Boron-gallium codoped quasi-monocrystalline silicon and preparation method thereof

[0030] Example 1

[0031] The (100) growth direction of the single crystal rod is cut into a square with a cross-sectional size of 156*156mm and a height of 20mm, which is placed on the bottom of the crucible tightly and orderly. Place silicon material on the seed crystal and mix with 300g of borosilicate alloy. The mass percentage of boron in the borosilicate alloy is about 0.01%. Add 1g of metallic gallium, totaling about 430kg, and the target resistivity is 1.6Ω·cm . Put the crucible filled with silicon material into the ingot furnace, vacuum and heat, control the heater to gradually increase the temperature in the furnace to 1540℃, when the seed crystal starts to melt to the remaining thickness of about 10mm, it jumps from melting to crystal growth stage. At the initial stage of crystal growth, the temperature was quickly reduced from 1540°C to 1440°C, and then the heat shield was opened to make the silicon crystal grow upward from the seed crystal melting interface; in the middle of crystal growth, the heating was controlled at an average cooling rate of about 1°C/h At the same time, open the heat shield at an average speed of 0.5cm/h. The silicon crystals will grow directionally from the bottom until they all grow into solids. After annealing and cooling, a large-grained boron-gallium co-doped standard is obtained. Single crystal silicon ingot. Since there is a very small amount of phosphorus in the silicon raw materials and the borosilicate alloy, the final quasi-single crystal silicon contains about 1.2×10 16 Pcs/cm 3 The concentration of boron and phosphorus is about 3×10 14 Pcs/cm 3 Of gallium.

[0032] The silicon ingot becomes 25 silicon squares after square extraction. The resistivity distribution measured by the resistivity tester is between 0.5-2.6Ω·cm, and the resistivity distribution along the growth direction of the silicon square is shown in the figure figure 1 As shown, the range of resistivity is within the current allowable range for the production of crystalline silicon cells. The silicon square is made by cutting, removing heads and tails, grinding, chamfering, slicing and solar cells, and its average efficiency reaches more than 17.6%. Take the large crystal grains (the grain area of ​​a certain crystal orientation accounts for 75% of the entire silicon wafer area). % Above) and small grains (the grain area of ​​a certain crystal orientation accounts for 50-75% of the entire silicon wafer area) of boron-gallium co-doped quasi-single crystal silicon cell test attenuation, and the two cells are each Divided into two groups, one group is directly tested, and the other group is tested after drying. The test condition is 1000w/m 2 Irradiated for 5h under the light conditions of, the test results show that the light-induced attenuation is less than -1%. figure 2 Shown.

[0033] Example 2

[0034] Take the polysilicon block with (100) as the main crystal orientation, and place multiple blocks with a height of 30mm on the bottom of the crucible tightly and orderly. Place silicon raw material on the seed crystal, mix 250g of boron alloy and 1g of metal gallium, total about 430kg, and target resistivity of 1.6Ω·cm. Put the crucible with silicon material into the ingot furnace, vacuum and heat, control the heater to gradually increase the temperature in the furnace to 1530℃, and adjust the heating rate at the bottom of the crucible to keep the temperature at the bottom of the crucible at 1300℃ to make the seed crystal Partially melted; when the seed crystal starts to melt to about 15mm thick, it jumps from the melting to the crystal growth stage. At the initial stage of crystal growth, the temperature was quickly reduced from 1530°C to 1430°C, and then the heat shield was opened to make the silicon crystals grow upward from the seed crystal melting interface; in the middle of crystal growth, the heating was controlled at an average temperature drop of about 0.8°C/h At the same time, when the heat shield is opened at an average speed of 0.3cm/h, silicon crystals will grow directionally from the bottom. After annealing and cooling, a large-grain boron-gallium co-doped quasi-single crystal silicon ingot will be obtained. Since the silicon raw material contains a small amount of phosphorus, the concentration of such quasi-single crystal silicon is about 1×10 16 Pcs/cm 3 The concentration of boron and phosphorus is about 3×10 16 Pcs/cm 3 Of gallium.

[0035] The silicon ingot becomes 25 silicon squares after the square is opened. The resistivity distribution measured by the resistivity tester is between 0.5-2.6Ω·cm, and the resistivity range is within the current allowable range for the production of crystalline silicon cells. The silicon square is made by cutting, removing heads and tails, grinding, chamfering, slicing and cell production, with an average efficiency of more than 17.6%. Take the boron-gallium co-doped quasi-monocrystalline silicon cell containing large and small crystal grains Test attenuation, the test results show that the light-induced attenuation is less than -1%.

[0036] Example 3

[0037] The (100) growth direction of the single crystal rod is cut into a square with a cross-sectional size of 156*156mm and a height of 10mm, which is placed on the bottom of the crucible tightly and orderly. Place silicon raw material on the seed crystal, mix 150g of boron alloy and 4.5g of metal gallium, total about 430kg, and target resistivity of 1.7Ω·cm. Put the crucible filled with silicon material into the ingot furnace, evacuate and heat, control the heater to gradually increase the temperature in the furnace to 1550℃, and adjust the heating rate at the bottom of the crucible to keep the temperature at the bottom of the crucible at 1350℃ to make the seed crystal Partially melted, when the seed crystal begins to melt to the remaining about 5mm thick, it jumps from the melting to the crystal growth stage. At the early stage of crystal growth, the temperature was quickly reduced from 1550°C to 1450°C, and then the heat shield was opened to make silicon crystals grow upward from the seed crystal melting interface; in the middle of crystal growth, the heating was controlled at an average cooling rate of about 1.2°C/h At the same time, when the heat shield is opened at an average speed of 0.8cm/h, silicon crystals will grow oriented from the bottom. After annealing and cooling, a large-grain boron-gallium co-doped quasi-single crystal silicon ingot will be obtained. Since the silicon raw material contains a very small amount of phosphorus, the final quasi-single crystal silicon contains a concentration of about 6×10 15 Pcs/cm 3 The concentration of boron and phosphorus is about 1.6×10 17 Pcs/cm 3 Of gallium.

[0038] The silicon ingot becomes 25 silicon squares after the square is opened. The resistivity distribution measured by the resistivity tester is between 0.5-2.6Ω·cm, and the resistivity range is within the current allowable range for the production of crystalline silicon cells. The silicon square is made by cutting, removing heads and tails, grinding, chamfering, slicing and cell production, with an average efficiency of more than 17.6%. Take the boron-gallium co-doped quasi-monocrystalline silicon cell containing large and small crystal grains Test attenuation, the test results show that the light-induced attenuation is less than -1%.