TWI442588B - Solar cell and preparation method thereof - Google Patents

Description

Solar cell and preparation method thereof

The invention relates to a solar cell and a preparation method thereof.

Solar energy is one of the cleanest energy sources in today, and it is inexhaustible. Solar energy utilization includes light energy-thermal energy conversion, light energy-electric energy conversion, and light energy-chemical energy conversion. A typical example of solar cell-based light energy-electric energy conversion is made using the photovoltaic principle of semiconductor materials. According to different types of semiconductor photoelectric conversion materials, solar cells can be classified into germanium-based solar cells (see production of solar cells and polycrystalline germanium, Journal of Materials and Metallurgy, Zhang Mingjie et al., vo16, p33-38 (2007)), gallium arsenide solar cells. , organic thin film solar cells, etc.

At present, solar cells are mainly based on germanium-based solar cells. Please refer to FIG. 1. FIG. 1 is a prior art solar cell 400. The solar cell 400 includes a back electrode 40, a germanium substrate 42, a doped germanium layer 44, and an upper electrode 46. The cymbal substrate 42 is made of polycrystalline germanium or single crystal germanium, and has a first surface 41 and a second surface 43 disposed opposite the first surface 41. The second surface 43 is a planar structure. The back electrode 40 is disposed on the first surface 41 of the cymbal substrate 42 and is in ohmic contact with the first surface 41 of the cymbal substrate 42. The doped germanium layer 44 is formed on the second surface 43 of the enamel substrate 42 as a material for photoelectric conversion. The surface of the doped germanium layer 44 is a flat planar structure. The upper electrode 46 is disposed on a surface of the doped germanium layer 44. Place The ruthenium substrate 42 and the doped yttrium layer 44 in the solar cell 400 form a PN junction which generates a plurality of electron-hole pairs (excitons) under the excitation of sunlight, the electron-hole pairs The electrostatic potential energy is separated and moved to the back electrode 40 and the upper electrode 46, respectively. If a load is applied across the back electrode 40 and the upper electrode 46 of the solar cell 400, a current flows through the load in the external circuit.

However, in the prior art, since the surface of the doped germanium layer 44 formed on the second surface 43 of the enamel substrate 42 has a flat planar structure and a small surface area thereof, the solar cell 400 is taken. The light area is small. In addition, when the sun light is incident from the outside to the surface of the doped germanium layer 44, since the surface of the doped germanium layer 44 has a planar structure, a part of the light irradiated to the doped germanium layer 44 is absorbed, and a part of the light is reflected. However, the reflected light cannot be reused, so the solar cell 400 has a low utilization rate of light.

In view of this, it is necessary to provide a solar cell having a large light extraction area and a method of preparing the same.

A solar cell comprising: a cymbal substrate having a first surface and a second surface disposed opposite the first surface, the second surface of the cymbal substrate being provided with a plurality of a three-dimensional nanostructure, the three-dimensional nanostructure is a stepped structure; a back electrode, the back electrode is disposed on the first surface of the enamel substrate and is in ohmic contact with the first surface; a layer, the doped germanium layer is formed on a surface of the three-dimensional nanostructure and a second surface of the germanium substrate between adjacent three-dimensional nanostructures; and an upper electrode, the upper electrode is disposed on the Doping at least a portion of the surface of the ruthenium layer.

A solar cell comprising a back electrode disposed in order from bottom to top, a germanium substrate, a doped germanium layer, and an upper electrode, wherein the surface of the germanium substrate adjacent to the upper electrode is provided with a plurality of three dimensions In the nanostructure, the three-dimensional nanostructure is a stepped structure, and the doped germanium layer is disposed on a surface of the three-dimensional nanostructure and a surface of the germanium substrate between adjacent three-dimensional nanostructures.

A method of fabricating a solar cell, comprising: providing a cymbal substrate having a first surface and a second surface disposed opposite the first surface, the second surface of the cymbal substrate The surface is provided with a plurality of stepped three-dimensional nanostructures; a doped germanium layer is formed on the surface of the germanium substrate between the three-dimensional nanostructure surface and the adjacent three-dimensional nanostructure; an upper electrode is provided, and The upper electrode is disposed on at least a portion of a surface of the doped germanium layer; and a back electrode is disposed, the back electrode is disposed on the first surface of the germanium substrate, and the back electrode and the germanium are The first surface of the sheet substrate is in ohmic contact.

Compared with the prior art, the solar cell can increase the light extraction area of the solar cell by providing a plurality of stepped three-dimensional nano structures on the second surface of the enamel substrate. In addition, when light is irradiated to the side of the three-dimensional nanostructure, a part of the irradiated light is absorbed and partially reflected, and most of the reflected light is once again incident on the adjacent three-dimensional nanostructure, and the phase is The adjacent three-dimensional nanostructure absorbs and reflects, so that the irradiated light is reflected and absorbed plural times in the three-dimensional nanostructure, thereby further improving the utilization of light by the solar cell. The method for preparing the solar cell has the advantages of simple process and low cost.

100;200;300‧‧‧ solar cells

10;30‧‧‧ Back electrode

11;21;31‧‧‧ first surface

12;32‧‧‧矽 substrate

13;23;33‧‧‧second surface

14;34‧‧‧Doped layer

15;25;35‧‧‧Three-dimensional nanostructure

152; 252‧‧‧ first cylinder

154; 254‧‧‧ second cylinder

16; 36‧‧‧ upper electrode

18‧‧‧metal layer

22‧‧‧矽 substrate

24‧‧‧ mask layer

26‧‧‧Reactive etching gas

352‧‧‧First cylindrical space

354‧‧‧Second cylindrical space

1 is a schematic structural view of a solar cell in the prior art.

2 is a schematic structural view of a solar cell according to a first embodiment of the present invention.

3 is a schematic structural view of a ruthenium substrate in a solar cell according to a first embodiment of the present invention.

4 is a scanning electron micrograph of a ruthenium substrate in a solar cell according to a first embodiment of the present invention.

FIG. 5 is a flow chart of a method for fabricating a solar cell according to a first embodiment of the present invention.

6 is a process flow diagram of a method for preparing a plurality of three-dimensional nanostructures on a second surface of a tantalum substrate in a method for fabricating a solar cell according to a first embodiment of the present invention.

7 is a scanning electron micrograph of a single-layer nanosphere in which a hexagonal close-packed arrangement is formed on a second surface of a tantalum substrate in a method of fabricating a solar cell according to a first embodiment of the present invention.

FIG. 8 is a scanning electron micrograph of a single-layer nanosphere formed on a second surface of a tantalum substrate in a method for preparing a solar cell according to a first embodiment of the present invention.

FIG. 9 is a schematic structural diagram of a solar cell according to a second embodiment of the present invention.

FIG. 10 is a schematic structural diagram of a solar cell according to a third embodiment of the present invention.

FIG. 11 is a structural diagram showing a ruthenium substrate in a solar cell according to a third embodiment of the present invention; intention.

The solar cell provided by the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

Referring to FIG. 2, a first embodiment of the present invention provides a solar cell 100 comprising, in order from bottom to top, a back electrode 10, a germanium substrate 12, a doped germanium layer 14, and an upper electrode 16. Sunlight is incident from the side of the upper electrode 16. The cymbal substrate 12 has a first surface 11 and a second surface 13 disposed opposite the first surface 11. The second surface 13 is adjacent to the upper electrode 16 of the cymbal substrate 12. The surface, that is, the surface on the side close to the incident direction of the sunlight. The second surface 13 of the cymbal substrate is provided with a plurality of three-dimensional nanostructures 15 which are stepped structures; the back electrode 10 is disposed on the first surface of the cymbal substrate 12 And ohmic contact with the first surface 11; the doped germanium layer 14 is formed on the surface of the three-dimensional nanostructure 15 and the second surface of the cymbal substrate 12 between the adjacent three-dimensional nanostructures 15 The upper electrode 16 is disposed on at least a portion of the surface of the doped germanium layer 14.

The material of the back electrode 10 may be a metal such as aluminum, magnesium or silver. The back electrode 10 has a thickness of 10 micrometers to 300 micrometers. In this embodiment, the back electrode 10 is an aluminum foil having a thickness of about 200 microns.

Referring to FIG. 3, the cymbal substrate 12 is a P-type cymbal substrate. The material of the P-type cymbal substrate may be a single crystal germanium, a polysilicon or other P-type semiconductor material. In this embodiment, the cymbal substrate 12 is a P-type single crystal cymbal. The ruthenium substrate 12 has a thickness of from 200 micrometers to 300 micrometers. The second surface 13 of the cymbal substrate 12 is provided with a plurality of three-dimensional nanostructures 15. The plurality of three-dimensional nanostructures 15 are on the cymbal substrate 12 The second surfaces 13 are arranged in an array. The arrangement in the form of an array means that the plurality of three-dimensional nanostructures 15 can be arranged in a simple cubic arrangement, a concentric annular arrangement or a hexagonal dense arrangement. Moreover, the plurality of three-dimensional nanostructures 15 arranged in an array form a single pattern or a plurality of patterns. The single pattern may be a triangle, a parallelogram, a diamond, a square, a rectangle, or a circle. The distance between the adjacent two three-dimensional nanostructures 15 is equal. The distance between the adjacent two three-dimensional nanostructures 15 is from 10 nm to 1000 nm. The form in which the plurality of three-dimensional nanostructures 15 are arranged on the second surface 13 of the enamel substrate 12 and the distance between the adjacent two three-dimensional nanostructures 15 can be prepared according to actual needs. In this embodiment, the plurality of three-dimensional nanostructures 15 are arranged in a hexagonal densely packed pattern to form a single square pattern, and the distance between two adjacent three-dimensional nanostructures 15 is about 30 nm.

The three-dimensional nanostructure 15 is a stepped convex structure. The stepped raised structure is an entity of stepped protrusions that extend outwardly from the second surface 13 of the cymbal substrate 12. The stepped convex structure is a plurality of layer structures, such as a plurality of layers of triangular prisms, a plurality of layers of quadrangular prisms, a plurality of layers of hexagonal prisms, a plurality of layers of cylinders or a plurality of layers of circular tables. In this embodiment, the stepped convex structure is a plurality of layered cylindrical structures. The maximum size of the stepped protrusion structure is 1000 nm or less, that is, its length, width and height are less than or equal to 1000 nm. Preferably, the stepped protrusion structure has a length, a width and a height ranging from 10 nm to 500 nm.

Referring to FIG. 4 together, in the embodiment, the three-dimensional nanostructure 15 is a double-layered cylindrical structure with a stepped protrusion. Specifically, the three-dimensional nanostructure 15 includes a first cylinder 152 and a second cylinder 154 disposed on an upper surface of the first cylinder 152. Place The first cylinder 152 is disposed on the second surface 13 of the cymbal substrate 12, and the side of the first cylinder 152 is perpendicular to the second surface 13 of the cymbal substrate 12. The side of the second cylinder 154 is perpendicular to the upper surface of the first cylinder 152. Preferably, the first cylinder 152 is coaxial with the second cylinder 154, and the first cylinder 152 and the second cylinder 154 are a unitary structure, that is, the second cylinder 154 is a cylinder extending from the upper surface of the first cylinder 152. Structure. The diameter of the first cylinder 152 is greater than the diameter of the second cylinder 154. The first cylinder 152 has a diameter of 30 nm to 1000 nm and a height of 50 nm to 1000 nm. Preferably, the first cylinder 152 has a diameter of 50 nm to 200 nm and a height of 100 nm to 500 nm. The second cylinder 154 has a diameter of 10 nm to 500 nm and a height of 20 nm to 500 nm. Preferably, the second cylinder 154 has a diameter of 20 nm to 200 nm and a height of 100 nm to 300 nm. The dimensions of the first cylinder 152 and the second cylinder 154 can be prepared according to actual needs. In this embodiment, the first cylinder 152 and the second cylinder 154 are coaxially disposed, and the first cylinder 152 and the second cylinder 154 are integrally formed with the cymbal substrate 12. The first cylinder 152 has a diameter of 380 nm and a height of 105 nm. The second cylinder 154 has a diameter of 280 nm and a height of 55 nm.

The doped germanium layer 14 is formed on the surface of the three-dimensional nanostructure 15 and the second surface 13 of the germanium substrate 12 between adjacent three-dimensional nanostructures 15, and the material of the doped germanium layer 14 is N-type doped layer. The doped germanium layer 14 can be implanted with an excess of, for example, phosphorus by a second surface 13 of the enamel substrate 12 and a plurality of three-dimensional nanostructures 15 disposed on the second surface 13 of the slab substrate 12. Or N-type doping materials such as arsenic are prepared. The N-type doped germanium layer 14 has a thickness of 10 nm to 1 μm. The doped germanium layer 14 forms a P-N junction structure with the germanium substrate 12 to implement the solar cell 100. Conversion of light energy to electrical energy. It can be understood that providing a plurality of three-dimensional nanostructures 15 on the second surface 13 of the cymbal substrate 12 allows the second surface 13 of the cymbal substrate 12 to have a larger PN junction interface area. The solar cell has a larger light extraction area; in addition, the plurality of three-dimensional nanostructures 15 have the characteristics of a photonic crystal, so that the residence time of the photons in the three-dimensional nanostructure 15 and the three-dimensional nanometer can be increased. The frequency range of the absorption light of the structure 15 increases the light absorption efficiency of the solar cell 100, thereby improving the photoelectric conversion efficiency of the solar cell 100.

In addition, when light is incident on the sides of the first cylinder 152 and the second cylinder 154, a part of the irradiated light is absorbed and partially reflected, and most of the reflected light is once again incident on the adjacent three-dimensional nanometer. The structure 15 is absorbed and reflected by the adjacent three-dimensional nanostructure 15 , so that the irradiated light is reflected and absorbed in the three-dimensional nanostructure 15 in multiple times, that is, the first time the light is irradiated When the first cylinder 152 and the side surface of the second cylinder 154 are used, most of the reflected light is reused, so that the utilization of light by the solar cell 100 can be further improved.

The upper electrode 16 may be in partial or full contact with the doped germanium layer 14. It can be understood that the upper electrode 16 can be partially suspended by the plurality of three-dimensional nanostructures 15 and partially contacted with the doped germanium layer 14; the upper electrode 16 can also be coated with the doping. The surface of the germanium layer 14 is in complete contact with the doped germanium layer 14. The upper electrode 16 may be selected from an indium tin oxide structure and a carbon nanotube structure having good light transmission properties and electrical conductivity, so that the solar cell 100 has high photoelectric conversion efficiency, good durability, and Uniform resistance, thereby improving the performance of the solar cell 100.

The indium tin oxide structure may be an indium tin oxide layer, and the indium tin oxide layer may be uniform The surface of the doped germanium layer 14 is coated and completely in contact with the doped germanium layer 14. The carbon nanotube structure is a self-supporting structure composed of a plurality of carbon nanotubes, and the carbon nanotube structure may be a carbon nanotube membrane or a nanocarbon pipeline, and the carbon nanotube membrane or nai The carbon carbon pipeline may be partially suspended by the plurality of three-dimensional nanostructures 15 and partially contacted with the doped germanium layer 14. The self-supporting structure means that the carbon nanotube structure can be self-supported without substrate support. In this embodiment, the upper electrode 16 is a carbon nanotube film, and the carbon nanotube film is a self-supporting structure composed of a plurality of carbon nanotubes. The carbon nanotube film is partially suspended by the plurality of three-dimensional nanostructures 15 and is in partial contact with the doped germanium layer 14 for collecting light energy through the PN junction. The current produced by the conversion of electrical energy.

It can be understood that the solar cell 100 can further include an intrinsic tunnel layer (not shown) disposed between the enamel substrate 12 and the doped yttrium layer 14, the intrinsic tunnel The material of the layer is cerium oxide or cerium nitride. The intrinsic tunnel layer has a thickness of 1 angstrom to 30 angstroms. The arrangement of the intrinsic tunnel layer can reduce the recombination speed of the electron-hole pair at the contact surface of the enamel substrate 12 and the doped yttrium layer 14, thereby further improving the photoelectric conversion efficiency of the solar cell 100.

A contact surface of the ruthenium substrate 12 and the doped ruthenium layer 14 in the solar cell 100 is formed with a P-N junction. The excess electrons in the doped germanium layer 14 on the contact surface tend to the P-type germanium substrate in the wafer substrate 12 and form an internal electric field directed by the doped germanium layer 14 toward the germanium substrate 12. Sunlight is incident from the side of the upper electrode 16 of the solar cell 100, and when the PN junction generates a plurality of electron-hole pairs under the excitation of sunlight, the plurality of electron-hole pairs act on the internal electric field Subsequent separation, electrons in the N-type dopant material move toward the upper electrode 16, and holes in the P-type germanium substrate move toward the back electrode 10. And then collected by the back electrode 10 and the upper electrode 16, respectively, to form a current.

Referring to FIG. 5, the present invention further provides a method for fabricating the solar cell 100, comprising the steps of: S10, providing a cymbal substrate having a first surface and opposite to the first surface a second surface disposed, the second surface of the cymbal substrate is provided with a plurality of stepped three-dimensional nanostructures; S11, between the surface of the three-dimensional nanostructure and the adjacent three-dimensional nanostructure a second surface of the substrate is formed with a doped germanium layer; S12, an upper electrode is provided, and the upper electrode is disposed on at least a portion of the surface of the doped germanium layer; S13, and a back electrode is provided The back electrode is disposed on the first surface of the cymbal substrate such that the back electrode is in ohmic contact with the first surface of the cymbal substrate.

Referring to FIG. 6 , the step S10 further includes the following steps: Step S101 , providing a substrate 22 including a first surface 21 and a second surface 23 disposed opposite the first surface 21 . The ruthenium substrate 22 is a P-type ruthenium, and the material of the P-type ruthenium may be a single crystal germanium, a polycrystalline germanium or other P-type semiconductor material. In this embodiment, the germanium substrate 22 is a P-type single crystal germanium. The germanium substrate 22 has a thickness of 200 micrometers to 300 micrometers. The size, thickness, and shape of the crucible substrate 22 are not limited and may be selected according to actual needs.

Further, the second surface 23 of the ruthenium substrate 22 may be subjected to a hydrophilic treatment.

First, the second surface 23 of the crucible substrate 22 is cleaned and cleaned using a clean room standard process. Then, in a solution having a temperature of 30 ° C to 100 ° C and a volume ratio of NH ₃ ‧H ₂ O:H ₂ O ₂ :H ₂ O=x:y:z, the bath is heated for 30 minutes to 60 minutes. The second surface 23 of the substrate 22 is subjected to a hydrophilic treatment, followed by rinsing with deionized water twice to three times. Where x is 0.2 to 2, y is 0.2 to 2, and z is 1 to 20. Finally, the second surface 23 of the tantalum substrate 22 is blown dry with nitrogen.

Further, the second surface 23 of the ruthenium substrate 22 may be subjected to a second hydrophilic treatment, which specifically includes the following steps: treating the ruthenium substrate 22 after the hydrophilic treatment at 2 wt% to 5 wt% of sodium lauryl sulfate Soak in solution (SDS) for 2 hours to 24 hours. It will be appreciated that the second surface 23 of the tantalum substrate 22 after soaking in the SDS facilitates the spreading of subsequent nanospheres and forms an ordered array of large area nanospheres.

In step S102, a mask layer 24 is formed on the second surface 23 of the germanium substrate 22.

The method of forming the mask layer 24 on the second surface 23 of the ruthenium substrate 22 is to form a single layer of nanospheres on the second surface 23 of the ruthenium substrate 22. It can be understood that, using a single layer of nanospheres as the mask layer 24, a stepped convex structure can be prepared at a position corresponding to the nanospheres.

Forming a single layer of nanospheres as the mask layer 24 on the second surface 23 of the ruthenium substrate 22 specifically includes the following steps: First, preparing a solution of nanospheres.

In this embodiment, 150 ml of pure water, 3 μl to 5 μl of 0.01 wt% to 10 wt% of nanospheres, and an equivalent weight of 0.1 wt% to 3 wt are sequentially added to a 15 cm diameter watch glass. After the % SDS was formed, the mixture was allowed to stand for 30 to 60 minutes. After the nanospheres are sufficiently dispersed in the mixture, 1 microliter to 3 microliters of 4 wt% SDS is added to adjust the surface tension of the nanospheres, which is favorable for forming a single layer nanosphere array. The diameter of the nanospheres may range from 60 nm to 500 nm. Specifically, the diameter of the nanospheres may be 100 nm, 200 nm, 300 nm or 400 N. Meters, the above diameter deviation is 3 nm ~ 5 nm. Preferred nanospheres have a diameter of 200 nm or 400 nm. The nanospheres may be polymer nanospheres or nanobelt microspheres or the like. The material of the polymer nanospheres may be polystyrene (PS) or polymethyl methacrylate (PMMA). It will be appreciated that the mixture in the watch glass can be scaled as desired.

Next, a single layer of nanosphere solution is formed on the second surface 23 of the ruthenium substrate 22, and the single layer of nanospheres is disposed in an array on the second surface 23 of the ruthenium substrate 22.

A single layer of nanosphere solution is formed on the second surface 23 of the ruthenium substrate 22 by a pulling or spin coating method. The single-layer nano microspheres may be arranged in a hexagonal dense stack, a simple cubic arrangement or a concentric annular arrangement.

The method for forming a single-layer nano microsphere solution on the second surface 23 of the ruthenium substrate 22 by the pulling method comprises the following steps: First, the hydrophilically treated ruthenium substrate 22 is slowly tilted along the surface plate The side walls are slid into the mixture of the watch glass, and the 矽 substrate 22 is inclined at an angle of 9° to 15°. The tantalum substrate 22 is then slowly lifted from the mixture of watch glass. Among them, the above-mentioned sliding down and lifting speed are equivalent, both are 5 mm / hour ~ 10 mm / hour. In the process, the nanospheres in the solution of the nanospheres are self-assembled to form a single layer of nanospheres arranged in a hexagonal close-pack.

In this embodiment, a single layer of nanosphere solution is formed on the second surface 23 of the ruthenium substrate 22 by spin coating, which comprises the following steps: First, the hydrophilically treated ruthenium substrate 22 is at 2 wt% of dodecyl group. The sodium sulfate solution is immersed for 2 hours to 24 hours, and after taking out, 3 μl to 5 μl of polystyrene is coated on the second surface 23 of the ruthenium substrate 22. Second Spin-coat at a speed of 400 rpm to 500 rpm for 5 seconds to 30 seconds. Then, spin coating at a speed of 800 rpm to 1000 rpm for 30 seconds to 2 minutes. Again, the spin coating speed is increased to 1400 rpm to 1500 rpm, and spin coating is applied for 10 seconds to 20 seconds to remove excess microspheres at the edges. Finally, the second surface 23 on which the nanospheres are distributed is dried to form a single layer of nanospheres arranged in a hexagonal close-packed manner on the second surface 23 of the base substrate 22, thereby forming the Mask layer 24. Further, the second surface 23 of the ruthenium substrate 22 may be further baked after the mask layer 24 is formed. The baking temperature is 50 ° C to 100 ° C, and the baking time is 1 minute to 5 minutes.

In this embodiment, the diameter of the nanospheres may be 400 nm. Referring to FIG. 7, the nanospheres in the single-layer nano microspheres are arranged in the lowest energy arrangement, that is, the hexagonal close-packed arrangement. The single-layer nanospheres are densely packed and have the largest duty ratio. Any three adjacent nanospheres in the single-layer nanospheres are in an equilateral triangle.

It can be understood that by controlling the surface tension of the nanosphere solution, the nanospheres in the single-layer nanospheres can be arranged in a simple cubic arrangement as shown in FIG.

In step S103, the second surface 23 of the germanium substrate 22 is etched by the reactive etching gas 26 while etching the mask layer 24, and a plurality of stepped shapes are formed on the second surface 23 of the germanium substrate 22. Three-dimensional nanostructures 25.

The step of etching the second surface 23 of the tantalum substrate 22 with the reactive etching gas 26 is performed in a microwave plasma system. The microwave plasma system is a Reaction-Ion-Etching (RIE) mode. The reactive etching gas 26 is used to etch the second surface 23 of the germanium substrate 22 while being The mask layer 24 is etched. When the mask layer 24 is a single layer of nanospheres, the diameter of the nanospheres is reduced during the etching process, so that a plurality of stepped three-dimensional nanostructures 25 can be formed.

In this embodiment, the second surface 23 of the tantalum substrate 22 on which the single layer of nanospheres are formed is placed in a microwave plasma system, and an inductive power source of the microwave plasma system generates a reactive etching gas 26. The reactive etching gas 26 diffuses from the generation region and drifts to the second surface 23 of the tantalum substrate 22 with a lower ion energy. In one aspect, the reactive etching gas 26 etches the second surface 23 of the tantalum substrate 22 between the single layer of nanospheres to form a first cylinder 252; on the other hand, the reactivity The etching gas 26 simultaneously etches the single layer of nanospheres on the second surface 23 of the ruthenium substrate 22 to form smaller diameter nanospheres, ie, each nanometer in the single layer of nanospheres. The ball is etched into nanospheres having a smaller diameter than the first cylinder 252, such that the reactive etching gas 26 can further etch the first cylinder 252 to form the second cylinder 254. Further, the plurality of stepped three-dimensional nanostructures 25 are formed.

In this embodiment, the working gas of the microwave plasma system includes sulfur hexafluoride (SF ₆ ) and argon (Ar) or sulfur hexafluoride (SF ₆ ) and oxygen (O ₂ ). Among them, the rate of sulphur hexafluoride is 10 standard milliliters per minute ~ 60 standard conditions per minute, the access rate of argon or oxygen is 4 standard milliliters per minute ~ 20 standard conditions per minute. The working gas forms a gas pressure of 2 Pa to 10 Pa. The plasma system has a power of 40 watts to 70 watts. The etching time using the reactive etching gas 26 is from 1 minute to 2.5 minutes. Preferably, the ratio of the power of the microwave plasma system to the gas pressure of the working gas of the microwave plasma system is less than 20:1. It will be appreciated that the spacing between the three-dimensional nanostructures 25 and the height of the first cylinders 252 and the second cylinders 254 in the three-dimensional nanostructures 25 can be controlled by controlling the etching time of the reactive etching gas 26.

Further, other gases such as trifluoromethane (CHF ₃ ), tetrafluoromethane (CF ₄ ) or a mixed gas thereof may be added to the reactive etching gas 26 to adjust the etching rate. The flow rate of the trifluoromethane (CHF ₃ ), tetrafluoromethane (CF ₄ ) or a mixed gas thereof may be 20 standard milliliters per minute to ~40 standard milliliters per minute.

In step S104, the mask layer 24 is removed to obtain the enamel substrate.

Using a non-toxic or low-toxic environmentally friendly solvent such as tetrahydrofuran (THF), acetone, methyl ethyl ketone, cyclohexane, n-hexane, methanol or absolute ethanol as a stripping agent to dissolve the nanospheres, the nanospheres can be removed and retained in the ruthenium. The three-dimensional nanostructure 25 of the second surface 23 in the substrate 22, thereby forming the cymbal substrate 12 in the first embodiment of the present invention, wherein the first surface 21 of the ruthenium substrate 22 is the first embodiment of the present invention a first surface 11 of the cymbal substrate 12; the three-dimensional nanostructure 25 is a three-dimensional nanostructure 15 in the cymbal substrate 12 of the first embodiment of the present invention; The surface between the adjacent three-dimensional nanostructures 25 is the second surface 13 of the cymbal substrate 12 described in the first embodiment of the present invention.

In this example, the polystyrene nanospheres were removed by ultrasonic cleaning in methyl ethyl ketone.

In step S12, a doped germanium layer 14 is formed on the surface of the three-dimensional nanostructure 15 and the second surface 13 of the wafer substrate 12 between the adjacent three-dimensional nanostructures 15.

The doped germanium layer 14 is implanted with an excessive amount of N such as phosphorus or arsenic to the second surface 13 of the wafer substrate 12 between the surface of the three-dimensional nanostructure 15 and the adjacent three-dimensional nanostructure 15 The doped material is prepared. The thickness of the doped germanium layer 14 is 10 nm~1 Micron. The doped germanium layer 14 forms a P-N junction structure with the germanium substrate 12 to effect conversion of light energy to electrical energy in the solar cell 100.

It can be understood that, before the step S12, an eigen tunnel may be further formed on the second surface 13 of the cymbal substrate 12 between the surface of the three-dimensional nanostructure 15 and the adjacent three-dimensional nanostructure 15 The layer, the material of the intrinsic tunnel layer may be ceria or tantalum nitride, and this step is an optional step.

In step S13, an upper electrode 16 is provided, and the upper electrode 16 is disposed on at least part of the surface of the doped germanium layer 14.

It can be understood that the upper electrode 16 is disposed on the surface of the doped germanium layer 14, and the upper electrode 16 can be partially or completely in contact with the doped germanium layer 14. The upper electrode 16 may be partially suspended by the plurality of three-dimensional nanostructures 15 and partially in contact with the doped germanium layer 14; the upper electrode 16 may also be coated on the surface of the doped germanium layer 14. And in complete contact with the doped germanium layer 14. The upper electrode 16 may be selected from an indium tin oxide structure and a carbon nanotube structure having good light transmission properties and electrical conductivity, so that the solar cell 100 has high photoelectric conversion efficiency, good durability, and Uniform resistance, thereby improving the performance of the solar cell 100. In this embodiment, the upper electrode 16 is a carbon nanotube film, and the carbon nanotube film is partially suspended by the three-dimensional nanostructure 15 and partially contacts the doped germanium layer 14 . The carbon nanotube film is used to collect the current generated by the conversion of light energy to electric energy in the PN junction.

Step S14, providing a back electrode 10, the back electrode 10 is disposed on the first surface 11 of the cymbal substrate 12, and the first surface of the back electrode 10 and the cymbal substrate 12 is provided. 11 ohm contact.

The material of the back electrode 10 may be a metal such as aluminum, magnesium or silver. The back electrode 10 has a thickness of 10 micrometers to 300 micrometers. It can be understood that the back electrode 10 is disposed on the first surface 11 of the cymbal substrate 12, and the back electrode 10 can form an ohmic contact with the first surface 11 of the cymbal substrate 12.

Referring to FIG. 9, a second embodiment of the present invention provides a solar cell 200. The solar cell 200 has substantially the same structure as the solar cell 100 in the first embodiment of the present invention, except that the solar energy in this embodiment is The battery 200 further includes a nano-scale metal layer 18 overlying the surface of the doped germanium layer 14. The metal layer 18 is a single layer layer structure or a plurality of layer structure formed by spreading a plurality of nano metal particles. The metal layer 18 has a thickness of 2 nm to 200 nm, and the material of the metal layer 18 is selected. Metal materials such as gold, silver, copper, iron or aluminum. In this embodiment, the metal layer 18 is a layer of nano gold particles having a thickness of about 50 nm.

The upper electrode 16 may also be in partial or complete contact with the metal layer 18. In this embodiment, the upper electrode 16 is partially suspended by the plurality of three-dimensional nanostructures 15 and is in partial contact with the metal layer 18.

It can be understood that a surface of the doped germanium layer 14 is coated with a nano-scale metal layer 18, and when incident light is transmitted through the upper electrode 16 to the metal layer 18, the surface plasma of the metal layer 18 is Excitation increases the absorption of photons by the doped germanium layer 14 located adjacent the metal layer 18. In addition, the electromagnetic field generated by the surface plasmon of the metal layer 18 is also advantageous for separating a plurality of electron-hole pairs generated in the P-N junction structure under the excitation of sunlight.

The present invention further provides a method for preparing the solar cell 200, which is basically the same as the method for preparing the solar cell 100 in the first embodiment of the present invention, except that the three-dimensional nanostructure 15 is After the second surface 13 of the cymbal substrate 12 between the surface and the adjacent three-dimensional nanostructures 15 forms a doped ruthenium layer 14, a metal layer 18 is further formed on the surface of the doped ruthenium layer 14. The metal layer 18 may be formed on the surface of the doped germanium layer 14 by electron beam evaporation.

Referring to FIG. 10, a third embodiment of the present invention provides a solar cell 300 including a back electrode 30, a germanium substrate 32, a doped germanium layer 34, and an upper electrode 36. The cymbal substrate 32 has a first surface 31 and a second surface 33 opposite to the first surface 31. The second surface 33 of the cymbal substrate is provided with a plurality of three-dimensional nanostructures 35. The three-dimensional nanostructure 35 is a stepped structure; the back electrode 30 is disposed on the first surface 31 of the cymbal substrate 32 and is in ohmic contact with the first surface 31; the doped yttrium layer 34 is formed on The surface of the three-dimensional nanostructure 35 and the second surface 33 of the cymbal substrate 32 between adjacent three-dimensional nanostructures 35; the upper electrode 36 is disposed on at least a portion of the surface of the doped yttrium layer 34.

The solar cell 300 is substantially the same as the solar cell 100 of the first embodiment of the present invention, except that in the embodiment, the three-dimensional nanostructure 35 is a stepped recessed structure, and the stepped shape The recessed structure is a space of a stepped recess formed inwardly recessed from the second surface 33 of the cymbal substrate 32, that is, an imaginary structure. . The stepped recessed structure is a plurality of layer structures, such as a plurality of layers of triangular prisms, a plurality of layers of quadrangular terraces, a plurality of layers of hexagonal prisms, a plurality of layers of cylinders or a plurality of layers of circular tables. The maximum dimension of the stepped recessed structure is less than or equal to 1000 nm, that is, its length, width and height are less than or equal to 1000 nm. Preferably, the stepped recessed structure The length, width and height range from 10 nm to 500 nm. In this embodiment, the stepped recess structure is a plurality of layered cylindrical structures. The stepped recessed structure is a plurality of layers of cylindrical structures, which means that the space of the stepped recesses is a plurality of layers of cylindrical shapes.

Referring to FIG. 11 , in the embodiment, the three-dimensional nanostructure 35 is a double-cylindrical space, specifically including a first cylindrical space 352 and a first cylindrical space 352 . The second cylindrical space 354. The first cylindrical space 352 is disposed coaxially with the second cylindrical space 354. The first cylindrical space 352 is disposed adjacent to the second surface 33 of the cymbal substrate 32. The diameter of the first cylindrical space 352 is larger than the diameter of the second cylindrical space 354. The first cylindrical space 352 has a diameter of 30 nm to 1000 nm and a height of 50 nm to 1000 nm. The second cylindrical space 354 has a diameter of 10 nm to 500 nm and a height of 20 nm to 500 nm. The dimensions of the first cylindrical space 352 and the second cylindrical space 354 can be prepared according to actual needs.

The plurality of three-dimensional nanostructures 35 are disposed in an array on the second surface 33 of the cymbal substrate 32. The arrangement in the form of an array means that the plurality of three-dimensional nanostructures 35 can be arranged in a simple cubic arrangement, a concentric annular arrangement or a hexagonal dense arrangement, and the plurality of three-dimensional images are arranged in an array form. The nanostructures 35 can form a single pattern or a plurality of patterns. The distance between the adjacent two three-dimensional nanostructures 35 is equal. The distance between the adjacent two three-dimensional nanostructures 35 is from 10 nm to 1000 nm. The form in which the plurality of three-dimensional nanostructures 35 are disposed on the second surface 33 of the cymbal substrate 32 and the distance between the adjacent two three-dimensional nanostructures 35 can be prepared according to actual needs. In this embodiment, the plurality of three-dimensional nanostructures 35 are arranged in a hexagonal densely packed pattern to form a single square pattern, and two adjacent three The distance between the Vennite structures 35 is approximately 50 nm.

It can be understood that a plurality of nano-scale stepped recess structures are disposed on the second surface 33 of the cymbal substrate 32 to allow the second surface 33 of the cymbal substrate 32 to have a larger PN junction interface area. Thereby, the photoelectric conversion efficiency of the solar cell 300 is improved. In addition, when light is irradiated to the stepped recessed structure, the irradiated light may be reflected and absorbed in the stepped recessed structure for a plurality of times, thereby increasing the light trapping performance of the doped germanium layer; The plurality of three-dimensional nanostructures 35 also have the characteristics of a photonic crystal, and can also increase the residence time of the photons in the three-dimensional nanostructures 35 and the frequency range of the absorbed light of the three-dimensional nanostructures 35, thereby improving the solar cell. 300 absorbance efficiency, which in turn increases the photoelectric conversion efficiency of the solar cell 300.

It can be understood that the solar cell 300 can further include an intrinsic tunnel layer (not shown) disposed between the enamel substrate 32 and the doped yttrium layer 34. The intrinsic tunnel layer can reduce the recombination speed of the electron-hole pair at the contact surface of the enamel substrate 32 and the doped yttrium layer 34, thereby further improving the photoelectric conversion efficiency of the solar cell 300. In addition, the solar cell 300 may further include a nano-scale metal layer (not shown) overlying the surface of the doped germanium layer 34. This metal layer has the same material and thickness as the metal layer 18 in the second embodiment of the present invention.

The present invention further provides a method for preparing the solar cell 300, which is basically the same as the method for preparing the solar cell 100 in the first embodiment of the present invention, except that the three-dimensional nanometer in this embodiment is used. The structure is a stepped recessed structure, so in the present embodiment, the second surface 23 of the meandering substrate 22 is shaped A continuous film having a plurality of openings is formed as the mask layer 24. It can be understood that when a continuous film having a plurality of openings is used as the mask layer 24, on the one hand, the reactive etching gas 26 etches the second surface 23 of the germanium substrate 22 corresponding to the opening portion of the continuous film. Thereby forming a second cylindrical space 354; on the other hand, the reactive etching gas 26 simultaneously etches the continuous film on the second surface 23 of the ruthenium substrate 22, making the opening in the continuous film larger The etched range of the reactive etching gas 26 to the second surface 23 of the ruthenium substrate 22 is made larger, thereby forming the first cylindrical space 352, and finally a stepped recess structure is prepared at a position corresponding to the opening. It can be understood that the spacing between the three-dimensional nanostructures 35 and the dimensions of the first cylindrical space 352 and the second cylindrical space 354 in the three-dimensional nanostructure 35 can be controlled by controlling the etching time of the reactive etching gas 26. The continuous film having a plurality of openings can be prepared by nanoimprinting, template deposition, or the like.

The solar cell of the embodiment of the present invention has the following advantages: first, a plurality of stepped three-dimensional nanostructures are disposed on the surface of the enamel substrate to increase the light extraction area of the solar cell; secondly, the stepped shape The convex structure or the stepped recess structure may cause incident sunlight to be reflected and absorbed in the stepped convex structure or the stepped concave structure, thereby increasing the light trapping performance of the doped germanium layer and the The efficiency of light absorption of the solar cell in various directions, so that the utilization ratio of the solar cell to light can be improved; again, a surface of the doped germanium layer is coated with a layer of nano-scale metal, when the incident light passes through When the upper electrode of the solar cell is irradiated to the metal layer, due to the surface plasma effect of the metal layer, the absorption performance of the doped germanium layer near the metal layer can be increased, and the separation is facilitated by the excitation of sunlight. a plurality of electron-hole pairs generated in the PN junction structure; finally, the ladder The three-dimensional nanostructure also has the characteristics of a photonic crystal, which can increase the retention time of photons in the three-dimensional nanostructure and the frequency range of absorption of sunlight by the three-dimensional nanostructure, thereby improving the photoelectric conversion efficiency of the solar cell.

A method for preparing a solar cell according to an embodiment of the present invention, wherein a method of combining a mask layer and a reactive etching gas forms a stepped three-dimensional nanostructure on the second surface of the enamel substrate to increase The light extraction area of the solar cell, and the method is simple in process and low in cost.

In summary, the present invention has indeed met the requirements of the invention patent, and has filed a patent application according to law. However, the above description is only a preferred embodiment of the present invention, and it is not possible to limit the scope of the patent application of the present invention. Equivalent modifications or variations made by those skilled in the art in light of the spirit of the invention are intended to be included within the scope of the following claims.

100‧‧‧ solar cells

10‧‧‧Back electrode

11‧‧‧ first surface

12‧‧‧矽 substrate

13‧‧‧ second surface

14‧‧‧Doped layer

15‧‧‧Three-dimensional nanostructure

16‧‧‧Upper electrode

Claims (24)

A solar cell, the improvement comprising: a cymbal substrate having a first surface and a second surface disposed opposite the first surface, the cymbal substrate The two surface etching is formed with a plurality of three-dimensional nanostructures, the three-dimensional nanostructure is a stepped structure; a back electrode, the back electrode is disposed on the first surface of the enamel substrate, and is ohmic with the first surface Contacting; a doped germanium layer, the doped germanium layer disposed on a surface of the three-dimensional nanostructure and a second surface of the germanium substrate between adjacent three-dimensional nanostructures; and an upper electrode, The upper electrode is disposed on at least a portion of the surface of the doped germanium layer. The solar cell according to claim 1, wherein the stepped structure is a stepped convex structure or a stepped concave structure. The solar cell according to claim 2, wherein the stepped protrusion structure or the stepped recess structure has a maximum size of 1000 nm or less. The solar cell according to claim 2, wherein the stepped structure is a plurality of layers of triangular prisms, a plurality of layers of quadrangular prisms, a plurality of layers of hexagonal prisms, a plurality of layers of cylinders or a plurality of layers of circular tables. The solar cell of claim 1, wherein the three-dimensional nanostructure comprises a first cylinder and a second cylinder disposed on the upper surface of the first cylinder, and the diameter of the first cylinder is larger than the diameter of the second cylinder The first cylinder and the second cylinder are integrally formed and coaxially disposed. The solar cell of claim 5, wherein a diameter of a bottom surface of the first cylinder It is 50 nm to 1000 nm, and the height is 100 nm to 1000 nm; the diameter of the bottom surface of the second cylinder is 10 nm to 500 nm, and the height is 20 nm to 500 nm. The solar cell of claim 1, wherein the plurality of three-dimensional nanostructures are disposed in an array on the second surface of the cymbal substrate. The solar cell of claim 1, wherein the plurality of three-dimensional nanostructures are disposed on the cymbal substrate in a simple cubic arrangement, a concentric annular arrangement, or a hexagonal dense arrangement Two surfaces. The solar cell of claim 1, wherein the plurality of three-dimensional nanostructures form a single pattern or a plurality of patterns. The solar cell of claim 1, wherein the three-dimensional nanostructure and the cymbal substrate are of a unitary structure. The solar cell of claim 1, wherein the distance between the adjacent two three-dimensional nanostructures is from 10 nm to 1000 nm. The solar cell of claim 1, further comprising an intrinsic tunnel layer disposed between the enamel substrate and the doped ruthenium layer. The solar cell of claim 1, further comprising a metal layer of a nanometer scale, the metal layer being coated on a surface of the doped germanium layer. The solar cell according to claim 13, wherein the metal layer has a thickness of 2 nm to 200 nm. The solar cell according to claim 1, wherein the upper electrode is suspended by the plurality of three-dimensional nanostructure portions and is in contact with the doped germanium layer forming portion. The solar cell of claim 1, wherein the upper electrode is coated on a surface of the doped germanium layer and is in complete contact with the doped germanium layer. The solar cell according to claim 1, wherein the upper electrode is an indium tin oxide structure or a carbon nanotube structure. A solar cell comprising a back electrode disposed in order from bottom to top, a germanium substrate, a doped germanium layer, and an upper electrode, wherein the germanium substrate is etched near the surface of the upper electrode A plurality of three-dimensional nanostructures having a stepped structure, the doped germanium layer being disposed on a surface of the three-dimensional nanostructure and a surface of the germanium substrate between adjacent three-dimensional nanostructures. A method of fabricating a solar cell, comprising the steps of: providing a cymbal substrate having a first surface and a second surface disposed opposite the first surface, the cymbal substrate The second surface etching is formed with a plurality of stepped three-dimensional nanostructures; a doped germanium layer is formed on the surface of the germanium substrate between the three-dimensional nanostructure surface and the adjacent three-dimensional nanostructure; An electrode disposed on at least a portion of a surface of the doped germanium layer; and a back electrode disposed on the first surface of the germanium substrate such that the back electrode An ohmic contact with the first surface of the cymbal substrate. The method for preparing a solar cell according to claim 19, wherein the enamel substrate is prepared by providing a ruthenium substrate, the ruthenium substrate comprising a first surface and a first surface opposite to the first surface a second surface; forming a mask layer on the second surface of the germanium substrate; etching the mask layer while etching the second surface of the germanium substrate with a reactive etching gas, in the germanium substrate The second surface forms a plurality of steps a three-dimensional nanostructure; and removing the mask layer. The method of producing a solar cell according to claim 20, wherein the method of forming a mask layer on the second surface of the ruthenium substrate is to form a single layer of nanospheres on the second surface of the ruthenium substrate. The method for producing a solar cell according to claim 21, wherein the method of forming a single layer of nanospheres on the second surface of the ruthenium substrate is a pulling method or a spin coating method. The method of producing a solar cell according to claim 20, wherein the step of etching the second surface of the tantalum substrate with a reactive etching gas is performed in a microwave plasma system. The method for preparing a solar cell according to claim 20, wherein the method of forming a mask layer on the second surface of the germanium substrate is to form a continuous plurality of openings on the second surface of the germanium substrate. membrane.