CN104241428A - Two-dimensional silicon-based micro-nano photonic crystal solar cell - Google Patents

Abstract

The invention belongs to the technical field of solar cells, and relates to a two-dimensional silicon-based micro-nano photonic crystal solar cell. The two-dimensional silicon-based micro-nano photonic crystal solar cell is characterized in that front electrodes which are periodically arrayed are arranged on the lower side surface of a front contact layer; a two-dimensional silicon-based micro-nano photonic crystal solar cell structure is arranged between the front electrodes and back electrodes, upper layers of the two-dimensional silicon-based micro-nano photonic crystal solar cell structure are type-n silicon semiconductor layers, a lower layer of the two-dimensional silicon-based micro-nano photonic crystal solar cell structure is a type-p silicon semiconductor layer, and PN junctions are formed by the type-n silicon semiconductor layers and the type-p silicon semiconductor layer; a back contact layer is arranged at the bottoms of the back electrodes, and the back contact layer and the front contact layer are made of identical materials; the back electrodes which are of aluminum thin layer structures are arranged in slow-light regions or band-gap regions of the type-p silicon semiconductor layer. The two-dimensional silicon-based micro-nano photonic crystal solar cell has the advantages that the two-dimensional silicon-based micro-nano photonic crystal solar cell is simple in structure, small in size, low in threshold, short in carrier diffusion distance and high in stability, light coupling efficiency and light transmission efficiency, is far thinner than the traditional silicon solar cell and becomes a new-generation low-cost and efficient solar cell device with the maximum potential, and mature processing and composite technologies are implemented.

Description

A two-dimensional silicon-based micro-nano photonic crystal solar cell

Technical field:

The invention belongs to the technical field of solar cells, and relates to a novel photonic crystal solar cell structure, in particular to a two-dimensional silicon-based micro-nano photon with photonic band gap and slow light effect, small thickness, good light trapping, and high photoelectric conversion efficiency Crystalline solar cells.

Background technique:

Solar cells are semiconductor devices that convert light energy into electrical energy. Batteries, organic thin-film solar cells and fuel-sensitized solar cells, silicon-based solar cells are widely used at present, because silicon raw materials are abundant, photoelectric conversion efficiency is high, photoelectric performance stability and reliability are high, and processing technology is mature. It does not contain toxic elements, does not cause pollution to the environment, and is determined by factors such as high market acceptance. The main factors affecting the efficiency of solar cells can be attributed to two aspects, optical loss and electrical loss, the most important factor of which is optical absorption. To improve the conversion efficiency of solar cells, it is necessary to increase the absorption of sunlight by cell materials as much as possible. The essence of a silicon-based solar cell is a large PN junction. For general silicon materials (300K, E _g = 1.12eV), the available solar spectrum is 300-1100nm. The optical energy loss of silicon solar cells is not only because the energy is less than Infrared photons of crystalline silicon energy systems cannot be utilized, especially because photon energy cannot be effectively used for photoelectric conversion. In traditional solar cells, these two effects will cause the energy loss of nearly 70% of the battery. It is generally believed that the maximum light conversion efficiency of solar cells is 31%. In terms of the effective absorption of photons by materials; another key direction of silicon solar cell research is to reduce costs. The initial thickness of the silicon solar cell substrate was relatively thick, but now the thickness of the silicon substrate can be reduced from 350 to 400 μm to 150 to 200 μm. Experiments by the British company BT have proved that when the monocrystalline silicon solar cell is reduced to 175 μm, there is no additional loss in the efficiency of the cell . The 75μm thick solar cell made by Fraunhofer Company in Germany can still achieve 23.1% efficiency. However, studies have pointed out that silicon solar cells with a light-trapping structure with a thickness greater than 50 μm have better conversion efficiency. It can be seen that if an appropriate structure is adopted, the thickness of the material can be reduced without reducing the photoelectric conversion efficiency of the silicon solar cell. However, when the thickness of traditional solar cells is reduced, the loss of transmitted light increases with the thickness reduction. Theoretical calculations show that when the material is as thin as 50 μm, the absorption efficiency of the structure for long-wave photons decreases due to the thinning of the cell thickness. Only by adopting a light-trapping structure can the photoelectric conversion efficiency of the battery be guaranteed. In addition to the anti-reflection of the light-incoming surface of the battery and the minimum coverage area of the front electrode, the existing light trapping method is mainly to increase the path of light in the absorbing layer after the light enters the battery body, so that the refractive index of the absorbing layer is greater than that of the upper and lower layers. The textured material allows the unabsorbed light to return to the battery absorbing layer for secondary absorption, which can be divided into three ways:

(1) Single-layer or multi-layer 1/4-wavelength anti-reflection coatings are based on the principle of thin-film destructive interference to reduce the reflectivity of specific wavelengths. Although this type of anti-reflection coating is low in production cost, its reflection band is narrow, and The reflectivity increases greatly with the increase of the incident angle of the light wave;

(2) Gradient refractive index anti-reflection coating is an anti-reflection coating with a gradually changing refractive index deposited on the surface of silicon. It can achieve very low reflectivity in a wide spectrum and a wide range of incident angles. The preparation cost is high, and it is difficult to find materials that meet the requirements of the refractive index;

(3) Suede anti-reflection film is a combination of anti-reflection film technology and surface texturing technology to prepare anti-reflection film with suede structure, so as to realize the function of 1/4 wavelength anti-reflection film, and at the same time change and reduce reflection The rate increases with the increase of the incident angle, but this kind of anti-reflection film needs a combination of physical, chemical and even microelectronic methods, and the preparation process is difficult to control, so most of the research is in the experimental stage.

Recently, studies have suggested that silicon nanowires (or silicon pores) may be one of the most potential, low-cost, and high-efficiency solar cell device materials. Silicon nanowires can increase light absorption, and have carriers that only need to diffuse a short distance. It can achieve the advantages of the junction area, but the existing research is mostly on the one-dimensional structure of the nano-solar cell structure, and the mechanism used is also to trap light through diffuse reflection. Some studies have proposed a two-dimensional structure of radial silicon nanowires, but the manufacturing process is complicated. It is also not combined with the forbidden band and slow light theory of photonic crystal structure. Therefore, a new type of photonic crystal solar cell structure is sought, which has photonic band gap and slow light effect, small thickness, good light trapping, and high photoelectric conversion efficiency.

Invention content:

The purpose of the present invention is to overcome the shortcomings of the prior art, to design a new two-dimensional silicon-based micro-nano photonic crystal solar cell with small thickness, good light trapping, high conversion efficiency, stable structure, and easy processing and large-scale production. The characteristics of the band gap and slow light characteristics of the crystal are combined with the advantages of the silicon nanostructure, and the circular bow or elliptical scattering element is used to design the structure of the solar cell through simulation calculations to limit the propagation path and mode of light, and through the front contact The layer reduces reflection of incident light, the two-dimensional silicon-based micro-nano photonic crystal solar cell structure effectively traps light and converts photoelectricity, the front electrode and the back electrode prepare for building a circuit, and the back contact layer increases reflection of incident light organically. , to achieve the purpose of improving battery efficiency.

In order to achieve the above object, the main structure of the present invention includes a front contact layer, a front electrode, a two-dimensional silicon-based micro-nano photonic crystal solar cell structure, a back electrode, and a back contact layer; the lower part of the front contact layer made of a transparent conductive oxide TCO material There are periodically arranged front electrodes on the side; a two-dimensional silicon-based micro-nano photonic crystal solar cell structure is arranged between the front electrode and the back electrode, and the upper layer of the two-dimensional silicon-based micro-nano photonic crystal solar cell structure is an n-type silicon semiconductor layer, the lower layer is a p-type silicon semiconductor layer, and the n-type silicon semiconductor layer and the p-type silicon semiconductor layer form a PN junction; the bottom of the back electrode is provided with a back contact layer, and the material of the back contact layer is the same as that of the front contact layer; the thin aluminum The back electrode of the layer structure is set in the slow light region or forbidden band region of the p-type silicon semiconductor layer. The back electrode may be a single thin layer, and the shape of the back electrode is the same as that of the front electrode, both of which are strip shapes; The contact layer is irradiated on the two-dimensional silicon-based micro-nano photonic crystal solar cell structure. Due to the band gap and slow light effect, the two-dimensional silicon-based micro-nano photonic crystal solar cell structure has a good light trapping effect, which can effectively perform photoelectric conversion and excite Carriers are released, and the slow light effect ensures the directionality and stability of the carrier flow; the front electrode and the back electrode prepare for the photovoltaic effect of the carrier to form a circuit, and the back contact layer increases the reflection of the incident light to improve the efficiency of the battery .

The n-type silicon semiconductor of the present invention is a nano-photonic crystal dielectric column or an air hole structure with a two-dimensional silicon base with a band gap and a slow light effect, including a forbidden band scattering element, a forbidden band scattering element gap, and a slow light area The gap between scattering elements and scattering elements in the slow light area; the gap between the scattering elements in the forbidden band area is formed between the adjacent scattering elements in the forbidden area; the gap between the scattering elements in the slow light area is formed between the adjacent scattering elements in the slow light area; the scattering element is a circle arcuate or elliptical; the spatial arrangement of n-type silicon semiconductors is a triangular lattice or tetragonal lattice structure; assuming the lattice constant of n-type silicon semiconductors is a, the parameters b and c represent the long axis and The radius of the short axis defines the parameters e=1-c/b, e=0-1, and the parameters a and e vary according to the requirements of the forbidden band and slow light; The gap between the scattering elements in the forbidden zone is so that the incident light or its components cannot propagate in the vertical direction, which has a good light trapping effect; the slow light scattering elements in the slow light area and the gaps between the scattering elements in the slow light area have many changes to achieve Microcavity parameters with high quality factor and higher group refractive index; the forbidden band region and the slow light region have the same structural height, and their thickness is greater than 50 μm, and the forbidden band region and slow light region are periodically arranged alternately; the p-type silicon semiconductor is thicker than With a single semiconductor structure of 50 μm, the p-type silicon semiconductor can form a plane with the back electrode.

The micro-nano photonic crystal dielectric column or air hole structure involved in the present invention is the following two kinds of periodic arrangements with two-dimensional silicon base band gap and slow light effect substructure respectively: one is composed of circular bow or elliptical scattering elements The two-dimensional silicon-based photonic crystal bandgap structure with more than seven rows ensures the bandgap effect, and the scattering element gap is between the scattering elements; the nanophotonic crystal dielectric column or air hole has a large specific surface area, which can increase the incident light The absorption ability; its scattering elements and lattice constants are adjustable, so that the photon band gap of the dielectric column (or air hole) includes a region of 300-1100nm; when light is incident, the existence of the band gap makes the structure not allow light to travel parallel to Dielectric column or air) propagating in the direction, which is beneficial to the absorption and utilization of photons by the material; the other is a slow coupling waveguide composed of the same scattering element and differently arranged microcavities, which is formed by the absence of scattering element and the deflection of scattering element Multiple high-quality factor microcavities; through parameter adjustment, the Q value of a single cavity can reach 10 ⁴ or more; multiple microcavities form a slow light coupling waveguide structure, and the group refractive index of the coupling waveguide reaches 10 ⁴ , and its slow light velocity Far below the speed of light (only 1/10000 or lower of the speed of light), the efficiency of internal photons absorbed by the material exceeds many times that of unprocessed materials; where the Q value is based on the energy in the microcavity emitted by the signal generator The attenuation formula of the microcavity isolated mode obtained from the real-time distribution is:

U(t)＝U ₀ exp(-αt) (1)

Where U ₀ is the initial energy in the cavity, and U(t) represents the energy corresponding to the microcavity at time t after attenuation factor α. For a mode centered on a resonant frequency f, the quality factor Q corresponding to the microcavity can be expressed as (2):

Q＝2πf/α (2)

The relationship between the group velocity v _g and the group refractive index n _g can be expressed by formula (3), c is the speed of light:

${\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; c</span>}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

It can be seen that since the structure is a periodic arrangement of the above two substructures, it has many advantages in increasing light trapping and light absorption: the dielectric column or air hole structure has a large specific surface area; the bandgap structure has a light trapping effect, and the incident light In the silicon line array, it is gradually absorbed after multiple reflections back and forth; the group velocity of light in the slow light structure is very small, which is convenient for photons to be absorbed by the material, thereby generating more carriers, and the slow light effect also ensures that the carriers The directionality and stability of the flow; the size of the structure is adjusted according to the absorption wavelength to complete high-efficiency optical absorption; the greater the height of the dielectric column or the depth of the hole, the lower the reflectivity of the cell. Light effect, when the depth of the structure reaches 50 μm, the reflectance of the battery at 400-1000 nm is lower than 10% on average.

The photonic crystal dielectric column or the air hole structure of the present invention forms a shallow PN junction with the p-type silicon semiconductor, and the photogenerated carriers reach the junction region after a very short diffusion distance, thereby having a higher carrier collection rate, The two structures are arranged in a periodic shape, and the forbidden band region can increase the photoelectric conversion efficiency by nearly 50% compared with the traditional battery, while the photoelectric conversion efficiency in the slow light region is twice that of the traditional battery. The joint effect greatly increases the photoelectric conversion efficiency of the structure. The theoretical value of the efficiency can reach more than 60%. Due to the electrical properties of this structure and the silicon base material, no further treatment such as doping is required, and it has good electrical transmission performance.

Compared with the prior art, the present invention applies the principle of photon band gap and slow light to solar photoelectric conversion; the band gap structure has a good light trapping effect, and the incident light is gradually absorbed in the silicon line array after multiple reflections back and forth, It has a good light trapping effect; the slow light structure has good light trapping, and because the group velocity of light is very small, it is convenient for the material to absorb photons and generate more carriers. The slow light effect ensures the directionality and stability of carrier flow The designed structure is not only regular, but also flexible: silicon nanopillars with relatively small scattering elements exhibit lower reflection and higher absorption in the high-frequency region; silicon nanopillars with relatively large scattering elements exhibit The low-frequency region shows lower reflection and higher absorption; silicon nanopores showing similar regularity can also be taken, which has a simple structure and a thickness much lower than that of traditional silicon solar cells, small volume, low threshold, and low load capacity. The carrier diffusion distance is short, the stability, light coupling and transmission efficiency are high, and the processing and recombination technology is mature. It has become the most potential, low-cost, and high-efficiency solar cell device of the new generation.

Description of drawings:

Fig. 1 is a schematic diagram of the principle of the main structure of the present invention.

Fig. 2 is a schematic diagram of the structural principle of the two-dimensional silicon-based micro-nano photonic crystal solar cell structure involved in the present invention, wherein (1) is a perspective view; (2) is a top view.

FIG. 3 is a forbidden band diagram of the forbidden band region in Embodiment 1 of the present invention, wherein the horizontal axis is the parameter e value, and the vertical axis is the relative forbidden band value.

Fig. 4 is the quality factor Q value curve of a single microcavity in Example 1 of the present invention, wherein the horizontal axis is the parameter e value, and the vertical axis is the Q value.

Fig. 5 is a group refractive index curve in Example 1 of the present invention, wherein the horizontal axis is the normalized frequency f, and the vertical axis is the group refractive index n _g value.

6 is a schematic diagram of the structural principle of the two-dimensional silicon-based micro-nano photonic crystal solar cell structure in Example 2 of the present invention, wherein (1) is a perspective view; (2) is a top view.

FIG. 7 is a forbidden band diagram of the forbidden band region in Example 2 of the present invention, wherein the horizontal axis is the parameter e value, and the vertical axis is the relative forbidden band value.

FIG. 8 is a curve of the quality factor Q value of a single microcavity in Example 2 of the present invention, wherein the horizontal axis is the parameter e value, and the vertical axis is the Q value.

Fig. 9 is a group refractive index curve in Example 2 of the present invention, wherein the horizontal axis is the normalized frequency f, and the vertical axis is the group refractive index n _g value.

Detailed ways:

Further description will be given below through the embodiments and in conjunction with the accompanying drawings.

The main structure of this embodiment includes a front contact layer 1, a front electrode 2, a two-dimensional silicon-based micro-nano photonic crystal solar cell structure 3, a back electrode 4 and a back contact layer 5; the front contact layer 1 is made of a transparent conductive oxide TCO material The lower side of the front electrode 2 is provided with a periodic arrangement; the two-dimensional silicon-based micro-nanophotonic crystal solar cell structure 3 is arranged between the front electrode 2 and the back electrode 4, and the two-dimensional silicon-based micro-nanophotonic crystal solar cell structure 3 The upper layer is an n-type silicon semiconductor layer 6, the lower layer is a p-type silicon semiconductor layer 7, and the n-type silicon semiconductor layer 6 and the p-type silicon semiconductor layer 7 form a PN junction; the bottom of the back electrode 4 is provided with a back contact layer 5, and the back contact The material of the layer 5 is the same as that of the front contact layer 1; the back electrode 4 of the aluminum thin layer structure is arranged in the slow light region or the forbidden band region of the p-type silicon semiconductor layer 7, the back electrode 4 may be a single thin layer, and the back electrode The shape of 4 is the same as that of the front electrode, both of which are in the shape of strips; the incident light is irradiated on the two-dimensional silicon-based micro-nano photonic crystal solar cell structure 3 through the front contact layer 1, due to the band gap and slow light effect, the two-dimensional silicon-based Micro-nano photonic crystal solar cell structure 3 has a good light-trapping effect, effectively performs photoelectric conversion, and excites carriers, and the slow light effect ensures the directionality and stability of carrier flow; the front electrode 2 and the back electrode 4 In preparation for the photovoltaic effect carrier to form a circuit, the back contact layer 5 increases the reflection of incident light and improves the efficiency of the cell.

The n-type silicon semiconductor 6 described in this embodiment is a nano-photonic crystal dielectric column or air hole structure with a two-dimensional silicon base with a band gap and a slow light effect, including a forbidden band scattering element 8 and a forbidden band scattering element gap 9 , the scattering elements 10 in the slow-light region and the gaps 11 between the scattering elements in the slow-light region; the gaps 9 in the forbidden-band region are formed between the scattering elements 8 in the adjacent forbidden-band region; the slow-light is formed between the scattering elements 10 in the adjacent slow-light region Area scattering element gap 11; scattering element is circular segment or ellipse; the spatial arrangement of n-type silicon semiconductor 6 is a triangular lattice or tetragonal lattice structure; set the lattice constant of n-type silicon semiconductor 6 as a, parameters b and c Represent the radius of the major axis and the minor axis of the circular segment or elliptical scattering element respectively, define the parameters e=1-c/b, e=0-1, the parameters a and e vary according to the requirements of the forbidden band and slow light; the forbidden band The area is composed of more than 7 rows of forbidden-band scattering elements 7 and forbidden-band scattering element gaps 8, so that the incident light or its components cannot propagate to the vertical direction, and has a good light-trapping effect; the slow-light scattering elements in the slow-light area 9 and the gap 10 of the scattering element in the slow light region have various changes to achieve high quality factor microcavity parameters and obtain a higher group refractive index; The p-type silicon semiconductor 7 is a single semiconductor structure with a thickness greater than 50 μm, and the p-type silicon semiconductor can form a plane with the back electrode 4 .

The two-dimensional silicon-based micro-nano photonic crystal solar cell structure 3 described in this embodiment adopts a commercially available two-dimensional silicon wafer, and its micro-processing technology is mature, and the front and rear electrodes and front and rear contact layer materials are also conventional commercially available products.

Example 1:

The overall structure of this embodiment is shown in Figure 1. The n-type silicon semiconductor 6 involved in the two-dimensional silicon-based micro-nano photonic crystal solar cell structure 3 is a structure with two substructures of forbidden band and slow light effect arranged periodically. The scattering element of the n-type silicon semiconductor 6 adopts a circular bow, and the space is arranged as a triangular lattice structure; the central wavelength of the forbidden band is set at λ=700nm, which can be obtained by the plane wave expansion method: when the central wavelength of the forbidden band is set at 700nm, The lattice constant of the structure is a=0.4λ=280nm, and when the parameters b=0.4a and e=0.4, both the forbidden band and slow light have better effects; since the forbidden band of the structure is close to 50% of the central wavelength, as shown in the figure As shown in 3, the forbidden band of this structure is between 350 and 1050nm. This range includes not only the range of visible light, but also the area with high sunlight intensity; in order to ensure the light trapping effect of the forbidden band, the forbidden band is composed of more than 7 The forbidden band scattering element 8 and the forbidden band scattering element gap 9 are formed, so that the incident light or its component cannot propagate to the direction perpendicular to the nanocolumn (or hole); (2) the slow light area includes the slow light area scattering element 10 1. Scattering element gap 11 in the slow light area, which is composed of three rows of scattering elements. One of the two adjacent scattering elements in the middle row is removed at intervals, and the other is deflected by 90° to form a microcavity. The other four around the microcavity Scattering elements are also deflected sequentially to form a ring shape, so as to achieve high quality factor microcavity parameters and obtain high group refractive index. These two structures have the same height (thickness is greater than 50 μm), and they are periodically arranged alternately. The lower layer is a p-type silicon semiconductor 7, which is a single semiconductor structure (thickness is greater than 50 μm), and the back electrode is strip-shaped. Electrode correspondence, see Figure 2.

The working principle of this embodiment is: the incident light passes through the front contact layer 1, and irradiates on the two-dimensional silicon-based micro-nano photonic crystal solar cell structure 3 almost without reflection. Due to the band gap and slow light effect, this structure has a good The light trapping effect can effectively perform photoelectric conversion and excite carriers, and the slow light effect also ensures the directionality and stability of carrier flow; the front electrode 2 and the back electrode 4 are the current carriers of the photovoltaic effect The sub-constituent circuit is prepared, and the back contact layer 5 increases the reflection of the incident light to further improve the efficiency of the cell; the front contact layer 1 and the back contact layer 5 have the function of protecting the photonic crystal solar cell, and Fig. 3 is a forbidden band diagram of the forbidden band region , it can be seen from Figure 3 that the relative forbidden band has a maximum value near e=0.4, which is 49.6%; Figure 4 is a figure of quality factor in the slow light area, and there is also a maximum value near e=0.4, which is 4.8×10 ⁴ ; Figure 5 is the group refractive index diagram of the slow light area. In the case of no displacement in the slow light area, the maximum value of the group refractive index reaches 1.6×10 ⁴ ; if the overall slow light area has a reasonable displacement, the value of the group refractive index is still will increase.

Example 2:

The overall structure of this embodiment is the same as that of FIG. 1 . The upper layer n-type silicon semiconductor 6 in the two-dimensional silicon-based micro-nano photonic crystal solar cell structure 3 involved in the embodiment is a structure with two substructures of forbidden band and slow light effect arranged periodically. In order to meet the large forbidden band of the structure, the scattering element adopts a circular bow shape; the spatial arrangement of the structure is a triangular lattice structure; the central wavelength of the forbidden band is set at λ=700nm, which can be obtained by the plane wave expansion method: When the central wavelength of the structure is set at 700nm, the lattice constant of the structure is a=0.375λ=262.5nm, and when the parameters b=0.42a, e=0.3, the forbidden band and slow light also have good effects; because the forbidden band of the structure is close to 43% of the central wavelength, as shown in Figure 7, the forbidden band of the structure is slightly narrow, between 399 and 1;001nm, this range also includes the range of visible light, and includes the region with high sunlight intensity; In order to ensure the light trapping effect of the forbidden band, the forbidden band has more than 7 rows of scattering elements 8 and the scattering element gap 9 in the forbidden band, so that the incident light or its components cannot propagate to the direction perpendicular to the nanocolumn (or hole) ;; The slow-light area includes the scattering elements 10 in the slow-light area and the scattering element gap 11 in the slow-light area. The microcavity parameters with high quality factor and higher group refractive index, three rows of scattering elements forming the slow light area, that is, the rectangular area in Figure 6(2), the overall rightward displacement ds=0.18a; the height of these two structures The same (thickness greater than 50 μm is enough), periodically arranged alternately, the lower layer is a p-type silicon semiconductor 7 is a single semiconductor structure (thickness greater than 50 μm is enough), the back electrode is strip-shaped, corresponding to the front electrode.

The working principle of this embodiment is: the incident light passes through the front contact layer 1, and irradiates on the two-dimensional silicon-based micro-nano photonic crystal solar cell structure 3 almost without reflection. Due to the band gap and slow light effect, this structure has a good The light trapping effect can effectively perform photoelectric conversion and excite carriers, and the slow light effect ensures the directionality and stability of carrier flow; the front electrode 2 and the back electrode 4 are the carriers formed by the photovoltaic effect The circuit is prepared, and the back contact layer 5 increases the reflection of the incident light to further improve the cell efficiency; the front contact layer 1 and the back contact layer 5 have the function of protecting the photonic crystal solar cell; Fig. 7 is a forbidden band diagram of the forbidden band region, which can It can be seen that near e=0.375, the relative forbidden band has a maximum value of 43%; Figure 8 is a figure of quality factor in the slow light area, and it also has a maximum value near e=0.375, which is 4.0×10 ⁴ ; Figure 9 It is the group refraction index diagram of the slow light region. In the case of a displacement of ds=0.18a in the slow light region, the maximum value of the group refraction index reaches 2.0×10 ⁴ .

Claims (2)

1. A two-dimensional silicon-based micro-nano photonic crystal solar cell, characterized in that the main structure includes a front contact layer, a front electrode, a two-dimensional silicon-based micro-nano photonic crystal solar cell structure, a back electrode and a back contact layer; transparent conductive oxidation The lower side of the front contact layer made of TCO material is provided with periodically arranged front electrodes; a two-dimensional silicon-based micro-nano photonic crystal solar cell structure is arranged between the front electrode and the back electrode, and the two-dimensional silicon-based micro-nano photonic crystal The upper layer of the solar cell structure is an n-type silicon semiconductor layer, the lower layer is a p-type silicon semiconductor layer, and the n-type silicon semiconductor layer and the p-type silicon semiconductor layer form a PN junction; the bottom of the back electrode is provided with a back contact layer, and the material of the back contact layer The same material as the front contact layer; the back electrode of the aluminum thin layer structure is set in the slow light region or forbidden band region of the p-type silicon semiconductor layer, the back electrode may be a single thin layer, and the shape of the back electrode is the same as that of the front electrode , all in the shape of strips; the incident light is irradiated on the two-dimensional silicon-based micro-nanophotonic crystal solar cell structure through the front contact layer. Due to the band gap and slow light effect, the two-dimensional silicon-based micro-nanophotonic crystal solar cell structure has a good The light trapping effect effectively performs photoelectric conversion and excites carriers, and the slow light effect ensures the directionality and stability of the carrier flow; the front electrode and the back electrode prepare for the photovoltaic effect carrier to form a circuit, and the back contact The layer increases the reflection of the incident light and improves the efficiency of the cell. 2. according to the described two-dimensional silicon-based micro-nano photonic crystal solar cell of claim 1, it is characterized in that said n-type silicon semiconductor is a nano-photonic crystal dielectric column or air with a two-dimensional silicon base band gap and slow light effect. Hole structure, including forbidden band scattering elements, forbidden band scattering element gaps, slow light area scattering elements and slow light area scattering element gaps; forbidden band scattering element gaps are formed between adjacent forbidden band scattering elements; adjacent The scattering elements in the slow light area form gaps between the scattering elements in the slow light area; the scattering elements are circular bow or ellipse; the spatial arrangement of the n-type silicon semiconductor is a triangular lattice or a tetragonal lattice structure; the lattice of the n-type silicon semiconductor The constant is a, the parameters b and c respectively represent the radius of the major axis and the minor axis of the circular segment or elliptical scattering element, define the parameter e=1-c/b, e=0-1, and the parameters a and e are based on the forbidden band and slow The requirements of the light change; the forbidden zone is composed of more than 7 rows of forbidden zone scattering elements and the gap between the forbidden zone scattering elements, so that the incident light or its components cannot propagate in the vertical direction, and has a good light trapping effect; slow light There are many changes in the gap between the slow light scattering element and the slow light area scattering element in order to achieve high quality factor microcavity parameters and obtain a higher group refractive index; the structure height of the forbidden band area and the slow light area is the same, and its thickness is greater than 50 μm , the forbidden band region and the slow light region are periodically arranged alternately; the p-type silicon semiconductor is a single semiconductor structure with a thickness greater than 50 μm, and the p-type silicon semiconductor can form a plane with the back electrode.