Compound solar cell structure with adjustable band edge and preparation method thereof

Abstract

The invention provides a band-edge-adjustable compound solar cell structure and a preparation method thereof. The band-edge-adjustable compound solar cell structure comprises a supporting substrate, a back field layer, a base region layer, a band gap regulation and control layer, an emitter region layer, a window layer and a contact layer. Wherein the band gap regulation and control layer is composed of GaAs buffer layers at the two ends and a GaAs (1-y) Py layer I, an In < x > Ga (1-x) As layer and a GaAs (1-y) Py layer II strain layer which are periodically arranged in the middle, x is larger than 0 and smaller than 0.5, and y is larger than 0 and smaller than 1. And each period comprises an In < x > Ga < 1-x > As layer and a GaAs < 1-y > Py layer with a set thickness. According to the structure, the band edge light absorption range of the solar cell is expanded, material defects and dislocation stripes are weakened under the condition of strain balance, the photon utilization efficiency is improved, a large adjustment range is provided for a spectral current balance strategy of a multi-junction solar cell, and the photoelectric conversion efficiency of a five-junction / six-junction solar cell is further improved.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, and specifically relates to a compound solar cell structure with adjustable edges and its preparation method. Background Technology

[0002] Solar cells are devices that convert light energy into electrical energy using the photovoltaic effect, and they are widely used in aerospace, military, and civilian fields. Compound solar cells, in particular, are III-V semiconductor solar cell devices deposited through metal-organic vapor phase epitaxy (MOE). They are widely used in multi-junction solar cell technology; currently, five-junction solar cells have achieved a photoelectric conversion efficiency of 36% in spatial spectral (AM0) mode, with a cell area exceeding 20 cm². 2 This can effectively increase the power generation density of satellite payloads and reduce the weight of solar panels. However, the band edge of GaAs cells with a band gap of 1.4 eV is relatively fixed, making it difficult to modulate the band edge through doping with main group elements. This limits the performance of GaAs cells in multi-junction solar cells and makes it difficult to further improve the photoelectric conversion efficiency of multi-junction solar cells. Summary of the Invention

[0003] To overcome the shortcomings of the prior art, the inventors have conducted intensive research and provided a compound solar cell structure with adjustable band edges and its preparation method, thereby achieving adjustable band edges in the compound solar cell, expanding the range of photon absorption, and increasing the current matching adjustment capability of multi-junction solar cells, thus completing the present invention.

[0004] The technical solution provided by this invention is as follows:

[0005] In a first aspect, a compound solar cell structure with adjustable bandgap includes, from bottom to top, a supporting substrate, a back surface layer, a base region layer, a bandgap control layer, an emitter region layer, a window layer, and a contact layer;

[0006] The bandgap control layer comprises a bottom GaAs buffer layer, a top GaAs buffer layer, and multiple periodically repeating strain layers; each periodic strain layer contains GaAs from bottom to top. 1-y P y Layer I, In x Ga 1-x As layer and GaAs 1-y P y Layer II, where x is greater than 0 and less than 0.5, and y is greater than 0 and less than 1.

[0007] Secondly, a method for preparing a compound solar cell structure with adjustable bandgap uses metal-organic vapor phase epitaxy to sequentially grow and deposit a back field layer, a base layer, a bandgap control layer, an emitter layer, a window layer, and a contact layer on a supporting substrate in either the forward or reverse direction. The preferred epitaxial growth temperature is 620℃~750℃.

[0008] The tunable edge compound solar cell structure and its preparation method provided by the present invention have the following beneficial effects:

[0009] (1) The present invention provides a compound solar cell structure with adjustable bandgap. In order to expand the bandgap range of the compound solar cell, strain-balanced epitaxial growth can be used to grow In with a narrow bandgap and a large lattice constant. x Ga 1-x As and GaAs with wide bandgap and small lattice constant 1-y P y By combining these elements into a bandgap adjustment layer, within a critical thickness, the bandgap adjustment layer will maintain strain growth, which can maximally suppress the generation of internal defects and dislocations. Periodically arranged bandgap adjustment layers can expand to form new absorption band positions, thereby extending the bandgap range of compound solar cells; compound solar cells using this structure can extend the bandgap range from 1.42 eV to below 1.3 eV, improving the photon utilization rate of compound solar cells in the infrared band.

[0010] (2) The method for preparing edge-tunable compound solar cells provided by the present invention has a smooth and flat surface with no dislocation stripe distribution after metal-organic vapor phase epitaxial growth and deposition. It can be widely used in multi-junction solar cell devices including bonded solar cells and mismatch buffer layer solar cells to improve current matching adjustment redundancy and photoelectric conversion efficiency. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the structure of a compound solar cell in the prior art.

[0012] Figure 2 This is a schematic diagram of the edge-adjustable compound solar cell structure provided by the present invention.

[0013] Figure 3 This is a schematic diagram of the bandgap control layer structure in the tunable compound solar cell provided by the present invention.

[0014] Figure 4 The graph shows the internal quantum efficiency test results of the compound solar cell in Comparative Example 1 and the edge-tunable compound solar cell in Example 1 of this invention.

[0015] Figure 5 The graph shows the internal quantum efficiency test results of the compound solar cell in Comparative Example 1 and the edge-tunable compound solar cell in Example 2 of this invention. Detailed Implementation

[0016] The features and advantages of the present invention will become clearer and more apparent from the following detailed description.

[0017] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0018] In existing technologies, such as Figure 1 As shown, the compound solar cell structure mainly comprises, from bottom to top, an epitaxially grown and deposited support substrate 1, a back surface layer 2, a base region layer 3, an emitter region layer 4, a window layer 5, and a contact layer 6. Figure 1 The band gap of the compound solar cell structure shown is determined by the base layer 3. Since the base layer 3 is composed of GaAs binary semiconductor material, its band gap is a fixed 1.4 eV, which cannot be adjusted, thus limiting its application in multi-junction solar cells.

[0019] like Figure 2 As shown, the present invention provides a compound solar cell structure with adjustable bandgap, comprising a support substrate A, a back field layer B, a base region layer C, a bandgap control layer D, an emitter region layer E, a window layer F, and a contact layer G, which are epitaxially grown and deposited sequentially from bottom to top.

[0020] The supporting substrate A is a p-type doped GaAs substrate with Zn as the dopant and a doping concentration greater than 1 × 10⁻⁶. 18 cm -3 .

[0021] The back field layer B is p-type doped Ga. 0.5 In 0.5 P or Al x Ga 1-x As, where x is greater than 0 and less than 0.8, the doping atom is C or Zn, and the doping concentration is greater than 1 × 10⁻⁶. 17 cm -3 .

[0022] The base layer C is p-type doped GaAs, with C or Zn as the doping atoms, and the doping concentration is greater than 1 × 10⁻⁶. 15 cm -3 And less than 1×10 18 cm -3 .

[0023] The emitter layer E is n-type doped GaAs or Ga 0.5 In 0.5 P, doped with Si atoms, with a doping concentration greater than 1×10⁻⁶. 17 cm -3 .

[0024] The window layer F is an n-type doped Al 0.5 In 0.5 P, doped with Si atoms, with a doping concentration greater than 1×10⁻⁶.17 cm -3 .

[0025] The contact layer G is n-type doped GaAs with Si as the doping atoms, and the doping concentration is greater than 1 × 10⁻⁶. 18 cm -3 .

[0026] like Figure 3 As shown, the bandgap control layer D comprises a bottom GaAs buffer layer D1, a top GaAs buffer layer D5, and multiple periodically repeating strain layers D6. Each period of strain layer D6 contains GaAs... 1-y P y Layer ID2, In x Ga 1-x As layer D3 and GaAs 1-y P y Layer IID4, where x is greater than 0 and less than 0.5, and y is greater than 0 and less than 1. GaAs in each period. 1-y P y Layer ID2, In x Ga 1-x As layer D3 and GaAs 1-y P y The thickness and composition of layer IID4 remain constant and satisfy stress balance, and the thickness should be less than the maximum thickness that would have a destructive effect on the crystal structure. The bottom GaAs buffer layer D1, the top GaAs buffer layer D5, and the strain layer D6 are all unintentionally doped.

[0027] and Figure 1 Compared to existing technologies, the bandgap-tunable compound solar cell structure provided by this invention can extend the absorption bandgap edge position of the compound solar cell. Depending on the composition and thickness of the bandgap tuning layer, the bandgap can be extended from 1.42 eV to below 1.3 eV, increasing the photon utilization band. Simultaneously, the additionally introduced stress-balancing structure (bandgap tuning layer) ensures that the semiconductor material is in a strained state, reducing the generation of defects and dislocations.

[0028] The present invention also provides a method for fabricating a compound solar cell with adjustable bandgap. The method employs metal-organic vapor phase epitaxy to sequentially epitaxially grow and deposit a back field layer B, a base layer C, a bandgap control layer D, an emitter layer E, a window layer F, and a contact layer G on a supporting substrate A in either the forward or reverse direction. The lattice constants of the back field layer B, the base layer C, the bandgap control layer D, the emitter layer E, the window layer F, and the contact layer G are the same as those of the supporting substrate. The epitaxial growth temperature is 620℃~750℃.

[0029] The bandgap control layer D is obtained by sequential epitaxial growth and deposition of the bottom GaAs buffer layer D1, the strain layer D6, and the top GaAs buffer layer D5. Specifically:

[0030] Immediately after the epitaxial growth and deposition of the bottom GaAs buffer layer D1 is completed, the Ga source valve is turned off, while the arsine valve remains open. After 4–6 seconds, the phosphine valve is opened, and after 1–2 seconds, the Ga source valve is reopened to begin depositing GaAs of the set thickness. 1-y P y Layer ID2. GaAs 1-y P y Immediately after the epitaxial growth deposition of layer ID2 is completed, turn off the Ga source valve while keeping the arsine and phosphine valves open. After 4–6 seconds, turn off the phosphine valve, and after 1–2 seconds, turn on the Ga source and In source valves to begin depositing the In layer of the set thickness. x Ga 1-x As layer D3. In x Ga 1-x Immediately after the epitaxial growth and deposition of the As layer (D3) is completed, turn off the In and Ga source valves, keeping the arsine valve open. After 4–6 seconds, open the phosphine valve, and after 1–2 seconds, open the Ga source valve again to begin depositing the GaAs layer of the set thickness. 1-y P y Layer IID4. Afterwards, GaAs deposition began periodically and alternately. 1-y P y Layer I, In x Ga 1-x As layer and GaAs 1-y P y Layer II. After reaching the set number of cycles, immediately shut off the Ga source valve while keeping the arsine and phosphine valves open. After 4-6 seconds, shut off the phosphine valve and after 1-2 seconds, open the Ga source valve to begin depositing the top GaAs buffer layer D5.

[0031] Example

[0032] Example 1

[0033] The edge-tunable compound solar cell structure of this embodiment includes, from bottom to top, a support substrate A, a back field layer B, a base region layer C, a bandgap control layer D, an emitter region layer E, a window layer F, and a contact layer G, which are epitaxially grown and deposited sequentially.

[0034] The supporting substrate A is a p-type doped GaAs substrate with Zn as the dopant and a doping concentration of 4 × 10⁻⁶. 18 cm -3 Thickness 350μm.

[0035] The back field layer B is p-type doped Al 0.1 Ga 0.9 As material, doped with Zn atoms, with a doping concentration of 1×10⁻⁶. 18 cm -3 Thickness 100nm.

[0036] The base layer C is a p-type doped GaAs material with Zn as the dopant and a doping concentration of 1 × 10⁻⁶. 17 cm -3 Thickness 2000nm.

[0037] The emitter layer E is n-type doped Ga 0.5 In 0.5 P material, doped with Si atoms, with a doping concentration of 1×10⁻⁶. 18 cm -3 Thickness 20nm.

[0038] The window layer F is an n-type doped Al 0.5 In 0.5 P material, doped with Si atoms, with a doping concentration of 2 × 10⁻⁶. 18 cm -3 Thickness 100nm.

[0039] The contact layer G is an n-type doped GaAs material with Si as the dopant atoms and a doping concentration of 4 × 10⁻⁶. 18 cm -3 Thickness 300nm.

[0040] The bandgap control layer D consists of a bottom GaAs buffer layer D1, a top GaAs buffer layer D5, and a strain layer D6 that repeats for 60 cycles.

[0041] The bottom GaAs buffer layer D1 is an unintentionally doped GaAs material with a thickness of 50 nm.

[0042] The top GaAs buffer layer D5 is an unintentionally doped GaAs material with a thickness of 50 nm.

[0043] Strained layer D6 contains GaAs 0.917 P 0.083 Layer D2, In 0.10 Ga 0.90 As layer D3 and GaAs 0.917 P 0.083 Layer D4. GaAs 0.917 P 0.083 Layer D2 thickness 9nm, In 0.10 Ga 0.90 The As layer D3 is 8nm thick, GaAs 0.917 P 0.083 Layer D4 has a thickness of 9 nm.

[0044] The method for preparing the edge-tunable compound solar cell provided in Example 1 involves sequentially growing and depositing a back field layer B, a base layer C, a bandgap control layer D, an emitter layer E, a window layer F, and a contact layer G on a supporting substrate A using metal-organic vapor phase epitaxy. The epitaxial growth temperature is 680°C.

[0045] The bandgap control layer D is formed by the epitaxial growth and deposition of the bottom GaAs buffer layer D1, the strain layer D6, and the top GaAs buffer layer D5 in sequence.

[0046] Immediately after the epitaxial growth and deposition of the bottom GaAs buffer layer D1 is completed, the Ga source valve is turned off while the arsine valve remains open. After 5 seconds, the phosphine valve is opened, and after 1 second, the Ga source valve is reopened to begin depositing a 9nm thick GaAs layer. 0.917 P 0.083 Layer D2. GaAs 0.917 P 0.083 Immediately after the epitaxial growth and deposition of layer D2 is completed, the Ga source valve is turned off, while the arsine and phosphine valves remain open. After 5 seconds, the phosphine valve is turned off, and after 1 second, the Ga source and In source valves are turned on to begin depositing an 8 nm thick In layer. 0.10 Ga 0.90 As layer D3. In 0.10 Ga 0.90 Immediately after the epitaxial growth and deposition of the As layer (D3) is completed, the In and Ga source valves are shut off, while the arsine valve remains open. After 5 seconds, the phosphine valve is opened, and after 1 second, the Ga source valve is reopened to begin depositing a 9 nm thick GaAs layer. 0.917 P 0.083 Layer D4. Then, In is periodically deposited alternately. 0.10 Ga 0.90 As layer and GaAs 0.917 P 0.083 After reaching 60 cycles, immediately shut off the Ga source valve while keeping the arsine and phosphine valves open. After 5 seconds, shut off the phosphine valve and after 1 second, open the Ga source valve to begin depositing the top GaAs buffer layer D5.

[0047] The compound solar cell with adjustable band edge prepared by the above method can extend the band edge position to the infrared band, thereby improving photon utilization efficiency. Figure 4 The solid line represents the internal quantum efficiency test results of compound solar cells in the existing technology. Figure 4 The dashed line represents the internal quantum efficiency test results of the edge-tunable compound solar cells obtained in the above embodiments. From... Figure 4 As can be seen, the edge of the dashed line extends to approximately 950nm, which is higher than the 880nm edge of the solid line, thus increasing the photon absorption range.

[0048] Example 2

[0049] This embodiment 2 is the same as embodiment 1, except that the bandgap control layer D consists of a bottom GaAs buffer layer D1, a top GaAs buffer layer D5, and a strain layer D6 that repeats for 60 cycles.

[0050] The bottom GaAs buffer layer D1 is an unintentionally doped GaAs material with a thickness of 50 nm.

[0051] The top GaAs buffer layer D5 is an unintentionally doped GaAs material with a thickness of 50 nm.

[0052] Strained layer D6 contains GaAs 0.912 P 0.088 Layer D2, In 0.07 Ga 0.93 As layer D3 and GaAs 0.912 P 0.088 Layer D4. GaAs 0.912 P 0.088 Layer D2 has a thickness of 12nm, In 0.07 Ga 0.93 The thickness of the As layer D3 is 8 nm, GaAs 0.912 P 0.088 The thickness of layer D4 is 12nm.

[0053] The compound solar cell with adjustable band edge prepared by the above method can extend the band edge position to the infrared band, thereby improving photon utilization efficiency. Figure 5 The solid line represents the internal quantum efficiency test results of compound solar cells in the existing technology. Figure 5 The dashed line represents the internal quantum efficiency test results of the edge-tunable compound solar cells obtained in the above embodiments. From... Figure 5 As can be seen, the edge of the dashed line extends to approximately 910 nm, which is higher than the 880 nm edge of the solid line, thus increasing the photon absorption range.

[0054] Comparative Example

[0055] Comparative Example 1

[0056] The compound solar cell structure of Comparative Example 1 comprises, from bottom to top, a support substrate 1, a back surface layer 2, a base region layer 3, an emitter region layer 4, a window layer 5, and a contact layer 6, which are epitaxially grown and deposited sequentially. The epitaxial structure design and epitaxial growth design, except for the bandgap control layer, are the same as in Example 1.

[0057] The compound solar cell provided in Comparative Example 1 does not possess the property of band-side tunability; its quantum efficiency test curve is as follows. Figure 4As shown by the solid line, its band gap is entirely determined by the base material. Since the base material is composed of the binary semiconductor material GaAs, its band gap is fixed at 1.4 eV, which is 880 nm at the band edge.

[0058] In summary, this invention reconstructs a compound solar cell structure with adjustable bandgap by adding a bandgap adjustment layer, which expands the bandgap absorption range of the solar cell, reduces the generation of material defects and dislocation fringes under strain balance conditions, improves photon utilization efficiency, provides a larger adjustment range for the spectral current balance strategy of multi-junction solar cells, and will further improve the photoelectric conversion efficiency of five-junction / six-junction solar cells.

[0059] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0060] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A compound solar cell structure with tunable band edges, characterized by, The solar cell comprises a supporting substrate, a back field layer, a base region layer, a band gap regulation layer, an emitting region layer, a window layer and a contact layer from bottom to top. The bandgap modulation layer includes a bottom GaAs buffer layer, a top GaAs buffer layer, and a plurality of periodically repeating strain layers; each period of strain layers includes, from bottom to top, a GaAs 1-y P y Layer I, In x Ga 1-x As layer and a GaAs 1-y P y Layer II, where x is greater than 0 and less than 0.5, and y is greater than 0 and less than 1.

2. The compound solar cell structure with tunable edges according to claim 1, wherein, The support substrate is a p-doped GaAs substrate, the doping atoms are Zn, and the doping concentration is greater than 1 x 1018cm-3. 18 cm -3 .

3. The compound solar cell structure with tunable edges of claim 1, wherein, The back field layer is p-type doped Ga 0.5 In 0.5 P or Al x Ga 1-x As, where x is greater than 0 and less than 0.8, the doping atom is C or Zn, and the doping concentration is greater than 1 x 10 17 cm -3 .

4. The compound solar cell structure with tunable edges of claim 1, wherein, The base region layer is p-type doped GaAs, the doping atoms are C or Zn, the doping concentration is greater than 1 x 10 15 cm -3 and less than 1 x 10 18 cm -3 .

5. The compound solar cell structure with tunable edges of claim 1, wherein, The emitter region layer is n-type doped GaAs or Ga 0.5 In 0.5 P, the doping atom is Si, and the doping concentration is greater than 1 x 10 17 cm -3 .

6. The compound solar cell structure with tunable edges of claim 1, wherein, The window layer is n-type doped Al 0.5 In 0.5 P, the doping atom is Si, and the doping concentration is greater than 1 x 10 17 cm -3 .

7. The compound solar cell structure with tunable edges of claim 1, wherein, The contact layer is n-type doped GaAs, the doping atom is Si, the doping concentration is greater than 1 x 1018cm-3. 18 cm -3 .

8. The compound solar cell structure with tunable edges of claim 1, wherein, The lattice constants of the back field layer, the base region layer, the band gap regulation layer, the emitting region layer, the window layer and the contact layer are the same as that of the supporting substrate.

9. A method of producing a compound solar cell structure with adjustable band edges according to one of claims 1 to 8, characterized in that The back field layer, the base region layer, the band gap regulation layer, the emitting region layer, the window layer and the contact layer are prepared by metal organic vapor phase epitaxy method, and are sequentially and positively or reversely epitaxially grown on the supporting substrate, and the epitaxial growth temperature is preferably 620-750 DEG C.

10. The method of claim 9, wherein the method further comprises the step of: The band gap modulation layer is deposited by epitaxial growth of a bottom GaAs buffer layer, a strain layer and a top GaAs buffer layer in sequence, and the specific method is as follows: immediately after the epitaxial growth and deposition of the bottom GaAs buffer layer is completed, the Ga source valve is closed, the arsine valve is kept open, the phosphine valve is opened after 4-6 seconds, the Ga source valve is opened again after 1-2 seconds, and the deposition of GaAs with a set thickness is started 1-y P y Layer I; GaAs 1-y P y Immediately after the epitaxial growth and deposition of the layer I is completed, the Ga source valve is closed, the arsine and phosphine valves are kept open, the phosphine valve is closed after 4-6 seconds, the Ga source and In source valves are opened after 1-2 seconds, and the deposition of In with a set thickness is started x Ga 1-x As layer; In x Ga 1-x Immediately after the epitaxial growth and deposition of the GaAs layer is completed, the In source and Ga source valves are closed, the arsine valve is kept open, the phosphine valve is opened after 4-6 seconds, the Ga source valve is opened again after 1-2 seconds, and the deposition of GaAs with a set thickness is started 1-y P y Layer II; then the periodic alternate deposition of GaAs is started 1-y P y Layer I, In x Ga 1-x As layer and GaAs 1-y P y Layer II; immediately after a set number of periods is reached, the Ga source valve is closed, the arsine and phosphine valves are kept open, the phosphine valve is closed after 4-6 seconds, the Ga source valve is opened after 1-2 seconds, and the deposition of the top GaAs buffer layer is started. ​

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