Ultrathin solar cells and photovoltaic modules with selective poly-silicon passivation contacts

Abstract

The utility model discloses a kind of ultra-thin solar cells and photovoltaic modules with selective polysilicon passivation contact, wherein ultra-thin solar cell includes N-type silicon wafer substrate, a plurality of patterning structures are provided on the back of N-type silicon wafer substrate, patterning structure includes resonant cavity structure and recessed structure, resonant cavity structure is the convex structure projecting to silicon wafer back surface, recessed structure is the structure recessed to substrate interior between adjacent two resonant cavity structures;Resonant cavity structure includes first resonant cavity and second resonant cavity, first resonant cavity is located in the metal contact area of the back of N-type silicon wafer substrate, second resonant cavity and recessed structure are located in the non-metal contact area of the back of N-type silicon wafer substrate.The utility model can save silicon wafer cost, with good flexibility, can improve the current value of battery, is conducive to the more efficient transmission of carrier.

Description

Technical Field

[0001] This invention belongs to the field of ultrathin solar cells, specifically relating to an ultrathin solar cell with selective polycrystalline silicon passivated contacts. Background Technology

[0002] The emergence of TOPCon tunneling oxide passivated contact solar cells has attracted significant attention to high-efficiency crystalline silicon solar cell technology. TOPCon cells use N-type silicon as the substrate material and consist of an ultrathin silicon oxide layer and a highly doped polycrystalline silicon layer. Because the tunneling potential of the tunneling oxide layer (4.5 eV) is higher than the electron tunneling potential (3.1 eV), it reduces carrier recombination between the metal electrode and silicon, making it easier for electrons to tunnel and be collected. Another function of the tunneling oxide layer is full-area passivation; its excellent passivation capability further improves the efficiency of TOPCon solar cells. Currently, the photoelectric conversion efficiency record for TOPCon cells has exceeded 26.5%.

[0003] Since 2023, the photovoltaic industry has faced overcapacity issues, and cost reduction and efficiency improvement have become the main themes of solar cell development. Research has shown that ultra-thin solar cells, which are one-third the thickness of conventional solar cells, have unique potential. While efficiently converting solar energy into electrical energy, they also achieve cost advantages through material savings. At the same time, ultra-thin solar cells have good flexibility and can be bent or rolled, which allows them to be installed on surfaces with various complex shapes. In addition, because the carrier transport path is shorter during the lifetime of ultra-thin solar cells, it helps to reduce the problem of shortened carrier lifetime caused by substrate defects.

[0004] Currently, advanced crystalline silicon solar cells generally have a thickness ranging from 110µm to 150µm. Based on different technological approaches, they can be broadly categorized into TOPCon, HJT, and BC types. TOPCon cells improve power generation efficiency by fabricating an ultrathin tunneling oxide layer and a highly doped polycrystalline silicon film in the metal electrode contact area to form a passivated contact structure. HJT cells passivate by depositing intrinsic amorphous silicon films and P / N-type amorphous silicon films on both the front and back sides, followed by the deposition of a transparent conductive film (TCO) for conductivity. BC cells increase current by placing all metal grid lines on the back of the cell, serving as a platform technology for upgrading TOPCon or HJT cells. Currently, TOPCon holds a mainstream position due to its low cost, high reliability, and high market acceptance.

[0005] Meanwhile, other studies have found that, based on HJT cells, by using low-damage continuous plasma vapor deposition to prevent passivation layer damage and combining it with laser transfer technology, high-efficiency solar cells of different thicknesses were fabricated. Compared to the baseline thickness of 125µm, the efficiency decreased by 0.25% for 106µm thickness, 0.31% for 84µm thickness, 0.62% for 74µm thickness, and 0.75% for 57µm thickness. The 57µm flexible ultrathin solar cell exhibited the highest power-to-weight ratio. This indicates that the efficiency decrease caused by cell thinning is not linear, and that cell thinning also reduces the weight and cost of the solar cell.

[0006] However, there are also some problems with the existing technology: 1. Currently, only HJT batteries have the laboratory-scale manufacturing process for ultra-thin batteries. TOPCon, as the most mainstream type of solar cell, does not currently have the corresponding ultra-thin battery technology for mass production. 2. While reducing the thickness of crystalline silicon, ultra-thin batteries reduce the light absorption rate of the silicon wafer as the light-absorbing layer thins, leading to a decrease in battery current density and thus affecting the photoelectric conversion efficiency of solar cells. 3. Conventional TOPCon solar cell structures have a full-surface deposition of phosphorus-doped polycrystalline silicon on the back. While heavily doped polycrystalline silicon helps reduce the contact resistance between silicon and metal and improves the cell's fill factor, it also exhibits free carrier absorption, leading to severe parasitic absorption of long-wavelength photons and a decrease in current density. In ultra-thin cells, the thinner silicon wafer reduces light absorption, causing long-wavelength photons to undergo multiple reflections within the wafer, increasing the number of times they pass through the heavily doped polycrystalline silicon layer. Compared to TOPCon cells with normal-thickness silicon wafers, the parasitic absorption losses from the heavily doped polycrystalline silicon layer are further amplified in ultra-thin silicon TOPCon cells. Summary of the Invention

[0007] The purpose of this invention is to provide an ultrathin solar cell structure with selective polycrystalline silicon passivation contacts based on existing technology. It features a tunneling oxide layer and doped polycrystalline silicon passivation, filling the gap in the fabrication process of TOPCon cells for ultrathin solar cells.

[0008] The ultrathin solar cell of this invention differs from the polished back surface of conventional cells. Based on ultrathin crystalline silicon (20µm~100µm), this invention adopts a patterned structural design on the back of the silicon substrate. This design can form a resonant cavity structure, which effectively increases the effective optical path length of absorbed light within the cell. Through optical effects, it enhances the current value of the solar cell and can compensate for the negative impact of reduced cell thickness on the current value.

[0009] This invention forms a selective polycrystalline silicon passivation contact structure on the back surface of a TOPCon battery. Unlike conventional TOPCon batteries where phosphorus-doped polycrystalline silicon is deposited over the entire back surface, this invention only sets a tunneling oxide layer and a doped polycrystalline silicon layer on the resonant cavity structure corresponding to the metallized region. This approach can effectively reduce the parasitic absorption of doped polycrystalline silicon and increase the current value. The conductivity of doped polycrystalline silicon is equivalent to that of metallic materials, and this design is more conducive to the transport of charge carriers.

[0010] The technical solution of this utility model is: An ultrathin solar cell with selective polycrystalline silicon passivated contacts includes an N-type silicon wafer substrate. Multiple patterned structures are disposed on the back side of the N-type silicon wafer substrate. The patterned structures include resonant cavity structures and recessed structures. The resonant cavity structures are protruding structures extending towards the back surface of the silicon wafer, and the recessed structures are structures located between two adjacent resonant cavity structures and recessed into the substrate. The resonant cavity structure includes a first resonant cavity and a second resonant cavity. The first resonant cavity is located in the metal contact region of the back surface of the silicon wafer, and the second resonant cavity and the recessed structures are located in the non-metallic contact region of the back surface of the silicon wafer. A tunneling oxide layer and a phosphorus-doped polycrystalline silicon layer are sequentially disposed from the inside to the outside in the metal contact area on the back side of the N-type silicon wafer substrate. The N-type silicon substrate is ultrathin crystalline silicon; the depth D of the first resonant cavity and the second resonant cavity are independently 0.5µm to 10µm, the width W of the protruding top of the first resonant cavity and the second resonant cavity are independently 20µm to 200µm, and the width S of the recessed structure is 50µm to 1000µm.

[0011] In a preferred embodiment, the depth D of the first resonant cavity and the second resonant cavity are independently 1µm to 5µm, the width W of the protruding top of the first resonant cavity and the second resonant cavity are independently 40µm to 100µm, and the width S of the recessed structure is 100µm to 1000µm.

[0012] In this invention, the depth D of each first resonant cavity and each second resonant cavity may be the same or different, the width W of the protruding top of each first resonant cavity and each second resonant cavity may be the same or different, and the width S of each recessed structure may be the same or different. Furthermore, as... Figure 4As shown, the battery back surface of this utility model is designed with a resonant structure based on light-harvesting capability. The depth (i.e., the height of the protrusion) D of each protrusion structure forming the resonant cavity structure can be the same or different, i.e., D1 = D2 or D1 ≠ D2. The width W of the top of the protrusion of each protrusion structure forming the resonant cavity structure can also be the same or different, i.e., W1 = W2 or W1 ≠ W2. The width S of the recessed structure can be the same or different, i.e., S1 = S2 or S1 ≠ S2. Each resonant cavity structure is periodically distributed or aperiodically distributed. Within a single non-metallized region, the number of second resonant cavities is greater than or equal to 2.

[0013] In a preferred embodiment, the number of second resonant cavities within a single non-metallic contact region is n, and n≥2.

[0014] The thickness of the ultrathin crystalline silicon in the N-type silicon wafer substrate of this invention is 20µm to 100µm.

[0015] The present invention further provides a back surface passivation antireflection film on the phosphorus-doped polycrystalline silicon layer in the metal contact area on the back side of the N-type silicon wafer substrate, and on the non-metal contact area on the back side of the N-type silicon wafer substrate.

[0016] In a preferred embodiment, the front side of the N-type silicon wafer substrate is provided with a boron-doped emitter layer and a front surface passivation antireflection film, arranged sequentially from the inside to the outside.

[0017] The front or rear passivation antireflection film in this invention can be designed as a stacked film, that is, the passivation antireflection film can be made of two of the following: aluminum oxide, silicon nitride, silicon dioxide, and silicon oxynitride; preferably, an aluminum oxide + silicon nitride passivation antireflection film stacked design is adopted.

[0018] In a preferred embodiment, the front surface passivation antireflection film or the back surface passivation antireflection film includes an aluminum oxide layer and a silicon nitride layer, wherein the thickness of the aluminum oxide layer is 1–10 nm and the thickness of the silicon nitride layer is 20–50 nm.

[0019] In a preferred embodiment, the thickness of the tunneling oxide layer is 0.5 nm to 2.5 nm.

[0020] In a preferred embodiment, the thickness of the phosphorus-doped polycrystalline silicon layer is 60–200 nm.

[0021] This utility model discloses a photovoltaic module, which includes a front encapsulation layer, a photovoltaic cell and a back encapsulation layer, wherein the photovoltaic cell is an ultra-thin solar cell with selective polycrystalline silicon passivated contacts as described in this utility model.

[0022] This invention is based on the application of ultra-thin solar cells. After the boron diffusion process is completed on the silicon wafer, a patterned structure is formed on the entire back surface of the silicon wafer using laser technology and wet processing. The depth is D (i.e., the protrusion depth D of the resonant cavity), the width of the un-laser-etched area is W (i.e., the width of the protrusion top W), and the width of the laser-etched area is S (i.e., the width of the recess S) (see appendix). Figure 4 This resonant structure effectively increases the reflection path length of absorbed light within the silicon substrate, thereby enhancing the current value of the solar cell. Compared to the polished back surface of conventional cells, where long-wavelength light undergoes conventional specular reflection upon reaching the back surface, in this resonant structure, some long-wavelength light is trapped within the structure, forming an additional reflection path (see Appendix). Figure 10 Meanwhile, on the back of the battery structure, laser technology is used to completely ablate the doped polysilicon in the non-metallic grid area, reducing the negative impact of parasitic absorption of the doped polysilicon on the battery current value. In addition, the conductivity of the heavily doped polysilicon layer is similar to that of metal, and the retention of some doped polysilicon in direct contact with the substrate silicon is more conducive to the transport of charge carriers.

[0023] By comparing three different TOPCon solar cell structures, this invention has the following advantages: ① This utility model is designed based on ultra-thin batteries. Compared with conventional thickness TOPCon batteries, ultra-thin solar cells have the advantage of saving silicon wafer costs. For example, the silicon wafer thickness used in conventional TOPCon batteries is 120~130µm. If a thin silicon wafer material of 40µm is used, the cost of silicon wafers can be reduced to 1 / 3 of the original. At the same time, ultra-thin solar cells have good flexibility and can be bent or rolled, making them more suitable for distributed scenarios such as industrial and commercial rooftops. ② The design of the resonant structure on the back surface of the battery can effectively increase the length of the reflection path of absorbed light in the silicon substrate, thereby improving the battery's current value. Compared with the polished back surface of conventional batteries, where long-wavelength light undergoes conventional specular reflection upon reaching the battery's back surface, in this structure, some mid-to-long-wavelength light will be trapped in this resonant structure and undergo multiple reflections. This can compensate for the negative impact on the battery current value caused by the reduction in battery thickness and the decrease in the light-absorbing layer (see appendix). Figure 10 ); ③ In this utility model, the doped polycrystalline silicon in the non-metallized region on the back of the battery structure is dissolved to reduce the negative impact of parasitic absorption of the doped polycrystalline silicon on the battery current value. ④ The tunneling oxide layer + doped polycrystalline silicon structure of the first resonant cavity is retained. For ultra-thin batteries, the retention of the passivation layer on both sides of the first resonant cavity structure increases the area for carrier transport, which is conducive to more efficient carrier transport. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the silicon wafer structure after texturing in step S1 of this utility model; Figure 2 This is a schematic diagram of the silicon wafer structure after double-sided boron diffusion in step S2 of this utility model; Figure 3 This is a schematic diagram of the silicon wafer structure after laser pre-fabrication of the resonant cavity structure in step S3 of this utility model; Figure 4 This is a schematic diagram of the silicon wafer resonant cavity structure formed in step S4 of this utility model; Figure 5 This is a schematic diagram of the silicon wafer structure after the phosphorus-doped polycrystalline silicon layer is formed in step S5 of this utility model. Figure 6 This is a schematic diagram of the silicon wafer structure in step S5 of this utility model, showing the removal of the tunneling oxide layer and the doped polycrystalline silicon layer in the non-metallic contact area. Figure 7 This is a schematic diagram of the silicon wafer structure after the passivation antireflection film is formed in step S6 of this utility model; Figure 8 This is a schematic diagram of a conventional TOPCon solar cell structure. Figure 9 This is a structural diagram of a TOPCon solar cell with selective polycrystalline silicon contacts under existing technology; Figure 10 This is an ultrathin solar cell structure with a resonant structure on the back surface to enhance light-harvesting ability and selective polycrystalline silicon passivation capability, as described in Embodiment 1 of this utility model. Figure 11 This is another ultrathin solar cell structure with a resonant structure on the back surface to enhance light-harvesting capability and selective polycrystalline silicon passivation capability, as described in Embodiment 2 of this utility model. In the figure, 1-N-type silicon substrate, 2-boron-doped emitter, 3-patterned structure, 31-first resonant cavity, 32-second resonant cavity, 33-recessed structure, 4-tunneling oxide layer, 5-phosphorus-doped polycrystalline silicon layer, 61-front surface passivation antireflection film, 62-back surface passivation antireflection film, 71-front surface metal electrode, 72-back surface metal electrode. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to the following examples.

[0026] The present invention can be better understood from the following embodiments. However, those skilled in the art will readily understand that the description of the embodiments is for illustrative purposes only and should not, and will not, limit the present invention as described in detail in the claims.

[0027] The TOPCon battery mentioned in this utility model is officially called a tunnel oxide passivated contact solar cell.

[0028] like Figure 10-11 As shown, the present invention discloses an ultrathin solar cell with selective polycrystalline silicon passivated contacts, comprising an N-type silicon wafer substrate, wherein the N-type silicon wafer substrate is an ultrathin crystalline silicon with a thickness of 20µm to 100µm; the back side of the N-type silicon wafer substrate includes a metal contact region and a non-metal contact region.

[0029] Multiple patterned structures 3 with multiple resonant cavities are formed on the back side of a silicon wafer using a boron-expanded laser and wet process. The patterned structure 3 includes multiple resonant cavity structures and multiple recessed structures 33. The resonant cavity structure is a protruding structure that protrudes towards the back surface of the silicon wafer, including a first resonant cavity 31 and a second resonant cavity 32. The recessed structure 33 is located between two adjacent resonant cavity structures and is recessed into the silicon wafer. The first resonant cavity 31 is located in the metal contact area, and the second resonant cavity 32 and the recessed structure 33 are located in the non-metal contact area.

[0030] The N-type silicon substrate is made of ultrathin crystalline silicon with a thickness of 20µm to 100µm.

[0031] The depth D of the first and second resonant cavities is independently 1µm to 5µm, the width W of the protruding tops of the first and second resonant cavities is independently 40µm to 100µm, and the width S of the recessed structure is 100µm to 1000µm. The depth D of each first and second resonant cavity may be the same or different, the width W of the protruding tops of each first and second resonant cavity may be the same or different, and the width S of each recessed structure may be the same or different. Furthermore, with... Figure 4 For example, the back surface of the battery of this utility model is designed with a resonant structure based on light-harvesting capability. The depth (i.e., the height of the protrusion) D of each protrusion structure forming a resonant cavity structure can be the same or different, i.e., D1 = D2 or D1 ≠ D2. The width W of the top of each protrusion structure forming a resonant cavity structure can also be the same or different, i.e., W1 = W2 or W1 ≠ W2. The width S of the recessed structure can be the same or different, i.e., S1 = S2 or S1 ≠ S2.

[0032] Within a single non-metallic contact region, the number of second resonant cavities is n, and n≥2.

[0033] In one specific embodiment, a single patterned structure in this application includes a first resonant cavity, multiple second resonant cavities, and multiple recessed structures between the resonant cavities. The range of the single patterned structure includes an adjacent metal contact region and a non-metal contact region.

[0034] On the metal contact region on the back side of the N-type silicon substrate, a tunneling oxide layer 4 and a phosphorus-doped polycrystalline silicon layer 5 are sequentially disposed from the inside out. The thickness of the tunneling oxide layer 4 is 0.5 nm to 2.5 nm. The thickness of the phosphorus-doped polycrystalline silicon layer 5 is 60 nm to 200 nm.

[0035] A back surface passivation antireflection film 62 is provided on the phosphorus-doped polycrystalline silicon layer 5 in the metal contact area on the back side of the N-type silicon wafer substrate and on the non-metal contact area on the back side of the N-type silicon wafer substrate.

[0036] On the front side of the N-type silicon wafer substrate, a boron-doped emitter layer 2 and a front surface passivation antireflection film 61 are sequentially arranged from the inside to the outside.

[0037] The passivation antireflection film on the front surface or the passivation antireflection film on the back surface can be designed as a stacked film, that is, the passivation antireflection film can be two of the following: aluminum oxide layer, silicon nitride layer, silicon dioxide layer, and silicon oxynitride layer; preferably, an aluminum oxide + silicon nitride passivation antireflection film stacked design is adopted, that is, the passivation antireflection film includes an aluminum oxide layer and a silicon nitride layer, the thickness of the aluminum oxide layer is 1-10 nm, and the thickness of the silicon nitride layer is 20-50 nm.

[0038] A front surface metal electrode 71 is provided on the front side of the N-type silicon wafer substrate, and a back surface metal electrode 72 is provided in the metal contact area on the back side of the N-type silicon wafer substrate.

[0039] The ultrathin solar cell with selective polycrystalline silicon passivated contact of this invention can be directly applied to photovoltaic modules.

[0040] This invention also includes a photovoltaic module, which includes a front encapsulation layer, a photovoltaic cell, and a back encapsulation layer, wherein the photovoltaic cell is an ultra-thin solar cell with selective polycrystalline silicon passivated contacts as described in this invention.

[0041] The ultrathin solar cell with selective polycrystalline silicon passivated contacts of this invention can be prepared by the following method: S1. Perform wet cleaning on N-type monocrystalline silicon wafers to remove the damaged layer on the wafer surface, clean surface metal impurities and oil stains, and create a textured surface (see attached). Figure 1 (As shown).

[0042] S2. Perform a double-sided boron diffusion process on the texturized silicon wafer to form surface emitters (see appendix). Figure 2 (As shown).

[0043] S3. Laser-based prefabrication of patterned structures. After double-sided boron diffusion on the silicon wafer, a laser is used to ablate the back surface of the silicon wafer, forming a recessed structure.

[0044] S4. Wet polishing and etching are performed on the back surface of the battery to form a patterned structure with multiple resonant cavities. The laser-irradiated areas from the previous process have poor corrosion resistance due to surface modification, so they are etched downwards to a certain depth. The areas without laser irradiation form the polished surface of the silicon substrate, ultimately forming the resonant cavity structure. The resonant cavity structures can be periodically or aperiodically distributed, and the depth or width of the downward protrusion of each resonant cavity structure can be consistent or inconsistent. The number of second resonant cavities within a single non-metallized region is greater than or equal to two (see appendix). Figure 4 (As shown).

[0045] S5. Preparation of selective tunneling oxide layer and doped polycrystalline silicon layer on the back surface. Using low-pressure chemical vapor deposition (LPCVD) or plasma-enhanced chemical vapor deposition (PECVD), an ultrathin tunneling oxide layer is deposited on the back surface under high-temperature conditions with oxygen flow. Under low-pressure conditions, silane (SiH4) reacts on the back surface of the silicon wafer to deposit and grow a polycrystalline silicon layer. Then, through a phosphorus diffusion process, phosphorus atoms are introduced into the intrinsic polycrystalline silicon layer to form a phosphorus-doped polycrystalline silicon layer (see appendix). Figure 5 (As shown).

[0046] Secondly, using laser technology and wet processing, the excess doped polysilicon in the non-metallized region is removed, leaving only the tunnel oxide layer and doped polysilicon layer structure in the remaining metallized region (see Appendix). Figure 6 (As shown).

[0047] S6. Deposition of passivation and antireflection films on the front and rear surfaces. The passivation and antireflection films on the front and rear surfaces adopt a stacked design of alumina + silicon nitride passivation and antireflection films (see appendix). Figure 7 (As shown).

[0048] S7. Printing and sintering of metal electrodes on the front and back surfaces.

[0049] During the fabrication process, the laser parameters in step S3 and the etching parameters in step S4 can be adjusted to form first resonant cavities, second resonant cavities, and recessed structures of different sizes.

[0050] by Figure 10For example, in this scheme, the depth and width of each resonant cavity structure are the same and are periodically distributed. The number of second resonant cavities in a single non-metallized region is n=2; the widths of the protruding tops of the two second resonant cavities 32 in a single non-metallized region are W1 and W2, W1=W2=60µm; the depths of the two second resonant cavities in a single non-metallized region are D1 and D2, D1=D2=5µm; the widths of the two recessed structures in a single non-metallized region are S1 and S2, S1=S2=200µm (this product is marked as Example 1).

[0051] by Figure 11 For example, in this scheme, the depth and width of each resonant cavity structure are different and not periodically distributed. The number of second resonant cavities in a single non-metallized region is n=2; the widths of the protruding tops of the two second resonant cavities 32 in a single non-metallized region are W1 and W2, W1=30µm and W2=100µm; the depths of the two second resonant cavities in a single non-metallized region are D1 and D2, D1=2µm and D2=5µm; the widths of the two recessed structures in a single non-metallized region are S1 and S2, S1=100µm and S2=500µm (this product is marked as Example 2).

[0052] A conventional TOPCon cell structure with a thickness of 130µm is used as a comparative example 1.

[0053] Comparative Example 2 uses a conventional TOPCon structure battery with a thickness of 40µm (its structure is shown in the appendix). Figure 8 ).

[0054] Comparative Example 3 uses a 40µm thick selectively passivated polycrystalline silicon solar cell from the prior art (its structure is shown in Appendix). Figure 9 ).

[0055] The electrical performance of each batch of solar cells obtained in Examples 1 and 2 and Comparative Examples 1-3 was tested, and the results are shown in Table 1.

[0056] Table 1

[0057] In this table, the electrical performance data for each type of solution is the average data for a 100Pcs battery.

[0058] Analysis of Table 1 shows that: 1) Compared to Comparative Example 1, Comparative Examples 2 / 3 and Example 1 / 2 have fewer light-absorbing layers due to the thinning of the battery, which has a negative impact on the current density value of the battery; while Comparative Examples 2 / 3 and Example 1 / 2 have an advantage in cost as ultra-thin solar cells, and the open circuit voltage is improved due to fewer bulk defects.

[0059] 2) Compared with Comparative Example 2 / 3, Example 1 / 2 adopts the solar cell structure with selective polycrystalline silicon passivated contact designed in this invention. The resonant structure on the back of the cell increases the propagation path length of light inside the cell through optical effects, thereby increasing the current density value.

[0060] 3) Compared with Example 1, the resonant structure designed on the back of Example 2 has a non-periodic distribution pattern, which makes the propagation path of long-wavelength light inside the battery longer and can improve the current density value.

[0061] In summary, the ultrathin solar cell structure with selective polycrystalline silicon passivated contacts designed in this invention has the advantages of low cost and high efficiency.

[0062] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and inventive concept of the present utility model, should be included within the protection scope of the present utility model.

Claims

1. An ultra-thin solar cell with selective poly-silicon passivated contact comprising an N-type silicon wafer substrate (1) characterized in that, Multiple patterned structures (3) are provided on the back side of the N-type silicon substrate (1). The patterned structure (3) includes a resonant cavity structure and a recessed structure (33). The resonant cavity structure is a protruding structure protruding towards the back surface of the silicon wafer, and the recessed structure (33) is a structure located between two adjacent resonant cavity structures and recessed into the substrate. The resonant cavity structure includes a first resonant cavity (31) and a second resonant cavity (32). The first resonant cavity (31) is located in the metal contact area of ​​the back surface of the silicon wafer, and the second resonant cavity (32) and the recessed structure (33) are located in the non-metal contact area of ​​the back surface of the silicon wafer. In the metal contact area on the back side of the N-type silicon wafer substrate (1), a tunneling oxide layer (4) and a phosphorus-doped polycrystalline silicon layer (5) are sequentially provided from the inside to the outside. The N-type silicon substrate is ultrathin crystalline silicon; the depth D of the first resonant cavity (31) and the second resonant cavity (32) are independently 0.5µm to 10µm, the width W of the protruding top of the first resonant cavity (31) and the second resonant cavity (32) are independently 20µm to 200µm, and the width S of the recessed structure (33) is 50µm to 1000µm.

2. The ultra-thin solar cell with selective poly-silicon passivated contact according to claim 1, wherein, The depth D of the first resonant cavity (31) and the second resonant cavity (32) are independently 1µm to 5µm, the width W of the protruding top of the first resonant cavity (31) and the second resonant cavity (32) is independently 40µm to 100µm, and the width S of the recessed structure (33) is 100µm to 1000µm.

3. The ultra-thin solar cell with selective poly-silicon passivated contact according to claim 1, wherein, The depth D of each of the first resonant cavities (31) and each of the second resonant cavities (32) is the same or different, the width W of the protruding top of each of the first resonant cavities (31) and each of the second resonant cavities (32) is the same or different, and the width S of each of the recessed structures (33) is the same or different.

4. The ultra-thin solar cell with selective poly-silicon passivated contact of claim 1, wherein, The number of the second resonant cavities (32) in a single non-metallic contact area is n, and n≥2.

5. The ultra-thin solar cell with selective poly-silicon passivated contact according to claim 1, wherein, The thickness of the ultrathin crystalline silicon in the N-type silicon substrate is 20µm to 100µm.

6. The ultra-thin solar cell with selective poly-silicon passivated contact of claim 1, wherein, A back surface passivation antireflection film (62) is provided on the phosphorus-doped polycrystalline silicon layer (5) in the metal contact area on the back side of the N-type silicon wafer substrate (1) and on the non-metal contact area on the back side of the N-type silicon wafer substrate (1).

7. The ultra-thin solar cell with selective poly-silicon passivated contact according to claim 6, wherein The front side of the N-type silicon wafer substrate is provided with a boron-doped emitter layer (2) and a front surface passivation antireflection film (61) from the inside to the outside.

8. The ultrathin solar cell with selective poly-silicon passivated contact according to claim 7, wherein The front or rear passivation antireflection film comprises an aluminum oxide layer and a silicon nitride layer, wherein the thickness of the aluminum oxide layer is 1–10 nm and the thickness of the silicon nitride layer is 20–50 nm.

9. The ultrathin solar cell with selective poly-silicon passivated contact of claim 1, wherein The thickness of the tunneling oxide layer (4) is 0.5 nm to 2.5 nm, and the thickness of the phosphorus-doped polycrystalline silicon layer (5) is 60 to 200 nm.

10. A photovoltaic module comprising a front encapsulant layer, a photovoltaic cell, and a back encapsulant layer, characterized by: The photovoltaic cell is an ultrathin solar cell with selective polycrystalline silicon passivated contacts as described in any one of claims 1 to 9.

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