Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Fig. 1 shows a schematic plan view of a crystalline silicon film layer according to an embodiment of the present invention. Fig. 2 is a schematic plan view of another crystalline silicon film layer according to an embodiment of the present invention. The invention provides a crystalline silicon film layer 1, wherein the crystalline silicon film layer 1 comprises at least one first polycrystalline silicon part 11, the first polycrystalline silicon part 11 penetrates through the crystalline silicon film layer 1 from the thickness direction of the crystalline silicon film layer 1, and the number of the first polycrystalline silicon parts in the crystalline silicon film layer 1 is not limited. The crystalline silicon film layer 1 may be entirely composed of the first polysilicon portion 11, or the crystalline silicon film layer 1 may be composed of the first polysilicon portion 11 and the amorphous silicon portion 12, which is not particularly limited in the embodiment of the present invention. For example, referring to fig. 1, the crystalline silicon film layer 1 is entirely composed of the first polysilicon portions 11, or it can be considered that the crystalline silicon film layer 1 is composed of 1 first polysilicon portions 11, and the first polysilicon portions 11 penetrate the crystalline silicon film layer 1 from the thickness direction of the crystalline silicon film layer 1. Fig. 1 and 2 are schematic plan view structures of the crystalline silicon film layers, and thus, the thickness direction of the crystalline silicon film layer 1 in fig. 1 and 2 is perpendicular to the paper surface. As another example, referring to fig. 2, the crystalline silicon film layer 1 includes: 8 first polysilicon portions 11, and 7 amorphous silicon portions 12, each first polysilicon portion 11 penetrating the crystalline silicon film layer 1 from the thickness direction of the crystalline silicon film layer 1, each amorphous silicon portion 12 penetrating the crystalline silicon film layer 1 from the thickness direction of the crystalline silicon film layer 1. The first polysilicon portion 11 here may penetrate the crystalline silicon film layer 1 from the thickness direction of the crystalline silicon film layer 1 by: at least one three-dimensional structure is present in the first polysilicon portion 11, the three-dimensional structure comprising: at least one point and at least one surface, which are respectively located on two opposite surfaces in the thickness direction of the crystalline silicon film layer 1.
Fig. 3 shows an enlarged schematic view of a portion of a first polysilicon portion in an embodiment of the invention. Fig. 4 shows a partially enlarged schematic view of a polysilicon film layer of the prior art. Referring to fig. 3 and 4, the number of holes 111 of the first polysilicon portion 11 is smaller and the volume of the holes 111 is smaller in the present invention compared to the prior art, so that the first polysilicon portion 11 has smaller and more compact porosity in the present invention.
More specifically, the crystallization rate of the first polysilicon portion 11 is 50% to 60%, the hydrogen content in the first polysilicon portion 11 is 1% to 20%, the porosity of the first polysilicon portion 11 is 0.1% to 10%, the crystallization rate, the hydrogen content and the porosity of the first polysilicon portion 11 are respectively in the above ranges, and the film quality of the first polysilicon portion 11 is better, which is beneficial to improving the photoelectric conversion efficiency of the photovoltaic device. In addition, in the wet etching process, the etching rate of the first polysilicon portions 11 with better quality in the alkaline wet etchant and the acidic wet etching reagent is very low, and the etching of the first polysilicon portions 11 by the alkaline wet etchant and the acidic wet etching reagent is basically negligible, so that a mask layer is not required to be arranged on each first polysilicon portion 11, the step of arranging the mask layer on each first polysilicon portion 11 is reduced, the step of removing the mask layer after wet etching is reduced, the wet etching process is simplified, and the production efficiency is improved.
For example, referring to fig. 1, the crystalline silicon film layer 1 is composed of the first polysilicon portion 11, the photovoltaic device includes the crystalline silicon film layer 1 and the component a which are stacked, and in the process of setting the texture surface on the surface of the component a away from the crystalline silicon film layer 1, since the crystallization rate, the hydrogen content and the porosity of the first polysilicon portion 11 are respectively in the above ranges, the film quality of the first polysilicon portion 11 is better, in the process of texture surface making, the etching rate of the first polysilicon portion 11 with better quality is very slow in the texture surface making liquid, and the etching of the texture surface making liquid on the first polysilicon portion can be basically ignored, so that the mask layer can be omitted from being set on the crystalline silicon film layer 1, the steps of setting the mask layer on the crystalline silicon film layer 1 and removing the mask layer after wet etching are reduced, the texture surface making process is simplified, and the production efficiency is improved.
For another example, referring to the crystalline silicon film layer 1 shown in fig. 2, the crystalline silicon film layer 1 is composed of 8 first polysilicon portions 11 and 7 amorphous silicon portions 12, each of the first polysilicon portions 11 penetrates the crystalline silicon film layer 1 from the thickness direction of the crystalline silicon film layer 1, and each of the amorphous silicon portions 12 penetrates the crystalline silicon film layer 1 from the thickness direction of the crystalline silicon film layer 1. In the process of patterning the crystalline silicon film layer 1, as the crystallization rate, the hydrogen content and the porosity of the first polysilicon portion 11 are respectively in the ranges, the film layer quality of the first polysilicon portion 11 is better, in the process of patterning, the etching rate of the first polysilicon portion 11 with better quality is very slow in etching liquid, the etching of the etching liquid can be basically ignored, however, compared with the first polysilicon portion 11, the film layer quality of the amorphous silicon portion 12 is poorer, in the etching liquid, 7 amorphous silicon portions 12 can be etched completely, only 8 first polysilicon portions 11 are left, patterning is realized, and further, the step of arranging a mask layer on each first polysilicon portion 11 is omitted, the step of removing the mask layer after patterning is omitted, the patterning process is simplified, and the production efficiency is improved.
For example, the crystallization rate of the first polysilicon portion 11 may be 50%, or 50.2%, or 52%, or 52.9%, or 53.7%, or 54.9%, or 55%, or 55.3%, or 57%, or 59%, or 60%, the hydrogen content in the first polysilicon portion 11 is 1%, or 2.3%, or 4%, or 7%, or 9.7%, or 10.4%, or 10.5%, or 10.9%, or 12%, or 15%, or 20%, and the porosity of the first polysilicon portion 11 is 0.1%, or 1%, or 3%, or 4.7%, or 5.05%, or 6%, or 7.5%, or 8%, or 9%, or 9.5%, or 10%.
It should be noted that, the hydrogen content in one first polysilicon portion 11 may refer to: the total number of hydrogen bonds in the first polysilicon portion 11 is a proportion of the total number of all bonds in the first polysilicon portion 11. The crystallization rate in a first polysilicon portion 11 may refer to the ratio of crystals in the first polysilicon portion 11. The porosity in a first polysilicon portion 11 may refer to the percentage of the total volume of pores in the first polysilicon portion 11 to the total volume of the first polysilicon portion 11. For the crystallization rate and the porosity, a predetermined number of points may be selected from the first polysilicon portion 11, the points being located at different positions in the first polysilicon portion 11, respectively, the crystallization rate and the porosity at each point being measured, and then the crystallization rates at all points being arithmetically averaged to obtain the crystallization rate of the first polysilicon portion 11, and the porosities at all points being arithmetically averaged to obtain the porosity of the first polysilicon portion 11. The number of points selected for the crystallization rate and the porosity may be the same or different, and each point may be representative of the first polysilicon portion 11. For example, the first polysilicon portion 11 is rectangular, and for both the crystallization rate and the porosity, 5 points may be selected, the 5 points being located at four vertices of the rectangle, and the geometric center of the rectangle, respectively. For another example, for both the crystallization rate and the porosity, 30 points may be selected, the 30 points being uniformly distributed in the first polysilicon portion 11.
Optionally, the first polysilicon portion 11 is a doped polysilicon portion, and the doping concentration of the doped polysilicon portion is: 5X 1018 cm-3 Up to 1X 1020 cm-3 Specifically, the film quality of the first polysilicon portion 11 is better, so that the first polysilicon portion 11 can obtain a wider doping concentration range, and the applicable scene is wider. For example, the first polysilicon portion 11 is a doped polysilicon portion, and the doping concentration of the doped polysilicon portion may be: 5X 1018 cm-3 Or 8X 1018 cm-3 Or 9.3X1018 cm-3 Or 1X 1019 cm-3 Or 4X 1019 cm-3 Or 5X 1019 cm-3 Or 5.25X1019 cm-3 Or 6X 1019 cm-3 Or 8X 1019 cm-3 Or 9X 1019 cm-3 Or 1X 1020 cm-3 。
Note that the first polysilicon portion 11 may be doped N-type or P-type, which is not limited thereto.
Optionally, the thickness difference of the crystalline silicon film layer 1 is less than 5%. The thickness difference of the crystalline silicon film layer 1 is as follows: the maximum value of the thicknesses at a plurality of positions in the crystalline silicon film layer 1 is subtracted from the first difference value obtained by subtracting the average value of the thicknesses, and the first quotient value obtained by dividing the average value of the thicknesses is obtained. Alternatively, the thickness difference of the crystalline silicon film layer 1 is: and a second quotient obtained by dividing a second difference obtained by subtracting the minimum value of the plurality of thicknesses from the average value of the plurality of thicknesses at a plurality of positions in the crystalline silicon film layer 1. The thickness difference of the crystalline silicon film layer 1 is smaller than 5%, which indicates that the thickness uniformity of the crystalline silicon film layer 1 is good, the thickest part of the crystalline silicon film layer 1 is not too thick in the process of etching the crystalline silicon film layer 1, the etching time is not too long, the etching time can be saved, and the etching efficiency is improved. Each first polysilicon part is a part of the crystalline silicon film layer, and penetrates through the crystalline silicon film layer from the thickness direction of the crystalline silicon film layer, so that the thickness difference of each first polysilicon part is basically equal to that of the crystalline silicon film layer, the thickness difference of each first polysilicon part is smaller than 5%, the thickness uniformity of each first polysilicon part is better, in the process of etching each first polysilicon part, the thickest part of each first polysilicon part is not too thick, the etching time is not too long, the etching time can be saved, and the etching efficiency is improved. Under the condition that the crystalline silicon film layer comprises amorphous silicon parts, each amorphous silicon part is a part of the crystalline silicon film layer, and each amorphous silicon part penetrates through the crystalline silicon film layer from the thickness direction of the crystalline silicon film layer, so that the thickness difference of each amorphous silicon part is basically equal to that of the crystalline silicon film layer, the thickness difference of each amorphous silicon part is smaller than 5%, the thickness uniformity of each amorphous silicon part is better, in the process of etching each amorphous silicon part, the thickest part of each amorphous silicon part is not too thick, the etching time is not too long, the etching time can be saved, and the etching efficiency is improved.
Optionally, referring to fig. 2, the crystalline silicon film layer 1 further includes: at least one amorphous silicon portion 12, the amorphous silicon portion 12 penetrates the crystalline silicon film layer 1 from the thickness direction of the crystalline silicon film layer 1, and in the crystalline silicon film layer 1, the first polysilicon portion 11 and the amorphous silicon portion 12 are alternately distributed. The crystallization rate of the amorphous silicon part 12 is lower than that of the first polysilicon part 11, the hydrogen content and the porosity of the amorphous silicon part 12 are larger than those of the first polysilicon part 11, that is, compared with the first polysilicon part 11, the quality of the film layer of the amorphous silicon part 12 is relatively poor, when the amorphous silicon part 12 in the crystalline silicon film layer 1 needs to be removed and the first polysilicon part 11 is reserved, on one hand, the film layer quality of the amorphous silicon part 12 is relatively poor, the removal speed is faster, the process time is reduced, on the other hand, the quality of the film layer of the amorphous silicon part 11 is better than that of the amorphous silicon part 12, and when the amorphous silicon part 12 in the crystalline silicon film layer 1 needs to be removed and the first polysilicon part 11 is reserved, the etching rate of the first polysilicon part 11 is very slow in an alkaline wet etching agent and an acid wet etching agent, the etching rate of the amorphous silicon part 12 is basically negligible, and then the etching rate of the first polysilicon part 11 does not need to be formed on each first polysilicon part 11, the mask layer is reduced, the mask layer is removed, and the mask layer is removed. It should be noted that, here, the hydrogen content in one amorphous silicon portion 12 may refer to: the total number of hydrogen bonds in the amorphous silicon portion 12 is a proportion of the total number of all bonds in the amorphous silicon portion 12. The crystallization rate in an amorphous silicon portion 12 may refer to the ratio of crystals in the amorphous silicon portion 12. The porosity in an amorphous silicon portion 12 may refer to the percentage of the total volume of pores in the amorphous silicon portion 12 to the total volume of the amorphous silicon portion 12.
The crystallization rate of the amorphous silicon portion 12 is not particularly limited, and the hydrogen content and the porosity of the amorphous silicon portion 12 are smaller than those of the first polysilicon portion 11, and the hydrogen content and the porosity of the amorphous silicon portion 12 are larger than those of the first polysilicon portion 11. The determination manners of the hydrogen content, the crystallization rate, and the porosity of the amorphous silicon portion 12 may be referred to as the determination manners of the hydrogen content, the crystallization rate, and the porosity of the first polysilicon portion 11, and are not repeated here.
The invention also provides a preparation method of any one of the crystalline silicon film layers 1. The method may include the following steps.
Step 101, providing an amorphous silicon film layer.
The crystallization rate of the amorphous silicon film layer is lower than that of the first polysilicon portion 11, and the hydrogen content and the porosity of the amorphous silicon film layer are both greater than those of the first polysilicon portion 11. The hydrogen content in the amorphous silicon film layer may refer to: the total number of hydrogen bonds in the amorphous silicon film is a proportion of the total number of all bonds in the amorphous silicon film. The crystallization rate in the amorphous silicon film layer may refer to the ratio of crystals in the amorphous silicon film layer. The porosity in the amorphous silicon film layer may refer to the percentage of the total volume of pores in the amorphous silicon film layer to the total volume of the amorphous silicon film layer. The determination manners of the hydrogen content, the crystallization rate, and the porosity of the amorphous silicon film layer may refer to the determination manners of the hydrogen content, the crystallization rate, and the porosity of the first polysilicon portion 11, and in order to avoid repetition, the description is omitted here.
Step 102, heating the amorphous silicon film layer by adopting infrared light until the temperature of the amorphous silicon film layer reaches a preset temperature, and carrying out hydrogenation and crystallization on at least one part of the amorphous silicon film layer by adopting laser, wherein a part acted by the laser forms a first polycrystalline silicon part; the preset temperature is 5% -30% of the temperature of the laser; wherein, the infrared light heating and the laser action are performed simultaneously, or the infrared light heating is performed first and then the laser action is performed.
Figure 5 shows a schematic diagram of crystallization and hydrogenation in an embodiment of the invention. Fig. 6 shows a schematic diagram of crystallization and hydrogenation in the prior art. In the present invention, the main purpose of heating the amorphous silicon film layer 2 by using the infrared light 31 is to: in the first aspect, the infrared light 31 does not cause damage basically, and the infrared light 31 can provide a certain heat basis for the amorphous silicon film layer 2, so that the energy of the laser 32 can be reduced, and the laser damage can be reduced. In the second aspect, the hydrogen has a high absorptivity for the infrared light 31, which is favorable for the slow release of hydrogen, and the slow release of hydrogen can greatly reduce the porosity. In the third aspect, the infrared light 31 can easily raise the temperature of the amorphous silicon film layer 2 to the preset temperature. That is, compared with the prior art shown in fig. 6, in which only the laser light 32 is used for crystallization and hydrogenation, the energy of the laser light 32 can be reduced and the damage of the laser light can be reduced due to the auxiliary heating of the infrared light 31, and the hydrogen has a higher absorptivity to the infrared light 31, which is beneficial to the slow release of the hydrogen, and meanwhile, the infrared light 31 can easily raise the temperature of the amorphous silicon film layer 2 to the preset temperature.
In the present invention, the infrared light 31 is used to heat the whole amorphous silicon film layer 2, so that the heating process is simple, and the whole amorphous silicon film layer 2 is heated uniformly, the stress distribution is uniform, and warpage and the like can be reduced, compared with the case that only the infrared light 31 is used to heat the part to be crystallized and hydrogenated. For example, the amorphous silicon film layer 2 may be placed on an auxiliary mesa, the auxiliary mesa may be heated to a preset temperature using infrared light, or the like.
The preset temperature is 5% -30% of the temperature of the laser, under the preset temperature, the laser and the infrared light are well matched, the slow release of hydrogen is facilitated, the slow release of hydrogen can be realized, the porosity can be reduced to a great extent, meanwhile, the infrared light with the preset temperature is easy to reach, the laser is matched, good crystallization and hydrogenation effects can be achieved, and laser damage caused by the laser is smaller. In the invention, the main purpose of the laser and infrared light matching is to facilitate the slow release of hydrogen, the slow release of hydrogen and the reduction of laser damage, and the improvement of crystallization rate is not excessively limited. For example, the temperature may be 5%, or 8%, or 9%, or 10%, or 13.5%, or 17%, or 17.5%, or 18%, or 21%, or 28%, or 30% of the temperature of the laser.
In the amorphous silicon film layer 1, a portion where the laser light 32 acts forms a first polysilicon portion 11. The portion where the laser light 32 does not act is an amorphous silicon portion.
The heating by the infrared light 31 and the laser 32 are performed simultaneously, that is, the infrared light 31 heats the amorphous silicon film 2, and at least a part of the amorphous silicon film 2 is hydrogenated and crystallized by the laser 32, and the infrared light 31 heats the amorphous silicon film 2 to heat the amorphous silicon film 2 to the predetermined temperature. Heating by the infrared light 31 and then the laser 32 means that the infrared light 31 is used to heat the amorphous silicon film layer 2, the amorphous silicon film layer 2 is heated to the preset temperature, and then the laser 32 is used to hydrogenate and crystallize at least a part of the amorphous silicon film layer 2.
Optionally, in the present invention, the power of the laser 32 is 20W to 200W, and the laser at the power is beneficial to slow release of hydrogen, so that the porosity can be reduced to a great extent, the laser damage is smaller, and the crystallization degree and the hydrogenation degree are more suitable. The preset temperature is 100-300 ℃, the infrared light 31 can easily raise the temperature of the amorphous silicon film layer 2 to the preset temperature, and the laser damage is smaller, the hydrogen release speed is more proper, and the porosity can be further reduced under the auxiliary effect of the preset temperature.
For example, in the present invention, the power of the laser 32 is 20W, or 30W, or 50W, or 60W, or 90W, or 105W, or 110W, or 113W, or 140W, or 170W, or 200W. The preset temperature may be 100 ℃, or 110 ℃, or 140 ℃, or 160 ℃, or 190 ℃, or 197 ℃, or 200 ℃, or 210 ℃, or 260 ℃, or 290 ℃, or 300 ℃.
In the present invention, the wavelength of the infrared light 31 is not limited, and the wavelength of the laser light 32 and the like may be not limited. For example, the wavelength of the infrared light 31 may be 50nm-3000nm. The laser 32 may be a 500-600nm nanosecond laser. Alternatively, the laser 32 may have a pulse width of 10ns-100ns, a spot size of 20um-300um (microns), green light at 492nm-577nm, and the like.
Fig. 7 shows a schematic diagram of a laser in an embodiment of the invention. In fig. 7, the black and white triangles distributed up and down are both triangular laser spots. Fig. 8 shows a schematic diagram of a laser of the prior art. Referring to fig. 8, in the prior art, a square laser spot is often adopted in the photovoltaic field, however, the inventor finds that the number of sides of the square laser spot is more, burrs and the like inevitably exist on each side, so that the square laser spot is not easy to splice into a regular pattern in the splicing process, and the laser damage areas are more and are irregularly distributed due to the fact that the burrs are more, and damage caused by laser is not easy to remove. Optionally, in order to solve the problem, the inventor creatively adjusts the spot shape of the laser 32 to be triangular, as shown in fig. 7, the number of sides of the triangle is smaller and burrs are smaller than that of the square, so that the laser 32 is easier to splice into a regular pattern in the splicing process, and the laser damage area is fewer and the distribution is more regular due to fewer burrs, so that damage caused by the laser is easier to remove.
More specifically, the triangular laser light spots can be regular triangular laser light spots, regular patterns are spliced more easily in the splicing process, burrs are fewer, laser damage areas are fewer, the distribution is more regular, and damage caused by laser is removed more easily.
Optionally, the foregoing step 101 may include: a substrate is provided. On the first surface of the substrate, the amorphous silicon film layer 2 having a crystallization rate of 5% -40% and a porosity of 0.1% -20% is formed by means of LPCVD (Low Pressure Chemical Vapor Deposition ). Or, on the substrate, the amorphous silicon film layer 2 with crystallization rate of 5% -30% and porosity of 0.1% -20% is formed by adopting a PECVD (Plasma Enhanced Chemical Vapor Deposition ) method. Wherein, in the PECVD mode, the technological parameters comprise at least one of the following five technological parameters: the radio frequency power supply switching ratio is 1/5-4/5; the discharge times are 2-5 ten thousand times; the discharge gas is a mixed gas formed by hydrogen, nitrogen and argon; in the mixed gas, the volume concentration of hydrogen is 5-70%, and the volume concentration of argon is 10-80%; the power of the radio frequency power supply is 5000w-15000w; the process temperature is 300-500 ℃.
Specifically, the substrate is not particularly limited as to the deposition carrier of the amorphous silicon film layer 2, the material of the substrate, and the like. By adopting the LPCVD mode, the amorphous silicon film layer 2 has certain crystallization due to a certain temperature in the LPCVD deposition process, the crystallization rate is between 5 and 40 percent, and the porosity is between 0.1 and 20 percent. Because the deposition temperature of PECVD is lower, the crystallization rate of the amorphous silicon film layer 2 is lower, the crystallization rate is between 5% and 30%, and the porosity is between 0.1% and 20%. In the PECVD mode, the radio frequency power supply switching ratio is adjusted, smaller switching ratio is used, meanwhile, high-quality film deposition is realized by using denser switching frequency, specifically, the switching ratio range is 1/5-4/5, the discharge frequency is 2-5 ten thousand times, and the high-quality amorphous silicon film layer 2 with the thickness difference within 5% is obtained by adjusting the radio frequency power supply switching ratio, the discharge frequency and the like. And/or, in the PECVD mode, the discharge gas is a mixed gas formed by hydrogen, nitrogen and argon. In the mixed gas, the volume concentration of hydrogen is 5-70%, and the volume concentration of argon is 10-80%. According to the invention, nitrogen, argon and hydrogen are mixed for discharging, hydrogen molecules are small, ionization is easier to enter the amorphous silicon film layer 2, the nitrogen and the argon assist ionization, the nitrogen and the argon are larger in molecules than the hydrogen, ionization is not easy to enter the amorphous silicon film layer 2, the porosity can be reduced, and the nitrogen and the argon can ensure the ionization effect. Meanwhile, under the condition that the substrate is a silicon substrate, nitrogen is easy to react with the silicon substrate, the cost of argon is high, nitrogen and argon are adopted, and the volume concentration of the argon is 10% -80%, so that compared with the case that only one of the nitrogen and the argon is adopted, the cost can be reduced, and the reaction with the silicon substrate is reduced. And/or, in the PECVD mode, the power of the radio frequency power supply is 5000w-15000w, the power of the radio frequency power supply is relatively low, the power consumption can be reduced, the crystallization rate of the amorphous silicon film layer 2 is properly reduced, and the thickness difference of the amorphous silicon film layer 2 can be reduced. And/or, in the PECVD mode, the process temperature is 300-500 ℃, so that the power consumption can be reduced, the crystallization rate of the amorphous silicon film layer 2 is properly reduced, and the thickness difference of the amorphous silicon film layer 2 can be reduced. Because the thickness difference of the amorphous silicon film layer 2 is smaller, the thickest part is not too thick, and the cleaning time of the amorphous silicon film layer 2 can be reduced by 10 to 50 percent.
For example, the substrate may be a silicon substrate, in a PECVD manner: the radio frequency power supply switching ratio may be 1/5, or 1/4, or 1/3, or 2/5, or 1/2, or 3/5, or 2/3, or 3/4, or 4/5. The number of discharges may be 2 ten thousand, or 2.2 ten thousand, or 2.9 ten thousand, or 3.3 ten thousand, or 3.4 ten thousand, or 3.5 ten thousand, or 3.7 ten thousand, or 4 ten thousand, or 5 ten thousand. The discharge gas is a mixed gas of hydrogen, nitrogen and argon. In the mixed gas, the volume concentration of the hydrogen gas may be 5%, or 10%, or 19%, or 26%, or 35%, or 37.5%, or 50%, or 70%, and the volume concentration of the argon gas may be 10%, or 30%, or 40%, or 50%, or 60%, or 67.5%, or 70%, or 80%. The power of the radio frequency power supply may be 5000w, or 6000w, or 7000w, or 9000w, or 9600w, or 10000w, or 11000w, or 13000w, or 14000w, or 15000w. The process temperature may be 300 ℃, or 310 ℃, or 360 ℃, or 390 ℃, or 400 ℃, or 405 ℃, or 430 ℃, or 480 ℃, or 500 ℃.
Optionally, the foregoing providing a substrate may include: and polishing the first surface of the substrate to obtain a first surface with the reflectivity of 30-50%, wherein the first surface of the substrate is smoother, and the amorphous silicon film layer 2 with better film quality is easier to obtain on the flatter first surface.
For example, the first surface of the substrate is subjected to a polishing process to obtain a first surface having a reflectance of 30%, or 32%, or 39%, or 40%, or 41%, or 46%, or 49%, or 50%.
The polishing etchant is not particularly limited. For example, the polishing etchant may include an alkali solution and an etching additive, wherein the mass concentration of the alkali in the polishing etchant is 1% to 20%, and the mass concentration of the etching additive is 1% to 20%.
The present invention also provides a solar cell comprising: the tunnel oxide layer is arranged on the silicon substrate, and the first doped film layer is arranged on the tunnel oxide layer. The first doped film layer is: in the process of forming a solar cell, after any of the foregoing crystalline silicon film layers 1 is formed, a film layer is formed under the influence of the subsequent steps. Or, the first doped film layer is: in the process of forming the solar cell, after the crystalline silicon film layer 1 is prepared by any one of the preparation methods of the crystalline silicon film layer 1, the film layer is formed under the influence of the subsequent steps. Thus, the structure of the first doped film layer in the solar cell is similar to the structure of the aforementioned crystalline silicon film layer, and the first doped film layer in the solar cell may include: at least one second polysilicon portion penetrating the first doped film layer from the thickness direction of the first doped film layer. In the solar cell, after the crystalline silicon film layer 1 is disposed, there may be a process of heating during the preparation of other layers, and the heating process may bring about a thermal influence on the first polysilicon portion 11, for example, sintering of an electrode may bring about a certain thermal influence on the crystalline silicon film layer 1, and the thermal influence is mainly reflected in the improvement of the crystallization rate, and thus the crystallization rate of the first polysilicon portion 11 may be improved. Accordingly, the crystallization rate of the first doped film layer in the solar cell is greater than or equal to 60%, for example, the crystallization rate of the first polysilicon portion 11 of the crystalline silicon film layer 1 is 50% to 60%, and the crystallization rate of the second polysilicon portion in the solar cell is 60% to 80%. The hydrogen content and the porosity of the first polysilicon portion 11 are slightly changed by heat, so that the hydrogen content and the porosity of the second polysilicon portion are substantially equal to those of the first polysilicon portion 11, and thus the hydrogen content of the second polysilicon portion is 1% to 20% and the porosity of the second polysilicon portion is 0.1% to 10%.
The first doped film layer is as follows: in the process of forming the solar cell, after the crystalline silicon film layer 1 is prepared by any one of the foregoing preparation methods of the crystalline silicon film layer 1, in the case of a film layer formed under the influence of the subsequent steps, the substrate may be a silicon substrate and a tunneling oxide layer located on the silicon substrate in the foregoing preparation method of the crystalline silicon film layer 1.
In the solar cell, the crystallization rate of the second polysilicon part is higher, the hydrogen content of the second polysilicon part is also more suitable, the porosity of the second polysilicon part is more suitable, the film quality of the second polysilicon part is better, and the photoelectric conversion efficiency of the solar cell is improved. Other advantages of the solar cell, etc. can refer to the above description of the crystalline silicon film layer 1 or the preparation method of the crystalline silicon film layer 1, and have similar or similar beneficial effects, so that the description is not repeated here. The specific type of the solar cell is not limited.
Optionally, the first doped film layer is entirely composed of the second polysilicon portion, that is, referring to fig. 1, the crystalline silicon film layer 1 is entirely composed of the first polysilicon portion 11, the surface of the silicon substrate far away from the crystalline silicon film layer 1 is in a textured structure, for the preparation of the solar cell, after the crystalline silicon film layer 1 is set, the surface of the silicon substrate far away from the crystalline silicon film layer 1 can be textured, in the texturing process, since the crystalline silicon film layer 1 is entirely composed of the first polysilicon portion 11, the quality of the crystalline silicon film layer 1 is better, the crystalline silicon film layer 1 is not etched in the texturing solution basically, therefore, no mask layer is required to be set on the crystalline silicon film layer 1, the steps of setting the mask layer and removing the mask layer are reduced, the production steps of the solar cell are fewer, and the production efficiency is higher.
Optionally, the thickness variation of the first doped film layer is less than 5%. Specifically, the first doped film layer is: in the process of forming a solar cell, after any of the foregoing crystalline silicon film layers 1 is formed, a film layer is formed under the influence of the subsequent steps. Or, the first doped film layer is: in the process of forming the solar cell, after the crystalline silicon film layer 1 is prepared by any one of the preparation methods of the crystalline silicon film layer 1, the film layer is formed under the influence of the subsequent steps. The effect of the subsequent steps, mainly thermal effect, is that the thermal effect has substantially no effect on the thickness variability, and therefore, the thickness variability of the first doped film layer is also less than 5%. The thickness difference of the first doped film layers is also smaller than 5%, which indicates that the thickness uniformity of the first doped film layers is good, the thickest part is not too thick in the process of processing each first doped film layer, the processing time is not too long, the process time can be saved, and the production efficiency is improved. The determination method of the thickness difference of the first doped film layer may refer to the determination method of the thickness difference of the foregoing crystalline silicon film layer, and in order to avoid repetition, details are not repeated here.
The invention also provides a back contact solar cell comprising: a silicon substrate, a first region and a second region falling on the silicon substrate are projected. Wherein the first areas and the second areas are alternately distributed. The relative sizes of the first and second regions are not limited. The first region may include: the tunnel oxide layer and the first transmission layer are stacked, and the relative positional relationship between the first transmission layer and the tunnel oxide layer may be: the first transmission layer is positioned in the surface of the silicon substrate close to the tunneling oxide layer or on the silicon substrate, the tunneling oxide layer is positioned on the first transmission layer, or the tunneling oxide layer is positioned on the silicon substrate, and the first transmission layer is positioned on the tunneling oxide layer, namely, the tunneling oxide layer is positioned between the silicon substrate and the first transmission layer. The crystallization rate of the first transmission layer is greater than or equal to 60%, the hydrogen content of the first transmission layer is 1% to 20%, and the porosity of the first transmission layer is 0.1% to 10%. The first transport layer here is: in the process of forming the back contact solar cell, after any of the foregoing crystalline silicon film layers 1 is formed, the amorphous silicon portion is removed and the film layer formed under the influence of the subsequent steps is formed. Or, the first transport layer here is: in the process of forming the back contact solar cell, after the crystalline silicon film layer 1 is prepared by any one of the aforementioned preparation methods of the crystalline silicon film layer 1, the amorphous silicon is partially removed and the film layer is formed under the influence of the subsequent steps. In the back contact solar cell, after the crystalline silicon film layer 1 is disposed, there may be a process of heating during the preparation of other layers, and the heating process may bring about a thermal influence on the first polysilicon portion 11, for example, sintering of an electrode may bring about a certain thermal influence on the crystalline silicon film layer 1, and the thermal influence is mainly reflected in the improvement of the crystallization rate, and thus the crystallization rate of the first polysilicon portion 11 may be improved. Accordingly, the crystallization rate of the first transmission layer in the back contact solar cell is greater than or equal to 60%, for example, the crystallization rate of the first polysilicon portion 11 of the crystalline silicon film layer 1 is 50% to 60%, and the crystallization rate of the first transmission layer in the back contact solar cell is 60% to 80%. The hydrogen content and the porosity of the first polysilicon portion 11 are slightly changed by heat, so that the hydrogen content and the porosity of the first transmission layer are substantially equal to those of the first polysilicon portion 11, and thus the hydrogen content of the first transmission layer is 1% to 20% and the porosity of the second polysilicon portion is 0.1% to 10% in the back contact solar cell.
The second region may include a second transport layer, the doping types of the first transport layer and the second transport layer being different, i.e., one of the first transport layer and the second transport layer is P-type doped and the other is N-type doped. It should be noted that whether the tunnel oxide layer exists on the second region is not limited, for example, the tunnel oxide layer does not exist on the second region. In the case where the tunnel oxide layer is provided on the second region, the relative positional relationship between the second transmission layer and the tunnel oxide layer and the like are not particularly limited.
The back contact solar cell has the advantages similar to or similar to the aforementioned crystalline silicon film layer or the crystalline silicon film layer, and is not repeated here. The specific type of the back contact solar cell is not limited.
Optionally, the thickness of the first transmission layer varies by less than 5%. Specifically, the first transmission layer here is: in the process of forming the back contact solar cell, after any of the foregoing crystalline silicon film layers 1 is formed, the amorphous silicon portion is removed and the film layer formed under the influence of the subsequent steps is formed. Or, the first transport layer here is: in the process of forming the back contact solar cell, after the crystalline silicon film layer 1 is prepared by any one of the aforementioned preparation methods of the crystalline silicon film layer 1, the amorphous silicon is partially removed and the film layer is formed under the influence of the subsequent steps. The effect of the subsequent steps, mainly thermal, has substantially no effect on the thickness variability of the first transport layer, and therefore the thickness variability of the first transport layer is also less than 5%. The thickness uniformity of the first transmission layer is good everywhere, and in the process of processing the first transmission layer, the thickest part is not too thick, the processing time is not too long, the process time can be saved, and the production efficiency is improved. The determination manner of the thickness difference of the first transmission layer may refer to the determination manner of the thickness difference of the foregoing crystalline silicon film layer, and in order to avoid repetition, details are not repeated here.
The invention also provides a preparation method of the back contact solar cell, which comprises the following steps.
Step S1, providing a conductive substrate; the conductive substrate includes: a silicon substrate, a tunneling oxide layer and a crystalline silicon film layer which are sequentially laminated on the silicon substrate; the crystal silicon film layer is any one of the crystal silicon film layers, or is prepared by any one of the preparation methods of the crystal silicon film layers; the crystalline silicon film layer comprises: at least one first polysilicon portion and at least one amorphous silicon portion; the amorphous silicon part penetrates through the crystalline silicon film layer from the thickness direction of the crystalline silicon film layer; in the crystalline silicon film layer, the first polycrystalline silicon part and the amorphous silicon part are alternately distributed.
The silicon substrate, the tunneling oxide layer and the crystalline silicon film layer may all include: the projections fall into a first region of the silicon substrate and the projections fall into a second region of the silicon substrate, the first and second regions being alternately distributed. In the crystalline silicon film layer, the first polysilicon portion is located in the first region, the amorphous silicon portion is located in the second region, and both the amorphous silicon portion and the first polysilicon portion penetrate the crystalline silicon film layer in the thickness direction of the crystalline silicon film layer, and the first polysilicon portion and the amorphous silicon portion are alternately distributed, that is, the crystalline silicon film layer 1 is shown with reference to fig. 2.
And S2, carrying out wet etching on the conductive substrate under the condition that each first polysilicon part is not covered by a mask layer, wherein each first polysilicon part is reserved in the wet etching, each amorphous silicon part is removed in the wet etching, and the tunneling oxide layer or the second area of the silicon substrate is exposed.
In step S2, the first polysilicon portion remaining in the wet etching forms a first transmission layer under the influence of the subsequent step.
And S3, forming a second transmission layer on the exposed second area.
That is, the crystalline silicon film layer 1 is shown with reference to fig. 2. In the wet etching process of step S2, since the quality of the first polysilicon portions 11 is better, the first polysilicon portions 11 are not etched in the wet etching solution, so that no mask layer is required to be disposed on each first polysilicon portion 11, the steps of disposing a mask layer on each first polysilicon portion 11 and removing the mask layer are reduced, and the back contact solar cell has fewer production steps and higher production efficiency. It should be noted that, in the process of removing the amorphous silicon portion in the crystalline silicon film layer by wet etching, the tunneling oxide layer under the amorphous silicon film layer may be etched away, so that the portion of the silicon substrate located in the second region may be exposed. And under the condition that the tunneling oxide layer of the second region is not etched, exposing the second region of the tunneling oxide layer, and forming a second transmission layer on the second region of the tunneling oxide layer. The second region of the silicon substrate is exposed with the second region of the tunnel oxide etched away, where a second transport layer may be formed over the second region of the tunnel oxide.
Alternatively, the first transmission layer may be a P-type doped transmission layer, and the second transmission layer may be an N-type doped transmission layer, so as to reduce thermal influence.
The present application is further illustrated below in conjunction with specific examples.
Example 1
And arranging a tunneling oxide layer on the silicon substrate, wherein the tunneling oxide layer and the silicon substrate are respectively arranged in a first area and a second area, and the first area and the second area are alternately distributed. The tunneling oxide layer away from the first surface of the silicon substrate comprises: a portion located in the first region and a portion located in the second region. And forming a P-type doped amorphous silicon film layer 2 with the crystallization rate of 5% -30%, the porosity of 0.1% -20% and the hydrogen content of 30% -40% on the tunneling oxide layer by adopting a PECVD mode. The amorphous silicon film layer 2 is heated by infrared light until the temperature of the amorphous silicon film layer 2 reaches a preset temperature of 100 ℃ and is kept warm, then, a plurality of parts of the amorphous silicon film layer 2, which are positioned in a first area, are hydrogenated and crystallized by adopting laser with 20W, a part with laser action is formed into a first polysilicon part 11, and a part without laser action is formed into an amorphous silicon part 12, namely, the amorphous silicon part 12 is formed for the part of the amorphous silicon film layer 2, which is positioned in a second area, so that a conductive substrate is obtained. The first polysilicon portions 11 and the amorphous silicon portions 12 penetrate the crystalline silicon film layer 2 from the thickness direction of the crystalline silicon film layer 2, and in the crystalline silicon film layer 1, the first polysilicon portions 11 and the amorphous silicon portions 12 are alternately distributed, and the resulting crystalline silicon film layer 1 is shown in fig. 2. In the PECVD method: the radio frequency power supply switching ratio is 3/5, the discharge times are 4 ten thousand times, and the discharge gas is mixed gas formed by hydrogen, nitrogen and argon. In the mixed gas, the volume concentration of hydrogen was 40%, the volume concentration of argon was 43%, and the volume concentration of nitrogen was 17%. The power of the radio frequency power supply is 10000w, and the process temperature is 400 ℃.
Under the condition that a mask layer is not covered on each first polysilicon part 11, wet etching is carried out on the conductive substrate, the components of the wet etchant are alkali and additives, the etching time is 15 minutes (min) to 20min, each first polysilicon part 11 is not etched basically in the wet etching and remains basically, each amorphous silicon part 12 is removed in the wet etching, the second area of the tunneling oxide layer is exposed, and then mixed acid is adopted for cleaning for 15min to 20min. The mixed acid herein may include: HF. HNO (HNO)3 、H2 SO4 And the like, wherein the mixed acid aims at neutralizing alkali in the wet etching agent and etching away the part of the tunneling oxide layer positioned in the second area, and the second area of the silicon substrate is exposed.
And forming a second N-type doped transmission layer on the exposed second region of the silicon substrate.
Compared with the prior art, in which the polysilicon film layer with a relatively uniform texture is formed and then the polysilicon film layer on the second region is removed by laser, in the first aspect, in the embodiment 1, the laser only plays the roles of hydrogenation and crystallization, and has the assistance of infrared light, the laser power is smaller, and the laser damage is smaller, in the second aspect, in the embodiment 1, the laser action area is as shown in fig. 2, only each first polysilicon portion 11, however, in the prior art, the second region is removed by laser, since the second region needs to leave an insulating region mainly playing the role of insulation except for forming another doped second transmission layer, the second region is larger, that is, the laser action area is larger, that is, compared with the prior art, the laser action area is smaller, and the laser damage is further greatly reduced.
Example 2
The amorphous silicon film layer 2 is heated by infrared light until the temperature of the amorphous silicon film layer 2 reaches the preset temperature of 130 ℃ and is kept at the same time, and then a plurality of parts of the amorphous silicon film layer 2 are hydrogenated and crystallized by adopting 30W laser.
The remainder of example 2 corresponds to example 1.
Example 3
The amorphous silicon film layer 2 is heated by infrared light until the temperature of the amorphous silicon film layer 2 reaches the preset temperature of 170 ℃ and is kept warm, and then, a plurality of parts of the amorphous silicon film layer 2 are hydrogenated and crystallized by adopting 40W laser.
The remainder of example 3 corresponds to example 1.
Example 4
The amorphous silicon film layer 2 is heated by infrared light until the temperature of the amorphous silicon film layer 2 reaches the preset temperature of 200 ℃ and is kept at the same time, and then, a plurality of parts of the amorphous silicon film layer 2 are hydrogenated and crystallized by adopting 50W laser.
The remainder of example 4 corresponds to example 1.
Example 5
The amorphous silicon film layer 2 is heated by infrared light until the temperature of the amorphous silicon film layer reaches 230 ℃ which is preset, the amorphous silicon film layer is insulated, and then, a plurality of parts of the amorphous silicon film layer 2 are hydrogenated and crystallized by adopting laser with the power of 60W.
The remainder of example 5 corresponds to example 1.
Example 6
The amorphous silicon film layer 2 is heated by infrared light until the temperature of the amorphous silicon film layer 2 reaches 270 ℃ which is preset, heat preservation is carried out, and then, 70W laser is adopted to hydrogenate and crystallize a plurality of parts of the amorphous silicon film layer 2.
The remainder of example 6 corresponds to example 1.
Fig. 9 is a schematic view showing a hydrogen content and crystallization rate distribution of the first polysilicon portion according to each of the embodiments of the present invention. For the amorphous silicon film layer 2 formed by PECVD in examples 1 to 6, the wet etchant in examples 1 to 6 was directly used without laser crystallization and hydrogenation, and cleaning was performed under the same etching conditions, with the cleaning parameters shown in the second row of table 1 below. The first polysilicon portion 11 in the crystalline silicon film layer 1 formed after laser crystallization and hydrogenation in examples 1 to 6 was subjected to measurement of crystallization rate, hydrogen content, and the measurement results are shown in table 1 and fig. 9. In fig. 9, G1 represents example 1, G2 represents example 2, G3 represents example 3, G4 represents example 4, G5 represents example 5, and G6 represents example 6.
Table 1: partial process parameters and measurement results table
Referring to the second line of table 1, in examples 1 to 6, the amorphous silicon film layer 2 formed by PECVD was directly cleaned under the same etching conditions by using the wet etchant of examples 1 to 6 without performing laser crystallization and hydrogenation, and the cleaning was substantially completed for 6min to 12 min. As is clear from examples 1 to 6 and table 1, for the crystalline silicon film layer 1 formed after laser crystallization and hydrogenation of examples 1 to 6, the wet etchants of examples 1 to 6 were used, and the cleaning was performed under the same etching conditions for 15min to 20min, and the respective first polysilicon portions 11 were not substantially etched in the wet etching and remained substantially. The method has the specific reasons that in the method, through the auxiliary heating of infrared light and the matching of laser, the temperature of the auxiliary heating and the laser power are perfectly matched, the crystallization rate of the formed first polysilicon part 11 is proper, the slow release of hydrogen is facilitated, the slow release of hydrogen can be realized, the porosity can be reduced to a great extent, the first polysilicon part 11 with excellent film quality can be further obtained, under the condition that each first polysilicon part 11 is not provided with a mask layer, each first polysilicon part 11 with excellent film quality is basically not etched in an etchant and basically remains, the steps of arranging the mask layer on each first polysilicon part 11 and removing the mask layer are reduced, the process steps are fewer, and the production efficiency is higher.
As can be seen from table 1 and fig. 9, in the present invention, by the infrared light auxiliary heating and the laser light both being matched, the temperature of the auxiliary heating and the laser power both being perfectly matched, the crystallization rate of the formed first polysilicon portion 11 is maintained substantially stable, and the hydrogen content is slowly released without rising along with the rising of the laser power, thereby reducing the hydrogen content and also reducing the porosity.
It should be noted that, for simplicity of description, the method embodiments are shown as a series of acts, but it should be understood by those skilled in the art that the embodiments are not limited by the order of acts described, as some steps may occur in other orders or concurrently in accordance with the embodiments. Further, those skilled in the art will appreciate that the embodiments described in the specification are presently preferred, and that the acts referred to are not necessarily all required for the embodiments of the present application.
It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
From the above description of the embodiments, it will be clear to those skilled in the art that the above-described embodiment method may be implemented by means of software plus a necessary general hardware platform, but of course may also be implemented by means of hardware, but in many cases the former is a preferred embodiment. Based on such understanding, the technical solution of the present invention may be embodied essentially or in a part contributing to the prior art in the form of a software product stored in a storage medium (e.g. ROM/RAM, magnetic disk, optical disk) comprising instructions for causing a terminal (which may be a mobile phone, a computer, a server, an air conditioner, or a network device, etc.) to perform the method according to the embodiments of the present invention.
The embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and many forms may be made by those having ordinary skill in the art without departing from the spirit of the present invention and the scope of the claims, which are to be protected by the present invention.