CN102280588A - Silicon-based nuclear shell nanowire photovoltaic cell and preparation process thereof - Google Patents

Abstract

The invention discloses a silicon-based core-shell nanowire photovoltaic cell and a preparation method thereof. The photovoltaic cell includes an N-type silicon substrate, an N-type silicon nanowire array is formed on the front side of the substrate as a photoactive layer, and a metal back electrode is provided on the bottom surface of the substrate. The silicon nanowire array is combined with a hole-transporting organic conductive polymer A core-shell nanowire Schottky heterojunction is formed, and an ITO top electrode is arranged on the heterojunction. Further, the organic conductive polymer includes PEDOT:PSS. The silicon nanowire array and the silicon substrate are formed of single crystal or polycrystalline silicon with a purity of 3-6N, the height of the nanowire is 3-5 μm, and the thickness of the substrate is 5-200 μm. The preparation process is as follows: a silicon nanowire array is prepared on the front side of an N-type silicon substrate by wet etching, and then a core-shell nanowire heterojunction is formed with a hole-transporting organic conductive polymer, and finally the silicon nanowire array is formed on the bottom surface of the silicon substrate and A metal back electrode and an ITO top electrode are respectively assembled on the heterojunction. The invention has the advantages of less raw material consumption, low cost, high conversion efficiency and simple preparation process.

Description

Silicon-based core-shell nanowire photovoltaic cell and its preparation process

technical field

The invention particularly relates to an N-type silicon/hole transport organic conductive polymer core-shell nanowire photovoltaic cell and a preparation process thereof, belonging to the technical field of solar energy conversion.

Background technique

Photovoltaic cells can continuously convert sunlight light sources into electrical energy to solve the current problems of energy depletion and environmental pollution that people are facing. Crystalline silicon photovoltaic cells have high photoelectric conversion efficiency and account for 80% of the entire photovoltaic market. However, the current high cost of crystalline silicon photovoltaic cells hinders the development of the photovoltaic power generation industry. Among them, crystalline silicon photovoltaic cells need to use a large amount (200-300 μm thick) and high purity (>6N grade) crystalline silicon as raw materials, and the cost of raw materials accounts for more than 40% of the entire photovoltaic module, which is the high cost of crystalline silicon photovoltaic cells a major factor. How to effectively reduce the amount of raw materials used on the basis of maintaining the efficiency of crystalline silicon photovoltaic cells is an effective way to reduce the cost of photovoltaic modules. Photovoltaic cells of silicon nanowire arrays enable this approach. Reported articles (eg, "Light trapping in silicon nanowire solar cells", "Nano Letters", 2010, 10, p1082–1087) mentioned that silicon nanowire arrays have excellent light trapping performance, and silicon nanowire arrays with a height of several μm The nanowire array can completely absorb the solar photons of 300-1100nm (the spectral range of silicon intrinsic absorption), which can effectively reduce the amount of crystalline silicon raw materials used. At the same time, the photovoltaic junction in this photovoltaic cell can be made into a core-shell nanowire structure, and the photogenerated carriers can be effectively separated by the photovoltaic junction when the silicon nanowire moves a short distance in the radial direction, thus allowing the use of low-quality silicon raw materials Devices are fabricated to further reduce the cost of silicon raw materials.

The key to obtaining the silicon nanowire photovoltaic cells mentioned above is to design and build photovoltaic junctions with a core-shell nanowire array structure. The invention patent application with the publication number CN101257094 mentions a heterojunction photovoltaic cell using a P-type silicon nanowire array/N-type organic semiconductor hybrid. In this photovoltaic cell, it is mentioned that the silicon nanowire array acts as an anti-reflection layer for sunlight, and the photoactive layer (base region) of the device is still bulk crystalline silicon, and a high quantity and high quality silicon raw material is still required to make the device.

Contents of the invention

The object of the present invention is to propose a core-shell nanowire photovoltaic cell and its preparation process, which has low cost, high photoelectric conversion efficiency and is easy to prepare, thereby overcoming the deficiencies in the prior art.

In order to realize the above-mentioned purpose of the invention, the present invention has adopted following technical scheme:

A silicon-based core-shell nanowire photovoltaic cell, characterized in that: it includes an N-type silicon substrate, a silicon nanowire array is formed on the front of the N-type silicon substrate as a photoactive layer, and a metal back electrode is provided on the bottom surface of the N-type silicon substrate The silicon nanowire array is conformally covered with a hole-transporting organic conductive polymer to form a nanowire heterojunction with a core-shell structure as a photovoltaic junction, and an ITO top electrode is arranged on the heterojunction.

Preferably, the hole-transporting organic conductive polymer includes PEDOT:PSS.

Both the N-type silicon nanowire array and the silicon substrate are formed of single crystal or polycrystalline silicon with a purity of 3-6N, wherein the height of the silicon nanowires is 3-5 μm, and the thickness of the silicon substrate is 5-200 μm.

The metal back electrode includes an Al electrode layer covering the bottom surface of the N-type silicon substrate, and the ITO top electrode includes ITO glass covering the heterojunction. the

A preparation process for a silicon-based core-shell nanowire photovoltaic cell, characterized in that the process is: using wet etching to prepare a silicon nanowire array on the front side of an N-type silicon substrate, and then using hole transport organic conductive polymerization The material is conformally covered on the silicon nanowire array to form a core-shell nanowire heterojunction. Finally, a metal back electrode and an ITO top electrode are respectively assembled on the bottom surface of the N-type silicon substrate and the heterojunction to obtain the target product.

Further, the process specifically includes the following steps:

1. Prepare silicon nanowire arrays on the front side of the N-type silicon substrate by using catalytically active metals to assist silicon chemical etching;

ii. After filling the silicon nanowire array with a solution of a hole-transporting organic conductive polymer, evaporate and remove the solvent in the organic conductive polymer solution to form an organic conductive polymer film conformally covering the silicon nanowire array;

Ⅲ. Assemble a metal back electrode and an ITO top electrode on the bottom surface of the N-type silicon substrate and the heterojunction respectively to obtain the target product.

Step i is specifically as follows: firstly, a discontinuous silver film is formed by electroless deposition on the front side of the N-type silicon substrate, and then by means of the catalytic action of the silver film, silicon nanowire arrays are formed on the front side of the N-type silicon substrate by wet etching, and finally Remove the silver film.

The hole-transporting organic conductive polymer includes PEDOT:PSS, and the metal back electrode includes an Al electrode layer deposited on the bottom surface of the N-type silicon substrate.

The process of assembling the ITO top electrode on the heterojunction array is:

The conductive surface of the ITO glass is coated with a hole-transporting organic conductive polymer solution, placed on the surface of the heterojunction, and then evaporated to remove the solvent in the organic conductive polymer solution, so that the conductive surface of the ITO glass is in contact with the heterojunction. Mass knot fixed connection.

The hole-transporting organic conductive polymer solution includes a polar organic solvent and a commercial PEDOT:PSS aqueous solution with a volume ratio of 1:3-1:1, and the polar organic solvent is at least selected from ethanol, acetone and isopropanol any of the.

The main features of silicon/PEDOT:PSS core-shell nanowire photovoltaic cell of the present invention are: the photoactive layer is a silicon nanowire array located on a silicon substrate, and the photovoltaic junction is N-type silicon of core-shell nanowire structure and hole transport. Organic conductive polymers, especially PEDOT:PSS heterojunction, where PEDOT:PSS is conductive and transparent, and the Fermi level is close to the conduction band of silicon can effectively form a window layer/absorber type Schottky photovoltaic junction with silicon, there are conducive to photoelectric conversion. In addition, silicon nanowires and silicon substrates are formed of single crystal or polycrystalline silicon with a purity of 3-6N, the height of the nanowires is 3-5 μm, and the thickness of the substrate is 5-200 μm, which is beneficial to reduce device costs. In addition, the photovoltaic cell may also include top electrode ITO glass, Al bottom electrode and other components.

The main process of the manufacturing process of the photovoltaic cell of the present invention is: first metal assists silicon chemical etching to prepare silicon nanowire array on silicon substrate; The organic conductive polymer solution is filled into the metal-assisted silicon chemically etched silicon nanowire array, and the solvent is evaporated to form a silicon/PEDOT:PSS core-shell nanowire array; finally, the metal back electrode is prepared by thermal evaporation on the back surface of the silicon substrate And assemble the ITO top electrode on the front surface of the silicon/PEDOT:PSS core-shell nanowire array to form a photovoltaic device. Among them, due to the superhydrophobicity of the surface of the silicon nanowire array prepared by metal-assisted silicon chemical etching, it is difficult for the PEDOT:PSS aqueous solution to fill the silicon nanowire array and form the core-shell nanowire. Therefore, in the present invention, polar organic solvents such as alcohol, acetone or isopropanol are added to the PEDOT:PSS aqueous solution, so that the PEDOT:PSS solution can effectively fill the silicon nanowire array to form core-shell nanowires.

The working principle of the photovoltaic cell of the present invention is: sunlight passes through the ITO glass top electrode and the PEDOT:PSS layer is absorbed by the silicon nanowires, generating hole-electron pairs, and then the hole-electron pairs are separated by the silicon/PEDOT:PSS photovoltaic junction , the holes are transferred to the PEDOT:PSS layer and collected by the ITO top electrode, and the electrons are collected by the AL bottom electrode to realize the entire photoelectric conversion.

Compared with the prior art, the present invention has the advantages that: the silicon-based core-shell nanowire photovoltaic cell uses less raw materials, has low cost, high photoelectric conversion efficiency, and its preparation process is simple and easy to operate, and the scale of photovoltaic cells can be realized. chemical production.

Description of drawings

Fig. 1 is the structure diagram of silicon/PEDOT:PSS core-shell nanowire photovoltaic cell in the present invention, among the figure: 1 is AL bottom electrode, 2 is silicon substrate, 3 is silicon/PEDOT:PSS core-shell nanowire array, 31 Be silicon nanowire array, 32 is PEDOT:PSS layer, 4 is top electrode ITO glass;

Figure 2a is a scanning electron micrograph of the silicon/PEDOT:PSS core-shell nanowire array shown in Figure 1;

Figure 2b is a transmission electron micrograph of a single silicon/PEDOT:PSS core-shell nanowire;

Figure 2c is a transmission electron micrograph of the silicon/PEDOT:PSS core-shell nanowire interface;

Figure 3 is a current-voltage characteristic curve of a typical silicon/PEDOT:PSS core-shell nanowire photovoltaic cell of the present invention under AM 1.5G simulated sunlight.

specific implementation plan

The technical solution of the present invention will be described in detail below in conjunction with the accompanying drawings and a preferred embodiment.

Referring to Fig. 1, the silicon/PEDOT:PSS core-shell nanowire photovoltaic cell is composed of ITO glass, silicon/PEDOT:PSS core-shell nanowire array, N-type silicon substrate and Al electrode.

The main feature of the photovoltaic cell is that the photoactive layer is a silicon nanowire array, and the photovoltaic junction is N-type silicon with a core-shell nanowire structure and a PEDOT:PSS heterojunction. Among them, PEDOT:PSS is conductive and transparent, and the Fermi level is close to the conduction band of silicon, which can effectively form a window layer/absorber type Schottky photovoltaic junction with silicon, which is beneficial to photoelectric conversion. The aforementioned silicon nanowires and silicon substrates are formed of single crystal or polycrystalline silicon with a purity of 3-6N, the height of the nanowires is 3-5 μm, and the thickness of the substrate is 5-200 μm, which is beneficial to reduce the raw material cost of the device.

The preparation process of the silicon/PEDOT:PSS core-shell nanowire photovoltaic cell comprises the following steps:

(1) Fabricate silicon nanowire arrays on silicon substrates. First, place the cleaned N-type silicon wafer in a mixed aqueous solution of 0.02M silver nitrate and 5M hydrofluoric acid at room temperature, and deposit a discontinuous silver film on the surface of silicon nanowires by electroless plating, and then place the sample in 4.6M hydrogen In a mixed aqueous solution of hydrofluoric acid and 0.8M hydrogen peroxide, metal-assisted silicon chemical etching was used to prepare silicon nanowire arrays. Finally, the etched silicon wafer was placed in 40% nitric acid to remove the silver catalyst, and then washed with 5% hydrofluoric acid and deionized water in sequence to obtain a silicon nanowire array 31 on the silicon substrate;

(2) Preparation of silicon/PEDOT:PSS core-shell nanowire arrays: Mix alcohol and commercial PEDOT:PSS aqueous solution at a volume ratio of 1:3, then spin-coat the mixed solution to fill the silicon nanowire arrays, and finally place the sample Evaporate the solvent in an oven at 120°C to obtain a silicon/PEDOT:PSS core-shell nanowire array 3 (see Figures 2a-2c);

(3) Preparation of silicon/PEDOT:PSS core-shell nanowire photovoltaic cells: first, Al electrodes were deposited on the back surface of the silicon substrate by thermal evaporation, and then a layer of wet PEDOT:PSS was spin-coated on the ITO glass and placed On the surface of the silicon/PEDOT:PSS core-shell nanowires, the sample was finally placed in an oven at 120°C to evaporate the solvent to obtain a silicon/PEDOT:PSS core-shell nanowire photovoltaic cell. The photovoltaic performance of the device was tested (see Figure 3), and its photoelectric conversion efficiency can reach more than 6%.

In the present invention, the photoactive layer is an N-type silicon nanowire array (3-5 μm), which can fully absorb 300-1100nm sunlight, and can reduce the amount of silicon raw materials used. At the same time, the present invention adopts the Schottky heterojunction formed by N-type silicon/hole-transporting organic conductive polymer of the core-shell nanowire structure as the photovoltaic junction, and the separation path of the photo-generated carriers in the photoactive layer is short, and can be used Low-purity, low-quality, cheap silicon raw materials are used to make devices. Moreover, the invention adopts the method of filling the organic conductive polymer solution to construct the photovoltaic junction, the process is simple, and a device with a large area can be constructed. In summary, the N-type silicon/hole transport organic conductive polymer core-shell nanowire photovoltaic cell of the present invention can achieve low cost and high efficiency.

The above is only an introduction to the essential features of the present invention through specific application examples, and does not constitute any limitation to the protection scope of the invention. All technical solutions formed by equivalent transformation or equivalent replacement fall within the protection scope of the present invention.

Claims (10)

1. a silica-based core-shell nano linear light lies prostrate battery, it is characterized in that: it comprises N type silicon substrate, described N type silicon substrate front is formed with silicon nanowire array as photoactive layer, its bottom surface is provided with metal back electrode, the nanowire heterojunction that the organic conductive polymer of conformal covering hole transport forms nucleocapsid structure on the described silicon nanowire array is as photovoltaic junction, and described heterojunction is provided with the ITO top electrode.

2. silica-based core-shell nano linear light volt battery according to claim 1, it is characterized in that: the organic conductive polymer of described hole transport comprises PEDOT:PSS.

3. silica-based core-shell nano linear light volt battery according to claim 1, it is characterized in that: described N type silicon nanowire array and silicon substrate are the monocrystalline or the polysilicon formation of 3-6N level by purity, wherein, the silicon nanowires height is 3-5 μ m, and silicon substrate thickness is 5-200 μ m.

4. silica-based core-shell nano linear light volt battery according to claim 1, it is characterized in that: described metal back electrode comprises the Al electrode layer that covers on N type silicon substrate bottom surface, and described ITO top electrode comprises the ito glass that covers on heterojunction.

5. the preparation technology of a silica-based core-shell nano linear light volt battery, it is characterized in that, this technology is: adopt wet etching to prepare silicon nanowire array in N type silicon substrate front, cover on the silicon nanowire array so that the organic conductive polymer of hole transport is conformal then, form core-shell nano line heterojunction, difference assembling metal back electrode and ITO top electrode on N type silicon substrate bottom surface and heterojunction obtain target product at last.

6. the preparation technology of silica-based core-shell nano linear light volt battery as claimed in claim 5 is characterized in that this technology specifically comprises the steps:

ⅰ, prepare silicon nanowire array in the positive metal assistance chemistry of silicones etching that adopts of N type silicon substrate with catalytic activity;

After ⅱ, the solution of getting the organic conductive polymer of hole transport were filled silicon nanowire array, the solvent in this organic conductive polymer solution was removed in evaporation, forms the conformal organic conductive thin polymer film that covers on the silicon nanowire array;

ⅲ, on N type silicon substrate bottom surface and heterojunction respectively assembling metal back electrode and ITO top electrode, obtain target product.

7. the preparation technology of silica-based core-shell nano linear light volt battery as claimed in claim 6, it is characterized in that, step I is specially: at first form discontinuous silver-colored film in the positive deposited electroless of N type silicon substrate, then by the catalytic action of silver-colored film, form silicon nanowire array at N type silicon substrate front wet etching, remove silver-colored film at last.

8. according to the preparation technology of claim 5 or 6 described silica-based core-shell nano linear lights volt batteries, it is characterized in that: the organic conductive polymer of described hole transport comprises PEDOT:PSS, and described metal back electrode comprises the Al electrode layer that is deposited on the N type silicon substrate bottom surface.

9. according to the preparation technology of claim 5 or 6 described silica-based core-shell nano linear light volt batteries, it is characterized in that the process of assembling ITO top electrode is on heterojunction array:

Get the organic conductive polymer solution that applies hole transport on the conducting surface of ito glass, and be placed on the heterojunction surface, the solvent in this organic conductive polymer solution is removed in evaporation then, and the conducting surface of ito glass is fixedlyed connected with heterojunction.

10. the preparation technology of silica-based core-shell nano linear light volt battery according to claim 6, it is characterized in that: the organic conductive polymer solution of described hole transport comprises that volume ratio is the polar organic solvent and the commercial PEDOT:PSS aqueous solution of 1:3-1:1, and described polar organic solvent is selected from any one in ethanol, acetone and the isopropyl alcohol at least.

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