A double-layer fluorescent solar collector

Abstract

This invention belongs to the field of optical element technology, specifically disclosing a double-layer fluorescent solar collector. The collector includes a fluorescent layer, a lossless waveguide layer, an asymmetric light transmission nanostructure layer disposed between the fluorescent layer and the lossless waveguide layer, and a reflective bottom surface at the bottom of the lossless waveguide layer. This invention utilizes the asymmetric light transmission nanostructure layer to promote the transmission of fluorescent photons to the lossless waveguide layer and prevent them from returning to the fluorescent layer, significantly reducing reabsorption loss. Simultaneously, the scattering effect of the asymmetric light transmission nanostructure layer alters the photon propagation angle, helping more solar photons to propagate to the side of the collector for absorption, thereby improving optical efficiency.

Description

Technical Field

[0001] This invention belongs to the field of optical element technology and relates to a double-layer fluorescent solar concentrator. Specifically, it relates to a double-layer fluorescent solar concentrator having a fluorescent layer, an asymmetric light transmission nanostructure layer, a lossless waveguide layer, and a bottom reflective surface of the waveguide layer. Background Technology

[0002] Fluorescent solar concentrators (LSCs), as core photovoltaic devices that can be integrated into building surfaces, are made of transparent waveguide plates doped or coated with fluorescent materials. LSCs absorb sunlight and emit fluorescence through the fluorescent material, which is then transmitted to edge photovoltaic cells via total internal reflection within the waveguide for photoelectric conversion. LSCs utilize the principle of emitting light through fluorescent materials and collecting light through waveguides, enabling them to concentrate both diffuse and direct light. Therefore, they do not require complex solar tracking systems and have broad application prospects in building-integrated photovoltaics (BIPV), providing an effective way to solve problems such as space constraints and poor building compatibility in urban renewable energy applications.

[0003] Since the concept of fluorescent solar collectors was proposed in 1976, their structure and material systems have been continuously optimized, but low optical efficiency remains a core bottleneck restricting their commercial application. The causes of low optical efficiency are diverse. Besides poor compatibility between the waveguide substrate and the fluorescent object during fabrication, the main optical losses are fluorescence reabsorption loss and surface escape cone loss. Surface escape cone loss occurs when the fluorescence emission angle is smaller than the total internal reflection angle of the surface, causing photons to directly transmit into the air. Reabsorption loss, on the other hand, is caused by the overlap between the absorption spectrum and fluorescence spectrum of the fluorescent material. Reabsorbed photons may disappear due to non-radiative attenuation or be lost again through the surface escape cone.

[0004] To reduce reabsorption loss, existing technologies often employ material modification strategies that increase the Stokes shift of fluorescent materials. However, this method suffers from drawbacks such as poor versatility and limited absorption efficiency, making it difficult to simultaneously meet the dual requirements of high absorption and low reabsorption. Regarding structural optimization, researchers have proposed various schemes, such as those in the literature: Giebink, N., Wiederrecht, G. & Wasielewski, M. Resonance-shifting to circumvent reabsorption loss inluminescent solar concentrators. Nature Photon5,694–701 (2011). https: / / doi.org / 10.1038 / nphoton.2011.236 proposed a method to create a resonant shift by changing the thickness of the fluorescent layer, so that the fluorescence entering the waveguide layer after emission does not return to the fluorescent layer, thus reducing the reabsorption loss. However, this method requires extremely high precision control of the fluorescent layer thickness, and even a small deviation can cause the resonance effect to fail, making it difficult to stably replicate in actual fabrication. For example, the literature Zohrabi R, Ehsani‐Tabar, Sahar, Esmaeili AH, et al. Monte Carlo Modeling of a High‐Efficiency Tandem Luminescent Solar Concentrator Containing a Polarization Volume Grating Layer[J]. Advanced Photonics Research, 2024, 5(12).DOI:10.1002 / adpr.202400054 proposes a fluorescent layer / air gap / waveguide layer / polarimeter grating structure. The polarimeter grating, which is composed of cholesteric liquid crystal, collects the fluorescent-guided side that escapes from the fluorescent layer, thus reducing reabsorption loss. However, the assembly of the multilayer heterostructure is difficult. Problems such as the precise control of the air gap and the interface compatibility between the polarimeter grating and the waveguide layer will increase the fabrication cost and process complexity, which is not conducive to large-scale production.

[0005] In recent years, nanostructures with broadband asymmetric light transmission properties have been introduced onto the surface of light-sensitive solar cells (LSCs). The Woods-Rayleigh anomalous light refraction (WRA) allows sunlight to enter the LSC while reducing the amount of light escaping the surface, thus enhancing sunlight collection. However, introducing broadband asymmetric light transmission structures onto the LSC surface also causes fluorescence to return to the structure, significantly increasing the probability of fluorescence photons being reabsorbed and lost. Currently, no work has been done to design asymmetric light transmission structures to achieve unidirectional transmission of fluorescence photons and reduce reabsorption losses. Furthermore, the performance of traditional planar LSCs containing only a single fluorescent layer is highly dependent on phosphor parameters; even small fluctuations in fluorescence quantum yield, concentration, and Stokes shift can lead to a significant decrease in optical efficiency, limiting their adaptability to different material systems.

[0006] Therefore, developing a fluorescent solar collector structure that is simple in structure, feasible in fabrication, can simultaneously and efficiently suppress reabsorption loss, and has good robustness to phosphor parameters is of great significance for improving the optical efficiency of LSC and promoting its large-scale application in building-integrated photovoltaic systems. Summary of the Invention

[0007] The purpose of this invention is to overcome the technical bottlenecks of traditional fluorescent solar collectors, such as low optical efficiency, significant reabsorption loss, and strong dependence on phosphor parameters. It provides a bilayer composite structure based on asymmetric light transmission nanostructures, which significantly reduces fluorescence reabsorption loss, improves the optical efficiency of fluorescent solar collectors, and broadens the phosphor compatibility range, thereby comprehensively improving the overall performance of the collector.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] A double-layer fluorescent solar collector, such as Figure 1 The diagram shown is a structural schematic of the dual-layer fluorescent solar collector of the present invention. The dual-layer fluorescent solar collector of the present invention is a dual-layer fluorescent solar collector based on an asymmetric light transmission nanostructure. From top to bottom, it includes a fluorescent layer 1, an asymmetric light transmission nanostructure layer 2, a lossless waveguide layer 3, and a reflective bottom surface 4, which are tightly attached from top to bottom.

[0010] The fluorescent layer 1 is composed of a transparent matrix 6 and phosphors 5 randomly and uniformly distributed inside. The phosphor 5 is made of cesium lead bromine (CsPbBr3) quantum dots. CsPbBr3 quantum dots are materials with high quantum yield and stable photoluminescence properties. The transparent matrix 6 is a transparent polymer material with a refractive index between 1.4 and 1.5 in the 300-700 nm wavelength range, and has good compatibility with the luminescent quantum dots.

[0011] The asymmetric light transmission nanostructure layer 2 is made of a dielectric material with a refractive index of 2-3, and the asymmetric light transmission nanostructure layer is an array of trapezoidal nanounits. Each trapezoidal nanounit is a truncated pyramid structure with both its upper and lower bases being squares. Figure 2 As shown, the dimensions of the trapezoidal nanostructure range as follows: upper base length a = 100~200nm, lower base length b = 225~325nm, height h = 225~325nm, and repeating unit period p = 325~375nm. The trapezoidal nanounit array designed in this invention has an asymmetric optical transmission bandwidth where the short cutoff wavelength is the same as the shortest fluorescence wavelength of the quantum dot, and the long cutoff wavelength is greater than the longest fluorescence emission wavelength of the quantum dot. Within the fluorescence emission band, the direction from the fluorescent layer to the lossless waveguide layer is considered forward, and the direction from the lossless waveguide layer to the fluorescent layer is considered reverse. The forward and reverse transmittance exhibit significant asymmetry and maintains stable asymmetric transmission characteristics across different incident angle ranges.

[0012] The material used to prepare the non-destructive waveguide layer 3 is a light-transmitting polymer material with a transmittance of ≥80% in the 300~700nm band and a refractive index in the range of 1.5~1.6, and the refractive index of the non-destructive waveguide layer is higher than that of the transparent matrix 6.

[0013] The reflective bottom surface 4 is a thin film of metal material, which is used to completely reflect the photons propagating downward in the lossless waveguide layer 3 back into the lossless waveguide layer 3, and avoid photon leakage at the bottom.

[0014] Preferably, the transparent polymer material of the transparent matrix 6 is polyvinylidene fluoride (PVDF), and more preferably, the thickness of the fluorescent layer is 0.01~0.3 cm.

[0015] Preferably, the concentration range of phosphor 5 in the transparent matrix 6 is 10. -5 ~0.1 mol / L, the quantum yield of the phosphor is 50%~80%.

[0016] Preferably, the dielectric material of the asymmetric light transmission nanostructure layer 2 is any one of red quartz TiO2, zinc sulfide ZnS, or zirconium oxide ZrO2, for example, red quartz TiO2 has a refractive index of 2.75.

[0017] Preferably, the light-transmitting polymer material of the non-destructive waveguide layer 3 is polycarbonate (PC) or polystyrene (PS). These two materials not only have excellent optical transparency, but also high mechanical strength and good thermal stability. More preferably, the thickness of the non-destructive waveguide layer 3 is in the range of 0.1~1cm.

[0018] Preferably, the metal material of the reflective bottom surface 4 is silver (Ag) or aluminum (Al); more preferably, the thickness of the reflective bottom surface 4 is 200 nm.

[0019] Compared to existing technologies, the asymmetric light transmission nanostructure layer designed in this invention is placed between the fluorescent layer and the waveguide layer. The unidirectional transmission characteristics of the quantum dot fluorescence emission band allow fluorescent photons to enter the waveguide layer from the fluorescent layer in the forward direction, while preventing them from returning to the fluorescent layer in the reverse direction. This structurally cuts off the fluorescence reabsorption path and significantly reduces reabsorption loss.

[0020] The asymmetric light transmission nanostructure layer reduces reabsorption loss while having a strong scattering effect on vertically incident photons, changing the photon motion angle and helping more solar photons to be transmitted to the side of the LSC for collection, thereby improving optical efficiency.

[0021] The light collection efficiency of this invention is 10 -5 It is insensitive to parameters such as phosphor concentration, quantum yield and phosphor layer thickness in the range of ~0.1 mol / L, and can maintain high light collection efficiency under a wide range of phosphor performance conditions. It does not need to rely on high-performance phosphors, thus broadening the range of phosphor compatibility. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a double-layer fluorescent solar collector according to the present invention;

[0023] Figure 2 This is a schematic diagram of a trapezoidal nanostructure.

[0024] Figure 3 This is a schematic diagram showing the transmittance of the trapezoidal nanostructures in Examples 1, 2, and 3 under vertical incidence.

[0025] Figure 4 This is a schematic diagram of the transmission scattering angle distribution of the trapezoidal nanostructures in Examples 1, 2, and 3;

[0026] Figure 5 This is a schematic diagram of the reflection and scattering angle distribution of the trapezoidal nanostructures in Examples 1, 2, and 3;

[0027] Figure 6 This is a flowchart of a Monte Carlo ray tracing simulation program.

[0028] Among them, 1: fluorescent layer; 2: asymmetric light transmission nanostructure layer; 3: non-destructive waveguide layer; 4: reflective bottom surface; 5: phosphor; 6: transparent matrix. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] In the following embodiments, the fluorescent layer 1 uses cesium lead bromine (CsPbBr3) quantum dots as the phosphor material 5, with a fluorescence emission band of 490~550nm and a fluorescence emission peak of 520nm; polyvinylidene fluoride (PVDF) is used as the transparent matrix material 6, and the refractive index of the transparent matrix 6 layer is 1.42.

[0031] In the following embodiments, the material of the non-destructive waveguide layer 3 is polycarbonate (PC), and the refractive index of the non-destructive waveguide layer 3 is 1.6.

[0032] In the following embodiments, silver (Ag) is selected as the metal thin film material for the reflective bottom surface 4.

[0033] In the following embodiments, the asymmetric light transmission nanostructure layer 2 is selected as the trapezoidal nanostructure material, which is red crystal TiO2.

[0034] Based on the Woods-Rayleigh anomaly WRA theory, the forward and reverse propagation cutoff wavelengths satisfy the formula λ. F =p×n S (1+sinθ i ), λ B =p×n U (1+sinθ i ), where n S and n Uθ represents the refractive index of the material after light propagates forward and backward through the asymmetric light transmission nanostructure layer, respectively, referring to the lossless waveguide layer 3 and the transparent matrix 6 material. i λ is the angle of incidence of the incident light. F and λ B The difference between these values ​​represents the wavelength range or bandwidth of asymmetric transmission. By adjusting the repeating unit period p and the trapezoidal structure size, asymmetric optical transmission within the fluorescence emission range of 490–550 nm for CsPbBr3 quantum dots can be achieved.

[0035] In the following embodiments, the overall horizontal dimensions of the fluorescent solar collector are 10cm × 10cm.

[0036] Example 1

[0037] In this embodiment, the thickness of the transparent matrix 6 of the fluorescent layer 1 is 0.2 cm, and the thickness of the lossless waveguide layer 3 is 0.2 cm. In this embodiment, the concentration of the phosphor 5 is 5 × 10⁻⁶. -5 The asymmetric light transmission nanostructure layer 2 has a quantum yield of 76.8% and an upper base length of a=150nm, a lower base length of b=275nm, a height of h=275nm, and a repeating unit period of p=350nm.

[0038] Comparative Example 1

[0039] Comparative Example 1 uses only a single-layer fluorescent layer structure and a reflective bottom surface. Its transparent matrix thickness is 0.4 cm, the same as the collector size in Example 1. The phosphor concentration and quantum yield are also the same as in Example 1. The only difference is that Comparative Example 1 does not introduce a double-layer structure, i.e., a fluorescent layer and a lossless waveguide layer, nor does it introduce an asymmetric light transmission nanostructure layer. The number of phosphors in Comparative Example 1 is twice that in Example 1.

[0040] Example 2

[0041] In this second embodiment, the dimensions of the fluorescent solar collector and the asymmetric light transmission nanostructure layer are the same as in the first embodiment, and the quantum yield of the phosphor is also the same. The only difference is that the concentration of phosphor 5 is reduced to 2 × 10⁻⁶. -5 mol / L.

[0042] Comparative Example 2

[0043] The only difference between the structure of Comparative Example 2 and Comparative Example 1 is that the phosphor concentration of Comparative Example 2 is reduced to 2 × 10⁻⁶. -5 mol / L.

[0044] Example 3

[0045] In this embodiment, the size of the fluorescent solar collector and the size of the asymmetric light transmission nanostructure layer are similar to those in the previous embodiment, and the concentration of the phosphor is also the same. The difference is that the thickness of the fluorescent layer 1 in the double-layer structure is reduced to 0.1 cm, the thickness of the lossless waveguide layer 3 is increased to 0.3 cm, and the quantum yield of the phosphor is selectively reduced to 70%.

[0046] Comparative Example 3

[0047] The structure of Comparative Example 3 is the same as that of Comparative Example 1. The difference lies in the reduction of the quantum yield of the phosphor to 70%.

[0048] Example 4

[0049] In this embodiment, the structure of the light collector and the concentration and quantum yield of the phosphor are the same as in Example 1. The only difference is that the parameters of the asymmetric light transmission nanostructure layer are adjusted. In the asymmetric light transmission nanostructure layer 2, the upper base length a=125nm, the lower base length b=300nm, the height h=300nm, and the repeating unit period p=340nm of the trapezoidal nanostructure.

[0050] Comparative Example 4

[0051] In this comparative example, the structure of the light collector and the concentration and quantum yield of the phosphor are the same as in Example 1. The difference lies in the adjustment of the parameters of the trapezoidal nanostructure. In the asymmetric light transmission nanostructure layer 2, the upper base length a = 25 nm, the lower base length b = 100 nm, the height h = 500 nm, and the repeating unit period p = 400 nm.

[0052] To quantitatively evaluate the performance advantages of this invention compared to traditional structures, corresponding comparative examples one, two, three, and four were set up for comparison with the above embodiments one, two, three, and four. Each comparative example had the same phosphor conditions as the corresponding embodiment, i.e., the same concentration and the same quantum yield. Among them, comparative examples one to three were traditional planar LSC structures containing only a single-layer phosphor layer and a bottom reflective surface, without the asymmetric light transmission nanostructure layer and the lossless waveguide layer. Comparative example four was completely consistent with the phosphor conditions and double-layer structure of embodiment one, i.e., phosphor layer + lossless waveguide layer and reflective bottom surface, except that the trapezoidal nanostructure parameters exceeded the limits of this invention, and were used to verify the rationality of the trapezoidal nanostructure parameter design.

[0053] like Figure 3 The image shows the forward and reverse transmission spectra of the trapezoidal nanostructures described in Examples 1, 2, and 3 under vertical incidence. The relevant data were determined by simulation using FDTD Solutions, a software based on the finite-difference time-domain method. Figure 3This indicates that the trapezoidal nanostructure exhibits very significant asymmetric light transmission characteristics within the selected fluorescence emission band of CsPbBr3 quantum dots. It should be noted that the asymmetric light transmission nanostructure layer is identical in Examples 1, 2, and 3, therefore the reflectivity is the same. The reflectivity is only related to the size of the asymmetric light transmission nanostructure layer, and this data is simulated, not from actual samples.

[0054] like Figure 4 The figure shows the scattering angle distribution characteristics of the trapezoidal nanostructures in Examples 1, 2, and 3. The relevant data were determined by calculating the Poynting vector using FDTD. Specifically, Figure 4 and Figure 5 The probability distributions of the transmission and reflection angles of the trapezoidal nanostructure at an incident angle of 0° are shown at a fluorescence emission peak of 520 nm for CsPbBr3 quantum dots. This distribution indicates that the trapezoidal nanostructure exhibits strong scattering of perpendicularly incident photons, with the scattering angles distributed over a wide range of probabilities. This significantly increases the optical path length of incident solar photons within the LSC, increasing the probability of absorption by the CsPbBr3 quantum dots, while simultaneously facilitating the transmission of unabsorbed solar photons within the waveguide for direct collection by the side-mounted solar cells.

[0055] The transmittance and scattering angle data obtained from the FDTD Solutions software simulation were imported into a Monte Carlo ray tracing simulation program written in MATLAB. Specifically, FDTD was used to perform numerical simulation to obtain the transmittance spectrum and scattering angle distribution of the collector's nanostructure. The data was then exported as a database and input into the Monte Carlo ray tracing simulation system. The system analyzed the absorptivity, escape rate, reabsorption rate, and optical efficiency within the collector. The flowchart of the Monte Carlo ray tracing simulation program is as follows: Figure 6 As shown. Each embodiment is modeled using its own structural parameters. Simultaneously, a light collector containing only the fluorescent layer and reflective bottom surface of the corresponding embodiment is constructed as a control device. Simulations are performed under the same light source and the same number of incident photons. Key performance parameters are statistically analyzed and calculated. Table 1 below shows a comparison of the performance parameters of Embodiments 1, 2, 3, and 4 with those of Comparative Examples 1, 2, 3, and 4.

[0056] Table 1:

[0057]

[0058] As can be seen from the reabsorption loss rate and light collection efficiency of Example 1 and Comparative Example 1, the asymmetric light transmission nanostructure layer proposed in this invention significantly reduces the reabsorption loss from 11.28% to 5.54%, thereby improving the optical efficiency from 5.04% to 6.55%.

[0059] In Example 2 and Comparative Example 2, the concentration of quantum dots was lower than that in Example 1 and Comparative Example 1. In the comparative example without the asymmetric light transmission nanostructure layer, the reduction in quantum dot concentration resulted in a decrease in reabsorption loss, which remained at a relatively high level, from 11.28% to 3.98%, while the optical efficiency decreased significantly, from 5.04% to 4.36%. However, in the light collector proposed in this invention, the reduction in quantum dot concentration resulted in a significant decrease in reabsorption loss, from 5.54% to 1.60%, while the optical efficiency remained essentially unchanged, increasing from 6.55% to 6.57%. The reabsorption loss was far lower than that in Comparative Example 2 under the corresponding conditions, fully demonstrating the performance optimization effect of the asymmetric light transmission nanostructure layer.

[0060] In Example 3 and Comparative Example 3, the quantum yield of the quantum dots was slightly lower than that of Example 1 and Comparative Example 1. In the comparative example without the asymmetric light transmission nanostructure layer, the decrease in quantum yield resulted in a reduction in both reabsorption loss and optical efficiency in Comparative Example 3 compared to Comparative Example 1. However, in the light collector proposed in this invention, because the asymmetric light transmission nanostructure layer confines the fluorescent photons within the waveguide layer, the decrease in quantum yield resulted in a significant reduction in reabsorption loss in Example 3 compared to Comparative Example 3, decreasing from 10.52% to 2.19%, while the optical efficiency was significantly improved, increasing from 4.38% to 6.92%.

[0061] A comparison of Examples 1-3 and Comparative Examples 1-3 reveals a significant improvement in optical efficiency in the light collector proposed in this invention. Furthermore, the variation in quantum dot performance has a relatively small impact on optical efficiency. This is because the asymmetric light transmission nanostructure layer can block fluorescence from returning to the fluorescence layer, thereby reducing reabsorption loss. Simultaneously, the asymmetric light transmission nanostructure layer can collect solar photons through scattering, while the planar structure in the comparative examples cannot collect solar photons, thus contributing significantly to optical efficiency.

[0062] Compared to Example 1, Example 4 adjusted the parameters of the asymmetric light transmission nanostructure layer, resulting in a non-optimal structure. However, it still retains asymmetric transmission characteristics, thus reducing the reabsorption rate from 11.28% to 5.68% compared to Comparative Example 1. Consequently, the optical efficiency is lower than that of Example 1, but still better than the 5.56% of Comparative Example 1.

[0063] Comparative Example 4 and Example 1 share the same phosphor conditions and bilayer structure. Although the reabsorption rate of Comparative Example 4 is lower than that of Comparative Example 1, this result is not due to the directional confinement of fluorescent photons by asymmetric light transmission to suppress reabsorption, but rather to a significant reduction in the number of photons participating in reabsorption due to its own low absorption efficiency. This is a case of "passive loss reduction at the expense of core absorption performance," which directly leads to its low optical efficiency. Furthermore, it lacks a strong ability to collect solar photons that have not been absorbed by the phosphor. Ultimately, the optical efficiency of Comparative Example 4 is only 3.18%, significantly lower than that of Example 1 and Comparative Example 1. This fully demonstrates that only within the range of trapezoidal nanostructure parameters defined in this invention can efficient suppression of reabsorption loss and improvement of optical efficiency be achieved simultaneously, while structural designs outside this range cannot achieve the expected technical effects.

[0064] The above comparative data fully demonstrates that this invention, by introducing asymmetric light transmission nanostructures with specific parameter ranges to construct a bilayer composite system, can systematically solve the problems of high reabsorption loss, low optical efficiency, and sensitivity to phosphor parameters in traditional flat-panel fluorescent solar collectors. Furthermore, the parameter limitation of the trapezoidal nanostructure is key to achieving the aforementioned technical effects; structural designs exceeding this parameter range cannot achieve the expected performance. This invention achieves all the expected technical effects, significantly improving the overall performance and application potential of fluorescent solar collectors.

[0065] The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. The understanding of this specification should be based on those skilled in the art. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still make modifications or equivalent substitutions to the present invention. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A double-layer fluorescent solar collector, characterized in that, The dual-layer fluorescent solar collector comprises, from top to bottom, a fluorescent layer, an asymmetric light transmission nanostructure layer, a non-destructive waveguide layer, and a reflective bottom surface, which are tightly bonded together from top to bottom. The fluorescent layer consists of a transparent matrix and phosphors randomly and uniformly distributed inside. The phosphors are made of cesium lead bromine (CsPbBr3) quantum dots, and the transparent matrix is ​​a transparent polymer material with a refractive index between 1.4 and 1.5 in the 300-700 nm wavelength range. The asymmetric light transmission nanostructure layer is made of a dielectric material with a refractive index of 2 to 3, and the asymmetric light transmission nanostructure layer is an array of trapezoidal nanounits. The trapezoidal nanounits are truncated square structures with both the upper and lower bases being square. The size range of the trapezoidal nanostructures is: upper base length a = 100~200 nm, lower base length b = 225~325 nm, height h = 225~325 nm, and repeating unit period p = 325~375 nm. The material used to prepare the non-destructive waveguide layer is a light-transmitting polymer material with a transmittance of ≥80% in the 300~700nm band and a refractive index in the range of 1.5~1.6, and the refractive index of the non-destructive waveguide layer is higher than that of the transparent matrix. The reflective bottom surface is a thin film of metallic material.

2. The double-layer fluorescent solar collector as described in claim 1, characterized in that, The transparent polymer material of the transparent matrix is ​​polyvinylidene fluoride (PVDF).

3. A double-layer fluorescent solar collector as described in claim 2, characterized in that, The thickness of the fluorescent layer is 0.01~0.3 cm.

4. A double-layer fluorescent solar collector as described in claim 1, characterized in that, The concentration range of the phosphor in the transparent matrix is ​​10. -5 ~0.1 mol / L, the quantum yield of the phosphor is 50%~80%.

5. A double-layer fluorescent solar collector as described in claim 1, characterized in that, The dielectric material of the asymmetric light transmission nanostructure layer is any one of red crystal TiO2, zinc sulfide ZnS, or zirconium oxide ZrO2.

6. A double-layer fluorescent solar collector as described in claim 1, characterized in that, The light-transmitting polymer material of the non-destructive waveguide layer is polycarbonate (PC) or polystyrene (PS).

7. A double-layer fluorescent solar collector as described in claim 6, characterized in that, The thickness of the non-destructive waveguide layer ranges from 0.1 to 1 cm.

8. A double-layer fluorescent solar collector as described in claim 1, characterized in that, The metal material of the reflective bottom surface is silver (Ag) or aluminum (Al).

9. A double-layer fluorescent solar collector as described in claim 1, characterized in that, The thickness of the reflective bottom surface is 200 nm.

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