A perovskite solar cell oxide layer and an optimization method thereof

Abstract

The application provides a PERC solar cell oxidation layer and an optimization method thereof. The optimization method comprises the following steps in sequence: boat loading, constant voltage, leakage detection, constant temperature, oxidation, nitrogen filling and boat unloading. The constant voltage comprises the following steps in sequence: first constant voltage, second constant voltage and third constant voltage. The oxidation comprises the following steps in sequence: first oxidation and second oxidation. The oxidation is accompanied by the input of nitrogen and oxygen, and the flow ratio of nitrogen to oxygen is 1:(2-4). The temperature in the furnace gradually decreases from the furnace mouth to the furnace tail during the process from the constant voltage to the nitrogen filling. The optimization method provided by the application improves the LID resistance effect and conversion efficiency of the cell, and improves the production capacity and processing efficiency.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solar cells, and relates to a PERC solar cell, in particular to an oxidation layer of a PERC solar cell and an optimization method thereof. BACKGROUND

[0002] Light Induced Degradation (LID) refers to a power degradation phenomenon caused by photovoltaic cells and components in the process of illumination. In recent years, the most cost-effective efficiency improvement means for crystalline silicon solar cells is PERC technology, and the PERC technology has higher compatibility with conventional single and polycrystalline cell production lines, the cost of the old production line is low, and the efficiency improvement effect is relatively significant. The successful application of the PERC technology greatly enhances the competitiveness of P-type crystalline silicon and delays the marketization process of N-type crystalline silicon.

[0003] The PERC (Passivated Emitter and Rear Cell) cell technology is an innovative technology for P-type solar cells. The conversion efficiency of the cell sheet is improved basically from the medium film passivation of the back surface, which can greatly reduce the back surface recombination velocity and improve the light reflection of the back surface. The technical process route is etching→diffusion→SE front laser grooving→thermal oxidation→PSG removal→alkali stripping→annealing→ALD+back film plating→front film plating→back laser grooving→screen printing→LID annealing. In the solar cell industry, the LID attenuation level generally continues at about 0.5%, which causes great loss to the conversion efficiency of the cell sheet, so it is imminent to add an oxidation process after the alkali stripping process to improve the LID resistance of the cell sheet. Later, with the development of the industry, many companies improved the oxidation process, added an annealing furnace, and combined oxidation and annealing to improve the conversion efficiency of the cell sheet.

[0004] CN 113421944A discloses an oxidation annealing process for improving the conversion efficiency of crystalline silicon solar cells, which includes an oxidation process temperature of 680-760 DEG C, while nitrogen gas 5000-10000 sccm and oxygen gas 500-1000 sccm are introduced, for 300-600 s; the oxidation process temperature is 650-700 DEG C, while nitrogen gas 20000-30000 sccm and oxygen gas 3000-6000 sccm are introduced, for 600-1000 s; the process temperature of the first step-down annealing is 600-650 DEG C, while nitrogen gas 20000-30000 sccm is introduced, for 1200-2000 s; the process temperature of the second step-down annealing is 550-600 DEG C, while nitrogen gas 20000-30000 sccm is introduced, for 1200-1800 s. Although the oxidation annealing process of the present application achieves the purpose of compensating for internal defects of the silicon wafer, improving the minority carrier lifetime and improving the conversion efficiency, the oxygen flow used in the step-down annealing process is low, and the time consumption of each stage is long, which seriously affects the production capacity, and the LID reduction is not reflected.

[0005] Therefore, how to provide an optimization method for the oxidation layer of a PERC solar cell to improve the LID resistance effect and conversion efficiency of the cell, and to improve the production capacity and processing efficiency, has become an urgent problem to be solved by those skilled in the art. SUMMARY

[0006] The present application provides a PERC solar cell oxidation layer and an optimization method thereof, which improves the LID resistance effect and conversion efficiency of the cell, and improves the production capacity and processing efficiency.

[0007] To achieve the object of the present application, the following technical solutions are adopted:

[0008] In a first aspect, the present application provides an optimization method for the oxidation layer of a PERC solar cell, which includes in-order progress of boat loading, constant pressure, leak detection, constant temperature, oxidation, nitrogen filling and boat unloading.

[0009] The constant pressure includes in-order progress of first constant pressure, second constant pressure and third constant pressure.

[0010] The oxidation includes in-order progress of first oxidation and second oxidation.

[0011] The oxidation is accompanied by the introduction of nitrogen and oxygen, and the nitrogen-oxygen flow ratio is 1:(2-4), for example, it can be 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3, 1:3.2, 1:3.4, 1:3.6, 1:3.8 or 1:4, but it is not limited to the listed values, and other values not listed in this range are also applicable.

[0012] The furnace temperature gradually decreases from the furnace mouth to the furnace tail during the constant pressure to nitrogen filling process.

[0013] The present application realizes the accurate adjustment of the thickness of the silicon wafer surface oxide layer by optimizing the specific process of the oxide layer, especially limiting the nitrogen oxygen ratio in the oxidation process within a reasonable range and controlling the furnace temperature to gradually decrease from the furnace mouth to the furnace tail during the constant pressure to nitrogen filling process, improves the uniformity and density of the oxide layer, improves the LID resistance effect and conversion efficiency of the battery, and improves the production capacity and processing efficiency.

[0014] In the present application, the nitrogen filling is specifically furnace door nitrogen filling, not internal nitrogen filling.

[0015] Preferably, the furnace mouth temperature is 5-10℃ higher than the furnace temperature during the constant pressure to nitrogen filling process, for example, it can be 5℃, 5.5℃, 6℃, 6.5℃, 7℃, 7.5℃, 8℃, 8.5℃, 9℃, 9.5℃ or 10℃, but not limited to the listed values, other values not listed in this range are also applicable.

[0016] Preferably, the furnace temperature is 5-10℃ higher than the furnace tail temperature during the constant pressure to nitrogen filling process, for example, it can be 5℃, 5.5℃, 6℃, 6.5℃, 7℃, 7.5℃, 8℃, 8.5℃, 9℃, 9.5℃ or 10℃, but not limited to the listed values, other values not listed in this range are also applicable.

[0017] Preferably, the temperature of the boat-in and boat-out is 20-30℃ higher than the temperature of each intermediate step, for example, it can be 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃ or 30℃, but not limited to the listed values, other values not listed in this range are also applicable.

[0018] The present application sets the temperature of the boat-in and boat-out to be 20-30℃ higher than the temperature of each intermediate step, so that the temperature of all temperature zones before oxidation can reach the set value.

[0019] Preferably, the temperature of the boat-in is 600-800℃, for example, it can be 600℃, 620℃, 640℃, 660℃, 680℃, 700℃, 720℃, 740℃, 760℃, 780℃ or 800℃, but not limited to the listed values, other values not listed in this range are also applicable.

[0020] Preferably, the small nitrogen flow rate into the boat is 400-600 seem, for example, it can be 400 seem, 420 seem, 440 seem, 460 seem, 480 seem, 500 seem, 520 seem, 540 seem, 560 seem, 580 seem or 600 seem, but not only limited to the listed values, other values not listed in the range are also applicable.

[0021] Preferably, the large nitrogen flow rate into the boat is 2000-4000 seem, for example, it can be 2000 seem, 2200 seem, 2400 seem, 2600 seem, 2800 seem, 3000 seem, 3200 seem, 3400 seem, 3600 seem, 3800 seem or 4000 seem, but not only limited to the listed values, other values not listed in the range are also applicable.

[0022] Preferably, the time of the first constant pressure is 100-300 s, for example, it can be 100 s, 120 s, 140 s, 160 s, 180 s, 200 s, 220 s, 240 s, 260 s, 280 s or 300 s, but not only limited to the listed values, other values not listed in the range are also applicable.

[0023] Preferably, the pressure of the first constant pressure is 50-150 mbar, for example, it can be 50 mbar, 60 mbar, 70 mbar, 80 mbar, 90 mbar, 100 mbar, 110 mbar, 120 mbar, 130 mbar, 140 mbar or 150 mbar, but not only limited to the listed values, other values not listed in the range are also applicable.

[0024] Preferably, the temperature of the first constant pressure is 650-700 °C, for example, it can be 650 °C, 655 °C, 660 °C, 665 °C, 670 °C, 675 °C, 680 °C, 685 °C, 690 °C, 695 °C or 700 °C, but not only limited to the listed values, other values not listed in the range are also applicable.

[0025] Preferably, the small nitrogen flow rate of the first constant pressure is 100-300 seem, for example, it can be 100 seem, 120 seem, 140 seem, 160 seem, 180 seem, 200 seem, 220 seem, 240 seem, 260 seem, 280 seem or 300 seem, but not only limited to the listed values, other values not listed in the range are also applicable.

[0026] Preferably, the time of the second constant pressure is 200-300 s, for example, it can be 200 s, 210 s, 220 s, 230 s, 240 s, 250 s, 260 s, 270 s, 280 s, 290 s or 300 s, but not only limited to the listed values, other values not listed in the range are also applicable.

[0027] Preferably, the pressure of the second constant pressure is 600-800 mbar, for example, it can be 600 mbar, 620 mbar, 640 mbar, 660 mbar, 680 mbar, 700 mbar, 720 mbar, 740 mbar, 760 mbar, 780 mbar or 800 mbar, but not only limited to the listed values, other values not listed in the range are also applicable.

[0028] Preferably, the temperature of the second constant pressure is 650-700℃, for example, it can be 650℃, 655℃, 660℃, 665℃, 670℃, 675℃, 680℃, 685℃, 690℃, 695℃ or 700℃, but not only limited to the listed values, other values not listed in the range are also applicable.

[0029] Preferably, the small nitrogen flow of the second constant pressure is 100-300 sccm, for example, it can be 100 sccm, 120 sccm, 140 sccm, 160 sccm, 180 sccm, 200 sccm, 220 sccm, 240 sccm, 260 sccm, 280 sccm or 300 sccm, but not only limited to the listed values, other values not listed in the range are also applicable.

[0030] Preferably, the large nitrogen flow of the second constant pressure is 10000-20000 sccm, for example, it can be 10000 sccm, 11000 sccm, 12000 sccm, 13000 sccm, 14000 sccm, 15000 sccm, 16000 sccm, 17000 sccm, 18000 sccm, 19000 sccm or 20000 sccm, but not only limited to the listed values, other values not listed in the range are also applicable.

[0031] Preferably, the time of the third constant pressure is 100-200 s, for example, it can be 100 s, 110 s, 120 s, 130 s, 140 s, 150 s, 160 s, 170 s, 180 s, 190 s or 200 s, but not only limited to the listed values, other values not listed in the range are also applicable.

[0032] Preferably, the pressure of the third constant pressure is 50-150 mbar, for example, it can be 50 mbar, 60 mbar, 70 mbar, 80 mbar, 90 mbar, 100 mbar, 110 mbar, 120 mbar, 130 mbar, 140 mbar or 150 mbar, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0033] Preferably, the temperature of the third constant pressure is 650-700℃, for example, it can be 650℃, 655℃, 660℃, 665℃, 670℃, 675℃, 680℃, 685℃, 690℃, 695℃ or 700℃, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0034] Preferably, the nitrogen flow of the third constant pressure is 100-300 sccm, for example, it can be 100 sccm, 120 sccm, 140 sccm, 160 sccm, 180 sccm, 200 sccm, 220 sccm, 240 sccm, 260 sccm, 280 sccm or 300 sccm, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0035] Preferably, the time of the leak detection is 30-90 s, for example, it can be 30 s, 35 s, 40 s, 45 s, 50 s, 55 s, 60 s, 65 s, 70 s, 75 s, 80 s, 85 s or 90 s, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0036] Preferably, the pressure of the leak detection is 950-1050 mbar, for example, it can be 950 mbar, 960 mbar, 970 mbar, 980 mbar, 990 mbar, 1000 mbar, 1010 mbar, 1020 mbar, 1030 mbar, 1040 mbar or 1050 mbar, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0037] Preferably, the temperature of the leak detection is 650-700℃, for example, it can be 650℃, 655℃, 660℃, 665℃, 670℃, 675℃, 680℃, 685℃, 690℃, 695℃ or 700℃, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0038] Preferably, the temperature of the isothermal step is in the range of 650-700 °C, for example it can be 650 °C, 655 °C, 660 °C, 665 °C, 670 °C, 675 °C, 680 °C, 685 °C, 690 °C, 695 °C or 700 °C, but is not limited to the listed values, other non-listed values within this range are equally applicable.

[0039] Preferably, the pressure of the isothermal step is in the range of 50-150 mbar, for example it can be 50 mbar, 60 mbar, 70 mbar, 80 mbar, 90 mbar, 100 mbar, 110 mbar, 120 mbar, 130 mbar, 140 mbar or 150 mbar, but is not limited to the listed values, other non-listed values within this range are equally applicable.

[0040] Preferably, the temperature of the isothermal step is in the range of 650-700 °C, for example it can be 650 °C, 655 °C, 660 °C, 665 °C, 670 °C, 675 °C, 680 °C, 685 °C, 690 °C, 695 °C or 700 °C, but is not limited to the listed values, other non-listed values within this range are equally applicable.

[0041] Preferably, the nitrogen flow of the isothermal step is in the range of 100-300 seem, for example it can be 100 seem, 120 seem, 140 seem, 160 seem, 180 seem, 200 seem, 220 seem, 240 seem, 260 seem, 280 seem or 300 seem, but is not limited to the listed values, other non-listed values within this range are equally applicable.

[0042] Preferably, the time of the first oxidation step is in the range of 250-350 s, for example it can be 250 s, 260 s, 270 s, 280 s, 290 s, 300 s, 310 s, 320 s, 330 s, 340 s or 350 s, further preferred is in the range of 320-350 s, but is not limited to the listed values, other non-listed values within this range are equally applicable.

[0043] Preferably, the pressure of the first oxidation step is in the range of 50-150 mbar, for example it can be 50 mbar, 60 mbar, 70 mbar, 80 mbar, 90 mbar, 100 mbar, 110 mbar, 120 mbar, 130 mbar, 140 mbar or 150 mbar, but is not limited to the listed values, other non-listed values within this range are equally applicable.

[0044] Preferably, the temperature of the first oxidation is 650-700 °C, for example it can be 650 °C, 655 °C, 660 °C, 665 °C, 670 °C, 675 °C, 680 °C, 685 °C, 690 °C, 695 °C or 700 °C, but not only the listed values, other values not listed within this range are also applicable.

[0045] Preferably, the nitrogen flow of the first oxidation is 2000-4000 seem, for example it can be 2000 seem, 2200 seem, 2400 seem, 2600 seem, 2800 seem, 3000 seem, 3200 seem, 3400 seem, 3600 seem, 3800 seem or 4000 seem, but not only the listed values, other values not listed within this range are also applicable.

[0046] Preferably, the oxygen flow of the first oxidation is 6000-10000 seem, for example it can be 6000 seem, 6500 seem, 7000 seem, 7500 seem, 8000 seem, 8500 seem, 9000 seem, 9500 seem or 10000 seem, but not only the listed values, other values not listed within this range are also applicable.

[0047] Preferably, the time of the second oxidation is 1500-1700 s, for example it can be 1500 s, 1520 s, 1540 s, 1560 s, 1580 s, 1600 s, 1620 s, 1640 s, 1660 s, 1680 s or 1700 s, further preferred 1500-1600 s, but not only the listed values, other values not listed within this range are also applicable.

[0048] Preferably, the pressure of the second oxidation is 50-150 mbar, for example it can be 50 mbar, 60 mbar, 70 mbar, 80 mbar, 90 mbar, 100 mbar, 110 mbar, 120 mbar, 130 mbar, 140 mbar or 150 mbar, but not only the listed values, other values not listed within this range are also applicable.

[0049] Preferably, the temperature of the second oxidation is 650-700 °C, for example it can be 650 °C, 655 °C, 660 °C, 665 °C, 670 °C, 675 °C, 680 °C, 685 °C, 690 °C, 695 °C or 700 °C, but not only the listed values, other values not listed within this range are also applicable.

[0050] Preferably, the second oxidized nitrogen gas flow is in the range of 2000-4000 seem, for example it can be 2000 seem, 2200 seem, 2400 seem, 2600 seem, 2800 seem, 3000 seem, 3200 seem, 3400 seem, 3600 seem, 3800 seem, or 4000 seem, but is not limited to the listed values, other non-listed values within this range are also applicable.

[0051] Preferably, the second oxidized oxygen gas flow is in the range of 6000-10000 seem, for example it can be 6000 seem, 6500 seem, 7000 seem, 7500 seem, 8000 seem, 8500 seem, 9000 seem, 9500 seem, or 10000 seem, but is not limited to the listed values, other non-listed values within this range are also applicable.

[0052] Preferably, the nitrogen filling time is in the range of 100-140 s, for example it can be 100 s, 105 s, 110 s, 115 s, 120 s, 125 s, 130 s, 135 s, or 140 s, but is not limited to the listed values, other non-listed values within this range are also applicable.

[0053] Preferably, the nitrogen filling pressure is in the range of 950-1050 mbar, for example it can be 950 mbar, 960 mbar, 970 mbar, 980 mbar, 990 mbar, 1000 mbar, 1010 mbar, 1020 mbar, 1030 mbar, 1040 mbar, or 1050 mbar, but is not limited to the listed values, other non-listed values within this range are also applicable.

[0054] Preferably, the nitrogen filling temperature is in the range of 650-700 °C, for example it can be 650 °C, 655 °C, 660 °C, 665 °C, 670 °C, 675 °C, 680 °C, 685 °C, 690 °C, 695 °C, or 700 °C, but is not limited to the listed values, other non-listed values within this range are also applicable.

[0055] Preferably, the out-of-boat temperature is in the range of 600-800 °C, for example it can be 600 °C, 620 °C, 640 °C, 660 °C, 680 °C, 700 °C, 720 °C, 740 °C, 760 °C, 780 °C, or 800 °C, but is not limited to the listed values, other non-listed values within this range are also applicable.

[0056] Preferably, the small nitrogen flow rate of the boat-out is 400-600sccm, for example, it can be 400sccm, 420sccm, 440sccm, 460sccm, 480sccm, 500sccm, 520sccm, 540sccm, 560sccm, 580sccm or 600sccm, but not limited to the listed values, other values not listed in the range are also applicable.

[0057] Preferably, the large nitrogen flow rate of the boat-out is 2000-4000sccm, for example, it can be 2000sccm, 2200sccm, 2400sccm, 2600sccm, 2800sccm, 3000sccm, 3200sccm, 3400sccm, 3600sccm, 3800sccm or 4000sccm, but not limited to the listed values, other values not listed in the range are also applicable.

[0058] As a preferred technical solution of the first aspect of the application, the optimization method comprises the following steps:

[0059] (1) Boat-in: temperature is 600-800℃, small nitrogen flow rate is 400-600sccm, and large nitrogen flow rate is 2000-4000sccm;

[0060] (2) First constant pressure: time is 100-300s, pressure is 50-150mbar, temperature is 650-700℃, and small nitrogen flow rate is 100-300sccm;

[0061] (3) Second constant pressure: time is 200-300s, pressure is 600-800mbar, temperature is 650-700℃, small nitrogen flow rate is 100-300sccm, and large nitrogen flow rate is 10000-20000sccm;

[0062] (4) Third constant pressure: time is 100-200s, pressure is 50-150mbar, temperature is 650-700℃, and small nitrogen flow rate is 100-300sccm;

[0063] (5) Leak detection: time is 30-90s, pressure is 950-1050mbar, and temperature is 650-700℃;

[0064] (6) Constant temperature: time is 30-90s, pressure is 50-150mbar, temperature is 650-700℃, and small nitrogen flow rate is 100-300sccm;

[0065] (7) first oxidation: time is 320-350s, pressure is 50-150mbar, temperature is 650-700℃, nitrogen flow is 2000-4000sccm, oxygen flow is 6000-10000sccm, and nitrogen oxygen flow ratio is 1:(2-4);

[0066] (8) second oxidation: time is 1500-1600s, pressure is 50-150mbar, temperature is 650-700℃, nitrogen flow is 2000-4000sccm, oxygen flow is 6000-10000sccm, and nitrogen oxygen flow ratio is 1:(2-4);

[0067] (9) nitrogen filling: time is 100-140s, pressure is 950-1050mbar, temperature is 650-700℃;

[0068] (10) boat out: temperature is 600-800℃, small nitrogen flow is 400-600sccm, and large nitrogen flow is 2000-4000sccm.

[0069] The optimization method is carried out in an annealing furnace, and the temperature in the furnace gradually decreases from the furnace mouth to the furnace tail during the process from constant pressure to nitrogen filling, the temperature at the furnace mouth is 5-10℃ higher than the temperature in the furnace, and the temperature in the furnace is 5-10℃ higher than the temperature at the furnace tail; the temperature of the boat in and out is 20-30℃ higher than the temperature of each step in the middle.

[0070] In the second aspect, the application provides a PERC solar cell oxide layer prepared by the optimization method of the first aspect, wherein the thickness of the PERC solar cell oxide layer is 1.5-1.8nm, for example, can be 1.5nm, 1.55nm, 1.6nm, 1.65nm, 1.7nm, 1.75nm or 1.8nm, but not limited to the listed values, and other values not listed in the range are also applicable.

[0071] In the application, the thickness range of the PERC solar cell oxide layer from the furnace mouth to the furnace tail is ≤0.1nm, for example, can be 0.01nm, 0.02nm, 0.03nm, 0.04nm, 0.05nm, 0.06nm, 0.07nm, 0.08nm, 0.09nm or 0.1nm, but not limited to the listed values, and other values not listed in the range are also applicable.

[0072] Compared with the prior art, the application has the following beneficial effects:

[0073] The present application realizes the accurate adjustment of the thickness of the surface oxide layer of the silicon wafer, improves the uniformity and density of the oxide layer, improves the LID resistance effect and conversion efficiency of the battery, and the highest LID resistance effect can reach 0.46%, the improvement range of the conversion efficiency is 0.02%, the light decay ratio is reduced to 0.11% at the lowest, and the production capacity and processing efficiency are improved. BRIEF DESCRIPTION OF DRAWINGS

[0074] Figure 1 is a comparison chart of PERC solar cells prepared by using the oxide layers obtained from Example 4 and Comparative Example 1 in terms of Eta (efficiency);

[0075] Figure 2 is a comparison chart of PERC solar cells prepared by using the oxide layers obtained from Example 4 and Comparative Example 1 in terms of FF (filling);

[0076] Figure 3 is a comparison chart of PERC solar cells prepared by using the oxide layers obtained from Example 4 and Comparative Example 1 in terms of Voc (open voltage);

[0077] Figure 4 is a comparison chart of PERC solar cells prepared by using the oxide layers obtained from Example 4 and Comparative Example 1 in terms of Isc (short current);

[0078] Figure 5 is a comparison chart of PERC solar cells prepared by using the oxide layers obtained from Example 4 and Comparative Example 1 in terms of Rser (series resistance);

[0079] Figure 6 is a comparison chart of PERC solar cells prepared by using the oxide layers obtained from Example 4 and Comparative Example 1 in terms of Rsh (shunt resistance);

[0080] Figure 7 is a comparison chart of PERC solar cells prepared by using the oxide layers obtained from Example 4 and Comparative Example 1 in terms of Irev2 (leakage current). DETAILED DESCRIPTION

[0081] The technical solutions of the present application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only to help understand the present application, and should not be regarded as specific limitations on the present application.

[0082] Example 1

[0083] The embodiment provides a PERC solar cell oxide layer and an optimization method thereof, and the optimization method comprises starting, opening a furnace door, feeding a boat, closing the furnace door, first constant pressure, second constant pressure, third constant pressure, leak detection, constant temperature, first oxidation, second oxidation, nitrogen filling, opening the furnace door, discharging the boat, closing the furnace door and ending in sequence, and specific conditions of each step are shown in Table 1.

[0084] Table 1

[0085]

[0086]

[0087] Note: In the table, "nitrogen filling" specifically refers to furnace door nitrogen filling, not internal furnace cavity nitrogen filling, so the large nitrogen flow and the small nitrogen flow are 0 in the nitrogen filling link.

[0088] According to statistics, the average thickness of the PERC solar cell oxide layer obtained in the embodiment is 1.51 nm, 1.54 nm and 1.59 nm from the furnace mouth, the furnace center to the furnace tail respectively, and the thickness range is 0.08 nm.

[0089] Embodiment 2

[0090] The embodiment provides a PERC solar cell oxide layer and an optimization method thereof, and the optimization method comprises starting, opening a furnace door, feeding a boat, closing the furnace door, first constant pressure, second constant pressure, third constant pressure, leak detection, constant temperature, first oxidation, second oxidation, nitrogen filling, opening the furnace door, discharging the boat, closing the furnace door and ending in sequence, and specific conditions of each step are shown in Table 2.

[0091] Table 2

[0092]

[0093]

[0094] Note: In the table, "nitrogen filling" specifically refers to furnace door nitrogen filling, not internal furnace cavity nitrogen filling, so the large nitrogen flow and the small nitrogen flow are 0 in the nitrogen filling link.

[0095] According to statistics, the average thickness of the PERC solar cell oxide layer obtained in the embodiment is 1.74 nm, 1.76 nm and 1.79 nm from the furnace mouth, the furnace center to the furnace tail respectively, and the thickness range is 0.05 nm.

[0096] Embodiment 3

[0097] The embodiment provides a PERC solar cell oxide layer and an optimization method thereof, and the optimization method comprises starting, opening a furnace door, feeding a boat, closing the furnace door, first constant pressure, second constant pressure, third constant pressure, leak detection, constant temperature, first oxidation, second oxidation, nitrogen filling, opening the furnace door, discharging the boat, closing the furnace door and ending in sequence, and specific conditions of each step are shown in Table 3.

[0098] Table 3

[0099]

[0100]

[0101] Note: In the table, "nitrogen filling" specifically refers to furnace door nitrogen filling, not internal furnace cavity nitrogen filling, so the large nitrogen flow and the small nitrogen flow are 0 in the nitrogen filling link.

[0102] According to statistics, the average thickness of the PERC solar cell oxide layer obtained in the embodiment is 1.72 nm, 1.74 nm and 1.78 nm from the furnace mouth, the furnace center to the furnace tail respectively, and the thickness range is 0.06 nm.

[0103] Embodiment 4

[0104] The embodiment provides a PERC solar cell oxide layer and an optimization method thereof, and the optimization method comprises starting, opening a furnace door, feeding a boat, closing the furnace door, first constant pressure, second constant pressure, third constant pressure, leak detection, constant temperature, first oxidation, second oxidation, nitrogen filling, opening the furnace door, discharging the boat, closing the furnace door and ending in sequence, and specific conditions of each step are shown in Table 4.

[0105] Table 4

[0106]

[0107]

[0108] Note: In the table, "nitrogen filling" specifically refers to furnace door nitrogen filling, not internal furnace cavity nitrogen filling, so the large nitrogen flow and the small nitrogen flow are 0 in the nitrogen filling link.

[0109] According to statistics, the average thickness of the PERC solar cell oxide layer obtained in the embodiment is 1.72 nm, 1.74 nm and 1.78 nm from the furnace mouth, the furnace center to the furnace tail respectively, and the thickness range is 0.06 nm.

[0110] Embodiment 5

[0111] The embodiment provides a PERC solar cell oxide layer and an optimization method thereof, and the optimization method comprises starting, opening a furnace door, feeding a boat, closing the furnace door, first constant pressure, second constant pressure, third constant pressure, leak detection, constant temperature, first oxidation, second oxidation, nitrogen filling, opening the furnace door, discharging the boat, closing the furnace door and ending which are sequentially performed, and specific conditions of each step operation are shown in Table 5.

[0112] Table 5

[0113]

[0114] Note: In the table, the "nitrogen filling" is specifically furnace door nitrogen filling, not internal furnace cavity nitrogen filling, so the large nitrogen flow and the small nitrogen flow are 0 in the nitrogen filling link.

[0115] According to statistics, the average thickness of the PERC solar cell oxide layer obtained in the embodiment is 1.76 nm, 1.79 nm and 1.85 nm from the furnace mouth, the furnace center to the furnace tail respectively, and the thickness range is 0.09 nm.

[0116] Comparative Example 1

[0117] The comparative example provides a PERC solar cell oxide layer and an optimization method thereof, and the optimization method comprises starting, opening a furnace door, feeding a boat, closing the furnace door, first constant pressure, second constant pressure, third constant pressure, leak detection, constant temperature, first oxidation, second oxidation, nitrogen filling, opening the furnace door, discharging the boat, closing the furnace door and ending which are sequentially performed, and specific conditions of each step operation are shown in Table 6.

[0118] Table 6

[0119]

[0120] Note: In the table, the "nitrogen filling" is specifically furnace door nitrogen filling, not internal furnace cavity nitrogen filling, so the large nitrogen flow and the small nitrogen flow are 0 in the nitrogen filling link.

[0121] According to statistics, the average thickness of the PERC solar cell oxide layer obtained in the comparative example is 1.12 nm, 1.15 nm and 1.34 nm from the furnace mouth, the furnace center to the furnace tail respectively, and the thickness range is 0.22 nm.

[0122] Comparative Example 2

[0123] The comparative example provides a PERC solar cell oxide layer and an optimization method thereof, and the optimization method comprises starting, opening a furnace door, feeding a boat, closing the furnace door, first constant pressure, second constant pressure, third constant pressure, leak detection, constant temperature, first oxidation, second oxidation, nitrogen filling, opening the furnace door, discharging the boat, closing the furnace door and ending which are sequentially performed, and specific conditions of each step operation are shown in Table 7.

[0124] Table 7

[0125]

[0126] Note: "Nitrogen filling" in the table is specifically furnace door nitrogen filling, not internal nitrogen filling, so the large and small nitrogen flow is 0 in the nitrogen filling link.

[0127] According to statistics, the average thickness of the PERC solar cell oxide layer obtained in the example is 1.27 nm, 1.32 nm and 1.35 nm from the furnace mouth, the furnace middle to the furnace tail, respectively, and the thickness range is 0.08 nm.

[0128] Comparative Example 3

[0129] The comparative example provides a PERC solar cell oxide layer and an optimization method thereof, the optimization method comprising sequentially starting, opening the furnace door, putting the boat, closing the furnace door, first constant pressure, second constant pressure, third constant pressure, leak detection, constant temperature, oxidation, nitrogen filling, opening the furnace door, taking out the boat, closing the furnace door and ending, the specific conditions of each step operation are shown in Table 8.

[0130] Table 8

[0131]

[0132]

[0133] Note: "Nitrogen filling" in the table is specifically furnace door nitrogen filling, not internal nitrogen filling, so the large and small nitrogen flow is 0 in the nitrogen filling link.

[0134] According to statistics, the average thickness of the PERC solar cell oxide layer obtained in the example is 1.27 nm, 1.32 nm and 1.35 nm from the furnace mouth, the furnace middle to the furnace tail, respectively, and the thickness range is 0.08 nm.

[0135] The ZW-SSS01 light decay furnace was used to test the light decay under the condition of cumulative irradiance of 2.5 kw.h / m 2 , the light decay ratio of the PERC solar cell oxide layer obtained in examples 1-5 and comparative examples 1-3 is shown in Table 9.

[0136] Table 9

[0137]

[0138] The PERC solar cell oxide layer thickness of the battery piece corresponding to examples 4 and comparative examples 1 was selected respectively, the red sun coating machine was used for coating, and the May printing test sorting integrated machine was used to test the performance of the batch of batteries at 25-30℃, and the related test performance results are shown in Table 10 and Figures 1-7 .

[0139] Table 10

[0140]

[0141]

[0142] Depend on Figures 1-7 It can be seen that, compared with Comparative Example 1, the PERC solar cell prepared using the oxide layer with a thickness of 1.60-1.67 nm obtained in Example 4 has a higher average efficiency Eta by 0.02%, mainly reflected in an increase of 0.8 mV in open-circuit voltage VOC and an increase of 24 mA in short-circuit current Isc. The oxide layer thickness obtained in Example 4 improves the density of the oxide layer on the surface of the cell, resulting in a better passivation effect, significantly reducing surface recombination, fully improving the anti-LID effect of the cell and increasing the conversion efficiency.

[0143] Therefore, this invention optimizes specific processes of the oxide layer, particularly limiting the nitrogen-oxygen ratio within a reasonable range during oxidation, and controlling the furnace temperature to gradually decrease from the furnace mouth to the furnace tail during the constant pressure to nitrogen charging process. This achieves precise adjustment of the oxide layer thickness on the silicon wafer surface, improves the uniformity and density of the oxide layer, and enhances the anti-LID effect and conversion efficiency of the battery. The anti-LID effect can reach up to 0.46%, the conversion efficiency can be improved by 0.02%, and the light decay ratio can be reduced to a minimum of 0.11%. At the same time, it improves production capacity and processing efficiency.

[0144] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for optimizing the oxide layer of a PERC solar cell, characterized in that, The optimization method comprises in turn boat loading, constant pressure, leak detection, constant temperature, oxidation, nitrogen filling and boat unloading; The temperature of the boat loading is 600-800℃; The constant pressure comprises in turn first constant pressure, second constant pressure and third constant pressure; The oxidation comprises in turn first oxidation and second oxidation; The oxidation is accompanied by the introduction of nitrogen and oxygen, and the nitrogen / oxygen flow ratio is 1:(2-4); During the process from constant pressure to nitrogen filling, the temperature in the furnace gradually decreases from the furnace mouth to the furnace tail; During the process from constant pressure to nitrogen filling, the temperature at the furnace mouth is 5-10℃ higher than the temperature in the furnace; During the process from constant pressure to nitrogen filling, the temperature in the furnace is 5-10℃ higher than the temperature at the furnace tail; The temperature of the boat loading and unloading is 20-30℃ higher than the temperature of each intermediate step; The temperature of the boat unloading is 600-800℃; The pressure of the first constant pressure is 50-150mbar; The pressure of the second constant pressure is 600-800mbar; The pressure of the third constant pressure is 50-150mbar.

2. The optimization method of claim 1, wherein, The small nitrogen flow of the boat loading is 400-600sccm.

3. The optimization method of claim 1, wherein, The large nitrogen flow of the boat loading is 2000-4000sccm.

4. The optimization method of claim 1, wherein, The time of the first constant pressure is 100-300s.

5. The optimization method of claim 1, wherein, The temperature of the first constant pressure is 650-700℃.

6. The optimization method of claim 1, wherein, The small nitrogen flow of the first constant pressure is 100-300sccm.

7. The optimization method of claim 1, wherein, The time of the second constant pressure is 200-300s.

8. The optimization method of claim 1, wherein, The temperature of the second constant pressure is 650-700℃.

9. The optimization method of claim 1, wherein, The small nitrogen flow of the second constant pressure is 100-300sccm.

10. The optimization method of claim 1, wherein, The large nitrogen flow of the second constant pressure is 10000-20000sccm.

11. The optimization method of claim 1, wherein, The time of the third constant pressure is 100-200s.

12. The optimization method of claim 1, wherein, The temperature of the third constant pressure is 650-700℃.

13. The optimization method of claim 1, wherein, The small nitrogen flow of the third constant pressure is 100-300sccm.

14. The optimization method of claim 1, wherein, The time of the leak detection is 30-90s.

15. The optimization method of claim 1, wherein, The pressure of the leak detection is 950-1050mbar.

16. The optimization method of claim 1, wherein, The temperature of the leak detection is 650-700℃.

17. The optimization method of claim 1, wherein, The time of the constant temperature is 30-90s.

18. The optimization method of claim 1, wherein, The pressure of the constant temperature is 50-150mbar.

19. The optimization method of claim 1, wherein, The temperature of the constant temperature is 650-700℃.

20. The optimization method of claim 1, wherein, The small nitrogen flow of the constant temperature is 100-300sccm.

21. The optimization method of claim 1, wherein, The time of the first oxidation is 250-350s.

22. The optimization method of claim 21, wherein, The time of the first oxidation is 320-350s.

23. The optimization method of claim 1, wherein, The pressure of the first oxidation is 50-150mbar.

24. The optimization method of claim 1, wherein, The temperature of the first oxidation is 650-700℃.

25. The optimization method of claim 1, wherein, The nitrogen flow of the first oxidation is 2000-4000sccm.

26. The optimization method of claim 1, wherein, The oxygen flow of the first oxidation is 6000-10000sccm.

27. The optimization method of claim 1, wherein, The time of the second oxidation is 1500-1700s.

28. The optimization method of claim 27, wherein, The time of the second oxidation is 1500-1600s.

29. The optimization method of claim 1, wherein, The pressure of the second oxidation is 50-150mbar.

30. The optimization method of claim 1, wherein, The temperature of the second oxidation is 650-700℃.

31. The optimization method of claim 1, wherein, The nitrogen flow of the second oxidation is 2000-4000sccm.

32. The optimization method of claim 1, wherein, The oxygen flow of the second oxidation is 6000-10000sccm.

33. The optimization method of claim 1, wherein, The time of the nitrogen filling is 100-140s.

34. The optimization method of claim 1, wherein, The nitrogen filling pressure is 950-1050 mbar.

35. The optimization method of claim 1, wherein, The nitrogen filling temperature is 650-700℃.

36. The optimization method of claim 1, wherein, The small nitrogen flow rate of the boat-out is 400-600 sccm.

37. The optimization method of claim 1, wherein, The large nitrogen flow rate of the boat-out is 2000-4000 sccm.

38. The optimization method of claim 1, wherein, The optimization method comprises the following steps: (1) Boat-in: the temperature is 600-800℃, the small nitrogen flow rate is 400-600 sccm, and the large nitrogen flow rate is 2000-4000 sccm; (2) First constant pressure: the time is 100-300 s, the pressure is 50-150 mbar, the temperature is 650-700℃, and the small nitrogen flow rate is 100-300 sccm; (3) Second constant pressure: the time is 200-300 s, the pressure is 600-800 mbar, the temperature is 650-700℃, the small nitrogen flow rate is 100-300 sccm, and the large nitrogen flow rate is 10000-20000 sccm; (4) Third constant pressure: the time is 100-200 s, the pressure is 50-150 mbar, the temperature is 650-700℃, and the small nitrogen flow rate is 100-300 sccm; (5) Leak detection: the time is 30-90 s, the pressure is 950-1050 mbar, and the temperature is 650-700℃; (6) Constant temperature: the time is 30-90 s, the pressure is 50-150 mbar, the temperature is 650-700℃, and the small nitrogen flow rate is 100-300 sccm; (7) First oxidation: the time is 320-350 s, the pressure is 50-150 mbar, the temperature is 650-700℃, the nitrogen flow rate is 2000-4000 sccm, the oxygen flow rate is 6000-10000 sccm, and the nitrogen / oxygen flow rate ratio is 1:(2-4); (8) Second oxidation: the time is 1500-1600 s, the pressure is 50-150 mbar, the temperature is 650-700℃, the nitrogen flow rate is 2000-4000 sccm, the oxygen flow rate is 6000-10000 sccm, and the nitrogen / oxygen flow rate ratio is 1:(2-4); (9) Nitrogen filling: the time is 100-140 s, the pressure is 950-1050 mbar, and the temperature is 650-700℃; (10) Boat-out: the temperature is 600-800℃, the small nitrogen flow rate is 400-600 sccm, and the large nitrogen flow rate is 2000-4000 sccm; The optimization method is carried out in an annealing furnace, and the furnace temperature gradually decreases from the furnace mouth to the furnace tail during the process from constant pressure to nitrogen filling, the furnace mouth temperature is 5-10℃ higher than the furnace temperature, and the furnace temperature is 5-10℃ higher than the furnace tail temperature; the temperature of the boat-in and boat-out is 20-30℃ higher than the temperature of each intermediate step.

39. An oxide layer of a PERC solar cell prepared by using the optimization method according to any one of claims 1-38. The thickness of the oxide layer of the PERC solar cell is 1.5-1.8 nm.

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