KR100994182B1 - Method for forming selective emitter of solar cell and diffusion apparatus for forming the selective emitter - Google Patents

Abstract

The present invention relates to a method of forming a selective emitter of a solar cell and a diffusion apparatus for the same, comprising the steps of: organizing the surface of the silicon substrate by etching the silicon substrate; Coating an impurity solution on the surface of the silicon substrate; Injecting first thermal energy over the entire surface of the silicon substrate coated with the impurity solution; And injecting the second heat energy by irradiating laser light to a portion of the surface of the silicon substrate coated with the impurity solution while the first heat energy is injected to the entire surface of the silicon substrate. The temperature by the second thermal energy is the temperature by the first thermal energy and the laser light. The impurity ions diffuse into the silicon substrate by the first thermal energy to form an emitter layer, and the impurity ions are emitted by the second thermal energy. It is further diffused within some regions of the layer to form a selective emitter layer. According to the present invention, high productivity in mass production and high photoelectric conversion efficiency of a solar cell can be obtained.

Solar cell, emitter layer, silicon, diffusion

Description

Method for forming selective emitter of solar cell and diffusion apparatus for same

The present invention relates to a method for manufacturing a solar cell, and more particularly, to a method for forming a selective emitter of a solar cell and a diffusion apparatus for the same.

Recently, as the environmental pollution problem becomes serious, researches on renewable energy that can reduce environmental pollution have been actively conducted. Among renewable energy, in particular, attention is focused on solar cells that can produce electrical energy using solar energy. However, in order for a solar cell to be applied to an actual industry, the photoelectric conversion efficiency of the solar cell must be high and its manufacturing price must be low.

In terms of photoelectric conversion efficiency, the theoretical limit efficiency of silicon solar cells is not so high, so there is a limit to increase the photoelectric conversion efficiency of actual solar cells. It is reported to have.

However, when mass production of solar cells, the average photoelectric conversion efficiency of solar cells is actually difficult to exceed 17%. Therefore, there is a demand for a high efficiency production method that can be applied in an automated mass production process line of 30MW or more per year.

Accordingly, the technical problem to be achieved by the present invention is a selective emitter of a substrate using a laser while injecting the first thermal energy into the entire substrate using a non-contact heater of a radiation method during a heat treatment process for diffusion of impurities. The present invention provides a method for forming a selective emitter of a solar cell by injecting second thermal energy into a partial region or a plurality of predetermined regions for formation, thereby increasing the photoelectric conversion efficiency of the solar cell even in mass production.

Another technical problem to be achieved by the present invention is a part of forming a selective emitter of a substrate by using a laser while injecting first thermal energy into the entire substrate using a non-contact heater of a radiation method during a heat treatment process for diffusion of impurities. The present invention provides a diffusion device for forming a selective emitter of a solar cell by injecting second thermal energy into a region or a plurality of set regions, thereby improving photoelectric conversion efficiency of the solar cell even in mass production.

According to an aspect of the present invention, there is provided a method of forming a selective emitter of a solar cell, comprising: etching a silicon substrate to organize a surface of the silicon substrate; Coating an impurity solution on the surface of the silicon substrate; Injecting first thermal energy over the entire surface of the silicon substrate coated with the impurity solution; And injecting the second heat energy by irradiating laser light to a portion of the surface of the silicon substrate coated with the impurity solution while the first heat energy is injected to the entire surface of the silicon substrate.

The temperature by the second thermal energy is the temperature by the first thermal energy and the laser light. The impurity ions diffuse into the silicon substrate by the first thermal energy to form an emitter layer, and the impurity ions are emitted by the second thermal energy. It is further diffused within some regions of the layer to form a selective emitter layer.

According to another aspect of the present invention, there is provided a method of forming an emitter of a solar cell, the method including: etching a silicon substrate to organize a surface of the silicon substrate; First coating an impurity solution on the surface of the silicon substrate; Second coating the impurity solution on a portion of the surface of the silicon substrate on which the impurity solution is first coated; Injecting first thermal energy over the entire surface of the silicon substrate; And injecting the second thermal energy by irradiating a laser light to the surface of the second substrate on which the impurity solution is coated while the first thermal energy is injected to the entire surface of the silicon substrate.

The temperature by the second thermal energy is the temperature by the first thermal energy and the laser light. The impurity ions diffuse into the silicon substrate by the first thermal energy to form an emitter layer, and the impurity ions are emitted by the second thermal energy. It is further diffused within some regions of the layer to form a selective emitter layer.

According to still another aspect of the present invention, there is provided a method of forming an emitter of a solar cell, the method including: etching a silicon substrate to organize a surface of the silicon substrate; Coating an impurity solution on the surface of the silicon substrate; Injecting first thermal energy over the entire surface of the silicon substrate coated with the impurity solution; And injecting the second thermal energy by irradiating laser light to a plurality of predetermined regions of the surface of the silicon substrate coated with the impurity solution while the first thermal energy is injected into the entire surface of the silicon substrate.

The temperature by the second thermal energy is the temperature by the first thermal energy and the laser light. The impurity ions diffuse into the silicon substrate by the first thermal energy to form an emitter layer, and the impurity ions are emitted by the second thermal energy. It is further diffused within some regions of the layer to form a selective emitter layer.

According to still another aspect of the present invention, there is provided a method of forming an emitter of a solar cell, the method comprising: etching a silicon substrate to organize a surface of the silicon substrate; First coating an impurity solution on the surface of the silicon substrate; Second coating the impurity solution on the plurality of predetermined regions of the surface of the silicon substrate, on which the impurity solution is first coated; Injecting first thermal energy over the entire surface of the silicon substrate; And injecting the second thermal energy by irradiating a laser light to the surface of the second substrate on which the impurity solution is coated while the first thermal energy is injected to the entire surface of the silicon substrate.

The temperature by the second thermal energy is the temperature by the first thermal energy and the laser light. The impurity ions diffuse into the silicon substrate by the first thermal energy to form an emitter layer, and the impurity ions are emitted by the second thermal energy. It is further diffused within some regions of the layer to form a selective emitter layer.

Diffusion apparatus for selective emitter formation of a solar cell according to the present invention for achieving the above another technical problem includes a diffusion chamber, a transfer belt, a rotating roller, a heater, and a laser generator. The diffusion chamber has an inlet formed on one side and an outlet formed on the other side. The transfer belt is mounted on a silicon substrate coated with an impurity solution on a surface organized by an etching process. The rotary roller moves the transfer belt such that the silicon substrate mounted on the transfer belt is transferred at a set speed from the inlet to the outlet of the diffusion chamber.

The heater is installed to surround the transfer belt at a predetermined distance from the transfer belt within the diffusion chamber, and injects first thermal energy to the entire surface of the silicon substrate transferred inside the diffusion chamber. The laser generator penetrates one side of the heater in the diffusion chamber and irradiates laser light to a portion of the surface of the silicon substrate through a plurality of tubes installed to face the transfer belt.

The first thermal energy diffuses the impurity ions into the silicon substrate to form an emitter layer, and the second thermal energy further diffuses the impurity ions into a portion of the emitter layer to form a selective emitter layer. The temperature by the second thermal energy is the temperature by the first thermal energy and the laser light.

As described above, the method of forming a selective emitter of a solar cell according to the present invention and a diffusion apparatus therefor injects the first thermal energy to the entire substrate using a non-contact heater of the radiation method during the heat treatment process for diffusion of impurities. In the meantime, since the second thermal energy is injected into the partial region for the selective emitter formation of the substrate using a laser, high photoelectric conversion efficiency of the solar cell can be obtained. In addition, since the method of forming a selective emitter of the solar cell according to the present invention and a diffusion apparatus therefor may be applied to an inline type automated production equipment capable of mass production, high productivity may be realized in mass production.

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the present invention. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms, only the embodiments are to make the disclosure of the present invention complete and to those skilled in the art the scope of the invention It is provided for complete information.

1 is a flowchart illustrating a process of forming a selective emitter of a solar cell according to a first embodiment of the present invention. 2A to 2E are cross-sectional views of a substrate for describing a process of forming a selective emitter of the solar cell shown in FIG. 1.

First, the silicon substrate 111 is etched to organize the surface of the silicon substrate 111 (step 1001). In step 1001, irregularities are formed on the surface of the silicon substrate 110 by dry or wet etching. Although not shown in detail in FIG. 2A, very fine irregularities are formed on the surface of the silicon substrate 111. Here, the silicon substrate 111 may be a p-type substrate doped with boron (B) ions.

Thereafter, the impurity solution 112 is sprayed onto the textured surface of the silicon substrate 111 to coat the impurity solution 112 on the surface of the silicon substrate 111 as shown in FIG. 2B. (Step 1002). In this case, the impurity solution 112 may be a solution containing a phosphorus (P) component. In addition, the impurity solution 112 may include POCl ₃ (phosphorus oxychloride).

Next, as shown in FIG. 2C, the first thermal energy E1 is injected into the entire surface of the silicon substrate 111 coated with the impurity solution 112 (step 1003). Step 1003 may be performed by a radiating non-contact heater 240 of the diffusion device 200 (see FIG. 5). The temperature range by the first thermal energy may be set to 830 ~ 900 ℃. As a result of the execution of step 1003, impurity ions are diffused into the silicon substrate 111 by the first thermal energy E1, so that the emitter layer 113 is formed as shown in FIG. 2D. The emitter layer 113 corresponds to the n layer doped with phosphorus (P) ions.

While step 1003 is performed, i.e., the first thermal energy E1 is injected into the entire surface of the silicon substrate 111, a laser beam is applied to a part of the surface of the silicon substrate 111 coated with the impurity solution 112. The second thermal energy E2 is injected by irradiating the light L (step 1004). Step 1004 may be performed by the radiated non-contact heater 240 and the laser generator 250 of the diffusion device 200. The range of temperature by the second thermal energy may be set to 830 ~ 1,070 ℃. The temperature by the second thermal energy E2 is the temperature by the first thermal energy E1 and the laser light.

As a result of the execution of step 1004, the impurity ions are further diffused into the partial region of the emitter layer 113 by the second thermal energy E2 to form the selective emitter layer 114, as shown in FIG. 2D. The selective emitter layer 114 corresponds to an n + layer doped with phosphorus (P) ions more than the emitter layer 113. A portion of the region where the selective emitter layer is formed corresponds to a region where the metal electrode 117 (see FIG. 4) is deposited.

Here, when the second thermal energy E2 having a higher temperature than the temperature caused by the first thermal energy E1 is injected into the silicon substrate 110, the principle of better diffusion of impurity ions will be described. .

The diffusion of atoms in a solid occurs from a high concentration region to a low concentration region when the concentration of atoms is uneven, until the concentration of atoms is uniform throughout the solid by thermal motion. The equation which is the basis of the diffusion phenomenon according to the first law of the peak that the diffusion amount is proportional to the concentration gradient is as follows.

In Equation 1, J represents the diffusion amount (ie, the amount of diffusion material passing through the unit area), and D is the diffusion coefficient. In addition, C represents the concentration of the diffusion material, x represents the moving distance of the diffusion material on the Y axis.

At this time, the diffusion coefficient rapidly increases as the temperature is increased, and is expressed as a function below.

In Equation 2, D ₀ is a temperature insensitive constant, k is a Boltzmann constant, and T is a temperature. Q is called activation energy and has a value of about 2 to 5 eV depending on the substance. Graphs showing changes in diffusion coefficient with temperature based on Equation 2 are shown in Figs. 9A and 9B. For example, when Q = 2 eV and D ₀ = 8 x 10 ^-5 m 2 / sec, D ° 10 ^-38 m 2 / sec at 300 ° K, but at T = 1500 ° K, D = 10 ^-11 It increases sharply to m 2 / sec.

Therefore, as shown in FIG. 9A, assuming that two energy E1 and E2 of different temperatures are respectively injected to two points of the silicon substrate, the diffusion coefficients for the two regions are different as D1 and D2 (that is, the temperature is Since the diffusion coefficient increases as the value increases, the degree of arrival of impurities is changed, so that the emitter layer 113 and the selective emitter layer 114 are divided as shown in FIG. 2D.

The graph shown in FIG. 9A can be represented again as a graph showing the relationship between the log function and the inverse of the temperature, as shown in FIG. 9B. Equation (2) is represented by a logarithmic function corresponding to the graph shown in FIG. 9B.

Meanwhile, in steps 1003 and 1004, a PSG (phosphorus silicate glass) 115 layer may be further formed on the surface of the silicon substrate 111 on which the emitter layer 113 and the optional emitter layer 114 are formed. Thus, after step 1004, the PSG layer 115 formed on the surface of the silicon substrate 111 including the emitter layer 113 and the optional emitter layer 114 is removed (step 1005). In step 1005, the silicon substrate 111 may be immersed in a 5% NF solution to remove the PSG layer 115. Thereafter, the silicon substrate 111 is washed with deionized water. As a result, as shown in FIG. 2E, a silicon substrate 111 comprising an emitter layer 113 and an optional emitter layer 114 is obtained.

As described above, according to the selective emitter forming process according to the present invention, high productivity of the solar cell and high photoelectric conversion efficiency of 18% or more can be obtained. In addition, the selective emitter forming method according to the present invention can be applied to the automated production equipment of the in-line type capable of mass production.

3 is a cross-sectional view illustrating an example of a solar cell including a selective emitter layer formed according to a selective emitter forming process of the solar cell according to the first embodiment of the present invention. An anti-reflection film 116 is formed on the upper surface of the silicon substrate 111 shown in FIG. 2E. The anti-reflection film 116 functions to reduce reflection of sunlight and to increase absorption of sunlight.

Thereafter, the metal electrode 117 made of Ag (−) material is printed on the anti-reflection film 116 on the selective emitter layer 113 by a printing press, and a drying and firing process is performed. Similarly, the bottom surface of the silicon substrate 111 is also printed with a metal electrode 118 made of AgAl for busbars by a printing machine, and a drying and firing process is performed. In addition, a metal electrode 119 of Al (+) material is printed by a printing machine, and a drying and firing process is performed.

By the drying and firing process, as shown in FIG. 3, the metal electrode 117 diffused through the upper anti-reflection film 116 makes ohmic contact with the selective emitter layer 114, and the metal on the back side. The electrode 118 is in ohmic contact with the silicon substrate 111.

4 is a plan view illustrating an example of a solar cell including a selective emitter layer formed according to a selective emitter forming process of the solar cell according to the first embodiment of the present invention. The metal electrode 117 is formed through the anti-reflection film 116 and is in ohmic contact with the selective emitter layer. Further, finger electrodes 121 are formed on both sides of the metal electrode 117. An optional emitter layer 114 is formed under the metal electrode 117.

5 is a longitudinal cross-sectional view of a diffusion device for forming a selective emitter of a solar cell according to an embodiment of the present invention. The diffusion device 200 includes a diffusion chamber 210, a transfer belt 220, a rotating roller 230, a heater 240, a laser generator 250, and an exhaust pump. (pump) 260. An inlet 211 is formed at one side of the diffusion chamber 210, and an outlet 212 is formed at the other side of the diffusion chamber 210.

The transfer belt 220 is mounted with a silicon substrate 100 sprayed with an impurity solution 220 on a surface organized by an etching process. The plurality of silicon substrates 100 may be mounted on the transfer belt 220 at predetermined intervals. The transfer belt 220 may be formed of a metal mesh.

The rotary roller 230 moves the transfer belt 220 so that the silicon substrate 100 mounted on the transfer belt 220 is transferred at the set speed from the inlet 211 to the outlet 212 of the diffusion chamber 210. .

The heater 240 is installed in the diffusion chamber 210 to surround the transfer belt 220 at a predetermined interval from the transfer belt 220, as shown in FIG. 6. 6 is a cross-sectional view taken along the dashed line "A" of the diffusion device shown in FIG. The heater 240 injects the first thermal energy E1 to the entire surface of the silicon substrate 100 transferred into the diffusion chamber 210. The heater 240 may include a non-contact heater of a radiation method. By the first thermal energy E1, impurity ions are diffused into the silicon substrate 100 to form an emitter layer.

The laser generator 250 irradiates the laser light L to a portion of the surface of the silicon substrate 100 through the plurality of tubes 251. As a result, the second thermal energy E2 is injected into a part of the surface of the silicon substrate 100 by the first thermal energy E1 and the laser light L by the heater 240. As shown in FIG. 7, the laser light L is irradiated to the region where the metal electrode is to be formed in the silicon substrate 100. FIG. 7 is a plan view showing an example of the diffusion device as seen from above the transfer belt after cutting the diffusion device shown in FIG. 6 along the dotted line “B”. FIG. By the second thermal energy E2, impurity ions are further diffused in some regions of the emitter layer to form a selective emitter layer.

In FIG. 7, the silicon substrate 100 is mounted as a single line on the conveyance belt 220 as an example. However, as shown in FIG. 8, the silicon as a plurality of lines on the conveyance belt 220 is illustrated. The substrate 100 may be mounted. FIG. 8 is a plan view showing another example of the diffusion device as seen from above the transfer belt after cutting the diffusion device shown in FIG. 6 along the dotted line "B".

Meanwhile, as shown in FIG. 6, the plurality of tubes 251 penetrates one side of the heater 240 in the diffusion chamber 210, and one end of each of the plurality of tubes 251 is connected to the transfer belt 220. It is installed to face each other. The exhaust pump 260 penetrates the other side of the heater 240 and extends the outside of the diffusion chamber 210 through the exhaust pipe 261 installed to extend outside of the diffusion chamber 210 to the outside.

10 is a flowchart illustrating a process of forming a selective emitter of a solar cell according to a second embodiment of the present invention. 11A through 11D are cross-sectional views of a substrate for describing a process of forming a selective emitter of the solar cell illustrated in FIG. 10.

First, the silicon substrate 111 is etched to organize the surface of the silicon substrate 111 (step 1101). The processing of the silicon substrate 111 in step 1101 is the same as that of step 1001 described above with reference to FIG. 1.

Thereafter, the impurity solution 112 is sprayed onto the textured surface of the silicon substrate 111, and as shown in FIG. 2B, the impurity solution 112 is first sprayed onto the surface of the silicon substrate 111. Coating (step 1102). The processing of the silicon substrate 111 in step 1102 is the same as in step 1002 described above.

As shown in FIG. 11A, a second coating of the impurity solution 112 ′ is performed on a portion of the surface of the silicon substrate 111 coated with the impurity solution 112 (step 1103). At this time, the impurity solution 112 ′ is second coated on the silicon substrate 111 by the coating apparatus 280. At the bottom of the coating apparatus 280, as shown in FIG. 11B, when the silicon substrate 111 coated with the impurity solution 112 is moved, the impurity solution 112 ′ is coated only in the region 101. FIG. 11C is a cross-sectional view taken along the dotted line C of the silicon substrate 111 shown in FIG. 11B.

Next, as shown in FIG. 11D, the first thermal energy E1 is injected into the entire surface of the silicon substrate 111 coated with the impurity solutions 112 and 112 ′ (step 1104). The process of processing the silicon substrate 111 in step 1104 is the same as step 1003 described above with reference to FIG. 1. As a result of the execution of step 1104, impurity ions are diffused into the silicon substrate 111 by the first thermal energy E1, so that the emitter layer 113 is formed as shown in FIG. 2D. The emitter layer 113 corresponds to the n layer doped with phosphorus (P) ions.

While step 1104 is executed, that is, while the first thermal energy E1 is injected into the entire surface of the silicon substrate 111, the silicon substrate coated with the impurity solution 112 ′ is second coated, as shown in FIG. 11D. The second heat energy E2 is injected by irradiating a laser light L onto the surface of the 111 (step 1105). The processing of the silicon substrate 111 in step 1105 is the same as step 1004 described above with reference to FIG. 1. The range of temperature by the second thermal energy may be set to 830 ~ 1,070 ℃. The temperature by the second thermal energy E2 is the temperature by the first thermal energy E1 and the laser light.

As a result of the execution of step 1105, the impurity ions are further diffused into some regions of the emitter layer 113 by the second thermal energy E2, thereby forming the selective emitter layer 114, as shown in FIG. 2D. The selective emitter layer 114 corresponds to an n + layer doped with phosphorus (P) ions more than the emitter layer 113. A portion of the region where the selective emitter layer is formed corresponds to a region where the metal electrode 117 (see FIG. 4) is deposited.

Meanwhile, in steps 1104 and 1105, a PSG layer may be further formed on the surface of the silicon substrate 111 on which the emitter layer 113 and the optional emitter layer 114 are formed. Thus, after step 1105, the PSG layer 115 formed on the surface of the silicon substrate 111 including the emitter layer 113 and the optional emitter layer 114 is removed (step 1106). The processing of the silicon substrate 111 in step 1106 is the same as in step 1005 described above. As a result, as shown in FIG. 2E, a silicon substrate 111 comprising an emitter layer 113 and an optional emitter layer 114 is obtained.

As described above, in steps 1102 and 1103, since the impurity solution 112 is coated twice in the region where the selective emitter layer 114 is to be formed, when the second thermal energy E2 is injected into the silicon substrate 111. A high quality selective emitter layer 114 can be formed.

12 is a flowchart illustrating a process of forming a selective emitter of a solar cell according to a third embodiment of the present invention. 13A to 13F are cross-sectional views of a substrate for describing a process of forming a selective emitter of the solar cell illustrated in FIG. 12.

First, the silicon substrate 311 is etched to organize the surface of the silicon substrate 311 (step 1201). The processing of the silicon substrate 111 in step 1201 is the same as that of step 1001 described above with reference to FIG. 1.

Thereafter, an impurity solution 312 is sprayed onto the textured surface of the silicon substrate 311, and the impurity solution 312 is applied to the surface of the silicon substrate 311 as shown in FIGS. 13A and 13B. Coating (step 1202). The processing of the silicon substrate 311 in step 1202 is the same as that of step 1002 described above.

Next, as shown in FIG. 13C, the first thermal energy E1 is injected into the entire surface of the silicon substrate 311 coated with the impurity solution 312 (step 1203). Step 1203 may be performed by the radiating non-contact heater 240 of the diffusion device 200 (see FIG. 5). The temperature range by the first thermal energy may be set to 830 ~ 900 ℃. As a result of the execution of step 1203, impurity ions are diffused into the silicon substrate 311 by the first thermal energy E1, so that the emitter layer 313 is formed as shown in Fig. 13E. The emitter layer 313 corresponds to the n layer doped with phosphorus (P) ions.

While step 1203 is executed, that is, while the first thermal energy E1 is injected into the entire surface of the silicon substrate 311, the silicon substrate 311 coated with the impurity solution 312, as shown in FIG. 13C. The second thermal energy E2 is injected by irradiating laser light L to the plurality of set areas 301 to 303 (see FIG. 13D) of the surface of the surface (step 1204). Step 1204 may be performed by the radiated non-contact heater 240 and the laser generator 250 of the diffusion apparatus 200. The range of temperature by the second thermal energy may be set to 830 ~ 1,070 ℃. The temperature by the second thermal energy E2 is the temperature by the first thermal energy E1 and the laser light.

In step 1204, as shown in FIG. 16, a plurality of lines of laser light L may be irradiated to the plurality of set regions 301 to 303 on the surface of the silicon substrate 311, respectively. The laser generator 250 used in step 1204 may include a plurality of lines of tubes 251, as shown in FIG. 17. In FIG. 16, the silicon substrate 311 is mounted as a single line on the transfer belt 220 as an example. However, as shown in FIG. 18, a plurality of lines on the transfer belt 220 may be used. The substrate 311 may be mounted. FIG. 18 is a plan view showing still another example of the diffusing device viewed from above the conveying belt after cutting the diffusing device shown in FIG. 6 along the dotted line “B”.

As a result of the execution of step 1204, the impurity ions are further diffused into the partial region of the emitter layer 313 by the second thermal energy E2, thereby forming the selective emitter layer 314 as shown in FIG. 13E. The selective emitter layer 314 corresponds to an n + layer doped with phosphorus (P) ions more than the emitter layer 313. Among the regions where the selective emitter layer 314 is formed, at least one region corresponds to a region where the metal electrode 317 (see FIG. 14) is not formed, and the remaining region corresponds to a region where the metal electrode 317 is formed.

Meanwhile, in steps 1203 and 1204, a PSG layer may be further formed on the surface of the silicon substrate 311 on which the emitter layer 313 and the optional emitter layer 314 are formed. Thus, after step 1204, the PSG layer 315 formed on the surface of the silicon substrate 311 including the emitter layer 313 and the optional emitter layer 314 is removed (step 1205). The processing of the silicon substrate 311 in step 1205 is the same as that of step 1005 described above. As a result, as shown in FIG. 13F, a silicon substrate 311 is obtained that includes an emitter layer 313 and an optional emitter layer 314.

14 is a cross-sectional view illustrating an example of a solar cell including a selective emitter layer formed according to a selective emitter forming process of a solar cell according to a third embodiment of the present invention. An antireflection film 316 is formed on the upper surface of the silicon substrate 311 shown in FIG. 13F. The anti-reflection film 316 functions to reduce reflection of sunlight and increase absorption of sunlight.

Thereafter, the Ag (−) material is formed by a printing press on the anti-reflection film 316 on the selective emitter layer 314 formed at a distance from both sides of the selective emitter layer 314 formed at the center of the silicon substrate 311. Metal electrode 317 is printed, and a drying and firing process is performed. Similarly, on the bottom of the silicon substrate 311, a metal electrode 318 made of AgAl material for busbars is printed by a printer, and a drying and firing process is performed. In addition, a metal electrode 319 of Al (+) material is printed by a printing machine, and a drying and firing process is performed.

By the drying and firing process, as shown in FIG. 14, the metal electrode 317 diffused through the upper anti-reflection film 316 makes ohmic contact with the selective emitter layer 314, and the metal on the back side. The electrode 318 makes ohmic contact with the silicon substrate 311.

FIG. 15 is a plan view illustrating an example of a solar cell including a selective emitter layer formed according to a process of forming a selective emitter of a solar cell according to a third exemplary embodiment of the present invention. The metal electrode 317 is formed through the anti-reflection film 316 and is in ohmic contact with the selective emitter layer. Further, finger electrodes 321 are formed on both sides of the metal electrode 317. An optional emitter layer 314 is formed under the metal electrode 317. Meanwhile, an optional emitter layer 314 is formed in a portion of the lower portion of the finger electrodes 321 formed between the metal electrodes 317. As the number of selective emitter layers 314 formed on the silicon substrate 311 increases, the photoelectric conversion efficiency of the solar cell may increase.

19 is a flowchart illustrating a process of forming a selective emitter of a solar cell according to a fourth embodiment of the present invention. 20A to 20D are cross-sectional views of a substrate for describing a process of forming a selective emitter of the solar cell illustrated in FIG. 19.

First, the silicon substrate 311 is etched to organize the surface of the silicon substrate 311 (step 1301). The processing of the silicon substrate 311 in step 1301 is the same as step 1001 described above with reference to FIG. 1.

Thereafter, the impurity solution 312 is sprayed onto the textured surface of the silicon substrate 311, and the impurity solution 312 is first sprayed onto the surface of the silicon substrate 311 as shown in FIG. 13B. Coating (step 1302). The processing of the silicon substrate 311 in step 1302 is the same as that of step 1002 described above.

As shown in FIG. 20A, a second coating of the impurity solution 312 ′ is applied to a plurality of predetermined regions 301 to 303 (see FIG. 20C) of the surface of the silicon substrate 311 coated with the impurity solution 312. (Step 1303). At this time, the impurity solution 312 ′ is second coated on the silicon substrate 311 by the coating apparatus 280. At the bottom of the coating apparatus 280, as shown in FIG. 20C, when the silicon substrate 311 coated with the impurity solution 312 is moved, only the regions 301 to 303 are coated with the impurity solution 312 ′. .

Next, as shown in FIG. 20D, the first thermal energy E1 is injected into the entire surface of the silicon substrate 311 coated with the impurity solutions 312 and 312 ′ (step 1304). The process of processing the silicon substrate 311 in step 1304 is the same as step 1003 described above with reference to FIG. 1. As a result of the execution of step 1304, impurity ions are diffused into the silicon substrate 311 by the first thermal energy E1, so that the emitter layer 313 is formed as shown in Fig. 13E. The emitter layer 313 corresponds to the n layer doped with phosphorus (P) ions.

While step 1304 is executed, that is, while the first thermal energy E1 is injected into the entire surface of the silicon substrate 111, as shown in FIG. 20D, the silicon substrate coated with the impurity solution 312 ′ is second-coated. The second thermal energy E2 is injected by irradiating a laser light L onto the surface of the 311 (step 1305). The processing of the silicon substrate 311 in step 1305 is the same as step 1004 described above with reference to FIG. 1. The range of temperature by the second thermal energy may be set to 830 ~ 1,070 ℃. The temperature by the second thermal energy E2 is the temperature by the first thermal energy E1 and the laser light.

As a result of the execution of step 1305, the impurity ions are further diffused into the partial region of the emitter layer 313 by the second thermal energy E2, thereby forming the selective emitter layer 314, as shown in FIG. 13E. The selective emitter layer 314 corresponds to an n + layer doped with phosphorus (P) ions more than the emitter layer 313. At least one of the plurality of set regions in which the selective emitter layer is formed corresponds to a region where the metal electrode 317 (see FIG. 14) is not deposited, and the remaining region corresponds to a region where the metal electrode 317 is deposited. .

Meanwhile, in steps 1304 and 1305, a PSG layer may be further formed on the surface of the silicon substrate 311 on which the emitter layer 313 and the optional emitter layer 314 are formed. Thus, after step 1305, the PSG layer 315 formed on the surface of the silicon substrate 311 including the emitter layer 313 and the optional emitter layer 314 is removed (step 1306). The processing of the silicon substrate 311 in step 1306 is the same as that of step 1005 described above. As a result, as shown in FIG. 13F, a silicon substrate 311 is obtained that includes an emitter layer 313 and an optional emitter layer 314.

As described above, in steps 1302 and 1303, the impurity solution 312 is coated twice in the region where the selective emitter layer 314 is to be formed, so that when the second thermal energy E2 is injected into the silicon substrate 311. A high quality selective emitter layer 314 may be formed.

The above embodiments are for explaining the present invention, and the present invention is not limited to these embodiments, and various embodiments are possible within the scope of the present invention. In addition, although not described, equivalent means will also be referred to as being incorporated in the present invention. Therefore, the true scope of the present invention will be defined by the claims below.

1 is a flowchart illustrating a process of forming a selective emitter of a solar cell according to a first embodiment of the present invention.

2A through 2E are cross-sectional views of a substrate for describing a process of forming a selective emitter of the solar cell illustrated in FIG. 1.

3 is a cross-sectional view illustrating an example of a solar cell including a selective emitter layer formed according to a selective emitter forming process of the solar cell according to the first embodiment of the present invention.

4 is a plan view illustrating an example of a solar cell including a selective emitter layer formed according to a selective emitter forming process of the solar cell according to the first embodiment of the present invention.

5 is a longitudinal cross-sectional view of a diffusion device for forming a selective emitter of a solar cell according to an embodiment of the present invention.

6 is a cross-sectional view taken along the dashed line "A" of the diffusion device shown in FIG.

FIG. 7 is a plan view showing an example of the diffusion device as seen from above the transfer belt after cutting the diffusion device shown in FIG. 6 along the dotted line “B”. FIG.

FIG. 8 is a plan view showing another example of the diffusion device as seen from above the transfer belt after cutting the diffusion device shown in FIG. 6 along the dotted line "B".

9A and 9B are graphs illustrating a change in diffusion coefficient with temperature associated with a selective emitter forming process of a solar cell according to an embodiment of the present invention.

10 is a flowchart illustrating a process of forming a selective emitter of a solar cell according to a second embodiment of the present invention.

11A through 11D are cross-sectional views of a substrate for describing a process of forming a selective emitter of the solar cell illustrated in FIG. 10.

12 is a flowchart illustrating a process of forming a selective emitter of a solar cell according to a third embodiment of the present invention.

13A to 13F are cross-sectional views of a substrate for describing a process of forming a selective emitter of the solar cell illustrated in FIG. 12.

14 is a cross-sectional view illustrating an example of a solar cell including a selective emitter layer formed according to a selective emitter forming process of a solar cell according to a third embodiment of the present invention.

15 is a plan view illustrating an example of a solar cell including a selective emitter layer formed according to a selective emitter forming process of a solar cell according to a third embodiment of the present invention.

FIG. 16 is a plan view showing another example of the diffusion device as seen from above the transfer belt after cutting the diffusion device shown in FIG. 6 along the dotted line "B".

17 is a perspective view illustrating another example of the laser generator illustrated in FIG. 5.

FIG. 18 is a plan view showing still another example of the diffusing device viewed from above the conveying belt after cutting the diffusing device shown in FIG. 6 along the dotted line “B”.

19 is a flowchart illustrating a process of forming a selective emitter of a solar cell according to a fourth embodiment of the present invention.

20A through 20D are cross-sectional views of a substrate for describing a process of forming a selective emitter of the solar cell illustrated in FIG. 19.

Description of the Related Art

111, 311: silicon substrate 112, 312: impurity solution

113, 314: emitter layer 114, 314: optional emitter layer

115, 315: PSG layer 116, 316: antireflection film

117 to 119 and 317 to 319: metal electrodes 121 and 321: finger electrodes

200: diffusion device 210: diffusion chamber

220: conveying belt 230: rotary roller

240: heater 250: laser generator

251: tube 260: exhaust pump

280: coating device

Claims (25)

Etching the silicon substrate to organize the surface of the silicon substrate; Coating an impurity solution on a surface of the silicon substrate; Injecting first thermal energy into the entire surface of the silicon substrate coated with the impurity solution; And Injecting the second thermal energy by irradiating a laser light to a portion of the surface of the silicon substrate coated with the impurity solution while the first thermal energy is injected into the entire surface of the silicon substrate, The temperature by the second thermal energy is the temperature by the first thermal energy and the laser light, and by the first thermal energy, impurity ions diffuse into the silicon substrate to form an emitter layer, and the second thermal energy is applied to the second thermal energy. Wherein the impurity ions are further diffused within a portion of the emitter layer to form a selective emitter layer. Etching the silicon substrate to organize the surface of the silicon substrate; First coating an impurity solution on a surface of the silicon substrate; Second coating the impurity solution on a portion of the surface of the silicon substrate on which the impurity solution is first coated; Injecting first thermal energy over the entire surface of the silicon substrate; And Injecting second thermal energy by irradiating a laser light onto a surface of the silicon substrate coated with the impurity solution while the first thermal energy is injected into the entire surface of the silicon substrate, The temperature by the second thermal energy is the temperature by the first thermal energy and the laser light, and by the first thermal energy, impurity ions diffuse into the silicon substrate to form an emitter layer, and the second thermal energy is applied to the second thermal energy. Wherein the impurity ions are further diffused within a portion of the emitter layer to form a selective emitter layer. The method according to claim 1 or 2, The impurity solution is a selective emitter forming method of a solar cell containing a phosphorus (P) component. The method according to claim 1 or 2, The impurity solution is a method of forming a selective emitter of a solar cell containing POCl ₃ . The method according to claim 1 or 2, The silicon substrate is a p-type substrate doped with boron (B) ions, The emitter layer corresponds to an n layer doped with phosphorus (P) ions, And the selective emitter layer corresponds to an n + layer doped with phosphorus (P) ions more than the emitter layer. The method according to claim 1 or 2, The first step of injecting thermal energy, the method of forming a selective emitter of a solar cell is performed by a radiating non-contact heater. The method according to claim 1 or 2, The second step of injecting thermal energy, a method of forming a selective emitter of a solar cell is carried out by a radiating non-contact heater and a laser generator. The method according to claim 1 or 2, In the step of organizing the surface of the silicon substrate, the method of forming a selective emitter of a solar cell is formed by irregularities on the surface of the silicon substrate by dry or wet etching. The method according to claim 1 or 2, And a portion of the region in which the selective emitter layer is formed corresponds to a region in which a metal electrode is deposited. The method according to claim 1 or 2, The range of temperature by the said 1st thermal energy is 830-900 degreeC, The method of forming a selective emitter of a solar cell is a temperature range of the second thermal energy is 830 ~ 1,070 ℃. The method according to claim 1 or 2, And removing the phosphorus silicate glass (PSG) layer formed on the surface of the silicon substrate after the injection of the second thermal energy. A diffusion chamber in which an inlet is formed at one side and an outlet is formed at the other side; A transfer belt on which a silicon substrate coated with an impurity solution is mounted on a surface organized by an etching process; A plurality of rotating rollers for moving the conveying belt such that the silicon substrate mounted on the conveying belt is conveyed at a set speed from the inlet to the outlet of the diffusion chamber; A heater installed to surround the transfer belt at a predetermined interval from the transfer belt in the diffusion chamber, and injecting first thermal energy to the entire surface of the silicon substrate transferred into the diffusion chamber; And A laser generator penetrating one side of the heater in the diffusion chamber and irradiating laser light to a portion of the surface of the silicon substrate through a plurality of tubes provided to face the transfer belt, By the first thermal energy, impurity ions diffuse into the silicon substrate to form an emitter layer, and by the second thermal energy, the impurity ions are further diffused in a portion of the emitter layer to selectively emit an emitter layer. Form the The temperature of the second thermal energy is a temperature by the first thermal energy and the laser light diffusion device for the selective emitter formation of the solar cell. The method of claim 12, The transfer belt is a diffusion device for forming a selective emitter of a solar cell comprising a metal mesh. The method of claim 12, Diffusion for the selective emitter formation of the solar cell further comprises an exhaust pump penetrates the other side of the heater and extends to the outside of the diffusion chamber to discharge the superheated air inside the diffusion chamber to the outside. Device. The method of claim 12, The heater is a diffusion device for forming a selective emitter of the solar cell including a radiating non-contact heater. Etching the silicon substrate to organize the surface of the silicon substrate; Coating an impurity solution on a surface of the silicon substrate; Injecting first thermal energy into the entire surface of the silicon substrate coated with the impurity solution; And Injecting second thermal energy by irradiating a laser light to a plurality of predetermined regions of the surface of the silicon substrate coated with the impurity solution while the first thermal energy is injected into the entire surface of the silicon substrate. and, The temperature by the second thermal energy is the temperature by the first thermal energy and the laser light, and by the first thermal energy, impurity ions diffuse into the silicon substrate to form an emitter layer, and the second thermal energy is applied to the second thermal energy. Wherein the impurity ions are further diffused within a portion of the emitter layer to form a selective emitter layer. Etching the silicon substrate to organize the surface of the silicon substrate; First coating an impurity solution on a surface of the silicon substrate; Second coating the impurity solution on a plurality of predetermined regions of the surface of the silicon substrate on which the impurity solution is first coated; Injecting first thermal energy over the entire surface of the silicon substrate; And Injecting second thermal energy by irradiating a laser light onto a surface of the silicon substrate coated with the impurity solution while the first thermal energy is injected into the entire surface of the silicon substrate, The temperature by the second thermal energy is the temperature by the first thermal energy and the laser light, and by the first thermal energy, impurity ions diffuse into the silicon substrate to form an emitter layer, and the second thermal energy is applied to the second thermal energy. Wherein the impurity ions are further diffused within a portion of the emitter layer to form a selective emitter layer. The method according to claim 16 or 17, The impurity solution is a selective emitter forming method of a solar cell containing a phosphorus (P) component. The method according to claim 16 or 17, The impurity solution is a method of forming a selective emitter of a solar cell containing POCl ₃ . The method according to claim 16 or 17, The silicon substrate is a p-type substrate doped with boron (B) ions, The emitter layer corresponds to an n layer doped with phosphorus (P) ions, And the selective emitter layer corresponds to an n + layer doped with phosphorus (P) ions more than the emitter layer. The method according to claim 16 or 17, The first step of injecting thermal energy, the method of forming a selective emitter of a solar cell is performed by a radiating non-contact heater. The method according to claim 16 or 17, The second step of injecting thermal energy, a method of forming a selective emitter of a solar cell is carried out by a radiating non-contact heater and a laser generator. The method according to claim 16 or 17, At least one region of the plurality of set regions, wherein the selective emitter layer is formed, corresponds to a region where no metal electrode is deposited, and the remaining region corresponds to a region where the metal electrode is deposited. . The method according to claim 16 or 17, The range of temperature by the said 1st thermal energy is 830-900 degreeC, The method of forming a selective emitter of a solar cell is a temperature range of the second thermal energy is 830 ~ 1,070 ℃. The method according to claim 16 or 17, And removing the phosphorus silicate glass (PSG) layer formed on the surface of the silicon substrate after the injection of the second thermal energy.

Images