JP5518910B2 - Method for manufacturing polycrystalline silicon substrate for composite solar cell - Google Patents

Description

  The present invention relates to a method for manufacturing a silicon substrate, and more particularly to a method for manufacturing a polycrystalline silicon substrate for a composite solar cell.

  The development of photoelectric devices is an important industry that has been emphasized in Taiwan for several years, and Taiwan's share of semiconductors and light-emitting diodes is one of the top in the world. In recent years, more efficient solar cells have been actively developed. A solar cell absorbs light rays mainly by a semiconductor element, and converts the absorbed light rays into electric energy. The light source absorbed by the solar cell includes sunlight, an artificial light source, and the like. According to the principle of polymer solar cells, when a solar cell is irradiated with light, a photoactive layer made of a conductive polymer absorbs light energy to generate excitons, which are separated at the interface site. Electrons and holes are generated, and the electrons and holes are respectively conducted through different electrode plates through the electron conducting material and the hole conducting material, thereby forming a current path.

  Current mainstream solar cells are manufactured using crystalline bulk silicon. Usually, in the manufacturing method of a polycrystalline silicon wafer, first, the entire silicon ingot is cut into a plurality of thin wafers (180 μm to 200 μm) by saw wires. Usually, a wafer is doped with a small amount of p-type, and then the surface of the wafer is doped with an n-type dopant to form a pn junction at a few hundred nanometers below the wafer surface by surface diffusion of the n-type dopant. To do.

  However, in order to obtain better photoelectric conversion efficiency, the polycrystalline silicon wafer used by the prior art needs to have high purity. However, in order to have high purity, the silicon material needs to be subjected to a purification process a plurality of times. Therefore, there are disadvantages in that energy is wasted, costs are increased, and the environment is not friendly. Further, in an actual solar cell structure, the active layer providing the photoelectric conversion function needs only a thickness of 5 μm to 10 μm, and thus there is a disadvantage that other high-purity substrates are wasted. Thus, how to provide a method for producing a polycrystalline silicon substrate for a composite solar cell that can reduce the cost of the solar cell and obtain good photoelectric conversion efficiency is an issue.

  It is an object of the present invention to effectively reduce the cost of solar cell materials by forming a polycrystalline silicon substrate that is a composite substrate by forming a high purity silicon material on a low cost substrate with a general purity. An object of the present invention is to provide a method for producing a polycrystalline silicon substrate for a composite solar cell.

  The present invention provides a method for producing a polycrystalline silicon substrate for a composite solar cell, the step of preparing a first base layer having a purity of 2N to 3N, and a purity of 6N on the first base layer. Forming a second base material layer that is ˜9N.

  In the present invention, in a semiconductor process, a high-quality high-purity epitaxy layer or a high-purity sputtering layer is formed on a low-purity substrate and used as an active layer of a solar cell. The amount can be reduced, the conventional solar cell made of bulk silicon can be replaced, and the cost of the entire solar cell can be reduced.

The schematic diagram of the 1st base material layer of the present invention is shown. 1 is a schematic view of a polycrystalline silicon substrate for a composite solar cell according to the present invention. The schematic diagram of the solar cell which concerns on this invention is shown. 1 is a flowchart of a method for manufacturing a polycrystalline silicon substrate for a composite solar cell according to the present invention.

  Hereinafter, the embodiments of the present invention disclosed in the specification and the drawings are merely examples for explaining the technical contents of the present invention more clearly and helping the understanding of the present invention. It does not limit the range. It is obvious to those skilled in the art to which the present invention pertains that other variations based on the technical idea of the present invention can be implemented in addition to the embodiments disclosed herein. .

  In the method for manufacturing a polycrystalline silicon substrate for a composite solar cell according to the present invention, since the manufactured polycrystalline silicon substrate has a composite structure, the amount of high-purity polycrystalline silicon material used is reduced. In addition, the cost of the polycrystalline substrate and the solar cell can be reduced.

  This will be described with reference to FIGS. The method for producing a polycrystalline silicon substrate for a composite solar cell according to the present invention includes at least the following steps.

  In step S101, the first base material layer 11 is prepared. In the present embodiment, the first base material layer 11 is a low-purity silicon material, and its purity is, for example, about 2N (that is, 99%) to 3N (that is, 99.9%). In other words, the first base material layer 11 is an industrial-level silicon material that is easily obtained at low cost. In this embodiment, the first base layer 11 is made of industrial-grade silicon such as model numbers 411, 421, 553, 2202, and 3303 manufactured by a company called “SHANGHAI YIXIN CHEMICAL CO., LTD”. It is selected from materials. Moreover, the thickness of the 1st base material layer 11 is 160 micrometers-180 micrometers.

  In step S <b> 103, the second base material layer 12 is formed on the first base material layer 11. Compared to the first base material layer 11, the second base material layer 12 is a high-purity silicon material, and its purity is about 6N (ie 99.9999%) to 9N (ie 99.999999999%). It is. The thickness of the 2nd base material layer 12 is about 5 micrometers-20 micrometers. The second base material layer 12 is a high-purity silicon material belonging to an electronic level silicon material, and mainly functions as an active layer of a solar cell. Preferably, the thickness of the second base material layer 12 is smaller than the length of the electron diffusion range. Thereby, problems such as electron-hole scattering and electron-hole coupling due to the active layer being too thick can be improved, the amount of high-purity silicon material used can be reduced, and the material cost can be reduced.

  The second base layer 12 is formed by a method such as physical vapor deposition (PVD), chemical vapor deposition (CVD), or liquid-phase epitaxy (LPE). Although it may be formed on the first base material layer 11, the present invention is not limited to this. Hereinafter, specific steps of the chemical vapor deposition method and the sputtering method according to the present embodiment will be described in detail.

  In chemical vapor deposition, a reaction source is introduced into a reaction chamber by a gas method, and then a chemical reaction is performed by a method such as oxidation, reduction, or reaction with a substrate. And the other process gases are pulled away from the substrate surface. Specifically, the chemical vapor deposition process includes the following five main steps (a) to (e). (A) First, a reaction gas and an inert gas for dilution are introduced into the deposition chamber. Hereinafter, a mixed gas composed of a reaction gas and an inert gas is referred to as a main stream. (B) The atoms or molecules of the reaction gas in the main airflow diffuse and move inward, pass through the stagnant boundary layer, and arrive at the substrate surface. (C) The atoms of the reaction gas are adsorbed on the substrate. (D) The adsorbed atoms move on the surface of the substrate and cause a surface chemical reaction necessary for thin film growth. (E) The gas product that has undergone a surface chemical reaction is decomposed, diffuses outward, passes through the boundary layer, enters the main stream, and is removed from the deposition chamber.

In the present embodiment, the second base material layer 12 that is a silicon material having a dopant is formed on the first base material layer 11. Further, a gas material source of Si atoms is dichlorosilane (DCS) (SiH ₂ Cl ₂ ), silane, trichlorosilane (Cl ₃ SiH), tetrachlorosilane (Cl ₄ Si), or the like, and boron (B) The source material of the doping gas may be diborane (B ₂ H ₆ ) which is p-type doped silicon, PH ₃ or AsH ₃ may be n-type doped silicon, and the carrier gas may be hydrogen. Specifically, in this embodiment, the main airflow includes dichlorosilane, diboranes, and hydrogen. A main air stream is passed through the first base material layer 11 and a chemical reaction is performed at 1000 ° C. to 1100 ° C. for 20 to 30 minutes, thereby forming a 15 μm p-Si (ie, p-type doped silicon) The two base material layers 12 may be epitaxially grown.

As other process parameters, the flow rate of dichlorosilane is about 200 sccm to 300 sccm (standard cm ³ / min), the flow rate of diborane is about 5 sccm to 10 sccm, the flow rate of hydrogen is about 80 sccm to 100 sccm, The material layer 11 may be heated at about 300 ° C. to 350 ° C., and the pressure may be about 0.8 Torr to 1 Torr.

The second base material layer 12 may be a sputtering layer. For example, when a silicon thin film is grown on the first substrate layer 11 by a pulsed direct-current magnetron sputtering (Pluse-DC) facility in a sputtering process, a backing pressure of about 5 × 10 ⁻ is used as a process parameter. ⁷ Torr to 9 × 10 ⁻⁷ Torr, sputtering power to 100 W to 300 W, stage temperature to 200 degrees to 250 degrees, deposition pressure to about 5 mTorr, and Ar gas flow rate to about 8 sccm to 10 sccm.

  Further, with regard to the crystallinity of the second base material layer 12, considering that the second base material layer 12 may become an amorphous layer after performing a certain growth process, it is polycrystalline. The process may further include a conversion step. For example, the second base material layer 12 may be formed as a polycrystalline material by a method such as a laser crystal method. For example, when an amorphous second substrate layer 12 is irradiated with an excimer laser, the temperature is raised to about 1400 degrees at about 20 ns of the laser pulse, and cooling is performed after the laser pulse is completed. Start.

FIG. 3 is a schematic view of a solar cell formed by a polycrystalline silicon substrate manufactured by the method for manufacturing a polycrystalline silicon substrate for a composite solar cell according to the present invention. The solar cell includes a first base material layer 11, a second base material layer 12, and electrodes 14A and 14B provided on the polycrystalline silicon substrate. Since the first base material layer 11 has already been described in the above embodiment, the description thereof is omitted here. The second substrate layer 12 may be converted into an n ⁺ -Si emitter layer 12 ′ by a thermal diffusion process of phosphorous atoms or an ion implantation process of phosphorus atoms. Preferably, the solar cell further has an antireflection layer 13 formed on the emitter layer 12 ′. The antireflection layer 13 may be, for example, a silicon nitride layer. The electrode (ie, front electrode) 14A has a titanium / palladium / gold structure, and may be provided on the emitter layer 12 ′. On the other hand, the electrode (that is, the back electrode 14B) may be formed by coating the back surface of the first base material layer 11 with a highly conductive metal such as an aluminum paste.

As described above, the present invention has at least the following merits.
(1) A polycrystalline silicon substrate for a composite solar cell manufactured by the method for manufacturing a polycrystalline silicon substrate for a composite solar cell according to the present invention grows a high-purity silicon material on a low-purity substrate. As a result, a conventional substrate made of high-cost, high-purity bulk silicon can be replaced, and the overall cost can be reduced.
(2) Since the polycrystalline silicon substrate for a composite solar cell manufactured by the method for manufacturing a polycrystalline silicon substrate for a composite solar cell according to the present invention can be applied to a solar cell, high-efficiency and low-cost epitaxial silicon (Epitaxial silicon) solar cells can be provided.

  The above-described embodiments are merely preferred embodiments of the present invention, and do not limit the scope of the present invention. Equivalent changes and additions made based on the specification and drawings of the present invention will Are intended to be included within the scope of the claims.

DESCRIPTION OF SYMBOLS 11 1st base material layer 12 2nd base material layer 12 'Emitter layer 13 Antireflection layer 14A, 14B Electrode S101-S103 Process process

Claims (6)

Preparing a first base material layer having a purity of 2N to 3N;
Forming a second base material layer having a purity of 6N to 9N on the first base material layer ,
In the step of forming the second substrate layer, dichlorosilane having a flow rate of about 200 sccm to 300 sccm, diborane having a flow rate of about 5 sccm to 10 sccm, and hydrogen having a flow rate of 80 sccm to 100 sccm are used as a main air flow by chemical vapor deposition. Then, the second base material layer that is p-type doped silicon is formed by passing the first base material layer through the main air flow and performing a chemical reaction at 1000 ° C. to 1100 ° C. for 20 to 30 minutes. A method for producing a polycrystalline silicon substrate for a composite solar cell.   Preparing a first base material layer having a purity of 2N to 3N;
  Forming a second base material layer having a purity of 6N to 9N on the first base material layer;
  Comprising
  In the step of forming the second base material layer, the back pressure is set to about 5 × 10 6 by a pulsed DC magnetron sputtering facility. ^-7 Torr ~ 9 × 10 ^-7 The second base material layer is formed by a sputtering method with Torr, sputtering power of 100 W to 300 W, stage temperature of 200 degrees to 250 degrees, deposition pressure of about 5 mTorr, and Ar gas flow rate of about 8 sccm to 10 sccm. A method for producing a polycrystalline silicon substrate for a composite solar cell. In the step of preparing said first substrate layer, the thickness of the first substrate layer, the composite solar cell according to claim 1 or 2, characterized in that it is a 160μm~180μm A method for manufacturing a polycrystalline silicon substrate. In the step of forming the second base layer, the thickness of the second substrate layer, the composite solar cell according to claim 1 or 2, characterized in that it is a 5μm~20μm A method for manufacturing a polycrystalline silicon substrate. After the step of forming said second base layer to the first substrate layer, the composite solar cell according to claim 1 or 2, further comprising a multi-crystallization process A method for manufacturing a polycrystalline silicon substrate. 6. The method for producing a polycrystalline silicon substrate for a composite solar cell according to claim 5 , wherein in the polycrystallization step, the second base material layer is formed as a polycrystalline material by a laser crystallization method.

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