A back contact solar cell and a method for manufacturing the same

Abstract

The application relates to a back contact solar cell and a preparation method thereof. The back contact solar cell comprises a front surface and a back surface oppositely arranged on a semiconductor substrate. The back surface comprises a first conductive region, a second conductive region and an isolation structure unit. The first conductive region and the second conductive region are oppositely arranged along a first direction of the semiconductor substrate. The isolation structure unit is arranged between the first conductive region and the second conductive region. The length of the isolation structure unit along the first direction is 20.0-200.0 mu m. The isolation structure unit comprises a first isolation region, a second isolation region, a third isolation region, a fourth isolation region and a fifth isolation region with different topographies. The isolation structure unit provided by the application can realize good insulation effect, improve the collection efficiency of carriers, improve the passivation performance of the isolation region, reduce the damage caused by laser grooving to the cell, and improve the photoelectric conversion efficiency of the back contact cell.

Description

Technical Field

[0001] This application relates to the technical field of solar cells, and in particular to a back-contact solar cell and a method for its fabrication. Background Technology

[0002] The positive and negative metal electrodes of the back-contact battery are arranged in an interdigitated manner on the back surface of the battery. This design ensures that there are no metal grid lines blocking the front surface of the battery, thereby maximizing the light-receiving area of ​​the battery, reducing optical losses, and improving short-circuit current and overall photoelectric conversion efficiency. It is one of the current technical directions for preparing high-efficiency crystalline silicon batteries.

[0003] To prevent charge carriers from directly contacting the N-type and P-type doped regions on the back side, which would hinder effective carrier collection, an isolation region is needed between them. For example, CN218975459U discloses a back-contact battery and photovoltaic module. This back-contact battery includes a semiconductor substrate, a first doped semiconductor layer, and a second doped semiconductor layer. The back side of the semiconductor substrate has a central region and an edge isolation region extending outward from the central region. The central region is divided into alternating first and second regions. The surface of the edge isolation region is recessed inward relative to the surface of the first region. The first doped semiconductor layer is formed on the first region, and the second doped semiconductor layer is formed on the second region. Although this patent proposes an edge isolation region design, it does not specify the design of the isolation region's morphology, leaving the morphological characteristics of the isolation region having a significant impact on carrier collection in the back-contact battery.

[0004] Publication number CN115566088A discloses a back-contact battery and its manufacturing method, as well as a photovoltaic module. The back-contact battery includes a semiconductor substrate, a first doped semiconductor layer, and a second doped semiconductor layer. Along a direction parallel to the back surface, the back surface has alternately arranged first and second regions. The surface of the second region has a first hole structure recessed into the semiconductor substrate. The first doped semiconductor layer is formed on the first region, and the second doped semiconductor layer is formed on the second region. Although this patent proposes setting the first hole structure on the surface of the second region, the question remains: how to further optimize the morphology and size of the hole structure to improve the photoelectric conversion efficiency of the back-contact battery?

[0005] The aforementioned technologies have the following shortcomings: the morphology of the isolation region affects carrier collection in back-contact batteries, and how to design the morphology of the isolation region to improve carrier collection efficiency remains a pressing technical problem. Furthermore, in the existing manufacturing process of back-contact batteries, the fabrication process of the isolation region is prone to damaging the battery, leading to a decrease in the fill factor (FF) and hindering the improvement of the conversion efficiency of the back-contact battery. Therefore, a novel back-contact battery structure and its fabrication method are urgently needed to solve the above-mentioned technical problems. Summary of the Invention

[0006] In order to improve the carrier collection efficiency of back-contact solar cells, optimize the morphology and size of the isolation region to improve photoelectric conversion efficiency, achieve good insulation effect, improve the passivation performance of the isolation region, reduce the damage to the cell caused by laser grooving, and avoid carriers from directly contacting the N-type doped region and the P-type doped region, which would prevent the carriers from being effectively collected, this application provides a back-contact solar cell and its preparation method.

[0007] The first direction of the semiconductor substrate described in this application is arranged laterally in the horizontal direction, and the second direction of the semiconductor substrate is perpendicular to the first direction in the vertical direction.

[0008] In a first aspect, this application provides a back-contact solar cell, employing the following technical solution:

[0009] A back-contact solar cell includes a front side and a back side disposed opposite to each other on a semiconductor substrate. The back side includes a first conductive region, a second conductive region, and an isolation structure unit. The first conductive region and the second conductive region have opposite conductivity types and are alternately arranged along a first direction of the semiconductor substrate. The isolation structure unit is located between the first conductive region and the second conductive region. The length of the isolation structure unit along the first direction is 20.0 μm to 200.0 μm. The isolation structure unit includes a first isolation region, a second isolation region, a third isolation region, a fourth isolation region, and a fifth isolation region with different isolation region morphologies.

[0010] Optionally, the semiconductor substrate is an N-type semiconductor, the first conductive region is a P-type conductive region, the second conductive region is an N-type conductive region, and the length of the isolation structure unit along the first direction can be 20.0 μm, 30.0 μm, 40.0 μm, or 50.0 μm. If the overall length of the isolation structure unit is too small, it will directly reduce the insulation effect of the isolation structure unit, leading to recombination of charge carriers on both sides of the isolation structure unit. If the overall length of the isolation structure unit is too large, it will increase the transport path of charge carriers in the first and second conductive regions along the first direction, that is, increase the series resistance of the battery and reduce the efficiency of the back contact battery.

[0011] By adopting the above technical solution, this application provides a back contact battery with five different isolation region morphologies by designing the structure of the isolation structure unit. Each isolation structure region has different beneficial effects during battery operation, so as to achieve good insulation effect, improve carrier collection efficiency, improve the passivation performance of the isolation structure unit, reduce the damage to the battery caused by laser grooving, and improve the photoelectric conversion efficiency of the back contact battery.

[0012] The tilted inverted pyramid of P-type doping in the first isolation region and the edge platform of N-type doping in the fifth isolation region are located at the junctions of the isolation structure unit and the first and second conductive regions, respectively. By controlling the morphology of these two regions, the isolation structure unit is designed as an asymmetric structure. The difference in collection efficiency between different types of charge carriers due to the asymmetric structure is utilized to improve the collection efficiency. This effectively avoids direct contact between the N-type and P-type doped regions, which would otherwise prevent the effective collection of charge carriers, thus improving the photoelectric conversion efficiency of the back-contact cell. Furthermore, the platform in the fifth isolation region, by reducing the area of ​​the doped layer, reduces parasitic absorption on the back side of the cell and also reduces damage to the semiconductor substrate caused by laser grooving, thereby improving the cell's front-end flyback (FF).

[0013] The unique tilted inverted pyramid structure of the first isolation zone can receive more sunlight transmitted from the front of the cell to the back and sunlight reflected from other directions on the back, improving the light trapping effect of the cell. Combined with the semiconductor substrate region with dense small pyramids in the third isolation zone, the reflectivity can be reduced, thereby further increasing the short-circuit current of the cell and ultimately improving the power of the module.

[0014] The large pyramid structure of the second and fourth isolation zones increases the deposition area of ​​the passivation film on the back of the battery, thereby further improving the passivation performance of the slotted area on the back of the battery.

[0015] Furthermore, in the fabrication process of the back contact battery, a low-temperature deposition process is used to prepare a highly dense doped layer, which can block laser energy to a greater extent, reduce damage to the battery, and also reduce the consumption of chemicals, thereby lowering production costs.

[0016] By designing the isolation structure unit to be composed of the first to fifth isolation regions mentioned above, an isolation structure region with different morphologies and gradient height changes is formed. This can achieve good insulation effect, improve carrier collection efficiency, and enhance the passivation performance of the isolation region, while reducing the damage to the battery caused by laser grooving.

[0017] Optionally, the first isolation region is located on the sidewall near the first conductive region. The length S1 of the first isolation region along the first direction is 0.5μm to 10.0μm, and the height H1 of the first isolation region along the second direction is 0.5μm to 7.0μm. The wall surface of the first isolation region has an inclined velvety inverted pyramid structure. The height of the pyramid structure of the first isolation region is 0.3 to 1.5μm, and the size of the base is 0.2μm to 1.5μm.

[0018] Optionally, the length S1 of the first isolation region along the first direction can be 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, or 10.0μm; the height H1 of the first isolation region along the second direction can be 0.5μm, 1.0μm, 2.0μm, 5.0μm, or 7.0μm.

[0019] If the length S1 of the first isolation region along the first direction is greater than 10.0 μm, the pyramid structure is too large, which is not conducive to the export of the drug solution after texturing and the subsequent deposition of the passivation and antireflection layer, thus affecting the battery efficiency; if the height H1 of the first isolation region in the second direction is less than 0.5 μm, there is a risk of the first conductive region and the second conductive region becoming connected.

[0020] By adopting the above technical solution, the first isolation region is located on the sidewall of the isolation structure unit in contact with the first conductive region. The first isolation region includes a P-type doped inclined inverted pyramid textured surface structure arranged along the second direction. The pyramid apex on the textured surface is inclined towards the center of the isolation structure region, thus forming a certain angle with the first direction. The unique inclined inverted pyramid structure of the first isolation region can receive more sunlight transmitted from the front of the battery to the back and sunlight reflected from other directions on the back, improving the light trapping effect of the battery, increasing the short-circuit current of the battery, and ultimately improving the module power.

[0021] Optionally, the second isolation region is connected to the side of the first isolation region away from the first conductive region. The length S2 of the second isolation region along the first direction is 0.5μm to 15.0μm. The wall surface of the second isolation region has a velvety pyramid structure, and the velvet density of the second isolation region is 50,000-70,000 pieces / mm². 2 The pyramid structure of the second isolation zone is arranged along the length of the first direction. The height of the pyramid structure of the second isolation zone is 0.3μm~1.5μm, and the size of the base is 0.3μm~1.5μm.

[0022] Optionally, the length S2 of the second isolation region along the first direction can be 1.0 μm, 2.0 μm, 3.0 μm or 4.0 μm.

[0023] Optionally, the third isolation zone is located on the side of the second isolation zone away from the first isolation zone. The length S3 of the third isolation zone along the first direction is 10.0 μm to 100.0 μm. The third isolation zone has a dense, small pile pyramid structure, and the pile density of the third isolation zone is 50,000-90,000 pieces / mm. 2 The pyramid structure of the third isolation zone is arranged along the length of the first direction, and the height of the pyramid structure of the third isolation zone is 0.1μm~1.5μm, and the size of the base is 0.1μm~1.0μm.

[0024] Optionally, the length S3 of the third isolation region along the first direction can be 10.0 μm, 20.0 μm, 30.0 μm or 40.0 μm.

[0025] If the length S3 of the third isolation region is less than 10.0 μm, it will reduce the overall texture density of the isolation structure unit, thereby reducing the absorption capacity of the back contact battery to sunlight. More importantly, the third isolation region plays a major insulating role in the isolation structure unit. If S3 is too small, it will directly reduce the insulation effect of the isolation structure unit, leading to carrier recombination on both sides of the isolation structure unit.

[0026] Optionally, the fourth isolation zone is located on the side of the third isolation zone away from the second isolation zone. The fourth isolation zone includes a bottom region and a sidewall region that intersect each other. The bottom region is located on the side closer to the third isolation zone, and the sidewall region is located on the side closer to the fifth isolation zone. The length S4 of the bottom region along the first direction is 0.5μm to 20.0μm, and the height H2 of the sidewall region along the second direction is 0.5μm to 7.0μm. The length S4' of the sidewall region along the first direction is 0.5μm to 15.0μm.

[0027] Optionally, the length S4 of the bottom region along the first direction can be 1.0 μm, 5.0 μm, 10.0 μm, or 15.0 μm, the length S4' of the sidewall region along the first direction can be 1.0 μm, 5.0 μm, 10.0 μm, or 15.0 μm, and the height H2 of the sidewall region along the second direction can be 1.0 μm, 2.0 μm, or 5.0 μm. If the height H2 of the fourth isolation region is less than 0.5 μm, there is a risk that the first conductive region 2 and the second conductive region 3 will become conductive.

[0028] The bottom region features a sparsely packed, large, pyramidal pile structure with a pile density of 10,000-40,000 particles / mm². 2The pyramid structure in the bottom region has a height of 0.3μm to 2.0μm and a base size of 0.3 to 2.0μm. The side wall region has a pyramid structure with a height of 0.2μm to 1.5μm and a base size of 0.2μm to 1.0μm.

[0029] Optionally, the fifth isolation region is located between the fourth isolation region and the second conductive region. The fifth isolation region is an N-type doped plateau and is parallel to the length direction of the first direction. The length S5 of the fifth isolation region along the first direction is 0.1 μm to 2.0 μm. Specifically, the length S5 of the fifth isolation region along the first direction can be 0.2 μm, 0.5 μm, 1.0 μm, or 1.2 μm.

[0030] Optionally, the first conductive region includes a first tunneling layer, a first doped layer, and a passivation antireflection layer deposited sequentially from the side near the semiconductor substrate to the side away from the semiconductor substrate. The first conductive region has an extension region on the side near the isolation structure unit. The extension region extends towards the side near the isolation structure unit and is located on the same horizontal plane as the first conductive region. The width D1 of the extension region along the first direction is 0.5μm~2.0μm.

[0031] Optionally, the length S3 of the third isolation zone along the first direction is greater than any one of the length S1 of the first isolation zone along the first direction, the length S2 of the second isolation zone along the first direction, the length S4 of the bottom region along the first direction, the length S4' of the side wall region along the first direction, the length S5 of the fifth isolation zone along the first direction, the height of the first isolation zone along the second direction, and the height H2 of the side wall region along the second direction.

[0032] Optionally, the sidewalls of both the first and fourth isolation zones are inclined, with the angle ∠1 between the first isolation zone and the first direction being 30° to 150°, and the angle ∠2 between the sidewall of the fourth isolation zone and the first direction being 30° to 160°.

[0033] Optionally, the angle ∠1 between the first isolation zone and the first direction can be 30°, 40°, 50°, or 60°. The angle ∠2 between the sidewall region of the fourth isolation zone and the first direction can be 30°, 40°, 50°, 60°, or 120°.

[0034] If the included angle ∠1 < 30°, the laser requires high precision and is not conducive to the deposition of the passivation and antireflection layer in the first isolation zone.

[0035] It is understandable that, since the height and size of the velvet pyramid structure in the same isolation structure area cannot be completely consistent, the height and size of the pyramid in each isolation area of ​​the isolation structure unit are given a certain range in the specification.

[0036] Secondly, this application provides a method for fabricating a back-contact solar cell, employing the following technical solution:

[0037] A method for fabricating a back-contact solar cell includes the following steps:

[0038] S1. Polishing the semiconductor substrate using an alkaline solution;

[0039] S2. A first tunneling layer and a first doped layer are deposited on the back side of the semiconductor substrate processed in step S1. The deposition temperature is 500-700℃, and the thickness of the first doped layer is 100-300nm. After thermal diffusion, a semiconductor substrate with a first mask deposited on its surface is obtained. Specifically, the temperature of the low-temperature deposition process can be 500℃, 600℃, or 700℃, preferably 600℃. The thickness of the first doped layer can be 100nm, 200nm, or 300nm, preferably 200nm. The doping concentration of the first doped layer is 2E19~1E20 atom / cm. 3 Preferably 5E19 atom / cm 3 The thickness of the first mask can be 50nm-70nm, preferably 60nm.

[0040] S3. After the first laser and wet etching process removes the first tunneling layer, the first doped layer and the first mask on the back side of the semiconductor substrate in step S2, a reserved second conductive region is formed, and a first isolation region, a second isolation region and an extension region are initially obtained.

[0041] S4. A second tunneling layer and a second doped layer are deposited on the back side of the semiconductor substrate processed in step S3, and after thermal diffusion, a semiconductor substrate with a second mask deposited on its surface is obtained. Specifically, the deposition temperature is 590-730℃, preferably 615℃; the thickness of the second doped layer is 130-320nm, preferably 240nm; and the doping concentration of the second doped layer is 4E20~1.5E21 atom / cm. 3 The preferred value is 1.4E21 atom / cm 3 The thickness of the second mask is 40-60 nm, preferably 45 nm.

[0042] S5. The second laser and wet etching process removes the second tunneling layer, the second doped layer, and the second mask covering the first conductive region on the back side of the semiconductor substrate in step S4, resulting in an extended region, a first isolation region, a second isolation region, a third isolation region, a fourth isolation region, and a fifth isolation region.

[0043] Specifically, inclined walls are prepared for the first and fourth isolation regions. The tilt angle of the laser ranges from 0 to 60°, with a preferred angle of 30°. The laser spot is rectangular, with a length and width ranging from 10 to 500 μm, preferably 300 μm in both dimensions. The single-pulse energy of the first laser is 83-98 μJ, with a preferred energy density of 90 μJ; the single-pulse energy of the second laser is 74-93 μJ, with a preferred energy density of 83 μJ.

[0044] S6. Deposit Al2O3 / SiN on the front and back sides of the semiconductor substrate processed in step S5 using ALD and PECVD equipment. x Passivation anti-reflection layer;

[0045] S7. Metal electrodes are printed on the first and second conductive areas on the back of the semiconductor processed in step S6 by screen printing. After sintering and photoinjection, the finished back contact cell is obtained.

[0046] Optionally, the sidewall morphology of the first and fourth isolation regions can be obtained by adjusting the laser spot shape, size, power, tilt angle and / or wet etching process. The larger the laser tilt angle, the larger the angle between the sidewall of the first and fourth isolation regions and the first direction, and the higher the precision requirements of the laser, which is not conducive to mass production.

[0047] Furthermore, since the height and size of the velvet pyramids in the same isolation structure area cannot be completely consistent, the range of pyramid height and size in each isolation structure area of ​​the isolation structure unit is given in the specification.

[0048] Understandably, in the process of preparing the first doped layer, a low-temperature deposition process is used to obtain a highly dense first doped layer. This first doped layer can block laser energy to a greater extent, reducing laser damage to the semiconductor substrate, and also reducing the loss of the first doped layer, thus lowering production costs. Simultaneously, because the first doped layer has less loss, a first conductive region extension can be obtained after laser or / or wet etching processes.

[0049] The passivation antireflection layer can be one or more of aluminum oxide, silicon nitride, silicon oxynitride, and silicon carbide. The large pyramid structure of the second and fourth isolation regions increases the contact area between the back of the battery and the passivation film, effectively reducing the recombination rate of charge carriers within the isolation structure unit, and ultimately improving the photoelectric conversion efficiency of the back contact battery.

[0050] The metal electrode can be one or more of silver, aluminum, and copper. After screen printing and sintering, the metal electrode contacts the first doped layer and / or the second doped layer to collect charge carriers in the corresponding regions and form a current.

[0051] In summary, this application has the following beneficial effects:

[0052] 1. This application provides a back contact battery with five different isolation region morphologies by designing the structure of the isolation structure unit. Each isolation region has different beneficial effects during battery operation, so as to achieve good insulation effect, improve carrier collection efficiency, improve the passivation performance of the isolation structure unit, reduce the damage to the battery caused by laser grooving, and improve the photoelectric conversion efficiency of the back contact battery.

[0053] The tilted inverted pyramid of P-type doping in the first isolation region and the edge platform of N-type doping in the fifth isolation region are located at the junctions of the isolation structure unit and the first and second conductive regions, respectively. By controlling the morphology of these two regions, the isolation structure unit is designed as an asymmetric structure. The difference in collection efficiency between different types of charge carriers due to the asymmetric structure is utilized to improve the collection efficiency. This effectively avoids direct contact between the N-type and P-type doped regions, which would otherwise prevent the effective collection of charge carriers, thus improving the photoelectric conversion efficiency of the back-contact cell. Furthermore, the platform in the fifth isolation region, by reducing the area of ​​the doped layer, reduces parasitic absorption on the back side of the cell and also reduces damage to the semiconductor substrate caused by laser grooving, thereby improving the cell's front-end flyback (FF).

[0054] The unique tilted inverted pyramid structure of the first isolation zone can receive more sunlight transmitted from the front of the cell to the back and sunlight reflected from other directions on the back, improving the light trapping effect of the cell. Combined with the semiconductor substrate region with dense small pyramids in the third isolation zone, the reflectivity can be reduced, thereby further increasing the short-circuit current of the cell and ultimately improving the power of the module.

[0055] The large pyramid structure of the second and fourth isolation zones increases the deposition area of ​​the passivation film on the back of the battery, thereby further improving the passivation performance of the slotted area on the back of the battery.

[0056] By designing the isolation structure unit to be composed of the first to fifth isolation regions mentioned above, an isolation structure region with different morphologies and gradient height changes is formed. This can achieve good insulation effect, improve carrier collection efficiency, and enhance the passivation performance of the isolation region, while reducing the damage to the battery caused by laser grooving.

[0057] 2. In the preparation process of the back contact battery, a high-density doped layer is prepared by low-temperature deposition process, which can block laser energy to a greater extent, reduce damage to the battery, and also reduce the consumption of chemicals, thereby reducing production costs. Attached Figure Description

[0058] Figure 1Schematic diagram of the first conductive region, the isolation structural unit, and the second conductive region. Figure 1 .

[0059] Figure 2 Schematic diagram of the first conductive region, the isolation structural unit, and the second conductive region. Figure 2 .

[0060] Figure 3 This is a flowchart of the battery cell fabrication process.

[0061] Figure 4 This is a topographical diagram of the isolated structural unit.

[0062] Figure 5 This is a topographical diagram of the first isolation zone, the second isolation zone, and the extension zone.

[0063] Figure 6 This is a topographical diagram of the third isolation zone.

[0064] Figure 7 The images show the topographical features of the fourth and fifth quarantine zones.

[0065] Figure 8 This is a schematic diagram of the isolation structure unit in Comparative Example 1.

[0066] Explanation of reference numerals in the attached figures: 1. Semiconductor substrate; 2. First conductive region; 20. First mask; 21. First tunneling layer; 22. First doped layer; 23. Extension region; 3. Second conductive region; 30. Second mask; 31. Second tunneling layer; 32. Second doped layer; 4. Isolation structure unit; 41. First isolation region; 42. Second isolation region; 43. Third isolation region; 44. Fourth isolation region; 441. Bottom region; 442. Sidewall region; 45. Fifth isolation region; 5. Metal electrode; 6. Passivation antireflection layer. Detailed Implementation

[0067] Unless otherwise specified, the experimental methods described in the following embodiments of the present invention are generally performed under conventional conditions or as recommended by the manufacturer. All commonly used chemical reagents used in the embodiments are commercially available products.

[0068] The following is in conjunction with the appendix Figure 1-8 This application will be described in further detail.

[0069] Example 1

[0070] Reference Figure 1 and Figure 2A back-contact solar cell includes a semiconductor substrate 1. The semiconductor substrate 1 is arranged laterally in a horizontal direction (denoted as a first direction) and perpendicularly in a vertical direction (denoted as a second direction). The semiconductor substrate 1 includes a front side and a back side disposed opposite to each other. The front side is deposited with a passivation and anti-reflection layer 6. The back side includes a first conductive region 2, a second conductive region 3, an isolation structure unit 4, and a metal electrode 5. The first conductive region 2 and the second conductive region 3 have opposite electrical properties and are alternately arranged along the first direction of the semiconductor substrate 1. The isolation structure unit 4 is located between the first conductive region 2 and the second conductive region 3, mainly serving to isolate the two different conductive regions on the back side of the cell to prevent carriers from being unable to be collected. If the overall length of the isolation structure unit 4 is too small, the insulation effect of the isolation structure unit 4 is reduced, leading to carrier recombination on both sides of the isolation structure unit 4. If the overall length of the isolation structure unit 4 is too large, it will increase the transport path of carriers in the first conductive region 2 and the second conductive region 3 along the first direction, i.e., increase the series resistance of the cell and reduce the efficiency of the back-contact cell.

[0071] Semiconductor substrate 1 is an N-type semiconductor, first conductive region 2 is a P-type conductive region, and second conductive region 3 is an N-type conductive region. First conductive region 2 includes a first tunneling layer 21, a first doped layer 22, and a passivation antireflection layer 6 deposited sequentially from the side closest to semiconductor substrate 1 to the side furthest from semiconductor substrate 1, with the metal electrode 5 forming an ohmic contact with the first doped layer 22. Second conductive region 3 includes a second tunneling layer 32, a second doped layer 32, and a passivation antireflection layer 6 deposited sequentially from the side closest to semiconductor substrate 1 to the side furthest from semiconductor substrate 1, with the metal electrode forming an ohmic contact with the second doped layer 32.

[0072] The isolation structure unit 4 includes a first isolation region 41, a second isolation region 42, a third isolation region 43, a fourth isolation region 44 and a fifth isolation region 45 arranged sequentially along a first direction. The first isolation region 41 is located on the side closer to the first conductive region 2, and the fifth isolation region 45 is located on the side closer to the second conductive region 3.

[0073] The first isolation region 41 is located on the sidewall near and connected to the first conductive region 2. The length S1 of the first isolation region 41 along the first direction is 0.6 μm, and the height H1 of the first isolation region 41 along the second direction is 4 μm. The angle ∠1 between the first isolation region 41 and the first direction is 60°. The first isolation region 41 includes P-type doped textured inverted pyramid structures arranged along the second direction. The apex of the textured pyramid structure tilts towards the direction near the third isolation region 43, thus the first isolation region 41 forms a certain angle with the first direction. The height of the pyramid structure of the first isolation region 41 is 0.3~1.5 μm, and the base size is 0.2 μm~1.5 μm. If the pyramid structure is too large, it will hinder the extraction of the drug solution after texturing and the subsequent deposition of the passivation and antireflection layer 6, affecting the battery efficiency.

[0074] The unique tilted inverted pyramid structure of the first isolation zone 41 can receive more sunlight transmitted from the front of the solar cell to the back and sunlight reflected from other directions on the back, improving the light trapping effect of the cell, increasing the short-circuit current of the cell, and ultimately increasing the module power.

[0075] The second isolation region 42 is located on the side of the first isolation region 41 away from the first conductive region 2. The length S2 of the second isolation region 42 along the first direction is 0.5 μm. The wall of the second isolation region 42 has a velvety pyramid structure, and the velvet density of the second isolation region 42 is 50,000-70,000 pieces / mm. 2 The pyramid structure of the second isolation zone 42 is arranged along the length of the first direction. The height of the pyramid structure of the second isolation zone 42 is 0.3μm~1.5μm, and the size of the base is 0.3μm~1.5μm.

[0076] The third isolation region 43 is located on the side of the second isolation region 42 away from the first isolation region 41, and the length S3 of the third isolation region 43 along the first direction is 100 μm. If the length S3 of the third isolation region 43 is less than 10.0 μm, the overall texture density of the isolation structure unit 4 will be reduced, thereby reducing the absorption capacity of the back of the back contact battery to sunlight. More importantly, the third isolation region 43 plays a major insulating role in the isolation structure unit 4. If S3 is too small, it will directly reduce the insulating effect of the isolation structure unit 4, leading to carrier recombination on both sides of the isolation structure unit 4.

[0077] The third isolation zone 43 has a dense, small pile pyramid structure, with a pile density of 50,000-90,000 pieces / mm. 2 The pyramid structure of the third isolation zone 43 is arranged along the length of the first direction. The height of the pyramid structure of the third isolation zone 43 is 0.1μm~1.5μm, and the size of the base is 0.1μm~1.0μm.

[0078] The fourth isolation zone 44 is located on the side of the third isolation zone 43 away from the second isolation zone 42. The fourth isolation zone 44 includes a bottom region 441 and a side wall region 442. The bottom region 441 is located on the side closer to the third isolation zone 43, and the side wall region 442 is located on the side closer to the fifth isolation zone 45. The length S4 of the bottom region 441 along the first direction is 0.5 μm, the length S4' of the side wall region 442 along the first direction is 0.5 μm, the height H2 of the side wall region 442 along the second direction is 2 μm, and the included angle ∠2 of the side wall region 442 along the first direction in the fourth isolation zone 44 is 120°.

[0079] The bottom region 441 features a sparse, large, upright pyramidal pile structure with a pile density of 10,000-40,000 piles / mm. 2The pyramid structure in the bottom region 441 has a height of 0.3μm to 2.0μm and a base size of 0.3 to 2.0μm. The side wall region 442 has a pyramid structure with a height of 0.2μm to 1.5μm and a base size of 0.2μm to 1.0μm.

[0080] The fifth isolation region 45 is located on the side of the fourth isolation region 44 near the second conductive region 3. The length of the fifth isolation region 45 along the first direction is 1.0 μm. The fifth isolation region 45 is an N-type doped platform and is parallel to the length direction of the first direction.

[0081] The first conductive region 2 has an extension region 23 on the side near the isolation structure unit 4. The extension region 23 extends towards the side near the isolation structure unit 4 and is located on the same horizontal plane as the first conductive region 2. The width D1 of the extension region 23 along the first direction is 0.8μm.

[0082] The first conductive region 2 is prepared by low-temperature deposition, resulting in a denser doped layer that can block laser energy to a greater extent. This makes it less susceptible to removal during wet cleaning, reducing the trench area and thus creating an extension region 23 of the first conductive region 2. This reduces battery damage. However, due to the parasitic absorption of the doped layer, energy loss occurs, so the length of the extension region 23 should not be too large. The second conductive region 3 is prepared by a high-temperature process, not low-temperature deposition, making the film layer easier to remove via laser trenching. This results in an N-type doped plateau region in the fifth isolation region 45. The trench area is controlled by limiting the length of the fifth isolation region 45. These two methods reduce laser trenching damage to the battery.

[0083] Reference Figure 3 A method for preparing a back contact solar cell includes the following steps:

[0084] S1. Polishing the semiconductor substrate 1 using an alkaline solution;

[0085] S2. A first tunneling layer and a first doped layer 22 are deposited on the back side of the semiconductor substrate 1 processed in step S1. The deposition temperature is 600℃ and the thickness of the first doped layer 22 is 200nm. After thermal diffusion, a semiconductor substrate 1 with a 60nm first mask 20 deposited on the surface is obtained.

[0086] S3. After removing the first tunneling layer, first doped layer 22 and first mask 20 on the back side of the semiconductor substrate 1 from step S2 by first laser and wet etching, a reserved second conductive region 3 is formed, and a first isolation region 41, a second isolation region 42 and an extension region 23 are initially obtained. The single pulse energy of the first laser is 90 μJ, the shape of the laser spot is rectangular, the length is 300 μm and the width is 300 μm, and the laser tilt angle for preparing the first isolation region 41 is 30°.

[0087] S4. A second tunneling layer 31 and a second doped layer 32 are deposited on the back side of the semiconductor substrate 1 processed in step S3. After thermal diffusion, a semiconductor substrate 1 with a second mask 30 deposited on its surface is obtained. The deposition temperature is 700℃, and the thickness of the second doped layer 32 is 240nm. The doping concentration of the second doped layer 32 is 1.4E21 atom / cm. 3 The thickness of the second mask 30 is 45nm.

[0088] S5. The second laser and wet etching process removes the second tunneling layer 31, the second doped layer 32, and the second mask 30 covering the first conductive region 2 on the back side of the semiconductor substrate 1 in step S4, resulting in the extended region 23, the first isolation region 41, the second isolation region 42, the third isolation region 43, the fourth isolation region 44, and the fifth isolation region 45. The single pulse energy of the second laser is 83 μJ, the shape of the laser spot is rectangular, the length is 300 μm, and the width is 300 μm. The tilt angle of the laser used to prepare the sidewall region 442 of the fourth isolation region 44 is 30°.

[0089] S6. Deposit Al2O3 / SiNx passivation and antireflection layers 6 on the front and back sides of the semiconductor substrate 1 processed in step S5.

[0090] S7. Metal electrodes 5 are printed on the first conductive region 2 and the second conductive region 3 on the back side of the semiconductor processed in step S6 by screen printing. After sintering and photoinjection, the finished back contact battery cell is obtained.

[0091] The morphology of the prepared solar cells was observed using a scanning electron microscope, and the test results are as follows: Figures 4-7 .

[0092] Example 2

[0093] A back-contact battery cell differs from Embodiment 1 in that the length S1 of the first isolation region 41 along the first direction is 0.8 μm, the height H1 of the first isolation region 41 along the second direction is 2 μm, and the angle ∠1 between the first isolation region 41 and the first direction is 30°.

[0094] The length S2 of the second isolation zone 42 along the first direction is 0.8 μm, and the length S3 of the third isolation zone 43 along the first direction is 70 μm.

[0095] The fourth isolation zone 44 includes a bottom region 441 and a sidewall region 442. The bottom region 441 and the sidewall region 442 intersect along a first direction. The length of the bottom region 441 along the first direction is 0.7 μm, the length of the sidewall region 442 along the first direction is 0.8 μm, the height H2 of the sidewall region 442 along the second direction is 2 μm, and the included angle ∠2 of the fourth isolation zone 44 along the first direction is 110°.

[0096] The fifth isolation zone 45 has a length of 0.5 μm along the first direction. The extension zone 23 has a length of 1.0 μm along the first direction.

[0097] Example 3

[0098] A back-contact battery cell differs from Embodiment 1 in that the length S1 of the first isolation region 41 along the first direction is 1.0 μm, the height H1 of the first isolation region 41 along the second direction is 2.5 μm, and the angle ∠1 between the first isolation region 41 and the first direction is 40°.

[0099] The length S2 of the second isolation zone 42 along the first direction is 1.0 μm, and the length S3 of the third isolation zone 43 along the first direction is 80 μm.

[0100] The fourth isolation zone 44 includes a bottom region 441 and a sidewall region 442. The bottom region 441 and the sidewall region 442 intersect along a first direction. The length of the bottom region 441 along the first direction is 1.0 μm, the length of the sidewall region 442 along the first direction is 0.5 μm, the height H2 of the sidewall region 442 along the second direction is 2.3 μm, and the included angle ∠2 of the fourth isolation zone 44 along the first direction is 100°.

[0101] The fifth isolation zone 45 has a length of 0.7 μm along the first direction. The extension zone 23 has a length of 1.2 μm along the first direction.

[0102] Example 4

[0103] A back-contact battery cell differs from Embodiment 1 in that the length S1 of the first isolation region 41 along the first direction is 1.4 μm, the height H1 of the first isolation region 41 along the second direction is 4.5 μm, and the angle ∠1 between the first isolation region 41 and the first direction is 50°.

[0104] The length S2 of the second isolation zone 42 along the first direction is 2.0 μm, and the length S3 of the third isolation zone 43 along the first direction is 90 μm.

[0105] The fourth isolation zone 44 includes a bottom region 441 and a sidewall region 442. The bottom region 441 and the sidewall region 442 intersect along a first direction. The length of the bottom region 441 along the first direction is 2.0 μm, the length of the sidewall region 442 along the first direction is 1.0 μm, the height H2 of the sidewall region 442 along the second direction is 3.0 μm, and the included angle ∠2 of the fourth isolation zone 44 along the first direction is 90°.

[0106] The fifth isolation zone 45 has a length of 1.0 μm along the first direction. The extension zone 23 has a length of 1.5 μm along the first direction.

[0107] Example 5

[0108] A back-contact battery cell differs from Embodiment 1 in that the length S1 of the first isolation region 41 along the first direction is 2.0 μm, the height H1 of the first isolation region 41 along the second direction is 5.0 μm, and the angle ∠1 between the first isolation region 41 and the first direction is 60°.

[0109] The length S2 of the second isolation zone 42 along the first direction is 2.0 μm, and the length S3 of the third isolation zone 43 along the first direction is 100 μm.

[0110] The fourth isolation zone 44 includes a bottom region 441 and a sidewall region 442. The bottom region 441 and the sidewall region 442 intersect along a first direction. The length of the bottom region 441 along the first direction is 2.5 μm, the length of the sidewall region 442 along the first direction is 1.5 μm, the height H2 of the sidewall region 442 along the second direction is 4.0 μm, and the included angle ∠2 of the fourth isolation zone 44 along the first direction is 80°.

[0111] The fifth isolation zone 45 has a length of 1.5 μm along the first direction. The extension zone 23 has a length of 1.0 μm along the first direction.

[0112] Example 6

[0113] A back-contact solar cell differs from Embodiment 1 in that the length S1 of the first isolation region 41 along the first direction is 12 μm, and the height H1 of the first isolation region 41 along the second direction is 0.1 μm.

[0114] Example 7

[0115] A back-contact solar cell differs from Embodiment 1 in that the length S3 of the third isolation region 43 along the first direction is 5 μm.

[0116] Comparative Example 1

[0117] Reference Figure 8 One type of back-contact battery cell differs from Embodiment 1 in that the isolation structure unit 4 has sidewalls and bottom walls with flat surfaces.

[0118] Performance testing

[0119] The solar cells prepared in Examples 1-7 and Comparative Example 1 were tested to measure their photoelectric conversion efficiency.

[0120] Table 1

[0121]

[0122] As can be seen from Examples 1-5 and Comparative Example 1, and in conjunction with Table 1, compared to the single isolation structure and flat surfaces on both sides of Comparative Example 1, the isolation structure units of Examples 1-5 have five regions with different morphological structures. While ensuring good insulation of the back-contact battery, this optimizes the carrier collection efficiency and the flyback effect (FF) of the battery cell at the boundary between the first and second conductive regions. Furthermore, dividing the isolation structure unit into regions with different morphological structures can effectively disperse the stress borne by the battery after laser grooving, preventing battery cracking and improving the reliability of the battery cell and module.

[0123] Combining Examples 1 and 6 with Table 1, it can be seen that Example 1 is superior to Example 6. The reason is that when the length S1 of the first isolation region along the first direction is greater than 10.0 μm, the pyramid structure is too large, which is not conducive to the export of the drug solution after texturing and the subsequent deposition of the passivation and antireflection layer, thus affecting the battery efficiency; when the height H1 of the first isolation region in the second direction is less than 0.5 μm, there is a risk of the first conductive region and the second conductive region becoming connected.

[0124] Combining Examples 1 and 7 with Table 1, it can be seen that Example 1 is superior to Example 7. The reason is that the length S3 of the third isolation region is less than 10.0 μm, which will reduce the overall texture density of the isolation structure unit, thereby reducing the absorption capacity of the back of the battery to sunlight. More importantly, the third isolation region plays a major insulating role in the isolation structure unit. If S3 is too small, it will directly reduce the insulation effect of the isolation structure unit, leading to carrier recombination on both sides of the isolation structure unit.

[0125] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A back-contact solar cell, characterized in that: The device includes a front side and a back side disposed opposite to each other on a semiconductor substrate (1). The back side includes a first conductive region (2), a second conductive region (3), and an isolation structure unit (4). The first conductive region (2) and the second conductive region (3) have opposite conductivity types and are arranged alternately along a first direction of the semiconductor substrate (1). The isolation structure unit (4) is located between the first conductive region (2) and the second conductive region (3). The length of the isolation structure unit (4) along the first direction is 20.0 μm to 200.0 μm. The isolation structure unit (4) includes a first isolation region (41), a second isolation region (42), a third isolation region (43), a fourth isolation region (44), and a fifth isolation region (45) with different isolation region morphologies.

2. The back-contact solar cell according to claim 1, characterized in that: The first isolation region (41) is located near the side wall of the first conductive region (2). The length S1 of the first isolation region (41) along the first direction is 0.5μm to 10.0μm, and the height H1 of the first isolation region (41) along the second direction is 0.5μm to 7.0μm. The wall of the first isolation region (41) has an inclined velvet inverted pyramid structure. The height of the pyramid structure of the first isolation region (41) is 0.3 to 1.5μm, and the size of the pyramid base is 0.2μm to 1.5μm.

3. A back-contact solar cell according to claim 2, characterized in that: The second isolation region (42) is connected to the side of the first isolation region (41) away from the first conductive region (2). The length S2 of the second isolation region (42) along the first direction is 0.5μm~15.0μm. The wall of the second isolation region (42) has a velvety pyramid structure. The velvet density of the second isolation region (42) is 50,000-70,000 pieces / mm. 2 The pyramid structure of the second isolation zone (42) is arranged along the length direction of the first direction. The height of the pyramid structure of the second isolation zone (42) is 0.3μm~1.5μm, and the size of the base is 0.3μm~1.5μm.

4. A back-contact solar cell according to claim 3, characterized in that: The third isolation zone (43) is located on the side of the second isolation zone (42) away from the first isolation zone (41). The length S3 of the third isolation zone (43) along the first direction is 10.0μm~100.0μm. The third isolation zone (43) is provided with a dense small pile pyramid structure. The pile density of the third isolation zone (43) is 50,000-90,000 pieces / mm. 2 The pyramid structure of the third isolation zone (43) is arranged along the length direction of the first direction. The height of the pyramid structure of the third isolation zone (43) is 0.1μm~1.5μm, and the size of the base is 0.1μm~1.0μm.

5. A back-contact solar cell according to claim 4, characterized in that: The fourth isolation zone (44) is located on the side of the third isolation zone (43) away from the second isolation zone (42). The fourth isolation zone (44) includes a bottom region (441) and a side wall region (442) that intersect each other. The bottom region (441) is located on the side closer to the third isolation zone (43), and the side wall region (442) is located on the side closer to the fifth isolation zone (45). The length S4 of the bottom region (441) along the first direction is 0.5μm to 20.0μm, and the height H2 of the side wall region (442) along the second direction is 0.5μm to 7.0μm. The length S4' of the side wall region (442) along the first direction is 0.5μm to 15.0μm. The bottom region (441) has a sparse, large, piled pyramidal structure with a pile density of 10,000-40,000 pieces / mm. 2 The height of the pyramid structure in the bottom region (441) is 0.3μm~2.0μm, and the size of the base is 0.3~2.0μm. The side wall region (442) has a pyramid structure, the height of the pyramid structure in the side wall region (442) is 0.2μm~1.5μm, and the size of the base is 0.2μm~1.0μm.

6. A back-contact solar cell according to claim 5, characterized in that: The fifth isolation region (45) is located between the fourth isolation region (44) and the second conductive region (3). The fifth isolation region (45) is an N-type doped platform and is parallel to the length direction of the first direction. The length S5 of the fifth isolation region (45) along the first direction is 0.1μm~2.0μm.

7. A back-contact solar cell according to claim 1, characterized in that: The first conductive region (2) includes a first tunneling layer (21), a first doped layer (22) and a passivation antireflection layer (6) deposited sequentially from the side near the semiconductor substrate (1) to the side away from the semiconductor substrate (1). The first conductive region (2) has an extension region (23) on the side near the isolation structure unit (4). The extension region (23) extends towards the side near the isolation structure unit (4) and is located on the same horizontal plane as the first conductive region (2). The width D1 of the extension region (23) along the first direction is 0.5μm~2.0μm.

8. A back-contact solar cell according to claim 6, characterized in that: The length S3 of the third isolation zone (43) along the first direction is greater than any one of the length S1 of the first isolation zone (41) along the first direction, the length S2 of the second isolation zone (42) along the first direction, the length S4 of the bottom region (441) along the first direction, the length S4' of the side wall region (442) along the first direction, the length S5 of the fifth isolation zone (45) along the first direction, the height of the first isolation zone (41) along the second direction, and the height H2 of the side wall region (442) along the second direction.

9. A back-contact solar cell according to claim 7, characterized in that: The side wall areas (442) of the first isolation zone (41) and the fourth isolation zone (44) are both inclined. The angle ∠1 between the first isolation zone (41) and the first direction is 30°~150°, and the angle ∠2 between the side wall area (442) of the fourth isolation zone (44) and the first direction is 30°~160°.

10. A method for preparing a back-contact solar cell according to any one of claims 1-9, characterized in that: Includes the following steps: S1. Polish the semiconductor substrate (1) using an alkaline solution; S2. A first tunneling layer and a first doped layer (22) are deposited on the back side of the semiconductor substrate (1) processed in step S1. The deposition temperature is 500-700℃, the thickness of the first doped layer (22) is 100-300nm, and after thermal diffusion, a semiconductor substrate (1) with a first mask (20) deposited on the surface is obtained. S3. After removing the first tunneling layer, first doped layer (22) and first mask (20) on the back side of the semiconductor substrate (1) in step S2 by first laser and wet etching, a reserved second conductive region (3) is formed, and a first isolation region (41), a second isolation region (42) and an extension region (23) are initially obtained. S4. A second tunneling layer (31) and a second doped layer (32) are deposited on the back side of the semiconductor substrate (1) processed in step S3, and after thermal diffusion, a semiconductor substrate (1) with a second mask (30) deposited on the surface is obtained. The deposition temperature is 590℃-730℃, and the thickness of the second doped layer (32) is 130nm-320nm. S5. The second laser and wet etching process removes the second tunneling layer (31), the second doped layer (32) and the second mask (30) on the back side of the semiconductor substrate (1) in step S4, which are covered on the first conductive region (2), to obtain the extended region (23), the first isolation region (41), the second isolation region (42), the third isolation region (43), the fourth isolation region (44) and the fifth isolation region (45). S6. Deposit Al2O3 / SiNx passivation and antireflection layers (6) on the front and back sides of the semiconductor substrate (1) processed in step S5. S7. Metal electrodes (5) are printed on the first conductive area (2) and the second conductive area (3) on the back side of the semiconductor processed in step S6 by screen printing. After sintering and photoinjection, the finished back contact battery cell is obtained.

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