Etching additives for preparing pyramid-tipped, single crystal silicon and processes for using the same

Abstract

The application discloses a texturing additive for preparing pyramid-tower-tip-connected structure monocrystalline silicon and a use process thereof, and mass percentages of components of the texturing additive are as follows: 0-15% of polyoxyethylene, 1-10% of polypropylene glycol, 1-5% of an organic solvent, 1-12% of an organic acid, and the balance of water. The use process comprises the following steps: 1) preparing the texturing additive, 2) preparing an alkaline texturing solution, and 3) texturing. The application provides the texturing additive for preparing the pyramid-tower-tip-connected structure monocrystalline silicon and the use process thereof, and a monocrystalline silicon wafer after treatment forms a pyramid-tower-tip-connected texturing structure, which is more favorable for combination with silver paste in a later stage and is favorable for metal passivation contact, so that short-circuit current is improved, and photoelectric conversion efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of solar cell production, and particularly relates to a texturing additive for preparing a pyramid tip connected structure monocrystalline silicon and a use process thereof. BACKGROUND

[0002] With the development of social economy and the increasing population, the demand for energy is also increasing, and most of the energy is non-renewable, so we must pay attention to the development of new energy, and practically apply water energy, wind energy, geothermal energy and solar energy. At the present stage of development, solar energy is relatively ideal, and photovoltaic power generation is an important part of direct utilization of solar energy, that is, the process of converting electrical energy by solar cell pieces through absorbing sunlight. The primary focus in the production process of solar cells is the uneven textured surface of the monocrystalline silicon wafer, that is, the texturing of monocrystalline silicon, which uses the principle of light trapping to increase the absorption of sunlight by the silicon wafer. At present, the texturing of monocrystalline silicon for solar cells is a relatively mature process, and the most commonly used method is chemical etching to prepare a monocrystalline silicon textured surface. The textured surface obtained by the current monocrystalline silicon texturing process is a conventional pyramid structure, without considering the matching of the pyramid structure with the subsequent process, thereby limiting the photoelectric conversion efficiency. Therefore, it is necessary to further study the morphology of the textured surface of monocrystalline silicon to achieve matching with the subsequent process and improve the photoelectric conversion efficiency. SUMMARY

[0003] In order to improve the solar photoelectric conversion efficiency, the present application provides a pyramid tip connected structure monocrystalline silicon texturing additive and its application. The additive can be applied to the process of conventional texturing additives, and the pyramid tip connected structure can be obtained without extending the texturing time. This structure is beneficial to the printing of subsequent silver paste and the passivation of metal contact, thereby improving the short-circuit current and ultimately improving the solar photoelectric conversion efficiency.

[0004] To achieve the above-mentioned objectives, the technical scheme adopted by the present application is as follows: a texturing additive for preparing a pyramid tip connected structure monocrystalline silicon, wherein the mass percentage of each component is as follows: 0-15% of polyethylene oxide, 1-10% of polypropylene glycol, 1-5% of an organic solvent, 1-12% of an organic acid, and the balance of water.

[0005] As a preferred embodiment of the above technical scheme, the polyethylene oxide is one or more of PEO-3, PEO-4, PEO-6, and PEO-15.

[0006] As a preferred embodiment of the above technical scheme, the polypropylene glycol is one or more of polypropylene glycol 400, polypropylene glycol 1000, polypropylene glycol 2000, and polypropylene glycol 4000.

[0007] As the preferred technical scheme of the above, the complexing agent is one or more of sodium nitrilotriacetate, sodium ethylenediaminetetraacetate, sodium diethylenetriaminepentaacetate and triethanolamine.

[0008] As the preferred technical scheme of the above, the organic acid is one or more of acetic acid, benzoic acid, oxalic acid, propionic acid and salicylic acid.

[0009] As the preferred technical scheme of the above, the mass percentage of each component is 1.2-2: 5% of polyethylene oxide, 1.5-4.0% of polypropylene glycol, 3.0-5.0% of complexing agent, 1.5-2.0% of organic acid, and the balance is water.

[0010] The use process of the texturing additive for preparing the single crystal silicon with the pyramid tip connected structure includes the following steps:

[0011] 1) Texturing additive preparation: 1.2-2.5% of polyethylene oxide, 1.5-4.0% of polypropylene glycol, 3.0-5.0% of complexing agent, 1.5-2.0% of organic acid and the balance of water are mixed to prepare a single crystal silicon texturing additive;

[0012] 2) Preparation of alkaline texturing solution: the additive prepared in step 1) is added to an alkaline solution and mixed uniformly, wherein the mass ratio of the texturing additive to the alkaline solution is 1-6:100; the alkaline solution is a 0.1-3wt% aqueous solution of sodium hydroxide or potassium hydroxide;

[0013] 3) Texturing: the single crystal silicon wafer is placed in the alkaline texturing solution prepared in step 2) for texturing, the texturing time is 300-500s, and the texturing temperature is 75-83℃.

[0014] As the preferred technical scheme of the above,

[0015] The working principle of the texturing additive of the present application is that the polyethylene oxide can be orientedly adsorbed on the silicon wafer to induce the formation of the pyramid tip connected structure; the polypropylene glycol plays a role in decontamination and accelerating the hydrogen produced to separate from the silicon wafer; the addition of the complexing agent mainly complexes the sodium silicate generated to accelerate the separation of the sodium silicate from the silicon surface, thereby assisting the polyethylene oxide to be adsorbed on the silicon wafer, so that the formation of the pyramid tip connected structure is more favorable; the addition of the organic acid is to reduce the viscosity of the sodium silicate generated, and at the same time, it can buffer the mass transfer speed of the alkali in the solution, which is favorable for etching the uniform pyramid tip connected structure.

[0016] The present application provides a texturing additive for preparing the single crystal silicon with the pyramid tip connected structure and a use process thereof, and the single crystal silicon wafer processed forms the pyramid tip connected texturing structure, which is more favorable for the combination with the silver paste in the later process and the metal passivation contact, thereby improving the short circuit current and the photoelectric conversion efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 SEM top view of the pyramids of a silicon wafer after texturing for Example 2

[0018] Figure 2 SEM plan view of the pyramids structure obtained by one texturing of a single crystal silicon for Comparative Example 1

[0019] Figure 3 is a schematic diagram of the structure of the pyramid apexes connected in Example 1

[0020] Figure 4 is a schematic diagram of the structure of the pyramid apexes not connected in Comparative Example 1. DETAILED DESCRIPTION

[0021] The technical solutions of the present application will be described clearly and completely below in conjunction with the drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0022] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected inside two elements. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0023] Example 1

[0024] The specific implementation steps of the single crystal silicon texturing of the present application are as follows:

[0025] 1) Single crystal silicon texturing additive preparation: 2.0% by mass of polyethylene oxide, 3.0% of polypropylene glycol, 3.0% of complexing agent, 1.5% of organic acid and the balance of water are mixed to prepare a single crystal silicon texturing additive;

[0026] The complexing agent is one or more of sodium nitrilotriacetate, sodium ethylenediaminetetraacetate, sodium diethylenetriaminepentaacetate and triethanolamine;

[0027] The organic acid is one or more of acetic acid, benzoic acid, oxalic acid, propionic acid and salicylic acid;

[0028] 2) Preparation of alkaline texturing solution: the additive prepared in step 1) is added to an alkaline solution and mixed uniformly, wherein the mass ratio of the texturing additive to the alkaline solution is 3:100; the alkaline solution is a 3wt% sodium hydroxide aqueous solution.

[0029] 3) Texturing method: the single crystal silicon wafer is put into the alkaline texturing solution prepared in step 2) to perform texturing, and the silicon surface is etched to form a pyramid tip connected structure, the texturing time is 400 s, and the texturing temperature is 80 DEG C.

[0030] Example 2

[0031] The specific implementation steps of the single crystal silicon texturing of the present application are as follows:

[0032] 1) Single crystal silicon texturing additive preparation: polyethylene oxide 5.0%, polypropylene glycol 2.0%, complexing agent 4.0%, organic acid 1.5% and the balance of water are mixed to prepare a single crystal silicon texturing additive;

[0033] The complexing agent is one or more of sodium nitrilotriacetate, sodium ethylenediaminetetraacetate, sodium diethylenetriaminepentaacetate and triethanolamine;

[0034] The organic acid is one or more of acetic acid, benzoic acid, oxalic acid, propionic acid and salicylic acid;

[0035] 2) Preparation of alkaline texturing solution: the additive prepared in step 1) is added to an alkaline solution and mixed uniformly, wherein the mass ratio of the texturing additive to the alkaline solution is 4:100; the alkaline solution is a 3wt% sodium hydroxide aqueous solution.

[0036] 3) Texturing method: the single crystal silicon wafer is put into the alkaline texturing solution prepared in step 2) to perform texturing, and the silicon surface is etched to form a pyramid tip connected structure, the texturing time is 400 s, and the texturing temperature is 80 DEG C.

[0037] Example 3

[0038] The specific implementation steps of the single crystal silicon texturing of the present application are as follows:

[0039] 1) Single crystal silicon texturing additive preparation: polyethylene oxide 5.0%, polypropylene glycol 2.0%, complexing agent 4.0%, organic acid 1.5% and the balance of water are mixed to prepare a single crystal silicon texturing additive;

[0040] The complexing agent is one or more of sodium nitrilotriacetate, sodium ethylenediaminetetraacetate, sodium diethylenetriaminepentaacetate and triethanolamine;

[0041] The organic acid is one or more of acetic acid, benzoic acid, oxalic acid, propionic acid and salicylic acid;

[0042] 2) Preparation of alkaline texturing solution: the additive prepared in step 1) is added to an alkaline solution and mixed uniformly, wherein the mass ratio of the texturing additive to the alkaline solution is 4:100; the alkaline solution is a 3wt% sodium hydroxide aqueous solution.

[0043] 3) Texturing method: put the single crystal silicon wafer into the alkaline texturing solution prepared in step 2) for texturing, etch the silicon surface to form a pyramid tip connected structure, the texturing time is 420 s, and the texturing temperature is 82℃.

[0044] Comparative Example 1

[0045] A single crystal silicon texturing additive and a one-time texturing process, comprising the following steps:

[0046] (1) Preparation of additive: directly use the "K02(T30D)" single crystal silicon texturing additive produced by Jiaxing Xiaocheng Photovoltaic Technology Co., Ltd.;

[0047] (2) Preparation of texturing solution: add the additive of step (1) into the alkaline solution and mix uniformly to prepare the texturing solution; the mass ratio of the additive to the alkaline solution is 0.6:100; the alkaline solution is a 1.2wt% sodium hydroxide aqueous solution;

[0048] (3) immerse the single crystal silicon wafer into the texturing solution prepared in step (2) for one-time texturing, the texturing temperature of one-time texturing is 82℃, and the texturing time of one-time texturing is 400 s.

[0049] The single crystal silicon prepared in Example 2 and Comparative Example 1 is subjected to scanning electron microscope analysis, and the test results are shown in Figure 1 and 2 It can be seen from Figure 1 that the tips of some adjacent pyramids form a tip connected structure. However, the single crystal silicon treated with the original single crystal silicon texturing additive of the applicant does not have a structure in which the tips of adjacent pyramids are connected.

[0050] The single crystal silicon prepared in Example 2 and Comparative Example 1 is subjected to the same process to complete the subsequent processing steps, and the single crystal silicon is subjected to photoelectric conversion efficiency test, and the test results are shown in the following table:

[0051] Photoelectric conversion efficiency Open voltage Short circuit current Filling Example 2 23.02％ 0.6894 13.65 80.81 Comparative Example 1 23.00％ 0.6893 13.63 80.82

[0052] As can be seen from the above table, the photoelectric conversion efficiency of the single crystal silicon wafer obtained by using the texturing additive and the process thereof is obviously improved. This is because the pyramid tip connected texturing structure is more conducive to the printing of the subsequent silver paste and the metal passivation contact, thereby improving the short circuit current and ultimately improving the solar photoelectric conversion efficiency.

[0053] It is worth mentioning that the technical features such as scanning electron microscope involved in the present patent application should be regarded as prior art, the specific structure, working principle and possible control mode and spatial arrangement mode of these technical features can be selected by using the conventional selection in the field, and should not be regarded as the invention point of the present patent, and the present patent will not be further expanded and described in detail.

[0054] The preferred embodiments of the present application are described in detail above, it should be understood that those skilled in the art can make many modifications and changes without creative labor according to the concept of the present application, therefore, any technical solution obtained by logical analysis, reasoning or limited experiment based on the prior art according to the concept of the present application should be within the protection scope determined by the claims.

Claims

1. A texturing additive for preparing single-crystal silicon with interconnected pyramid apex structures, characterized in that, The mass percentage of each component is as follows: 2-15% polyethylene oxide, 1-10% polypropylene glycol, 3.0-5.0% complexing agent, 1-12% organic acid, and the balance water.

2. The texturing additive for preparing single-crystal silicon with interconnected pyramid apex structures as described in claim 1, characterized in that, The polyethylene oxide is one or more of PEO-3, PEO-4, PEO-6, and PEO-15.

3. The texturing additive for preparing single-crystal silicon with interconnected pyramid apex structures as described in claim 1, characterized in that, The polypropylene glycol is one or more of polypropylene glycol 400, polypropylene glycol 1000, polypropylene glycol 2000, and polypropylene glycol 4000.

4. The texturing additive for preparing single-crystal silicon with interconnected pyramid apex structures as described in claim 1, characterized in that, The complexing agent is one or more of sodium triacetate, sodium ethylenediaminetetraacetate, sodium diethylenetriaminepentacarboxylate, and triethanolamine.

5. The texturing additive for preparing single-crystal silicon with interconnected pyramid apex structures as described in claim 4, characterized in that, The organic acid is one or more of acetic acid, benzoic acid, oxalic acid, propionic acid, and salicylic acid.

6. The texturing additive for preparing a pyramid-shaped, interconnected structure of single-crystal silicon as described in any one of claims 2-5, characterized in that, The mass percentage of each component is 2-2.5% polyethylene oxide, 1.5-4.0% polypropylene glycol, 3.0-5.0% complexing agent, 1.5-2.0% organic acid, and the balance is water.

7. The process for using the texturing additive for preparing a pyramid-shaped, interconnected single-crystal silicon structure as described in claim 6, characterized in that... Includes the following steps: 1) Formulation of texturing additive: Mix 2-2.5% polyethylene oxide, 1.5-4.0% polypropylene glycol, 3.0-5.0% complexing agent, 1.5-2.0% organic acid and the balance water to form a monocrystalline silicon texturing additive. 2) Preparation of alkaline texturing solution: Add the additive prepared in step 1) to the alkaline solution and mix evenly. The mass ratio of texturing additive to alkaline solution is 1-6:

100. The alkaline solution is an aqueous solution of sodium hydroxide or potassium hydroxide of 0.1-3 wt%. 3) Texturing: The monocrystalline silicon wafer is placed in the alkaline texturing solution obtained in step 2) for texturing. The texturing time is 300-500s and the texturing temperature is 75-83℃.

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