阅读说明：本技术 一种晶体硅太阳能电池烧结方法 (Sintering method of crystalline silicon solar cell ) 是由 樊选东 于 2020-05-08 设计创作，主要内容包括：本发明涉及一种晶体硅太阳能电池烧结方法,包括以下步骤：S1：设置烧结炉传送履带匀速将印刷有铝浆和银浆的电池片送入烧结炉中,分别按照平台型和陡坡型烧结工艺曲线进行温度设置；S2：实际温度的测试：为准确掌握TPS烧结炉的实际烧结温度,实验借助温度测试仪获取炉内实际烧结温度,烧结炉内实际温度确实不等同于工艺设定温度,且差别较大,但与对应的温度设定基本吻合,陡坡型烧结曲线对应温度高于平台型烧结曲线的对应温度；陡坡型烧结曲线的温度持续上升,表明炉内温度持续升高,电池片充分加热,金属浆料与硅在液态时充分熔合、扩散,然后进入冷却区快速降温,最终形成良好的欧姆接触。(The invention relates to a crystalline silicon solar cell sintering method, which comprises the following steps: s1: arranging a sintering furnace conveying crawler belt to convey the battery piece printed with the aluminum paste and the silver paste into the sintering furnace at a constant speed, and setting the temperature according to a platform type sintering process curve and a steep slope type sintering process curve respectively; s2: testing of actual temperature: in order to accurately master the actual sintering temperature of the TPS sintering furnace, the actual sintering temperature in the furnace is obtained by an experiment with the help of a temperature tester, the actual temperature in the sintering furnace is not exactly equal to the process set temperature and has larger difference, but basically coincides with the corresponding temperature setting, and the corresponding temperature of the steep slope type sintering curve is higher than the corresponding temperature of the platform type sintering curve; the temperature of the steep-slope sintering curve continuously rises, which indicates that the temperature in the furnace continuously rises, the battery piece is fully heated, the metal slurry and the silicon are fully fused and diffused in a liquid state, and then the metal slurry and the silicon enter a cooling area to be rapidly cooled, and finally good ohmic contact is formed.)

1. A crystalline silicon solar cell sintering method is characterized by comprising the following steps:

s1: the method comprises the steps that a sintering furnace conveying crawler belt is arranged to convey battery pieces printed with aluminum paste and silver paste into a sintering furnace at a constant speed, temperature setting is carried out according to platform-type and abrupt-slope-type sintering process curves respectively, the temperature of a drying area is kept consistent in order to compare two sintering processes, the temperature of the sintering area is optimized and adjusted, particularly, the temperature of a rear area needs to be raised rapidly, and conversion from a platform type to an abrupt slope type is achieved; it should be noted that the first 7 temperature zones of the TPS chain sintering furnace only have the proportion of the output power of the upper lamp tube, and are related to the temperature setting of the corresponding temperature zone, which is not specifically specified herein; the temperature of the last 2 temperature zones is controlled by the proportion of the output power of the upper and lower lamp tubes together, and the front and the back of the battery piece are sintered in a coordinated manner and need to be set specifically;

s2: testing of actual temperature: because the set temperature of each temperature zone of the sintering furnace is different from the actual sintering temperature in the furnace to a certain extent, the set sintering temperature is considered to be only a surface phenomenon, and therefore the actual temperature in the furnace is known in the sintering process; in order to accurately master the actual sintering temperature of the TPS sintering furnace, the actual sintering temperature in the furnace is obtained by an experiment with the help of a temperature tester, the actual temperature in the sintering furnace is not exactly equal to the process set temperature and has larger difference, but basically coincides with the corresponding temperature setting, and the corresponding temperature of the steep slope type sintering curve is higher than the corresponding temperature of the platform type sintering curve; the temperature of the steep-slope sintering curve continuously rises, which indicates that the temperature in the furnace continuously rises, the battery piece is fully heated, the metal slurry and the silicon are fully fused and diffused in a liquid state, and then the metal slurry and the silicon enter a cooling area to be rapidly cooled, so that good ohmic contact is finally formed; the low temperature in the platform type sintering curve lasts for a long time, the temperature is suddenly raised until the back region, the actual temperature in the furnace does not reach the sintering temperature required by the process, so that the time of the battery piece in the high temperature region is short, the metal and the silicon cannot be fully fused, and good ohmic contact is formed; in addition, the sintering temperature is too low, so that the battery piece is not burnt, the short-circuit current is not ideal, the series resistance is too large, and finally the filling factor and the photoelectric conversion efficiency of the battery are influenced.

2. The method for sintering crystalline silicon solar cells according to claim 1, wherein the speed of the conveyor belt of the sintering furnace in step S1 is 609.6 cm/min.

Technical Field

The invention relates to the field of preparation methods of solar cells, in particular to a sintering method of a crystalline silicon solar cell.

Background

The sintering process is used as the last procedure in the production process of the crystalline silicon solar cell, relates to multiple disciplines such as optics, thermal science, semiconductor materials and the like, and mainly researches the fusion and diffusion problems between metal materials and silicon materials. Because the silver grid line and the aluminum Back Surface Field (BSF) of the positive electrode are thin and belong to different metal materials, the temperatures of alloy formed on the front surface and the back surface are greatly different. At present, sintering furnaces for industrially producing crystalline silicon cells are of the silver-aluminum co-firing type. Therefore, the sintering temperature and the sintering time are well held, so that good ohmic contact is formed between silicon and the metal slurry, and the method is a key technology for manufacturing a high-efficiency crystalline silicon battery. For the sintering process of the crystalline silicon solar cell, a kinetic model of the silver silicon sintering process is proposed and the correctness of the model is demonstrated in many literatures. In the process of industrial development of the crystalline silicon solar cell, a chain sintering furnace and a tube sintering furnace are the most mature sintering devices, wherein the sintering furnace of the Despatch company in the United states and the TPS chain sintering furnace of the Thermal Processing Solutions company in the United states occupy the international major market. In the aspect of sintering process, high-temperature rapid sintering is widely adopted, the process is simple, and the large-scale production is facilitated. The sintering curve generally accepted at present has a flat platform type and a steep slope type.

The rapid sintering process is to rapidly sinter the metal electrode printed on the surface of the cell slice in a sintering furnace to form good electric contact. After being dried and coke-removed, the metal slurry is contracted into a solid and adhered on a silicon chip, and the glass powder in the slurry has the function of corroding a silicon nitride film, so that the metal slurry is directly contacted with silicon. The so-called sintering process is a process in which a metal electrode and a silicon wafer are alloyed with each other, and when a metal electrode material and a silicon material are heated to a eutectic temperature, silicon atoms are diffused into the molten alloy material in a certain ratio. When the temperature is lowered, the system begins to cool to form a recrystallized layer, and the silicon atoms which have diffused into the metal electrode material are crystallized out again in a solid state, namely, an epitaxial layer grows on the contact interface of the metal and the crystal. If the epitaxial layer contains a sufficient amount of impurity components having the same conductivity type as the original crystalline material, the metal forms an ohmic contact with the crystalline silicon.

Because the quality of the sintering process directly affects the photoelectric conversion efficiency of the solar cell, the selection of a reasonable sintering process is particularly important. The temperature of the steep slope type curve rises slowly, the temperature of the platform type curve rises suddenly after being gentle, which sintering process curve is specifically selected, the characteristics and the process characteristics of the sintering furnace are bound to be combined, and the height of the square resistance after diffusion is particularly considered. The sintering furnace with the platform type sintering curve has the capability of quickly heating and maintaining constant temperature, and meanwhile, the high square resistance shallow junction structure is matched with the platform type sintering curve. For a TSP chain sintering furnace, the hardware performance of the furnace does not have certain advantages, and a platform type sintering curve is not necessarily an ideal choice.

Therefore, further improvements in the sintering method of crystalline silicon solar cells are needed.

Disclosure of Invention

The invention aims to provide a sintering method of a crystalline silicon solar cell, which can improve the photoelectric conversion rate of the solar cell.

2 batches of 200P-type monocrystalline silicon are selected, the size is 156mm x 156mm, the resistivity is 0.5-3.0 omega cm, the thickness is (200 +/-20) mu m, the block resistance after diffusion is (65 +/-3) omega, the minority carrier lifetime is more than 6 mu s, the thickness of the silicon nitride film is 80-85 nm, and the refractive index is 2.00-2.05. The sample is sintered after being cleaned, textured, diffused, bonded, etched by plasma, dephosphorized silicate glass (P SG), plated with an antireflection film (PEVCD), printed with an electrode, subjected to a back field and other conventional production process flows. Wherein, the back electrode printing adopts the Ru xing RX-61041 silver paste, the back electric field printing adopts the Ru xing RX-8252X aluminum paste, and the front electrode printing adopts the three-star PA-SF8521 silver paste.

In order to achieve the purpose of the invention, the invention provides a crystalline silicon solar cell sintering method, which comprises the following steps:

s1: the method comprises the steps that a sintering furnace conveying crawler belt is arranged to convey battery pieces printed with aluminum paste and silver paste into a sintering furnace at a constant speed, temperature setting is carried out according to platform-type and abrupt-slope-type sintering process curves respectively, the temperature of a drying area is kept consistent in order to compare two sintering processes, the temperature of the sintering area is optimized and adjusted, particularly, the temperature of a rear area needs to be raised rapidly, and conversion from a platform type to an abrupt slope type is achieved; it should be noted that the first 7 temperature zones of the TPS chain sintering furnace only have the proportion of the output power of the upper lamp tube, and are related to the temperature setting of the corresponding temperature zone, which is not specifically specified herein; the temperature of the last 2 temperature zones is controlled by the proportion of the output power of the upper and lower lamp tubes together, and the front and the back of the battery piece are sintered in a coordinated manner and need to be set specifically;

s2: testing of actual temperature: because the set temperature of each temperature zone of the sintering furnace is different from the actual sintering temperature in the furnace to a certain extent, the set sintering temperature is considered to be only a surface phenomenon, and therefore the actual temperature in the furnace is known in the sintering process; in order to accurately master the actual sintering temperature of the TPS sintering furnace, the actual sintering temperature in the furnace is obtained by an experiment with the help of a temperature tester, the actual temperature in the sintering furnace is not exactly equal to the process set temperature and has larger difference, but basically coincides with the corresponding temperature setting, and the corresponding temperature of the steep slope type sintering curve is higher than the corresponding temperature of the platform type sintering curve; the temperature of the steep-slope sintering curve continuously rises, which indicates that the temperature in the furnace continuously rises, the battery piece is fully heated, the metal slurry and the silicon are fully fused and diffused in a liquid state, and then the metal slurry and the silicon enter a cooling area to be rapidly cooled, so that good ohmic contact is finally formed; the low temperature in the platform type sintering curve lasts for a long time, the temperature is suddenly raised until the back region, the actual temperature in the furnace does not reach the sintering temperature required by the process, so that the time of the battery piece in the high temperature region is short, the metal and the silicon cannot be fully fused, and good ohmic contact is formed; in addition, the sintering temperature is too low, so that the battery piece is not burnt, the short-circuit current is not ideal, the series resistance is too large, and finally the filling factor and the photoelectric conversion efficiency of the battery are influenced.

Further, the sintering furnace conveying crawler speed in step S1 is 609.6 cm/min.

Compared with the prior art, the sintering method of the crystalline silicon solar cell has the following advantages:

the steep-slope type sintering process can enable the grid line on the front side and the electric field on the back side of the solar cell to form good ohmic contact with silicon, reduce the contact resistance of the silicon with silver paste and aluminum paste, prolong the service life of minority carriers, improve the filling factor of the cell, enhance the current collecting capacity of the grid line on the front side of the cell, and finally improve the photoelectric conversion efficiency to a certain extent.

Detailed Description

The present invention will be further described with reference to the following specific examples.

2 batches of 200P-type monocrystalline silicon are selected, the size is 156mm x 156mm, the resistivity is 0.5-3.0 omega cm, the thickness is (200 +/-20) mu m, the block resistance after diffusion is (65 +/-3) omega, the minority carrier lifetime is more than 6 mu s, the thickness of the silicon nitride film is 80-85 nm, and the refractive index is 2.00-2.05. The sample is sintered after being cleaned, textured, diffused, bonded, etched by plasma, dephosphorized silicate glass (P SG), plated with an antireflection film (PEVCD), printed with an electrode, subjected to a back field and other conventional production process flows. Wherein, the back electrode printing adopts the Ru xing RX-61041 silver paste, the back electric field printing adopts the Ru xing RX-8252X aluminum paste, and the front electrode printing adopts the three-star PA-SF8521 silver paste.

The method is characterized in that a sintering furnace conveying crawler is arranged to uniformly convey the battery piece printed with the aluminum paste and the silver paste into the sintering furnace at a speed of 609.6cm/min, temperature setting is carried out according to a platform type sintering process curve and a steep slope type sintering process curve respectively, the temperature of a drying area is kept consistent in order to compare two sintering processes, the temperature of the sintering area is optimized and adjusted only, particularly, the temperature of a rear area needs to be rapidly increased, and the conversion from the platform type to the steep slope type is realized. It should be noted that the first 7 temperature zones of the TPS chain sintering furnace only have the proportion of the output power of the upper lamp tube, and are related to the temperature setting of the corresponding temperature zone, which is not specifically specified herein; the temperature of the last 2 temperature zones is controlled by the proportion of the output power of the upper lamp tube and the lower lamp tube together, the front surface and the back surface of the battery piece are sintered in a coordinated manner, and the temperature needs to be set specifically.

Testing of actual temperature: because the set temperature of each temperature zone of the sintering furnace is different from the actual sintering temperature in the furnace to a certain extent, the set sintering temperature is considered to be only a surface phenomenon, and therefore the actual temperature in the furnace is known in the sintering process. In order to accurately master the actual sintering temperature of the TPS sintering furnace, the actual sintering temperature in the furnace is obtained by a temperature tester in an experiment, the actual temperature in the sintering furnace is not exactly equal to the process set temperature and has larger difference, but basically coincides with the corresponding temperature set, and the corresponding temperature of the steep slope type sintering curve is higher than the corresponding temperature of the platform type sintering curve. The temperature of the steep-slope sintering curve continuously rises, which indicates that the temperature in the furnace continuously rises, the battery piece is fully heated, the metal slurry and the silicon are fully fused and diffused in a liquid state, and then the metal slurry and the silicon enter a cooling area to be rapidly cooled, and finally good ohmic contact is formed. And the low temperature in the platform type sintering curve lasts for a longer time, the temperature is not raised suddenly until the back region, the actual temperature in the furnace does not reach the sintering temperature required by the process, so that the time of the battery piece in the high temperature region is shorter, the metal and the silicon cannot be fused fully, and good ohmic contact is formed. In addition, the sintering temperature is too low, so that the battery piece is not burnt, the short-circuit current is not ideal, the series resistance is too large, and finally the filling factor and the photoelectric conversion efficiency of the battery are influenced.

For the TPS chain type sintering furnace, a steep slope type sintering process is adopted, and various electrical performance parameters of the battery piece are superior to those of a platform type sintering process. Wherein, open circuit voltage, short-circuit current only have promotion of 1mA and 4mA respectively, promote unobvious. The most obvious improvement is the series resistance, the parallel resistance and the filling factor, the series resistance is reduced by 0.49m omega, the parallel resistance is increased by 153.79 omega, the filling factor is increased by 0.46 percent, the photoelectric conversion efficiency of the cell is improved to a certain extent finally, the photoelectric conversion efficiency is improved from 18.70 percent to 18.81 percent, the photoelectric conversion efficiency is improved by 0.14 percent, and the average power of the cell is improved by 0.035W. The abrupt slope type sintering temperature is high, the junction depth of the front electrode and the aluminum back field is increased after sintering, the effective diffusion length of minority carriers is increased, the recombination rate of the minority carriers is reduced, the service life of the minority carriers is prolonged, and the short-circuit current is improved. Meanwhile, the good ohmic contact reduces the series resistance of the battery and increases the parallel resistance, thereby effectively improving the filling factor and obtaining higher photoelectric conversion rate.

Through experimental comparison and data analysis, the steep slope type sintering process is adopted, and all electrical performance parameters of the battery piece are superior to those of the platform type sintering process. The steep-slope sintering process can enable the grid line on the front side and the electric field on the back side of the solar cell to form good ohmic contact with silicon, reduce the contact resistance of the silicon with silver paste and aluminum paste, prolong the service life of minority carriers, improve the filling factor of the cell, enhance the current collecting capacity of the grid line on the front side of the cell, and finally improve the photoelectric conversion efficiency to a certain extent. Meanwhile, the steep-slope sintering process is more suitable for the TPS sintering furnace, and certain reference is provided for the research on the matching of the sintering process and equipment in industrial production.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of this patent application, "plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In this specification, unless expressly stated or limited otherwise, the terms "mounted," "connected," and "fixed" are to be construed broadly and may, for example, be fixedly connected, detachably connected, or integral to one another; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present specification can be understood by those of ordinary skill in the art as appropriate.

In this specification, unless explicitly stated or limited otherwise, a first feature may be "on" or "under" a second feature such that the first and second features are in direct contact, or the first and second features are in indirect contact via an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.