Multi-junction solar cell structure
By covering the first sublayer containing In with a GaAs or GaAsSb layer on the surface of the epitaxial structure of a multi-junction solar cell, the problem of reaction chamber contamination caused by In atom volatilization is solved, thereby improving the cell's fabrication yield and performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-27
- Publication Date
- 2026-04-03
AI Technical Summary
In the epitaxial fabrication process of existing inverted (Al)GaInP/GaAs/InGaAs triple-junction solar cells, the InGaAs subcell has a high In content, which causes In atoms to volatilize and remain in the reaction chamber, affecting cell performance and fabrication yield.
In the surface layer of the battery epitaxial structure, a GaAs or GaAsSb layer is covered on the first sublayer containing In as the second sublayer to form an ohmic contact layer, which reduces the volatilization of In atoms and reduces contamination of the reaction chamber.
It improves the fabrication yield of multijunction solar cells, reduces the number of resident In atoms in the reaction chamber, improves cell performance and stability, and enhances ohmic contact effect.
Smart Images
Figure CN224083972U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of solar cell technology, and more particularly to a solar cell structure. Background Technology
[0002] Solar cells can directly convert solar energy into electrical energy, making them an effective form of clean energy. III-V compound semiconductor solar cells currently boast the highest conversion efficiency among all material systems, while also possessing advantages such as good high-temperature resistance and strong radiation resistance, and are widely recognized as a new generation of high-performance, long-life space power sources. Currently, the most researched gallium arsenide-based triple-junction solar cells employ a lattice-matched GaInP / InGaAs / Ge structure and have been widely used in the aerospace field. However, the bandgap combination of GaInP / InGaAs / Ge triple-junction solar cells deviates from the optimal conditions of the solar spectrum, making it difficult to further significantly improve their photoelectric conversion efficiency.
[0003] In recent years, research has gradually shifted towards bandgap-matched (Al)GaInP / GaAs / InGaAs triple-junction solar cells, whose theoretical efficiency can reach 50% under high-concentration conditions. (Al)GaInP / GaAs / InGaAs triple-junction solar cells typically employ an inverted growth structure. Specifically, after forming stacked (Al)GaInP, GaAs, and InGaAs sub-cells on a GaAs substrate, the epitaxial wafer is bonded to a flexible PI substrate or electroplated Cu substrate, then flipped over and the GaAs substrate is peeled off. This process fabricates a flexible thin-film solar cell with a high power-to-weight ratio. The peeled GaAs substrate can be reused after processing, significantly reducing the manufacturing cost of the cell.
[0004] However, in the epitaxial fabrication process of existing inverted (Al)GaInP / GaAs / InGaAs triple-junction solar cells, the InGaAs sub-cells near the surface of the epitaxial structure use InGaAs materials with a high In content, and the surface of the epitaxial structure is usually an In-containing ohmic contact layer. Thus, after the growth of the In-containing ohmic contact layer, the In atoms in the In-containing ohmic contact layer are easily volatilized and remain in the reaction chamber. When a new epitaxial structure is fabricated in the reaction chamber, the In atoms residing in the reaction chamber will nucleate in the new epitaxial structure and form defects, affecting the performance of the cell. Utility Model Content
[0005] To address the aforementioned technical problems, this application provides a multi-junction solar cell structure to reduce or avoid the volatilization of In atoms from the In-containing ohmic contact layer located on the surface of the cell's epitaxial structure into the reaction chamber, thereby reducing the number of resident In atoms in the reaction chamber, i.e., reducing the contamination and impact of resident In atoms on the reaction chamber, and improving the fabrication yield of the multi-junction solar cell structure.
[0006] To achieve the above objectives, the embodiments of this application provide the following technical solutions:
[0007] A multi-junction solar cell structure, comprising:
[0008] First substrate;
[0009] Located on one side of the first substrate, a first ohmic contact layer, a plurality of sub-cells, and a second ohmic contact layer are stacked in a direction away from the first substrate;
[0010] The second ohmic contact layer includes a first sublayer and a second sublayer stacked in a direction away from the first substrate. The first sublayer is an In-containing material layer, and the second sublayer is a GaAs layer or a GaAsSb layer.
[0011] Optionally, the first sub-layer is an InGaAs layer.
[0012] Optionally, the first sub-layer is an AlInGaAs layer.
[0013] Optionally, the Al component x of the first sublayer satisfies: 0 < x ≤ 0.2.
[0014] Optionally, the thickness of the second sublayer ranges from 10nm to 100nm, including the endpoint values.
[0015] Optionally, the thickness of the first sublayer can range from 100nm to 500nm, including the endpoint values.
[0016] Optionally, the plurality of sub-cells includes a first sub-cell, a second sub-cell, and a third sub-cell stacked in a direction away from the first substrate, wherein a first tunnel junction is disposed between the first sub-cell and the second sub-cell, and a second tunnel junction and a deterioration buffer layer stacked in a direction away from the first substrate are disposed between the second sub-cell and the third sub-cell.
[0017] The first sub-cell is an AlGaInP sub-cell or a GaInP sub-cell, the second sub-cell is a GaAs sub-cell, and the third sub-cell is an InGaAs sub-cell.
[0018] Optionally, the altered buffer layer is an AlGaInAs layer or a GaInP layer. The altered buffer layer includes an m-layer sequence stacked along the direction from the second sub-cell to the third sub-cell, where m ≥ 3 and m is an integer. The lattice constant of each layer of the sequence is greater than the lattice constant of the second sub-cell, and the lattice constant of each layer of the sequence increases along the direction from the second sub-cell to the third sub-cell, with the lattice constant of the m-th layer being greater than the lattice constant of the third sub-cell.
[0019] Optionally, the In component y of the first sublayer satisfies: 0.2≤y≤0.4.
[0020] Optionally, a sacrificial layer, which is an AlAs layer, is further disposed between the first substrate and the first ohmic contact layer.
[0021] Compared with existing technologies, the above technical solution has the following advantages:
[0022] The multi-junction solar cell structure provided in this application includes a first substrate, a first ohmic contact layer stacked on one side of the first substrate in a direction away from the first substrate, a plurality of sub-cells, and a second ohmic contact layer. The second ohmic contact layer includes a first sub-layer and a second sub-layer stacked in a direction away from the first substrate. The first sub-layer is an In-containing material layer, and the second sub-layer is a GaAs layer or a GaAsSb layer. That is, when forming the second ohmic contact layer on the surface of the cell epitaxial structure, the In-containing first sub-layer is grown first, and then the GaAs layer or GaAsSb layer is grown as the second sub-layer. In this way, not only do the first sub-layer and the second sub-layer together constitute the ohmic contact layer to form a good ohmic contact with the metal electrode, but also, since the In-containing first sub-layer is covered with a GaAs layer or GaAsSb layer as the second sub-layer, and the second sub-layer is an In-free material layer, the volatilization of In atoms from the In-containing first sub-layer into the reaction chamber can be reduced or avoided, thereby reducing the number of In atoms residing in the reaction chamber, that is, reducing the contamination and impact of the residing In atoms on the reaction chamber, and improving the fabrication yield of the multi-junction solar cell structure. Furthermore, in the second ohmic contact layer, the second sublayer is closer to the metal electrode than the first sublayer, and the second sublayer is made of GaAs or GaAsSb, which can form a good ohmic contact with the metal electrode.
[0023] Other objects and advantages of this application will be described in detail in conjunction with the accompanying drawings in the following embodiments. Attached Figure Description
[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0025] Figure 1 This is a cross-sectional schematic diagram of a multi-junction solar cell structure provided in an embodiment of this application;
[0026] Figure 2 To be Figure 1 The diagram shows the intermediate structure of a multi-junction solar cell as it transitions from the first substrate to the second substrate.
[0027] Figure 3 To be Figure 1 The diagram shows the structure of a multi-junction solar cell after the first substrate is transferred to the second substrate and the first substrate is removed.
[0028] Figure 4 for Figure 1 The diagram shows a detailed cross-sectional view of the multi-junction solar cell structure.
[0029] Figure label:
[0030] First substrate - 100; Second substrate - 110; First ohmic contact layer - 200; Multiple sub-cells 300; First sub-cell - 310; Second sub-cell - 320; Third sub-cell - 330; First tunnel junction - 340; Second tunnel junction - 350; Modified buffer layer - 360; Second ohmic contact layer - 400; First sublayer - 410; Second sublayer - 420; Sacrificial layer - 500; First window layer - 311; First emitter region - 312; First base region - 313; First back field layer - 314; Second window layer - 321; Second emitter region - 322; Second base region - 323; Second back field layer - 324; Third window layer - 331; Third emitter region - 332; Third base region - 333; Third back field layer - 334. Detailed Implementation
[0031] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0032] The terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms are interchangeable where appropriate; this is merely a way of distinguishing objects with the same attributes in the embodiments of this application. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, so that a process, method, system, product, or apparatus that comprises a series of elements is not necessarily limited to those elements, but may include other elements not explicitly listed or inherent to those processes, methods, products, or apparatuses.
[0033] Secondly, this application provides a detailed description in conjunction with schematic diagrams. When detailing the embodiments of this application, for ease of explanation, the accompanying drawings illustrating the device structure may be partially enlarged, not to scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of this application. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.
[0034] As described in the background section, in the epitaxial structure fabrication process of existing inverted (Al)GaInP / GaAs / InGaAs triple-junction solar cells, the InGaAs sub-cells near the surface of the epitaxial structure use InGaAs materials with a high In content, and the surface of the epitaxial structure is usually an In-containing ohmic contact layer. Thus, after the growth of the In-containing ohmic contact layer, the In atoms in the In-containing ohmic contact layer are easily volatilized and remain in the reaction chamber. When a new epitaxial structure is fabricated in the reaction chamber, the In atoms residing in the reaction chamber will nucleate in the new epitaxial structure and form defects, affecting the performance of the cell.
[0035] In view of this, embodiments of this application provide a multi-junction solar cell structure. Figure 1 A cross-sectional schematic diagram of a multi-junction solar cell structure provided in an embodiment of this application is shown, as follows: Figure 1 As shown, the multi-junction solar cell structure includes a first substrate 100 and a first ohmic contact layer 200, a plurality of sub-cells 300, and a second ohmic contact layer 400 stacked on one side of the first substrate 100 in a direction away from the first substrate 100. The second ohmic contact layer 400 includes a first sub-layer 410 and a second sub-layer 420 stacked in a direction away from the first substrate 100. The first sub-layer 410 is an In-containing material layer, and the second sub-layer 420 is a GaAs layer or a GaAsSb layer.
[0036] Optionally, the first substrate 100 can be a GaAs substrate.
[0037] Optionally, the first ohmic contact layer 200 can be an n-type ohmic contact layer, for example, the first ohmic contact layer 200 can be an n-type GaAs layer, and the second ohmic contact layer 400 can be a p-type ohmic contact layer, but this application does not limit this. Alternatively, the first ohmic contact layer 200 can be a p-type ohmic contact layer, and the second ohmic contact layer 400 can be an n-type ohmic contact layer.
[0038] Understandably, the first ohmic contact layer 200 will form an ohmic contact with a metal electrode, and the second ohmic contact layer 400 will form an ohmic contact with another metal electrode, so as to conduct the current generated by the absorption of sunlight by the multiple sub-cells 300.
[0039] It should be noted that the multi-junction solar cell structure provided in the embodiments of this application can be an inverted (Al)GaInP / GaAs / InGaAs triple-junction solar cell structure. In this case, as... Figure 1 As shown, the plurality of sub-cells 300 may include a first sub-cell 310, a second sub-cell 320 and a third sub-cell 330 stacked in a direction away from the first substrate 100. A first tunnel junction 340 is disposed between the first sub-cell 310 and the second sub-cell 320. A second tunnel junction 350 and a degradation buffer layer 360 are disposed between the second sub-cell 320 and the third sub-cell 330 stacked in a direction away from the first substrate 100. The first sub-cell 310 is an AlGaInP sub-cell or a GaInP sub-cell, the second sub-cell 320 is a GaAs sub-cell, and the third sub-cell 330 is an InGaAs sub-cell.
[0040] And, at this time, such as Figure 1 As shown, a sacrificial layer 500 may be disposed between the first substrate 100 and the first ohmic contact layer 200. The sacrificial layer 500 may be an AlAs layer. That is, a sacrificial layer 500, a first ohmic contact layer 200, a first sub-cell 310, a first tunnel junction 340, a second sub-cell 320, a second tunnel junction 350, a degradation buffer layer 360, a third sub-cell 330, and a second ohmic contact layer 400 are formed on one side of the first substrate 100 in a direction away from the first substrate 100. The second ohmic contact layer 400 (especially the second sub-layer 420) is the surface layer of the cell epitaxial structure.
[0041] Furthermore, such as Figure 2 As shown, the battery epitaxial structure formed by the first ohmic contact layer 200 to the second ohmic contact layer 400 is transferred to the second substrate 110 from the second ohmic contact layer 400 side.
[0042] For example Figure 3As shown, the sacrificial layer 500 (AlAs layer) is etched using HF etching solution to remove the first substrate 100. The second substrate 110 can be a PI substrate or an electroplated Cu substrate, serving as a metal electrode to form an ohmic contact with the second ohmic contact layer 400. A metal electrode is also formed on the first ohmic contact layer 200. Figure 3 (not shown in the image), thus forming an inverted (Al)GaInP / GaAs / InGaAs triple junction solar cell structure.
[0043] However, the multi-junction solar cell structure provided in this application is not limited to the inverted (Al)GaInP / GaAs / InGaAs triple-junction solar cell structure. It can also be a forward multi-junction solar cell structure or a multi-junction solar cell structure made of other materials. As long as the surface layer of the epitaxial structure of the multi-junction solar cell structure is an In-containing material layer that makes ohmic contact during its epitaxial growth process, the In atoms in the In-containing material layer that makes ohmic contact on the surface of the epitaxial structure of the cell are easy to volatilize and reside in the reaction chamber. This results in the In atoms residing in the reaction chamber nucleating in the new cell structure and forming defects, which affects the performance of the cell.
[0044] Based on this, the multi-junction solar cell structure provided in this application, when forming a stacked first ohmic contact layer 200, multiple sub-cells 300, and a second ohmic contact layer 400 on one side of the first substrate 100 in a direction away from the first substrate 100, especially when forming the second ohmic contact layer 400 on the surface of the cell epitaxial structure, firstly grows an In-containing first sub-layer 410, and then grows a GaAs layer or a GaAsSb layer as the second sub-layer 420. In this way, not only do the first sub-layer 410 and the second sub-layer 420 together constitute the ohmic contact layer to form a good ohmic contact with the metal electrode, but also, since the In-containing first sub-layer 410 is also covered with a GaAs layer or a GaAsSb layer as the second sub-layer 420, and the second sub-layer 420 is an In-free material layer, the volatilization of In atoms from the In-containing first sub-layer 410 into the reaction chamber can be reduced or avoided, thereby reducing the number of In atoms residing in the reaction chamber, that is, reducing the pollution and impact of the residing In atoms on the reaction chamber, and improving the fabrication yield of the multi-junction solar cell structure. Furthermore, in the second ohmic contact layer 400, the second sub-layer 420 is closer to the metal electrode than the first sub-layer 410, and the second sub-layer 420 is made of GaAs or GaAsSb, which can form a good ohmic contact with the metal electrode.
[0045] Optionally, in some embodiments of this application, the first sublayer 410 of the second ohmic contact layer 400 may be an InGaAs layer.
[0046] refer to Figure 3As shown, when the multi-junction solar cell structure provided in this application embodiment is an inverted (Al)GaInP / GaAs / InGaAs triple-junction solar cell structure, if the first sub-layer 410 in the second ohmic contact layer 400 is an InGaAs layer, then the lattice matching of the first sub-layer 410 (InGaAs layer), the third sub-cell 330 (InGaAs sub-cell), and the second sub-cell 320 (GaAs sub-cell) helps to reduce defects and stress caused by lattice mismatch, thereby improving the overall performance and stability of the cell. Furthermore, the band structure of the InGaAs material makes the first sub-layer 410 suitable as a p-type ohmic contact layer, effectively forming good energy level matching with other parts of the cell, which is beneficial for carrier transport and collection, and can also improve the contact characteristics between the cell and the metal electrode, reducing contact resistance, thereby improving the current output and efficiency of the cell.
[0047] However, it is still for reference Figure 3 As shown, when the multi-junction solar cell structure provided in this application embodiment is an inverted (Al)GaInP / GaAs / InGaAs triple-junction solar cell structure, after sunlight is absorbed sequentially by the first sub-cell 310, the second sub-cell 320, and the third sub-cell 330, excess light usually reaches the second ohmic contact layer 400 and the metal electrode (i.e., the second substrate 110) that forms an ohmic contact with the second ohmic contact layer 400. The excess light can be reflected back by the light reflection effect of the metal electrode, so that each sub-cell can absorb sunlight again, thereby effectively reducing the thickness of the sub-cell and improving the performance of the solar cell. However, when the first sub-layer 410 of the second ohmic contact layer 400 is an InGaAs layer, due to the small band gap of the InGaAs material, the first sub-layer 410 may absorb some light, affecting the secondary absorption effect of the cell.
[0048] At this time, when the second sub-layer 420 of the second ohmic contact layer 400 is a GaAs layer, since the band gap of GaAs material is larger than that of InGaAs material, the second ohmic contact layer 400 is configured to include a first sub-layer 410 (InGaAs layer) and a second sub-layer 420 (GaAs layer) while keeping the thickness of the second ohmic contact layer 400 unchanged. Compared with the second ohmic contact layer 400 being entirely the first sub-layer 410 (InGaAs layer), it will absorb less light, thereby improving the secondary absorption effect of the battery.
[0049] However, when the second sub-layer 420 of the second ohmic contact layer 400 is a GaAs layer, due to the lattice mismatch between the GaAs material and the InGaAs material of the third sub-cell 330 (InGaAs sub-cell) and the InGaAs material of the first sub-layer 410 (InGaAs layer), the thickness of the second sub-layer 420 can be set to be thinner. Optionally, the thickness of the second sub-layer 420 can be in the range of 10nm-100nm, including the endpoint value, so that the second sub-layer 420 (GaAs layer) is in a strain state, avoiding the impact of lattice mismatch on device performance.
[0050] Furthermore, when the second sub-layer 420 of the second ohmic contact layer 400 is a GaAsSb layer, the GaAsSb material is lattice-matched with the InGaAs material of the third sub-cell 330 (InGaAs sub-cell) and the InGaAs material of the first sub-layer 410 (InGaAs layer). However, the band gap of the GaAsSb material is relatively smaller than that of the InGaAs material. To avoid the second sub-layer 420 absorbing more light, the thickness of the second sub-layer 420 can be set to be relatively thin. Optionally, the thickness of the second sub-layer 420 can be in the range of 10nm-100nm, including the endpoint values, so as not to increase the overall light absorption of the second ohmic contact layer 400.
[0051] Considering that the first sublayer 410 of the second ohmic contact layer 400 may absorb light when it is an InGaAs layer, which may affect the secondary absorption effect of the battery, alternatively, in some embodiments of this application, the first sublayer 410 of the second ohmic contact layer 400 may be an AlInGaAs layer. Since the band gap of AlInGaAs material is large, the absorption of light by the second ohmic contact layer 400 can be significantly reduced, thereby improving the secondary absorption effect of the battery.
[0052] However, when the first sublayer 410 of the second ohmic contact layer 400 is an AlInGaAs layer, the presence of the Al component makes it difficult for the first sublayer 410 to form a good ohmic contact with the metal electrode. In this case, the second sublayer 420 of the second ohmic contact layer 400 is a GaAs layer or a GaAsSb layer, and the second sublayer 420 is closer to the metal electrode than the first sublayer 410. Therefore, the second sublayer 420 can form a good ohmic contact with the metal electrode.
[0053] Furthermore, when the second sub-layer 420 of the second ohmic contact layer 400 is a GaAs layer, the larger band gap of the GaAs material further reduces the light absorption of the second ohmic contact layer 400, improving the secondary absorption effect of the battery. However, due to the lattice mismatch between the GaAs material and the InGaAs material of the third sub-cell 330 (InGaAs sub-cell), the thickness of the second sub-layer 420 can be set to be relatively thin. Optionally, the thickness of the second sub-layer 420 can range from 10nm to 100nm, including the endpoint values, so that the second sub-layer 420 (GaAs layer) is under strain, avoiding the impact of lattice mismatch on device performance.
[0054] When the second sublayer 420 of the second ohmic contact layer 400 is a GaAsSb layer, the GaAsSb material is lattice-matched with the InGaAs material of the third sub-cell 330 (InGaAs sub-cell). However, the band gap of the GaAsSb material is relatively small. To avoid light absorption by the second sublayer 420, the thickness of the second sublayer 420 can be set to be thin. Optionally, the thickness of the second sublayer 420 can be in the range of 10nm-100nm, including the endpoint values. Thus, because the first sublayer 410 uses an AlInGaAs layer, the light absorption by the second ohmic contact layer 400 is significantly reduced, improving the secondary absorption effect of the cell.
[0055] In summary, in the multi-junction solar cell structure provided in this application embodiment, the first sublayer 410 of the second ohmic contact layer 400 can be an InGaAs layer or an AlInGaAs layer, and the second sublayer 420 of the second ohmic contact layer 400 can be a GaAs layer or a GaAsSb layer. By utilizing the In-free second sublayer 420 to reduce or avoid the volatilization of In atoms from the In-containing first sublayer 410 into the reaction chamber, thereby reducing the number of resident In atoms in the reaction chamber, i.e., reducing the contamination and impact of resident In atoms on the reaction chamber, improving the fabrication yield of the multi-junction solar cell structure, and based on the fact that the first sublayer 410 and the second sublayer 420 together constitute an ohmic contact layer to form a good ohmic contact with the metal electrode, further:
[0056] When the first sublayer 410 is an InGaAs layer and the second sublayer 420 is a GaAs layer, the advantages are that the first sublayer 410 (InGaAs layer), the third subcell 330 (InGaAs subcell), and the second subcell 320 (GaAs subcell) are lattice-matched and energy-level-matched, which is conducive to forming a good ohmic contact. Although the first sublayer 410 (InGaAs layer) may absorb some light due to its small band gap, the second sublayer 420 (GaAs layer) absorbs very little light, which can still improve the secondary absorption effect of the cell. Although the second sublayer 420 (GaAs layer) is lattice-mismatched with the third subcell 330 (InGaAs subcell) and the first sublayer 410 (InGaAs layer), the thickness of the second sublayer 420 (GaAs layer) can be relatively thin, so that the second sublayer 420 is in a strained state, avoiding the impact of lattice mismatch on device performance.
[0057] When the first sublayer 410 is an InGaAs layer and the second sublayer 420 is a GaAsSb layer, the advantages are that not only are the first sublayer 410 (InGaAs layer), the third subcell 330 (InGaAs subcell), and the second subcell 320 (GaAs subcell) lattice and energy level matched, which is conducive to forming a good ohmic contact, but the second sublayer 420 (GaAsSb layer) is also lattice matched with the third subcell 330 (InGaAs subcell) and the first sublayer 410 (InGaAs layer). Although the second sublayer 420 (GaAsSb layer) may absorb some light due to its small band gap, the thickness of the second sublayer 420 (GaAsSb layer) can be set to be relatively thin, so that it will not increase the overall light absorption of the second ohmic contact layer 400.
[0058] When the first sublayer 410 is an AlInGaAs layer and the second sublayer 420 is a GaAs layer, the advantages are that, since the band gaps of the first sublayer 410 (AlInGaAs layer) and the second sublayer 420 (GaAs layer) are both large, the absorption of light by the second ohmic contact layer 400 can be significantly reduced, improving the secondary absorption effect of the battery. Although the first sublayer 410 (AlInGaAs layer) is not easy to form a good ohmic contact with the metal electrode, the second sublayer 420 (GaAs layer) is closer to the metal electrode than the first sublayer 410 (AlInGaAs layer), and the second sublayer 420 (GaAs layer) can form a good ohmic contact with the metal electrode. Although the second sublayer 420 (GaAs layer) has a lattice mismatch with the third subcell 330 (InGaAs subcell) and the first sublayer 410 (InGaAs layer), the thickness of the second sublayer 420 (GaAs layer) can be relatively thin, so that the second sublayer 420 is in a strained state, avoiding the impact of lattice mismatch on device performance.
[0059] When the first sublayer 410 is an AlInGaAs layer and the second sublayer 420 is a GaAsSb layer, the advantages are that, due to the larger band gap of the first sublayer 410 (AlInGaAs layer), the absorption of light by the second ohmic contact layer 400 can be significantly reduced, thus improving the secondary absorption effect of the battery; and the second sublayer 420 (GaAsSb layer) is lattice-matched with the third sub-cell 330 (InGaAs sub-cell); although the second sublayer 420 (GaAsSb layer) may absorb some light due to its small band gap, the thickness of the second sublayer 420 (GaAsSb layer) can be set to be relatively thin, so that the absorption of light by the second ohmic contact layer 400 can still be significantly reduced due to the larger band gap of the first sublayer 410 (AlInGaAs layer), thus improving the secondary absorption effect of the battery.
[0060] Furthermore, when the first sublayer 410 of the second ohmic contact layer 400 is an AlInGaAs layer, the Al composition x of the first sublayer 410 can be set to satisfy: 0 < x ≤ 0.2, so that the first sublayer 410 can also achieve good ohmic contact with the metal electrode.
[0061] Based on any of the above embodiments, optionally, in some embodiments of this application, regardless of whether the first sub-layer 410 is an InGaAs layer or an AlInGaAs layer, the thickness of the first sub-layer 410 can range from 100nm to 500nm, including the endpoint values.
[0062] Based on any of the above embodiments, optionally, in some embodiments of this application, regardless of whether the first sub-layer 410 is an InGaAs layer or an AlInGaAs layer, the In composition y of the first sub-layer 410 satisfies: 0.2≤y≤0.4. Specifically, the In composition of the InGaAs material of the third sub-cell 330 (InGaAs sub-cell) can be 0.3, and the In composition y of the first sub-layer 410 can also be 0.3, so as to facilitate lattice matching.
[0063] Specifically, in some embodiments of this application, the multi-junction solar cell structure provided in this application is an inverted (Al)GaInP / GaAs / InGaAs triple-junction solar cell structure, such as... Figure 4 As shown, where:
[0064] The first ohmic contact layer 200 is an n-type GaAs layer;
[0065] The first sub-cell 310 includes a first window layer 311, a first emitter region 312, a first base region 313, and a first back field layer 314 stacked along a direction away from the first substrate 100. The first window layer 311 can be an n-type AlInP layer, the first emitter region 312 can be an n-type AlGaInP layer, the first base region 313 can be a p-type AlGaInP layer, and the first back field layer 314 can be a p-type AlGaInP layer.
[0066] In the first tunnel junction 340, the n-type layer can be an n-type GaAs layer or an n-type GaInP layer, and the n-type doping is Si or Te; the p-type layer can be a p-type AlGaAs layer, and the p-type doping is C.
[0067] The second sub-cell 320 includes a second window layer 321, a second emitter region 322, a second base region 323, and a second back field layer 324 stacked along a direction away from the first substrate 100. The second window layer 321 can be an n-type GaInP layer, an AlGaInP layer, or an AlInP layer; the second emitter region 322 can be an n-type GaAs layer or an n-type GaInP layer; the second base region 323 can be a p-type GaAs layer; and the second back field layer 324 can be a p-type GaInP layer or a p-type AlGaAs layer.
[0068] In the second tunnel junction 350, the n-type layer can be an n-type GaAs layer or an n-type GaInP layer, and the n-type doping is Si or Te; the p-type layer can be a p-type AlGaAs layer, and the p-type doping is C doping.
[0069] The modified buffer layer 360 can be an AlGaInAs layer or a GaInP layer, with a band gap higher than that of the third sub-cell 330 (InGaAs sub-cell) to avoid light absorption. The modified buffer layer 360 may include an m-layer sequence stacked along the direction from the second sub-cell 320 (GaAs sub-cell) to the third sub-cell 330 (InGaAs sub-cell), where m ≥ 3 and m is an integer. The lattice constant of each layer sequence in the modified buffer layer 360 is greater than that of the second sub-cell 320 (GaAs sub-cell), and the lattice constant of each layer sequence increases along the direction from the second sub-cell 320 (GaAs sub-cell) to the third sub-cell 330 (InGaAs sub-cell). That is, the modified buffer layer 360 is higher in the second sub-cell 320 (GaAs sub-cell) than the third sub-cell 330 (InGaAs sub-cell). The second sub-cell (GaAs sub-cell) and the third sub-cell (InGaAs sub-cell) 330 act as a lattice transition, effectively releasing the residual stress caused by lattice mismatch between the second sub-cell (GaAs sub-cell) 320 and the third sub-cell (InGaAs sub-cell), and effectively blocking the extension of dislocations caused by lattice mismatch between the second sub-cell (GaAs sub-cell) 320 (GaAs sub-cell) and the third sub-cell (InGaAs sub-cell) 330 (InGaAs sub-cell) into the active region of the third sub-cell (InGaAs sub-cell), thereby improving the performance of the multi-junction solar cell structure.
[0070] It is understandable that in the modified buffer layer 360, the lattice constant of each layer sequence increases along the direction from the second sub-cell 320 (GaAs sub-cell) to the third sub-cell 330 (InGaAs sub-cell). Thus, when growing a layer sequence with a relatively larger lattice constant on the i-th layer sequence with a relatively smaller lattice constant, compressive stress will be generated, where 1≤i≤m-1. Furthermore, if the lattice constant of the m-th layer sequence in the modified buffer layer 360 is set to be greater than that of the third sub-cell 330, i.e., the m-th layer sequence is an overshoot layer, then when growing a third sub-cell 330 (InGaAs sub-cell) with a relatively smaller lattice constant on the m-th layer sequence with a relatively larger lattice constant, tensile stress will be generated. This is different from the compressive stress generated by the gradual increase of the lattice constant of the preceding sequences. On the one hand, it can compensate for the residual stress generated by the preceding sequences, and on the other hand, it can prevent the dislocations of the modified buffer layer 360 from extending to the third sub-cell 330 (InGaAs sub-cell).
[0071] The third sub-cell 330 includes a third window layer 331, a third emitter region 332, a third base region 333, and a third back field layer 334 stacked along a direction away from the first substrate 100. The third window layer 331 can be an n-type GaInP layer or an AlGaInP layer, the third emitter region 332 can be an n-type InGaAs layer or an n-type GaInP layer, the third base region 333 can be a p-type InGaAs layer, and the third back field layer 334 can be a p-type GaInP layer or a p-type AlInGaAs layer.
[0072] Accordingly, embodiments of this application also provide a method for fabricating a multi-junction solar cell structure, the method comprising:
[0073] S100: As Figure 1 As shown, a first substrate 100 is provided;
[0074] S200: such as Figure 1 As shown, a sacrificial layer 500, a first ohmic contact layer 200, a plurality of sub-cells 300 and a second ohmic contact layer 400 are formed on one side of the first substrate 100 in a direction opposite to the first substrate 100. The second ohmic contact layer 400 includes a first sub-layer 410 and a second sub-layer 420 stacked in a direction opposite to the first substrate 100. The first sub-layer 410 is an In-containing material layer and the second sub-layer 420 is a GaAs layer or a GaAsSb layer.
[0075] S300: such as Figure 2 As shown, the battery epitaxial structure formed by the first ohmic contact layer 200 to the second ohmic contact layer 400 is transferred to the second substrate 110 from the side of the second ohmic contact layer 400.
[0076] S400: such as Figure 3 As shown, the sacrificial layer 500 is etched to peel off the first substrate 100.
[0077] Optionally, the first substrate 100 can be a GaAs substrate.
[0078] Optionally, the first ohmic contact layer 200 can be an n-type GaAs layer.
[0079] Optionally, the first sublayer 410 of the second ohmic contact layer 400 can be an InGaAs layer or an AlInGaAs layer, and the second sublayer 420 of the second ohmic contact layer 400 can be a GaAs layer or a GaAsSb layer; when the first sublayer 410 is an AlInGaAs layer, its Al composition x can satisfy: 0 < x ≤ 0.2.
[0080] Optionally, the thickness of the second sublayer 420 ranges from 10nm to 100nm, including the endpoint values; the thickness of the first sublayer 410 ranges from 100nm to 500nm, including the endpoint values.
[0081] Optionally, regardless of whether the first sublayer 410 is an InGaAs layer or an AlInGaAs layer, the In component y of the first sublayer 410 can satisfy: 0.2≤y≤0.4.
[0082] Optionally, the multi-junction solar cell structure obtained can be an inverted (Al)GaInP / GaAs / InGaAs triple-junction solar cell structure, such as... Figure 4As shown, where:
[0083] The first sub-cell 310 includes a first window layer 311, a first emitter region 312, a first base region 313, and a first back field layer 314 stacked along a direction away from the first substrate 100. The first window layer 311 can be an n-type AlInP layer, the first emitter region 312 can be an n-type AlGaInP layer, the first base region 313 can be a p-type AlGaInP layer, and the first back field layer 314 can be a p-type AlGaInP layer.
[0084] In the first tunnel junction 340, the n-type layer can be an n-type GaAs layer or an n-type GaInP layer, and the n-type doping is Si or Te; the p-type layer can be a p-type AlGaAs layer, and the p-type doping is C.
[0085] The second sub-cell 320 includes a second window layer 321, a second emitter region 322, a second base region 323, and a second back field layer 324 stacked along a direction away from the first substrate 100. The second window layer 321 can be an n-type GaInP layer, an AlGaInP layer, or an AlInP layer; the second emitter region 322 can be an n-type GaAs layer or an n-type GaInP layer; the second base region 323 can be a p-type GaAs layer; and the second back field layer 324 can be a p-type GaInP layer or a p-type AlGaAs layer.
[0086] In the second tunnel junction 350, the n-type layer can be an n-type GaAs layer or an n-type GaInP layer, and the n-type doping is Si or Te; the p-type layer can be a p-type AlGaAs layer, and the p-type doping is C doping.
[0087] The modified buffer layer 360 can be an AlGaInAs layer or a GaInP layer, with a band gap higher than that of the third sub-cell 330 (InGaAs sub-cell) to avoid light absorption. The modified buffer layer 360 may include an m-layer sequence stacked along the direction from the second sub-cell 320 (GaAs sub-cell) to the third sub-cell 330 (InGaAs sub-cell), where m ≥ 3 and m is an integer. The lattice constant of each layer sequence in the modified buffer layer 360 is greater than that of the second sub-cell 320 (GaAs sub-cell), and the lattice constant of each layer sequence increases along the direction from the second sub-cell 320 (GaAs sub-cell) to the third sub-cell 330 (InGaAs sub-cell). That is, the modified buffer layer 360 is higher in the second sub-cell 320 (GaAs sub-cell) than the third sub-cell 330 (InGaAs sub-cell). The second sub-cell (GaAs sub-cell) and the third sub-cell (InGaAs sub-cell) 330 act as a lattice transition, effectively releasing the residual stress caused by lattice mismatch between the second sub-cell (GaAs sub-cell) 320 and the third sub-cell (InGaAs sub-cell), and effectively blocking the extension of dislocations caused by lattice mismatch between the second sub-cell (GaAs sub-cell) 320 (GaAs sub-cell) and the third sub-cell (InGaAs sub-cell) 330 (InGaAs sub-cell) into the active region of the third sub-cell (InGaAs sub-cell), thereby improving the performance of the multi-junction solar cell structure.
[0088] It is understandable that in the modified buffer layer 360, the lattice constant of each layer sequence increases along the direction from the second sub-cell 320 (GaAs sub-cell) to the third sub-cell 330 (InGaAs sub-cell). Thus, when growing a layer sequence with a relatively larger lattice constant on the i-th layer sequence with a relatively smaller lattice constant, compressive stress will be generated, where 1≤i≤m-1. Furthermore, if the lattice constant of the m-th layer sequence in the modified buffer layer 360 is set to be greater than that of the third sub-cell 330, i.e., the m-th layer sequence is an overshoot layer, then when growing a third sub-cell 330 (InGaAs sub-cell) with a relatively smaller lattice constant on the m-th layer sequence with a relatively larger lattice constant, tensile stress will be generated. This is different from the compressive stress generated by the gradual increase of the lattice constant of the preceding sequences. On the one hand, it can compensate for the residual stress generated by the preceding sequences, and on the other hand, it can prevent the dislocations of the modified buffer layer 360 from extending to the third sub-cell 330 (InGaAs sub-cell).
[0089] The third sub-cell 330 includes a third window layer 331, a third emitter region 332, a third base region 333, and a third back field layer 334 stacked along a direction away from the first substrate 100. The third window layer 331 can be an n-type GaInP layer or an AlGaInP layer, the third emitter region 332 can be an n-type InGaAs layer or an n-type GaInP layer, the third base region 333 can be a p-type InGaAs layer, and the third back field layer 334 can be a p-type GaInP layer or a p-type AlInGaAs layer.
[0090] When fabricating a multi-junction solar cell structure using the method provided in the embodiments of this application, when forming a stacked first ohmic contact layer 200, multiple sub-cells 300, and a second ohmic contact layer 400 on one side of the first substrate 100 in a direction away from the first substrate 100, especially when forming the second ohmic contact layer 400 on the surface of the cell epitaxial structure, an In-containing first sub-layer 410 is first grown, followed by the growth of a GaAs layer or a GaAsSb layer as the second sub-layer 420. In this way, not only do the first sub-layer 410 and the second sub-layer 420 together constitute an ohmic contact layer to form a good ohmic contact with the metal electrode, but also, since the In-containing first sub-layer 410 is covered with a GaAs layer or a GaAsSb layer as the second sub-layer 420, and the second sub-layer 420 is an In-free material layer, the volatilization of In atoms from the In-containing first sub-layer 410 into the reaction chamber can be reduced or avoided, thereby reducing the number of In atoms residing in the reaction chamber, i.e., reducing the contamination and impact of residing In atoms on the reaction chamber, and improving the fabrication yield of the multi-junction solar cell structure. Furthermore, in the second ohmic contact layer 400, the second sub-layer 420 is closer to the metal electrode than the first sub-layer 410, and the second sub-layer 420 is made of GaAs or GaAsSb, which can form a good ohmic contact with the metal electrode.
[0091] The various parts of this manual are described in a combination of parallel and progressive methods. Each part focuses on the differences between the other parts, and the same or similar parts can be referred to each other.
[0092] The features described above regarding the disclosed embodiments can be substituted or combined with each other to enable those skilled in the art to implement or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A multi-junction solar cell structure, characterized by, The application relates to a solar cell, comprising: a first substrate; a first ohmic contact layer, a plurality of sub-cells and a second ohmic contact layer stacked in a direction away from the first substrate on one side of the first substrate; the second ohmic contact layer comprises a first sub-layer and a second sub-layer stacked in a direction away from the first substrate, the first sub-layer is an In-containing material layer, and the second sub-layer is a GaAs layer or a GaAsSb layer; the plurality of sub-cells comprises a first sub-cell, a second sub-cell and a third sub-cell stacked in a direction away from the first substrate, a first tunnel junction is arranged between the first sub-cell and the second sub-cell, and a second tunnel junction and a metamorphic buffer layer are arranged between the second sub-cell and the third sub-cell in a direction away from the first substrate; the first sub-cell is an AlGaInP sub-cell or a GaInP sub-cell, the second sub-cell is a GaAs sub-cell, and the third sub-cell is an InGaAs sub-cell.
2. The multi-junction solar cell structure of claim 1, wherein, the first sub-layer is an InGaAs layer.
3. The multi-junction solar cell structure of claim 1, wherein, the first sub-layer is an AlInGaAs layer.
4. The multi-junction solar cell structure of claim 3, wherein, the Al component x of the first sub-layer satisfies 0 < x <= 0.
2.
5. The multi-junction solar cell structure of claim 1, wherein, the thickness of the second sub-layer ranges from 10nm to 100nm, inclusive.
6. The multi-junction solar cell structure of claim 1, wherein, the thickness of the first sub-layer ranges from 100nm to 500nm, inclusive.
7. The multi-junction solar cell structure of claim 1, wherein, the metamorphic buffer layer is an AlGaInAs layer or a GaInP layer, the metamorphic buffer layer comprises an m-layer sequence stacked in a direction from the second sub-cell to the third sub-cell, m >= 3, m is an integer, the lattice constant of each layer of the sequence is greater than the lattice constant of the second sub-cell, the lattice constant of each layer of the sequence increases in the direction from the second sub-cell to the third sub-cell, and the lattice constant of the m-layer sequence is greater than the lattice constant of the third sub-cell.
8. The multi-junction solar cell structure according to any of claims 1 to 6, characterized in that the In component y of the first sub-layer satisfies 0.2 <= y <= 0.
4.
9. The multi-junction solar cell structure according to any of claims 1 to 6, characterized in that a sacrificial layer is further arranged between the first substrate and the first ohmic contact layer, and the sacrificial layer is an AlAs layer.