TWI590479B - Golden single-crystal silicon solar cells with high reflectivity and panels containing the same - Google Patents

Description

High reflectivity gold single crystal germanium solar cell and panel containing the same

The present invention relates to a high reflectivity gold single crystal germanium solar cell that can simultaneously have an industrially acceptable conversion efficiency and produce a visually satisfactory bright metallic luster and a panel comprising the same.

矽Solar cell is one of the solar cells widely used today, and its design uses a germanium wafer doped with n-type or p-type charge carriers, and the germanium wafers doped with n-type or p-type charge carriers are in contact with each other. A p/n junction is formed as a photoelectric conversion substrate, and photons are incident on the surface of the photoelectric conversion substrate to generate a photoelectric effect to form a current. The solar cell with high conversion efficiency is the development goal of practitioners in the field, and the conversion efficiency of the solar cell is affected by the effective incident photon amount. In order to reduce the amount of incident photon reflection, and thereby improve the solar cell conversion efficiency, the prior art is to roughen the surface of the photoelectric conversion substrate (such as a single crystal germanium photoelectric conversion substrate, also known as the original film) by an etching process and to provide anti-reflection thereon. Floor.矽 Solar cells are limited by the type and thickness of the anti-reflective layer material that can effectively reduce the amount of photon reflection, so that the solar cell achieves high conversion efficiency. The appearance of the solar cell is usually monotonous dark blue, as taught by Jenny Nelson in 2003. The Physics of Solar Cells has revealed that anti-reflective coatings for germanium-based solar cells are generally optimized for red light with strong solar radiation, while reflections are more common in the blue light region. For this reason, germanium based solar cells typically exhibit a purple or blue color. Currently marketed single crystal germanium high efficiency solar cells (conversion efficiency) >20%), the surface is monotonous dark blue, as shown in Figure 1. However, in the case of national governments promoting the installation of solar cells or panels on the roof or exterior walls of buildings, in order to achieve both aesthetic and battery conversion efficiency, solar cells or panels of different colors must be developed as a combination of architectural design or environmental color. However, in order to maintain high conversion efficiency, the color solar cells developed today are still dominated by low-reflection color solar cells, which can exhibit different colors from the purple or blue colors of the prior art, but the colors they display are still dark. series. Therefore, the development of solar cells with bright colors such as gold with a bright metallic luster is needed.

The higher the surface reflectance of an object, the higher the amount of light entering the viewer's eye, and the observer can perceive that the color becomes brighter. However, for solar cells, the surface reflectance is increased, that is, the amount of light entering the battery element is relatively reduced, and the battery conversion efficiency is thus lowered. Therefore, how to choose between the conversion efficiency of solar cells and the brightness of their appearance is an important issue.

The degree of reflection of the object on the light is affected by the surface topography of the object (such as the flatness of the surface). In the solar cell process, the surface morphology of the original sheet is usually changed by etching or chemical mechanical polishing. The etching process is divided into alkali etching and acid etching according to the type of etching liquid used. Currently, only the alkali etching (the main component of the etching liquid is potassium hydroxide) is used for the single crystal germanium industry, and a special texture is generated on the surface of the original sheet. (texture), roughening the surface of the original sheet, thereby reducing the surface light reflectivity of the subsequently formed solar cell. Although this process can increase the conversion efficiency of the solar cell, it makes the appearance color darker.

PCT Patent Application No. TW 201445748 discloses a color solar cell which is provided with two or more transparent inorganic dielectric layers disposed on an antireflection layer, wherein the two or more transparent inorganic dielectric layers comprise at least one layer of titanium The first transparent inorganic dielectric layer formed by the oxide causes the solar cell to generate different reflection spectra to exhibit diverse colors. However, the purpose of this solar cell is not to focus on improving the high reflectivity and color brightness of solar cells.

Although the novel patent TW M493153 has disclosed a gold-crystallized tantalum solar cell, the photoelectric conversion substrate used therein is polycrystalline germanium, which is not a single crystal germanium, and the obtained solar cell has obvious mottled color patches and does not appear single and uniform. Monochrome color distribution.

In view of the above prior art problems, it is an object of the present invention to provide a bright, high reflectance gold single crystal germanium solar cell which can simultaneously have an industrially acceptable conversion efficiency and is visually satisfactory, and has a wavelength ranging from 560 nm to 630 nm. With a reflectivity greater than 20%. The invention also provides a panel comprising the battery to enrich the color selection of the solar cell, so that the solar cell can be widely used by the public.

For the purpose of the foregoing, the present invention provides a gold single crystal germanium solar cell comprising: a high reflectivity single crystal germanium photoelectric conversion substrate; at least one antireflection layer disposed on the high reflectivity single crystal germanium photoelectric conversion substrate On the material; one or more transparent inorganic dielectric layers formed over the anti-reflective layer; and a titanium oxide layer formed over the anti-reflective layer, wherein the one or more transparent inorganic dielectric layers have a dielectric layer The refractive index between about 1.3 and about 2.2, and the gold single crystal germanium solar cell have a reflectance of greater than 20% in the wavelength range of 560 nm to 630 nm.

For the purpose of the foregoing, the present invention treats the surface of a single crystal crucible sheet by acid etching (the main component of the etching solution is hydrofluoric acid), thereby removing the defects formed on the single crystal crucible sheet due to the previous production process. A flat, high reflectivity surface compared to a non-acid etch process to produce a solar cell that combines acceptable conversion efficiencies with the brighter appearance of prior art monocrystalline solar cells.

The invention also provides a solar cell panel comprising a battery module composed of a gold single crystal germanium solar cell according to the invention; a protective layer on the battery module; and a transparent glass plate on the protective layer .

11‧‧‧Transparent inorganic dielectric layer

12‧‧‧Titanium oxide layer

a‧‧‧The thickness of the anti-reflection layer

AR‧‧‧Anti-reflective layer

b‧‧‧Thickness of transparent inorganic dielectric layer

c‧‧‧Thickness of titanium oxide layer

S‧‧‧High reflectivity single crystal germanium photoelectric conversion substrate

Figure 1 is a commercially available high-efficiency solar cell (conversion efficiency >20%), the surface of the battery is single Darken the blue system.

2 is a photograph of a high reflectivity gold single crystal germanium solar cell obtained according to the present invention. The photographing ambient light source is an indoor fluorescent lamp having an intensity of about 800 Lux and a shooting angle of about 90 degrees. The solar cell is in a substantially horizontal manner. Lay flat.

3 is a cross-sectional view of a high reflectivity gold single crystal germanium solar cell in accordance with the present invention.

4 is a reflectance spectrum of the original sheets (a) to (d) obtained in Examples 1 (a), 1 (b), 1 (c), and 1 (d) in the wavelength range of 400 nm to 800 nm.

5 is a reflectance spectrum of the solar cells of Examples 2(a), 2(b), 2(c), and 2(d) in the wavelength range of 400 nm to 800 nm.

6 is a reflectance spectrum of a gold single crystal germanium solar cell of Example 3-1 in a wavelength range of 400 nm to 800 nm.

7 is a reflectance spectrum of a gold single crystal germanium solar cell of Example 3-2 in a wavelength range of 400 nm to 800 nm.

8(a) and 8(b) are the appearance of the polycrystalline germanium color solar cell of Comparative Example 1 and the appearance of the golden polycrystalline germanium solar cell of Comparative Example 2.

The term "about" as used herein is meant to include an acceptable error as the value determined by those skilled in the art, which is determined in part by how the value is measured or determined.

The term "inorganic dielectric" as used herein refers to an inorganic insulator that can be electrodeized.

The term "original sheet" as used herein refers to a tantalum solar cell on which the inorganic dielectric is not deposited on its surface.

The term "reflectance" as used herein is calculated from the amount of reflected light of a solar cell based on the amount of 100% reflected light obtained by integrating a rough white surface with an integrating sphere.

The reflectance maps herein are measured using a standard 8 degree velvet area fractional reflectance meter, which is an instrument that measures the reflectivity of a test piece with a rough surface. Designed by Lihua Technology Co., Ltd. This instrument is a new reflectivity measuring instrument designed according to ISO7724 and DIN5033 standards. It is often used in the field of solar cells to measure the reflectivity of solar tantalum wafers as an effective measure of the production process of solar tantalum wafers. Measuring instrument.

The basic configuration of the reflectance meter is well known to those of ordinary skill in the art of optoelectronic technology. The reflectance measuring instrument adopted by the invention adopts a xenon lamp source (having a wavelength of 250 nm to 2500 nm, a rated power of 75 W, an operating current of 5 A) and an 8°/d integrating sphere, and the integrating sphere is used for the amount. The total reflectivity of the test piece, which includes scattering and mirroring. The diameter of the light exit port of the integrating sphere is 20 mm, and the sampling range diameter is 25 mm. The xenon lamp source and the integrating sphere are incident on the integrating sphere at a 90 degree angle. A standard whiteboard or a test piece can be placed directly below the integrating sphere. The standard whiteboard can be a chemically inert material, and the reflectance value reaches 400 nm to 1500 nm. More than 99%, such as WS-1-SL Reflectance Standards sold by Ocean Optics, Inc. The distance between the integrating sphere opening and the standard whiteboard or the piece to be tested is 0.3 mm, and the reflected light amount of the collecting detector is located at an angle of 8 degrees from the open end of the integrating sphere, and is connected to the spectrometer via the optical fiber to the Back-thinned type CCD. The group is used as the signal receiving mode, and its effective wavelength range is 320nm~1074nm; resolution: 1.45nm; accuracy: <0.05% within 10nm, the light signal of reflected light at each wavelength is transmitted to the computer, and the sample to be tested is obtained by calculation. Reflectance spectrum.

The reflectance measuring instrument has a measurable wavelength range of 400 nm to 1000 nm. The measuring method is to first measure the amount of reflected light of the standard whiteboard as a standard value, and then measure the amount of reflected light of the to-be-tested piece. The reflectance spectrum of the test piece is obtained from the ratio of the amount of reflected light of each test wavelength at each wavelength to the amount of reflected light of each wavelength of the standard whiteboard.

Theoretically, the golden color of the single crystal germanium solar cell of the present invention is reflected light generated on the interface of each film layer when the incident light passes through the titanium oxide layer and the transparent inorganic dielectric layer formed on the antireflection layer. The optical path difference generated by the combination of the refraction and the thickness of each layer is formed by mutual interference. Further, since the present invention employs an acid-etched single crystal ruthenium original sheet as a photoelectric conversion group Therefore, the close observation of the gold single crystal germanium solar cell of the present invention does not obviate the mottled color block on the prior art alkali-etched polycrystalline silicon solar cell (as shown in Fig. 8(b)). The appearance of the golden single crystal germanium solar cell of the present invention is as shown in FIG. 2, and the shooting environment light source is an indoor fluorescent lamp with an intensity of about 800 Lux and a shooting angle of about 90 degrees. The solar cell is laid flat in a substantially horizontal manner. The gold it presents has a bright metallic luster. The gold of the present invention contains conventional golden colors and is not limited to the gold shown in FIG. The gold of the present invention includes, but is not limited to, metallic gold, gold-like gold, golden sun, rose gold, and copper gold.

The appearance color of the solar cell is determined by the wavelength distribution of the reflected light in the observer's eye after the incident light is refracted and/or reflected by the interface of each film layer, and the appearance color is affected by the incident angle of the incident light, between the observer and the solar cell. Factors such as angles. That is, the appearance color obtained by looking at the solar cell in a front view and the appearance color obtained by observing the solar cell in a laterally inclined manner may be different.

The present invention provides a high reflectivity gold single crystal germanium solar cell comprising: a high reflectivity single crystal germanium photoelectric conversion substrate; at least one antireflection layer disposed on the high reflectivity single crystal germanium photoelectric conversion substrate; One or more transparent inorganic dielectric layers formed over the anti-reflective layer; and a titanium oxide layer formed over the anti-reflective layer, wherein the one or more transparent inorganic dielectric layers have a relationship of about 1.3 The refractive index to about 2.2, and the gold single crystal germanium solar cell have a reflectance of greater than 20% in the wavelength range of 560 nm to 630 nm.

Different from the prior art solar cell, the original film is subjected to roughening treatment, and the surface of the single crystal bismuth original film of the present invention can reduce surface roughness treatment, such as acid etching (the main component of the etching liquid is hydrofluoric acid) Or a chemical mechanical polishing method, thereby removing the defects formed on the single crystal crucible sheet due to the previous production process, to obtain a relatively flat surface having a higher reflectance, as a subsequent preparation of the golden single crystal germanium solar cell of the present invention. Substrate. The present invention preferably uses an acid etching treatment of the original sheet.

In accordance with an embodiment of the present invention, a titanium oxide layer in a gold single crystal germanium solar cell of the present invention is positioned over the one or more transparent inorganic dielectric layers. In accordance with another embodiment of the present invention, a gold single crystal germanium solar cell of the present invention comprises at least two transparent inorganic dielectric layers, the titanium oxide layer being on at least one of the transparent inorganic dielectric layers.

According to another embodiment of the present invention, the golden single crystal germanium solar cell of the present invention is provided with a titanium oxide layer and a transparent inorganic dielectric layer on the antireflection layer.

According to an embodiment of the present invention, the golden single crystal germanium solar cell of the present invention comprises two transparent inorganic dielectric layers (ie, a first transparent inorganic dielectric layer and a second transparent inorganic dielectric layer) and a titanium oxide layer. It is formed above the anti-reflection layer in the order of the first transparent inorganic dielectric layer, the titanium oxide layer and the second transparent inorganic dielectric layer.

In accordance with an embodiment of the present invention, the gold single crystal germanium solar cell of the present invention has a reflectance of greater than 20%, preferably greater than 25%, and more preferably greater than 30%, in the wavelength range from 530 nm to 630 nm.

The titanium oxide layer of the present invention is formed from undoped titanium oxide. The titanium oxide layer has a thickness of between about 20 nm and about 120 nm, preferably between about 30 nm and about 100 nm, more preferably between about 50 nm and about 80 nm, and has a refractive index between about 2.2 and about 2.6.

Each of the one or more layers of the transparent inorganic dielectric layer of the present invention is independently composed of a transparent inorganic dielectric having a refractive index of between about 1.3 and about 2.2, preferably between about 1.5 and about 2.0. Each of the one or more transparent inorganic dielectric layers independently has a thickness of between about 1 nm and about 200 nm, preferably between about 10 nm and 180 nm, more preferably between about 100 nm and 150 nm. .

Each of the one or more layers of transparent inorganic dielectric is independently selected from the group consisting of oxides of aluminum doped with aluminum, indium tin oxide, oxides of undoped zinc, co-doped with aluminum or aluminum gallium A group of hetero-zinc oxides and niobium nitrides. Each of the one or more transparent inorganic dielectric layers is independently selected from the group consisting of aluminum-doped zinc oxide, indium tin oxide, zinc oxide, and tantalum nitride. More preferably, at least one of the one or more transparent inorganic dielectric layers is formed from an oxide of zinc doped with aluminum.

According to an embodiment of the present invention, the present invention provides a golden single crystal germanium solar cell which exhibits a golden color with a bright metallic luster under sunlight, as shown in FIG. 2, the manufacturing method comprising the following steps:

1. Providing a single crystal germanium wafer substrate (ie, an original sheet), removing only the surface defects of the single crystal germanium in the <100> or <110> direction by acid etching, or removing the single crystal germanium in the <111> direction by acid etching and alkali etching. Surface defects provide a single crystal germanium photoelectric conversion substrate having an acceptable smooth surface and having a high reflectance of more than 30% in the wavelength range of 400 nm to 500 nm in the visible light region.

2. Forming at least one antireflection layer on the single crystal germanium photoelectric conversion substrate.

3. Forming a titanium oxide layer on the antireflective layer.

4. Forming at least one of the one or more transparent inorganic dielectric layers after step 3 or between steps 2 and 3.

3 is a cross-sectional view of a gold single crystal germanium solar cell according to a specific aspect of the present invention, comprising: an acceptable smooth surface and a high reflectance (wavelength range of 400 nm to 500 nm, reflectance greater than 30%) Reflectivity single crystal germanium photoelectric conversion substrate (S); at least one antireflection layer (AR) formed on the high reflectivity single crystal germanium photoelectric conversion substrate; a transparent inorganic dielectric layer (11) and titanium Oxide layer (12).

The photoelectric conversion substrate suitable for use in the etching process of the present invention is a single crystal germanium material known in the art. The aforementioned etching treatment can also be changed to a chemical mechanical polishing method.

The present invention is suitable as a material for the antireflection layer, any suitable material system also known in the art may be used for a solar cell, including monolayer SiN _x film formed by the SiN _x, or containing element nitrogen to silicon ratio of two different For SiN _x films, x can be between 1.1 and 1.3.

The method for forming the antireflection layer, the titanium oxide layer, and the transparent inorganic dielectric layer according to the present invention may be any method known in the art, including DC Magnetron Sputtering, evaporation (evaporation). ), sputtering, chemical vapor deposition (CVD), coating, or other methods known to those skilled in the art to be suitable.

According to an embodiment of the present invention, the present invention provides a gold single crystal germanium solar cell whose visible light band reflectance spectrum exhibits an average reflectance in the wavelength range of 560 to 630 having a reflectance of more than 20%. The observer can observe the golden color of the golden single crystal germanium solar cell of the present invention by observing the vertical side of the front side obliquely or at a specific angle. Taking the gold single crystal germanium solar cell of the present invention laid flat in a substantially horizontal manner as an example, the observer can be at an angle of view of the observer at a viewing angle (ie, the angle between the reflected light of the observer entering the observer's eye and the horizontal line) is about 10 degrees. A golden color is observed in the range of about 90 degrees, preferably about 30 degrees to about 90 degrees.

The gold single crystal germanium solar cell of the present invention has an industrially acceptable conversion efficiency of at least greater than 14%.

The present invention further provides a panel comprising the above solar cell, which is formed by sequentially placing a protective layer and a transparent layer on the color solar cell of the present invention. The protective layer suitable for use in the present invention may be an encapsulating material known in the art, and may be, for example, ethylene vinyl acetate (EVA), polyvinyl butyral (PVB) or other familiar art. Suitable analogs are considered to protect solar cells from exposure to water or moisture. The transparent layer suitable for use in the solar cell panel of the present invention may also be a material known in the art, such as glass.

The following examples are provided to further illustrate the invention and are not intended to limit the scope of the invention.

Example Example 1 Treatment of photoelectric conversion substrate and its reflectance (a) Preparation of polycrystalline germanium film by prior art acid etching

The acid etching solution is a concentration of 3% to 5% hydrofluoric acid.

(b) Preparation of polycrystalline germanium film by prior art alkali etching

The alkali etching solution is a concentration of 0.9% to 1.1% potassium hydroxide.

(c) Preparation of single crystal ruthenium tablets by prior art alkali etching

The alkali etching solution is a concentration of 0.9% to 1.1% potassium hydroxide.

(d) Preparation of acid-etched single crystal bismuth original sheet of the present invention

The acid etching solution is a concentration of 3% to 5% hydrofluoric acid.

The reflectance of the original sheets of the above (a) to (d) in the wavelength range of 400 nm to 800 nm was measured by a reflectance meter, and the results are shown in Fig. 4.

4, the acid-etched single crystal germanium film (d) of the present invention has a high reflectance of more than 30% in the wavelength range of 400 nm to 500 nm, in the visible light range (400 nm to 750). Nm), its reflectivity is greater than 10%. However, the reflectance of the prior art alkali-etched single crystal bismuth original sheet (c) in the wavelength range of 400 nm to 500 nm did not exceed 20%. The reflectance of the acid-etched single crystal germanium sheet (d) of the present invention is at least 1.5 times that of the prior art alkali-etched single crystal germanium sheet (c) in the wavelength range of 400 nm to 500 nm. In addition, observing the reflectance spectra of the polycrystalline bismuth original sheets (a) and (b) in the wavelength range of 400 nm to 500 nm, it is known that the prior art alkali-etched polycrystalline bismuth original sheet (b) is observed only in the wavelength range of about 400 nm to 440 nm. To a reflectance greater than 30%, the reflectivity of the prior art acid-etched polycrystalline germanium (a) in the 400 nm to 500 nm wavelength range does not exceed 30%.

Example 2

On the original sheets of the above Examples 1 (a) to 1 (d), an aluminum-doped zinc oxide and a titanium oxide layer were sequentially formed by magnetron DC sputtering to obtain Examples 2 (a) and 2 (b). ), 2(c) and 2(d) solar cells. The reflectance of the solar cells of the above (a) to (d) in the wavelength range of 400 nm to 800 nm was measured by a reflectance meter, and the results are shown in FIG. 5.

As can be seen from Fig. 5, the solar cell of the present invention (i.e., the oxidation of aluminum doped zinc on the acid-etched single crystal germanium sheet) compared to the prior art solar cells of Examples 2(a) to 2(c) The material obtained after the titanium oxide layer has a significantly higher reflectance in the wavelength range of 550 to 800 nm. In the wavelength range of 560 nm to 630 nm, the solar cell of the present invention has a reflectance higher than that of the prior art alkali-etched single crystal germanium solar cell 2 (c) by at least 2.2 times.

Example 3-1

After removing the surface defects of the single crystal germanium in the <100> direction by acid etching, a single crystal germanium photoelectric conversion substrate having a smooth surface can be obtained. Forming an anti-reflective layer containing SiN _x on the substrate, the reflectance thereof is greater than 25%, and forming a standard process of a blue solar cell known in the prior art, sequentially forming a magnetically controlled DC sputtering method thereon. The high-reflectance gold single crystal germanium solar cell of the present invention is formed by the aluminum-doped zinc oxide and the titanium oxide layer, and the thickness and refractive index of each layer are shown in Table 1-1 below. The reflectance of the solar cell at each wavelength was measured by a reflectance meter, and the results obtained are shown in Fig. 6.

Example 3-2

After removing the surface defects of the single crystal germanium in the <100> direction by acid etching, a single crystal germanium photoelectric conversion substrate having a smooth surface can be obtained. After forming an anti-reflective layer containing SiN _x on the substrate, the reflectance thereof is greater than 30% to manufacture a standard process of a blue solar cell known in the prior art, and the aluminum-doped method is formed by magnetron DC sputtering. After the zinc oxide and the titanium oxide layer, the stacking order, material type, thickness and refractive index of each layer are listed in Table 1-2 below, that is, the high reflectivity gold single crystal germanium solar cell of the present invention is formed. The reflectance of the solar cell at each wavelength was measured by a reflectance meter, and the results obtained are shown in FIG.

Comparative example 1

Forming an anti-reflective layer comprising SiN _1.1 on an acid-etched polycrystalline germanium photoelectric conversion substrate to produce a standard process of a blue solar cell known in the prior art, on which a titanium is formed by magnetron DC sputtering. The oxide and aluminum-doped zinc oxide, the thickness and refractive index of each layer are listed in Table 2 below. The resulting polycrystalline silicon solar cell has an appearance color of brick red as shown in Fig. 8(a).

Comparative example 2

Forming an anti-reflective layer comprising tantalum nitride on the alkali-etched polycrystalline germanium photoelectric conversion substrate to fabricate a standard process of a blue solar cell known in the prior art, and sequentially forming aluminum via magnetron DC sputtering The thickness of the doped zinc oxide and the oxide of titanium are shown in Table 3 below. The appearance of the polycrystalline silicon solar cell obtained by close observation is as shown in FIG. 8(b), which is a solar cell having a distinct mottled color block, and does not exhibit the single and uniform golden color of the golden solar cell of the present invention ( as shown in picture 2). Comparing Fig. 8(b) with the golden color of the golden solar cell of the present invention, the golden solar cell of the present invention exhibits a brighter gold color and a metallic luster.

11‧‧‧Transparent inorganic dielectric layer

12‧‧‧Titanium oxide layer

a‧‧‧The thickness of the anti-reflection layer

AR‧‧‧Anti-reflective layer

b‧‧‧Thickness of transparent inorganic dielectric layer

c‧‧‧Thickness of titanium oxide layer

S‧‧‧High reflectivity single crystal germanium photoelectric conversion substrate

Claims (14)

A gold single crystal germanium solar cell comprising: an acid etched single crystal germanium wafer, which is a single crystal germanium photoelectric conversion substrate having a high reflectance of more than 30% in a wavelength range of 400 nm to 500 nm in the visible light region; At least one antireflection layer disposed on the high reflectivity single crystal germanium photoelectric conversion substrate; one or more transparent inorganic dielectric layers formed over the antireflection layer; and a titanium oxide layer formed on the Above the anti-reflective layer, wherein the one or more transparent inorganic dielectric layers have a refractive index between about 1.3 and about 2.2, and the gold single crystal germanium solar cell has a standard 8 degree angle in a wavelength range of 560 nm to 630 nm. The velvet area fractional reflectance meter has a reflectance greater than 20%. The gold single crystal germanium solar cell of claim 1, wherein the titanium oxide layer is over the one or more transparent inorganic dielectric layers. The gold single crystal germanium solar cell of claim 1, comprising at least two transparent inorganic dielectric layers, the titanium oxide layer being on at least one of the transparent inorganic dielectric layers. The gold single crystal germanium solar cell according to any one of claims 1 to 3, which has a reflectance of more than 30% in a wavelength range of 560 nm to 600 nm. The gold single crystal germanium solar cell according to any one of claims 1 to 3, which has a reflectance spectrum as shown in Fig. 6 in a wavelength range of 400 nm to 800 nm. The gold single crystal germanium solar cell according to any one of claims 1 to 3, which has the reflectance spectrum shown in Fig. 7 in the wavelength range of 400 nm to 800 nm. The gold single crystal germanium solar cell of any one of claims 1 to 3, wherein the titanium oxide layer has a refractive index of between about 2.2 and about 2.6. The gold single crystal germanium solar cell of any one of claims 1 to 3, wherein the titanium oxide layer has a thickness of between about 20 nm and about 120 nm. The gold single crystal germanium solar cell of any one of claims 1 to 3, wherein each of the one or more transparent inorganic dielectric layers independently has a refractive index of between about 1.5 and about 2.0. The gold single crystal germanium solar cell of any one of claims 1 to 3, wherein each of the one or more transparent inorganic dielectric layers independently has a thickness of between about 1 nm and about 200 nm. The gold single crystal germanium solar cell of any one of claims 1 to 3, wherein each of the one or more transparent inorganic dielectric layers independently has a thickness of between about 10 nm and about 180 nm. The gold single crystal germanium solar cell of any one of claims 1 to 3, wherein each of the one or more transparent inorganic dielectric layers is independently selected from the group consisting of an oxide of aluminum doped with aluminum, indium tin oxide, A group of undoped zinc oxide, an aluminum or aluminum gallium co-doped zinc oxide, and a niobium nitride. The gold single crystal germanium solar cell according to any one of claims 1 to 3, wherein each of the one or more transparent inorganic dielectric layers is independently selected from the group consisting of aluminum-doped zinc oxide, indium tin oxide, a group consisting of zinc oxide and tantalum nitride. The gold single crystal germanium solar cell of any one of claims 1 to 3, wherein at least one of the one or more transparent inorganic dielectric layers is formed of an oxide of zinc doped with aluminum.