CN112904545A - Secondary condenser based on one-dimensional photonic crystal omnidirectional reflector - Google Patents
Secondary condenser based on one-dimensional photonic crystal omnidirectional reflector Download PDFInfo
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- G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
- G02B19/0004—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed
- G02B19/0019—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed having reflective surfaces only (e.g. louvre systems, systems with multiple planar reflectors)
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- G—PHYSICS
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- G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
- G02B1/002—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of materials engineered to provide properties not available in nature, e.g. metamaterials
- G02B1/005—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of materials engineered to provide properties not available in nature, e.g. metamaterials made of photonic crystals or photonic band gap materials
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
- G02B19/0033—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use
- G02B19/0038—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with ambient light
- G02B19/0042—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with ambient light for use with direct solar radiation
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- H—ELECTRICITY
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- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
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- H01L31/054—Optical elements directly associated or integrated with the PV cell, e.g. light-reflecting means or light-concentrating means
- H01L31/0547—Optical elements directly associated or integrated with the PV cell, e.g. light-reflecting means or light-concentrating means comprising light concentrating means of the reflecting type, e.g. parabolic mirrors, concentrators using total internal reflection
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/52—PV systems with concentrators
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Abstract
The embodiment of the application discloses a secondary condenser based on a one-dimensional photonic crystal omnidirectional reflector, which comprises a substrate and a one-dimensional photonic crystal coating plated on the substrate; the photonic crystal coating comprises a plurality of one-dimensional photonic crystal layers which are connected in series and have different lattice constants; the one-dimensional photonic crystal layer includes two materials having different refractive indices. In the scheme provided by the embodiment of the invention, the composite structure with the refractive index periodically arranged along one direction, namely the one-dimensional photonic crystal, can reflect light with any incidence angle and any polarization direction in a certain waveband, and finally forms the omnidirectional photonic band gap.
Description
Technical Field
The application relates to the technical field of optics, in particular to a secondary condenser based on a one-dimensional photonic crystal omnidirectional reflector.
Background
At present, the technology of solar power generation is mainly divided into three types, namely concentrating photo-thermal power generation, flat-panel photovoltaic power generation and concentrating photovoltaic power generation.
The Concentrating Photovoltaic (CPV) power generation technology is a technology that uses cheap optical devices (such as fresnel lenses) to concentrate sunlight on small-area solar cells and then converts light energy into electric energy through a photovoltaic effect, and is widely applied to industrial scenes.
In concentrated photovoltaic systems, a significant portion of the cost is concentrated on III-V solar cell materials. In order to make III-V cell based concentrated photovoltaic systems cost competitive, it is necessary to increase the concentration ratio of the system, thereby increasing the light efficiency of the whole element.
However, as the concentration ratio increases, two problems are also caused to the concentrating photovoltaic system:
first, the acceptance angle of a concentrated photovoltaic system decreases with increasing concentration ratio; second, the uniformity of the irradiance distribution that the optics converge on the cell surface is reduced.
Therefore, how to ensure that the concentrating photovoltaic system has a higher concentrating ratio and a larger acceptance angle and uniform irradiation distribution is one of the key factors for determining whether the concentrating photovoltaic technology can be successful in the photovoltaic field.
Disclosure of Invention
An embodiment of the present invention is directed to a concentrating photovoltaic system and a secondary concentrator based on a one-dimensional photonic crystal omnidirectional reflector, so as to at least partially solve the problems in the prior art.
The purpose of using a Secondary Optical Element (SOE) in a concentrated photovoltaic system is to reduce the sensitivity of its optical efficiency to solar tracking errors, improving the uniformity of irradiance distribution across the cell. The secondary condenser can be classified into two types according to optical principles, the first type being a refractive type secondary optical element, and the second type being a reflective type secondary optical element.
The reflective secondary optical element is widely used because of its advantages such as easy manufacturing and low cost. The main factor influencing the optical efficiency of the reflection-type secondary optical element is the reflectivity of the reflection surface of the reflection-type secondary optical element in the operating band (380nm-1650nm) of the III-V solar cell. The most widely used reflectors at present are based on metals or media. They all have more or less certain disadvantages. Metal reflectors, while capable of providing full-angle reflection, do not achieve very high reflectivity. Dielectric reflectors can provide high reflectivity but are very sensitive to the operating angle.
The characteristics of photonic crystals, particularly one-dimensional photonic crystals, make it possible to manufacture high-reflectivity omnidirectional reflectors. Mirrors made of photonic crystal materials can overcome the disadvantages of conventional metallic and dielectric mirrors.
The invention provides a secondary condenser with a surface plated with a one-dimensional photonic crystal omnidirectional reflector, which does not generate absorption or reflection loss in the process of redirecting light rays converged by a Fresnel lens to the surface of a condensing battery, thereby improving the optical performance of a system and improving the power generation efficiency of a condensing photovoltaic system. Photons of frequencies within the photonic band gap are not allowed to exist in the photonic crystal and are totally reflected when a beam of light having a frequency within the photonic band gap is incident on the photonic crystal. Thus a photonic crystal made of a dielectric material selected for non-absorption can reflect incident light from any direction with a reflectivity of almost 100%.
The invention specifically comprises the following scheme:
a secondary condenser based on a one-dimensional photonic crystal omnidirectional reflector comprises a substrate and a one-dimensional photonic crystal coating plated on the substrate;
the one-dimensional photonic crystal coating comprises a plurality of one-dimensional photonic crystal layers, and each one-dimensional photonic crystal layer comprises a high-refractive-index material and a low-refractive-index material; in the plurality of one-dimensional photonic crystal layers, the material with the high refractive index and the material with the low refractive index have different thicknesses; the reflectivity of the multiple layers of the one-dimensional photonic crystal coating to light with different wavelengths is more than 99%, so that the reflectivity of the one-dimensional photonic crystal coating to light with the wavelength range of 380nm-1650nm is more than 99%. .
Optionally, the substrate comprises: one or more of a quartz substrate, a K9 glass substrate, a sapphire substrate, and a Si substrate.
Optionally, of the two materials of the one-dimensional photonic crystal coating, the material with high refractive index is selected from TiO2、ZnSe、Ta2O5ZnS; the material with low refractive index is selected from MgF2、SiO2、Na3ALF6、AL2O3。
Optionally, the multiple layers of the one-dimensional photonic crystal coating layer respectively form different omnidirectional photonic band gaps, and the omnidirectional photonic band gaps of the one-dimensional photonic crystal coating layer are overlapped with each other.
Optionally, the high refractive index material is MgF2The low refractive index material is TiO2。
Optionally, of the plurality of tiers, MgF2And TiO2A filling ratio of between 0.2 and 0.6, wherein the filling ratio is d (TiO)2):(d(TiO2)+d(MgF2) D) is the thickness of the material; the number of the crystal lattice periods of the layers is 13, 14 or 15, the crystal lattice constant of the first layer is 138nm, and the relation between the lattice constants of the (i + 1) th layer and the ith layer satisfies di+1:di1.01:1 to 1.2:1, wherein the lattice constant is MgF2And TiO2The sum of the thicknesses of (a) and (b).
Optionally, of the plurality of tiers, MgF2And TiO2The filling ratio is 1/3, the number of lattice cycles of the delamination is 14, and the lattice constant relation between the i +1 th delamination and the i-th delamination satisfies di+1:di＝1.15:1。
Optionally, the substrate comprises a side wall for reflecting light, the side wall enclosing an inlet and an outlet for light to enter and exit, the inlet being larger in size than the outlet; the side wall of the substrate is enclosed to form a frustum pyramid or a revolving body.
The embodiment of the application further provides a concentrating photovoltaic system, which comprises the secondary concentrator based on the photonic crystal omnidirectional reflector, a concentrating battery and a Fresnel lens.
Optionally, the fresnel lens is used as a primary condenser, and an outlet surface of the secondary condenser is connected to the condensing battery.
The concentrating photovoltaic system and the secondary concentrator based on the one-dimensional photonic crystal omnidirectional reflector provided by the embodiment of the invention at least have the following advantages:
firstly, the photonic crystal reverse sealing mirror made of the optical dielectric material has extremely low loss; under the same intensity of illumination, the temperature rise value of the surface of the photonic crystal reflector is much smaller than that of the metal reflecting surface. A one-dimensional photonic crystal is a composite structure in which refractive indices are periodically arranged in only one direction. If the proper refractive index and the thickness of the dielectric layer are selected, the one-dimensional photonic crystal can reflect light with any incidence angle and any polarization direction in a certain waveband, and finally the omnidirectional photonic band gap is formed.
In an alternative embodiment, materials with different refractive indexes are selected to form different photonic crystal blocks with different lattice periods, omnidirectional photonic band gaps of the photonic crystals are overlapped, and the one-dimensional photonic crystals are connected in series to form a photonic heterostructure with a de-omnidirectional photonic band gap in a 380nm-1650nm waveband.
In an alternative embodiment, of the two materials of the photonic crystal block, the high refractive index material is selected from TiO2, ZnSe, Ta2O5, ZnS; the material with low refractive index is selected from MgF2、SiO2、Na3ALF6、AL2O3. The omnidirectional photonic band gaps of the one-dimensional photonic crystals are mutually overlapped, and the one-dimensional photonic crystals are connected in series to form a photonic heterostructure with the omnidirectional photonic band gap at a wave band of 380nm-1650 nm.
In an alternative embodiment, TiO2 and MgF2 are further selected as high-refractive-index media and low-refractive-index media respectively, and a composite structure formed by the two media is periodically arranged along a single direction. Although the dielectric material TiO2 and MgF2 has extremely low reflectivity, photonic crystals formed by periodically arranging the dielectric material TiO2 and MgF2 in a certain mode can realize high omnidirectional reflection characteristics in a specific wave band (for example, 380nm-1650 nm). The reflectivity theoretically reaches 100%, and the reflectivity of the photonic crystal high-reflectivity mirror prepared by actually adopting an electron beam evaporation method can also reach more than 99%.
Of course, it is not necessary for any product to achieve all of the above-described advantages at the same time for the practice of the present application.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
Fig. 1 is a schematic diagram of a primary condenser and a secondary condenser included in a concentrating photovoltaic system provided in an embodiment of the present application.
Fig. 2 is a schematic diagram of a secondary condenser provided in an embodiment of the present application.
Fig. 3 is a top view of a secondary concentrator provided in an embodiment of the present application.
Fig. 4 is a parameter-dependent schematic diagram of a one-dimensional photonic crystal structure provided in an embodiment of the present application.
Fig. 5 is a schematic diagram of a one-dimensional photonic crystal hetero-reflectivity curve provided by an embodiment of the present application.
Fig. 6 is a schematic diagram of the relationship between the system optical efficiency and the deflection angle of the concentrating photovoltaic system provided by the embodiment of the present application.
Fig. 7 is a schematic diagram of irradiation uniformity versus deflection angle of a concentrated photovoltaic system provided by an embodiment of the present application.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments that can be derived from the embodiments given herein by a person of ordinary skill in the art are intended to be within the scope of the present disclosure.
The embodiment of the invention provides a concentrating photovoltaic system and a secondary concentrator applied to the concentrating photovoltaic system. Fig. 1 is a schematic view of a concentrated photovoltaic system according to an embodiment of the present invention. As shown in fig. 1, the concentrated photovoltaic system 100 includes a primary concentrator 10 and a secondary concentrator 20. The primary concentrator 10 may be a fresnel lens. A condenser cell 30 is connected below the secondary condenser 20, i.e., away from the primary condenser 10.
In the concentrating photovoltaic system provided by the embodiment of the invention, the diameter of the fresnel lens can be 170mm, the focal length can be about 230mm, and the concentrating cell 30 can be a multi-junction concentrating gallium arsenide cell, the area of which can be 10mm × 10mm, and the size corresponds to the outlet size of the secondary concentrator.
Fig. 2 is a schematic view of a secondary condenser according to an embodiment of the present disclosure. Fig. 3 is a schematic top view. The ratio of the thickness of the plating layer 22 to the substrate 21 in fig. 3 is exaggerated to make the plating layer 22 clearly visible to those skilled in the art, and is not intended to limit the scope of the present invention.
As shown in fig. 2 and 3, the secondary condenser 20 is a one-dimensional photonic crystal omnidirectional reflector-based secondary condenser, and includes: a substrate 21 and a one-dimensional photonic crystal plating layer 22 plated on the substrate 21.
The substrate may be, for example, one or more of a quartz substrate, a K9 glass substrate, a sapphire substrate, and a Si substrate. As long as a substrate capable of good bonding with the plating layer 22 is available.
The one-dimensional photonic crystal plating layer 22 may be deposited on the substrate 21 by evaporation or sputtering, for example.
The one-dimensional photonic crystal coating 22 comprises a plurality of one-dimensional photonic crystal layers, wherein each one-dimensional photonic crystal layer comprises a high refractive index material and a low refractive index material; in the plurality of one-dimensional photonic crystal layers, the material with the high refractive index and the material with the low refractive index have different thicknesses; the reflectivity of the multiple layers of the one-dimensional photonic crystal coating to light with different wavelengths is more than 99%, so that the reflectivity of the one-dimensional photonic crystal coating to light with the wavelength range of 380nm-1650nm is more than 99%.
Of the two materials of the one-dimensional photonic crystal coating, the material with high refractive index can be selected from TiO2、ZnSe、Ta2O5ZnS, etc.; the material with low refractive index is selected from MgF2、SiO2、Na3ALF6、AL2O3And the like. The selection of the materials is mainly considered that the extinction coefficient of the selected dielectric material is close to zero in a 380nm-1650nm wave band, and the difference between the refractive indexes of the high-refractive-index material and the low-refractive-index material is as large as possible.
In some embodiments, as shown in fig. 2, the secondary concentrator 20 has a square frustum shape, the inlet 24 is square, and the outlet 25 is also a square outlet. In other embodiments, the shape of the secondary concentrator 20 may not be limited to a quadrangular frustum.
The substrate comprises a side wall for reflecting light, the side wall encloses an inlet and an outlet for light to enter and exit, and the size of the inlet is larger than that of the outlet; the side wall of the substrate is enclosed to form a frustum pyramid or a revolving body. In one embodiment, as shown in the embodiment of the substrate 21 provided in fig. 1 to 3, the substrate 21 includes four side walls 23, the four side walls 23 are connected to each other at four sides to form an inlet 24 and an outlet 25, the four side walls 23 are arranged from the inlet 24 to the outlet 25 to form an inlet and an outlet, and the size of the inlet 24 is larger than that of the outlet 25. The size of the outlet 25 matches the size of the concentrator cell 30 and the angle of each sidewall 23 to the vertical when the secondary concentrator 100 is placed vertically can vary, for example. The height of the secondary concentrator 100 when placed vertically may be determined from the demand by simulation.
In this embodiment, the outlet of the secondary concentrator is matched with the size of the cell, taking 10mm by 10 mm; the inlet is determined according to the acceptance angle to be achieved, and is taken as 24mm by 24 mm; the height is 50mm determined according to a statistical rule in simulation calculation, and once the upper bottom surface, the lower bottom surface and the height of the quadrangular frustum pyramid are determined, the included angle is determined.
The one-dimensional photonic crystal comprises a high refractive index material and a low refractive index material; in a preferred embodiment of the invention, the high refractive index material is TiO2The low refractive index material is MgF2。
The principle that the reflectivity of the one-dimensional photonic crystal can be close to 100% is as follows: photons of frequencies within the photonic band gap are not allowed to exist in the photonic crystal and are totally reflected when a beam of light having a frequency within the photonic band gap is incident on the photonic crystal. Therefore, the photonic crystal made of the dielectric material without absorption can reflect incident light from any direction, and the reflectivity is more than 99% and can reach 100%.
The reflector manufactured according to the principle can overcome a plurality of defects of a metal reflector: because the optical medium has very small absorption loss of optical waves in a depth of several wavelengths, the photonic crystal reverse sealing mirror made of the optical medium material has extremely small loss; meanwhile, compared with an absorption thin layer generated on the surface of the metal due to the skin effect, the absorption of the photonic crystal reflector to light waves is distributed in a plurality of media with the thickness of several wavelengths, and the volume of heat distribution generated due to the absorption of light is much larger, so that the temperature rise value of the surface of the photonic crystal reflector is much smaller than that of the metal reflecting surface under the same intensity of illumination, and the surface of the reflector is not easy to damage. Therefore, the reflector realizes low loss and full-angle reflection and is a novel reflector with high quality. The one-dimensional photonic crystal is a structure in which media are periodically arranged in one direction, and the expression form of a photonic forbidden band is that all reflection can be realized on incident electromagnetic waves in the forbidden band no matter the polarization state and the incident angle. Because photons having frequencies within the photonic band gap are not allowed to exist in the photonic crystal bandgap, a beam of light having a frequency within the photonic band gap is totally reflected when incident on the photonic crystal. Therefore, a photonic crystal made of dielectric material selected to be non-absorbing can reflect incident light from any direction, and the reflectivity can be close to 100%.
In addition to one-dimensional photonic crystal structuresBesides the application of the properties, in the embodiment of the invention, aiming at the problem of optical energy absorption or reflection loss caused in the process of redirecting incident light rays by a secondary condenser and aiming at the absorption characteristic of a concentrating photovoltaic cell, the structure and the characteristic of a one-dimensional photonic crystal omnidirectional medium reflector are researched through a transmission matrix Theory (TMM), and the structure parameters of the one-dimensional photonic crystal and TiO are optimized2With MgF2As a high-low refractive index material and K9 glass as a substrate material, the photonic heterostructure has an omnidirectional photonic band gap within the wave band range of 380-1650 nm.
One-dimensional photonic crystals (1DPCs) are a composite structure in which the refractive index is periodically arranged in only one direction. If the appropriate refractive index and dielectric layer thickness are selected, (such as TIO2 and MGF2) the one-dimensional photonic crystal can reflect light with any incident angle and any polarization direction in a certain waveband, and finally form omnidirectional Photonic Band Gaps (PBGs).
To achieve a wide bandgap, omnidirectional, high reflectivity omnidirectional photonic bandgap, a pair of high and low index materials with a large refractive index ratio is required. However, the materials available in nature in the visible light band are limited. At present, in the material of practical value, the maximum refractive index is not more than 2.6 and the minimum refractive index is not less than 1.3 in the visible wave band. Therefore, it is difficult to increase the omnidirectional photonic band gap width of the one-dimensional photonic crystal in the visible light region by increasing the refractive index ratio of the high refractive index material and the low refractive index material.
In the embodiment of the invention, the frequency range of the omnidirectional reflector can be expanded by combining two or more one-dimensional photonic crystals in a layered manner into a photonic heterostructure by utilizing the mutual overlapping of the omnidirectional photonic band gaps of the adjacent photonic crystals. In addition, three Thus-Morse substructures may be combined to form a heterostructure to enlarge the omnidirectional photonic bandgap. In addition, the method is suitable for photon heterostructures of any number of cascade 1DPCs according to the design rule of the maximum PBGs width omnidirectional reflector.
In order to realize the omnidirectional photon forbidden band within the absorption spectrum range of 380-1650nm of the concentrating photovoltaic cell, the embodiment of the invention selects TiO2And MgF2Respectively used as a medium with high refractive index and a medium with low refractive index,different photonic crystal blocks PCn, PCi, PC2, PC1 are formed with different lattice periods. The omnidirectional photonic band gaps of the one-dimensional photonic crystals are mutually overlapped, and the one-dimensional photonic crystals are connected in series to form a photonic heterostructure with the omnidirectional photonic band gap at the 380-1650nm waveband. The high refractive index medium being TiO2The low refractive index medium is MgF2。
In a preferred embodiment, the MgF2 and TiO2 fill ratio is between 0.2 and 0.6 in the plurality of layers, wherein the fill ratio is d (TiO 2)2):(d(TiO2)+d(MgF2) D) is the thickness of the material; the number of the crystal lattice periods of the layers is 13, 14 or 15, the crystal lattice constant of the first layer is 138nm, and the relation between the lattice constants of the (i + 1) th layer and the ith layer satisfies di+1:di1.01:1 to 1.2:1, wherein the lattice constant is MgF2And TiO2The sum of the thicknesses of (a) and (b).
More preferably, the number of lattice cycles of the delamination is 14, and the lattice constant relationship between the i +1 th delamination and the i-th delamination satisfies di+1:di＝1.15:1。
Since the main object of calculation is the reflection spectrum of the photonic crystal, a relatively mature and intuitive Transfer Matrix Method (TMM) is adopted in the theoretical method. The theory of transmission matrices is described in detail in many documents and is not described in detail here. The all-angle reflection device is simple in structure and easy to prepare, can realize omnidirectional photon forbidden bands within the absorption spectrum range of 380-1650nm of the concentrating photovoltaic cell, and has the reflectivity of more than 99.9%.
Fig. 5 is a schematic diagram showing a reflectance curve. As shown in FIG. 5, the average reflectivity of incident light at any angle in the 380-1650nm band is greater than 99%.
FIG. 6 is a schematic diagram showing the optical efficiency and deflection angle of the system. As shown in fig. 6, at normal incidence, the optical efficiency of the concentrating photovoltaic system with the addition of the one-dimensional photonic crystal omnidirectional reflector based secondary concentrator (HTPODTR) is improved by 13.48 percent compared with the optical efficiency of the concentrating photovoltaic system with the addition of the metal AL reflector secondary concentrator (HTPM), and is improved by 5.71 percent compared with the optical efficiency of the concentrating photovoltaic system with the addition of the refractive secondary concentrator (STP), and all three systems have comparable acceptance angles. The receiving angles of the three groups of row pairs and the concentrating photovoltaic system without the secondary concentrator are greatly improved.
FIG. 7 is a graph showing uniformity of irradiation versus deflection angle. As shown in fig. 7, the concentrated photovoltaic system with HTPODTR added has comparable uniformity of cell surface radiation distribution to the concentrated photovoltaic system with HTPM added, and is improved over the concentrated photovoltaic system with STP added.
The concentrating photovoltaic system and the secondary concentrator based on the one-dimensional photonic crystal omnidirectional reflector provided by the embodiment of the invention at least have the following advantages:
firstly, in the scheme provided by the embodiment of the invention, the photonic crystal reverse sealing mirror made of the optical dielectric material has extremely low loss; under the same intensity of illumination, the temperature rise value of the surface of the photonic crystal reflector is much smaller than that of the metal reflecting surface. One-dimensional photonic crystals (1DPCs) are a composite structure in which the refractive index is periodically arranged in only one direction. If the proper refractive index and the thickness of the dielectric layer are selected, the one-dimensional photonic crystal can reflect light with any incidence angle and any polarization direction in a certain waveband, and finally the omnidirectional photonic band gap is formed.
In alternative embodiments, TiO is selected for use2And MgF2The high-refractive-index medium and the low-refractive-index medium respectively form different photonic crystal blocks PCn, PCi, PC2 and PC1 with different lattice period cycles. The omnidirectional photonic band gaps of the one-dimensional photonic crystals are mutually overlapped, and the one-dimensional photonic crystals are connected in series to form a photonic heterostructure with the omnidirectional photonic band gap at the 380-1650nm waveband.
The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, the system or system embodiments are substantially similar to the method embodiments and therefore are described in a relatively simple manner, and reference may be made to some of the descriptions of the method embodiments for related points. The above-described system and system embodiments are only illustrative, wherein the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
The concentrating photovoltaic system and the secondary concentrator provided by the present application are introduced in detail, and a specific example is applied in the present application to explain the principle and the implementation of the present application, and the description of the above embodiment is only used to help understand the method and the core idea of the present application; meanwhile, for a person skilled in the art, according to the idea of the present application, the specific embodiments and the application range may be changed. In view of the above, the description should not be taken as limiting the application.
Claims (10)
1. A secondary condenser based on a one-dimensional photonic crystal omnidirectional reflector is characterized by comprising a substrate and a one-dimensional photonic crystal coating plated on the substrate;
the one-dimensional photonic crystal coating comprises a plurality of one-dimensional photonic crystal layers, and each one-dimensional photonic crystal layer comprises a high-refractive-index material and a low-refractive-index material; in the plurality of one-dimensional photonic crystal layers, the material with the high refractive index and the material with the low refractive index have different thicknesses; the reflectivity of the multiple layers of the one-dimensional photonic crystal coating to light with different wavelengths is more than 99%, so that the reflectivity of the one-dimensional photonic crystal coating to light with the wavelength range of 380nm-1650nm is more than 99%. .
2. The photonic crystal omni-directional mirror based secondary concentrator of claim 1, wherein the substrate comprises: one or more of a quartz substrate, a K9 glass substrate, a sapphire substrate, and a Si substrate.
3. The photonic crystal omni-directional reflector based secondary concentrator of claim 1, wherein the one-dimensional photonic crystal coating is made of two materials with high refractive index selected from TiO2、ZnSe、Ta2O5ZnS; the material with low refractive index is selected from MgF2、SiO2、Na3ALF6、AL2O3。
4. The photonic crystal omni-directional reflector based secondary concentrator of claim 1, wherein the plurality of layers of the one-dimensional photonic crystal coating respectively form different omni-directional photonic bandgaps, and the omni-directional photonic bandgaps of the one-dimensional photonic crystal coating overlap each other.
5. The photonic crystal omni-directional mirror based secondary concentrator of claim 1, wherein the high index material is MgF2The low refractive index material is TiO2。
6. The photonic crystal omni-directional mirror based secondary concentrator of claim 5, wherein MgF in the plurality of tiers2And TiO2A filling ratio of between 0.2 and 0.6, wherein the filling ratio is d (TiO)2):(d(TiO2)+d(MgF2) D) is the thickness of the material; the number of the crystal lattice periods of the layers is 13, 14 or 15, the crystal lattice constant of the first layer is 138nm, and the relation between the lattice constants of the (i + 1) th layer and the ith layer satisfies di+1:di1.01:1 to 1.2:1, wherein the lattice constant is MgF2And TiO2The sum of the thicknesses of (a) and (b).
7. The photonic crystal omni-directional mirror based secondary concentrator of claim 6, wherein MgF in the plurality of tiers2And TiO2Filling ratio1/3, the number of lattice cycles of the delamination is 14, and the lattice constant relationship between the i +1 th delamination and the i-th delamination satisfies di+1:di＝1.15:1。
8. The photonic crystal omni directional reflector based secondary concentrator of claim 1, wherein the substrate comprises sidewalls for reflecting light, the sidewalls enclosing an inlet and an outlet for light to enter and exit, the inlet being larger in size than the outlet; the side wall of the substrate is enclosed to form a frustum pyramid or a revolving body.
9. A concentrated photovoltaic system, comprising a secondary concentrator based on a photonic crystal omnidirectional reflector as claimed in any one of claims 1 to 8, further comprising a concentrating cell and a fresnel lens.
10. The concentrating photovoltaic system of claim 9, wherein the fresnel lens acts as a primary concentrator, and an outlet face of the secondary concentrator is connected to the concentrating cell.
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