阅读说明：本技术 一种与火星光谱匹配的三结砷化镓太阳电池 (Triple-junction gallium arsenide solar cell matched with Mars spectrum ) 是由 陈燕 石海平 杨洪东 王文强 刘治钢 张晓峰 汪静 穆浩 于 2021-06-25 设计创作，主要内容包括：本发明公开了一种与火星光谱匹配的三结砷化镓太阳电池,该太阳电池包括依次串联的GaInP顶电池、GaInAs中电池以及Ge底电池；所述GaInP顶电池的工作波长为300nm～670nm；所述GaInAs中电池的工作波长为500nm～900nm；所述Ge底电池的工作波长为900nm～1800nm；所述GaInP顶电池的带隙为1.85eV；所述GaInAs中电池的带隙为1.37eV；Ge底电池为0.67eV。上述太阳电池针对火星表面光谱,通过降低顶电池带隙、增加布拉格反射器和多层减反射膜三项技术优化,使电池结构与火星光谱相匹配其达到平衡,进而实现顶、中电池对300-950nm波段光能的均等利用,提升太阳电池在火星光谱下的能量输出效率。(The invention discloses a triple-junction gallium arsenide solar cell matched with a Mars spectrum, which comprises a GaInP top cell, a GaInAs middle cell and a Ge bottom cell which are sequentially connected in series; the working wavelength of the GaInP top battery is 300 nm-670 nm; the working wavelength of the battery in the GaInAs is 500 nm-900 nm; the working wavelength of the Ge-bottom battery is 900 nm-1800 nm; the band gap of the GaInP top cell is 1.85 eV; the band gap of the GaInAs medium cell is 1.37 eV; the Ge bottom cell was 0.67 eV. Aiming at the Mars surface spectrum, the solar cell is optimized by three technologies of reducing the band gap of the top cell, increasing the Bragg reflector and the multilayer antireflection film, so that the cell structure is matched with the Mars spectrum to achieve balance, further the top cell and the middle cell can equally utilize the light energy of the 300-doped 950nm waveband, and the energy output efficiency of the solar cell under the Mars spectrum is improved.)

1. A three-junction gallium arsenide solar cell matched with a Mars spectrum is characterized by comprising a GaInP top cell (1), a GaInAs middle cell (2) and a Ge bottom cell (3) which are sequentially connected in series;

the working wavelength of the GaInP top battery (1) is 300-670 nm;

the working wavelength of the battery (2) in the GaInAs is 500 nm-900 nm;

the working wavelength of the Ge-bottom battery (3) is 900 nm-1800 nm;

the band gap of the top cell (1) is 1.85 eV;

the band gap of the middle battery (2) is 1.37 eV;

the band gap of the bottom cell (3) is 0.67 eV.

2. Triple junction gallium arsenide solar cell according to claim 1 characterised in that the material of the GaInP top cell (1) is Ga_0.45In_0.55P；

The GaInAs medium battery (2) is made of Ga_0.92In_0.08As。

3. The triple junction gallium arsenide solar cell according to claim 2, wherein a bragg reflector (7) is arranged between the GaInAs intermediate cell (2) and the Ge-bottom cell (3), said bragg reflector (7) being adapted to reflect the transmitted solar spectrum back to the GaInAs intermediate cell (2) for secondary absorption.

4. The triple junction gallium arsenide solar cell according to any of claims 1 to 3, further comprising a multilayer anti-reflective film (8) on the surface of the cell;

the multilayer antireflection film (8) is made of TiOx/Al₂O₃Based on the double-layer antireflection film system, an admittance matrix method of a multilayer dielectric film is adopted, and the final triple-junction gallium arsenide solar cell is optimally designed according to the maximum short-circuit current density.

5. The triple junction gallium arsenide solar cell of claim 4 wherein said TiOx/Al is₂O₃The film thickness of the double-layer antireflection film is 580nm/720 nm.

Technical Field

The invention relates to the technical field of batteries, in particular to a three-junction gallium arsenide solar battery matched with a Mars spectrum.

Background

The solar cell array converts solar energy into electric energy by utilizing a photoelectric conversion principle, supplies power to a satellite in an illumination period, and charges a storage battery pack. At present, a solar cell array mainly adopts a three-junction gallium arsenide solar cell, but the existing cell design is based on the AM0 (solar outside the atmospheric zone) spectrum condition of the earth outer space, so that the cell has the best performance in the whole life cycle. However, the solar spectrum on the surface of the mars is subjected to higher scattering action of particles such as dust and the like in the process of passing through the mars atmosphere, and compared with the AM0 spectrum of the orbit of the earth, as shown in fig. 1, the blue light section is weakened, the red light and the infrared light section are enhanced, so that the top battery current is lower, the middle battery current is higher, and the spectrum on the mars is not matched with the conventional three-junction gallium arsenide solar battery structure matched with the spatial AM0 spectrum, so that redesign and optimization are needed.

The MER tour instrument in the United states adopts an ITJ triple junction gallium arsenide solar cell of Spectrolab company, and the photoelectric efficiency of the ITJ solar cell under the condition of 30 degrees of the surface of a spark is reduced by 11.94 percent compared with the AM0 condition of the earth orbit. And the photoelectric efficiency of a Spectrolab UTJ solar cell adopted by the 'Phoenix number' lander under the condition of 60 degrees on the surface of a Mars is reduced by 16.25 percent compared with the AM0 condition of the earth orbit.

Disclosure of Invention

In view of the above, the invention provides a triple-junction gallium arsenide solar cell matched with a mars spectrum, aiming at the mars surface spectrum, the cell structure is matched with the mars spectrum by optimizing three technologies of reducing a top cell band gap, increasing a bragg reflector and a multilayer antireflection film, so that the equal utilization of light energy of 300-doped 950nm wave bands by a top cell and a middle cell is realized, and the energy output efficiency of the solar cell under the mars spectrum is improved.

The invention adopts the following specific technical scheme:

a three-junction gallium arsenide solar cell matched with a Mars spectrum comprises a GaInP top cell, a GaInAs middle cell and a Ge bottom cell which are sequentially connected in series;

the working wavelength of the GaInP top battery is 300 nm-670 nm;

the working wavelength of the battery in the GaInAs is 500 nm-900 nm;

the working wavelength of the Ge-bottom battery is 900 nm-1800 nm;

the band gap of the top cell is 1.85 eV;

the band gap of the middle cell is 1.37 eV;

the band gap of the bottom cell is 0.67 eV;

further, the GaInP top cell is made of Ga_0.45In_0.55P, the material of the GaInAs battery is Ga_0.92In_0.08As。

Furthermore, a Bragg reflector is arranged between the GaInAs middle cell and the Ge bottom cell and used for reflecting the transmitted solar spectrum back to the GaInAs middle cell for secondary absorption.

Still further, a multi-layer antireflection film on the surface of the battery is also included;

the multilayer antireflection film is made of TiOx/Al₂O₃Based on the double-layer antireflection film system, an admittance matrix method of a multilayer dielectric film is adopted, the coated glass cover plate is comprehensively considered, and the optimization design is carried out by taking the maximum short-circuit current density of the final triple-junction gallium arsenide solar cell as an optimization target. TiOx/Al finally determined by the design₂O₃The thickness of the film layer is 580nm/720nm, but depending on the specific device, variations around this value are within the scope of the present invention.

Has the advantages that:

1. in the three-junction gallium arsenide solar cell, the material band gap is changed by adjusting the doping ratio of Ga and In the GaInP top cell, so that the absorption spectrum range of the material is changed. The band gap of the GaInP top battery is reduced from 1.90eV to 1.85eV, the spectral absorption limit of the top battery is expanded from 653nm to 670nm, and the spectral absorption waveband of the GaInP top battery is increased, so that the current output of the top battery is improved, the current between the top battery and the middle battery is more matched, and the overall current output of the battery is improved;

2. according to the triple-junction gallium arsenide solar cell, the multiple pairs of AlGaAs/GaAs Bragg reflection structures are additionally arranged between the GaInAs middle cell and the Ge bottom cell, the transmitted 800 nm-900 nm spectral band absorbed by the corresponding middle cell is reflected back to the middle cell again for secondary absorption, the light energy utilization rate and the middle cell current are improved, partial light energy loss given out for the top cell is compensated, and the anti-irradiation capacity of the cell is improved;

3. the triple junction gallium arsenide solar cell also comprises TiOx/Al positioned on the surface of the cell₂O₃A multilayer antireflection film. Aiming at the spectrum of the surface of the Mars, an admittance matrix method of a multilayer dielectric film is adopted, and two layers of TiOx/Al are designed according to the maximum optimization target of the short-circuit current density₂O₃The thickness of the antireflection film is 580nm/720nm, the average reflectivity of a 300nm-1000nm spectrum band is reduced from the existing 8% to not more than 5%, and the utilization rate of the cell to sunlight is improved.

4. The three-junction gallium arsenide solar cell can solve the problem of insufficient output power on the surface of a Mars, the structure of the three-junction gallium arsenide solar cell and a surface antireflection film are optimally designed aiming at the surface spectrum of the Mars, the current matching of a top cell and a middle cell can be realized, the current ratio of the top cell and the middle cell after improvement in the AM0 spectrum environment is improved to 1.05 from the original 0.98, the current ratio of the top cell and the middle cell after improvement in the Mars30 (30 DEG on the surface of the Mars) solar spectrum environment is improved to 0.986 from the original 0.91, and the cell current is improved by more than 15% compared with that of a conventional cell.

Drawings

FIG. 1 shows AM0 and a Mars spectrum curve;

FIG. 2 is a schematic diagram of a triple junction GaAs solar cell of the present invention;

FIG. 3 is a comparison of the technical route of a triple junction GaAs solar cell;

fig. 4 is a graph comparing the quantum efficiency of solar cells before and after improvement.

Wherein, 1-top cell, 2-middle cell, 3-bottom cell, 4-front electrode, 5-back electrode, 6-substrate, 7-Bragg reflector, 8-multilayer antireflection film

Detailed Description

The invention is described in detail below by way of example with reference to the accompanying drawings.

Referring to fig. 2 and 3, the invention provides a triple junction gallium arsenide solar cell matched with a spark spectrum, which comprises a GaInP top cell 1, a GaInAs middle cell 2 and a Ge bottom cell 3 which are sequentially connected in series; as shown in the structure of fig. 2, a front electrode 4 is arranged on the top of a GaInP top cell 1, and a substrate 6 and a back electrode 5 are arranged on the bottom of a Ge bottom cell 3; wherein:

the GaInP top battery 1 absorbs sunlight in a wave band of 300 nm-670 nm; the battery 2 in the GaInAs absorbs the sunlight with the wave band of 500 nm-900 nm; the Ge bottom cell 3 absorbs sunlight in a wave band of 900 nm-1800 nm;

the bandgap of the GaInP top cell 1 is 1.85 eV; the band gap of the cell 2 in GaInAs is 1.37 eV; the Ge cell band gap is 0.67 eV.

The three-junction gallium arsenide solar cell is formed by connecting three sub-cells, namely a GaInP top cell 1, a GaInAs middle cell 2 and a Ge bottom cell 3 in series, and the current density of the Ge bottom cell 3 is greater than that of the GaInP top cell 1 and the GaInAs middle cell 2; in terms of performance, the solar cell is characterized in that each sub-cell selectively absorbs and responds to different solar spectrum bands, and the current output of the whole cell is limited by the minimum photo-generated current of the sub-cell in the whole cell due to the fact that the sub-cells are connected in series to have an inter-junction current limiting effect.

The short-circuit current density calculation formula of the triple-junction gallium arsenide solar cell is as follows:

aiming at the characteristic that the spectrum of the Mars surface solar spectrum is weak within the range of 200-700 nm, in order to improve the current output of the top cell 1, the spectrum absorption waveband of the GaInP top cell 1 needs to be increased. And the calculation formula of the absorption wavelength lambda of the material is as follows:

λ＝1.24/Eg；

wherein Eg is the material bandgap.

Aiming at a Mars surface spectrum, the three-junction gallium arsenide solar cell sets the working wavelength and the material band gap of a GaInP top cell 1 and a cell 2 in GaInAs, sets the working wavelength of the top cell 1 to be 300-670 nm and the band gap to be 1.85eV, reduces the band gap of the top cell 1 from conventional 1.90eV to 1.85eV, expands the spectral absorption limit of the top cell 1 from 653nm to 670nm, realizes the equal utilization of the 300-950nm band light energy of the top cell 1 and the middle cell 2, improves the current output of the top cell 1 due to the increase of the spectral absorption band of the GaInP top cell 1, enables the current density of two junctions to be relatively close, further reduces the current mismatch degree between the top cell 1 and the middle cell 2, and enables the cell to obtain the maximum power output under the Mars spectrum; the current ratio of the top battery 1 to the middle battery 2 is improved from 0.98(AM0) and 0.91(Mars30) to 1.05(AM0) and 0.986(Mars30), and the output current of the battery is improved by more than 15% compared with that of the conventional battery.

In a specific embodiment, the material of the GaInP top cell 1 is Ga_(1-y)In_yThe material of the cell 2 in P, GaInAs is Ga_(1-x)In_xAs, wherein:

x is more than 0.01 and less than 0.50, and can be any value between 0.01 and 0.50;

y is more than 0.50 and less than 0.99, and can be any value between 0.50 and 0.99;

and when y is 0.55, the material of the GaInP top cell 1 is Ga_0.45In_0.55P。

The triple-junction gallium arsenide solar cell changes the band gap of the material by adjusting the doping proportion of Ga and In the top cell 1 and the middle cell 2, so that the absorption spectrum range of the material is changed; and the material of the top cell 1 is Ga_0.51In_0.49Adjusting P to Ga_0.45In_0.55P, and the doping of an epitaxial material Al element is reduced, the band gap of the top cell 1 is reduced from 1.90eV to 1.85eV, the spectral absorption limit of the top cell 1 is expanded from 653nm to about 670nm, and the current of the top cell 1 is improved.

Specifically, the triple junction gallium arsenide solar cell further comprises a multilayer antireflection film 8 positioned on the top of the GaInP top cell 1; multilayer antireflection film 8 made of TiO_x/Al₂O₃Based on the double-layer antireflection film system, an admittance matrix method of a multilayer dielectric film is adopted, the coated glass cover plate is comprehensively considered, and the optimization design is carried out by taking the maximum short-circuit current density of the final triple-junction gallium arsenide solar cell as an optimization target. The refractive index of each layer material of the m-layer antireflection film system is known to be n_kA thickness d_kThe refractive indexes of the incident medium and the cell substrate material are n₀，n_m+1Where k is 1, 2, 3 … … m, the interference matrix of m layers is:

wherein M is_kInterference matrix for the k-th layer:

in the formula (I), the compound is shown in the specification,is the optical path of the k-th layer;

n_kis the refractive index of the kth layer;

i is an imaginary unit;

d_kis the thickness of the kth layer;

λ is the incident wavelength;

then:

the equivalent optical admittance Y ═ C/B, the film-based reflectance over the entire wavelength range:

from the light transmittance of Mars, the transmittance is significantly reduced in the range of 200nm to 700nm, particularly 350nm to 500nm, and the current output of the GaInP top cell 1 is limited.

Aiming at Mars spectrum, the antireflection film is designed and optimized on the basis of quantum efficiency, incident light spectrum, refractive index of subcell material, thickness and the like in the top cell 2 and the middle cell 2, an admittance matrix method of a multilayer dielectric film is adopted, TFC (optical thin film design) software is utilized to perform simulation analysis on the multilayer antireflection film 8, and TiO (titanium dioxide) is optimized₂/Al₂O₃The thickness of the film layer is adjusted to 580nm/720nm from the conventional 500nm/700nm, the average reflectivity of a 300nm-1000nm spectral band is reduced to below 5% from the existing 8%, particularly the reflectivity of a 1 wave band of the top cell is reduced, the utilization rate of a Mars spectrum is improved, and therefore the current matching of the top-middle cell 2 is achieved.

The three-junction gallium arsenide solar cell can be applied to a Mars detector, the problem of insufficient output power on the surface of a Mars can be solved, the current ratio JscTC/JscMC of the top cell 1 and the middle cell 2 after improvement in the AM0 environment is improved to 1.05 from the original 0.98, the current ratio JscTC/JscMC of the top cell 1 and the middle cell 2 after improvement in the Mars30 (Mars surface 30 ℃) solar spectrum environment is improved to 0.986 from the original 0.91, and the cell short-circuit current is improved by more than 15% compared with that of a conventional AM0 solar cell. The current density test results of the existing triple-junction gallium arsenide solar cell and the triple-junction gallium arsenide solar cell of the invention under various spectral conditions are shown in table 1 below.

TABLE 1

Furthermore, the Mars solar cell changes the resistance of the cell to space particle irradiation due to the structural change. Because the anti-radiation performance of the GaInAs material is poorer than that of the GaInP material, the current of the GaInAs in the existing AM0 spectrum battery is lower than that of a GaInP top battery during the design, so that the maximum output of the battery at the end of the service life is ensured. And the transmittance of the Mars spectrum in the range of 200 nm-700 nm is obviously reduced, so that the band gap of the GaInP top battery is reduced during battery design, the current output is improved, and the current of the battery is not matched at the end of the service life.

Aiming at the problem of mismatching of currents at the end of irradiation of a spark battery, a Bragg reflector 7 is arranged between a battery 2 and a Ge-based battery 3 in GaInAs, the Bragg reflector is of an AlGaAs/GaAs structure, the number of design pairs is 8-16, and the Bragg reflector 7 is used for reflecting a transmitted spectrum section back to the battery 2 in the GaInAs again for secondary absorption.

By additionally arranging the Bragg reflector 7 between the GaInAs middle battery 2 and the Ge bottom battery 3, the transmitted 800 nm-900 nm spectrum section absorbed by the corresponding middle battery 2 can be reflected back to the middle battery 2 for secondary absorption, the light energy utilization rate and the current of the middle battery 2 are improved, partial light energy loss given out for the top battery 1 is compensated, and the anti-irradiation capability of the battery is improved. Fig. 4 shows a comparison of quantum efficiency test results before and after cell structure improvement.

In summary, the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.