Preparation Method of InP Nanopillar Radial Homojunction Array Structure and Solar Cell

Abstract

The present invention discloses a preparation method of a radial homojunction array structure of indium phosphide nanocolumns, comprising the following steps: cleaning and drying a p-type InP single crystal wafer; fabricating a nanocolumn array on the surface of the p-type InP single crystal wafer and cleaning it with an acid; wrapping an oxide layer on the side surface of the nanocolumn array and plating a transparent conductive layer. During the preparation process of the method involved in the present invention, the preparation of both indium phosphide nanocolumn arrays and radial homojunctions is achieved simultaneously. By controlling the etching time and the content of H2, the surface doping concentration and depth of indium phosphide are precisely controlled. Compared with other methods for growing radial homojunctions, the method of the present invention has simple equipment and high preparation efficiency. The present invention also provides a solar cell, and the solar cell provided by the present invention has a high solar light absorption rate and conversion efficiency.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor technology, and particularly relates to a preparation method of an InP nanocolumn radial homojunction array structure and a solar cell. Background Art

[0002] With the development of the global economy and the growth of the population, the pollution problem caused by fossil energy is becoming increasingly serious, and people begin to explore alternative solutions to traditional energy. Solar energy is the most abundant and easily accessible renewable energy on the earth, and a solar cell is a semiconductor device that directly uses solar energy to generate electricity through the photovoltaic conversion effect. However, the low energy conversion efficiency and high cost of solar cells have become two major problems restricting their development. At present, silicon-based solar cells dominate the solar cell market. The conversion efficiency of single-crystalline silicon cells can reach about 25%, but they require a relatively large amount of single-crystalline silicon materials and have high production costs. For polycrystalline silicon, due to many defects, the conversion efficiency is relatively low. The III-V materials have high conversion efficiency, but the material and production costs remain high, making it difficult to promote their use. Therefore, nanocolumn arrays are used to improve the light confinement ability and reduce the material cost. However, due to the large surface area of the nanocolumn structure, the large surface recombination of carriers seriously affects the performance of the device. To overcome this problem, surface passivation technology or nanocolumn radial junction structures are proposed to reduce surface recombination and improve the efficiency of solar cells. However, generally, preparing nanocolumn radial junctions requires precise control of the doping concentration at a very small size (within 200 nm), and it is easy to introduce additional surface defects, and the efficiency of nanocolumn solar cells is not very high. Therefore, it is necessary to propose a simple method for preparing nanocolumn radial homojunction structures to achieve high-efficiency and low-cost production of solar cells. Summary of the Invention

[0003] Aiming at the technical problems existing in the prior art that the doping concentration is difficult to control and additional surface defects are easily introduced during the preparation of nanocolumn radial junctions, the purpose of the present invention is to provide a preparation method of an InP nanocolumn radial homojunction array structure and a solar cell.

[0004] To achieve the above object, the present invention provides a preparation method of an indium phosphide (InP) nanocolumn radial homojunction array structure, comprising the following steps:

[0005] (1) Cleaning and drying a p-type indium phosphide single crystal wafer;

[0006] (2) Fabricating a nanocolumn array mask pattern on one surface of the p-type indium phosphide single crystal wafer;

[0007] (3) Use an inductively coupled plasma etcher to etch the surface with the nanocolumn array mask pattern in CH4 and H2 plasmas to obtain an indium phosphide nanocolumn radial homojunction. The indium phosphide nanocolumn radial homojunctions form an indium phosphide nanocolumn radial homojunction array, and wash the indium phosphide nanocolumn radial homojunction array in piranha solution;

[0008] (4) Deposit an oxide layer on the surface of the indium phosphide nanocolumn radial homojunction array, and etch away the oxide layer covering the sides other than the sides of the indium phosphide nanocolumn radial homojunction. Then deposit a transparent conductive layer on the indium phosphide nanocolumn radial homojunction array.

[0009] Among them, in step (2), according to the size of the nanocolumns, select to use ultraviolet exposure technology, electron beam exposure technology or polystyrene self-assembly technology to fabricate a nanocolumn array mask pattern on one surface of the p-type indium phosphide single crystal wafer, so that the part to be etched is exposed and the part that does not need to be etched is blocked.

[0010] In step (3), the length of the indium phosphide nanocolumns is positively correlated with the etching time. In addition, the function of washing with piranha solution is to remove organic substances on the material surface and In particles generated during the etching process, etc.

[0011] In step (4), a chemical vapor deposition system or an atomic layer deposition system is used for depositing the oxide layer, and a magnetron sputtering machine is used for depositing the transparent conductive layer. The transparent conductive layer is used as a conductive layer on the one hand and as an antireflection layer on the other hand.

[0012] In the preparation process of the indium phosphide nanocolumn radial homojunction array structure of the present invention, the preparation of the indium phosphide nanocolumn array and the radial homojunction is realized simultaneously. By controlling the etching time and the H2 content, the doping concentration and depth on the indium phosphide surface can be precisely controlled.

[0013] Further, the total gas pressure of the plasma is 5 - 20 mTorr, the volume flow rate of CH4 is 20 - 40 sccm, and the volume flow rate of H2 is 0 - 40 sccm.

[0014] Further, use the plasma containing H2 to etch the p-type indium phosphide single crystal wafer to obtain a lightly doped p-type indium phosphide layer or an n-type indium phosphide layer on the surface of the p-type indium phosphide single crystal wafer.

[0015] On the one hand, H2 in the etching gas can passivate the surface of indium phosphide (InP), and on the other hand, it can modify the surface of indium phosphide.

[0016] Further, the length of the indium phosphide nanocolumn radial homojunction is 800 - 1200 nm.

[0017] The length of the radial homojunction of indium phosphide nanowires is related to the etching time. The longer the etching time is, the greater the length of the radial homojunction of indium phosphide nanowires will be.

[0018] Furthermore, the thickness of the oxide layer is 10 - 40 nm.

[0019] Furthermore, the oxide layer is SiO2 or Al2O3.

[0020] The oxide layer is SiO2 or Al2O3, but is not limited to SiO2 or Al2O3. In addition, the oxide layer is used as an oxide layer on one hand and as an insulating layer on the other hand.

[0021] Furthermore, the thickness of the transparent conductive layer is 100 - 200 nm.

[0022] The present invention also provides a solar cell, which includes a radial homojunction array structure of indium phosphide nanowires.

[0023] Furthermore, the solar cell also includes a metal electrode and an interdigitated electrode. The interdigitated electrode is disposed on the transparent conductive layer of the radial homojunction array structure of indium phosphide nanowires, and the metal electrode is disposed on the other surface of the p-type indium phosphide single crystal wafer opposite to the indium phosphide nanowire array.

[0024] The solar cell of the present invention includes a radial homojunction array structure of indium phosphide nanowires, which reduces reflection and increases efficiency of the solar cell. Among them, the surface of the radial homojunction of indium phosphide nanowires contains an additional oxide layer, which passivates the surface of the radial homojunction of indium phosphide nanowires, and a high-efficiency solar cell can be realized.

[0025] Compared with the prior art, the technical effects of the present invention are as follows: In the preparation process of the method for preparing the radial homojunction array structure of indium phosphide nanowires according to the present invention, the preparation of the indium phosphide nanowire array and the radial homojunction is realized simultaneously. By controlling the etching time and the content of H2, the surface doping concentration and depth of indium phosphide are accurately controlled. Compared with other methods for growing radial homojunctions, this method has simple equipment and high preparation efficiency. The present invention also provides a solar cell, and the solar cell provided by the present invention has a high sunlight absorption rate and conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0027] Figure 1 is a flowchart of the preparation method of the present invention;

[0028] Figure 2 Schematic structural diagram of indium phosphide nanocolumns prepared according to the present invention;

[0029] Figure 3 Variation of the surface doping concentration of an indium phosphide single crystal wafer with the etching depth;

[0030] Figure 4 Mask pattern of the nanocolumn array;

[0031] Figure 5 Schematic partial structural diagram of a radial homojunction nanocolumn array solar cell;

[0032] Figure 6 External quantum efficiency and solar light absorption rate diagram of the radial homojunction nanocolumn array solar cell. Specific embodiments

[0033] The following details the embodiments of the present invention. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0034] The following describes a method for preparing a radial homojunction of indium phosphide nanocolumns according to an embodiment of the present invention with reference to the drawings.

[0035] As Figure 1 shown, the method for preparing the radial homojunction array structure of indium phosphide nanocolumns includes the following steps:

[0036] (1) Clean and dry a p-type InP single crystal wafer;

[0037] (2) Fabricate a nanocolumn array on the surface of the p-type InP single crystal wafer and clean it with acid;

[0038] (3) Wrap an oxide layer on the side of the nanocolumn array and deposit a transparent conductive layer.

[0039] The specific operation process of step (1) is as follows: ultrasonically clean the p-type InP single crystal wafer with acetone, alcohol, and distilled water respectively, and dry it with nitrogen, where the purity of nitrogen is 99.9%.

[0040] The specific operation process of fabricating a nanocolumn array on the surface of the p-type InP single crystal wafer and cleaning it with acid in step (2) is as follows.

[0041] First, according to the size of the nanocolumns, select to use ultraviolet exposure technology, electron beam exposure technology or polystyrene self-assembly technology to fabricate a nanocolumn array mask pattern on one surface of a p-type indium phosphide single crystal wafer, so that the part to be etched is exposed and the part that does not need to be etched is blocked. The nanocolumn array mask pattern can be arranged in a square or triangular lattice, or other suitable arrangements. In this embodiment, the nanocolumn array mask pattern is taken as an example of a square, as Figure 4 shown, where the circular part is the part to be etched, and the other parts except the circular part are the parts to be blocked.

[0042] Then, use an inductively coupled plasma etcher to etch the surface with the nanocolumn array mask pattern in CH4 and H2 plasmas to obtain indium phosphide nanocolumn radial homojunctions, and the indium phosphide nanocolumn radial homojunctions form an indium phosphide nanocolumn radial homojunction array. The total gas pressure of the plasma is 5 - 20 mTorr, the volume flow rate of CH4 is 20 - 40 sccm, the volume flow rate of H2 is 0 - 40 sccm, and the length of the indium phosphide nanocolumn radial homojunction is 800 - 1200 nm. Among them, the length of the indium phosphide nanocolumn radial homojunction is positively correlated with the etching time, that is, the longer the etching time, the greater the length of the indium phosphide nanocolumn radial homojunction. In addition, the shape of the nanocolumns is related to the etching gas ratio, power and total gas pressure, and the shape and length of the nanocolumns have a certain impact on the light reflectivity. Using a plasma containing H2 to etch the p-type indium phosphide single crystal wafer, a low-doped p-type indium phosphide layer or an n-type indium phosphide layer is obtained on the surface of the p-type indium phosphide single crystal wafer, and a homojunction is formed between the p-type indium phosphide and the low-doped p-type indium phosphide or a homojunction is formed between the p-type indium phosphide and the n-type indium phosphide. That is to say, on the one hand, H2 in the etching gas can passivate the surface of indium phosphide (InP), and on the other hand, it can modify the surface of indium phosphide. It can be understood that by controlling the etching time and the content of H2, the doping concentration and depth on the surface of indium phosphide can be precisely controlled, and a homojunction structure can be formed on the surface of indium phosphide. In addition, the doped substance in this embodiment is Zn. Figure 3 is the change of the doping concentration on the surface of the indium phosphide single crystal wafer with the etching depth. The distance from the surface depth is the etching depth, and the etching depth of 0 represents the substrate surface, that is, the surface of the indium phosphide single crystal. It can be seen from the figure that as the etching depth increases, the doping concentration shows a trend of first increasing rapidly and then gradually stabilizing.

[0043] Finally, put the indium phosphide nanocolumn radial homojunction array into piranha solution for cleaning. Among them, the cleaning time is 10 - 30 s, and the piranha solution is a mixture of 98% concentrated sulfuric acid, 30% hydrogen peroxide and deionized water, and the volume ratio of 98% concentrated sulfuric acid, 30% hydrogen peroxide and deionized water is 3:1:1.

[0044] In step (3), the specific operation process of coating an oxide layer on the side of the radial homojunction array of indium phosphide nanocolumns and depositing a transparent conductive layer is as follows: Use a chemical vapor deposition system or an atomic layer deposition system to deposit an oxide layer on the surface of the radial homojunction array of indium phosphide nanocolumns, and etch away the oxide layer wrapped on the sides other than the sides of the radial homojunction of indium phosphide nanocolumns. Then, use a magnetron sputtering machine to deposit a transparent conductive layer on the radial homojunction array of indium phosphide nanocolumns, and finally obtain the structure of the radial homojunction array of indium phosphide nanocolumns. The oxide layer is SiO2 or Al2O3, the thickness of the oxide layer is 10 - 40 nm, and the thickness of the transparent conductive layer is 100 - 200 nm.

[0045] The radial homojunction structure of indium phosphide nanocolumns prepared by the above method is as Figure 2 shown, from the inside out are p-type InP, n-type InP or low-doped p-type InP, oxide layer, and transparent conductive layer.

[0046] The present invention also provides a solar cell, including a radial homojunction array structure of indium phosphide nanocolumns. The solar cell further includes a metal electrode and an interdigitated electrode. The interdigitated electrode is disposed on the transparent conductive layer of the radial homojunction array structure of indium phosphide nanocolumns, and the metal electrode is disposed on the other surface of the p-type indium phosphide single crystal wafer opposite to the radial homojunction array of indium phosphide nanocolumns.

[0047] For example, if the metal electrode is Zn / Au, the interdigitated electrode is Ag, and the solar cell is prepared by using the radial homojunction array structure of indium phosphide nanocolumns prepared by the above method, Figure 5 it is a partial structure of the prepared solar cell; Figure 6 is the external quantum efficiency and solar light absorption rate diagram of the prepared solar cell. It can be seen from Figure 6 it that the prepared solar cell has an external quantum efficiency of more than 80% in the wavelength range of about 520 nm to 900 nm, and reaches the highest external quantum efficiency of 90% near the wavelength of 740 nm. It can be known that the solar cell provided by the present invention has a high solar light absorption rate and conversion efficiency.

[0048] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, without conflict, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0049] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0050] Although embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A preparation method of an indium phosphide nanocolumn radial homojunction array structure, characterized in that Including the following steps: (1) Clean and dry the p-type indium phosphide single crystal wafer; (2) Fabricate a nano-column array mask pattern on one surface of the p-type indium phosphide single crystal wafer; (3) Use an inductively coupled plasma etching machine to etch the surface with the nano-column array mask pattern in CH4 and H2 plasmas to obtain an indium phosphide nano-column radial homojunction. The indium phosphide nano-column radial homojunctions form an indium phosphide nano-column radial homojunction array, and wash the indium phosphide nano-column radial homojunction array in piranha solution; (4) Deposit an oxide layer on the surface of the indium phosphide nano-column radial homojunction array. The oxide layer is SiO2 or Al2O3, and etch away the oxide layer except for the side surfaces wrapping the indium phosphide nano-column radial homojunctions. Then deposit a transparent conductive layer on the indium phosphide nano-column radial homojunction array; Etch the p-type indium phosphide single crystal wafer with a plasma containing the H2 to obtain a lightly doped p-type indium phosphide layer or an n-type indium phosphide layer on the surface of the p-type indium phosphide single crystal wafer.

2. The method according to claim 1, characterized in that, The total gas pressure of the plasma is 5 - 20 mTorr, the volume flow rate of the CH4 is 20 - 40 sccm, and the volume flow rate of the H2 is 0 - 40 sccm.

3. The method according to claim 1, characterized in that, The length of the indium phosphide nano-column radial homojunction is 800 - 1200 nm.

4. The method according to claim 1, wherein The thickness of the oxide layer is 10 - 40 nm.

5. The method according to claim 1, wherein The thickness of the transparent conductive layer is 100 - 200 nm.

6. A solar cell includes an indium phosphide nanocolumn radial homojunction array structure, characterized in that, The indium phosphide nano-column radial homojunction array structure is prepared by the method according to any one of claims 1 - 5.

7. A solar cell according to claim 6, characterized in that, It further includes a metal electrode and an interdigital electrode. The interdigital electrode is disposed on the transparent conductive layer of the indium phosphide nano-column radial homojunction array structure, and the metal electrode is disposed on the other surface of the p-type indium phosphide single crystal wafer opposite to the indium phosphide nano-column radial homojunction array.

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