CN102496637A - Solar cell with intermediate bands and photoelectric conversion film material of solar cell - Google Patents

Abstract

The invention provides a solar cell with intermediate bands. The solar cell comprises a substrate, a back electrode, a complementary type film, a photoelectric conversion film material and a metal electrode, wherein the back electrode is arranged on the substrate; the complementary type film is arranged on the back electrode; the photoelectric conversion film material is arranged on the complementary type film and is a photoelectric conversion layer with the intermediate bands; and a parent material of the photoelectric conversion layer with the intermediate band is TiO2, ZnO, Si or III-V family semiconductor materials. The invention provides the solar cell and the photoelectric conversion film material forming the solar cell with high conversion efficiency, stable cell property and reasonable manufacturing cost.

Description

A kind of intermediate energy band solar cell and its photoelectric conversion film material

technical field

The invention relates to a solar cell and a photoelectric conversion thin film material thereof, in particular to a solar cell with intermediate bands.

Background technique

Due to the increasing global demand for energy and the improvement of environmental protection awareness, countries around the world have been researching and developing various alternative clean energy sources, among which solar energy has attracted the most attention. Solar energy has the advantages of being inexhaustible and inexhaustible, and it is an ideal clean energy for human beings to solve the problems of energy depletion and environmental pollution. Solar devices using the principle of photoelectric conversion, especially photovoltaic cells, are the main form and carrier of energy utilization.

Since Bell Laboratories in the United States first developed silicon solar cells in the 1970s, solar cells have made great progress, and there are many types, typically silicon solar cells, Cu(In, Ga)Se ₂ (CIGS), CdTe , Cu ₂ ZnSn(Se, S) ₄ (CZTS) and other thin film batteries and dye-sensitized solar cells.

The fundamental reason why solar energy is difficult to be widely used is limited by the low photoelectric conversion efficiency of current devices and the high manufacturing cost. Thin-film cells such as monocrystalline silicon cells and CIGS have high conversion efficiency, but there are bottlenecks such as complex processes, expensive raw materials, or environmental pollution. Although dye-sensitized solar cells are relatively simple to manufacture, they face the problems of low conversion efficiency and battery stability.

To sum up, the art lacks a solar cell with high conversion efficiency, stable cell and reasonable manufacturing cost. Therefore, there is an urgent need in this field to develop a solar cell with high conversion efficiency, stable cell and reasonable manufacturing cost and the photoelectric conversion thin film material constituting the cell.

Contents of the invention

The first object of the present invention is to obtain a solar cell with high conversion efficiency, stable cell and reasonable manufacturing cost.

The second object of the present invention is to obtain a photoelectric conversion film material for a solar cell with high conversion efficiency, stable cell and reasonable manufacturing cost.

The third object of the present invention is to obtain a method for preparing a photoelectric conversion thin film material.

The fourth object of the present invention is to obtain an application of the photoelectric conversion thin film material of the present invention in improving photoelectric conversion efficiency.

In a first aspect of the present invention there is provided an intermediate band solar cell comprising:

Substrate;

a back electrode disposed on the substrate;

a complementary thin film on the back electrode;

A photoelectric conversion thin film material provided on the complementary thin film; wherein, the photoelectric conversion thin film material is a photoelectric conversion layer with an intermediate energy band; the matrix material of the photoelectric conversion layer with an intermediate energy band is TiO ₂ , ZnO , Si or III-V semiconductor materials;

as well as

metal electrodes.

In a specific embodiment of the present invention, the intermediate energy band intermediate band solar cell includes:

Substrate;

a back electrode disposed on the substrate;

a complementary thin film on the back electrode;

The photoelectric conversion thin film material provided on the complementary thin film; the photoelectric conversion thin film material is a photoelectric conversion layer with an intermediate energy band; wherein the matrix material of the photoelectric conversion layer with an intermediate energy band is preferably TiO ₂ , and also Materials such as ZnO, Si or III-V semiconductors can be chosen; and

metal electrodes.

In a specific embodiment of the present invention, the matrix material of the photoelectric conversion layer with an intermediate energy band is TiO ₂ .

In a specific embodiment of the present invention, the matrix material of the photoelectric conversion layer with an intermediate energy band contains 1-5 atomic % of impurity atoms or pairs of impurity atoms, and the percentage is calculated by the molar ratio of the matrix material.

In a specific embodiment of the present invention, the impurity atoms are asymmetric or non-compensatory n-p co-doped impurity atoms.

In a specific embodiment of the present invention, the impurity atom pairs are unequal or non-compensatory n-p atom pair combinations.

The "n-p atom pair combination" is the combination of n-type and p-type atom pairs.

In a preferred example, the n-type atoms doped into the host material donate electrons and the p-type atoms donate holes, but the number of electrons and holes donated by the two are not equal.

In a specific embodiment of the present invention, when TiO ₂ is used as the parent material, the combination of unequal np atom pairs is selected from Cr-N, Mo-N, WN, Mo-P, or WP.

In a specific embodiment of the present invention, in the photoelectric conversion layer with an intermediate energy band, the introduced intermediate energy band E _i is located between the top E _v of the valence band and the bottom E _c of the conduction band of the parent material.

The second aspect of the present invention provides a photoelectric conversion thin film material for an intermediate energy band solar cell, the photoelectric conversion thin film material comprising:

A photoelectric conversion layer with an intermediate energy band; the matrix material of the photoelectric conversion layer with an intermediate energy band is TiO ₂ , ZnO, Si or a III-V semiconductor material, preferably TiO ₂ ;

The matrix material of the photoelectric conversion layer with an intermediate energy band contains 1 to 5 atomic % of impurity atoms or impurity atom pairs, and the percentage is calculated by the molar ratio of the matrix material;

The intermediate energy band is formed by the impurity atoms or pairs of impurity atoms on the parent material of the photoelectric conversion layer through asymmetric or non-compensatory n-p co-doping.

In a preferred example, the impurity atoms are unequal or non-compensatory n-p co-doped impurity atoms.

In a preferred example, the impurity atom pair is a combination of unequal or non-compensatory n-type and p-type atom pairs;

Preferably, the impurity atom pair is a combination of unequal n-type and p-type atom pairs,

In a preferred example, the n-type atoms doped into the host material donate electrons and the p-type atoms donate holes, but the number of electrons and holes donated by the two are not equal.

In a more preferred example, for the preferred parent material TiO ₂ , the combination of unequal np (that is, n-type and p-type) atomic pairs can be selected from Cr-N, Mo-N, WN, Mo-P, WP or a combination thereof.

In a preferred example, in the photoelectric conversion layer with an intermediate energy band, the introduced intermediate energy band E _i is located between the top E _v of the valence band and the bottom E _c of the conduction band of the parent material.

In a preferred example, the metal of the nano-metal structure layer is Ag, Al, Cu or a combination thereof; the nano-structure used in the nano-metal structure layer is a nanosphere or a nanoshell.

Specifically, the size of the nanostructure is 1-100 nm.

The third aspect of the present invention provides a method for preparing the photoelectric conversion thin film material, comprising the following steps:

i), providing a host material suitable for forming a photoelectric conversion layer with an intermediate energy band; the host material is TiO ₂ , ZnO, Si or III-V group semiconductor material, preferably TiO ₂ ;

ii) The intermediate energy band is constructed by impurity atoms or impurity atom pairs accounting for 1-5 atomic % of the parent material on the parent material through asymmetric or non-compensatory n-p co-doping.

In a preferred example, the unequal or non-compensatory n-p co-doping method may use, but is not limited to, methods such as vapor deposition or liquid phase growth to achieve the doping of n-p impurity atoms.

The fourth aspect of the present invention provides an application of the photoelectric conversion thin film material in improving photoelectric conversion efficiency.

In a specific embodiment, the intermediate energy band E _i is realized on the _TiO2 material through an unequal np co-doping method, and the intermediate energy band E _i introduced should be located at the top of the valence band E _v of the intrinsic material of the film and the conduction Between the bottom E _c ; the average thickness of the intermediate film is about 1 micron.

Description of drawings

Figure 1 is a schematic diagram of a TiO ₂ intermediate zone solar cell.

Detailed ways

After extensive and in-depth research, the inventor expanded theories and concepts, and combined with the existing preparation process, obtained an intermediate energy band thin film material solar cell that can achieve high conversion efficiency. Through the purposefully introduced intermediate energy band, The solar cell can effectively absorb a large amount of photons whose energy is lower than its band gap, thereby achieving higher photoelectric conversion efficiency. The present invention has been accomplished on this basis.

Technical conception of the present invention is as follows:

The invention discloses a wide-spectrum, high-efficiency solar cell, which at least includes a photoelectric conversion layer with an intermediate energy band. The photoelectric conversion layer with the intermediate energy band is made of suitable and cheap _TiO2 material through the non-equal np co-doping method to realize the structure of the intermediate energy band; the same method can also be implemented in materials such as ZnO, Si and III-V groups as The parent structure intermediate energy band.

Various aspects of the invention are described in detail below. Unless otherwise specified, various raw materials of the present invention can be obtained commercially; or prepared according to conventional methods in the art. Unless otherwise defined or stated, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to those described can be applied to the method of the present invention.

The terminology can refer to the following references: [1] A.Luque and A.Marti, Phys.Rev.Lett.78, 5014 (1997). [2] A.Luque and A.Marti, Adv.Mater.( Advanced Materials) 22, 160(2010).

The "complementary thin film" in the present invention means that if the photoelectric conversion layer is N-type, the corresponding complementary thin film should be P-type thin film; otherwise, it is P-type thin film. Specifically, the complementary thin film is used to enhance the efficiency of photogenerated electron-hole separation, so it corresponds to the intermediate energy band thin film material: if the intermediate energy band thin film material is electronically conductive, the thin film is selected as a P-type thin film; If the intermediate band thin film material is hole-type conductive, the thin film is an N-type thin film.

Photoelectric conversion thin film material and preparation method thereof

The invention provides a photoelectric conversion thin film material for an intermediate energy band solar cell, and the photoelectric conversion thin film material includes:

A photoelectric conversion layer with an intermediate energy band; the matrix material of the photoelectric conversion layer with an intermediate energy band is TiO ₂ , ZnO, Si or a III-V semiconductor material, preferably TiO ₂ ;

The matrix material of the photoelectric conversion layer with an intermediate energy band contains 1 to 5 atomic % of impurity atoms or impurity atom pairs, and the percentage is calculated by the molar ratio of the matrix material;

The intermediate energy band is formed by the impurity atoms or pairs of impurity atoms on the parent material of the photoelectric conversion layer through asymmetric or non-compensatory n-p co-doping.

The photoelectric conversion thin film material is a photoelectric conversion layer with an intermediate energy band, wherein the parent material of the photoelectric conversion layer with an intermediate energy band is preferably TiO ₂ material, and for parent materials such as ZnO, Si or III-V semiconductors The same applies.

In a specific embodiment, the unequal np co-doping of the intermediate energy band E _i is realized on the _TiO2 material, and the introduced intermediate energy band E _i should be located at the top E _v of the valence band and the bottom of the conduction band of the intrinsic material of the film between _Ec .

In a specific embodiment, the doped impurity atom concentration is between 1-5% atomic ratio.

In a specific embodiment, the average thickness of the intermediate zone film is about 1-10 microns.

In a specific embodiment, the unequal np co-doping of the intermediate energy band E _i is realized on the _TiO2 material, and the introduced intermediate energy band E _i should be located at the top E _v of the valence band and the bottom of the conduction band of the intrinsic material of the film between E _c ; the doped impurity atomic concentration is between 1-5% atomic ratio; the average thickness of the intermediate zone film is about 1-10 microns.

Photoelectric conversion layer with intermediate energy band

In a preferred example, the photoelectric conversion layer with an intermediate energy band is made of a suitable, cheap material TiO ₂ An asymmetric np co-doping method realizes the structure of an intermediate energy band; this construction method is also applicable to other parent materials such as ZnO, Si and III-V semiconductors, etc.

In a preferred example, the TiO ₂ material contains 1-5% by weight of impurity atoms, and the percentage is based on the molar ratio of the semiconductor material.

In a preferred example, the impurity atoms are unequal n-p co-doped impurity atoms.

In a preferred example, the impurity atoms are one of unequal n-p co-doped elements Cr-N, Mo-N, W-N, Mo-P, W-P and the like. .

In a preferred example, in the photoelectric conversion layer with an intermediate energy band, the introduced intermediate energy band E _i is located between the top E _v of the valence band and the bottom E _c of the conduction band of the parent material.

The inventors found that the intermediate energy band material can absorb low-energy photons, extend the absorption of the intrinsic material to the wavelength range of the solar spectrum, and improve the photoelectric conversion efficiency.

Preparation

The present invention also provides the preparation method of described photoelectric conversion film material, it comprises the following steps:

i), providing a host material suitable for forming a photoelectric conversion layer with an intermediate energy band; the host material is TiO ₂ , ZnO, Si or III-V group semiconductor material, preferably TiO ₂ ;

ii) The intermediate energy band is constructed by impurity atoms or impurity atom pairs accounting for 1-5 atomic % of the parent material on the parent material through asymmetric or non-compensatory n-p co-doping.

In a preferred example, the unequal or non-compensatory n-p co-doping method may use, but is not limited to, methods such as vapor deposition or liquid phase growth to achieve the doping of n-p impurity atoms.

Intermediate energy band solar cell and its preparation method

review

An intermediate energy band intermediate band solar cell of the present invention, said battery comprising:

Substrate;

a back electrode disposed on the substrate;

a complementary thin film on the back electrode;

The photoelectric conversion film material provided on the complementary film; the photoelectric conversion film material is a photoelectric conversion layer with an intermediate energy band; wherein the matrix material of the photoelectric conversion layer with an intermediate energy band is preferentially made of cheap TiO ₂ materials; and

metal electrodes.

The solar cell has an intermediate energy band structure capable of achieving high conversion efficiency, and at the same time, the concentration and combination of co-doped elements can be optimized and the position and width of the intermediate energy band can be regulated. Therefore, the solar cell described above can realize high-efficiency energy conversion.

More specifically, the schematic structure of the solar cell of the present invention is shown in Figure 1, the back electrode can be selected from low work function metals such as Al, and can be processed into a grid-like structure; the N-type thin film material 3 is introduced, and the P-type intermediate film The material forms a P-N junction, and its built-in electric field is conducive to the separation of photogenerated electron-hole pairs; the metal electrode 5 can choose Cu and other high work function metals to achieve low-resistance contact or ohmic contact.

Substrate

The substrate of the present invention is not particularly limited as long as it does not limit the purpose of the present invention. . For example, various plastics, glass, or stainless steel can be used, but not limited thereto, and references listed in the present invention can also be referred to.

Preferably, glass is used.

back electrode

The back electrode of the present invention is not particularly limited, as long as it does not limit the purpose of the present invention. For example, various metals with good electrical conductivity and chemical stability such as Cu and Al can be used, but not limited thereto. You can also refer to the content of the references listed in the present invention.

Preferably, Cu is used.

complementary thin film

The present invention adopts complementary thin film to enhance the efficiency of separation of photogenerated electrons and holes, so it corresponds to the intermediate energy band thin film material: if the intermediate energy band thin film material is electronically conductive, the thin film is selected as a P-type thin film; If the energy-band film material is hole-type conduction, the film is an N-type film. Others are not specifically limited, as long as they do not limit the purpose of the invention. For example, intrinsic oxide materials such as TiO ₂ and ZnO can be used but not limited thereto. You can also refer to the content of the references listed in the present invention.

Preferably, intrinsic TiO ₂ is used.

metal electrode

The metal electrode of the present invention is not particularly limited as long as it does not limit the purpose of the present invention. For example, Al and Cu can be used, but not limited thereto. You can also refer to the content of the references listed in the present invention.

Preferably, Al is used.

The present invention also provides the preparation method of described solar cell, described method comprises the following steps:

a) Deposit and prepare an Al back electrode with a certain thickness such as about 1 micron on a selected substrate such as glass

b), depositing and preparing a TiO2 film with a certain thickness such as 1.0-5.0 microns on the back electrode;

c), followed by the addition of co-doped impurity pairs on the _TiO2 film by vapor-phase deposition to achieve a stable, high-quality intermediate energy band configuration.

Advantages and positive effects:

Since the photoelectric conversion film material of the solar cell has an intermediate energy band, multiple absorption channels of different energies are provided for the absorption of sunlight [1, 2]: electrons can absorb a high-energy photon and directly jump from the valence band to the conduction band; It is also possible to make electrons go through two photon processes, that is, first absorb a low-energy photon to jump to the intermediate energy band, and then absorb the second low-energy photon to jump to the conduction band. For example, compared to the ideal efficiency of 9.6% for a single-gap TiO ₂ battery, the theoretical efficiency of a TiO ₂ battery with an intermediate energy band can be optimized to 56.0%. Efficiency here refers to the ratio of the output power of the battery to the incident light energy of one standard solar irradiation per second.

Other aspects of the invention will be apparent to those skilled in the art from the disclosure herein.

Below in conjunction with specific embodiment, further illustrate the present invention. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods without specific conditions indicated in the following examples are usually carried out according to conventional conditions, or according to the conditions suggested by the manufacturer. Unless otherwise indicated, all parts are mole parts, all percentages are atomic percent, and stated polymer molecular weights are number average molecular weights.

Unless otherwise defined or stated, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to those described can be applied to the method of the present invention.

Example

Implementation details of the invention will now be described, including exemplary aspects and implementation examples of the invention. Referring to the illustration in FIG. 1 , the associated numerals and the following description will illustrate the main features of the exemplary embodiments. Additionally, there is no intention in the legends to depict every feature of actual embodiments or to depict relative dimensions of elements, and the drawings are not drawn to scale.

The basic concept of manufacturing the intermediate solar cell with titanium dioxide as the matrix material is to sequentially grow each layer of structural materials shown in FIG. 1 on the substrate 1 (glass or plastic, etc.). That is, the back electrode 2 is epitaxially grown or vapor-deposited on the substrate, and then a complementary thin film, that is, an N-type thin film material (such as TiO ₂ or ZnO), and a P-type intermediate zone thin film 4 are fabricated on it by epitaxial growth.

Appropriate reaction temperature and time are preferred, and appropriate chemical components and dopants are used to control the thickness, lattice constant and electrical properties of the N-type thin film structure layer and the P-type intermediate zone thin film structure. The use of vapor deposition methods (such as metal organic vapor phase epitaxy (OMVPE), metal organic vapor phase deposition (MOCVD), molecular beam epitaxy (MBE), etc.) can enable the formation of monolithic thin film structures with desired thickness, element composition, Doping concentration and conductivity characteristics (that is, N-type or P-type) are grown.

The method of sputtering evaporation can tightly bond low work function metals such as Al and high work function metals such as Cu with the oxide structure layer to form a reliable low resistance or ohmic contact.

In an embodiment, the substrate 1 can be selected from silicon, glass, quartz, plastic, stainless steel and the like. In order to obtain better light transmission properties and lower manufacturing costs, glass or stainless steel can be used as the main choice. The back electrode 2 can choose main process methods such as evaporation method, sputtering method, electroplating method, printing method, etc., and a metal electrode with a thickness between 50 and 300 nm is epitaxially formed on the substrate 1 . Through main process methods such as masking and electron beam exposure, the back electrode 2 can be processed and structured with a nanometer microstructure. The N-type thin film is epitaxially grown on the back electrode 2 by methods such as molecular beam epitaxy and vapor deposition, and the thickness is between 500-1000nm. For oxide materials, it is noted that TiO ₂ and the like have intrinsic N-type electrical characteristics, which will reduce the complexity of process manufacturing. Then, further epitaxially grow a doped P-type film with intermediate energy band characteristics on the N-type film, with a thickness between 1000-5000nm; doping elements are selected according to the system, and for TiO ₂ materials, Cr and N can be selected. , through the introduction of Cr organometallic compounds and nitrogen-rich molecules such as NH ₃ , co-doped, intermediate energy band, P-type TiO ₂ film layers can be realized during the epitaxial growth process, and the concentration of co-doped atoms is controlled at 1 -5%; and can further achieve stable and uniform distribution of co-doped elements by annealing and other methods, and improve its electrical stability. Finally, select a suitable metal such as Ag or Cu, and realize the electrode 5 by evaporation or sputtering.

performance example

The battery of the present invention is assembled with a photoelectric conversion layer with an intermediate energy band, which enables the battery to absorb more low-energy photons and improve the efficiency of photoelectric conversion compared with existing batteries (mostly single-band batteries). Theoretical calculations show that the photoelectric conversion efficiency can be increased from 9.6% to 56% after introducing the intermediate energy band structure into the _TiO2 matrix material. Therefore, in actual batteries, it is possible to break through the bottleneck of single-band batteries and achieve a higher conversion efficiency of 10% or more. Efficiency here refers to the ratio of the output power of the battery to the incident light energy of one standard solar irradiation per second.

The most important spirit of the present invention is to simultaneously utilize the intermediate energy band of the material and the unequal n-p co-doping method. The intermediate energy band can effectively increase the contribution of low-energy photons to the photocurrent, thereby realizing high-efficiency solar cells; the non-equal n-p co-doping method can effectively regulate the energy band structure of the material and improve the thermodynamic solubility of the parent material for impurity atoms. Achieving efficient construction of intermediate energy bands. Therefore, the present invention can have other multiple embodiments, and those skilled in the art can make various corresponding changes and deformations according to the present invention without departing from the spirit and essence of the present invention. Changes and deformations should all belong to the protection scope of the appended claims of the present invention.

All documents mentioned in this application are incorporated by reference in this application as if each were individually incorporated by reference. In addition, it should be understood that after reading the above content of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Claims (10)

1. An intermediate energy band solar cell, characterized in that the cell comprises: Substrate; a back electrode disposed on the substrate; a complementary thin film on the back electrode; A photoelectric conversion thin film material provided on the complementary thin film; wherein, the photoelectric conversion thin film material is a photoelectric conversion layer with an intermediate energy band; the matrix material of the photoelectric conversion layer with an intermediate energy band is TiO ₂ , ZnO , Si or III-V semiconductor materials; as well as metal electrodes. 2 . The solar cell according to claim 1 , wherein the matrix material of the photoelectric conversion layer with an intermediate energy band is TiO ₂ . 3. The solar cell according to claim 1, characterized in that, the matrix material of the photoelectric conversion layer having an intermediate energy band contains 1 to 5 atomic % of impurity atoms or impurity atom pairs, and the percentage is expressed as the percentage of the matrix material. Molar ratio meter. 4. The solar cell according to claim 3, wherein the impurity atoms are asymmetric or non-compensatory n-p co-doped impurity atoms. 5 . The solar cell according to claim 3 , wherein the impurity atom pairs are unequal or non-compensatory n-p atom pair combinations. 6. The solar cell according to claim 5, characterized in that, when the parent material adopts TiO ₂ , the combinations of the unequal np atom pairs are selected from Cr-N, Mo-N, WN, Mo-P, or WP. 7. The solar cell according to claim 1, characterized in that, in the photoelectric conversion layer with an intermediate energy band, the introduced intermediate energy band _Ei is located at the top E of the valence band _and the bottom E of the conduction band of its parent material. between _c . 8. A photoelectric conversion thin film material for intermediate energy band solar cells, characterized in that, the photoelectric conversion thin film material comprises: A photoelectric conversion layer with an intermediate energy band; the matrix material of the photoelectric conversion layer with an intermediate energy band is TiO ₂ , ZnO, Si or a III-V semiconductor material, preferably TiO ₂ ; The matrix material of the photoelectric conversion layer with an intermediate energy band contains 1 to 5 atomic % of impurity atoms or impurity atom pairs, and the percentage is calculated by the molar ratio of the matrix material; The intermediate energy band is formed by the impurity atoms or pairs of impurity atoms on the parent material of the photoelectric conversion layer through asymmetric or non-compensatory n-p co-doping. 9. A preparation method of photoelectric conversion thin film material as claimed in claim 8, is characterized in that, comprises the steps: i), providing a host material suitable for forming a photoelectric conversion layer with an intermediate energy band; the host material is TiO ₂ , ZnO, Si or III-V group semiconductor material, preferably TiO ₂ ; ii) The intermediate energy band is constructed by impurity atoms or impurity atom pairs accounting for 1-5 atomic % of the parent material on the parent material through asymmetric or non-compensatory n-p co-doping. 10. An application of the photoelectric conversion thin film material as claimed in claim 8 in improving photoelectric conversion efficiency.

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