Wafer solar cell with passivated contact structure and method of manufacturing the same
By setting a through-contact region and forming a metal-silicon hybrid region within the current contact area of the wafer solar cell, the problem of high contact resistance is solved, resulting in lower contact resistance and higher cell efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CE CELL ENG GMBH
- Filing Date
- 2024-12-14
- Publication Date
- 2026-07-14
AI Technical Summary
The high contact resistance in the current contact area of existing wafer solar cells affects cell efficiency.
A through-contact area is locally set within the current contact area and penetrates through the SiO2 layer to form a metal-silicon hybrid region. A point-type direct current path is formed by local heating to reduce the contact resistance.
This significantly reduces the contact resistance between the metal electrode structure and the surface of the doped semiconductor wafer of the solar cell, thereby improving battery efficiency.
Smart Images
Figure CN122397340A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a solar cell with a passivated contact structure. The solar cell in this invention is a solar cell made of a semiconductor wafer, which forms the structural framework of the solar cell. The semiconductor wafer, made of semiconductor material, has a semiconductor wafer surface and at least one p-type doped region and at least one n-type doped region. The p-type doped region and / or the n-type doped region are electrically connected to metal electrode structures disposed on the semiconductor wafer surface through current contact regions, wherein each metal electrode structure covers an electrode coverage region on the semiconductor wafer surface. The metal electrode structures play an important role in extracting charge carriers, present in the form of current, from the wafer solar cell. Background Technology
[0002] Furthermore, wafer solar cells with passivated contact structures are known, which have a dielectric passivation layer between the metal electrode structure and the semiconductor wafer surface. In one disclosed embodiment of a wafer solar cell, the passivation layer consists of a bilayer structure comprising a polycrystalline silicon layer and an ultrathin SiO2 layer. Starting with the semiconductor material of the semiconductor wafer, a SiO2 layer is first deposited on the surface of the semiconductor wafer, followed by a polycrystalline silicon layer deposited on the SiO2 layer. Typically, the thickness of the polycrystalline layer ranges from 50 nm to 300 nm, and the thickness of the SiO2 layer ranges from 5 nm to 10 nm. Other layers, such as an anti-reflective layer, may also be selectively deposited on the SiO2 layer.
[0003] P-type and n-type wafer solar cells are known. For a p-type wafer solar cell, the semiconductor wafer has a positively charged silicon substrate, and its upper surface is negatively charged by doping with a heteromaterial. This negatively charged upper surface forms the emitter of the p-type wafer solar cell. Furthermore, in a p-type wafer solar cell, the polycrystalline silicon layer in the passivation layer is highly doped and positively charged. For an n-type wafer solar cell, the semiconductor wafer has a negatively charged silicon substrate, and its upper surface is positively charged by doping with a heteromaterial. This positively charged upper surface forms the emitter of the n-type wafer solar cell. Furthermore, in an n-type wafer solar cell, the polycrystalline silicon layer in the passivation layer is highly doped and negatively charged. The passivation of the contact structure can be designed as single-sided or double-sided passivation. The wafer solar cell can have passivated contact structures only on the front side, only on the back side, or simultaneously on both the front and back sides. The passivation contact structure can be designed in a way that allows for additional selection. For passivation contact structures designed as optional, the bilayer structure consisting of a SiO2 layer and a polycrystalline silicon layer is only placed below the metal electrode structure. The areas without a metal electrode structure are processed through appropriate steps in the wafer solar cell manufacturing process, excluding the bilayer structure consisting of the SiO2 layer and the polycrystalline silicon layer.
[0004] To form the metal electrode structure of a wafer solar cell with a polycrystalline silicon / SiO2 passivation layer, a metal paste can be printed onto the surface of a semiconductor wafer using a screen printing process, and then, during a subsequent heat treatment, the metal paste is etched or burned into the polycrystalline silicon layer, at least in localized areas. This creates opening regions and current contact regions located therein. During this process, the SiO2 layer remains intact even within these current contact regions. Particularly in metal pastes containing silver particles, silver microcrystals are locally formed within the polycrystalline silicon layer in the current contact regions when the metal paste is burned into the polycrystalline silicon layer. These localized silver microcrystals primarily constitute the current pathways for the transport of charge carriers generated in the semiconductor wafer to the metal electrode structure. The transport mechanism of these charge carriers through the SiO2 layer is mainly based on the quantum mechanical tunneling effect. In principle, the metal paste can also be applied to the semiconductor wafer surface using other processes. Furthermore, in addition to metal pastes containing silver particles, metal pastes containing silver and other metal particles, or metal pastes that completely replace silver particles with other metal particles, are also known.
[0005] The current contact area has a decisive influence on the electrical contact resistance between the metal electrode structure and the surface of the doped semiconductor wafer of the solar cell. This contact resistance should be as low as possible. Summary of the Invention
[0006] The purpose of this invention is to provide a wafer solar cell with a passivated contact structure, which has a lower electrical contact resistance, thereby improving the efficiency of the wafer solar cell.
[0007] This objective is achieved by providing at least a partial through-contact region within at least a portion of the current contact region, and within these through-contact regions, the SiO2 layer is penetrated. Furthermore, according to the invention, a metal-silicon mixture is provided in the through-contact region within a mixed region transitioning between the metal electrode structure, the polycrystalline silicon layer, the SiO2 layer (6a), and the semiconductor material. By penetrating the SiO2 layer through the through-contact region, a point-connected direct current path is formed between the semiconductor material of the semiconductor wafer and the metal electrode structure. This significantly reduces the contact resistance between the metal electrode structure and the surface of the doped semiconductor wafer of the solar cell. The design of the aforementioned mixed region further reduces the contact resistance between the metal electrode structure and the surface of the doped semiconductor wafer of the solar cell.
[0008] According to the present invention, the through-contact region having a mixing zone is formed by locally heating the opening region and / or the current contact region to a temperature range of 1000°C to 1500°C for a heating time of 10 ns to 1 s. Local heating can be achieved, for example, by LECO (laser-enhanced contact optimization) or local radiation-assisted direct heating. In LECO processing, both the positive and negative electrodes of the wafer solar cell are electrically contacted and a reverse voltage is applied, while a light source, such as a laser beam, is guided onto the surface of the wafer solar cell, thereby generating a local current and achieving local heating of the wafer solar cell. In local radiation-assisted direct heating, the corresponding area of the wafer solar cell is locally irradiated, for example, by a laser beam, wherein the energy of the laser beam is directly coupled into the wafer solar cell as thermal energy, thereby achieving direct local heating.
[0009] In an advantageous embodiment, the area of each through-contact region within the plane of the SiO2 layer is 0.05 μm. 2 Up to 1.50μm 2 Preferably 0.1μm 2 Up to 1.0μm 2 0.15μm is particularly preferred. 2 Up to 0.6μm 2 Within the range.
[0010] Another advantageous embodiment specifies that the lateral dimensions of each through-contact region within the SiO2 layer are in the range of 50 nm to 500 nm, preferably 100 nm to 250 nm, and particularly preferably 150 nm to 200 nm.
[0011] Furthermore, it is recommended that 200 to 2000 through contact areas be provided per square millimeter on the electrode coverage surface, preferably 400 to 1000 through contact areas per square millimeter, and particularly preferably 500 to 800 through contact areas per square millimeter.
[0012] Furthermore, the present invention also proposes a method for manufacturing the aforementioned wafer solar cell. This method specifies that, firstly, a wafer solar cell having a semiconductor material, a passivation layer, and a pre-designed metal electrode structure is provided; then, according to the present invention, in a heat treatment step, the current contact area is locally heated to a temperature of 1000°C to 1500°C for a time interval of 10 ns to 1 s.
[0013] In a preferred embodiment, the temperature is preferably between 1100°C and 1500°C, and particularly preferably between 1200°C and 1500°C.
[0014] In one advantageous implementation, local heating is achieved through LECO treatment or local radiation-assisted direct heating.
[0015] In the LECO process, both the positive and negative electrodes of the wafer solar cell are electrically contacted and a reverse voltage is applied. Simultaneously, a light source, such as a laser beam, is guided onto the surface of the wafer solar cell, thereby generating a localized current and achieving localized heating of the wafer solar cell. In localized radiation-assisted direct heating, a corresponding area of the wafer solar cell is locally irradiated, for example, by a laser beam. The energy from the laser irradiation is directly coupled into the wafer solar cell as heat energy, thus achieving direct localized heating. Attached Figure Description
[0016] An embodiment of the present invention will now be described with reference to the accompanying drawings:
[0017] Figure 1 A cross-sectional view of a p-type wafer solar cell with a passivated contact structure, based on existing technology;
[0018] Figure 2 A cross-sectional view of an n-type wafer solar cell with a passivated contact structure, based on existing technology;
[0019] Figure 3 :like Figure 1 and Figure 2 A partial detail view of part A in the cross-sectional view shown;
[0020] Figure 4 :like Figure 3 Top view of part A shown;
[0021] Figure 5 Analogous to Figure 3A partial detail view of part A in the cross-sectional view of the wafer solar cell described in this invention;
[0022] Figure 6 :like Figure 5 Top view of part A shown;
[0023] Figure 7 :like Figure 5 A partial detail view of part B in the cross-sectional view shown. Detailed Implementation
[0024] Figure 1 This is a schematic cross-sectional view of a p-type wafer solar cell with a passivated contact structure according to the prior art. The wafer solar cell includes a semiconductor wafer 1 having a semiconductor wafer surface consisting of a front side and a back side. An n-type doped region 3 is provided in the front side region, and a p-type doped region 2 is provided in the back side region. An anti-reflection layer 7 is provided on the n-type doped region 3, and a passivation layer 6 is provided on the p-type doped region 2. The passivation layer 6 includes a SiO2 layer 6a (silicon dioxide layer) and a poly-Si layer 6b (polycrystalline silicon layer). The SiO2 layer 6a and the polycrystalline silicon layer 6b are sequentially disposed starting from the p-type doped region 2. In this embodiment, the polycrystalline silicon layer 6b of the passivation layer 6 is a highly doped layer and is positively charged. Metal electrode junctions 4 in the form of gate fingers are respectively provided on the passivation layer 6 and the anti-reflection layer 7. In the illustrated embodiment, the wafer solar cell has the anti-reflection layer 7 only on the upper surface. However, the present invention is not limited to this type of wafer solar cell. In other embodiments, the anti-reflection layer 7 may also be disposed on the passivation layer 6 on the lower surface, or may be disposed only on the passivation layer 6 on the lower surface. Viewed from the front or back top view, the metal electrode structure 4 covers the electrode covering surface. The metal electrode structure 4 on the passivation layer 6 is connected to the current contact area 5 (see...). Figure 3 The current contact region is electrically connected to the p-type doped region 2, wherein the current contact region is located in the opening region 8 of the passivation layer 6 (see...). Figure 3 )Inside.
[0025] Figure 2This is a schematic cross-sectional view of an n-type wafer solar cell with a passivated contact structure according to the prior art. The wafer solar cell includes a semiconductor wafer 1 having a semiconductor wafer surface consisting of a front side and a back side. A p-type doped region 2 is formed in the region of the front side, while an n-type doped region 3 is formed in the region of the back side. An anti-reflection layer 7 is formed on the p-type doped region 2, and a passivation layer 6 is formed on the n-type doped region 3. In the illustrated embodiment, the wafer solar cell has an anti-reflection layer 7 only on the upper surface. However, the present invention is not limited to this type of wafer solar cell. In other embodiments, the anti-reflection layer 7 may also be formed on the passivation layer 6 on the lower surface, or only on the passivation layer 6 on the lower surface. The passivation layer 6 includes a SiO2 layer 6a (silicon dioxide layer) and a poly-Si layer 6b (polycrystalline silicon layer). The SiO2 layer 6a and the polycrystalline silicon layer 6b are sequentially formed starting from the n-type doped region 3. In this embodiment, the polycrystalline silicon layer 6b of the passivation layer 6 is a highly doped layer and is negatively charged. Metal electrode structures 4 in the form of grid fingers are respectively provided on the passivation layer 6 and the antireflection layer 7. Viewed from the front or back top view, the metal electrode structures 4 are on the electrode coverage surface. The metal electrode structures 4 disposed on the passivation layer 6 are in contact with the current contact area 5 (see...). Figure 3 ) is electrically connected to the n-type doped region 3, wherein the current contact region is located in the opening region 8 of the passivation layer 6 (see Figure 3 )Inside.
[0026] Furthermore, this invention is not limited to wafer solar cells with a fully bilayer structure consisting of a SiO2 layer and a polycrystalline silicon layer. In other embodiments not described, wafer solar cells with selectively passivated contact structures are also within the scope of this invention. For this selectively designed passivated contact, the bilayer structure consisting of a SiO2 layer and a polycrystalline silicon layer is only provided in the region of the wafer solar cell covered by the metal electrode structure. The region not covered by the metal electrode structure does not have a polycrystalline silicon layer.
[0027] Figure 3 for Figure 1 and Figure 2 The image shows a partial detail of part A in a cross-sectional view of a prior art wafer solar cell with a passivated contact structure. In this detail view, an opening region 8 can be seen on the side of the metal electrode structure 4 facing the semiconductor materials 2 and 3. This opening region is characterized in that the material of the metal electrode structure 4 partially penetrates the polycrystalline silicon layer 6b within this region. Furthermore, five current contact regions 5 can be seen within the opening region 8. In these regions, the material of the metal electrode structure 4 penetrates deeper into the polycrystalline silicon layer 6b. These current contact regions 5 have different lateral dimensions.
[0028] Figure 4 Shown from a top-down perspective Figure 3The diagram shows the distribution of the current contact region 5 in part A, which is visible after the electrode structure 4 has been removed.
[0029] Figure 5 To and Figure 3 A comparable partial detail view of portion A in the cross-sectional view of the wafer solar cell described in this invention. In this embodiment, at least a portion of the current contact region 5 has at least a partially provided through contact region 9. The SiO2 layer is penetrated through these through contact regions 9. Within these through contact regions 9, a portion of the material of the metal electrode structure 4 penetrates the SiO2 layer and extends into the semiconductor materials 2 and 3.
[0030] Figure 6 Shown from a top-down perspective Figure 5 A schematic diagram showing the distribution of the through contact area 9 within the current contact area 5 in Part A.
[0031] Each through-contact region 9 has an area range of 0.05 μm² to 1.50 μm² within the SiO2 layer, preferably 0.1 μm² to 1.0 μm², and particularly preferably 0.15 μm² to 0.6 μm².
[0032] Each through-contact region 9 has a lateral dimension range of 50nm to 500nm within the SiO2 layer, preferably a range of 100nm to 250nm, and particularly preferably a range of 150nm to 200nm.
[0033] On the electrode covering surface, there are 200 to 2000 through contact areas 9 per square millimeter, preferably 400 to 1000 through contact areas 9 per square millimeter, and particularly preferably 500 to 800 through contact areas 9 per square millimeter.
[0034] Figure 7 For example Figure 5 A partial detail view of section B of the cross-sectional view shown. At the through contact region 9, a metal-silicon mixture is provided in the mixed region between the metal electrode structure 4, the polycrystalline silicon layer 6b, the silicon oxide layer 6a, and the semiconductor materials 2 and 3.
[0035] The lateral dimension of the mixing region 10 within the SiO2 layer ranges from 50 nm to 300 nm, preferably from 100 nm to 250 nm, and particularly preferably from 150 nm to 200 nm.
[0036] The mixing region 10 has a size in the direction perpendicular to the SiO2 layer ranging from 100 nm to 1000 nm, preferably from 200 nm to 800 nm, and particularly preferably from 400 nm to 700 nm.
[0037] To manufacture the wafer solar cell of the present invention, a wafer solar cell having a semiconductor material, a passivation layer, and a designed metal electrode structure is first provided. Then, in a heat treatment step, the current contact region 5 is locally heated to a temperature range of 1000°C to 1500°C over a time interval of 10 ns to 1 s. The local heating of the current contact region 5 is achieved by LECO treatment or local radiation-assisted direct heating. Preferably, the temperature range is 1100°C to 1500°C, more preferably 1200°C to 1500°C.
[0038] In the embodiments, the metal electrode structure 4 is formed, for example, by a metal paste applied to the wafer surface using a screen printing process. However, the invention is not limited thereto. The metal paste can also be applied using other processes. Preferably, the metal paste contains silver particles. However, the invention is not limited thereto. For example, the metal paste may contain other metal particles (e.g., aluminum, copper, etc.) in addition to silver particles. In other embodiments, the metal paste may be replaced with other metal particles (e.g., aluminum, copper, etc.) instead of silver particles.
[0039] List of reference numerals in the attached diagram:
[0040] 1. Semiconductor wafer
[0041] 2p-type doped region
[0042] 3 n-type doped regions
[0043] 4. Metal Electrode Structure
[0044] 5 Electrical contact area
[0045] 6. Passivation layer
[0046] 6a SiO2 layer (silicon dioxide layer)
[0047] 6b poly-Si layer (polycrystalline silicon layer)
[0048] 7 Anti-reflective layer
[0049] 8. Opening area
[0050] 9. Through-contact area
[0051] 10 Mixed Areas
Claims
1. A wafer solar cell comprising a semiconductor wafer (1) made of semiconductor material, said semiconductor wafer having a semiconductor wafer surface and at least one p-type doped region (2) 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 connected to the metal electrode structure (4) disposed on the surface of the semiconductor wafer through an opening region (8) and a current contact region (5) within that region, respectively, and each 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 is provided with a passivation layer located between the semiconductor material and the metal electrode structure (4), the passivation layer comprising a polycrystalline silicon layer (6b) and a SiO2 layer ( A double-layer structure consisting of 6a); wherein the current contact region (5) extends at least partially into the polysilicon layer (6b); characterized in that: at least a portion of the current contact region (5) is provided with a through contact region (9), in which the SiO2 layer (6a) is penetrated; and, at the through contact region (9), a metal-silicon mixture is provided in the mixed region between the metal electrode structure (4), the polysilicon layer (6b), the SiO2 layer (6a) and the semiconductor material.
2. The wafer solar cell according to claim 1, characterized in that, The area of each through-contact region (9) within the SiO2 layer is 0.05 μm. 2 Up to 1.50μm 2 Within the range, preferably 0.1μm 2 Up to 1.0μm 2 Within the range, 0.15 μm is particularly preferred. 2 Up to 0.6μm 2 Within the range.
3. The wafer solar cell according to claim 1, characterized in that, The lateral dimensions of each through contact area (9) within the SiO2 layer are in the range of 50nm to 500nm, preferably in the range of 100nm to 250nm, and particularly preferably in the range of 150nm to 200nm.
4. The wafer solar cell according to any one of the preceding claims, characterized in that, Within the electrode coverage area, there are 200 to 2000 through contact areas (9) per square millimeter, preferably 400 to 1000 through contact areas (9) per square millimeter, and particularly preferably 500 to 800 through contact areas (9) per square millimeter.
5. The wafer solar cell according to any one of the preceding claims, characterized in that, The lateral dimension of the mixing region (10) within the SiO2 layer is in the range of 50 nm to 300 nm, preferably in the range of 100 nm to 250 nm, and particularly preferably in the range of 150 nm to 200 nm.
6. The wafer solar cell according to any one of the preceding claims, characterized in that, The mixing region (10) has a size in the direction perpendicular to the SiO2 layer in the range of 100nm to 1000nm, preferably in the range of 200nm to 800nm, and particularly preferably in the range of 400nm to 700nm.
7. 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 semiconductor material, passivation layer (6) and shaped metal electrode structure (4) is provided; then, in a heat treatment step, the current contact area (5) is locally heated to a temperature range of 1,000°C to 1,500°C for a heating time of 10 ns to 1 s.
8. The method according to claim 7, characterized in that, The temperature is preferably in the range of 1,100°C to 1,500°C, and particularly preferably in the range of 1,200°C to 1,500°C.
9. The method according to claim 7 or 8, characterized in that, The localized heating is achieved through LECO treatment or localized radiation-assisted direct heating.