×10 17 -1×10 20 cm −3 ; and a concentration of the nitrogen element, the carbon element, the hydrogen element, and the phosphorus element or the boron element in the crystalline silicon substrate gradually decreases as depth increases in a direction away from the near surface region of the crystalline silicon substrate adjacent to the nano silicon oxide.
17 . The preparation method of the functional polycrystalline silicon tunneling silicon oxide passivated contact structure according to claim 12 , wherein, in the functional polycrystalline silicon tunneling silicon oxide passivated contact structure, when the functional polycrystalline silicon structure comprises the carbon and nitrogen co-doped polycrystalline silicon layer, a carbon atom doping concentration of the carbon and nitrogen co-doped polycrystalline silicon layer is 0.1-50 at % and a nitrogen atom doping concentration of the carbon and nitrogen co-doped polycrystalline silicon layer is 0.1-50 at %; and wherein, when the functional polycrystalline silicon structure comprises the alternating layers of the carbon-doped polycrystalline silicon layer and the nitrogen-doped polycrystalline silicon layer, a carbon atom doping concentration of the carbon-doped polycrystalline silicon layer is 0.1-50 at % and a nitrogen atom doping concentration of the nitrogen-doped polycrystalline silicon layer is 0.1-50 at %.
18 . The preparation method of the functional polycrystalline silicon tunneling silicon oxide passivated contact structure according to claim 17 , wherein, in the functional polycrystalline silicon tunneling silicon oxide passivated contact structure, when the functional polycrystalline silicon structure comprises the carbon and nitrogen co-doped polycrystalline silicon layer, a distribution of the carbon atoms and the nitrogen atoms in the carbon and nitrogen co-doped polycrystalline silicon layer is a uniform doping or a gradient doping; and wherein, when the functional polycrystalline silicon structure comprises the alternating layers of the carbon-doped polycrystalline silicon layer and the nitrogen-doped polycrystalline silicon layer, a distribution of the carbon atoms in the carbon-doped polycrystalline silicon layer is the uniform doping or the gradient doping, and a distribution of the nitrogen atoms in the nitrogen-doped polycrystalline silicon layer is the uniform doping or the gradient doping.
19 . The preparation method of the functional polycrystalline silicon tunneling silicon oxide passivated contact structure according to claim 17 , wherein, in the functional polycrystalline silicon tunneling silicon oxide passivated contact structure, when the functional polycrystalline silicon structure comprises the carbon and nitrogen co-doped polycrystalline silicon layer, a thickness of the carbon and nitrogen co-doped polycrystalline silicon layer is 1 nm-1000 nm; and wherein, when the functional polycrystalline silicon structure comprises the alternating layers of the carbon-doped polycrystalline silicon layer and the nitrogen-doped polycrystalline silicon layer, a thickness of the carbon-doped polycrystalline silicon layer is 1 nm-1000 nm, and a thickness of the nitrogen-doped polycrystalline silicon layer is 1 nm-1000 nm.
20 . The preparation method of the functional polycrystalline silicon tunneling silicon oxide passivated contact structure according to claim 12 , wherein in the functional polycrystalline silicon tunneling silicon oxide passivated contact structure, a conventional polycrystalline silicon layer is further provided on the functional polycrystalline silicon structure, and a material of the conventional polycrystalline silicon layer is a polycrystalline silicon not doped with carbon or nitrogen.

Description

CROSS REFERENCE TO THE RELATED APPLICATIONS This application is a continuation application of International Application No. PCT/CN2024/137736, filed on Dec. 9, 2024, which is based upon and claims priority to Chinese Patent Application No. 202311841918.4, filed on Dec. 29, 2023, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD The present invention relates to the technical field of solar cells, and in particular to a functional polycrystalline silicon tunneling oxide passivated contact structure and a preparation method thereof. BACKGROUND Tunnel oxide passivated contact (TOPCon) technology is a representative passivating contact technology. Its key feature is to grow an ultra-thin nano silicon oxide (SiOx) layer on the surface of the silicon wafer to eliminate the dangling bonds on the surface and prepare a layer of heavily doped polycrystalline silicon on the ultra-thin silicon oxide to achieve a field passivation effect. Thanks to the TOPCon structure's excellent passivation performance, its mass-produced cell efficiency has now reached more than 25%; coupled with the compatibility of the production process, the planned production capacity of TOPCon cells is currently increasing rapidly. The TOPCon technology has become the mainstream technology for the expansion of industrial silicon cell production. However, in terms of efficiency improvement, the TOPCon technology currently shows certain limitations. First, the passivation performance of the TOPCon structure based on conventional polycrystalline silicon is slightly inferior to that of another representative passivating contact technology, heterojunction (HJT), and the passivation performance of the TOPCon structure needs to be further improved. Second, according to research, the corresponding silicon wafer thickness for a crystalline silicon solar cell to achieve the highest photoelectric conversion efficiency is about 110 m. In the case of a relatively thin silicon wafer, the cell performance is more sensitive to surface recombination, that 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 shown that the improvement of silicon cell efficiency will be limited by the quality of the silicon wafer, that is, the minority carrier lifetime. For example, the theoretical efficiency of a cell with a silicon wafer minority carrier lifetime of 15 ms is at least 1% higher than that of a cell with a minority carrier lifetime of 4.5 ms. Therefore, improving the silicon wafer minority carrier lifetime is also conducive to improving cell efficiency. SUMMARY In view of the shortcomings of the prior art, the purpose of the present invention is to develop a new tunneling oxide passivated contact structure that can simultaneously improve the surface passivation performance and minority carrier lifetime of the silicon wafer. To solve the above problem, the present invention provides a functional polycrystalline silicon tunneling silicon oxide passivated contact structure, including a crystalline silicon substrate, a nano silicon oxide, and a functional polycrystalline silicon structure laminated in sequence, where the functional polycrystalline silicon structure includes a carbon and nitrogen co-doped polycrystalline silicon layer or alternating layers of a carbon-doped polycrystalline silicon layer and a nitrogen-doped polycrystalline silicon layer. The present invention utilizes doping engineering to prepare new types of polycrystalline silicon with different functions, namely, carbon-doped (C) polycrystalline silicon, nitrogen-doped (N) polycrystalline silicon and carbon-nitrogen co-doped polycrystalline silicon layer, and form a functional polycrystalline silicon structure to exert the different functional effects of carbon and nitrogen doped atoms, while achieving passivation in the bulk and surface of the silicon wafer, thereby obtaining a TOPCon structure with ultra-high passivation performance, which has ultra-high minority carrier lifetime (τeff), implicit open-circuit voltage (iVoc), and ultra-low surface recombination current (J0), and can enhance the mechanical strength of the silicon wafer to a certain extent. Furthermore, the functional polycrystalline silicon structure includes an active dopant atom, and the active dopant atom is phosphorus or boron. Doping the polycrystalline silicon layer with n-type or p-type active dopant atoms can achieve an excellent field passivation effect. Furthermore, a near-surface region of the crystalline silicon substrate adjacent to the nano silicon oxide includes nitrogen, carbon, hydrogen, and phosphorus/boron elements; a nitrogen concentration at a surface of the crystalline silicon substrate is higher than 1×1020 cm−3, a carbon concentration is higher than 1×1020 cm−3, a hydrogen concentration is higher than 1×1019 cm−3, a phosphorus c