Wafer solar cell and method of manufacturing the same
Patent Information
- Application Number
- CN202480087704.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-12-15
- Filing Date
- 2024-12-14
- Publication Date
- 2026-09-11
AI Technical Summary
相反，在使用无铝金属浆料(例如无铝银浆)时，通常仅会在半导体材料与金属电极结构之间形成较差的电接触
Smart Images
Figure CN122743979A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a wafer solar cell. In the context of this invention, a wafer solar cell should be understood as a solar cell made of a silicon semiconductor wafer, with the semiconductor wafer forming the structural framework of the solar cell. The semiconductor wafer, formed of a semiconductor material (silicon), has a semiconductor wafer surface and at least one p-type doped region and at least one n-type doped region, wherein the p-type doped region and / or the n-type doped region are electrically contacted with metal electrode structures disposed on the semiconductor wafer surface through current contact regions, and each metal electrode structure covers the electrode coverage area on the semiconductor wafer surface. The metal electrode structures are important for extracting charge carriers from the wafer solar cell in the form of current. The p-type doping of silicon can be achieved using boron, gallium, or aluminum. Background Technology
[0002] It is known that a wafer solar cell may have at least one dielectric passivation layer disposed between the metal electrode structure and the surface of the semiconductor wafer. The passivation layer is typically selected from the group consisting of: AlOx (alumina), SiNx (silicon nitride), SiOxNy (silicon oxynitride), SiOx (silicon oxide), and / or poly-Si (polycrystalline silicon). Typically, the passivation layer has a thickness in the range of 50 nm to 200 nm. Other layers, such as an anti-reflective layer, may optionally be disposed on the passivation layer.
[0003] P-type and n-type solar cell wafers are known. In a p-type solar cell, the semiconductor wafer has a positively charged silicon substrate, the upper surface of which is negatively charged by doping with an external material. This negatively charged upper surface forms the emitter of the p-type solar cell. In an n-type solar cell, the semiconductor wafer has a negatively charged silicon substrate, the upper surface of which is positively charged by doping with an external material. This positively charged upper surface forms the emitter of the n-type solar cell.
[0004] In order to form the metal electrode structure of a wafer solar cell with a passivation layer, metal paste is printed onto the surface of the semiconductor wafer, for example, by screen printing, and in a subsequent heat treatment step, the metal paste is at least partially etched or burned into the passivation layer.
[0005] An opening region is formed in the passivation layer by at least partial burning-in. Within at least a portion of the opening region, a current contact region that completely penetrates the passivation layer is further formed. This current contact region primarily forms a path for the flow of charge carriers generated in the semiconductor wafer to the metal electrode structure. Therefore, the current contact region has a decisive influence on the electrical contact resistance between the metal electrode structure and the doped semiconductor wafer surface of the solar cell. This contact resistance should be as low as possible.
[0006] As is known from existing technology, for p-type doped emitters made of boron or gallium, low contact resistance of the metal electrode structure can only be achieved if the metal paste used to fabricate the metal electrode structure contains at least a small amount of aluminum. Conversely, when using aluminum-free metal pastes (such as aluminum-free silver paste), poor electrical contact is typically formed between the semiconductor material and the metal electrode structure. On the other hand, the aluminum particles used in the metal paste are usually relatively large, which limits the minimum gate width during screen printing and also narrows the process window when sintering these metal pastes. Summary of the Invention
[0007] The purpose of this invention is to provide a wafer solar cell, wherein the wafer solar cell has reduced electrical contact resistance while minimizing adverse effects on semiconductor materials, thereby improving the efficiency of the wafer solar cell.
[0008] For a wafer solar cell having a region of semiconductor material p-type doped with aluminum, this objective is achieved by forming a second mixing region in the semiconductor material at the end of the first mixing region facing the semiconductor material in the current contact region. In this second mixing region, aluminum atoms are embedded in the semiconductor material, and the aluminum atom concentration in the second mixing region is higher than the aluminum atom concentration in the semiconductor material outside the first and second mixing regions. Therefore, an intermediate layer (the second mixing region) is provided in the transition portion between the first mixing region and the semiconductor material, in which the semiconductor material is doped with aluminum atoms at a higher concentration.
[0009] This significantly reduces the contact resistance between the metal electrode structure of the wafer solar cell and the surface of the doped semiconductor wafer. The reduction in contact resistance can be attributed to the higher degree of local doping of the silicon-based semiconductor material in the second mixing region through the embedded aluminum atoms.
[0010] Furthermore, for wafer solar cells having regions of semiconductor material p-type doped with boron or gallium, this objective is achieved by forming a second mixing region in the semiconductor material at the end of the first mixing region facing the semiconductor material in the current contact region, and embedding aluminum atoms into the semiconductor material in this second mixing region. Thus, an intermediate layer (the second mixing region) is provided at the transition between the first mixing region and the semiconductor material, in which the semiconductor material is doped with aluminum atoms.
[0011] This significantly reduces the contact resistance between the metal electrode structure of the solar cell and the surface of the doped semiconductor wafer. This reduction in contact resistance can be explained by the fact that, on the one hand, the silicon-based semiconductor material is locally doped in the second mixing region by embedded aluminum atoms.
[0012] If aluminum atoms are already embedded in a region of a p-type doped semiconductor material of boron or gallium due to impurities in the initial material, then the present invention should be understood as follows: in this case, the aluminum atom concentration in the second mixed region is also greater than the aluminum atom concentration in the semiconductor material outside the first and second mixed regions.
[0013] Regarding the second mixing region, it should be clarified again that the second mixing region is only locally located at the current contact region. The various local second mixing regions located below the metal electrode structure are separate from each other. The second mixing regions do not collectively form a continuous layer below the metal electrode structure.
[0014] In one embodiment, the passivation layer is at least partially formed of aluminum oxide, and / or the metal electrode structure is formed of a metallic material that contains at least a portion of aluminum.
[0015] According to the invention, the second mixing region is generated by locally heating the opening region and / or the current contact region. Local heating of the opening region and / or the current contact region is achieved, particularly in the alumina layer and the semiconductor material region adjacent to the alumina layer, at temperatures ranging from 600°C to 1,500°C. Heating within this temperature range should last for a time ranging from 10 ns to 1 second. This local heating can be achieved, for example, by LECO (Laser Enhanced Contact Optimization) or by localized radiation-assisted direct heating. In LECO, the wafer solar cell is electrically contacted in two polarity directions, a reverse voltage is applied, and a light source or point source (e.g., a laser beam) is moved on the surface of the wafer solar cell, thereby achieving localized heating of the wafer solar cell through the resulting localized current. In localized radiation-assisted direct heating, for example, the relevant region of the wafer solar cell is locally irradiated by laser radiation, wherein the laser energy of the laser radiation is directly coupled into the wafer solar cell as thermal energy, thereby achieving direct localized heating.
[0016] In an advantageous embodiment, the second mixing region has a lateral dimension in the range of 100 nm to 1,000 nm in a plane parallel to the passivation layer, preferably in the range of 200 nm to 800 nm, and particularly preferably in the range of 400 nm to 700 nm.
[0017] One advantageous embodiment specifies that the second mixing region has a lateral dimension in the range of 25 nm to 250 nm, preferably in the range of 50 nm to 200 nm, and particularly preferably in the range of 75 nm to 150 nm, perpendicular to a plane parallel to the passivation layer.
[0018] It is proposed here that aluminum atoms in the second mixing region are embedded at a concentration ranging from 0.1 wt% to 2.0 wt%, preferably at a concentration ranging from 0.3 wt% to 1.8 wt%, and more preferably at a concentration ranging from 0.5 wt% to 1.5 wt% (wt% is a weight percentage used to express the mass fraction of a substance in a material mixture).
[0019] Furthermore, the first mixing region has a diameter of 0.05 μm in the plane of the passivation layer. 2 Up to 1.00μm 2 The area within the range is preferably 0.1 μm. 2 Up to 0.8μm 2The area within the range is particularly preferably 0.2 μm. 2 Up to 0.5μm 2 The area within the specified range.
[0020] In an advantageous embodiment, the first mixing regions each have a lateral dimension in the plane of the passivation layer ranging from 100 nm to 1,000 nm, preferably ranging from 200 nm to 800 nm, and particularly preferably ranging from 400 nm to 700 nm.
[0021] Another advantageous specific embodiment specifies that, on the electrode coverage area, per mm 2 There are 500 to 45,000 first mixing zones, preferably set per mm 2 There are 2,000 to 15,000 first mixing zones, with a particularly preferred setting per mm 2 There are 3,000 to 6,000 first mixed zones.
[0022] Furthermore, a method for manufacturing the wafer solar cell of the present invention is provided herein. The method specifies that a wafer solar cell having the semiconductor material, the passivation layer, and the formed metal electrode structure is first provided, and then, according to the invention, in a heat treatment step, the current contact region is locally heated to a temperature in the range of 600°C to 1,500°C for a time period in the range of 10 ns to 1 s.
[0023] It is proposed that the temperature is in the range of 900°C to 1,500°C, preferably in the range of 1,100°C to 1,500°C, and more preferably in the range of 1,250°C to 1,500°C.
[0024] Especially when using aluminum-free metal paste, the localized heating allows some of the aluminum in the passivation layer formed by Al2O3 to precipitate and react simultaneously with the aluminum-free metal paste. Here, the aluminum serves, at least temporarily, to lower the melting temperature of the alloy formed by the aluminum and the aluminum-free metal paste.
[0025] In an advantageous embodiment, the local heating is achieved by LECO treatment or by local radiation-assisted direct heating.
[0026] In the LECO process, the wafer solar cell is electrically contacted in two polarity directions, a reverse voltage is applied, and a light source or point source (e.g., a laser beam) is moved across the surface of the wafer solar cell, thereby achieving localized heating of the wafer solar cell through the resulting localized current. In localized radiation-assisted direct heating, for example, a relevant area of the wafer solar cell is locally irradiated by laser radiation, wherein the laser energy of the laser radiation is directly coupled into the wafer solar cell as thermal energy, thereby achieving direct localized heating. Attached Figure Description
[0027] An embodiment of the present invention will now be described with reference to the accompanying drawings.
[0028] Figure 1 : A cross-sectional schematic diagram of a wafer solar cell according to the present invention.
[0029] Figure 2 : Figure 1 The detailed view of part A in the cross-sectional view shown.
[0030] Figure 3 : Figure 1 The detailed view of part B in the cross-sectional view shown. Detailed Implementation
[0031] Figure 1 A schematic cross-sectional view of an n-type wafer solar cell according to the present invention is shown. The wafer solar cell has a silicon semiconductor wafer 1 having semiconductor wafer surfaces including a front side and a back side. A p-type doped region 3, formed of boron, gallium, or aluminum, is formed in the front side region, while an n-type doped region 2 is formed in the back side region. Passivation layers 6 are respectively disposed on the n-type doped region 2 and the p-type doped region 3. The passivation layer 6 disposed on the p-type doped region 3 is further covered with an anti-reflection layer 7. The anti-reflection layer 7 is optional and not mandatory. The passivation layer 6 has at least a layer formed of aluminum oxide (e.g., Al₂O₃). That is, the passivation layer 6 may be composed entirely of a layer formed of aluminum oxide, or may have other layers in addition to a layer formed of aluminum oxide. These other layers may be formed, for example, of SiNx (silicon nitride), SiOxNy (silicon oxynitride), SiOx (silicon oxide), and / or poly-Si (polycrystalline silicon).
[0032] A metal electrode structure 4 in the form of a finger electrode is respectively disposed on the passivation layer 6 and the antireflection layer 7 disposed on the n-type doped region 2. The metal electrode structure 4 covers an electrode coverage area when viewed from above the front or back side. The metal electrode structure 4 located on the antireflection layer 7 is in contact with the current contact area 5. Figure 2The current contact region 5 is electrically connected to the p-type doped region 3, and the current contact region 5 is located in the opening region 8 of the passivation layer 6 and the antireflection layer 7. Figure 2 Similarly, the metal electrode structure 4 located on the passivation layer 6 is electrically connected to the n-type doped region 2 via a current contact region 5, which is located within the opening region 8 of the passivation layer 6 disposed on the n-type doped region 2. In the illustrated embodiment, the metal electrode structure 4 is formed of at least partially aluminum-containing metal material or aluminum-free metal material. For example, the metal material may be made of silver, or the metal material may be made of silver mixed with aluminum.
[0033] Figure 2 It shows Figure 1 The diagram shows a detailed view of part A in the cross-sectional view. In this detailed view, a conductive gate line of the metal electrode structure 4, as well as the passivation layer 6, anti-reflection layer 7, and p-type doped region 3 of the silicon semiconductor material, can be seen in cross-section. Furthermore, an opening region 8 is also visible, within which a current contact region 5 is disposed. In the opening region 8, the material of the metal electrode structure 4 partially penetrates the anti-reflection layer 7. In the current contact region 5, the material of the metal electrode structure 4 penetrates the passivation layer 6 and the anti-reflection layer 7, and extends into the p-type doped region 3 of the semiconductor material.
[0034] At the current contact region 5, a metal-silicon mixture is formed in the first mixing region 9, which is the transition between the metal electrode structure 4, the passivation layer 6, and the semiconductor material. Furthermore, in the current contact region 5, at the end of the first mixing region 9 facing the semiconductor material, a second mixing region 10 is formed in the semiconductor material. If the p-type doped region of the semiconductor material is doped with boron or gallium, aluminum atoms are embedded in the p-type doped region of the semiconductor material in the second mixing region 10. If the p-type doped region of the semiconductor material has already been doped with aluminum during the fabrication of the wafer solar cell, then the aluminum atom concentration in the second mixing region 10 is greater than the aluminum atom concentration in the semiconductor material outside the first and second mixing regions 9 and 10.
[0035] Figure 3 It shows that according to Figure 1A detailed view of part B in the cross-sectional view. In this detailed view, a conductive gate line of the metal electrode structure 4, as well as the passivation layer 6 of the silicon semiconductor material and the cross-section of the n-type doped region 2, can be seen. Furthermore, an opening region 8 can be seen, within which a current contact region 5 is provided. In the opening region 8, the material of the metal electrode structure 4 partially penetrates the passivation layer 6. In the current contact region 5, the material of the metal electrode structure 4 penetrates the passivation layer 6 and extends into the n-type doped region 2 of the semiconductor material.
[0036] At the current contact region 5, a metal-silicon mixture is formed in a first mixing region 9, which is the transition between the metal electrode structure 4, the passivation layer 6, and the semiconductor material. Furthermore, at the end of the first mixing region 9 facing the semiconductor material, a second mixing region 10 is formed in the semiconductor material within the current contact region 5. In this second mixing region 10, aluminum atoms are embedded in the n-type doped regions of the semiconductor material.
[0037] Both the metal electrode structure 4 on the p-type doped side of the semiconductor material and the metal electrode structure 4 on the n-type doped side of the semiconductor material are provided with multiple opening regions 8 and multiple current contact regions 5 disposed therein.
[0038] The second mixing region 10 has a lateral dimension in the range of 100 nm to 1,000 nm in a plane parallel to the passivation layer, preferably in the range of 200 nm to 800 nm, and particularly preferably in the range of 400 nm to 700 nm. Perpendicular to the plane parallel to the passivation layer, the second mixing region 10 has a lateral dimension in the range of 25 nm to 250 nm, preferably in the range of 50 nm to 200 nm, and particularly preferably in the range of 75 nm to 150 nm.
[0039] In the second mixing region 10, aluminum atoms are embedded at a concentration ranging from 0.1 wt% to 2.0 wt%, preferably at a concentration ranging from 0.3 wt% to 1.8 wt%, and more preferably at a concentration ranging from 0.5 wt% to 1.5 wt%.
[0040] The first mixing region 9 has a diameter of 0.05 μm in the plane of the passivation layer 6. 2 Up to 1.00μm 2 The area within the range is preferably 0.1 μm. 2 Up to 0.8μm 2 The area within the range is particularly preferably 0.2 μm. 2 Up to 0.5μm2 The area within the range. Perpendicular to the plane of the passivation layer 6, the first mixing region 9 has a lateral dimension in the range of 100nm to 1,000nm, preferably in the range of 200nm to 800nm, and particularly preferably in the range of 400nm to 700nm.
[0041] Set per mm on the electrode coverage area 2 There are 500 to 45,000 first mixing zones 9, preferably set per mm 2 There are 2,000 to 15,000 first mixing zones 9, with a particularly preferred setting per mm 2 There are 3,000 to 6,000 first mixed zones.
[0042] This invention is not limited to the embodiments shown. For example, the wafer solar cell can also be a p-type wafer solar cell, wherein the p-type doped region and the n-type doped region are interchanged relative to the n-type wafer solar cell. Furthermore, in both p-type and n-type wafer solar cells, the passivation layer 6 formed of alumina can be disposed only on the n-type doped side or only on the p-type doped side.
[0043] Unlike the embodiments described above, the passivation layer 6 may not be formed of aluminum oxide. For example, the passivation layer 6 may be formed of SiNx (silicon nitride), SiOxNy (silicon oxynitride), SiOx (silicon oxide), and / or poly-Si (polycrystalline silicon).
[0044] To manufacture the wafer solar cell of the present invention, a wafer solar cell having a semiconductor material, a passivation layer 6, and a formed metal electrode structure 4 is first provided. Subsequently, in a heat treatment step, the current contact region 5 is locally heated to a temperature in the range of 600°C to 1,500°C for a time period ranging from 10 ns to 1 s. In other embodiments, the temperature is in the range of 900°C to 1,500°C, preferably in the range of 1,100°C to 1,500°C, and more preferably in the range of 1,250°C to 1,500°C. This localized heating is achieved by LECO treatment or by localized radiation-assisted direct heating.
[0045] The aluminum atoms embedded in the second mixed region 10 of the semiconductor material may, for example, originate from the passivation layer 6 formed at least partially of aluminum oxide and / or from the metal electrode structure 4 formed at least partially of aluminum-containing metal material, but the invention is not limited thereto.
[0046] List of reference numerals in the attached diagram:
[0047] 1. Semiconductor wafer
[0048] 2 p-type doped region
[0049] 3 n-type doped regions
[0050] 4. Metal Electrode Structure
[0051] 5 Current contact area
[0052] 6. Passivation layer
[0053] 7 Anti-reflective layer
[0054] 8. Opening area
[0055] 9 First Mixed Region
[0056] 10 Second Mixing Region
Claims
1. A wafer solar cell comprising a semiconductor wafer (1) made of silicon-based semiconductor material, said semiconductor wafer having a semiconductor wafer surface, at least one p-type doped region (2) of boron or gallium and at least one n-type doped region (3), wherein, The p-type doped region (2) and / or the n-type doped region (3) are electrically contacted with the metal electrode structure (4) disposed on the surface of the semiconductor wafer through the opening region (8) and the current contact region (5) located in the opening region, and the metal electrode structure (4) covers the electrode coverage area on the surface of the semiconductor wafer, wherein the semiconductor wafer surface of the wafer solar cell has a passivation layer (6) disposed between the semiconductor material and the metal electrode structure (4), and wherein the current contact region (5) penetrates the passivation layer (6), and wherein a metal-silicon mixture is formed in the first mixing region (9) of the transition portion between the metal electrode structure, the passivation layer (6) and the semiconductor material at the current contact region (5), characterized in that, in the current contact region (5), at one end of the first mixing region (9) facing the semiconductor material, a second mixing region (10) is formed in the semiconductor material, and in the second mixing region (10), aluminum atoms are embedded in the semiconductor material.
2. A wafer solar cell comprising a semiconductor wafer (1) made of silicon-based semiconductor material, said semiconductor wafer having a semiconductor wafer surface and including at least one p-type doped region (2) of aluminum and at least one n-type doped region (3), wherein, The p-type doped region (2) and / or the n-type doped region (3) are electrically contacted with the metal electrode structure (4) on the surface of the semiconductor wafer through an opening region (8) and a current contact region (5) located in the opening region, and the metal electrode structure (4) covers the electrode coverage area on the surface of the semiconductor wafer, wherein the semiconductor wafer surface of the wafer solar cell has a passivation layer (6) disposed between the semiconductor material and the metal electrode structure (4), and wherein the current contact region (5) penetrates the passivation layer (6), and wherein in the current contact region (5) A metal-silicon mixture is formed in a first mixing region (9) of the transition portion between the metal electrode structure, the passivation layer (6), and the semiconductor material. The characteristic feature is that, in the current contact region (5), at one end of the first mixing region (9) facing the semiconductor material, a second mixing region (10) is formed in the semiconductor material, and in the second mixing region (10), aluminum atoms are embedded in the semiconductor material, and the aluminum atom concentration in the second mixing region is higher than the aluminum atom concentration in the semiconductor material outside the first mixing region and the second mixing region (9, 10).
3. The wafer solar cell according to any one of the preceding claims, characterized in that, The passivation layer (6) is at least partially formed of aluminum oxide, and / or the metal electrode structure (4) is formed of at least partially aluminum-containing metal material.
4. The wafer solar cell according to any one of the preceding claims, characterized in that, Aluminum atoms are embedded in the second mixing region at a concentration ranging from 0.1 wt% to 2.0 wt%, preferably from 0.3 wt% to 1.8 wt%, and more preferably from 0.5 wt% to 1.5 wt%.
5. The wafer solar cell according to claim 1, characterized in that, The second mixing region (10) has a lateral dimension in the range of 100 nm to 1,000 nm in a plane parallel to the passivation layer, preferably in the range of 200 nm to 800 nm, and particularly preferably in the range of 400 nm to 700 nm.
6. The wafer solar cell according to any one of the preceding claims, characterized in that, The second mixing region (10) has a lateral dimension in the range of 25 nm to 250 nm, preferably in the range of 50 nm to 200 nm, and particularly preferably in the range of 75 nm to 150 nm, perpendicular to a plane parallel to the passivation layer.
7. The wafer solar cell according to any one of the preceding claims, characterized in that, The first mixing regions (9) have an area in the plane of the passivation layer in the range of 0.05 μm 2 to 1.00 μm 2 , preferably an area in the range of 0.1 μm 2 to 0.8 μm 2 , particularly preferably an area in the range of 0.2 μm 2 to 0.5 μm 2 .
8. The wafer solar cell according to any one of the preceding claims, characterized in that, The first mixing region (9) has a lateral dimension in the range of 100 nm to 1,000 nm, preferably in the range of 200 nm to 800 nm, and particularly preferably in the range of 400 nm to 700 nm, perpendicular to the plane of the passivation layer.
9. The wafer solar cell according to any one of the preceding claims, characterized in that, 500 to 45,000 first mixing zones (9) per mm2are provided over the electrode cover area, preferably 1,000 to 30,000 first mixing zones (9) per mm2are provided 2 2,000 to 15,000 first mixing zones (9) are provided, particularly preferably 3,000 to 6,000 first mixing zones (9) are provided 2 2,000 to 15,000 first mixing zones (9) are provided, particularly preferably 3,000 to 6,000 first mixing zones (9) are provided 10. A method for manufacturing a wafer solar cell according to any one of the preceding claims, characterized in that, First, a wafer solar cell having the semiconductor material, the passivation layer (6), and the formed metal electrode structure (4) is provided, and then in a heat treatment step, the current contact region (5) is locally heated to a temperature in the range of 600°C to 1,500°C for a period of time in the range of 10 ns to 1 s.
11. The method according to claim 10, characterized in that, The temperature is in the range of 900°C to 1,500°C, preferably in the range of 1,100°C to 1,500°C, and more preferably in the range of 1,250°C to 1,500°C.
12. The method according to claim 10 or 11, characterized in that, The localized heating is achieved through LECO treatment or through localized radiation-assisted direct heating.