Back contact battery with specific front surface structure and battery assembly thereof

Abstract

The invention belongs to the technical field of back contact cells, and particularly relates to a back contact cell with a specific front surface structure and a cell assembly thereof, and the specific front surface structure comprises a tunneling oxide layer and a specific doped amorphous silicon layer which are sequentially arranged on the front surface of a silicon substrate, a low-doped amorphous silicon layer, a high-doped amorphous silicon layer and an oxygen-doped amorphous silicon layer are sequentially arranged in the specific doped amorphous silicon layer along the direction far away from the tunneling oxide layer, and the specific doped amorphous silicon layer is doped with a P element and contains an H element; the P doping concentration C1 of the low-doping amorphous silicon layer and the P doping concentration C3 of the oxygen-doping amorphous silicon layer are respectively smaller than the P doping concentration C2 of the high-doping amorphous silicon layer, and the specific front structure enables the back contact cell to absorb incident light within 400 nm, and the highest absorptivity exceeds 85%. The back contact battery disclosed by the invention can still keep good performance after being exposed to ultraviolet rays for a long time, the UV reliability of the battery is improved, meanwhile, high light transmittance is realized, and relatively high battery efficiency is also realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of back contact cells, and particularly relates to a back contact cell with a specific front structure and a cell assembly thereof. BACKGROUND

[0002] In the field of solar cells, back contact cells are valued for their high photoelectric conversion efficiency and good UV reliability. With the increasing demand for solar cell performance, how to design a cell front structure that can both maintain high photoelectric conversion efficiency and improve UV reliability has become a key technical challenge in this field. In the prior art, the front structure of the back contact cell often cannot meet both requirements, resulting in limited cell performance.

[0003] Currently, in order to improve the photoelectric conversion efficiency and UV reliability of the back contact cell, the main measures include optimizing the texture design of the cell front, adjusting the passivation layer material, and changing the configuration of the high light absorption layer. For example, by designing a specific surface texture, light scattering and absorption can be increased, and photoelectric conversion efficiency can be improved; by selecting a specific passivation layer material, the UV reliability of the cell can be improved; by configuring a high light absorption layer to block light of a specific wavelength, light loss can be reduced. However, these measures often require a compromise between photoelectric conversion efficiency and UV reliability. For example, CN105679843B discloses a front structure of a back contact cell, which includes a textured surface on the front of a solar cell

[300] ; a passivation layer

[312] formed on the textured surface on the front; a high light absorption layer

[313] formed on the passivation layer

[312] , the high light absorption layer

[313] is configured to block at least 10% of incident light with a wavelength of 400 nm or less. This structure is believed to improve the UV reliability of the cell, but since more than 10% of the light is blocked, the photoelectric conversion efficiency is reduced. Therefore, there is an urgent need in the art to solve the problem of how to improve the photoelectric conversion efficiency while improving the UV reliability.

[0004] It should be noted that this part of the present application only provides background technology related to the present application, and does not necessarily constitute prior art or common knowledge. SUMMARY

[0005] The purpose of the present application is to overcome the defect that the structure of the back contact cell in the prior art cannot improve the photoelectric conversion efficiency and the UV reliability at the same time, and to provide a back contact cell with a specific front structure and a cell assembly thereof. The back contact cell of the present application can maintain good performance when exposed to ultraviolet light for a long time, improve the UV reliability of the cell, and at the same time realize high light transmittance, while also taking into account the high efficiency of the cell.

[0006] To achieve the above object, in a first aspect, the present application provides a back contact cell with a specific front structure, the back contact cell comprising a silicon substrate, the specific front structure comprising, in sequence from the front of the silicon substrate, a tunneling oxide layer, a specific doped amorphous silicon layer, and an optional anti-reflection layer, and the specific doped amorphous silicon layer comprises, in sequence from the tunneling oxide layer, a low-doped amorphous silicon layer, a high-doped amorphous silicon layer, and an oxygen-doped amorphous silicon layer, the specific doped amorphous silicon layer is doped with P element and contains H element, and the P doping concentration C1 of the low-doped amorphous silicon layer and the P doping concentration C3 of the oxygen-doped amorphous silicon layer are each less than the P doping concentration C2 of the high-doped amorphous silicon layer, and the specific front structure makes the highest absorption rate of the back contact cell for incident light within 400 nm exceed 85%.

[0007] In some preferred embodiments of the present application, the thickness of the low-doped amorphous silicon layer, the high-doped amorphous silicon layer, and the oxygen-doped amorphous silicon layer in the specific doped amorphous silicon layer is independently 1-5 nm, and / or the thickness of the low-doped amorphous silicon layer is less than the thickness of the high-doped amorphous silicon layer or the oxygen-doped amorphous silicon layer.

[0008] In some preferred embodiments of the present application, C1 and C3 are each independently 0-2e19cm -3 , and C2 is greater than 2e18cm -3 .

[0009] Preferably in the present application, the content of H element in the specific doped amorphous silicon layer is independently 2-40at% in atomic percentage, and / or the content of O element in the oxygen-doped amorphous silicon layer is 5-80at% in atomic percentage.

[0010] Preferably in the present application, the content of H element in the low-doped amorphous silicon layer, the high-doped amorphous silicon layer, and the oxygen-doped amorphous silicon layer is arranged in a gradient increasing manner.

[0011] Preferably in the present application, the total thickness of the specific doped amorphous silicon layer is 3-15nm.

[0012] In some preferred embodiments of the present application, the specific front structure of the back contact cell further has at least one of the following characteristics:

[0013] Characteristic one: C1 and C3 are each independently 2e18cm -3 -2e19cm -3 .

[0014] Characteristic two: the ratio of the thickness of the specific doped amorphous silicon layer to the thickness of the tunneling oxide layer is (2-20):1.

[0015] Characteristic three: the thickness of the tunneling oxide layer is 0.2-5nm.

[0016] Feature four, the anti-reflective layer comprises at least one of silicon nitride, silicon oxynitride and silicon oxide layer.

[0017] Feature five, the thickness of the anti-reflective layer is 50-250nm.

[0018] In some preferred embodiments of the present application, the back contact cell further comprises first semiconductor layers and second semiconductor layers arranged alternately on the back surface of the silicon substrate.

[0019] In some preferred embodiments of the present application, the back surface of the back contact cell further comprises at least one of the following structures:

[0020] Structure one, the first semiconductor layer comprises a first passivation layer and a first doped silicon layer arranged in sequence on the back surface, and the second semiconductor layer comprises a second passivation layer and a second doped silicon layer arranged in sequence on the back surface, the first passivation layer and the second passivation layer are independently a tunneling oxide layer or an intrinsic silicon layer; the first doped silicon layer and the second doped silicon layer are independently polycrystalline silicon, amorphous silicon or microcrystalline silicon;

[0021] Structure two, the second semiconductor layer extends outward at both ends to cover part of the back surface of the adjacent first semiconductor layer, and a first semiconductor opening area not covered by the second semiconductor layer is formed on the back surface of the first semiconductor layer, a second semiconductor opening area is formed between the adjacent first semiconductor layers, and the second semiconductor opening area and the first semiconductor opening area are arranged in a spaced manner, and the area between them is a spacing area; in the spacing area, a mask layer is arranged or not arranged between the first semiconductor layer and the second semiconductor layer;

[0022] Structure three, the back contact cell further comprises a metal electrode and a conductive film layer arranged on the outer surface of the first semiconductor layer and the second semiconductor layer, and an isolation groove is formed on the conductive film layer to isolate the first semiconductor layer and the second semiconductor layer; the metal electrode is arranged on the outer surface of the conductive film layer corresponding to the respective semiconductor area of the first semiconductor layer and the second semiconductor layer.

[0023] In the second aspect, the present application provides a battery assembly comprising the back contact cell with the specific front surface structure of the first aspect.

[0024] Advantages:

[0025] The application has the highest absorption rate of more than 90% for the incident light within 400 nm of the back contact cell of the overall front structure of the tunneling oxide layer as the passivation layer material, the specific doped amorphous silicon layer with specific doped H element and P element, and the optional anti-reflection layer, so that the back contact cell can still maintain good performance under long-term exposure to ultraviolet light, improve the UV reliability of the cell, and at the same time realize high light transmittance, while taking into account improving the cell efficiency. Among them, the principle of simultaneously realizing high light transmittance and UV stability is as follows: in the specific doped amorphous silicon layer, H and P co-doping can optimize the optical properties of amorphous silicon to improve light transmittance, because P doping can slightly widen the band gap of amorphous silicon, reducing the absorption of visible light; H atoms can combine with dangling bonds in amorphous silicon, eliminating defect energy levels and avoiding additional absorption of light by defects, allowing more light to penetrate to the silicon substrate; at the same time, H doping can also ensure UV stability through "dynamic passivation", because UV irradiation can generate new defects in amorphous silicon, and the diffusible H atoms can quickly diffuse and combine with new defects, achieving a "damage-repair" dynamic balance, preventing defect accumulation and avoiding continuous degradation of cell performance caused by UV light; at the same time, setting the oxygen-doped amorphous silicon layer outside the high-doped amorphous silicon layer can reduce the reflectivity and absorption of the cell front to sunlight, which is more conducive to improving the short-circuit current of the cell and thus improving the cell efficiency.

[0026] Moreover, the application also cooperates with the use of the doping concentration gradient of the specific doped amorphous silicon layer (i.e., the P doping concentration C1 of the low-doped amorphous silicon layer and the P doping concentration C3 of the oxygen-doped amorphous silicon layer are less than the P doping concentration C2 of the high-doped amorphous silicon layer), which can accurately match the damage difference of the inner and outer layers of the back contact cell caused by UV, effectively reducing UV decay; at the same time, the built-in electric field formed by the P concentration gradient can also guide the directional migration of H atoms to the surface, making passivation more accurate, ultimately improving UV stability, while taking into account higher cell efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments, and it should be understood that the following drawings only show some embodiments of the application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0028] Figure 1 A structural schematic diagram in one specific embodiment of the present application.

[0029] Figure 2 A graph of external quantum efficiency (EQE) curves of two battery pieces obtained from Example 1 collected in the present application.

[0030] Legend of reference signs

[0031] Silicon substrate 1, tunneling oxide layer 2, specifically doped amorphous silicon layer 3, anti-reflection layer 4, first tunneling oxide layer 5, first doped polysilicon layer 6, second intrinsic amorphous silicon layer 7, second doped amorphous silicon layer 8, conductive film layer 9, metal electrode 10. DETAILED DESCRIPTION

[0032] In the present application, the terms "first", "second", "third", etc. are used only for descriptive purposes and are not to be construed as indicating or implying relative importance or an indicated number of technical features. Thus, features defined with "first", "second", etc. can include one or more of the features explicitly or implicitly. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified and limited.

[0033] In the present application, unless otherwise explicitly specified and limited, a first feature is "on" or "under" a second feature can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature can be "above", "over" and "on top of" the second feature can be that the first feature is directly above or obliquely above the second feature, or only means that the first feature is higher in horizontal height than the second feature. The first feature can be "below", "under" and "underneath" the second feature can be that the first feature is directly below or obliquely below the second feature, or only means that the first feature is lower in horizontal height than the second feature.

[0034] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The ranges and values should be construed to be approximations that can vary by a small amount. For numerical ranges, the end points of each range are included in the range. The ranges and values are also inclusive of any values that fall within the range. The terms "optional", "optionally" mean that the subsequently described feature or structure can or can not be present, or can be present one or more times.

[0035] In the present application, the term "inner" means close to the silicon substrate, and the term "outer" means far from the silicon substrate.

[0036] In the present application, the highest absorption rate of the back contact battery for incident light within 400 nm is tested by the national standard GB / T 6495.8.

[0037] In a first aspect, the present application provides a back contact cell with a specific front structure, the back contact cell comprising a silicon substrate, the specific front structure comprising, in sequence from the front of the silicon substrate, a tunneling oxide layer, a specific doped amorphous silicon layer, and an optional anti-reflection layer, and the specific doped amorphous silicon layer comprising, in sequence from the tunneling oxide layer, a low-doped amorphous silicon layer, a high-doped amorphous silicon layer, and an oxygen-doped amorphous silicon layer, the specific front structure allowing the back contact cell to have a highest absorption rate of more than 85%, further preferably more than 90%, and preferably more than 92%, for incident light within 400 nm. The high-doped amorphous silicon layer refers to a lower doping concentration than the low-doped amorphous silicon layer.

[0038] Preferably, the specific doped amorphous silicon layer is doped with P element and contains H element, and the P doping concentration C1 of the low-doped amorphous silicon layer and the P doping concentration C3 of the oxygen-doped amorphous silicon layer are each less than the P doping concentration C2 of the high-doped amorphous silicon layer.

[0039] The anti-reflection layer of the present application can be provided or not provided, as long as the back contact cell has a highest absorption rate of more than 85% for incident light within 400 nm. Preferably, the anti-reflection layer is provided.

[0040] In some preferred embodiments of the present application, the thickness of the low-doped amorphous silicon layer, the high-doped amorphous silicon layer, and the oxygen-doped amorphous silicon layer is independently 1-5 nm, and each can be, for example, 1 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, or 5 nm, and a range between any two point values. The present application adopts the specific doped amorphous silicon layer structure with the appropriate thickness, which is more conducive to effectively reducing UV decay and improving UV reliability while ensuring higher cell efficiency.

[0041] More preferably, the thickness of the low-doped amorphous silicon layer is less than the thickness of the high-doped amorphous silicon layer or the oxygen-doped amorphous silicon layer, which is more conducive to further effectively reducing UV decay and improving UV reliability.

[0042] In some preferred embodiments of the present application, C1 and C3 are each independently 0-2e19cm -3 , preferably 2e18cm -3 -2e19cm -3 .

[0043] Preferably, C2 is greater than 2e18cm -3 .

[0044] In some preferred embodiments of the present application, the content of H element in the specific doped amorphous silicon layer is 2-40 at%, for example, specifically 2 at%, 3 at%, 5 at%, 7 at%, 10 at%, 11 at%, 12 at%, 13 at%, 14 at%, 15 at%, 16 at%, 17 at%, 18 at%, 19 at%, 20 at%, 21 at%, 22 at%, 23 at%, 24 at%, 25 at%, 26 at%, 27 at%, 28 at%, 29 at%, 30 at%, 32 at%, 34 at%, 35 at%, 36 at%, 38 at%, 39 at% or 40 at%, and the range between any two point values.

[0045] In the present application, the content of H element in the low-doped amorphous silicon layer, the high-doped amorphous silicon layer and the oxygen-doped amorphous silicon layer is preferably gradiently increased, for example, the content of H element in the low-doped amorphous silicon layer or the high-doped amorphous silicon layer is less than that in the oxygen-doped amorphous silicon layer, and the content of H element in the low-doped amorphous silicon layer is less than that in the high-doped amorphous silicon layer, and the content of H element in the high-doped amorphous silicon layer is less than that in the oxygen-doped amorphous silicon layer. The appropriate content of H element in the specific doped amorphous silicon layer is preferably gradiently increased, which is more conducive to improving the passivation effect of the battery and the UV reliability.

[0046] In the present application, the content of O element in the oxygen-doped amorphous silicon layer is 5-80 at%, for example, specifically 5 at%, 7 at%, 10 at%, 11 at%, 12 at%, 13 at%, 14 at%, 15 at%, 16 at%, 17 at%, 18 at%, 19 at%, 20 at%, 21 at%, 22 at%, 23 at%, 24 at%, 25 at%, 26 at%, 27 at%, 28 at%, 29 at%, 30 at%, 32 at%, 34 at%, 35 at%, 36 at%, 38 at%, 39 at%, 40 at%, 42 at%, 45 at%, 47 at%, 50 at%, 52 at%, 55 at%, 57 at%, 60 at%, 63 at%, 65 at%, 68 at%, 70 at%, 72 at%, 75 at%, 78 at% or 80 at%, and the range between any two point values. The oxygen-doped amorphous silicon layer with the appropriate content of oxygen doping in the specific doped amorphous silicon layer is more conducive to improving the transmittance and the battery efficiency.

[0047] The content of H element and the doping concentration of P element in the specific doped amorphous silicon layer in the present application can be realized by controlling the flow of the corresponding doping gas source in the prior art, which is the prior art and will not be described here.

[0048] In some preferred embodiments of the present application, the total thickness of the specific doped amorphous silicon layer is 3-15 nm, for example specifically 3 nm, 3.5 nm, 4 nm, 4.5 nm, 5 nm, 5.5 nm, 6 nm, 6.5 nm, 7 nm, 7.5 nm, 8 nm, 8.5 nm, 9 nm, 9.5 nm, 10 nm, 10.5 nm, 11 nm, 11.5 nm, 12 nm, 12.5 nm, 13 nm, 13.5 nm, 14 nm, 14.5 nm, or 15 nm, and a range between any two point values. The present application adopts this preferred scheme, which is more conducive to effectively reducing UV decay while ensuring high battery efficiency and improving UV reliability.

[0049] In some preferred embodiments of the present application, the ratio of the thickness of the specific doped amorphous silicon layer to the tunneling oxide layer is (2-20):1, for example specifically 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, or 20:1, and a range between any two point values. The present application adopts this preferred scheme, which is more conducive to effectively reducing UV decay while ensuring high battery efficiency and improving UV reliability.

[0050] In some preferred embodiments of the present application, the thickness of the tunneling oxide layer is 0.2-2 nm.

[0051] In some preferred embodiments of the present application, the anti-reflection layer comprises at least one of silicon nitride, silicon oxynitride, and silicon oxide layer.

[0052] In some preferred embodiments of the present application, the thickness of the anti-reflection layer is 50-250 nm.

[0053] In some preferred embodiments of the present application, the back contact battery further comprises first semiconductor layers and second semiconductor layers alternately arranged on the back surface of the silicon substrate. The first semiconductor layers and the second semiconductor layers can be film layers deposited outside the silicon substrate, or can be doped regions obtained by doping different regions of the silicon substrate. The first semiconductor layers and the second semiconductor layers can overlap or not overlap. One of the first semiconductor layers and the second semiconductor layers is N-type, and the other is P-type.

[0054] In some preferred embodiments of the present application, the first semiconductor layers comprise first passivation layers and first doped silicon layers arranged in sequence on the back surface, and the second semiconductor layers comprise second passivation layers and second doped silicon layers arranged in sequence on the back surface. Further preferably, the first passivation layers and the second passivation layers are independently tunneling oxide layers or intrinsic silicon layers; the first doped silicon layers and the second doped silicon layers are independently polysilicon, amorphous silicon, or microcrystalline silicon. The intrinsic silicon layer is preferably intrinsic amorphous silicon.

[0055] In a specific preferred embodiment, the first semiconductor layer comprises a first first tunneling oxide layer and a first doped polysilicon layer arranged in sequence from back to front, and the second semiconductor layer comprises a second intrinsic silicon layer and a second doped silicon layer arranged in sequence from back to front. The second doped silicon layer is doped amorphous silicon or microcrystalline silicon. The present application adopts a combined passivation structure, which is more conducive to improving UV reliability while improving cell efficiency. Further, the thicknesses and corresponding doping concentrations of the first tunneling oxide layer, the second intrinsic silicon layer, the first doped polysilicon layer and the second doped silicon layer can be within the ranges of the prior art, and can all be used in the present application. For example, the thickness of the first tunneling oxide layer is independently 1-2 nm, the thickness of the first doped polysilicon layer is 70-120 nm, the effective doping concentration is greater than 5e18cm -3 -9e19cm -3 -9e19cm -3 .

[0056] In some preferred embodiments of the present application, the second semiconductor layer extends outward at both ends to cover part of the back surface of the adjacent first semiconductor layer, and a first semiconductor opening area is formed on the back surface of the first semiconductor layer without covering the second semiconductor layer, and a second semiconductor opening area is formed between the adjacent first semiconductor layers, and the second semiconductor opening area and the first semiconductor opening area are arranged in a spaced manner and the area between them is a spacing area. Further preferably, in the spacing area, a mask layer is arranged between the first semiconductor layer and the second semiconductor layer or no mask layer is arranged.

[0057] The back contact cell of the present application also includes other conventional structures. In some preferred embodiments of the present application, the back contact cell further comprises a metal electrode and a conductive film layer laid on the outer surface of the first semiconductor layer and the second semiconductor layer, and an isolation groove is formed on the conductive film layer to isolate the first semiconductor layer and the second semiconductor layer; the metal electrode is arranged on the outer surface of the respective semiconductor area of the first semiconductor layer and the second semiconductor layer corresponding to the conductive film layer.

[0058] The front surface and the back surface of the silicon substrate of the present application can each independently be a textured surface or a polished surface, as long as it is conducive to improving UV reliability and cell efficiency.

[0059] In a second aspect, the present application provides a battery assembly comprising the back contact cell with a specific front surface structure of the first aspect.

[0060] The following detailed description of the embodiments of the present application is exemplary and is intended only to explain the present application, and cannot be understood as a limitation of the present application.

[0061] Example 1

[0062] A back-contact battery with a specific front structure, such as Figure 1 As shown, the back contact battery includes a silicon substrate 1, and a first semiconductor layer and a second semiconductor layer alternately disposed on the back side of the silicon substrate 1. The specific front structure includes a tunneling oxide layer 2 (tunneling silicon oxide) with a thickness of 1 nm, a specifically doped amorphous silicon layer 3 with a total thickness of 5 nm, and an antireflection layer 4 with a thickness of 100 nm (specifically, a stack of silicon nitride with a thickness of 60 nm, silicon oxynitride with a thickness of 25 nm, and silicon oxide with a thickness of 15 nm, disposed sequentially on the front side of the silicon substrate 1. The specifically doped amorphous silicon layer 3 is a stack of a low-doped amorphous silicon layer (thickness of 1.5 nm), a high-doped amorphous silicon layer (thickness of 1.5 nm), and an oxygen-doped amorphous silicon layer (thickness of 2 nm, oxygen content of 50 at%) disposed sequentially along the direction away from the tunneling oxide layer 2. The specifically doped amorphous silicon layer 3 is doped with H and P elements, and the P doping concentration C1 of the low-doped amorphous silicon layer and the P doping concentration C3 of the oxygen-doped amorphous silicon layer are respectively less than the P doping concentration C2 of the high-doped amorphous silicon layer. C1 is 2e18cm. -3 C2 is 2e19cm -3 C3 is 2e18cm -3 The H content in the low-doped amorphous silicon layer, the high-doped amorphous silicon layer, and the oxygen-doped amorphous silicon layer is 10at%, 15at%, and 20at, respectively. The calculated thickness ratio of the specifically doped amorphous silicon layer 3 to the tunneling oxide layer 2 is 5:1. This specific front-side structure results in a maximum absorption rate of 92% for incident light within 400nm of the back-contact battery.

[0063] The first semiconductor layer includes a first tunneling oxide layer 5 with a thickness of 1.5 nm and an N-type first doped polysilicon layer 6 (with a thickness of 100 nm and a phosphorus doping concentration of 5e19cm) sequentially disposed on the back side. -3 The second semiconductor layer includes a second intrinsic amorphous silicon layer 7 with a thickness of 10 nm and a second doped amorphous silicon layer 8 of P-type (with a thickness of 15 nm and a boron doping concentration of 2e19cm) sequentially disposed on the back side. -3). Two ends of the second semiconductor layer respectively extend outward to cover part of the back surface of the adjacent first semiconductor layer, and a first semiconductor opening area not covered by the second semiconductor layer is formed on the back surface of the first semiconductor layer, a second semiconductor opening area is formed between the adjacent first semiconductor layers, and the second semiconductor opening area is arranged in a spaced manner with the first semiconductor opening area, and the area between them is a spacing area. The back contact cell further comprises a metal electrode 10 and a conductive film layer 9 (ITO) laid on the outer surface of the first semiconductor layer and the second semiconductor layer, and a separation groove is formed on the conductive film layer 9 to separate the first semiconductor layer and the second semiconductor layer; the metal electrode 10 is arranged on the outer surface of the conductive film layer 9 corresponding to the respective semiconductor area of the first semiconductor layer and the second semiconductor layer.

[0064] The two battery pieces obtained in Example 1 were subjected to external quantum efficiency (EQE) test, and the test curve is shown in Figure 2 From Figure 2 , it can be seen that the effective absorption of the battery in the wavelength range of 300-400 nm is between 80% and 92%, which greatly improves the absorption and utilization rate of the battery to ultraviolet light.

[0065] Example 2

[0066] Refer to Example 1, the difference is that the P doping concentration C1 of the low-doped amorphous silicon layer is adjusted to 6e18cm -3 .

[0067] Example 3

[0068] Refer to Example 1, the difference is that the P doping concentration C2 of the high-doped amorphous silicon layer is adjusted to 5e19cm -3 .

[0069] Example 4

[0070] Refer to Example 1, the difference is that the P doping concentration C3 of the oxygen-doped amorphous silicon layer is adjusted to 5e18cm -3 .

[0071] Example 5

[0072] Refer to Example 1, the difference is that the thickness of the high-doped amorphous silicon layer is adjusted to 3nm, and the total thickness of the specific-doped amorphous silicon layer 3 is calculated to be 6.5nm, and the thickness ratio of the specific-doped amorphous silicon layer 3 to the tunneling oxide layer 2 is 6.5:1.

[0073] Example 6

[0074] Refer to Example 1, the difference is that the oxygen doping concentration of the oxygen-doped amorphous silicon layer is adjusted to 75at%.

[0075] Comparative Example 1

[0076] Reference is made to Example 1, except that no oxygen-doped amorphous silicon layer is formed in the specific doped amorphous silicon layer 3.

[0077] Comparative Example 2

[0078] Reference is made to Example 1, except that no low-doped amorphous silicon layer is formed in the specific doped amorphous silicon layer 3.

[0079] Comparative Example 3

[0080] Reference is made to Example 1, except that no high-doped amorphous silicon layer is formed in the specific doped amorphous silicon layer 3.

[0081] Comparative Example 4

[0082] Reference is made to Example 1, except that the oxygen-doped amorphous silicon layer in the specific doped amorphous silicon layer 3 is replaced by a non-oxygen-doped amorphous silicon, i.e. only no oxygen doping, other conditions such as hydrogen doping and P doping remain unchanged.

[0083] Test Example

[0084] The back contact cells obtained in the above examples and comparative examples are tested for performance, and the results are shown in Table 1. Among them, the highest absorption rate of the back contact cell in the application under the incident light of 400 nm is obtained by testing according to the national standard “GB / T 6495.8-2002 Photovoltaic devices Part 8: Measurement of spectral response of photovoltaic devices”. The test method of UV attenuation ratio is based on the IEC61215:2021 test standard.

[0085] Table 1

[0086] Performance indicators Absorption maxima (%) for incident light at 400 nm Minority carrier lifetime (ps) Cell efficiency (%) UV attenuation ratio (%) Example 1 92 4000 27 1 Example 2 91 3600 26.9 0.9 Example 3 90 3700 26.7 0.8 Example 4 91 3800 26.8 0.85 Example 5 88 4200 26.75 0.8 Example 6 92.5 4000 26.95 1 Comparative Example 1 84 3600 26.6 1.5 Comparative Example 2 84 2800 26.5 2 Comparative Example 3 85 3000 26.7 2.5 Comparative Example 4 83 4000 26.5 1.5

[0087] From the above results, compared with the comparative examples, the back contact cell using the embodiment scheme of the application can still maintain good performance under long-term exposure to ultraviolet light, improve the UV reliability of the cell, and at the same time realize high light transmittance, while maintaining high cell efficiency.

[0088] Further, according to Examples 1 and 2-6, using the preferred scheme of the application, the UV reliability of the cell is more improved, while maintaining high cell efficiency.

[0089] The above describes the preferred embodiments of the application, but the application is not limited thereto. Within the technical concept of the application, various simple modifications can be made to the technical scheme of the application, including combining various technical features in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the application and fall within the protection scope of the application.

Claims

1. A back-contact battery having a specific front-side structure, the back-contact battery comprising a silicon substrate, characterized in that, This specific front-side structure includes a tunneling oxide layer, a specifically doped amorphous silicon layer, and an antireflection layer (with or without) sequentially disposed on the front side of a silicon substrate. The specifically doped amorphous silicon layer contains a low-doped amorphous silicon layer, a high-doped amorphous silicon layer, and an oxygen-doped amorphous silicon layer sequentially disposed in the direction away from the tunneling oxide layer. The specifically doped amorphous silicon layer is doped with P and contains H. The P doping concentration C1 of the low-doped amorphous silicon layer and the P doping concentration C3 of the oxygen-doped amorphous silicon layer are respectively less than the P doping concentration C2 of the high-doped amorphous silicon layer. This specific front-side structure enables the back-contact battery to achieve an absorption rate of over 85% for incident light within 400 nm.

2. The back contact battery with a specific front structure according to claim 1, characterized in that, The thicknesses of the low-doped amorphous silicon layer, the high-doped amorphous silicon layer, and the oxygen-doped amorphous silicon layer are each independently 1-5 nm, and / or the thickness of the low-doped amorphous silicon layer is less than the thickness of the high-doped amorphous silicon layer or the oxygen-doped amorphous silicon layer.

3. The back contact battery with a specific front-side structure according to claim 1 or 2, characterized in that, C1 and C3 are each independently 0-2e19cm -3 C2 is greater than 2e18cm -3 .

4. The back contact battery with a specific front structure according to claim 1, characterized in that, The H element content in the specific doped amorphous silicon layer is 2-40 at% on an atomic percentage basis, and / or the O element content in the oxygen-doped amorphous silicon layer is 5-80 at% on an atomic percentage basis.

5. The back contact battery with a specific front-side structure according to claim 1 or 4, characterized in that, The H element content in the low-doped amorphous silicon layer, the high-doped amorphous silicon layer, and the oxygen-doped amorphous silicon layer is set in a gradient increasing manner.

6. The back contact battery with a specific front-side structure according to claim 1 or 2, characterized in that, The total thickness of the specifically doped amorphous silicon layer is 3-15 nm.

7. The back contact battery with a specific front structure according to claim 1, characterized in that, The specific front structure of the back contact battery also has at least one of the following characteristics: Feature 1: C1 and C3 are each independently 2e18cm -3 -2e19cm -3 ; Feature 2: The thickness ratio of the specifically doped amorphous silicon layer to the tunneling oxide layer is (2-20):1; Feature 3: The thickness of the tunneling oxide layer is 0.2-2 nm; Feature 4: The antireflection layer includes at least one of silicon nitride, silicon oxynitride, and silicon oxide layers; Feature 5: The thickness of the antireflection layer is 50-250nm.

8. The back contact battery with a specific front structure according to claim 1, characterized in that, The back contact battery also includes a first semiconductor layer and a second semiconductor layer alternately disposed on the back side of a silicon substrate.

9. The back contact battery with a specific front structure according to claim 8, characterized in that, The back side of the back contact battery also includes at least one of the following structures: Structure 1: The first semiconductor layer includes a first passivation layer and a first doped silicon layer sequentially disposed on the back side; the second semiconductor layer includes a second passivation layer and a second doped silicon layer sequentially disposed on the back side; the first passivation layer and the second passivation layer are each independently a tunneling oxide layer or an intrinsic silicon layer; the first doped silicon layer and the second doped silicon layer are each independently polycrystalline silicon, amorphous silicon, or microcrystalline silicon. Structure 2: The two ends of the second semiconductor layer extend outward to cover the back side of the adjacent first semiconductor layer, and a first semiconductor opening region that does not cover the second semiconductor layer is opened on the back side of the first semiconductor layer. A second semiconductor opening region is formed between adjacent first semiconductor layers. The second semiconductor opening regions and the first semiconductor opening regions are arranged alternately, and the area between them is a gap region. In the gap region, a mask layer is provided between the first semiconductor layer and the second semiconductor layer or no mask layer is provided. Structure 3: The back contact battery also includes a metal electrode and a conductive film layer laid on the outer surface of the first semiconductor layer and the second semiconductor layer. An isolation groove is formed on the conductive film layer to isolate the first semiconductor layer and the second semiconductor layer. The metal electrode is disposed on the outer surface of the conductive film layer corresponding to the semiconductor region of the first semiconductor layer and the second semiconductor layer.

10. A battery assembly, characterized in that, It includes a back-contact battery having a specific front-side structure as described in any one of claims 1-9.

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