CN108520901A - Thin film solar cell and manufacturing method thereof - Google Patents

Abstract

The invention discloses a thin-film solar cell and a manufacturing method thereof. The thin-film solar cell comprises: a conductive back electrode support structure; a first electrode layer on the back electrode support structure; a battery active layer on the first electrode layer layer; and a second electrode layer on the battery active layer; wherein the back electrode support structure is electrically connected to the first electrode layer and supports the battery active layer. The thin-film solar cell and the manufacturing method thereof in the embodiments of the present invention simplify the manufacturing process of the flip-chip thin-film solar cell and improve the production efficiency.

Description

Thin film solar cell and manufacturing method thereof

technical field

Embodiments of the present invention relate to the field of semiconductor technology, in particular to a thin-film solar cell and a manufacturing method thereof.

Background technique

As a clean energy source, solar cells play an important role in national defense and civilian applications. In particular, thin-film solar cells have been widely used in many fields, especially in aerospace or aviation equipment that are sensitive to load weight, due to their advantages of lightness, lightness, softness, and bendability. Flexible thin-film solar cells are usually fabricated using the flip-chip method. During its preparation, the epitaxial layer of the battery needs to be peeled off from the original growth substrate, and then the epitaxial layer is transferred to a flexible transfer substrate, on which subsequent electrodes are fabricated. It has been reported that thin film solar cells with good flexibility can be obtained by using polyimide (PI) and other insulating material films as transfer substrates. However, a disadvantage of this structure is that the back electrode needs to be drawn out on a flexible non-conductive substrate, which increases the steps of the entire battery manufacturing process and affects the available area of the epitaxial wafer.

Therefore, it is necessary to provide a thin film solar cell with an improved structure to solve the above problems.

Contents of the invention

Embodiments of the present invention provide a thin-film solar cell and a manufacturing method thereof, which can at least simplify the manufacturing process of flip-chip thin-film solar cells and improve production efficiency.

According to one aspect of the present invention, there is provided a thin film solar cell comprising: a conductive back electrode support structure; a first electrode layer on the back electrode support structure; a battery active layer on the first electrode layer layer; and a second electrode layer on the battery active layer; wherein the back electrode support structure is electrically connected to the first electrode layer and adapted to support the battery active layer.

According to some embodiments, the back electrode support structure includes a porous metal layer.

According to some embodiments, the porous metal layer includes porous copper.

According to some embodiments, the porosity of the porous metal layer is between 40%-70%, preferably between 50%-60%; the average pore size is less than 1 μm, preferably less than 500nm.

According to some embodiments, the density of the back electrode support structure is not greater than 10.0 g/cm ³ , preferably not greater than 5.0 g/cm ³ .

According to some embodiments, the back electrode support structure includes a conductive metal layer with a density not greater than 5.0 g/cm ³ .

According to some embodiments, the conductive metal layer includes one or more of titanium, chromium, aluminum, magnesium, and zinc.

According to some embodiments, the back electrode support structure includes a carbon fiber layer with a density not greater than 5.0 g/cm ³ .

According to some embodiments, the back electrode support structure has a thickness between 15 μm-50 μm, preferably between 20 μm-40 μm, more preferably between 20-30 μm.

According to some embodiments, the battery active layer includes a gallium arsenide battery active layer.

Another aspect of the embodiments of the present invention also provides a method for preparing the above-mentioned thin film solar cell, wherein the porous metal layer is prepared by a dealloying method or a hydrogen bubble template method.

Another aspect of the embodiments of the present invention also provides a method for preparing the above-mentioned thin film solar cell, comprising: providing a temporary substrate; epitaxially growing a sacrificial layer and a battery active layer on the temporary substrate; forming a first electrode layer; forming a back electrode support structure on the first electrode layer, the back electrode support structure is conductively connected to the first electrode layer; forming a protective film sealing the back electrode support structure on the back electrode support structure; Use corrosive liquid to corrode the sacrificial layer to realize the stripping of the temporary substrate; use the back electrode support structure as the support substrate, on the side of the battery active layer away from the back electrode support structure, that is, the new stripped battery active layer A second electrode layer is formed on the surface.

According to some embodiments, the method further includes: after peeling off the temporary substrate and the sacrificial layer, removing the protective film.

According to some embodiments, forming a protective film sealing the back electrode support structure on the back electrode support structure includes: before forming the first electrode layer on the battery active layer, disposing a ring of peripheral protective film on the outer periphery of the battery active layer , and then the first electrode layer and the back electrode support structure are formed in the peripheral protective film; after the first electrode layer and the back electrode support structure are formed in the peripheral protective film, the active layer is provided A cover protection film, the cover protection film and the peripheral protection film are connected to seal the first electrode layer and the back electrode support structure.

According to some embodiments, the back electrode support structure has a thickness between 15 μm-50 μm, preferably between 20 μm-40 μm, more preferably between 20-30 μm.

According to some embodiments, the etchant is capable of corroding the conductive metal layer as the back electrode support structure.

According to the thin-film solar cell and its manufacturing method according to the embodiment of the present invention, by providing a conductive back electrode support structure, the back electrode support structure and the back electrode (first electrode layer) are conductively connected to replace the traditional transfer liner of insulating material The bottom not only can support the active layer of the battery, but also does not need to lead out the back electrode, which simplifies the preparation process of the flip-chip thin film solar cell, improves the production efficiency, and does not affect the available area of the epitaxial wafer.

Description of drawings

Other objects and advantages of the present invention will be apparent from the following description of the present invention with reference to the accompanying drawings, and may help to provide a comprehensive understanding of the present invention.

Fig. 1 shows a schematic structural view of a thin film solar cell according to an exemplary embodiment of the present invention;

Fig. 2 shows the schematic diagram of the process of a kind of preparation method of the thin film solar cell of Fig. 1;

Fig. 3 shows a schematic diagram of the process of another preparation method of the thin film solar cell of Fig. 1; and

FIG. 4 shows a schematic diagram of a process of forming a protective film sealing a back electrode support structure according to an exemplary embodiment of the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions of the embodiments of the present invention in conjunction with the accompanying drawings of the embodiments of the present invention. Unless otherwise defined, in the embodiments of the present invention and in the drawings, the same reference numerals represent the same meaning. For the sake of clarity, in the drawings used to describe the embodiments of the present invention, the thickness of layers or regions is enlarged; and, in the drawings of some embodiments of the present invention, only structures related to the concept of the present invention are shown, Other structures can refer to the general design. In addition, some drawings only illustrate the basic structures of the embodiments of the present invention, and details are omitted.

Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the usual meanings understood by those having ordinary skill in the field to which the present invention belongs. "First", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Words such as "comprising" or "comprising" express an open meaning and do not exclude other elements, components, parts or items other than those explicitly listed. Words such as "connected" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "Down", "Left", "Right" and so on are only used to indicate the relative positional relationship. When the absolute position of the described object changes, the relative positional relationship may also change accordingly. It will be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" or "under" another element, it can be "directly on" or "under" the other element. ”, or there may be intermediate elements.

Fig. 1 shows a schematic structural view of a thin film solar cell 100 according to an exemplary embodiment of the present invention. As shown in Figure 1, a thin film solar cell 100 includes a conductive back electrode support structure 1; a first electrode layer 2 on the back electrode support structure 1; a battery active layer 3 on the first electrode layer 2; The second electrode layer 4 on the active layer 3 . The back electrode support structure 1 is conductively connected with the first electrode layer 2 and supports the active layer 3 of the battery.

Thin-film solar cell 100 may be any suitable single-junction, double-junction or multi-junction solar cell. The battery active layer 3 may include conventional epitaxial layer structures such as an N-type contact layer, an absorber layer, and a P-type contact layer. In order to obtain higher photoelectric conversion efficiency, the thin-film solar cell 100 can be a GaAs-based thin-film solar cell, and its cell active layer includes a gallium arsenide cell active layer.

In one embodiment, taking a triple-junction thin-film gallium arsenide (GaAs) solar cell as an example, the cell active layer 3 may sequentially include a P-type InGaAs contact layer, an InGaAs bottom cell, a first tunnel junction, a GaAs middle cell, a second Two tunnel junctions, a GaInP top cell and an N-type GaAs contact layer. Wherein, the P-type InGaAs contact layer is connected to the first electrode layer 2, and the N-type GaAs contact layer is connected to the second electrode layer 4. The thickness of the active layer 3 of the battery is generally relatively thin. Take thin-film gallium arsenide solar cells as an example, the thickness generally ranges from 3um-12um from single-junction solar cells to triple-junction solar cells.

In this embodiment, the first electrode layer 2 is used as the back electrode, and the second electrode layer 4 is used as the front electrode, and light enters the thin film solar cell 100 from the side of the front electrode. Any suitable electrode material can be selected for the first electrode layer 2 and the second electrode layer 4, which is not limited here. Typically, the materials of the first electrode layer 2 and the second electrode layer 4 may include one or more of copper, silver, gold, and molybdenum. The thickness of the first electrode layer 2 and the second electrode layer 4 is generally 3 µm or less, preferably 2 µm or less, more preferably 1 µm or less. The thickness of the electrode layer is relatively thin, which is conducive to reducing the thickness of the entire thin film solar cell, thereby reducing the weight of the thin film solar cell and increasing the flexibility of the thin film solar cell.

The back electrode support structure 1 can be made of conductive materials, for example, metal conductive materials can be directly deposited on the first electrode layer 2, and electrically connected with the first electrode layer 2. The back electrode support structure 1 is used to support the active layer 3 of the battery. In particular, since the thickness of the cell active layer 3 is very thin, usually only a few microns thick, in the process of preparing the thin-film solar cell 100 by the flip-chip method, when the temporary substrate such as a GaAs substrate is peeled off, if there is no supporting structure, so The thin battery active layer 3 is difficult to peel off, or is easily broken during the peeling process. In the thin film solar cell according to the embodiment of the present invention, since the back electrode support structure 1 is formed on the back electrode, that is, one side of the first electrode layer 1, the back electrode support structure 1 can be used in the process of peeling off the temporary substrate. Support the battery active layer 3 as a supporting substrate; and after peeling off the temporary substrate, the back electrode supporting structure 1 can continue to serve as a supporting substrate, so as to continue the subsequent preparation process of the battery on the battery active layer 3, such as making The front electrode, that is, the second electrode layer 4, finally forms a complete thin film solar cell.

According to the thin-film solar cell of the embodiment of the present invention, compared with non-conductive materials such as polyimide as the transfer substrate, the back electrode support structure and the back electrode (first electrode) are conductively connected by providing a conductive back electrode support structure. , does not need to lead out the back electrode additionally, simplifies the preparation process of the flip-chip thin-film solar cell, improves the production efficiency, and does not affect the available area of the epitaxial wafer.

In some embodiments, in order to play a good supporting role, the thickness of the back electrode support structure 1 can be selected between 15 μm-50 μm, preferably between 20 μm-40 μm, more preferably between 20-30 μm. An appropriate thickness of the back electrode support structure is conducive to achieving a balance between the overall weight of the battery and the support function of the back electrode support structure, which can not only ensure sufficient support, but also avoid increasing the weight of thin-film solar cells and losing their flexibility and lightness. .

In some applications of thin-film solar cells, especially in aerospace or aerospace equipment that is sensitive to load weight, in order to further reduce the weight of thin-film solar cells and better utilize the advantages of thin-film solar cells, the back electrode support structure 1 The density is set to be not greater than 10.0 g/cm ³ , preferably not greater than 8 g/cm ³ , more preferably not greater than 5.0 g/cm ³ .

In order to obtain the desired density of the back electrode support structure 1 at a certain thickness, according to some embodiments, the back electrode support structure 1 is made of a light metal material, such as one of titanium, chromium, aluminum, magnesium, and zinc. or multiple materials. Preferably, the lightweight metal material has a density not greater than 5.0 g/cm ³ . Metal titanium has a density of 4.5g/cm ³ , and it is more effective as an electrode support material.

According to other embodiments, in order to reduce the weight or density of the back electrode support structure 1 , the back electrode support structure 1 may adopt a porous metal layer structure. In addition, the porous structure has good heat dissipation performance and can also improve the performance of the battery. Preferably, the density of the porous metal layer is not greater than 5.0 g/cm ³ . These embodiments are particularly suitable for heavier metallic materials such as copper (Cu), silver (Ag), gold (Au), molybdenum (Mo), and the like. In order to reduce the manufacturing cost of the battery, the porous metal layer can be formed from abundant and cheap metal materials. For example, commonly used copper is used to prepare porous copper as the back electrode support structure 1 . The porous metal layer can be prepared by dealloying method or template method, such as hydrogen bubble template method. The porosity of the prepared porous metal layer is between 40%-70%, preferably between 50%-60%; the average pore size is less than 1 μm, preferably less than 500nm. By selecting an appropriate porosity and pore size, it can be ensured that the back electrode support structure 1 has sufficient strength and at the same time has as light a weight as possible.

The basic process of the dealloying method is to first prepare an alloy of two or more metals, and then use inorganic acid to corrode the more active metals (zinc, chromium, manganese, nickel, etc.) in the alloy, leaving only the inert metal that does not react with the acid. Metals (gold, copper, platinum, etc.). As one of the metals in the alloy is corroded and dissolved, voids are left in the positions of the original grains or atoms, forming a three-dimensional porous structure. The porosity of the porous metal layer prepared by the dealloying method is closely related to the atomic ratio in the alloy, crystal phase and reaction temperature, and its porosity and pore size are relatively easy to control. The porous metal layer prepared by the dealloying method may include metals with stable physical and chemical properties and good electrical conductivity at room temperature. In some embodiments, the porous metal layer may include porous copper, porous silver, porous gold, and porous molybdenum.

The template method refers to using a material with a nanoporous structure as a template, then depositing the required metal on the template by electroless plating or electroplating, and finally removing the template by chemical corrosion to obtain a porous metal structure. Among them, the hydrogen bubble template method uses the hydrogen bubbles generated during the electroplating process as a dynamic template to form a porous structure in the deposit. During the electroplating process, a large number of hydrogen bubbles will be generated by the cathode reaction. Since there are no metal ions available in the bubbles, there is no metal deposition, and pores can be formed in the deposited metal. Using the hydrogen bubble template method to prepare porous copper can be used in conjunction with the existing copper electroplating process in battery preparation without adding additional equipment and other costs, which is convenient and practical.

In some other embodiments, the back electrode support structure 1 may include a carbon fiber layer with a density not greater than 5.0 g/cm ³ . Since carbon fiber is a good conductive material and light in weight, the carbon fiber layer is used instead of the conductive metal layer to prepare the back electrode support structure, which can also play the same role as the conductive metal layer, without additionally leading out the back electrode, which simplifies the battery preparation process process.

FIG. 2 shows a schematic diagram of the process of a manufacturing method of the thin film solar cell 100 in FIG. 1 . As shown in Figure 2, the preparation method of the thin-film solar cell 100 of the embodiment of the present invention adopts flip chip process, comprises the following steps:

providing a temporary substrate 5;

On the temporary substrate 5, epitaxially grow the sacrificial layer 6 and the battery active layer 3 in sequence;

sequentially forming a first electrode layer 2 and a back electrode support structure 1 on the battery active layer 3;

Etching the sacrificial layer 6 with an etching solution to realize the peeling and summing of the temporary substrate 5 and the active layer 3 of the battery;

With the back electrode support structure 1 as the supporting substrate, the prepared epitaxial layer of the battery is inverted, that is, the back electrode support structure 1 is the bottom layer, the first electrode layer 2 is the middle layer, and the battery active layer 3 is the top layer. The second electrode layer 4 is prepared on the active layer 3 . The second electrode layer 4 is located on the other side of the battery active layer 3 away from the back electrode support structure 1.

It can be seen that, in order from bottom to top, the thin film solar cell 100 is inverted from the initial structure of "cell active layer 3-first electrode layer 2-back electrode support structure 1" to the final "back electrode support structure 1- The structure of the first electrode layer 2-battery active layer 3-second electrode layer 4". Taking a triple-junction thin-film gallium arsenide solar cell as an example, in the order from bottom to top, the active layer 3 of the cell is inverted from the initial structure of "GaInP top cell-GaAs middle cell-InGaAs bottom cell" to the final "InGaAs bottom cell -GaAs middle cell-GaInP top cell" structure.

The temporary substrate 5 can include various battery substrate materials such as GaAs. In the above-mentioned preparation process, the temporary substrate 5 after being stripped can be used for the next battery preparation. Such repeated use can save costs and resources. The sacrificial layer 6 is corroded by the etchant when the temporary substrate 5 is peeled off, so that the temporary substrate 5 is peeled off from the battery active layer.

In the process of preparing the thin film solar cell 100 of FIG. 1 , the inventors of the present invention found a problem: in order to reduce the weight of the thin film solar cell, light conductive metal materials such as titanium, chromium, When one or more of aluminum, magnesium, and zinc are used, because light metal materials are usually chemically active and easily react with acids, they are easily corroded by commonly used acidic corrosion solutions when the temporary substrate 5 is peeled off, resulting in failure to serve as The material of the back electrode support structure. In order to solve this technical problem, the inventors conducted research. In the preparation method of the thin film solar cell 100 shown in FIG. The step of the protective film; afterward, when peeling off the sacrificial layer 6 and the temporary substrate 5, since the back electrode support structure 1 is sealed and protected by the protective film, it will not be in contact with the acidic etching solution, so that it will not chemically react with the etching solution, Therefore, it can be completely preserved, and it can be used as a supporting substrate for the active layer 3 when the temporary substrate 5 is peeled off, and the active layer 3 will not be broken. Further, in the subsequent process of preparing the second electrode layer 4, the back electrode support structure 1 can be used as a supporting substrate to facilitate the preparation of the second electrode layer 4 and other structures.

FIG. 3 shows a schematic diagram of the process of another manufacturing method of the thin film solar cell 100 in FIG. 1 . According to a specific embodiment of the present invention, as shown in Figure 3, the above-mentioned method for preparing thin-film solar cell 100 comprises:

providing a temporary substrate 5;

Epitaxial growth of the sacrificial layer 6 and the active layer 3 of the battery on the temporary substrate 5;

Form the first electrode layer 2 on the battery active layer 3, specifically, one or more metal materials in copper, silver, gold, molybdenum can be evaporated on the battery active layer 3 as the first electrode layer 2;

Next, the back electrode support structure 1 is formed on the first electrode layer 2, so that the back electrode support structure 1 and the first electrode layer 2 are conductively connected. Specifically, the back electrode support structure 1 can be directly deposited on the first electrode layer 2 by magnetron sputtering. A light metal layer with a thickness of about 20 μm, such as one or more of titanium, chromium, aluminum, magnesium, zinc, as the back electrode support structure 1;

Next, a protective film 7 that seals the back electrode support structure 1 is formed on the back electrode support structure 1, and the protective film 7 can be made of materials such as resin or plastic that do not chemically react with the corrosive solution;

Afterwards, the sacrificial layer 6 is etched with an etchant to realize the peeling off of the temporary substrate 5;

Next, optionally, removing the protective film 7;

Afterwards, the back electrode support structure 1 can be used as a supporting substrate, the formed battery structure can be inverted, and then the second electrode layer 4 can be prepared on the battery active layer 3, specifically, the second electrode layer 4 can be evaporated on the battery active layer 3 One or more metal materials among copper, silver, gold and molybdenum are used as the second electrode layer 4 .

Note that the above steps can be adjusted in order or performed in parallel without affecting the battery preparation. For example, the step of removing protective film 7 may also be performed after forming second electrode layer 4 .

Fig. 4 shows a schematic diagram of a process of forming a protective film 7 sealing the back electrode support structure 1 according to an exemplary embodiment of the present invention. As shown in Figure 4, a protective film 7 sealing the back electrode support structure 1 is formed on the back electrode support structure 1, specifically comprising:

Before forming the first electrode layer 2 on the battery active layer 3, a circle of peripheral protective film 71 (primary sticking film) is set on the outer periphery of the battery active layer 3, and then the first electrode layer 2 and the back The electrode support structure 1 is formed in the peripheral protection film 71; and

After the first electrode layer 2 and the back electrode support structure 1 are formed in the peripheral protective film 71, a cover protective film 72 (secondary film) is arranged on the active layer 3, so that the cover protective film 72 and the peripheral protective film 71 to seal the first electrode layer 2 and the back electrode support structure 1 .

In the preparation method of the above-mentioned embodiment, when the first electrode layer 2 and the back electrode support structure 1 are formed by evaporation and sputtering, the jig can be arranged on the peripheral protective film 71 formed on the outer periphery of the active layer 3 of the battery, so that the first electrode layer 2 An electrode layer 2 and a back electrode support structure 1 are only formed in the peripheral protective film 71; at the same time, since the peripheral protective film 71 is formed in the jig area, it does not occupy additional battery area; and can be sequentially formed after one-time installation of the jig The first electrode layer 2 and the back electrode support structure 1 save the process.

Of course, the formation of the protective film 7 is not limited to the above-mentioned method of pasting the film twice, and it can also be formed once after the formation of the first electrode layer 2 and the back electrode support structure 1 to ensure that the first electrode layer 2 and the back electrode support structure 1 are in a sealed state. status.

Optionally, when the first electrode layer 2 is made of copper (Cu), silver (Ag), gold (Au), molybdenum (Mo) and other metal materials that do not react with the corrosion solution, it is also possible to support only the back electrode A protective film is formed around the structure 1 without forming a protective film that seals the first electrode layer 2 .

In some embodiments, the thickness of the back electrode support structure 1 is between 15 μm-50 μm, preferably between 20 μm-40 μm. If the thickness is too small, the supporting effect on the active layer 3 of the battery is insufficient; if the thickness is too large, the density will be increased and the weight advantage of the thin film solar battery will be weakened.

In some embodiments, the thin film solar cell 100 may further include other layer structures as required. For example, structures such as a back reflection layer, a diffusion layer, an adhesion layer, and an electrode contact layer can be added between the battery active layer 3 and the first electrode layer 2. The present invention is not limited thereto.

The method for preparing the back electrode support structure 1 of the thin-film solar cell shown in Figure 1 will be illustrated by specific examples below, and the methods for preparing other layers can be conventional methods, and the detailed description thereof will be omitted here.

example 1

The porous copper layer is prepared by dealloying method as the back electrode support structure 1 shown in Figure 1-2, and the steps are as follows:

Evaporate and form a first electrode layer 2, such as a Cu electrode layer, on the battery active layer 3 carried by the temporary substrate 5;

A 40um copper-zinc alloy is deposited by sputtering on the first electrode layer 2, wherein the atomic ratios of copper and zinc in the target are about 50% each, and the temperature of the first electrode layer 2 is controlled below 100°C during sputtering;

Place the intermediate product loaded with copper-zinc alloy in a mixed solution composed of NH ₄ Cl with a mass concentration of 20g/L, HCl with a mass fraction of 37%, and a volume ratio of NH4Cl and HCl of 1:10, and react in a water bath at 55°C More than two hours, until no bubbles are produced, so as to remove the zinc in the copper-zinc alloy;

The intermediate product after the water bath reaction was taken out and dried, and put into a quartz tube annealing furnace, and annealed for 60 minutes in a _N2 atmosphere at a maximum temperature of 250°C to obtain a porous copper layer;

The porosity of the porous copper layer prepared in Example 1 is about 50%, the pore diameter is less than 1um, the thickness is the original sputtered copper-zinc alloy thickness of 40um, and the density is below 4g/cm ³ , the porous copper layer can be used as the back electrode support structure 1.

Example 2

The porous copper layer is prepared by the hydrogen bubble template method as the back electrode support structure 1 shown in Figure 1-2, and the steps are as follows:

Evaporate and form a first electrode layer 2, such as a Cu electrode layer, on the battery active layer 3 carried by the temporary substrate 5;

Put the intermediate product carrying the first electrode layer 2 into a quartz tube annealing furnace, and anneal for 60 minutes at a maximum temperature of 250° C. in an _N2 atmosphere;

With the first electrode layer 2 as the cathode, electroplating is carried out in the CuSO4 system electrolyte, wherein the electrolyte includes CuSO4, 147g/L H2SO4, 70.2g/L Na2SO4, 30g/L For HCHO, the volume fractions are 0.25mL/L of HCl and 0.25mL/L of polyethylene glycol; and the temperature is controlled at 25°C, the current density is 3A/cm ² , and the electroplating time is 20 seconds.

After the electroplating is completed, a porous copper layer is obtained as the back electrode support structure 1 .

The electrolytic solution used in example 2 is obtained by adding formaldehyde and polyethylene glycol additives in the electrolytic solution of existing copper plating, without adding additional equipment and other costs, convenient and practical.

Example 3

To prepare a GaAs thin film solar cell with a titanium metal layer as the back electrode support structure 1 shown in Figures 1, 3 and 4, the steps are as follows:

Provide a GaAs temporary substrate 5 with a thickness of 350 μm;

On GaAs temporary substrate 5, epitaxially grow nanoscale AlAs sacrificial layer 6 and GaAs cell active layer 3;

A peripheral protective film 71 of resin material is provided on the outer periphery of the active layer 3 of the GaAs battery;

Install the fixture at the position of the peripheral protective film 71, then vapor-deposit a layer of copper with a thickness of less than 1 μm on the active layer 3 of the GaAs battery as the first electrode layer 2, and directly deposit it on the first electrode layer 2 by magnetron sputtering. A titanium metal layer with a thickness of about 20 μm is deposited on the layer 2 as the back electrode support structure 1, wherein the first electrode layer 2 and the back electrode support structure 1 are formed in the peripheral protective film 71 due to the shielding of the jig;

Next, a cover protective film 72 of a resin material is set above the GaAs battery active layer 3, so that the cover protective film 72 and the peripheral protective film 71 are connected to seal the first electrode layer 2 and the back electrode support structure 1;

Afterwards, the sacrificial layer 6 is etched with an etching solution to achieve the peeling off of the GaAs temporary substrate 5;

Next, remove the cover protection film 72 and the peripheral protection film 71;

Afterwards, with the back electrode support structure 1 as the supporting substrate, the formed GaAs battery structure is turned upside down, and then a copper layer is evaporated on the active layer of the GaAs battery as the second electrode layer 4.

While certain embodiments of the present general inventive concept have been shown and described, those of ordinary skill in the art will understand that the described embodiments represent some, and not all, embodiments of the present invention. Based on the described embodiments, various changes can be made to these embodiments without departing from the principles and spirit of the general inventive concept. Components of the various embodiments may be combined or substituted for each other without causing conflicts. The scope of the invention is defined by the claims and their equivalents.

Claims (16)

1. A thin-film solar cell, comprising: Conductive back electrode support structure; a first electrode layer on the back electrode support structure; a battery active layer on the first electrode layer; and a second electrode layer on the active layer of the battery; Wherein, the back electrode support structure is electrically connected to the first electrode layer and supports the active layer of the battery. 2. The thin film solar cell according to claim 1, wherein the back electrode support structure comprises a porous metal layer. 3. The thin film solar cell according to claim 2, wherein the porous metal layer comprises porous copper. 4. The thin film solar cell according to claim 2, characterized in that, the porosity of the porous metal layer is between 40%-70%, preferably between 50%-60%; the average pore size is less than 1 μm, Preferably less than 500 nm. 5 . The thin film solar cell according to claim 1 , wherein the density of the back electrode support structure is not greater than 10.0 g/cm ³ , preferably not greater than 5.0 g/cm ³ . 6 . The thin film solar cell according to claim 1 , wherein the back electrode support structure comprises a conductive metal layer with a density not greater than 5.0 g/cm ³ . 7. The thin film solar cell according to claim 6, wherein the conductive metal layer comprises one or more of titanium, chromium, aluminum, magnesium and zinc. 8 . The thin film solar cell according to claim 1 , wherein the back electrode support structure comprises a carbon fiber layer with a density not greater than 5.0 g/cm ³ . 9. The thin-film solar cell according to any one of claims 1-8, characterized in that, the thickness of the back electrode support structure is between 15 μm-50 μm, preferably between 20 μm-40 μm, more preferably 20 μm Between -30μm. 10. The thin film solar cell according to claim 1, wherein the cell active layer comprises a GaAs cell active layer. 11. A method for preparing the thin-film solar cell according to any one of claims 2-4, wherein the porous metal layer is prepared by a dealloying method or a hydrogen bubble template method. 12. A method for preparing the thin film solar cell according to any one of claims 6-7, comprising: Provide a temporary substrate; Epitaxial growth of the sacrificial layer and the active layer of the battery on the temporary substrate; forming a first electrode layer on the battery active layer; forming a back electrode support structure on the first electrode layer, the back electrode support structure is electrically connected to the first electrode layer; forming a protective film sealing the back electrode support structure on the back electrode support structure; Etching the sacrificial layer with corrosive solution to achieve the peeling off of the temporary substrate; Using the back electrode support structure as a supporting substrate, a second electrode layer is formed on the new surface where the active layer of the battery is peeled off. 13. The method according to claim 12, further comprising: after peeling off the temporary substrate and the sacrificial layer, removing the protective film. 14. The method according to claim 12, wherein forming a protective film sealing the back electrode support structure on the back electrode support structure comprises: Before forming the first electrode layer on the active layer of the battery, a peripheral protective film is provided on the outer periphery of the active layer of the battery, and then the first electrode layer and the back electrode support structure are formed on the outer periphery of the protective film. inside the membrane; After the first electrode layer and the back electrode supporting structure are formed in the peripheral protective film, a cover protective film is provided on the active layer, and the cover protective film and the peripheral protective film are connected to seal the first electrode layer. Electrode layer and back electrode support structure. 15. The method according to claim 12, wherein the thickness of the back electrode support structure is between 15 μm-50 μm, preferably between 20 μm-40 μm, more preferably between 20-30 μm. 16. The method of claim 12, wherein the etchant is capable of corroding a conductive metal layer as a back electrode support structure.