Thermophotovoltaic device based on hyperbolic metamaterial nanowire array and manufacturing method thereof

Abstract

The present invention discloses a thermophotovoltaic device based on a hyperbolic metamaterial nanowire array and a manufacturing method thereof, which can significantly improve the thermoelectric conversion performance. The present invention comprises the following steps: 1) determining the filling rate of the hyperbolic nanowire array according to the radiant heat flux and the limitation of the nanowire structure parameters; 2) designing the structural dimensions of the nanowire array according to the process limitation; 3) constructing a near-field thermophotovoltaic device according to the optimized structural parameters; 4) obtaining the thermoelectric conversion power performance of the near-field thermophotovoltaic device based on the hyperbolic metamaterial by using finite element analysis. The present invention combines the hyperbolic nanowire array structure with the near-field thermophotovoltaic device, and regulates the frequency of the radiant thermal photons through parameter optimization to match the band gap width of the semiconductor of the battery layer. The nanowire array structure can effectively improve the absorption capacity of the thermal photons. The present invention is compatible with the existing semiconductor manufacturing processes and has broad applications in aspects such as the recovery and utilization of industrial waste heat.

Description

Technical Field

[0001] The present invention belongs to the field of near-field thermoelectric conversion devices, and particularly relates to a thermophotovoltaic device based on a hyperbolic metamaterial nanowire array and a manufacturing method thereof. Background Art

[0002] A near-field thermophotovoltaic device is a fully solid-state waste heat recovery technology that converts thermal energy into electrical energy. Compared with far-field thermophotovoltaics, near-field thermophotovoltaics can greatly increase the radiative heat flux between a heat source and a cold end by utilizing the tunneling effect of evanescent waves. However, it is still limited by the non-adjustability of the radiation spectrum of traditional natural materials, making it impossible for radiative heat photons to be effectively utilized by the battery layer.

[0003] Hyperbolic metamaterials are a class of artificial composite structures with hyperbolic properties composed of sub-wavelength structures as basic units. They support the propagation of photons with a large transverse wave vector and have a high local surface state density. They can not only greatly enhance the radiative heat flux in the near field and enhance the thermoelectric conversion power, but also can be frequency-tuned by setting the structural parameters to match the frequency of the bandgap width of the semiconductor material of the thermophotovoltaic cell, so as to effectively utilize radiative heat photons and greatly improve the thermoelectric conversion efficiency. Therefore, the near-field thermophotovoltaic device based on hyperbolic metamaterials provides a very effective solution to the current problems. In addition, a thermophotovoltaic cell with a nanowire array structure has a larger receiving area for heat photons, effectively improving the absorption ability of radiative heat photons. Summary of the Invention

[0004] The purpose of the present invention is to provide a design method for a near-field thermophotovoltaic device based on hyperbolic metamaterials.

[0005] The technical solution adopted by the present invention to solve its technical problems is as follows:

[0006] The present invention first provides a near-field thermophotovoltaic device based on hyperbolic metamaterials, including a heat source, a emitter, a battery layer, and a cold end; the emitter and the battery layer are obtained by etching on a semiconductor substrate,

[0007] The heat source and the cold end on the back are respectively pasted on a material with good thermal conductivity and a thermoelectric cooler (TEC) with thermal conductive glue; the emitter is a hyperbolic metamaterial, and there is a spacing between the emitter and the battery layer that enhances the radiative heat flux by utilizing the near-field evanescent wave tunneling effect; the hyperbolic metamaterial has a dielectric constant in the direction perpendicular to the optical axis and a dielectric constant in the direction parallel to the optical axis, and the product of the dielectric constant in the direction perpendicular to the optical axis and the dielectric constant in the direction parallel to the optical axis of the hyperbolic metamaterial is negative.

[0008] The present invention also provides a manufacturing method for the above near-field thermophotovoltaic device, including the following steps:

[0009] Step 1): Build an initial model of the near-field thermophotovoltaic device according to the structure of the near-field thermophotovoltaic device;

[0010] Step 2): Determine the filling rates of the nanowire arrays of the emitter and the battery layer in the near-field thermophotovoltaic device by using the effective medium theory according to the magnitude of the radiative heat flux of the initial model of the near-field thermophotovoltaic device and the nanowire structure parameter constraints;

[0011] Step 3): Adjust the filling rates of the nanowire arrays of the emitter and the battery layer in the initial model of the near-field thermophotovoltaic device to the filling rates determined in Step 2), and determine the thicknesses of the nanowire arrays of the emitter and the battery layer according to the aspect ratio constraints of nanowire processing;

[0012] Step 4): Fabricate the near-field thermophotovoltaic device according to the filling rate determined in Step 2) and the thicknesses determined in Step 3).

[0013] As a preferred solution of the present invention, the specific method for determining the filling rates of the nanowire arrays of the emitter and the battery layer in the near-field thermophotovoltaic device in Step 2) is as follows: By using the effective medium theory, the dielectric constant ε ⊥ in the direction perpendicular to the optical axis and the dielectric constant ε || in the direction parallel to the optical axis of the hyperbolic material for constructing the emitter and the battery layer are obtained:

[0014]

[0015] ε || = 1 - f + ε i f

[0016] The dielectric constant of the hyperbolic metamaterial is related not only to the dielectric constant ε i of the material itself, but also to the material filling rate f. By changing the material filling rate, the dielectric constants in the direction perpendicular to the optical axis and the direction parallel to the optical axis are regulated;

[0017] where the temperature of the emitter is T1, the temperature of the battery layer is T2, the near-field spacing is d, the frequency of the radiative heat photons in the vacuum gap is ω, and the near-field radiative heat flux h between the emitter and the battery layer is calculated by using the fluctuating electrodynamics theory:

[0018]

[0019] where, Θ(ω, T i ) is the average energy of the harmonic oscillator with frequency ω; τ s，p (ω, k) is the transmission coefficient of the s-wave and the p-wave, expressed as:

[0020]

[0021] where, is the vacuum normal wave vector in the direction of the vertical plane, where k0 and β are the vacuum wave vector and the transverse wave vector respectively. r s，p are the Fresnel reflection coefficients of the s-wave and p-wave respectively, and their magnitudes are related to the dielectric constants of the emitter and the battery layer and the thickness of the nanowire array; fixing the thickness of the nanowire array structure, the relationship between the filling rate and the near-field radiative heat flux is obtained, and the optimal filling rate is thus obtained.

[0022] As a preferred embodiment of the present invention, in step 3), determining the thicknesses of the nanowire arrays of the emitter and the battery layer according to the aspect ratio limitation of nanowire processing specifically includes: adjusting the filling rate of the initial model of the near-field thermophotovoltaic device to the filling rate determined in step 2), and selecting an appropriate thickness according to the aspect ratio limitation of nanowire processing to maximize the near-field radiative heat flux:

[0023]

[0024] As a preferred embodiment of the present invention, step 4) specifically includes the following steps:

[0025] 4.1) Fabricate a nanowire array with appropriate unit size, thickness and filling rate as the battery layer by using etching and ion implantation processing techniques, connect leads and electrodes, and paste and cover the cold end on the back of the battery layer on the semiconductor refrigeration chip with thermal conductive adhesive;

[0026] 4.2) Fabricate a nanowire array emitter with certain hyperbolic properties by using hyperbolic metamaterials, paste the heat source on the back of the emitter with thermal conductive adhesive and a material with good thermal conductivity, and keep the emitter and the battery layer in the near-field spacing in a certain way;

[0027] 4.3) Package the components in steps 4.1) and 4.2), and select a material with thermal conductivity for packaging;

[0028] 4.4) Coat a layer of thermal grease on the side of the packaged near-field thermophotovoltaic device close to the emission end for collecting industrial waste heat;

[0029] 4.5) Detect whether the near-field thermophotovoltaic device in step 4.4) is qualified;

[0030] As a preferred embodiment of the present invention, the detection method in step 4.5) specifically includes: obtaining the carrier distribution hz(z, ω) in the thermophotovoltaic cell by using COMSOL finite element analysis, and then obtaining the thermoelectric conversion power and thermoelectric conversion efficiency of the near-field thermophotovoltaic device, so as to judge whether the near-field thermophotovoltaic device is qualified.

[0031] As a preferred embodiment of the present invention, the carrier distribution hz(z, ω) in the thermophotovoltaic cell is obtained according to the fact that the thermal photons approximately decay exponentially in the vertical direction in the nanowire battery layer:

[0032]

[0033] Where h(ω) is the heat flux spectrum on the upper surface of the battery layer, z is the vertical distance to the surface of the thermal photovoltaic cell, represents the attenuation factor of thermal photons inside the thermal photovoltaic cell layer;

[0034] The current density distribution spectrum generated in the p-region and n-region of the semiconductor material e (z, ω) and j h The relationship between (z, ω) and carrier distribution is:

[0035]

[0036]

[0037] Where e is the unit charge, D e(h) is the electron (hole) diffusion coefficient, n e(h) is the minority carrier concentration in the p(n) layer, r = a + Ln represents the radial position where the n region meets the depletion layer, and r = a represents the radial position where the p region meets the depletion layer;

[0038] The current density spectrum of the p-region and n-region is obtained by integrating the current density distribution spectrum over the corresponding area. The current density spectrum in the depletion layer can be considered to be converted from the heat flow absorbed by the depletion layer:

[0039]

[0040] hz(z0,,) and hz(0,r,ω) are the heat flux distribution spectra at the radial position r on the bottom and top surfaces of the nanowire battery layer, respectively.

[0041] As a preferred embodiment of the present invention, the thermoelectric conversion power and thermoelectric conversion efficiency of the near-field thermophotovoltaic device are obtained specifically as follows: the thermoelectric conversion power of the thermophotovoltaic cell is obtained by integrating the current density spectra of the p-region, n-region and depletion layer with respect to frequency and summing them; the thermoelectric conversion power is compared with the radiant heat flow flowing into the thermophotovoltaic cell layer to obtain the thermoelectric conversion efficiency of the near-field thermophotovoltaic device.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] This invention enhances the near-field heat flow between the heat source and the thermophotovoltaic cell by designing an artificial microstructured metamaterial and selecting appropriate structural parameters. Furthermore, by leveraging the hyperbolic properties of the nanowire array metamaterial, the thermal radiation spectrum can be regulated, significantly increasing the proportion of thermal photons with frequencies greater than the bandgap of the thermophotovoltaic cell's semiconductor material, effectively improving the thermophotovoltaic cell's utilization efficiency of radiated thermal photons.

[0044] The thermophotovoltaic cell of the present invention adopts a nanowire array structure, which has a larger thermophoton receiving area compared with the traditional multi-layer film structure, effectively improving the absorption ability of radiative thermophotons. Description of the Drawings

[0045] Figure 1 It is a schematic structural diagram of a hyperbolic nanowire array.

[0046] Figure 2 It is the dielectric constant spectra of tungsten nanowire arrays in the direction perpendicular to the optical axis and parallel to the optical axis.

[0047] Figure 3 It is a schematic diagram of the evanescent wave tunneling effect of a near-field thermophotovoltaic device.

[0048] Figure 4 It is the variation of the near-field radiative heat flux with the filling rate of the nanowire array.

[0049] Figure 5 It is the variation of the near-field radiative heat flux with the thickness of the nanowire array.

[0050] Figure 6 It is a schematic diagram of a near-field thermophotovoltaic device based on hyperbolic metamaterials.

[0051] Figure 7 It is the spatial distribution spectrum of thermophotons in the thermophotovoltaic cell in the direction perpendicular to the surface.

[0052] Figure 8 It is the simulation result of the carrier distribution in the n-layer and p-layer of the thermophotovoltaic cell.

[0053] Figure 9 It is the calculation result of the current density spectra in the p-layer, n-layer and depletion layer of the thermophotovoltaic cell.

[0054] Figure 10 It is a schematic diagram of a near-field thermophotovoltaic device based on a multi-layer film structure. Detailed Embodiments

[0055] The present invention will be further described and explained below in conjunction with the detailed embodiments. The embodiments are only illustrative of the present disclosure and do not delimit the scope of limitation. Without conflict, the technical features of each embodiment of the present invention can be combined accordingly.

[0056] The present invention will be further described below in conjunction with the drawings.

[0057] A near-field thermophotovoltaic device based on hyperbolic metamaterials, characterized in that it includes a heat source, a emitter, a battery layer, and a cold end; the emitter is fixed on the heat source, and the battery layer is fabricated on the cold end by etching; the emitter is a hyperbolic metamaterial, and there is a spacing between the emitter and the battery layer that enhances the radiative heat flux by using the near-field evanescent wave tunneling effect; the hyperbolic metamaterial has a dielectric constant in the direction perpendicular to the optical axis and a dielectric constant in the direction parallel to the optical axis, and the product of the dielectric constant in the direction perpendicular to the optical axis and the dielectric constant in the direction parallel to the optical axis of the hyperbolic metamaterial is negative.

[0058] In a specific embodiment of the present invention, a manufacturing method of a near-field thermophotovoltaic device based on hyperbolic metamaterials is further provided, specifically including the following steps:

[0059] Step (1), build an initial model of the near-field thermophotovoltaic device according to the structure of the near-field thermophotovoltaic device;

[0060] According to the target parameter indicators and the structural parameter limitations, use the effective medium theory to determine the filling rates of the emitter and the nanowire array of the thermophotovoltaic cell layer to maximize the radiative heat flux.

[0061] Step (2), as Figure 1 shown, is a schematic diagram of the structure of the hyperbolic nanowire array, and the nanowire filling rate f is the volume ratio of the nanowires. Figure 2 The dielectric constant spectra (ε ⊥ and ε ∥ , ε ⊥ ×ε ∥ <0) of tungsten nanowire arrays with filling rates of 0.2, 0.5, and π / 4 in the direction perpendicular to the optical axis and the direction parallel to the optical axis are given, which satisfy the hyperbolic characteristics. Such an artificial hyperbolic material emitter has a very high interfacial photon state density and can greatly enhance the near-field tunneling effect of evanescent wave thermal photons. The near-field evanescent wave tunneling effect is as Figure 3 shown, and the light wavy lines in the figure represent evanescent waves, which can be directly coupled from the emitter to the thermophotovoltaic cell. Figure 6 A schematic diagram of a near-field thermophotovoltaic device based on hyperbolic metamaterials is given. In the figure, the temperature of the emitter is T1, the temperature of the thermophotovoltaic cell is T2, the filling rates and thicknesses of the nanowire arrays of the heat source and the thermophotovoltaic cell are the same, which are f and L respectively, and the near-field spacing is d. The near-field radiative heat flux h between the heat source and the thermophotovoltaic cell calculated by using the theory of fluctuating electrodynamics is:

[0062]

[0063] The variation of the near-field heat flux with the filling rate is as Figure 4 shown. For a nanowire array structure with a circular cross-section, the filling rate range is 0 < f < π / 4. It can be seen from the figure that π / 4 is the optimal filling rate value.

[0064] Step (3), according to the limitations of the nanowire manufacturing process, design the thickness of the nanowire arrays of the emitter and the thermophotovoltaic cell layer at a certain filling rate, so as to achieve the maximum radiative heat flux between the heat source and the thermophotovoltaic cell. Adjust the filling rate of the initial model of the near-field thermophotovoltaic device to the filling rate determined in step (2), and select an appropriate thickness according to the aspect ratio limitation of nanowire processing to maximize the near-field radiative heat flux; in this embodiment, the filling rate f = π / 4 is selected, and the relationship between the near-field heat flux and the thickness of the nanowire array is obtained according to formula (1) as Figure 5 shown. It can be seen from this that 1500 nm is selected as the optimal thickness of the nanowire array.

[0065] Step (4), use the processing techniques of etching and ion implantation to fabricate a nanowire array with appropriate unit size, thickness and filling rate as the cell layer, connect the leads and electrodes, and paste the cold end on the back of the cell layer to a semiconductor refrigeration chip with thermal conductive adhesive; use hyperbolic metamaterials to fabricate a nanowire array emitter with certain hyperbolic characteristics, use thermal conductive adhesive to paste the heat source on the back of the emitter to a material with good thermal conductivity, and keep the emitter and the cell layer at a near-field spacing in a certain way; encapsulate the cell layer, the cold end, the nanowire array emitter and the heat source with copper; coat a layer of thermal grease on the side of the packaged near-field thermophotovoltaic device close to the emission end; and detect whether the near-field thermophotovoltaic device is qualified.

[0066] In a specific embodiment of the present invention, the thermoelectric conversion efficiency of the near-field thermophotovoltaic device is specifically detected as follows: First, according to the magnitude of the radiative heat flux transmitted through the gap between the heat source and the thermophotovoltaic cell, obtain the spatial distribution and frequency distribution of the thermal photons in the thermophotovoltaic cell along the vertical surface direction. According to the optimization of the filling rate and the thickness of the nanowire array, select a hyperbolic nanowire array with a filling rate of π / 4 and a thickness of 1500 nm as the optimal structure. Since the thermal photons in the thermophotovoltaic cell approximately decay exponentially along the vertical direction, as Figure 7 shown, the longitudinal spatial distribution spectrum of the thermal photons in the receiving end can be obtained. In the figure, the longitudinal distance along the surface of the thermophotovoltaic cell is z, the angular frequency of the thermal photons is ω, and the white dotted line corresponds to the bandgap frequency of indium antimonide semiconductor. It can be seen that the thermal photons radiated by the optimized artificial hyperbolic structure can be concentrated above the bandgap frequency of the semiconductor and can be effectively absorbed and utilized by the thermophotovoltaic cell.

[0067] Then, according to the distribution of the thermal photons in the thermophotovoltaic cell, obtain the distribution spectrum of the carriers in the thermophotovoltaic cell through COMSOL finite element analysis. According to the diffusion equation and boundary conditions of the semiconductor, import the distribution spectrum of the thermal photons in the thermophotovoltaic cell into the partial differential equation module of COMSOL, and obtain the distribution spectrum of the carriers in the n-layer and p-layer of the thermophotovoltaic cell through finite element simulation. Among them, Figure 8 gives the frequency of 5×10 14The distribution of minority carriers in the n-layer and p-layer at [[rad / s]].

[0068] According to the relationship between the carrier distribution spectrum and the current density spectrum, the thermoelectric conversion power and thermoelectric conversion efficiency of the near-field thermophotovoltaic device are obtained. The relationship between the current density spectra generated in the semiconductor materials p-layer and n-layer of the thermophotovoltaic cell and the carrier distribution spectrum is as follows:

[0069]

[0070]

[0071] Integrating the current density distribution spectrum over the area gives the current density spectra of the p-region and n-region. The current density spectrum in the depletion layer can be considered to be converted from the heat flux absorbed in this region:

[0072]

[0073] As Figure 9 shown are the current density spectra of the p-layer, n-layer, and depletion layer, which are j e , j h and j dp .

[0074] By integrating the current density spectra of the p-layer, n-layer, and depletion layer over the frequency and summing them, the thermoelectric conversion power of the thermophotovoltaic cell is obtained as P = 1340 W. By comparing the thermoelectric conversion power P with the total radiant heat flux flowing into the thermophotovoltaic cell, the thermoelectric conversion efficiency η = 35.7% of the near-field thermophotovoltaic device can be obtained.

[0075] Figure 10 Fig. shows a schematic diagram of a traditional multi-layer film structure near-field thermophotovoltaic device. In the figure, the temperatures of the heat source and the thermophotovoltaic cell are T1 and T2 respectively, and the near-field spacing is d. Using the finite difference method to calculate the diffusion equation, the current density of the multi-layer film structure near-field thermophotovoltaic device can be obtained. After frequency integration, its thermoelectric conversion power and thermoelectric conversion efficiency are P = 141.4 W and η = 7.9% respectively. Comparing the thermoelectric conversion performances of the near-field thermophotovoltaic devices of the two structures shows the significant advantage of the near-field thermophotovoltaic cell based on hyperbolic metamaterials in improving the thermoelectric conversion performance.

[0076] The above-described embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent of the present invention. For those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A manufacturing method of a near-field thermophotovoltaic device based on hyperbolic metamaterials, characterized in that, The near-field thermophotovoltaic device includes a heat source, a emitter, a battery layer, and a cold end; the emitter and the battery layer are obtained by etching on a semiconductor substrate, and the heat source and the cold end on the back are respectively pasted on a material with good thermal conductivity and a thermoelectric cooler (TEC) using thermal conductive glue; the emitter is a hyperbolic metamaterial, and there is a spacing that enhances the radiative heat flux using the near-field evanescent wave tunneling effect between the emitter and the battery layer; the hyperbolic metamaterial has a dielectric constant in the direction perpendicular to the optical axis and a dielectric constant in the direction parallel to the optical axis, and the product of the dielectric constant in the direction perpendicular to the optical axis and the dielectric constant in the direction parallel to the optical axis of the hyperbolic metamaterial is negative; The manufacturing method of the near-field thermophotovoltaic device includes the following steps: Step 1): Build an initial model of the near-field thermophotovoltaic device according to the structure of the near-field thermophotovoltaic device; Step 2): Determine the filling ratios of the nanowire arrays of the emitter and the battery layer in the near-field thermophotovoltaic device using the effective medium theory according to the magnitude of the radiative heat flux of the initial model of the near-field thermophotovoltaic device and the nanowire structure parameter constraints; Step 3): Adjust the filling ratios of the nanowire arrays of the emitter and the battery layer in the initial model of the near-field thermophotovoltaic device to the filling ratios determined in Step 2), and determine the thicknesses of the nanowire arrays of the emitter and the battery layer according to the aspect ratio constraints of nanowire processing; Step 4): Manufacture the near-field thermophotovoltaic device according to the filling ratio determined in Step 2) and the thicknesses determined in Step 3); The specific content of Step 4) includes the following steps: 4.1) Use the processing technologies of etching and ion implantation to fabricate a nanowire array with appropriate unit size, thickness, and filling ratio as the battery layer, connect the leads and electrodes, and paste the cold end on the back of the battery layer with thermal conductive glue to cover the thermoelectric cooler; 4.2) Use a hyperbolic metamaterial to fabricate a nanowire array emitter with certain hyperbolic characteristics, use thermal conductive glue to paste the heat source on the back of the emitter to a material with good thermal conductivity, and keep the emitter and the battery layer at a near-field spacing in a certain way; 4.3) Package the components in Steps 4.1) and 4.2), and select a material with thermal conductivity during packaging; 4.4) Coat a layer of thermal grease on the side of the packaged near-field thermophotovoltaic device close to the emission end to collect industrial waste heat; 4.5) Detect whether the near-field thermophotovoltaic device in Step 4.4) is qualified; The specific detection method in Step 4.5) is: Use COMSOL finite element analysis to obtain the carrier distribution hz(z,ω) in the thermophotovoltaic cell, and then obtain the thermoelectric conversion power and thermoelectric conversion efficiency of the near-field thermophotovoltaic device, so as to judge whether the near-field thermophotovoltaic device is qualified.

2. The manufacturing method of the near-field thermophotovoltaic device according to claim 1, characterized in that In step 2), the filling ratios of the emitter and the nanowire array of the battery layer in the near-field thermophotovoltaic device are specifically determined as follows: Using the effective medium theory, the dielectric constant of the hyperbolic material that constructs the emitter and the battery layer in the direction perpendicular to the optical axis is obtained and the dielectric constant ε ‖ in the direction parallel to the optical axis: In addition to being related to the dielectric constant ε of the material itself, the dielectric constant of the hyperbolic metamaterial is also related to the filling fraction f of the material. By changing the filling fraction of the material, the dielectric constants in the direction perpendicular to the optical axis and in the direction parallel to the optical axis are regulated; i The dielectric constant of the hyperbolic metamaterial is related to the filling fraction f of the material in addition to being related to the dielectric constant ε of the material itself. By changing the filling fraction of the material, the dielectric constants in the direction perpendicular to the optical axis and in the direction parallel to the optical axis are regulated; Where the temperature of the emitter is T1, the temperature of the battery layer is T2, the near-field spacing is d, the frequency of the radiative heat photons in the vacuum gap is ω, and the near-field radiative heat flux h between the emitter and the battery layer is calculated using the theory of fluctuating electrodynamics: where, Θ(ω, T i ) is the average energy of a harmonic oscillator with frequency ω; τ s (ω, k) is the transmission coefficient of the s-wave, and τ p (ω, k) is the transmission coefficient of the p-wave, expressed as: Among them, is the vacuum normal wave vector in the direction of the vertical plane, where k0 and β are the vacuum wave vector and the transverse wave vector respectively; r j In j = s, p of r j represents the Fresnel reflection coefficient of the s-wave. When j = p, r j represents the Fresnel reflection coefficient of the p-wave; r s is the Fresnel reflection coefficient of the s-wave, r p is the Fresnel reflection coefficient of the p-wave, and its magnitude is related to the dielectric constants of the emitter and the battery layer and the thickness of the nanowire array; fixing the thickness of the nanowire array structure, the relationship between the filling rate and the near-field radiative heat flux is obtained, and the optimal filling rate is thus obtained.

3. The manufacturing method of the near-field thermophotovoltaic device according to claim 1, characterized in that, The specific method for determining the thicknesses of the nanowire arrays of the emitter and the battery layer according to the aspect ratio constraints of nanowire processing in Step 3) is: Adjust the filling ratio of the initial model of the near-field thermophotovoltaic device to the filling ratio determined in Step 2), and select an appropriate thickness according to the aspect ratio constraints of nanowire processing to maximize the near-field radiative heat flux:

4. The manufacturing method of the near-field thermophotovoltaic device according to claim 1, characterized in that, The carrier distribution hz(z, ω) in the thermophotovoltaic cell is obtained based on the fact that the thermal photons approximately decay exponentially along the vertical direction in the nanowire cell layer: Among them, h(ω) is the heat flux spectrum on the upper surface of the battery layer, and z is the longitudinal distance perpendicular to the surface of the thermophotovoltaic cell. It represents the attenuation factor of thermal photons inside the thermophotovoltaic cell layer. It represents the magnitude of the wave vector of the nanowire layer in the z direction. 1, 2, and 3 represent vacuum, nanowire layer, and substrate layer respectively. The 2 in it represents the nanowire layer. Current density distribution spectra j e (z, ω) and j h (z, ω) and the carrier distribution is as follows: where e is the unit electric charge, D e is the electron diffusion coefficient, D h is the hole diffusion coefficient, n e is the minority carrier concentration in the p-layer, n h is the minority carrier concentration in the n-layer, r = a + Ln represents the radial position where the n-region meets the depletion layer, and r = a represents the radial position where the p-region meets the depletion layer; Integrating the current density distribution spectrum over the corresponding area gives the current density spectra of the p-region and the n-region; the current density spectrum in the depletion layer is converted from the heat flux absorbed by the depletion layer: hz(z0, r, ω) and hz(0, r, ω) are the heat flux distribution spectra at the radial position r on the bottom and top surfaces of the nanowire cell layer respectively, and ω is the frequency of the radiative thermal photons in the vacuum gap.

5. The manufacturing method of the near-field thermophotovoltaic device according to claim 1, wherein, The thermoelectric conversion power and the thermoelectric conversion efficiency of the near-field thermophotovoltaic device are obtained as follows: the thermoelectric conversion power of the thermophotovoltaic cell is obtained by integrating and summing the current density spectra of the p-region, the n-region and the depletion layer over the frequency; the thermoelectric conversion efficiency of the near-field thermophotovoltaic device is obtained by taking the ratio of the thermoelectric conversion power to the radiative heat flux flowing into the thermophotovoltaic cell layer.

Images