Solar cell epitaxial structure and preparation method thereof

Abstract

The embodiment of the invention relates to the technical field of semiconductors, in particular to a solar cell epitaxial structure and a preparation method thereof. The solar cell epitaxial structure comprises a substrate; the n-type doped GaN layer is positioned on one side of the substrate; the superlattice quantum well structure is located on the side, away from the substrate, of the n-type doped GaN layer, the superlattice quantum well structure comprises a plurality of superlattice layers and a plurality of quantum well layers which are sequentially arranged at intervals, the number of the superlattice layers is the same as that of the quantum well layers, and the n-type doped GaN layer makes contact with the superlattice layers; and a p-type doped GaN layer, wherein the superlattice quantum well structure is located between the n-type doped GaN layer and the p-type doped GaN layer. According to the technical scheme, the photoelectric conversion efficiency of the solar cell can be improved.

Description

Technical Field

[0001] The disclosed embodiments relate to the field of semiconductor technology, and in particular, to a solar cell epitaxial structure and a method for preparing the same. Background Art

[0002] With the development of science and technology, global energy demand continues to expand. However, the fossil energy that is currently used the most is a limited resource that has been accumulated over a long period of time. With the continuous exploitation of humans, fossil energy will inevitably be exhausted. In order to get rid of this dilemma, scientific researchers are eager to find new energy sources. Among the many new energy sources, solar energy is the most concerned and expected because of its advantages such as cleanliness, large reserves and easy access. The bandgap width of the new generation semiconductor material InGaN can be freely adjusted between 0.64eV-3.4eV, completely covering the visible solar spectrum, which is very suitable for the preparation of high-efficiency solar cells. At the same time, it also has the characteristics of direct band gap, low light reflectivity, high radiation resistance and high electron mobility, so it has great potential and broad prospects in the application of solar cells.

[0003] Due to the limitation of crystal quality, it is difficult to prepare InGaN materials that meet the requirements of large thickness, high quality and high In content. In order to make more effective use of the solar spectrum and improve the quality of materials, researchers have proposed the use of quantum well structures to prepare solar cells. Through the quantum well structure, the crystal quality can be improved, the In content can be increased, the absorption band gap of the battery can be more effectively adjusted, the spectral response of the long-wave band can be expanded, and the short-circuit current density can be increased. However, in the quantum well structure (including the quantum well layer), since the lattice constant of InGaN is greater than that of GaN, the quantum well layer is subjected to compressive stress and there is a large piezoelectric polarization field. The existence of this piezoelectric polarization field will cause the energy band to tilt, affect carrier transmission, and reduce the photoelectric conversion efficiency of the quantum well structure. Summary of the invention

[0004] Based on this, it is necessary to address the above technical problems. The present disclosure provides a solar cell epitaxial structure and a preparation method thereof, which are beneficial to improving the photoelectric conversion efficiency of solar cells.

[0005] In a first aspect, the present disclosure provides a solar cell epitaxial structure, comprising:

[0006] substrate;

[0007] an n-type doped GaN layer located on one side of the substrate;

[0008] a superlattice quantum well structure located on a side of the n-type doped GaN layer away from the substrate, the superlattice quantum well structure comprising a plurality of superlattice layers and a plurality of quantum well layers arranged in sequence and spaced apart from each other, the number of the superlattice layers and the number of the quantum well layers being the same, and the n-type doped GaN layer being in contact with the superlattice layer;

[0009] The p-type doped GaN layer, the superlattice quantum well structure is located between the n-type doped GaN layer and the p-type doped GaN layer.

[0010] In some embodiments, the solar cell epitaxial structure further comprises:

[0011] GaN buffer layer;

[0012] The GaN buffer layer is located between the p-type doped GaN and the superlattice quantum well structure.

[0013] In some embodiments, the superlattice layer is composed of In x Ga 1-x N / GaN structure composition;

[0014] In x Ga 1-x In in N / GaN structures x Ga 1-x The thickness of the N layer and the GaN layer is equal and is 5 nm.

[0015] In some embodiments, the In in each of the superlattice layers x Ga 1-x The In content in the N layer first increases and then decreases in a direction away from the substrate.

[0016] In some embodiments, the quantum well layer is composed of In x G a1-x N / GaN structure composition;

[0017] In x Ga 1-x In in N / GaN structures x Ga 1-x The thickness of the N layer is 4 nm. x Ga 1-x The thickness of the GaN layer in the N / GaN structure is 10 nm.

[0018] In some embodiments, the In in each of the quantum well layers x Ga 1-x The In content in the N layer first increases and then decreases in a direction away from the substrate.

[0019] In some embodiments, the solar cell epitaxial structure further comprises:

[0020] n-type electrode and p-type electrode;

[0021] The n-type electrode is disposed on the n-type doped GaN layer, and the p-type electrode is disposed on the p-type doped GaN layer.

[0022] In a second aspect, the present disclosure further provides a method for preparing an epitaxial structure of a solar cell, comprising:

[0023] providing a substrate;

[0024] forming an n-type doped GaN layer on one side of the substrate;

[0025] A superlattice quantum well structure is formed on a side of the n-type doped GaN layer away from the substrate, wherein the superlattice quantum well structure comprises a plurality of superlattice layers and a plurality of quantum well layers which are sequentially spaced apart, the number of the superlattice layers and the number of the quantum well layers are the same, and the n-type doped GaN layer is in contact with the superlattice layer;

[0026] A p-type doped GaN layer is formed on a side of the superlattice quantum well structure away from the n-type doped GaN layer.

[0027] In some embodiments, before forming a p-type doped GaN layer on a side of the superlattice quantum well structure away from the n-type doped GaN layer, the method further comprises:

[0028] A GaN buffer layer is formed on one side of the superlattice quantum well structure, and the GaN buffer layer is located between the superlattice quantum well structure and the p-type doped GaN.

[0029] In some embodiments, after forming a p-type doped GaN layer on a side of the superlattice quantum well structure away from the n-type doped GaN layer, the method further comprises:

[0030] An n-type electrode is formed on the n-type doped GaN layer, and a p-type electrode is formed on the p-type doped GaN layer.

[0031] The solar cell epitaxial structure provided by the embodiment of the present disclosure includes: a substrate; an n-type doped GaN layer located on one side of the substrate; a superlattice quantum well structure located on the side of the n-type doped GaN layer away from the substrate, the superlattice quantum well structure includes a plurality of superlattice layers and a plurality of quantum well layers arranged in sequence, the number of superlattice layers and quantum well layers is the same, the n-type doped GaN layer is in contact with the superlattice layer; a p-type doped GaN layer, the superlattice quantum well structure is located between the n-type doped GaN layer and the p-type doped GaN layer. By arranging a plurality of superlattice layers and a plurality of quantum well layers between the n-type doped GaN layer and the p-type doped GaN layer, and the superlattice layers and the quantum well layers are arranged in sequence, it is possible to insert a superlattice layer between the plurality of quantum well layers, the superlattice layer can be used as a stress release layer, the superlattice layer can be used to release the stress between the epitaxial layer (n-type doped GaN layer) and the quantum well layer, and the superlattice layer can also be used to release the stress between adjacent quantum well layers. At the same time, the superlattice layer reduces the energy band tilt in the quantum well layer, weakens the polarization electric field in the quantum well layer, suppresses carrier recombination, and enables more carriers to reach the cathode and anode, increasing the short-circuit current and thus promoting the photoelectric conversion efficiency. In addition, since the superlattice layer releases the stress between adjacent quantum well layers, it can reduce the lattice mismatch in the quantum well layer, thereby improving the crystal quality and helping to improve the photoelectric conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0034] Figure 1 A schematic diagram of a solar cell epitaxial structure provided by an embodiment of the present disclosure;

[0035] Figure 2 A schematic diagram of another solar cell epitaxial structure provided for the implementation of the present disclosure;

[0036] Figure 3 A schematic diagram of the structure of a superlattice layer provided in an embodiment of the present disclosure;

[0037] Figure 4 A schematic diagram of the structure of a quantum well layer provided in an embodiment of the present disclosure;

[0038] Figure 5A schematic flow chart of a method for preparing an epitaxial structure of a solar cell provided in an embodiment of the present disclosure.

[0039] Among them, 10, substrate; 010, superlattice quantum well structure; 11, n-type doped GaN layer; 12, superlattice layer; 13, quantum well layer; 14, p-type doped GaN layer; 15, GaN buffer layer; 16, n-type electrode; 17, p-type electrode; 01, first superlattice layer; 02, second superlattice layer; 03, third superlattice layer; 04, fourth superlattice layer; 05, fifth superlattice layer; 06, sixth superlattice layer; 07, seventh superlattice layer; 001, first quantum well layer; 002, second quantum well layer; 003, third quantum well layer; 004, fourth quantum well layer; 005, fifth quantum well layer; 006, sixth quantum well layer; 007, seventh quantum well layer. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the present disclosure more clear, the present disclosure is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present disclosure and are not used to limit the present disclosure.

[0041] The solar cell epitaxial structure provided by the embodiment of the present disclosure is realized by arranging multiple superlattice layers and multiple quantum well layers between the n-type doped GaN layer and the p-type doped GaN layer, and the superlattice layer and the quantum well layer are arranged in sequence, so that the superlattice layer can be inserted between the multiple quantum well layers, and the superlattice layer can be used as a stress release layer. The stress between the epitaxial layer (n-type doped GaN layer) and the quantum well layer can be released by the superlattice layer, and the stress between adjacent quantum well layers can also be released by the superlattice layer. At the same time, the superlattice layer reduces the band tilt in the quantum well layer, weakens the polarization electric field in the quantum well layer, suppresses the carrier recombination, and enables more carriers to reach the cathode and anode, thereby improving the short-circuit current and promoting the photoelectric conversion efficiency. In addition, since the superlattice layer releases the stress between adjacent quantum well layers, the lattice mismatch in the quantum well layer can be reduced, thereby improving the crystal quality, which is conducive to improving the photoelectric conversion efficiency.

[0042] The following is combined with Figure 1-5 , an exemplary description is given of the solar cell epitaxial structure and the method for preparing the solar cell epitaxial structure provided in the embodiments of the present disclosure.

[0043] Figure 1 The schematic diagram of the structure of a solar cell epitaxial structure provided by the embodiment of the present disclosure is shown in FIG. Figure 1As shown, the epitaxial structure of the solar cell includes: a substrate 10; an n-type doped GaN layer 11 located on one side of the substrate 10; a superlattice quantum well structure 010 located on the side of the n-type doped GaN layer 11 away from the substrate 10, the superlattice quantum well structure 010 includes a plurality of superlattice layers 12 and a plurality of quantum well layers 13 arranged in sequence, the number of the superlattice layers 12 and the quantum well layers 13 are the same, the n-type doped GaN layer 11 is in contact with the superlattice layer 12; a p-type doped GaN layer 14, the superlattice quantum well structure 010 is located between the n-type doped GaN layer 11 and the p-type doped GaN layer 14.

[0044] The n-type doped GaN layer 11 can be regarded as an epitaxial layer formed on the substrate 10, so that the superlattice quantum well structure 010 is grown on the epitaxial layer. The n-type doped GaN layer 11 forms an electron transport layer, and the p-type doped GaN layer 14 forms a hole transport layer.

[0045] Specifically, the embodiment of the present disclosure arranges multiple superlattice layers 12 and multiple quantum well layers 13 between the n-type doped GaN layer 11 and the p-type doped GaN layer 14, and the superlattice layers 12 and the quantum well layers 13 are arranged in sequence, so that the superlattice layer 12 can be inserted between the multiple quantum well layers 13. The superlattice layer 12 can be used as a stress release layer. The superlattice layer 12 can release the stress between the epitaxial layer (n-type doped GaN layer) and the quantum well layer 13, and the superlattice layer 12 can also release the stress between adjacent quantum well layers 13. At the same time, the superlattice layer 12 reduces the energy band tilt in the quantum well layer 13, weakens the polarization electric field in the quantum well layer 13, and suppresses carrier recombination, so that more carriers can reach the cathode and the anode, improve the short-circuit current, and thus promote the photoelectric conversion efficiency.

[0046] In addition, since the superlattice layer 12 releases the stress between adjacent quantum well layers 13, the lattice mismatch in the quantum well layer 13 can be reduced, thereby improving the crystal quality, which is beneficial to improving the photoelectric conversion efficiency.

[0047] The material forming the substrate 10 may be, for example, sapphire in c-axis crystal phase (0001); the n-type doped GaN layer 11 may be doped with n-type Si, with a doping concentration of 1×10 18 cm -3 , and the p-type doped GaN layer 14 can be doped with p-type Si, with a doping concentration of 1×10 18 cm -3 .

[0048] The n-type doped GaN layer 11 may include a first doped GaN layer and a second doped GaN layer ( Figure 1Not shown in the figure, the first doped GaN layer is first grown on the substrate 10 at a low temperature, for example, 470°C, that is, a first doped GaN layer with a thickness of, for example, 40 nm is first grown on the substrate 10, and then a second doped GaN layer is grown on the first doped GaN layer at a high temperature, for example, 1000°C, so that the second doped GaN layer can be transformed from a three-dimensional material to a two-dimensional material. The thickness of the second doped GaN layer can be, for example, 3μm.

[0049] Among them, the superlattice layer 12 is composed of In x Ga 1-x N / GaN structure, quantum well layer 13 is composed of In x Ga 1-x N / GaN structural composition, please see below for details.

[0050] It should be noted that Figure 1 The figure merely shows by way of example that the superlattice quantum well structure 010 includes seven superlattice layers 12 and seven quantum well layers 13 , which does not constitute a limitation on the number of superlattice layers 12 and quantum well layers 13 in the embodiment of the present disclosure.

[0051] The solar cell epitaxial structure provided by the embodiment of the present disclosure includes: a substrate; an n-type doped GaN layer located on one side of the substrate; a superlattice quantum well structure located on the side of the n-type doped GaN layer away from the substrate, the superlattice quantum well structure includes a plurality of superlattice layers and a plurality of quantum well layers arranged in sequence, the number of superlattice layers and quantum well layers is the same, the n-type doped GaN layer is in contact with the superlattice layer; a p-type doped GaN layer, the superlattice quantum well structure is located between the n-type doped GaN layer and the p-type doped GaN layer. By arranging a plurality of superlattice layers and a plurality of quantum well layers between the n-type doped GaN layer and the p-type doped GaN layer, and the superlattice layers and the quantum well layers are arranged in sequence, it is possible to insert a superlattice layer between the plurality of quantum well layers, the superlattice layer can be used as a stress release layer, the superlattice layer can be used to release the stress between the epitaxial layer (n-type doped GaN layer) and the quantum well layer, and the superlattice layer can also be used to release the stress between adjacent quantum well layers. At the same time, the superlattice layer reduces the energy band tilt in the quantum well layer, weakens the polarization electric field in the quantum well layer, suppresses carrier recombination, and enables more carriers to reach the cathode and anode, increasing the short-circuit current and thus promoting the photoelectric conversion efficiency. In addition, since the superlattice layer releases the stress between adjacent quantum well layers, it can reduce the lattice mismatch in the quantum well layer, thereby improving the crystal quality and helping to improve the photoelectric conversion efficiency.

[0052] In some embodiments, Figure 2 A schematic diagram of another solar cell epitaxial structure provided for the implementation of the present disclosure. Figure 2 As shown, the solar cell epitaxial structure also includes:

[0053] GaN buffer layer 15 ; the GaN buffer layer 15 is located between the p-type doped GaN layer 14 and the superlattice quantum well structure 010 .

[0054] The GaN buffer layer 15 can be heavily doped with p-type Si, with a doping concentration of 5×10 19 cm -3 Thus, the GaN buffer layer 15 can be used as an electron blocking layer to block the electrons diffused from the superlattice quantum well structure 010, causing them to return to the diffusion region or the space charge region and continue to drift toward the n-type doped GaN layer 11, i.e., the n-region, under the action of the built-in electric field, thereby inhibiting the recombination of carriers on the surface of the p-type doped GaN layer 14.

[0055] Therefore, providing a GaN buffer layer 15 between the p-type doped GaN layer 14 and the superlattice quantum well structure 010 is helpful to improve the performance of the solar cell.

[0056] Exemplarily, the thickness of the GaN buffer layer 15 may be 6 nm.

[0057] In some embodiments, the superlattice layer 12 is made of In x Ga 1-x N / GaN structure formation;

[0058] In x Ga 1-x In in N / GaN structures x Ga 1-x The thickness of the N layer and the GaN layer is equal and is 5 nm.

[0059] Specifically, by setting In x Ga 1-x In in N / GaN structures x Ga 1-x The thickness of the N layer and GaN layer is equal and 5nm to achieve In x Ga 1-x The N / GaN structure forms the superlattice layer 12 .

[0060] Specifically, x Ga 1-x The thickness of the N layer and the GaN layer are equal and are determined to be 5 nm through simulation tests.

[0061] For example, Figure 3 A schematic diagram of the structure of a superlattice layer provided in an embodiment of the present disclosure. Figure 3 As shown, the superlattice layer (In x Ga 1-x N / GaN structure) including In x Ga 1-x N layer and GaN layer, Inx Ga 1-x The thickness d of the N layer and the GaN layer is equal and is 5nm, thus achieving In x Ga 1-x The N / GaN structure forms a superlattice layer.

[0062] In some embodiments, Figure 1 or Figure 2 As shown, the In in each superlattice layer 12 x Ga 1-x The In content in the N layer first increases and then decreases in a direction away from the substrate 10 .

[0063] Specifically, the superlattice layer 12 can be used as a stress release layer and at the same time as the quantum well layer 13 as a photon absorption layer. x Ga 1-x The multilayer structure has a gradually changing In content in the N layer. Different In contents lead to different bandgap widths. Materials with different bandgap widths absorb light in different wavelength ranges. Materials with different bandgap widths are used to absorb photons of wavelengths that best match their bandgap widths, thereby reducing the current loss and voltage loss of solar cells during operation, thereby improving the conversion efficiency of solar cells.

[0064] However, in the superlattice layer 12 (In x Ga 1-x In N / GaN structure, since the lattice mismatch between InGaN and GaN is greater when the In component is higher, the gradual increase and then decrease of the In component can reduce the lattice mismatch between InGaN and GaN with different In components as much as possible, thereby improving crystal quality, reducing defects and improving device performance.

[0065] For example, Figure 1 or Figure 2 As shown, the superlattice quantum well structure 010 includes a first superlattice layer 01, a second superlattice layer 02, a third superlattice layer 03, a fourth superlattice layer 04, a fifth superlattice layer 05, a sixth superlattice layer 06 and a seventh superlattice layer 07. The In component x% in the first superlattice layer 01 is 10%, the In component x% in the second superlattice layer 02 is 20%, the In component x% in the third superlattice layer 03 is 30%, the In component x% in the fourth superlattice layer 04 is 40%, the In component x% in the fifth superlattice layer 05 is 30%, the In component x% in the sixth superlattice layer 06 is 20%, and the In component x% in the seventh superlattice layer 07 is 10%.

[0066] In some embodiments, the quantum well layer is composed of In x Ga 1-xN / GaN structure composition;

[0067] In x Ga 1-x In in N / GaN structures x Ga 1-x The thickness of the N layer is 4nm, and the In x Ga 1-x The thickness of the GaN layer in the N / GaN structure is 10 nm.

[0068] Specifically, by setting In x Ga 1-x In in N / GaN structures x Ga 1-x The thickness of the N layer is 4 nm, and the In x Ga 1-x The thickness of the GaN layer in the N / GaN structure is 10nm to achieve In x Ga 1-x The N / GaN structure forms a quantum well layer.

[0069] Specifically, x Ga 1-x The thickness of the N layer is 4 nm, and the thickness of the GaN layer is set to 10 nm, which is determined through simulation tests.

[0070] For example, Figure 4 A schematic diagram of the structure of a quantum well layer provided in an embodiment of the present disclosure. Figure 4 As shown, the quantum well layer (In x Ga 1-x N / GaN structure) including In x Ga 1-x N layer and GaN layer, In x Ga 1-x The thickness d1 of the N layer is 4 nm, and the thickness d2 of the GaN layer is 10 nm, thereby achieving In x Ga 1-x The N / GaN structure forms a quantum well layer.

[0071] In some embodiments, the In in each quantum well layer x Ga 1-x The In content in the N layer first increases and then decreases in a direction away from the substrate 10 .

[0072] Specifically, the present invention provides a quantum well layer having an In x Ga 1-xIn a multilayer structure in which the In content in N varies gradually, the different In contents lead to different bandgap widths, and materials with different bandgap widths absorb light in different wavelength ranges. Materials with different bandgap widths are used to absorb photons of wavelengths that best match their bandgap widths, thereby reducing the current loss and voltage loss of solar cells during operation, thereby improving the conversion efficiency of solar cells.

[0073] In the quantum well layer, since the lattice mismatch between InGaN and GaN is greater when the In content is higher, the gradual increase and then decrease of the In content can minimize the lattice mismatch between InGaN and GaN with different In contents, thereby improving crystal quality, reducing defects and improving device performance.

[0074] For example, Figure 1 or Figure 2 As shown, the superlattice quantum well structure 010 includes a first quantum well layer 001, a second quantum well layer 002, a third quantum well layer 003, a fourth quantum well layer 004, a fifth quantum well layer 005, a sixth quantum well layer 006 and a seventh quantum well layer 007. The In component x% in the first quantum well layer 001 is 10%, the In component x% in the second quantum well layer 002 is 20%, the In component x% in the third quantum well layer 003 is 30%, the In component x% in the fourth quantum well layer 004 is 40%, the In component x% in the fifth quantum well layer 005 is 30%, the In component x% in the sixth quantum well layer 006 is 20%, and the In component x% in the seventh quantum well layer 007 is 10%.

[0075] In some embodiments, the solar cell epitaxial structure further comprises:

[0076] An n-type electrode 16 and a p-type electrode 17;

[0077] The n-type electrode 16 is provided on the n-type doped GaN layer 11 , and the p-type electrode 17 is provided on the p-type doped GaN layer 14 .

[0078] Specifically, an n-type electrode 16 is disposed on the n-type doped GaN layer 11, and a p-type electrode 17 is disposed on the p-type doped GaN layer 14. Thus, electrons can be transferred from the n-type doped GaN layer 11 to the n-type electrode 16, and holes can be transferred from the p-type doped GaN layer 14 to the p-type electrode 17.

[0079] The epitaxial structure of the solar cell provided in the embodiment of the present disclosure proposes a multilayer structure in which the In content in the InGaN in the quantum well layer and the lattice layer gradually changes. The difference in In content leads to different bandgap widths, and materials with different bandgap widths absorb light in different wavelength ranges. Materials with different bandgap widths are used to absorb photons of wavelengths that best match their bandgap widths, thereby reducing the current loss and voltage loss of the solar cell during operation, thereby improving the conversion efficiency of the solar cell.

[0080] By inserting the superlattice layer 12 between multiple quantum well layers, the stress between adjacent quantum well layers can be released, the lattice mismatch can be reduced, and the crystal quality can be improved. At the same time, the superlattice layer 12 reduces the energy band tilt in the quantum well, weakens the polarization electric field in the quantum well, suppresses carrier recombination, and enables more carriers to reach the cathode and anode, thereby increasing the short-circuit current and promoting the improvement of photoelectric conversion efficiency.

[0081] In addition, the present disclosure also proposes a structure in which the In component of the InGaN layer in the quantum well layer and the lattice layer increases from low to high and then to low again from the bottom layer to the top layer. Since the higher the In component, the greater the lattice mismatch between InGaN and GaN, the gradual increase and then decrease of the In component can minimize the lattice mismatch between InGaN and GaN with different In components, improve the crystal quality, reduce defects, and improve device performance.

[0082] Based on the above embodiments, the present disclosure also provides a method for preparing an epitaxial structure of a solar cell. Figure 5 The present invention provides a schematic flow chart of a method for preparing a solar cell epitaxial structure according to an embodiment of the present invention. Figure 5 As shown, the method for preparing the epitaxial structure of a solar cell comprises the following steps:

[0083] S501, providing a substrate.

[0084] S502 , forming an n-type doped GaN layer on one side of the substrate.

[0085] S503. Form a superlattice quantum well structure on a side of the n-type doped GaN layer away from the substrate. The superlattice quantum well structure includes a plurality of superlattice layers and a plurality of quantum well layers arranged in sequence at intervals. The number of the superlattice layers and the quantum well layers is the same. The n-type doped GaN layer is in contact with the superlattice layer.

[0086] S504 , forming a p-type doped GaN layer on a side of the superlattice quantum well structure away from the n-type doped GaN layer.

[0087] Specifically, Figure 1As shown, a substrate 10 is first provided; next, an n-type doped GaN layer 11 is formed on one side of the substrate 10; next, a superlattice quantum well structure 010 is formed on the side of the n-type doped GaN layer 11 away from the substrate 10; next, a p-type doped GaN layer 14 is formed on the side of the superlattice quantum well structure 010 away from the n-type doped GaN layer 11.

[0088] The superlattice quantum well structure 010 includes a plurality of superlattice layers 12 and a plurality of quantum well layers 13 which are arranged in sequence and at intervals. The number of the superlattice layers 12 and the number of the quantum well layers 13 are the same. The n-type doped GaN layer 11 is in contact with the superlattice layer 12 .

[0089] Thus, by arranging multiple superlattice layers 12 and multiple quantum well layers 13 between the n-type doped GaN layer 11 and the p-type doped GaN layer 14, and the superlattice layers 12 and the quantum well layers 13 are arranged in sequence, it is possible to insert the superlattice layer 12 between the multiple quantum well layers 13, and the superlattice layer 12 can be used as a stress release layer. The superlattice layer 12 can release the stress between the epitaxial layer (n-type doped GaN layer) and the quantum well layer 13, and the superlattice layer 12 can also release the stress between adjacent quantum well layers 13. At the same time, the superlattice layer 12 reduces the energy band tilt in the quantum well layer, weakens the polarization electric field in the quantum well layer, and suppresses carrier recombination, so that more carriers can reach the cathode and the anode, increasing the short-circuit current and thus promoting the improvement of the photoelectric conversion efficiency.

[0090] In addition, since the superlattice layer 12 releases the stress between adjacent quantum well layers, the lattice mismatch in the quantum well layer can be reduced, thereby improving the crystal quality, which is beneficial to improving the photoelectric conversion efficiency.

[0091] In some embodiments, before forming the p-type doped GaN layer on the side of the superlattice quantum well structure away from the n-type doped GaN layer, the method further includes:

[0092] A GaN buffer layer is formed on one side of the superlattice quantum well structure. The GaN buffer layer 15 is located between the superlattice quantum well structure and the p-type doped GaN.

[0093] Specifically, the GaN buffer layer 15 can be used as an electron blocking layer, which can hinder the electrons diffused from the superlattice quantum well structure 010, causing them to return to the diffusion region or the space charge region, and continue to drift toward the n-type doped GaN layer 11, i.e., the n-region, under the action of the built-in electric field, thereby inhibiting the recombination of carriers on the surface of the p-type doped GaN layer 14.

[0094] Therefore, providing a GaN buffer layer 15 between the p-type doped GaN layer 14 and the superlattice quantum well structure 010 is helpful to improve the performance of the solar cell.

[0095] In some embodiments, after forming a p-type doped GaN layer on a side of the superlattice quantum well structure away from the n-type doped GaN layer, the method further includes:

[0096] An n-type electrode 16 is formed on the n-type doped GaN layer 11, and a p-type electrode 17 is formed on the p-type doped GaN layer 14. Thus, electrons can be transferred from the n-type doped GaN layer 11 to the n-type electrode, and holes can be transferred from the p-type doped GaN layer to the p-type electrode.

[0097] Exemplarily, the present disclosure provides a method for preparing an epitaxial structure of a solar cell with specific detailed steps as follows:

[0098] Step 1: Take a substrate, the material of which is sapphire. Clean the substrate in concentrated sulfuric acid for 5 minutes, then perform a high temperature cleaning treatment at 1000-1200°C in a hydrogen atmosphere for 10 minutes, and finally treat the substrate in an ammonia atmosphere for 5 minutes.

[0099] Step 2: Growing an n-type doped GaN layer on the substrate.

[0100] Step 3: Growing the first superlattice layer (In 0.1 Ga 0.9 N / GaN), In 0.1 Ga 0.9 The thickness of the N layer is 5 nm, the thickness of the GaN layer is 5 nm, and the growth temperature is 800°C.

[0101] Step 4: Growing the first quantum well layer (In 0.1 Ga 0.9 N / GaN), In 0.1 Ga 0.9 The thickness of the N layer is 4nm, the thickness of the GaN layer is 10nm, and the growth temperature is 800℃.

[0102] Step 5: Grow the second superlattice layer (In 0.2 Ga 0.8 N / GaN), In 0.2 Ga 0.8 The thickness of the N layer is 5 nm, the thickness of the GaN layer is 5 nm, and the growth temperature is 800°C.

[0103] Step 6: Growing a second quantum well layer (In 0.2 Ga 0.8 N / GaN), In 0.2 Ga 0.8 The thickness of the N layer is 4nm, the thickness of the GaN layer is 10nm, and the growth temperature is 800℃.

[0104] Step 7: Growing the third superlattice layer (In 0.3 Ga 0.7 N / GaN), In 0.3 Ga 0.7 The thickness of the N layer is 5 nm, the thickness of the GaN layer is 5 nm, and the growth temperature is 800°C.

[0105] Step 8: Growing a third quantum well layer (In 0.3 Ga 0.7 N / GaN), In 0.3 Ga 0.7 The thickness of the N layer is 4nm, the thickness of the GaN layer is 10nm, and the growth temperature is 800℃.

[0106] Step 9: Growing the fourth superlattice layer (In 0.4 Ga 0.6 N / GaN), In 0.4 Ga 0.6 The thickness of the N layer is 5 nm, the thickness of the GaN layer is 5 nm, and the growth temperature is 800°C.

[0107] Step 10: Growing a fourth quantum well layer (In 0.4 Ga 0.6 N / GaN), In 0.4 Ga 0.6 The thickness of the N layer is 4nm, the thickness of the GaN layer is 10nm, and the growth temperature is 800℃.

[0108] Step 11: Growing the fifth superlattice layer (In 0.3 Ga 0.7 N / GaN), In 0.3 Ga 0.7 The thickness of the N layer is 5 nm, the thickness of the GaN layer is 5 nm, and the growth temperature is 800°C.

[0109] Step 12: Growing a fifth quantum well layer (In 0.3 Ga 0.7 N / GaN), In 0.3 Ga 0.7 The thickness of the N layer is 4nm, the thickness of the GaN layer is 10nm, and the growth temperature is 800℃.

[0110] Step 13: Growing the sixth superlattice layer (In 0.2 Ga 0.8 N / GaN), In 0.2 Ga 0.8The thickness of the N layer is 5 nm, the thickness of the GaN layer is 5 nm, and the growth temperature is 800°C.

[0111] Step 14: Growing a sixth quantum well layer (In 0.2 Ga 0.8 N / GaN), In 0.2 Ga 0.8 The thickness of the N layer is 4nm, the thickness of the GaN layer is 10nm, and the growth temperature is 800℃.

[0112] Step 15: Growing the seventh superlattice layer (In 0.1 Ga 0.9 N / GaN), In 0.1 Ga 0.9 The thickness of the N layer is 5 nm, the thickness of the GaN layer is 5 nm, and the growth temperature is 800°C.

[0113] Step 16: Growing the seventh quantum well layer (In 0.1 Ga 0.9 N / GaN), In 0.1 Ga 0.9 The thickness of the N layer is 4nm, the thickness of the GaN layer is 10nm, and the growth temperature is 800℃.

[0114] Step 17: Grow a GaN buffer layer on the seventh quantum well layer at a growth temperature of 850° C. and a thickness of 6 nm.

[0115] Step 18: Grow a p-type doped GaN layer on the GaN buffer layer at a growth temperature of 850° C. with a thickness of 6 nm.

[0116] Step 19: Lower the temperature of the reaction chamber to below 800°C, anneal for 10 minutes in a nitrogen atmosphere, and then lower it to room temperature to complete the growth.

[0117] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0118] The above embodiments only express several implementation methods of the present disclosure, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present disclosure, and these all belong to the protection scope of the present disclosure. Therefore, the protection scope of the patent of the present disclosure shall be subject to the attached claims.

Claims

1. A solar cell epitaxial structure, characterized in that: include: substrate; an n-type doped GaN layer located on one side of the substrate; a superlattice quantum well structure located on a side of the n-type doped GaN layer away from the substrate, the superlattice quantum well structure comprising a plurality of superlattice layers and a plurality of quantum well layers arranged in sequence and spaced apart from each other, the number of the superlattice layers and the number of the quantum well layers being the same, and the n-type doped GaN layer being in contact with the superlattice layer; The p-type doped GaN layer, the superlattice quantum well structure is located between the n-type doped GaN layer and the p-type doped GaN layer.

2. The solar cell epitaxial structure according to claim 1, characterized in that: Also includes: GaN buffer layer; The GaN buffer layer is located between the p-type doped GaN and the superlattice quantum well structure.

3. The solar cell epitaxial structure according to claim 1, characterized in that: The superlattice layer is composed of In x Ga 1-x N / GaN structure composition; In x Ga 1-x In in N / GaN structures x Ga 1-x The thickness of the N layer and the GaN layer is equal and is 5 nm.

4. The solar cell epitaxial structure according to claim 3, characterized in that: In each of the superlattice layers x Ga 1-x The In content in the N layer first increases and then decreases in a direction away from the substrate.

5. The solar cell epitaxial structure according to claim 1, characterized in that: The quantum well layer is composed of In x Ga 1-x N / GaN structure composition; In x Ga 1-x In in N / GaN structures x Ga 1-x The thickness of the N layer is 4 nm. x Ga 1-x The thickness of the GaN layer in the N / GaN structure is 10 nm.

6. The solar cell epitaxial structure according to claim 5, characterized in that: In each of the quantum well layers x Ga 1-x The In content in the N layer first increases and then decreases in a direction away from the substrate.

7. The solar cell epitaxial structure according to claim 1, characterized in that: Also includes: n-type electrode and p-type electrode; The n-type electrode is disposed on the n-type doped GaN layer, and the p-type electrode is disposed on the p-type doped GaN layer.

8. A method for preparing an epitaxial structure of a solar cell, characterized in that: include: providing a substrate; forming an n-type doped GaN layer on one side of the substrate; A superlattice quantum well structure is formed on a side of the n-type doped GaN layer away from the substrate, wherein the superlattice quantum well structure comprises a plurality of superlattice layers and a plurality of quantum well layers which are sequentially spaced apart, the number of the superlattice layers and the number of the quantum well layers are the same, and the n-type doped GaN layer is in contact with the superlattice layer; A p-type doped GaN layer is formed on a side of the superlattice quantum well structure away from the n-type doped GaN layer.

9. The method for preparing a solar cell epitaxial structure according to claim 8, characterized in that: Before forming a p-type doped GaN layer on a side of the superlattice quantum well structure away from the n-type doped GaN layer, the method further comprises: A GaN buffer layer is formed on one side of the superlattice quantum well structure, and the GaN buffer layer is located between the superlattice quantum well structure and the p-type doped GaN.

10. The method for preparing a solar cell epitaxial structure according to claim 8, characterized in that: After forming a p-type doped GaN layer on a side of the superlattice quantum well structure away from the n-type doped GaN layer, the method further comprises: An n-type electrode is formed on the n-type doped GaN layer, and a p-type electrode is formed on the p-type doped GaN layer.

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