Optical coating structure of multi-junction solar cell

Abstract

The utility model relates to the technical field of semiconductor thin films, and discloses an optical coating structure of a multi-junction solar cell, which comprises a solar cell chip, an antireflection film connected to the solar cell chip and a fourth material layer connected to the antireflection film, the antireflection film comprises at least one first material layer, at least one second material layer and at least one third material layer which are sequentially stacked on the solar cell chip; wherein the fourth material layer comprises a submicron grating and a grating pattern groove, and the submicron grating is connected to the side, away from the second material layer, of the third material layer; and the grating pattern groove is connected and communicated to the third material layer through one side, deviating from the third material layer, of the submicron grating on the submicron grating. According to the multi-junction solar cell, the photoelectric conversion efficiency of the multi-junction solar cell is improved, and the sunlight reflectivity of the multi-junction solar cell is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor thin films, in particular to an optical coating structure of a multi-junction solar cell. BACKGROUND

[0002] A solar cell is a device for converting solar energy into electrical energy, and its working process depends on the effective absorption of sunlight. When sunlight shines on the surface of a solar cell, due to the difference in refractive index between the solar cell material (such as silicon, gallium arsenide, etc.) and the surrounding medium (usually air), a reflection phenomenon occurs at the interface. Without taking anti-reflection measures, the reflection loss in the visible light band can reach about 30%-40%, and this part of the reflected light cannot be absorbed and utilized by the cell, thereby greatly reducing the photoelectric conversion efficiency of the solar cell. For a multi-junction solar cell, each junction has a different wavelength of absorbed light spectrum, and more precise thin film regulation is needed to achieve maximum light loss.

[0003] Traditional multi-junction solar cells cannot balance the current density of each junction of the multi-junction cell, resulting in greater loss in a certain junction, especially in the case of more detailed spectral division and long spectral range of the multi-junction cell, and the anti-reflection film of the traditional multi-junction solar cell is extremely complex to operate and cannot accurately control the optical thickness of each film layer, nor can it obtain uniform film layers, and the refractive index cannot be guaranteed. This situation needs to be changed. CONTENT OF THE INVENTION

[0004] In view of this, the present application provides an optical coating structure of a multi-junction solar cell to solve the above-mentioned technical problems.

[0005] To achieve the above purpose, the technical scheme adopted is:

[0006] An optical coating structure of a multi-junction solar cell, comprising:

[0007] a solar cell chip, an anti-reflection film connected to the solar cell chip, and a fourth material layer connected to the anti-reflection film;

[0008] The anti-reflection film comprises at least one first material layer, at least one second material layer, and at least one third material layer stacked in sequence on the solar cell chip;

[0009] The fourth material layer comprises a sub-micron grating and a grating pattern groove, the sub-micron grating is connected to one side of the third material layer away from the second material layer, and the grating pattern groove is connected to the third material layer from the side of the sub-micron grating away from the third material layer and is in communication with the third material layer.

[0010] The application is further configured that the solar cell chip comprises a semiconductor substrate and an epitaxial layer grown on the semiconductor substrate, and a cell electrode is arranged on the epitaxial layer.

[0011] The application is further configured that the first material layer comprises a TiOx material layer, and the first material layer has a first refractive index and a first optical thickness, the first refractive index comprises 2.24, and the first optical thickness comprises 50-100 nm.

[0012] The application is further configured that the second material layer comprises an AlOx material layer, and the second material layer has a second refractive index and a second optical thickness, the second refractive index comprises 1.95, and the second optical thickness is less than 50 nm.

[0013] The application is further configured that the third material layer comprises a SiO2 material layer, and the third material layer has a third refractive index and a third optical thickness, the third refractive index comprises 1.46, and the third optical thickness comprises 50-100 nm.

[0014] The application is further configured that the fourth material layer comprises a MgF2 material layer, and the fourth material layer has a fourth refractive index and a fourth optical thickness, the fourth refractive index comprises 1.28, and the fourth optical thickness comprises 30 nm.

[0015] The application is further configured that the fourth optical thickness is the same as the thickness of the sub-micron grating and the groove depth of the grating pattern groove.

[0016] The application is further configured that the fourth material layer comprises an aluminum-doped zinc oxide material layer or a combination of organic polymer and inorganic nanoparticle material layer.

[0017] The application is further configured that the solar light wavelength range of the multi-junction solar cell comprises 300-1350 nm.

[0018] The application is further configured that the solar light reflectivity of the multi-junction solar cell is less than 3%.

[0019] Compared with the prior art, the optical coating structure of the multi-junction solar cell disclosed by the application comprises a solar cell chip, an anti-reflection film connected to the solar cell chip, and a fourth material layer connected to the anti-reflection film, wherein the anti-reflection film comprises at least one first material layer, at least one second material layer, and at least one third material layer stacked in sequence on the solar cell chip, the fourth material layer comprises a sub-micron grating and a grating pattern groove, the sub-micron grating is connected to a side of the third material layer away from the second material layer, and the grating pattern groove is connected to the third material layer from a side of the sub-micron grating away from the third material layer and is communicated to the third material layer, that is, through the above arrangement, the multi-junction solar cell has a low refractive index, and the photoelectric conversion efficiency of the multi-junction solar cell is improved. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0021] Figure 1 is a flowchart of a preparation method of the optical coating structure of the multi-junction solar cell of the application;

[0022] Figure 2 is a structural schematic diagram of the first optical coating structure of the multi-junction solar cell of the application in a preparation process;

[0023] Figure 3 is a structural schematic diagram of the second optical coating structure of the multi-junction solar cell of the application in a preparation process;

[0024] Figure 4 is a structural schematic diagram of the third optical coating structure of the multi-junction solar cell of the application in a preparation process;

[0025] Figure 5 is a structural schematic diagram of the fourth optical coating structure of the multi-junction solar cell of the application in a preparation process;

[0026] Figure 6 is a structural schematic diagram of the fifth optical coating structure of the multi-junction solar cell of the application in a preparation process. DETAILED DESCRIPTION

[0027] The exemplary embodiments will be described in detail herein with reference to the attached drawings. In the following description, like reference numerals refer to like elements throughout the description. The following exemplary embodiments are not representative of all embodiments consistent with the present application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the present application as detailed in the appended claims.

[0028] It is to be understood that the terms "including", "comprising", "consisting" and their conjugates, as used herein, are meant to be inclusive and not exclusive, i.e., unless otherwise noted, the process, method, article, or apparatus that includes a series of elements is not limited to those who include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. Unless otherwise defined, the elements defined by the statement "comprising a..." do not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element. In addition, components, features, elements with the same name in different embodiments of the present application can have the same meaning or different meanings, and the specific meaning thereof should be determined in the light of the explanation thereof in the specific embodiment or further in the light of the context in the specific embodiment.

[0029] It is to be understood that the specific embodiments described herein are merely illustrative of the present application and do not limit the present application.

[0030] In the following description, the suffixes "module", "part" or "unit" used for an element are merely intended for facilitating the description of the present application, and are not intended to limit the present application. Therefore, "module", "part" or "unit" can be mixedly used.

[0031] In the description of the present application, it should be noted that the terms "upper", "lower", "left", "right", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are merely for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0032] The technical solutions shown in the present application will be described in detail below through specific embodiments. It should be noted that the description order of the following embodiments is not limited as the priority order of the embodiments.

[0033] Reference Figure 1 The present embodiment provides a preparation method of an optical coating structure of a multi-junction solar cell, which comprises:

[0034] S101, providing a solar cell chip.

[0035] S102, continuously evaporating at least one first material layer, at least one second material layer and at least one third material layer on the solar cell chip to form an anti-reflection film.

[0036] S103, evaporating a fourth material layer on the anti-reflection film, and forming a mask layer on the fourth material layer.

[0037] S104, photoetching and etching the fourth material layer to form a sub-micron grating on the fourth material layer.

[0038] S105, removing the mask layer, and annealing and testing the multi-junction solar cell.

[0039] The optical coating structure preparation method of the multi-junction solar cell of the embodiment can effectively reduce the solar light reflection loss of the multi-junction solar cell, especially by using the sub-micron grating structure, the reflectivity of the multi-junction solar cell can be adjusted in a wider wavelength range, and thus the light absorption rate and the photoelectric conversion efficiency of the multi-junction solar cell are improved.

[0040] Specifically, the at least three-layer anti-reflection film can control the uniformity and thickness of the first material layer, the second material layer and the third material layer by the continuous evaporation, and thus the reflectivity of the anti-reflection film can be dynamically adjusted according to the spectral characteristics of different wavelengths, the current density of each junction of the anti-reflection film is balanced, the situation of overloading or insufficient of a certain junction is reduced, the balance of the light absorption and the current density of each junction is ensured, and thus the light absorption rate and the photoelectric conversion efficiency of the multi-junction solar cell are improved.

[0041] And, on the basis of the anti-reflective film, a fourth material layer is evaporated, and a sub-micron grating is formed on the fourth material layer to effectively adjust and optimize the propagation path of sunlight, further reducing the reflectivity, that is, the grating design is superimposed on the anti-reflective film containing at least three layers to maximize the use of sunlight and reduce reflectivity, and the reflectivity of light of a specific wavelength is more easily controlled. Specifically, the sub-micron grating can effectively scatter the incident light to various angles inside the cell, making the propagation path of the light inside the cell longer, increasing the interaction probability of the light and the active material of the cell, that is, the design of the sub-micron grating changes the electromagnetic field distribution on the surface of the multi-junction solar cell. At the interface between the sub-micron grating structure layer and the cell material, the electromagnetic field will undergo complex coupling, so that for light of a specific wavelength, the reflected wave and the incident wave at the interface can interfere and cancel each other out, thereby reducing the reflectivity, especially for light in the 700-1350nm wavelength range.

[0042] Preferably, the embodiment of the application uses an electron beam evaporation process for continuous evaporation.

[0043] Continue to combine Figures 2 to 6 The optical coating structure preparation method of the multi-junction solar cell of the application embodiment is described.

[0044] Please refer to Figure 2 A solar cell chip 1 is provided.

[0045] In the specific implementation process, the solar cell chip 1 can include a semiconductor substrate and an epitaxial layer grown on the semiconductor substrate, wherein the epitaxial layer is provided with a cell electrode.

[0046] Preferably, the semiconductor substrate includes a GaAs substrate on which an epitaxial layer is grown to form the core structure of the multi-junction solar cell. The GaAs substrate has the advantages of high electron mobility, wide band gap, strong anti-radiation capability, etc., and is suitable for high-efficiency photoelectric conversion of the multi-junction solar cell. It can also provide good lattice matching to support subsequent epitaxial layer growth.

[0047] Preferably, the epitaxial layer is formed by MOCVD (metal organic chemical vapor deposition) epitaxial growth process.

[0048] For example, the three-junction solar cell can include a Ge-based cell, a thin-film cell, etc. It can be understood that the Ge-based cell can be a GaInP / GaAs / Ge structure three-junction cell, and the thin-film cell can be a GaInP / GaAs / InGaAs structure three-junction cell. The cell electrode includes a metal layer evaporated on the above-mentioned epitaxial wafer, which can be an Ag / Au layer.

[0049] Furthermore, at least one first material layer 21, at least one second material layer 22 and at least one third material layer 23 are continuously deposited on the solar cell chip 1 to serve as an anti-reflection film 2.

[0050] In the specific implementation process, the first antireflective material is deposited on the solar cell chip 1 by adjusting the first coating rate, and the first oxygen flow rate is controlled to form a first material layer 21 with a first refractive index and a first optical thickness.

[0051] In this embodiment of the application, the first material layer 21 is formed by adjusting the refractive index and optical thickness of the first material layer 21 through the first plating rate and the first oxygen flow rate, thereby ensuring the overall uniformity and current density of the first material layer 21, optimizing the optical performance of the antireflective film 2, and improving the light absorption efficiency of the solar cell.

[0052] During the continuous evaporation process, the first deposition rate and the first oxygen flow rate can be adjusted in real time, and the deposition rate curve can be monitored in real time to complete the formation of the first material layer 21. When the deposition rate curve drops to zero, the deposition process can be considered complete. Throughout the process, the deposition rate curve is flat and stable, thereby ensuring the balance of light absorption and current density of each junction of the multi-junction solar cell, so as to improve the light absorption rate and photoelectric conversion efficiency of the multi-junction solar cell.

[0053] It is understandable that the continuous deposition of at least one first material layer 21, at least one second material layer 22, and at least one third material layer 23 on the solar cell chip 1, and the deposition of the fourth material layer 24 on the antireflection film, can be carried out in the crucible of the deposition machine. During the formation of at least one first material layer 21, the deposition power can be adjusted to 3-5kW, and the vacuum degree during deposition should not exceed 6*10. -3 Pa.

[0054] In one embodiment, the first antireflective material comprises metallic Ti particles to form a TiOx material layer, i.e., the first material layer 21 may include a TiOx material layer.

[0055] In addition, the first coating rate includes 0.3 nm / s, the first oxygen flow rate includes 35-45 sccm, the first refractive index includes 2.24, and the first optical thickness includes 50-100 nm.

[0056] Then, in the crucible of the vapor deposition machine, with a vapor deposition power of 3-5kW and a maximum of 6*10, -3 With a vacuum level of Pa, metal Ti particles are deposited on the solar cell chip 1 by adjusting the first deposition rate to 0.3 nm / s and controlling the first oxygen flow rate to 35-45 sccm, forming a TiOx material layer with a first refractive index of 2.24 and a first optical thickness of 50-100 nm.

[0057] The TiOx material layer with large refractive index is obtained by using the evaporation power of 3-5 kW and the first oxygen flow of 35-45 seem, so that the refractive index difference between the TiOx material layer and the contact layer of the solar cell chip 1 is reduced, the interface reflection is reduced, the light absorption rate and the photoelectric conversion efficiency of the multi-junction solar cell (such as a three-junction solar cell) are improved.

[0058] Preferably, the first optical thickness is 88 nm, that is, the thickness of the first material layer 21 is preferably 88 nm.

[0059] Of course, the first anti-reflective material in the embodiment of the application is not limited to the metal Ti particles, that is, according to the actual environmental requirements, the first material layer 21 can include a TiOx material layer, a ZnO material layer or an AlOx material layer, etc.

[0060] After forming the at least one first material layer 21, the thickness and the refractive index of the film layer can also be detected by an electron scanning lens (SEM) to confirm the film forming quality.

[0061] In the specific implementation process, the second anti-reflective material is evaporated on the first material layer 21 by adjusting the second evaporation rate, and the second oxygen flow is controlled to form the second material layer 22 with the second refractive index and the second optical thickness.

[0062] The second material layer 22 in the embodiment of the application controls the formation refractive index and the optical thickness of the second material layer 22 by the second evaporation rate and the second oxygen flow, ensures the overall uniformity and the current density of the second material layer 22, optimizes the optical performance of the anti-reflective film 2, and improves the light absorption efficiency of the solar cell.

[0063] That is, in the continuous evaporation process, the second oxygen flow can be adjusted in real time, and the evaporation rate curve is monitored in real time to complete the formation of the second material layer 22, so as to ensure the balance of the light absorption and the current density of each junction of the multi-junction solar cell, so as to improve the light absorption rate and the photoelectric conversion efficiency of the multi-junction solar cell.

[0064] In one embodiment, the second anti-reflective material includes metal Al particles, so as to form an AlOx material layer, that is, the second material layer 22 can include an AlOx material layer.

[0065] In addition, the second evaporation rate includes 0.2 nm / s, the second oxygen flow includes 2-10 seem, the second refractive index includes 1.95, and the second optical thickness is less than 50 nm.

[0066] Then in the crucible of the evaporation machine, the evaporation power is 3-5 kW and the oxygen flow is not higher than 6*10 -3The vacuum degree is Pa, the second plating rate is 0.2 nm / s, the second oxygen flow is 2-10 sccm, and the AlOx material layer with a second refractive index of 1.95 and a second optical thickness of less than 50 nm is formed on the solar cell chip 1.

[0067] Preferably, the second optical thickness is 20 nm, that is, the thickness of the second material layer 22 is preferably 20 nm.

[0068] It should be noted that the thickness of the second material layer 22 is preferably 20 nm to ensure the balance of the current density of the multi-junction solar cell and obtain the maximum current density.

[0069] Of course, the second anti-reflective material of the embodiment of the application is not limited to metal Al particles, that is, the second material layer 22 can also include a ZnO material layer according to actual environmental requirements.

[0070] In the specific implementation process, the third anti-reflective material is evaporated on the second material layer 22 by adjusting the third plating rate, and the third oxygen flow is controlled to form the third material layer 23 with a third refractive index and a third optical thickness.

[0071] Therefore, the third material layer 23 of the embodiment of the application controls the formation of the refractive index and the optical thickness of the third material layer 23 by the third plating rate and the third oxygen flow, ensures the overall uniformity and current density of the third material layer 23, optimizes the optical performance of the anti-reflective film 2, and improves the light absorption efficiency of the solar cell.

[0072] That is, in the continuous evaporation process, the third oxygen flow can be adjusted in real time, and the evaporation plating rate curve is monitored in real time to complete the formation of the third material layer 23, thereby ensuring the balance of the light absorption and current density of each junction of the multi-junction solar cell to improve the light absorption rate and photoelectric conversion efficiency of the multi-junction solar cell.

[0073] In one embodiment, the third anti-reflective material includes SiO2, thereby forming a SiO2 material layer, that is, the third material layer 23 can include a SiO2 material layer.

[0074] In addition, the third plating rate includes 0.2 nm / s, the third oxygen flow includes 3-10 sccm, the third refractive index includes 1.46, and the third optical thickness includes 50-100 nm.

[0075] Therefore, in the crucible of the evaporation machine, the evaporation power is 3-5 kW and the evaporation power is not higher than 6*10 -3 The vacuum degree is Pa, the third plating rate is 0.2 nm / s, the third oxygen flow is 3-10 sccm, and the substrate temperature is increased to 300-400°C, and the SiO2 material layer with a second refractive index of 1.46 and a third optical thickness of 50-100 nm is formed on the solar cell chip 1.

[0076] Preferably, the third optical thickness is 56 nm, i.e. the third material layer 23 has a thickness of preferably 56 nm.

[0077] It should be noted that the third material layer 23 is formed by the same principle of low plating rate, low power and low oxygen flow as the second material layer 22, and the temperature is increased on the basis of the original normal temperature substrate, so as to better form a film, so that SiO2 reaches high density, and lays a foundation for the adhesion of the next layer evaporation and grating preparation.

[0078] In addition, the plating rate of the second material layer 22 and the third material layer 23 is lower than that of the first material layer 21, so as to improve the film forming quality of each layer, enhance the density of the second material layer 22 and the third material layer 23, and further obtain the required refractive index range.

[0079] It should be noted that the solar waveband range of the multi-junction solar cell of the embodiment of the present application can include 300-1350 nm. For example, a three-junction cell with GaInP / GaAs / Ge structure, i.e. the GaInP layer can absorb solar light in the waveband range of 300-650 nm, the GaAs layer can absorb solar light in the waveband range of 650-900 nm, and the Ge layer can absorb solar light in the waveband range of 900-1350 nm. Therefore, the formation of the first material layer 21, the second material layer 22 and the third material layer 23 can coordinate and optimize the reflectivity of the entire waveband, meet the reflectivity regulation in different waveband ranges of the multi-junction solar cell, and further combine the refractive index difference of different material layers, so as to effectively reduce the reflection loss and improve the light absorption efficiency of each spectral segment, thereby optimizing the overall performance of the multi-junction solar cell.

[0080] Continuing to refer to Figure 2 and Figure 3 The fourth material layer 24 is formed by evaporation on the antireflection film 2, and the mask layer 3 is formed on the fourth material layer 24.

[0081] In the specific implementation process, the fourth antireflection material is evaporated on the third material layer 23 by adjusting the fourth plating rate, so as to form the fourth material layer 24 with the fourth refractive index and the fourth optical thickness.

[0082] In one embodiment, the fourth antireflection material includes MgF2, so as to form a MgF2 material layer, i.e. the fourth material layer 24 can include a MgF2 material layer.

[0083] And the fourth plating rate includes 0.5 nm / s, the fourth refractive index includes 1.28, and the fourth optical thickness includes 30 nm.

[0084] Then, in the crucible of the evaporation machine, the evaporation power is 3-5 kW and the oxygen flow is not higher than 6*10 -3The vacuum degree of the Pa is adjusted to 0.5 nm / s to evaporate MgF2 on the solar cell chip 1, and the evaporation rate curve is monitored in real time to form a MgF2 material layer with a fourth refractive index of 1.28 and a fourth optical thickness of 30 nm.

[0085] It should be noted that the MgF2 material layer as the outermost anti-reflective material can effectively reduce the reflection of short-wave light and enhance light absorption. The fourth optical thickness of 30 nm is calculated based on the optical transmission matrix method and also obtained according to the wavelength optimization of the sub-micron grating, thereby more conducive to prolonging the light path, improving the light trapping capability, increasing the optical path, and reducing reflection. That is, the fourth material layer 24 not only realizes the function of the anti-reflective film, but also lays the foundation for the subsequent grating structure.

[0086] The MgF2 material layer is a porous structure, so the porous MgF2 material layer has a higher surface area and more micro-pores than the traditional dense material layer. By adjusting the porosity and pore structure, the refractive index of the MgF2 material layer can be effectively adjusted to have ideal optical properties in different wavelength ranges. The introduction of the porous structure can increase the scattering and absorption of light in the material. Through multiple scattering of light, the path of light can be increased, thereby realizing efficient utilization of light of different wavelengths and greatly improving the photoelectric conversion efficiency of the multi-junction solar cell.

[0087] Of course, the fourth anti-reflective material of the present application is not limited to MgF2. According to actual environmental requirements, the fourth material layer 24 can also include an aluminum-doped zinc oxide material layer or a combination of organic polymers and inorganic nanoparticles.

[0088] In the specific implementation process, a mask layer 3 is formed on the fourth material layer 24, including: cleaning the solar cell chip with the fourth material layer 24, coating photoresist on the fourth material layer 24, and hardening the photoresist at a preset temperature for a set time to form a mask layer 3 with a set photoetching thickness.

[0089] Preferably, the set photoetching thickness includes 5 um, the preset temperature includes 110°C, and the set time includes 10 min.

[0090] Then, by setting the photoetching thickness to provide sufficient etching resistance, the photoresist is prevented from being etched through too early in the etching process. By presetting the temperature and the set time, the adhesion and etching resistance of the photoresist are considered, and the problem of dissolution or warping during subsequent development is prevented.

[0091] Continuing to refer to Figure 4 and Figure 5 , the fourth material layer 24 is photoetched and etched to form a sub-micron grating 4 on the fourth material layer 24.

[0092] In the implementation process, the solar cell chip 1 is holographic exposed by a holographic light source with a set wavelength to form a grating pattern on the mask layer 3, and based on the grating pattern, the fourth material layer 24 is etched to form a submicron grating 4 with a set etching thickness on the fourth material layer 24.

[0093] Therefore, based on the submicron grating 4, the light is reflected and refracted multiple times through the periodic microstructure, thereby increasing the light absorption path, enabling the multi-junction solar cell to effectively capture more sunlight, and improving the light absorption rate and photoelectric conversion efficiency of the multi-junction solar cell. Through the holographic exposure and etching technology, the shape and size of the submicron grating 4 can be accurately controlled to achieve optimal spectral regulation, thereby optimizing the overall photoelectric conversion efficiency of the multi-junction solar cell.

[0094] The fourth material layer 24 is formed into the submicron grating 4 through photolithography and etching, and the fourth material layer 24 forms a grating pattern groove 41 on the anti-reflection film 2 based on the grating pattern, that is, the submicron grating 4 has the grating pattern groove 41.

[0095] Further, the solar cell chip 1 is holographic exposed by a holographic light source with a set wavelength, a set exposure time and a set beam angle.

[0096] Preferably, the set wavelength includes 300 nm, the set exposure time includes 2 min, the set beam angle includes 30°, and the set etching thickness includes 30 nm.

[0097] That is, the solar cell chip 1 is holographic exposed by a holographic light source with a wavelength of 300 nm, the exposure time is 2 min to ensure that the grating pattern is correctly transferred in the mask layer 3, while avoiding overexposure, and the beam angle is 30°, thereby effectively affecting the period and refraction characteristics of the grating, thereby controlling the microstructure of the submicron grating 4 to optimize the reflectivity in different wavebands.

[0098] And after the exposure is completed, developing for 2 min, and then placing in an oven at 110°C for 30 min to harden the film.

[0099] The ICP dry etching can be used to etch the submicron grating 4 with a thickness of 30 nm and a period of 300 nm, to ensure the appropriate optical properties of the submicron grating 4 and enhance the light capturing ability of the multi-junction solar cell.

[0100] Reference Figure 6 The mask layer 3 is removed, and the multi-junction solar cell is annealed and tested.

[0101] In one embodiment, after the sub-micron grating 4 is obtained, the mask layer 3 is removed, and the complete multi-junction solar cell is placed in a tube furnace for annealing at 300℃ for 10 minutes. It should be noted that the lower annealing temperature is more conducive to the adhesion of the first material layer 21, the second material layer 22, the third material layer 23 and the fourth material layer 24 and the warping caused by the coefficient of thermal expansion. The multi-junction solar cell thus obtained has a solar light reflectivity of less than 3% in the wavelength range of 300-1350 nm.

[0102] That is, the multi-junction solar cell with the optical coating structure prepared by the method for preparing the optical coating structure of the multi-junction solar cell according to the embodiments of the present application comprises at least one first material layer 21, at least one second material layer 22 and at least one third material layer 23 of the anti-reflective film 2 obtained by continuous evaporation on the solar cell chip 1, and the fourth material layer 24 formed on the anti-reflective film 2 by evaporation. The fourth material layer 24 is photoetched and etched by forming the mask layer 3 on the fourth material layer 24, so as to form the sub-micron grating 4 on the fourth material layer 24. Thus, the solar light reflection loss of the multi-junction solar cell can be effectively reduced. In particular, by using the sub-micron grating 4 structure, the reflectivity of the multi-junction solar cell can be adjusted in a wider wavelength range, thereby improving the light absorption rate and the photoelectric conversion efficiency of the multi-junction solar cell.

[0103] In one embodiment, the multi-junction solar cell can comprise a 4-junction solar cell. For example, the wavelength range is further divided into 300-650 nm, 650-800 nm, 800-1100 nm and 1100-1350 nm. By adjusting the thickness of each layer of the anti-reflective film 2 containing the multi-layer material layer of the optical coating structure, the reflectivity intensity required for a certain wavelength range can be accurately adjusted, so as to balance the current density obtained by finally connecting in series. Meanwhile, the effect of the preparation method according to the present application is more obvious in a 5-junction, 6-junction or even higher-junction multi-junction solar cell.

[0104] In one embodiment, the sub-micron grating 4 can also be prepared by nanoimprint technology.

[0105] In one embodiment, the anti-reflective film 2 can also be a single-layer or double-layer film structure, that is, the sub-micron grating 4 is prepared on the basis of the single-layer or double-layer film structure.

[0106] The embodiments of the present application also disclose a multi-junction solar cell optical coating structure, which can be prepared by the method for preparing the optical coating structure of the multi-junction solar cell according to any one of the above embodiments. Referring to Figure 6 The multi-junction solar cell optical coating structure comprises a solar cell chip 1, an anti-reflective film 2 connected to the solar cell chip 1 and a fourth material layer 24 connected to the anti-reflective film 2.

[0107] In the implementation process, the anti-reflection film 2 comprises at least one first material layer 21, at least one second material layer 22 and at least one third material layer 23 which are sequentially stacked on the solar cell chip 1, wherein the fourth material layer 24 comprises the sub-micron grating 4 and the grating pattern groove 41, the sub-micron grating 4 is connected to the side of the third material layer 23 away from the second material layer 22, and the grating pattern groove 41 is connected to the third material layer 23 from the side of the sub-micron grating 4 away from the third material layer 23 and is communicated to the third material layer 23.

[0108] Therefore, the optical coating structure of the multi-junction solar cell can effectively reduce the solar light reflection loss of the multi-junction solar cell by the multi-layer anti-reflection film 2 and the sub-micron grating 4 connected to the anti-reflection film 2, especially by using the structure of the sub-micron grating 4 in cooperation with the anti-reflection film 2, the reflectivity of the multi-junction solar cell can be adjusted in a wider wavelength range, thereby improving the light absorption rate and photoelectric conversion efficiency of the multi-junction solar cell.

[0109] In one embodiment, the first material layer 21 comprises a TiOx material layer, and the first material layer 21 has a first refractive index and a first optical thickness, the first refractive index comprises 2.24, and the first optical thickness comprises 50-100 nm.

[0110] In one embodiment, the second material layer 22 comprises an AlOx material layer, and the second material layer 22 has a second refractive index and a second optical thickness, the second refractive index comprises 1.95, and the second optical thickness is less than 50 nm.

[0111] In one embodiment, the third material layer 23 comprises a SiO2 material layer, and the third material layer 23 has a third refractive index and a third optical thickness, the third refractive index comprises 1.46, and the third optical thickness comprises 50-100 nm.

[0112] In one embodiment, the fourth material layer 24 comprises a MgF2 material layer, and the fourth material layer 24 has a fourth refractive index and a fourth optical thickness, the fourth refractive index comprises 1.28, and the fourth optical thickness comprises 30 nm.

[0113] The fourth optical thickness is the same as the thickness of the sub-micron grating 4 and the groove depth of the grating pattern groove 41, that is, the thickness of the sub-micron grating 4 and the groove depth of the grating pattern groove 41 comprise 30 nm, so as to ensure the appropriate optical properties of the sub-micron grating 4 and enhance the light capturing capability of the multi-junction solar cell.

[0114] For other working principles and processes of the optical coating structure of the multi-junction solar cell, refer to the foregoing description of the preparation method of the optical coating structure of the multi-junction solar cell in the present embodiment, which will not be repeated here.

[0115] The optical coating structure of the multi-junction solar cell and the preparation method thereof provided in the present application are described in detail above, and the principles and implementation manners of the present application are described by using specific examples. It should be noted that the description of each embodiment in the present application has its own emphasis, and the parts not described or recorded in a certain embodiment can be referred to the related description of other embodiments.

[0116] The above are only preferred embodiments of the present application, and do not limit the patent scope of the present application. Each technical feature of the technical solutions of the present application can be combined arbitrarily. In order to make the description simple, each technical feature in the above embodiments is not described in all possible combinations. Any equivalent structure or equivalent flow conversion made by using the content of the present application and the drawings, or directly or indirectly applied in other related technical fields, as long as the combination of these technical features does not exist contradictory, is also included in the patent protection scope of the present application.

Claims

1. An optical coating structure for a multi-junction solar cell, characterized by, The solar cell chip, an anti-reflection film connected to the solar cell chip, and a fourth material layer connected to the anti-reflection film are included. The anti-reflection film includes at least one first material layer, at least one second material layer, and at least one third material layer sequentially stacked on the solar cell chip. The fourth material layer includes a sub-micron grating connected to a side of the third material layer away from the second material layer and a grating pattern groove connected to the sub-micron grating on a side of the sub-micron grating away from the third material layer and communicating to the third material layer. The solar cell chip includes a semiconductor substrate and an epitaxial layer grown on the semiconductor substrate, and a cell electrode provided on the epitaxial layer.

2. The optical coating structure of a multi-junction solar cell of claim 1, wherein, The first material layer includes a TiOx material layer, and the first material layer has a first refractive index including 2.24 and a first optical thickness including 50-100 nm.

3. The optical coating structure of a multi-junction solar cell of claim 1, wherein, The second material layer includes an AlOx material layer, and the second material layer has a second refractive index including 1.95 and a second optical thickness < 50 nm.

4. The optical coating structure of a multi-junction solar cell of claim 1, wherein, The third material layer includes a SiO2 material layer, and the third material layer has a third refractive index including 1.46 and a third optical thickness including 50-100 nm.

5. The optical coating structure of a multi-junction solar cell of claim 1, wherein, The fourth material layer includes a MgF2 material layer, and the fourth material layer has a fourth refractive index including 1.28 and a fourth optical thickness including 30 nm.

6. The optical coating structure of a multi-junction solar cell of claim 1, wherein, The fourth optical thickness is the same as the thickness of the sub-micron grating and the groove depth of the grating pattern groove.

7. The optical coating structure of a multi-junction solar cell of claim 6, wherein, The fourth material layer includes an aluminum-doped zinc oxide material layer or a combination of an organic polymer and inorganic nanoparticles material layer.

8. The optical coating structure of a multi-junction solar cell of claim 6, wherein, The solar light wavelength range of the multi-junction solar cell includes 300-1350 nm.

9. The optical coating structure of a multi-junction solar cell of claim 1, wherein, The solar light reflectivity of the multi-junction solar cell is less than 3%.

10. The optical coating structure of a multi-junction solar cell of claim 1, wherein, ​

Images