A four-junction solar cell and its preparation method and application

Abstract

The present invention discloses a four-junction solar cell and a preparation method and application thereof. The four-junction solar cell of the present invention sequentially comprises a Ge substrate, a GaAs buffer layer, a two-dimensional conductive material layer, an AlGaInAs / GaAsP superlattice structure layer, a GaInAs subcell, an AlGaInAs subcell and an AlGaInP subcell. The four-junction solar cell of the present invention reduces the threading dislocation density of the high In component target material layer in the mismatch structure four-junction solar cell, ultimately reduces the non-irradiation recombination probability inside each subcell, and improves the open circuit voltage and fill factor FF of the four-junction cell.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a four-junction solar cell and a preparation method and application thereof. Background Art

[0002] Multi-junction solar cells based on GaAs materials have been maturely applied in the field of space satellites. At present, most of the multi-junction cells used in space are lattice-matched GaInP / GaAs / Ge triple-junction cells. Due to the overall material lattice matching, there are fewer material defects and the space conversion efficiency is stable at around 30%. However, the band gap combination of GaInP / GaAs / Ge triple-junction cells is 1.9 / 1.4 / 0.67eV, which is not the theoretical optimal band gap combination for triple-junction cells. The band gap of the middle cell GaAs is too high, and the short-circuit current of the low cell Ge is much larger than that of other sub-cells, so the theoretical efficiency is limited. Adding a certain amount of In to the middle cell material GaAs to form GaInAs material can reduce the material band gap, and introducing other materials can form a four-junction cell.

[0003] However, existing four-junction cells have high material defect density and high threading dislocation density, which limits the material quality of each sub-cell and causes more non-irradiation recombination, thus affecting the overall voltage and FF of the solar cell.

[0004] Therefore, it is necessary to develop a new four-junction solar cell. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the first aspect of the present invention proposes a four-junction solar cell that can effectively reduce the threading dislocation density, reduce the probability of non-irradiated recombination within each sub-cell, and improve the overall open circuit voltage and fill factor (FF) of the four-junction cell.

[0006] The second aspect of the present invention also provides a method for preparing a four-junction solar cell.

[0007] The third aspect of the present invention also provides an application of a four-junction solar cell.

[0008] According to a first aspect of the present invention, an embodiment provides a four-junction solar cell, which comprises, in sequence, a Ge substrate, a GaAs buffer layer, a two-dimensional conductive material layer, an AlGaInAs / GaAsP superlattice structure layer, a GaInAs sub-cell, an AlGaInAs sub-cell and an AlGaInP sub-cell.

[0009] The four-junction solar cell according to the embodiment of the present invention has at least the following beneficial effects:

[0010] The four-junction solar cell of the present invention reduces the threading dislocation density of the high In component target material layer in the mismatch structure four-junction solar cell, ultimately reducing the non-irradiation recombination probability inside each sub-cell, and improving the open circuit voltage and FF of the four-junction cell. This is because the present invention introduces a two-dimensional conductive material layer and an AlGaInAs / GaAsP superlattice structure layer, and the two-dimensional conductive material layer can promote the lattice reconstruction of the upper epitaxial material, reduce stress and defects; the superlattice material layer can inhibit the growth of defects through internal strain. Therefore, the combination of the two-dimensional conductive material layer and the superlattice structure layer reduces the threading dislocation density, reduces the non-irradiation recombination probability inside each sub-cell, improves the overall open circuit voltage and FF of the four-junction cell, and obtains a high-efficiency four-junction solar cell.

[0011] According to some embodiments of the present invention, the material in the two-dimensional conductive material layer includes at least one of molybdenum sulfide, graphene or silicene. Thus, when growing the upper epitaxial material, its lattice reconstruction can be achieved, reducing the stress on the epitaxial layer and the production defects.

[0012] According to some embodiments of the present invention, the thickness of the two-dimensional conductive material layer is 5 to 30 nm.

[0013] According to some embodiments of the present invention, the AlGaInAs / GaAsP superlattice structure layer is composed of 10 to 100 pairs of AlGaInAs / GaAsP double-layer structure cycles.

[0014] According to some embodiments of the present invention, in each pair of AlGaInAs / GaAsP double-layer structures, the thickness of AlGaInAs is 2-10 nm, and the thickness of GaAsP is 2-10 nm.

[0015] According to some embodiments of the present invention, the total thickness of the AlGaInAs / GaAsP superlattice structure layer is 100-1000 nm.

[0016] According to some embodiments of the present invention, the thickness of the GaAs buffer layer is 300-1000 nm.

[0017] According to some embodiments of the present invention, the optical band gap of the GaInAs subcell is 1.0-1.1 eV, and the absorption thickness is 2-3 μm.

[0018] According to some embodiments of the present invention, the optical band gap of the AlGaInAs sub-cell is 1.4-1.5 eV, and the absorption thickness is 2-3 μm.

[0019] According to some embodiments of the present invention, the optical band gap of the AlGaInP subcell is 1.9-2.0 eV, and the absorption thickness is 300-700 nm.

[0020] According to some embodiments of the present invention, the Ge substrate is a single-sided or double-sided polished p-type single crystal wafer.

[0021] According to a second aspect of the present invention, a method for preparing a four-junction solar cell is provided, comprising the following steps:

[0022] A GaAs buffer layer is grown on the surface of the Ge substrate, and a two-dimensional conductive material layer is grown on the surface of the GaAs buffer layer; an AlGaInAs / GaAsP superlattice structure layer is grown on the two-dimensional conductive material layer; and a GaInAs sub-cell, an AlGaInAs sub-cell and an AlGaInP sub-cell are sequentially grown on the surface of the AlGaInAs / GaAsP superlattice structure layer.

[0023] According to some embodiments of the present invention, metal organic chemical vapor deposition (MOCVD) or chemical vapor deposition (CVD) technology is used for preparation.

[0024] A third aspect of the present invention provides an application of the above-mentioned four-junction solar cell in a photovoltaic power generation device.

[0025] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0027] Figure 1 It is a schematic diagram of the structure of a four-junction solar cell according to Example 1 of the present invention.

[0028] Among them, 10-Ge substrate; 20-GaAs buffer layer; 30-two-dimensional conductive material layer; 40-AlGaInAs / GaAsP superlattice structure layer; 50-GaInAs sub-cell; 60-AlGaInAs sub-cell; 70-AlGaInP sub-cell. DETAILED DESCRIPTION

[0029] The following are specific embodiments of the present invention, and the technical solutions of the present invention are further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0030] Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0031] Example 1

[0032] This example provides a four-junction solar cell, the structural diagram of which is shown in Figure 1 As shown, the specific steps are: using MOCVD technology to sequentially grow a GaAs buffer layer 20, a two-dimensional conductive material layer 30, an AlGaInAs / GaAsP superlattice structure layer 40, a GaInAs sub-cell 50, an AlGaInAs sub-cell 60 and an AlGaInP sub-cell 70 on the surface of a Ge substrate 10; wherein:

[0033] The Ge substrate 10 is a single-sided polished p-type single crystal wafer;

[0034] The thickness of the GaAs buffer layer is 500 nm.

[0035] The material of the two-dimensional conductive material layer 30 is molybdenum disulfide, and the thickness is 10 nm;

[0036] The AlGaInAs / GaAsP superlattice structure layer is composed of 80 pairs of AlGaInAs / GaAsP double-layer structure cycles. In each pair of AlGaInAs / GaAsP double-layer structures, the thickness of AlGaInAs is 5nm, the thickness of GaAsP is 5nm, and the total thickness of the AlGaInAs / GaAsP superlattice structure layer is 800nm.

[0037] The GaInAs subcell has an optical band gap of 1.0 eV and an absorption thickness of 2.5 μm;

[0038] The AlGaInAs subcell has an optical band gap of 1.4 eV and an absorption thickness of 2.5 μm;

[0039] The AlGaInP subcell has an optical band gap of 1.9 eV and an absorption thickness of 500 nm.

[0040] Example 2

[0041] This example provides a four-junction solar cell, the structural diagram of which is shown in Figure 1 As shown, the specific steps are: using MOCVD technology to sequentially grow a GaAs buffer layer 20, a two-dimensional conductive material layer 30, an AlGaInAs / GaAsP superlattice structure layer 40, a GaInAs sub-cell 50, an AlGaInAs sub-cell 60 and an AlGaInP sub-cell 70 on the surface of a Ge substrate 10; wherein:

[0042] The Ge substrate 10 is a single-sided polished p-type single crystal wafer;

[0043] The thickness of the GaAs buffer layer is 800nm;

[0044] The material of the two-dimensional conductive material layer 30 is graphene, and the thickness is 20 nm;

[0045] The AlGaInAs / GaAsP superlattice structure layer is composed of 50 pairs of AlGaInAs / GaAsP double-layer structure cycles. In each pair of AlGaInAs / GaAsP double-layer structures, the thickness of AlGaInAs is 6nm, the thickness of GaAsP is 8nm, and the total thickness of the AlGaInAs / GaAsP superlattice structure layer is 700nm.

[0046] The GaInAs subcell has an optical band gap of 1.1 eV and an absorption thickness of 3 μm;

[0047] The AlGaInAs subcell has an optical band gap of 1.5 eV and an absorption thickness of 3 μm;

[0048] The AlGaInP subcell has an optical band gap of 2.0 eV and an absorption thickness of 400 nm.

[0049] Comparative Example 1

[0050] Comparative Example 1 provides a conventional Ge-based four-junction solar cell, whose structure and preparation method are basically the same as those of Example 1, except that both the two-dimensional conductive material layer and the AlGaInAs / GaAsP superlattice structure layer are missing.

[0051] Performance Testing

[0052] The four-junction solar cells prepared in the above Examples 1 to 2 and Comparative Example 1 were subjected to simulation tests. The IV performance of the samples was tested at 25°C using an AM0 solar spectrum simulator to calibrate the open circuit voltage and fill factor. The threading dislocation density was tested at 25°C using a cathode fluorescence spectrometer and calibrated through the sample luminescence photos. The results are shown in Table 1.

[0053] Table 1

[0054] Open circuit voltage(V) Fill Factor FF <![CDATA[Penetration dislocation density / cm 2 > Example 1 3.30 0.83 3E5 Example 2 3.48 0.83 5E5 Comparative Example 1 3.15 0.81 5E6

[0055] From Table 1, it can be seen that the multi-junction solar cell provided by the present invention can significantly reduce the penetration defect density of the surface layer of the four-junction solar cell; thereby improving its open circuit voltage and fill factor.

[0056] The above is a detailed description of the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A four-junction solar cell, characterized in that: The four-junction solar cell comprises, in sequence, a Ge substrate, a GaAs buffer layer, a two-dimensional conductive material layer, an AlGaInAs / GaAsP superlattice structure layer, a GaInAs subcell, an AlGaInAs subcell and an AlGaInP subcell; The AlGaInAs / GaAsP superlattice structure layer is composed of 10 to 100 pairs of AlGaInAs / GaAsP double-layer structure cycles; The material in the two-dimensional conductive material layer is selected from molybdenum disulfide; the thickness of the two-dimensional conductive material layer is 5 to 30 nm; the thickness of the GaAs buffer layer is 300 to 1000 nm; The optical band gap of the GaInAs subcell is 1.0-1.1 eV, and the absorption thickness is 2-3 μm; the optical band gap of the AlGaInAs subcell is 1.4-1.5 eV, and the absorption thickness is 2-3 μm; the optical band gap of the AlGaInP subcell is 1.9-2.0 eV, and the absorption thickness is 300-700 nm.

2. The four-junction solar cell according to claim 1, characterized in that: In each pair of AlGaInAs / GaAsP double-layer structures, the thickness of AlGaInAs is 2 to 10 nm, and the thickness of GaAsP is 2 to 10 nm.

3. The four-junction solar cell according to claim 1 or 2, characterized in that: The total thickness of the AlGaInAs / GaAsP superlattice structure layer is 100-1000nm.

4. The method for preparing a four-junction solar cell according to any one of claims 1 to 3, characterized in that: The steps include: A GaAs buffer layer is grown on the surface of the Ge substrate, and a two-dimensional conductive material layer is grown on the surface of the GaAs buffer layer; an AlGaInAs / GaAsP superlattice structure layer is grown on the two-dimensional conductive material layer; and a GaInAs sub-cell, an AlGaInAs sub-cell and an AlGaInP sub-cell are sequentially grown on the surface of the AlGaInAs / GaAsP superlattice structure layer.

5. The preparation method according to claim 4, characterized in that: The material was prepared by chemical vapor deposition technology.

6. Use of the four-junction solar cell according to any one of claims 1 to 3 in photovoltaic power generation equipment.

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