Preparation method of silicon heterojunction solar cell

Abstract

The invention belongs to the technical field of solar cells, and particularly relates to a preparation method of a silicon heterojunction solar cell, which comprises the following steps of: 1, preparing an amorphous silicon layer on crystalline silicon; 2, preparing an island-shaped transparent conductive oxide particle layer on the surface of the amorphous silicon layer; 3, carrying out illumination treatment on the island-shaped transparent conductive oxide particle layer, so that light is gathered near an interface between the crystalline silicon and the amorphous silicon through the island-shaped transparent conductive oxide particle layer; and 4, preparing a transparent conductive oxide layer on the island-shaped transparent conductive oxide particle layer. The island-shaped transparent conductive oxide particle layer is prepared on the surface of the amorphous silicon layer, light energy is gathered near the interface of crystalline silicon and amorphous silicon, the problem that traditional vertical incident light cannot be effectively gathered is solved, the carrier separation and transmission efficiency is improved, and therefore the photoelectric conversion efficiency of the silicon heterojunction solar cell is improved, and the photoelectric conversion efficiency of the silicon heterojunction solar cell is improved. Good application prospects are realized.

Description

Technical Field

[0001] The invention belongs to the technical field of solar cells, and in particular relates to a method for preparing a silicon heterojunction solar cell. Background Art

[0002] Silicon heterojunction solar cells are a type of solar cell that combines amorphous silicon and single-crystal silicon, in which the amorphous silicon layer passivates the defects on the surface of the crystalline silicon, reduces surface recombination, improves the performance of the solar cell, and has a higher photoelectric conversion efficiency. However, despite the excellent performance of this type of solar cell in terms of efficiency, interface defects and surface recombination are still one of the main factors limiting the efficiency improvement.

[0003] Photoprocessing is a technology that uses light to change or optimize the physical and chemical properties of materials. In silicon heterojunction solar cells, the interface between crystalline silicon and amorphous silicon is a key part that affects the efficiency of the cell. Defects and mismatches on the interface lead to carrier recombination, which reduces the photoelectric conversion efficiency. Photoprocessing reduces recombination and improves the photoelectric conversion efficiency of the cell by exciting carriers near the interface, enhancing the generation of electron-hole pairs, or repairing interface defects through local thermal effects. In addition, light irradiation can promote lattice repair and defect elimination in the material by stimulating thermal effects in local areas. For example, light irradiation causes microscopic changes in the surface of amorphous silicon or crystalline silicon at the interface, thereby improving the conductivity and photoelectric conversion efficiency of the material.

[0004] When traditionally treating silicon heterojunction interfaces with light, vertical incident light is usually used, that is, the light is irradiated vertically onto the surface of the silicon heterojunction. Under vertical incidence, when light passes through the silicon heterojunction material, it will be absorbed or scattered by the surface and interior of the material, and it is difficult to effectively gather at the interface between amorphous silicon and crystalline silicon. Carrier recombination at the interface is a key factor limiting efficiency improvement. If the light cannot be sufficiently concentrated at the interface, then it cannot effectively reduce interface defects or improve photoelectric conversion efficiency. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a method for preparing a silicon heterojunction solar cell, which is characterized by comprising the following steps: Step 1, preparing an amorphous silicon layer on crystalline silicon; Step 2, preparing an island-shaped transparent conductive oxide particle layer on the surface of the amorphous silicon layer; Step 3, performing light treatment on the island-shaped transparent conductive oxide particle layer, so that light passes through the island-shaped transparent conductive oxide particle layer and is concentrated near the interface between crystalline silicon and amorphous silicon; Step 4: preparing a transparent conductive oxide layer on the island-shaped transparent conductive oxide particle layer.

[0006] The present invention prepares an island-shaped transparent conductive oxide particle layer on the surface of the amorphous silicon layer, and then performs light treatment to make the light pass through the particle layer to gather near the interface between crystalline silicon and amorphous silicon, thereby solving the problem that the traditional vertical incident light cannot gather light to the interface. Compared with the traditional light treatment method, the light treatment method of the present invention changes the propagation path of light through the scattering of island-shaped particles, enhances the light energy density at the interface, reduces the carrier recombination phenomenon, and improves the carrier separation and transmission efficiency at the interface, thereby improving the photoelectric conversion efficiency of silicon heterojunction solar cells.

[0007] Specifically, under vertical incident light, the island-shaped transparent conductive oxide particle layer gathers light at the interface between crystalline silicon and amorphous silicon through the scattering and refraction effects of light. The morphology and structure of the island-shaped transparent conductive oxide particle layer causes light to scatter when passing through the particle layer, changing the propagation path of light. These particles guide and concentrate light near the interface, enhancing the light energy density at the interface.

[0008] Furthermore, step 1 includes: Step 11, cleaning the n-type single crystal silicon by a wet chemical method; Step 12: Forming a pyramid-shaped light-trapping structure on the surface of n-type single-crystal silicon through a texturing process; Step 13: using plasma enhanced chemical vapor deposition technology to sequentially deposit an intrinsic amorphous silicon film and a p-type amorphous silicon film on the back side of the n-type single crystal silicon; Step 14: Use plasma enhanced chemical vapor deposition technology to sequentially deposit an intrinsic amorphous silicon film and an n-type amorphous silicon film on the front surface of the n-type single crystal silicon.

[0009] Furthermore, in step 13 and step 14, the thickness of the amorphous silicon film is 5 nm to 15 nm, and the thickness of the p-type amorphous silicon film or the n-type amorphous silicon film is 5 nm to 15 nm.

[0010] Furthermore, the material of the island-shaped transparent conductive oxide particle layer is ITO, FTO or SnO2.

[0011] Furthermore, in step 2, the island-shaped transparent conductive oxide particle layer is prepared by sputtering or thermal evaporation. When the island-shaped transparent conductive oxide particle layer is prepared on the surface of amorphous silicon by sputtering or thermal evaporation, the growth mechanism of the island-shaped particles is mainly related to the nucleation and growth dynamics during the thin film deposition process. During the sputtering or thermal evaporation process, the atoms or molecules of the oxide material are first deposited on the surface of amorphous silicon, and nucleation points are initially formed on the surface. Since the surface of amorphous silicon usually has a certain degree of roughness or energy inhomogeneity, these nucleation points are preferentially formed in high-energy areas or surface defects. With the further increase of the deposited material, the particles between the nucleation points gradually combine and grow with each other to form a particle layer with an island structure.

[0012] Furthermore, the material of the transparent conductive oxide layer is the same as that of the island-shaped transparent conductive oxide particle layer. The material of the transparent conductive oxide layer is the same as that of the island-shaped transparent conductive oxide particle layer, which helps to maintain the consistency of light transmission and interface matching. The use of the same material ensures the consistency of optical and electrical properties between the two layers, avoiding reflection, scattering or discontinuity of interface electrical properties caused by material mismatch. At the same time, this consistency also helps to reduce the loss of light at the interface and improve the photoelectric conversion efficiency. In addition, the consistency of the material allows the light gathering effect to be more smoothly transmitted to the entire interface area during light irradiation, further optimizing the carrier separation and transmission efficiency and improving the overall performance of the solar cell.

[0013] Furthermore, in step 4, the amorphous silicon layer is heated. Heating the amorphous silicon layer can improve the atomic or molecular diffusivity of the amorphous silicon surface and promote more uniform deposition of the transparent conductive oxide material on the surface. During the heating process, the surface energy of the amorphous silicon layer increases, which helps the attachment and uniform distribution of transparent conductive oxide particles, thereby avoiding aggregation or uneven deposition of particles. In addition, proper heating can also enhance the crystallinity and electron transport properties of the deposited layer, further optimize the electrical properties of the transparent conductive oxide layer, and enhance its application effect in silicon heterojunction solar cells.

[0014] Furthermore, in step 3, the light is irradiated at an angle. The obliquely incident light will scatter on the surface of the island-shaped transparent conductive oxide particles, so that the light energy forms a stronger coupling effect between the particles and the amorphous silicon. Since the amorphous silicon layer is very thin, the light field is distributed near the interface, thereby effectively concentrating the light energy at the interface region between crystalline silicon and amorphous silicon.

[0015] Furthermore, in step 3, the light is p-polarized. For p-polarized light, its electric field vector mainly vibrates along the incident plane, which makes the coupling effect of light at the interface more significant. The island-shaped transparent conductive oxide particle layer can produce a stronger interaction with p-polarized light, especially in the material near the interface, the propagation and aggregation ability of light is enhanced. Compared with s-polarized light, p-polarized light is more likely to produce a stronger reflection and scattering effect when interacting with the surface of the medium, which helps to gather light at the interface and improve the energy density, thereby effectively reducing the carrier recombination caused by interface defects and improving the photoelectric conversion efficiency.

[0016] Furthermore, in step 2, an island-shaped transparent conductive oxide particle layer is prepared on both the front and back sides; in step 3, a light treatment is performed on both the front and back sides; and in step 4, a transparent conductive oxide layer is prepared on both the front and back sides. The existence of the double-sided island-shaped transparent conductive oxide particle layer can effectively capture light in multiple directions. No matter which direction the light is incident from, light energy can be concentrated near the interface between crystalline silicon and amorphous silicon, thereby improving the light capture rate and the overall photoelectric conversion efficiency of the solar cell. Beneficial effects of the present invention: (1) The present invention prepares an island-shaped transparent conductive oxide particle layer on the surface of the amorphous silicon layer and performs light treatment to concentrate light energy near the interface between crystalline silicon and amorphous silicon, thereby overcoming the problem that traditional vertically incident light cannot be effectively concentrated; when applied, the carrier separation and transmission efficiency is improved, thereby improving the photoelectric conversion efficiency of silicon heterojunction solar cells, and has good application prospects.

[0017] (2) The present invention uses a transparent conductive oxide layer and an island-shaped transparent conductive oxide particle layer made of the same material, which helps to maintain the consistency of light transmission and interface matching, ensures the consistency of optical and electrical properties, and avoids reflection, scattering or discontinuity of interface electrical properties caused by material mismatch.

[0018] (3) In the prior art, precious metal particles gather light energy through the surface plasmon resonance effect, usually focusing light into the medium. However, there is inconsistency between the precious metal particles and the transparent conductive oxide material finally prepared, which easily leads to problems such as light scattering and conductivity differences. In addition, when removing the precious metal particles, there is often the challenge of incomplete removal, which not only affects the controllability of the preparation process, but also may affect the performance of the device. In contrast, the present invention uses the method of "island-shaped transparent conductive oxide particles" to gather light before preparing the transparent conductive oxide layer, so as to effectively focus light near the interface between crystalline silicon and amorphous silicon. This method does not introduce any new substances, avoids the problems that may be caused by precious metal particles, and ensures the compatibility and consistency of the materials. Through this innovative idea, not only can the interface light energy density be improved, but also the photoelectric conversion efficiency can be optimized, which has high technical feasibility and application potential.

[0019] Based on the above beneficial effects, the present invention has good application prospects in the field of solar cell technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of a method for preparing a silicon heterojunction solar cell. DETAILED DESCRIPTION

[0021] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and examples.

[0022] Example 1 The present invention provides a method for preparing a silicon heterojunction solar cell, such as Figure 1 As shown, the specific steps include: Step 1: Prepare an amorphous silicon layer on crystalline silicon.

[0023] First, the n-type single crystal silicon is cleaned by wet chemical methods. The cleaning process includes using deionized water and acidic solution to clean the surface and remove surface impurities and oxides. Next, the surface of the n-type single crystal silicon is treated by a texturing process to form a pyramid-shaped light-trapping structure, the purpose of which is to increase the surface light absorption area. Then, using plasma enhanced chemical vapor deposition (PECVD) technology, an intrinsic amorphous silicon film (10nm thick) and a p-type amorphous silicon film (10nm thick) are sequentially deposited on the back of the n-type single crystal silicon. In the same way, an intrinsic amorphous silicon film (10nm thick) and an n-type amorphous silicon film (10nm thick) are sequentially deposited on the front of the n-type single crystal silicon by PECVD to form the basic structure of the silicon heterojunction.

[0024] Step 2: preparing an island-shaped transparent conductive oxide particle layer on the surface of the amorphous silicon layer.

[0025] On the surface of the amorphous silicon layer, an island-shaped transparent conductive oxide particle layer is prepared by sputtering. Specifically, the material is selected as ITO (indium tin oxide), and is deposited on the surface of the amorphous silicon layer by DC sputtering technology. The sputtering power is 200W, the gas flow rate is 30sccm of argon gas, and the oxygen flow rate is 3sccm. The deposition time is 5 minutes, and an ITO island-shaped transparent conductive oxide particle layer of about 50nm thick is obtained. Due to the local deposition and particle growth characteristics during the sputtering process, the ITO layer forms an island structure, which allows light to scatter between particles and gather near the interface.

[0026] Preferably, the island-shaped transparent conductive oxide particles are hemispherical, the hemispherical shape is symmetrical, and the surface can uniformly guide the incident light for scattering. Due to its curvature distribution, the hemispherical particles can directionally focus light to its bottom and surrounding areas. In other words, the optical behavior of the hemispherical particles is similar to that of a microlens structure, which can concentrate more light energy at the interface between amorphous silicon and crystalline silicon by bending light, thereby enhancing the local light field. When preparing hemispherical island-shaped transparent conductive oxide particles, DC sputtering technology and rotating sample technology are used. During preparation, the amorphous silicon is first fixed on a rotating sample stage and rotated at a speed of 10-20rpm to ensure uniform distribution of the material during the sputtering process. The sputtering chamber is evacuated to less than 10⁻ 4After the vacuum degree of 1.5 Pa, argon (30-50 sccm) and oxygen (5-10 sccm) were introduced to stabilize the pressure in the chamber to 0.5-1 Pa, and the sputtering source was started to sputter ITO at a power of 150-300 W. In the early stage of sputtering, transparent conductive oxide particles formed nucleation points on the surface of amorphous silicon and gradually grew into hemispherical particles. The rotating sample technology effectively avoided particle accumulation or shadow effects and ensured uniform distribution of particles.

[0027] Step 3: performing light treatment on the island-shaped transparent conductive oxide particle layer.

[0028] The light source is a xenon lamp with a light intensity of about 100mW / cm² and an irradiation time of about 10 minutes. Through light treatment, the light excites more carriers near the interface and reduces interface defects, thereby improving the separation efficiency of interface carriers. Preferably, the intensity of the light source for light treatment is adjustable, and the light intensity changes from weak to strong, gradually exciting the generation of carriers and defect repair in the interface area, avoiding overheating or material damage caused by excessive light intensity. Furthermore, during the light treatment process, a weak electric field is applied to enhance the effect of light treatment. The electric field is used to induce the optimization of interface charge distribution and carrier migration behavior, thereby reducing the interface defect density and improving the separation and transmission efficiency of carriers. Specifically, an electrode is set near the interface of crystalline silicon and amorphous silicon to form a weak electric field perpendicular to the direction of light treatment. The electrode material can be selected from transparent conductive oxides (such as ITO or FTO) to ensure that the transmission of light is not affected. The electric field strength is in the range of 0.1~1 V / µm, and the electrode spacing is in the range of 1~10mm. The applied electric field is a DC electric field or a low-frequency AC electric field (frequency range is 10Hz~1kHz). During the light treatment process, the weak electric field and light work together to promote the migration of carriers at the interface to the corresponding electrode area, effectively reducing the interface recombination phenomenon.

[0029] Step 4: preparing a transparent conductive oxide layer on the island-shaped transparent conductive oxide particle layer.

[0030] A transparent conductive oxide layer is prepared on the island-shaped transparent conductive oxide particle layer by thermal evaporation. The material selected is the same as that of the island-shaped transparent conductive oxide particle layer, namely ITO, and is deposited by thermal evaporation technology. The deposition conditions are an evaporation source power of 150W, a deposition rate of 0.3nm / s, and a deposition thickness of 100nm. In this process, in order to promote molecular diffusion and enhance the structural consistency of the transparent conductive oxide layer, the amorphous silicon layer will be treated by heating during the evaporation process. The heating temperature is controlled at 150°C and the heating is continued for 20 minutes to promote the diffusion of transparent conductive oxide molecules on the surface of amorphous silicon, improve the adhesion and interface quality of the transparent conductive oxide layer, and ensure the stability and uniformity of its electrical properties.

[0031] Since amorphous silicon layers are provided on both sides of crystalline silicon, when preparing the ITO layer by thermal evaporation, the solar cell needs to be suspended in the air to avoid direct contact between the heating platform and the amorphous silicon layer, resulting in damage or affecting the uniformity of film deposition. The suspended clamping device of the present invention is made of a material (such as quartz or ceramic) that is resistant to high temperatures and has low thermal conductivity, and is designed as a frame structure for fixing the edge of the solar cell so that both sides are suspended in the air to avoid direct contact with the heating platform and the surface of the equipment. The contact between the clamping device and the solar cell is limited to non-functional areas, which protects the integrity of the amorphous silicon layer and the island-shaped transparent conductive oxide particle layer to the greatest extent. The present invention adopts an infrared heating method, and the infrared heating device is installed inside the thermal evaporation equipment, and a multi-directionally distributed infrared heat source is used, which is arranged around the solar cell, and the suspended solar cell is evenly heated when preparing the transparent conductive oxide layer. The heating device is equipped with a precise temperature control system to stably control the temperature at 150°C, promote the uniform deposition and molecular diffusion of the transparent conductive oxide layer, and optimize the interface contact quality and the photoelectric performance of the solar cell.

[0032] Furthermore, the material of the island-shaped transparent conductive oxide particle layer and the transparent conductive oxide layer may also be FTO or SnO2.

[0033] Example 2 On the basis of Example 1, in step 3, the island-shaped transparent conductive oxide particle layer is treated with light using oblique p-polarized light, the light source is a xenon lamp, the wavelength range is 400nm to 800nm, the light intensity is about 100mW / cm², the irradiation time is about 10 minutes, and the incident angle is 45 degrees. The electric field direction of the p-polarized light helps to stimulate the optical coupling effect between the island-shaped transparent conductive oxide particle layer and the amorphous silicon layer. At the same time, when the incident light is oblique, its reflectivity is low, and more light energy can enter the amorphous silicon layer, enhancing the light absorption and energy density near the interface. The localization of the light field matches the thinness of the amorphous silicon layer, so that the effect of light is concentrated at the interface.

[0034] Example 3 On the basis of Example 2, in step 2, an island-shaped transparent conductive oxide particle layer is prepared on both the front and back sides; in step 3, a light treatment is performed on both the front and back sides; and in step 4, a transparent conductive oxide layer is prepared on both the front and back sides. The island-shaped transparent conductive oxide particle layer and the light treatment are simultaneously used on the front and back sides, and the light field is localized on both sides in the interface region of the amorphous silicon layer, thereby increasing the interface light energy density and reducing carrier recombination.

[0035] Preferably, in step 2, before preparing the island-shaped transparent conductive oxide particle layer, the performance of the island-shaped transparent conductive oxide particle layer and the overall photoelectric performance of the silicon heterojunction solar cell are optimized by laser etching the amorphous silicon layer. Laser etching forms a microscopic rough structure or a periodic array on the surface of amorphous silicon, thereby enhancing the adhesion, uniformity and light scattering ability of the particle layer, and optimizing the interface light field distribution and carrier transmission efficiency. The parameter range of laser etching includes: laser wavelength of 355 nm (ultraviolet laser) or 1030 nm (femtosecond laser), laser power controlled between 1-10W, scanning speed of 10-100mm / s, and etching depth controlled within 10nm, ensuring that the surface structure can provide particle attachment sites without excessively damaging the integrity of the amorphous silicon thin layer; the periodic array spacing is about 500nm. In addition, a pulsed laser mode can be selected to avoid heat accumulation or surface overheating caused by continuous laser. The microstructure produced by laser etching not only significantly increases the nucleation density of transparent conductive oxide particles and makes the particle distribution more regular, but also enhances the localization effect of the interface light field through synergistic light scattering, focusing more light energy on the interface area between crystalline silicon and amorphous silicon. At the same time, the local high temperature effect of laser etching can promote the optimization of atomic arrangement on the surface of amorphous silicon, reduce the interface defect density, thereby reducing carrier recombination and further improving the photoelectric conversion efficiency.

[0036] In summary, the present invention proposes a method for preparing a silicon heterojunction solar cell, which realizes the localized enhancement of the interface light field by preparing an island-shaped transparent conductive oxide particle layer on the surface of an amorphous silicon layer and combining it with oblique p-polarized light irradiation, thereby significantly improving the light processing effect. The innovation of the present invention lies in the use of light regulation technology to significantly improve the interface light field distribution, effectively improving the photoelectric conversion efficiency of silicon heterojunction solar cells in applications, and providing an efficient and stable solution for the development of photoelectric technology.

[0037] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for preparing a silicon heterojunction solar cell, characterized in that: The steps include: Step 1, preparing an amorphous silicon layer on crystalline silicon; Step 2, preparing an island-shaped transparent conductive oxide particle layer on the surface of the amorphous silicon layer; Step 3, performing light treatment on the island-shaped transparent conductive oxide particle layer, so that light passes through the island-shaped transparent conductive oxide particle layer and is concentrated near the interface between crystalline silicon and amorphous silicon; Step 4: preparing a transparent conductive oxide layer on the island-shaped transparent conductive oxide particle layer.

2. The method for preparing a silicon heterojunction solar cell according to claim 1, characterized in that: Step 1 includes: Step 11, cleaning the n-type single crystal silicon by a wet chemical method; Step 12: Forming a pyramid-shaped light-trapping structure on the surface of n-type single-crystal silicon through a texturing process; Step 13: using plasma enhanced chemical vapor deposition technology to sequentially deposit an intrinsic amorphous silicon film and a p-type amorphous silicon film on the back side of the n-type single crystal silicon; Step 14: Use plasma enhanced chemical vapor deposition technology to sequentially deposit an intrinsic amorphous silicon film and an n-type amorphous silicon film on the front surface of the n-type single crystal silicon.

3. The method for preparing a silicon heterojunction solar cell according to claim 2, characterized in that: In step 13 and step 14, the thickness of the amorphous silicon film is 5 nm to 15 nm, and the thickness of the p-type amorphous silicon film or the n-type amorphous silicon film is 5 nm to 15 nm.

4. The method for preparing a silicon heterojunction solar cell according to claim 3, characterized in that: The material of the island-shaped transparent conductive oxide particle layer is ITO, FTO or SnO2.

5. The method for preparing a silicon heterojunction solar cell according to claim 4, characterized in that: In step 2, the island-shaped transparent conductive oxide particle layer is prepared by sputtering or thermal evaporation.

6. The method for preparing a silicon heterojunction solar cell according to claim 5, characterized in that: The material of the transparent conductive oxide layer is the same as that of the island-shaped transparent conductive oxide particle layer.

7. The method for preparing a silicon heterojunction solar cell according to claim 1, characterized in that: In step 4, the amorphous silicon layer is heated.

8. The method for preparing a silicon heterojunction solar cell according to claim 1, characterized in that: In step 3, light is irradiated at an angle.

9. The method for preparing a silicon heterojunction solar cell according to claim 8, characterized in that: In step 3, the light is p-polarized.

10. The method for preparing a silicon heterojunction solar cell according to any one of claims 1 to 9, characterized in that: In step 2, an island-shaped transparent conductive oxide particle layer is prepared on both the front and back sides; in step 3, a light treatment is performed on both the front and back sides; in step 4, a transparent conductive oxide layer is prepared on both the front and back sides.

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