Preparation process of aluminum oxide film-containing battery piece and UV (ultraviolet) solar battery of aluminum oxide film-containing battery piece

Abstract

The invention relates to the technical field of solar cells, in particular to a preparation process of a cell containing an aluminum oxide film and a UV solar cell thereof, and the process comprises the following steps: S1, placing a silicon substrate in a reaction chamber in an atomic layer deposition machine; s2, O3 is introduced into the reaction chamber, and an initial silicon oxide interface layer is formed on the surface of the silicon substrate; s3, purging the surface of the silicon substrate by adopting nitrogen, purging O3 out of the cavity, and circularly purging; s4, TMA is introduced into the reaction chamber, and the TMA reacts with O3 attached to the surface of the battery piece to produce aluminum oxide; s5, nitrogen is adopted to purge the surface of the silicon substrate, and purging is carried out circularly; s6, O3 is introduced into the reaction chamber and reacts with redundant TMA attached to the surface of the silicon substrate to generate a second layer of aluminum oxide; s7, nitrogen is adopted to purge the surface of the silicon substrate, and circulating purging is carried out; and S8, repeating the steps S2 to S5 to prepare the aluminum oxide-containing thin film battery piece. According to the process, introduction of H < + > is reduced, and the interface defect density is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and particularly to a preparation process of a cell sheet with an aluminum oxide thin film and a UV solar cell thereof. Background Art

[0002] In today's photovoltaic industry, as a highly efficient solar cell technology, Topcon cells have been widely used. However, currently, Topcon cells face a severe technical problem, namely the phenomenon of UV potential-induced degradation. This phenomenon causes the power generation of the power station to continuously decline after it is built and put into use. By testing the defective components withdrawn from the power station, it is found that the root cause lies in the passivation failure of the front passivation interface layer, specifically manifested as the damage of the aluminum oxide layer.

[0003] The performance stability of solar cells is crucial for the long-term efficient operation of power stations. With the rapid development of the photovoltaic industry, improving the anti-degradation ability of cells has become one of the key research directions. For Topcon cells, the existing general improvement solution is to increase the thickness of aluminum oxide to slow down the damage effect of ultraviolet irradiation on aluminum oxide. Currently, the existing aluminum oxide process mainly generates by reacting water with TMA, and a large amount of H + will be generated during the reaction process. These H + accumulate in the silicon wafer interface layer and inside the aluminum oxide, thereby passivating the surface of the silicon wafer. However, in an environment of ultraviolet irradiation, the Si-H bond will break, causing H+ to escape, ultimately leading to passivation failure and further resulting in the problem of power generation decline of Topcon cells. This not only affects the power generation efficiency and economic benefits of the power station, but also restricts the further popularization and application of Topcon cell technology. Therefore, it is urgent to develop a new technical solution to solve this problem in order to improve the stability and reliability of Topcon cells. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a preparation process of a cell sheet with an aluminum oxide thin film and a UV solar cell thereof.

[0005] In a first aspect, the present invention provides a preparation process of a cell sheet with an aluminum oxide thin film, including the following steps:

[0006] S1. Place the silicon substrate in the reaction chamber of an atomic layer deposition machine.

[0007] S2. Introduce O 3 into the reaction chamber to form an initial silicon oxide interface layer on the surface of the silicon substrate.

[0008] S3. Purge the surface of the silicon substrate with nitrogen to purge the excess O 3 out of the chamber, and perform cyclic purging.

[0009] S4. Introduce TMA into the reaction chamber, and TMA reacts with the O previously attached to the surface of the battery cell 3 to produce aluminum oxide;

[0010] S5. Purge the surface of the silicon substrate with nitrogen and perform cyclic purging;

[0011] S6. Introduce O 3 into the reaction chamber to react with the excess TMA attached to the surface of the silicon substrate to form a second layer of aluminum oxide;

[0012] S7. Purge the surface of the silicon substrate with nitrogen and perform cyclic purging;

[0013] S8. Repeat steps S2 to S5 to obtain an aluminum oxide thin film, that is, a battery cell containing an aluminum oxide thin film is prepared. In the present invention, in step S1, the temperature of the reaction chamber is 250 ± 5 °C;

[0014] In steps S2 and S4, the internal cavity pressure is maintained at 0.4 - 1 mbar to produce a uniform thin film;

[0015] In step S8, the number of cycles is 30 - 35 times to form an aluminum oxide thin film with a gradient H + distribution structure.

[0016] In step S2, the oxygen vacancy concentration of the initial aluminum oxide interface layer ≤ 5×10 16 cm -3 ;

[0017] In step S4, after the pulse, apply a radio frequency bias voltage with a frequency of 13.56 MHz and a power of 20 W to make the Al 3+ ion implantation depth reach 2 - 3 nm;

[0018] Preferably, in step S2, the pulse conditions are: pulse time 8 s, process flow rate 20 sccm.

[0019] Preferably, in step S3, the purging time is 16 s.

[0020] Preferably, in step S4, the pulse conditions are: pulse time 6 s, process flow rate 30 sccm.

[0021] Preferably, in step S5, the purging time is 12 s.

[0022] Preferably, in step S6, the pulse conditions are: pulse time 7 s, process flow rate 30 scm.

[0023] Preferably, in step S7, the purge time is 14 s. In step S7, temperature-variable purging is performed. The temperature is maintained at 180 °C for the first 7 s, and then increased to 220 °C in the next 7 s. Nitrogen is introduced during the heating stage at a flow rate of 5 sccm to form an Al-O-N transition layer.

[0024] Preferably, the thickness of the silicon substrate is 130 - 140 μm.

[0025] Preferably, in step S8, the thickness of the alumina thin film is 5 - 6 nm.

[0026] In a second aspect, the present invention provides a UV solar cell, including a cell prepared by using the preparation process of the cell with an alumina thin film as described in the first aspect.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1. In the present invention, an alumina thin film is formed by the reaction of ozone and trimethylaluminum, avoiding the use of water as an oxygen source and reducing the introduction of H + , thereby reducing the interfacial defect density. At the same time, Si-O bonds are used instead of traditional Si-H bonds for interface passivation. Si-O bonds have higher bond energy and chemical stability and can maintain a longer service life under ultraviolet (UV) irradiation, significantly improving the durability of the passivation effect.

[0029] 2. In the present invention, through atomic layer deposition technology, combined with precise pulse time and process flow control, a uniform and dense alumina thin film can be formed on the surface of the silicon substrate. The formation of the initial alumina interface layer and the dense capping layer effectively reduces the pinholes and defects in the thin film, improving the insulation performance and barrier performance of the thin film.

[0030] 3. In the present invention, ozone is used as the oxygen source, avoiding the H + pollution problem caused by the use of water in traditional processes, and the process is more environmentally friendly. The nitrogen purge step effectively removes reaction by-products, reduces impurity residues, and further improves the purity of the thin film.

[0031] 4. The cell with an alumina thin film prepared by the present invention has excellent UV resistance, can effectively reduce the damage of UV irradiation to the passivation layer, extend the service life of the solar cell, and the stability of Si-O bonds significantly improves the performance of the cell in a UV environment, making it have a wide application prospect in the field of high-efficiency UV solar cells. Detailed Embodiments

[0033] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the protection scope of the present invention.

[0034] Embodiment 1

[0035] This embodiment provides a preparation process for a battery cell containing an alumina thin film, including the following steps:

[0036] S1. Place the silicon substrate in the reaction chamber of an atomic layer deposition tool, and the temperature of the reaction chamber is 185°C; the thickness of the silicon substrate is 135μm nm;

[0037] S2. Introduce O3 into the reaction chamber, keep the internal cavity pressure at 0.5 mbar, pulse, and form an initial alumina interface layer on the surface of the silicon substrate. The oxygen vacancy concentration of the initial alumina interface layer ≤ 5×1016 cm -3 ; The pulse conditions are: pulse time 8 s, process flow rate 20 sccm;

[0038] S3. Purge the surface of the silicon substrate with nitrogen to purge the excess O 3 out of the cavity, circulate the purge, the purge time is 16 s, the purge pressure linearly decreases from 5 Torr to 1 Torr, and the purge frequency is 0.5 Hz;

[0039] S4. Introduce TMA into the reaction chamber, and TMA reacts with the previously attached O on the surface of the battery cell 3 to produce alumina, keep the internal cavity pressure at 0.5 mbar, pulse; the pulse conditions are: pulse time 6 s, process flow rate 30 sccm;

[0040] S5. Purge the surface of the silicon substrate with nitrogen, circulate the purge, the purge time is 12 s, and the purge pressure linearly decreases from 5 Torr to 1 Torr;

[0041] S6. Introduce O3 into the reaction chamber, react with the excess TMA attached to the surface of the silicon substrate to produce the second layer of alumina, pulse, and the pulse conditions are: pulse time 7 s, process flow rate 30 scm, and form a dense capping layer on the surface of the silicon substrate;

[0042] S7. Purge the surface of the silicon substrate with nitrogen, circulate the purge, the purge time is 14 s, and purge the previous excess precursors out of the cavity to avoid the generation of CVD by-products;

[0043] S8. Repeat steps S2 to S5, the number of cycles is 30 times, and form a gradient H +An alumina thin film with a distributed structure, and the thickness of the alumina thin film is 6 nm.

[0044] This embodiment provides a UV solar cell, including a cell prepared by the preparation process of the cell sheet with the alumina thin film as described above.

[0045] Example 2

[0046] Compared with Example 1, the thickness of the silicon substrate is 130 μm, O 3 The pulse time is shortened to 6 s, purged for 12 s, and the total number of cycles is 35 times. The remaining steps are the same, and the thickness of the prepared alumina thin film is 5 nm.

[0047] Comparative Example 1

[0048] Compared with Example 1, O 3 is replaced by H 2 O, the pulse time is 6.5 s, the purge time is 11 s, the process flow rate is 20 sccm, and the number of cycles is 30 times. The remaining steps are the same.

[0049] Comparative Example 2

[0050] Compared with Example 1, step S2 is not performed, and TMA / O 3 is deposited by cycling.

[0051] Perform passivation performance testing, stability testing, film layer densification, and chemical bond analysis testing on the cell sheets prepared in Example 1, Example 2, Comparative Example 1, and Comparative Example 2. The test results are shown in Table 1.

[0052] Table 1

[0053] Experimental group Initial cell efficiency UV attenuation rate Interface bond type Film layer defect Example 1 26.01％ 0.95％ Si-0 None Example 2 26.01％ 1.2％ Si-0 None Comparative example 1 26.00％ 2.4％ Si-H Microcrack Comparative example 2 26.00％ 1.8％ Mixed bond Pinhole

[0054] The test results show that:

[0055] The test results show that:

[0056] Compared Example 1 with Comparative Example 1, in Comparative Example 1, the H 2 introduced by H + forms an Si-H bond with the silicon substrate, and its bond energy (299 kJ / mol) is much lower than that of the Si-O bond (452 kJ / mol). The UV photon energy is sufficient to break the Si-H bond, resulting in an increase in recombination centers and a sharp drop in efficiency; H 2 The reaction by-products of O (such as -OH) are released during annealing, generating microcracks and accelerating the failure of the passivation layer.

[0057] Compared with Comparative Example 2, in Comparative Example 2, no Si-O interface layer was formed, and the direct deposition of TMA led to insufficient Al-Si bonding and a high interface state density; there was a lack of initial oxide layer densification, the subsequent film growth was uneven, UV light penetrated the defect area to trigger bulk recombination, and O 3 Reducing the pulse time may reduce the effect of repairing interface oxygen vacancies, but through gradient H + Still maintain 93% stability. In Example 1, through O 3 / TMA co-deposition, gradient H + Engineering and Al-O-N transition layer design achieved high-stability Si-O interface passivation, and the efficiency decay rate was lower than that of the traditional H 2 O process, extending the service life of the component.

[0058] The above further describes the present invention with the aid of specific embodiments. However, it should be understood that this specific description should not be construed as limiting the essence and scope of the present invention. Various modifications made by those of ordinary skill in the art to the above embodiments after reading this specification all fall within the scope protected by the present invention.

Claims

1. A process for preparing a thin film battery cell containing aluminum oxide, characterized in that: The following steps are involved: S1, placing a silicon substrate in a reaction chamber in an atomic layer deposition machine; S2, introducing O3 into the reaction chamber to form an initial silicon oxide interface layer on the surface of the silicon substrate; S3, using nitrogen to purge the surface of the silicon substrate to purge excess O3 out of the cavity, and circulate the purge; S4, TMA is introduced into the reaction chamber, and TMA reacts with O3 previously attached to the surface of the battery cell to produce aluminum oxide; S5, using nitrogen to purge the surface of the silicon substrate, and circulate the purge; S6, introducing O3 into the reaction chamber to react with excess TMA attached to the surface of the silicon substrate to form a second layer of aluminum oxide; S7, using nitrogen to purge the surface of the silicon substrate, and circulate the purge; S8. Repeat steps S2 to S5 to obtain an aluminum oxide film, that is, to obtain an aluminum oxide film-containing battery cell.

2. The process for preparing a thin film battery cell containing aluminum oxide according to claim 1, characterized in that: In step S2, the pulse conditions are: pulse time 8s, process flow rate 20sccm.

3. The process for preparing a thin film battery cell containing aluminum oxide according to claim 1, characterized in that: In step S3, the purge time is 16 seconds.

4. The process for preparing a thin film battery cell containing aluminum oxide according to claim 1, characterized in that: In step S4, the pulse conditions are: pulse time 6 s, process flow rate 30 sccm.

5. The process for preparing a thin film battery cell containing aluminum oxide according to claim 1, characterized in that: In step S5, the purge time is 12 seconds.

6. The process for preparing a thin film battery cell containing aluminum oxide according to claim 1, characterized in that: In step S6, the pulse conditions are: pulse time 7s, process flow rate 30scm.

7. The process for preparing a thin film battery cell containing aluminum oxide according to claim 1, characterized in that: In step S7, the purge time is 14 seconds.

8. The process for preparing a thin film battery cell containing aluminum oxide according to claim 1, characterized in that: The thickness of the silicon substrate is 130-140 μm.

9. The process for preparing a thin film battery cell containing aluminum oxide according to claim 1, characterized in that: In the step S8, the thickness of the aluminum oxide film is 5-6 nm.

10. A UV solar cell, characterized in that: It comprises a battery cell produced by the preparation process of an aluminum oxide thin film battery cell as described in any one of claims 1 to 9.