JP2005327871A - Solar battery and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly strong solar battery capable of increasing photoelectric conversion efficiency, that is power generation, and to provide its manufacturing method. <P>SOLUTION: The solar battery comprises a first conductivity-type (110) substrate with a dent groove, constituted of ä111} surface on a substrate upper surface, for which the substrate thickness direction is [110] direction, a second conductivity-type emitter layer provided on the upper surface of the substrate, and a finger electrode formed on the upper surface of the emitter layer. The longitudinal direction of the finger electrode and the groove line direction of the dent groove are crossed at an angle such that it is ≥45° and ≤90°. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a solar cell using a (110) substrate, and more particularly to a solar cell that can increase the photoelectric conversion efficiency, that is, the amount of power generation and has high strength, and a method for manufacturing the solar cell.

  A typical single crystal solar cell is formed using a (100) substrate. The largest reason why the (100) substrate is used is that a texture structure as an antireflection structure can be formed relatively easily and at low cost. As shown in FIG. 6, in this conventional solar cell, the single crystal substrate 40 from which damage has been removed is usually immersed in an aqueous solution obtained by adding isopropyl alcohol to 3 weight percent sodium hydroxide or potassium hydroxide at 70 to 90 ° C. To form a pyramid structure 42 randomly arranged on the upper surface of the substrate 40.

On the other hand, apart from this general method, a solar cell using a (110) substrate has been proposed (Patent Document 1). The structure of the solar cell using the proposed (110) substrate will be briefly described with reference to FIG. 10B is a conventional solar cell, which has a (110) substrate 11 of a first conductivity type, for example, an n-type. The substrate thickness direction Z of the substrate 11 is the [110] direction, and a trough groove 12 constituted by a {111} V-groove surface 12a is provided on the upper surface of the substrate. Reference numeral 14 denotes a second conductivity type, for example, p-type emitter layer, for example, a high-concentration p-type diffusion layer formed on the upper surface portion of the substrate 11. A surface protective film, for example, a nitride film 16 is formed on the upper surface of the emitter layer 14. Is provided. Finger electrodes 18 are formed on the upper surface of the emitter layer 14 via a nitride film 16. Reference numeral 20 denotes a BSF (Base Surface Field) layer provided on the lower surface portion of the substrate 10, for example, a high-concentration n-type diffusion layer, and a back electrode 22 is provided on the lower surface of the BSF layer 20.
Japanese Patent Publication No. 2001-504996

  However, in the structure of the proposed solar cell, as shown in FIG. 3, the finger electrode 18 is in a state in which the longitudinal direction Y and the groove line direction X of the valley groove 12 are parallel or nearly parallel. In such a case, the yield is greatly reduced. The cause of the decrease in yield is that the crystal is easily broken along the crystal barrier line, and in particular, it is often caused by a load when the finger electrode 18 is formed.

  Furthermore, in this conventional structure, when the longitudinal direction of the finger electrode 18 is close to parallel to the groove line direction X of the valley groove 12 constituted by the {111} plane V-groove surface 12a, there is a problem of resistance loss. Occur. Usually, in order to form an antireflection structure at low cost, an alkaline aqueous solution is used as described above. In this case, the {111} plane with the slowest etching rate is exposed. When a (110) substrate is used, it is very difficult to form a random texture as shown in FIG. 6, but by using an etching mask, a {111} plane as shown in FIG. It is possible to form the valley groove 12 by exposing it as the surface 12a.

  In FIG. 3, if the groove line direction X of the trough groove 12 and the longitudinal direction Y of the finger electrode 18 are parallel, the current path 14b of the electric wire flowing in the emitter layer 14 has a sawtooth shape, so that it is compared with a linear current path. And get longer. This is obvious when comparing FIG. 1 showing one embodiment of a solar cell 10A according to the present invention to be described later and FIG. 3 showing a structural example of a solar cell 10B using the above-described conventional (110) substrate. Assuming that the pitches of the finger electrodes 18 and 19 in FIGS. 3 and 1 are equal and that the current path 14a of the emitter layer 14 in FIG. 1 is linear and the current apparently moves a distance L, as shown in FIG. This is because the current path 14b of the third emitter layer 14 is serrated and the current moves a distance of 1.225L. As a result, in the conventional solar cell 10B, the internal series resistance increases, and the photoelectric conversion efficiency decreases due to resistance loss during power generation.

  Further, in the solar cell using the conventional (110) substrate 11 described above, when the substrate thickness direction Z coincides with the [110] direction, even if the above V-groove surface antireflection structure is formed, The antireflection film having a low reflectance (that is, a high transmittance) has a high transmittance even with respect to light returning from the inside at the same angle. Therefore, as shown in FIG. The incident light 24 of the long wavelength light incident on the substrate 11 easily escapes from the substrate 11 as the outgoing light 26.

  The present invention has been made in order to overcome the above-described problems of the prior art, and provides a high-strength solar cell that can increase photoelectric conversion efficiency, that is, power generation, and a method for manufacturing the same. With the goal.

  In order to solve the above-described problem, a first aspect of the solar cell of the present invention is a first conductivity type having a valley groove in which the substrate thickness direction is the [110] direction and the substrate upper surface is configured by the [111] plane. (110) A substrate, a second conductivity type emitter layer provided on the upper surface of the substrate, and a finger electrode formed on the upper surface of the emitter layer, the longitudinal direction of the finger electrode and the groove of the trough The linear direction intersects at an angle of 45 degrees or more and 90 degrees or less.

  In the second aspect of the solar cell of the present invention, the substrate thickness direction is set at an angle of more than 0 degree and not more than 10 degrees with respect to the [110] direction, and is configured by the [111] plane on the upper surface of the substrate. A first conductivity type (110) substrate having a trough, a second conductivity type emitter layer provided on the upper surface of the substrate, and a finger electrode formed on the upper surface of the emitter layer, The longitudinal direction and the groove line direction of the valley groove intersect with each other at an angle of 45 degrees or more and 90 degrees or less. As the first conductivity type substrate, an n-type substrate is preferably used.

  The method for manufacturing a solar cell according to the present invention includes a step of preparing a first conductivity type substrate in which the substrate thickness direction is set at an angle of 0 degrees to 10 degrees with respect to the [110] direction, and at least one of the substrates Forming an etching mask on the surface, and the etching mask.

Forming a valley groove by cutting in a direction or [001] direction, forming a second conductivity type emitter layer on the upper surface of the substrate, and 45 degree to the groove line direction of the valley groove on the upper surface of the emitter layer. And a step of forming finger electrodes that intersect at an angle of 90 degrees or less.

  According to the solar cell of the first aspect of the present invention, by using the (110) substrate, it is possible to increase the diffusion length of the fractional carriers, and thus it is possible to increase the photoelectric conversion efficiency, that is, the power generation amount. Furthermore, the strength of the solar cell can be increased by crossing the longitudinal direction of the finger electrodes at an angle of 45 degrees or more and 90 degrees or less with respect to the groove line direction of the troughs constituted by {111} planes, It is possible to prevent the yield from being lowered when electrodes are formed by screen printing. Further, according to the solar cell of the second aspect of the present invention, by adopting a configuration in which the substrate thickness direction is slightly tilted (tilted) with respect to the [110] direction, the light confinement effect can be enhanced, Therefore, the effect that the photoelectric conversion efficiency, that is, the power generation amount can be further increased is achieved. According to the method of the present invention, the solar cell of the present invention can be efficiently produced.

  Hereinafter, the embodiment of the present invention will be described in detail with reference to FIG. 1 in the accompanying drawings, but it goes without saying that various modifications other than the illustrated examples are possible without departing from the technical idea of the present invention. Absent. FIG. 1 is a perspective explanatory view schematically showing one embodiment of a solar cell according to the present invention. 1, the same or similar members as those shown in FIG. 3 will be described using the same reference numerals.

  In FIG. 1, 10A is a solar cell according to the present invention, and the same configuration as the conventional solar cell 10B shown in FIG. The solar cell 10A of the present invention has a (110) substrate 11 of a first conductivity type, for example, an n-type. The substrate thickness direction Z of the substrate 11 is the [110] direction, and a trough groove 12 constituted by a {111} -plane V-groove surface 12a is provided on the upper surface of the substrate. Reference numeral 14 denotes a second conductivity type, for example, p-type emitter layer, for example, a high-purity p-type diffusion layer formed on the upper surface portion of the substrate 11. A surface protective film, for example, a nitride film 16 is formed on the upper surface of the emitter layer 14. Is provided. A finger electrode 19 is formed on the upper surface of the emitter layer 14 via a nitride film 16.

  The feature of the solar cell 10A of the present invention is that the finger electrode 19 is formed in a mode different from the finger electrode 18 of the conventional solar cell 10A. That is, while the finger electrode 18 of the conventional solar cell 10B is provided at an angle in which the longitudinal direction Y and the groove line direction X of the valley groove 12 are parallel or nearly parallel, the solar cell of the present invention. The finger electrode 19 of 10B is provided so that the longitudinal direction Y and the groove line direction X of the valley groove 12 intersect at an angle of 45 degrees or more and 90 degrees or less. In the example of FIG. 1, the groove line direction X of the valley groove 12 and the longitudinal direction Y of the finger electrode 19 are orthogonal to each other, that is, intersects at an angle of 90 degrees.

  By adopting such a configuration, as described above, when the solar cell 10A of the present invention shown in FIG. 1 is compared with the solar cell 10B having the conventional structure shown in FIG. 3, the finger electrodes in FIG. 3 and FIG. Assuming that the pitches 18 and 19 are equal and the current path 14a of the emitter layer 14 in FIG. 1 is linear and the current apparently moves a distance L, the current path 14b of the emitter layer 14 in FIG. The current travels a distance of 1.225L. In other words, the current path 14a of the current flowing in the emitter layer 14 of the solar cell 10A of the present invention is shorter than the current path 14b of the current flowing in the emitter layer 14 of the conventional solar cell 10B. As a result, the series resistance in the solar cell 10A is reduced, the decrease in photoelectric conversion efficiency due to resistance loss during power generation is reduced, and the photoelectric conversion efficiency is improved as compared with the conventional case.

  In the above-described embodiment, the case where the (110) substrate in which the substrate thickness direction Z is the [110] direction has been described. However, the substrate thickness direction exceeds 10 degrees with respect to the [110] direction. Even if a (110) substrate tilted at an angle of less than or equal to a degree is used, the same effect can be achieved. In this case, there is an advantage that the light confinement action can be further enhanced.

  That is, most of the light incident perpendicularly to the bottom surface travels inside the silicon at an angle A with respect to the V-groove surface, reflects off the bottom surface, and then collides with another V-groove surface at an angle B. Usually, a solar cell has a reflectance as small as possible, and an antireflection film is formed so that light can be maximally introduced into the device. However, since such a film having a low reflectance is also a film having a high transmittance, when light is emitted from the inside of the device to the outside as shown in FIGS. It has become. In particular, as shown in FIG. 5A, when the substrate thickness direction is not tilted with respect to the [110] direction, the angle A and the angle B are equal to each other, so that the transmission conditions are most easily transmitted.

  On the other hand, when the substrate thickness direction is tilted with respect to the [110] direction as shown in FIG. 5B, if the angle B is different from the angle A, and the angle B> the angle A, the V groove surface 12a Since the transmittance from the silicon to the outside is always lower than when the angle A and the angle B are equal, the light taken into the solar cell is less likely to leak to the outside, and the light generation current increases.

  Note that a solar cell in which the substrate thickness direction is tilted with respect to the [110] direction can be easily obtained by slicing the [110] crystal at an angle to tilt.

  Then, the manufacturing method of the solar cell of this invention is demonstrated with reference to FIG. FIG. 2 is a flowchart showing an example of the process sequence of the method of the present invention. In FIG. 2, the case where the first conductivity type is n-type and the second conductivity type is p-type will be described. In addition, the code | symbol in FIG. 1 was used for the code | symbol of each member in the following explanatory note.

  As shown in FIG. 2, first, an n-type (110) substrate 11 is prepared (step 100). The thickness direction of this substrate is set at an angle of 0 ° to 10 ° with respect to the [100] direction. As this substrate, a silicon single crystal substrate can be used, and it may be produced by any method of the chocolate ski (CZ) method and the float zone (FZ) method. The substrate specific resistance is preferably, for example, 0.1 to 20 Ω · cm, and in particular, 0.5 to 2.0 Ω · cm is suitable for producing a high-performance solar cell.

  Next, the damaged layer of the substrate 11 is removed by etching (step 102). As an etching solution for removing the damage, a strong alkaline aqueous solution such as potassium hydroxide can be used in addition to the aqueous sodium hydroxide solution, and the same purpose can be achieved with an aqueous acid solution such as hydrofluoric acid. is there.

  An oxide film or a nitride film is deposited on the surface of the substrate 11 subjected to the damage etching by a predetermined method, and a multi-blade dicing saw is used.

The oxide film or nitride film including the substrate 11 is cut into a strip shape in the direction (or [001] direction) to form an etching mask (step 104). The later the etching becomes easier as the portion left to be cut becomes thinner.

  V-groove etching is performed by immersing the substrate provided with this etching mask in an etching solution, thereby forming a V-groove structure or a valley-groove structure as shown in FIG. 4 (step 106). In general, it is preferable that the solar cell has an uneven shape on the surface. The reason is that in order to reduce the reflectance in the visible light region, it is necessary to cause the light receiving surface to perform reflection at least twice as much as possible. In the present invention, a V-groove structure or a trough structure is formed. In the example of FIG. 2, the antireflection structure forming method by wet etching is described. However, it is also possible to directly form the V-groove and U-groove using a grinding machine or a laser processing machine. Also, acid etching, reactive ion etching, or the like can be used to create a micro random uneven structure in the trough.

  An emitter layer (p-type diffusion layer) 14 is formed by performing boron diffusion on the substrate having the V-groove structure or the valley-groove structure (step 108). As a boron diffusion method, it is possible to perform thermal diffusion using a solid source in addition to thermal diffusion using a liquid source such as boron bromide. Since it is difficult to increase the surface concentration in the ion implantation method, it has not been actively used in the production of solar cells. However, in the present invention, since the (110) substrate 11 is used, this ion implantation method is also a diffusion layer. It is easy to control the formation and is effective.

  Phosphorus diffusion is performed on the substrate 11 on which the emitter layer 14 is formed, thereby forming a high concentration n-type diffusion layer (BSF layer) 20 on the surface opposite to the emitter layer 14 (step 110). Again, the BSF layer 20 can be formed by a thermal diffusion method using a solid diffusion source or an ion implantation method, but phosphorus and boron dopants are spin-coated on a wafer in advance on each side, and a large number of layers are stacked at a time. Co-diffusion is one of the most effective and convenient methods.

  Further, a surface protective film 16 is formed on the emitter layer 14 (step 112). Specifically, after boron or phosphorous glass formed on the substrate surface is etched with hydrofluoric acid, a nitride film or the like is deposited as a surface protective film 16 on the emitter layer 14 using, for example, a direct plasma CVD apparatus. The film thickness is preferably 70 nm to 100 nm because it also serves as an antireflection film. Other antireflection films include oxide films, titanium dioxide films, zinc oxide films, tin oxide films, and the like, which can be substituted. In addition to the above, the formation method includes a remote plasma CVD method, a coating method, a vacuum deposition method, and the like. From the economical viewpoint, it is preferable to form the nitride film by the plasma CVD method. Furthermore, if a film having a refractive index between 1 and 2, such as a magnesium difluoride film, is formed on the antireflection film so that the total reflectance is minimized, the reflectance is further reduced. The current density is increased.

  Subsequently, an electrode 22 is formed on the back surface of the substrate (step 114). Specifically, using a screen printing apparatus, a paste made of silver is applied to the back surface of the substrate and dried.

  Next, the finger electrode 19 is formed on the substrate surface (step 116). Specifically, a silver electrode containing aluminum is printed and dried with a finger electrode pattern printing plate using a screen printing apparatus. At this time, printing is performed so that the longitudinal direction Y of the finger electrode intersects the ridge line direction (groove line direction) X of the V-groove or valley groove at an angle of 45 degrees to 90 degrees (90 degrees in the example of FIG. 1). Do. Thereafter, firing is performed with a predetermined thermal profile to obtain a final electrode. These electrodes can be formed by a vacuum deposition method, a sputtering method, or the like other than the printing method described above. By forming the electrodes 22 and 19 described above, the solar cell 10A of the present invention is completed (step 118).

  The present invention will be described more specifically with reference to the following examples. However, it is needless to say that these examples are shown by way of illustration and should not be construed in a limited manner. The reference numerals in FIG. 1 are used as the reference numerals of the members in the following description.

(Example 1)
The method for manufacturing the solar cell in this example is as follows. First, a crystal plane orientation (110), a thickness of 250 μm, an as-slice specific resistance of 2 Ω · cm (a dopant concentration of 2.4 × 10 ¹⁵ cm ⁻³ ), a phosphorus-doped n-type single crystal silicon substrate was prepared, and a 40 weight percent aqueous sodium hydroxide solution was prepared. And the damaged layer was removed by etching. Next, an oxide film or a nitride film is deposited by a predetermined method, and using a multi-blade dicing saw, the W direction shown in FIG.

The oxide film or nitride film including the Si substrate 11 in the direction was cut into a strip shape. The thinner the portion to be shaved, the easier it is to etch later. If this sample is immersed again in 40 weight percent sodium hydroxide for several minutes, a V-groove structure or a trough structure as shown in FIG. 4 is formed.

  Subsequently, a p-type diffusion layer (emitter layer) 14 having a sheet resistance of 40Ω / □ was formed by performing boron thermal diffusion using a boron bromide liquid source. Further, a high concentration n-type diffusion layer (BSF layer) 20 having a sheet resistance of 20Ω / □ was formed on the surface opposite to the emitter layer 14 by performing phosphorous thermal diffusion using a phosphorous oxychloride liquid source. At this time, in order to prevent phosphorus from diffusing into the p-type emitter layer 14, the surfaces on which the emitter layer 14 was formed were overlapped and then introduced into the furnace. Next, after boron or phosphorous glass formed on the surface was etched with hydrofluoric acid, a nitride film 16 as a surface protective film was deposited on the emitter layer using a direct plasma CVD apparatus.

  Next, using a screen printing apparatus, a silver paste was applied to the back surface and dried. Further, on the surface side, a silver electrode containing aluminum was printed by a finger electrode pattern printing plate using a screen printing apparatus and dried. At this time, printing was performed so that the longitudinal direction Y of the finger electrode 19 was orthogonal to the ridge line direction (groove line direction) X of the V groove or the valley groove 12, that is, intersected at 90 degrees. Thereafter, firing was performed with a predetermined thermal profile, and final electrodes 19 and 22 were obtained.

The current-voltage characteristics of 100 manufactured 10 cm square solar cells were measured in a 25 ° C. atmosphere under a solar simulator (light intensity: 1 kW / m ² , spectrum: AM1.5 global). Table 1 shows the characteristics of the solar cell manufactured in Example 1.

(Example 2)
A solar cell was produced in the same manner as in Example 1 except that an n-type (110) substrate having the same grade as Example 1 and having the substrate thickness direction tilted by 10 degrees with respect to the [110] direction was used. The characteristics are shown in Table 1.

(Comparative Example 1)
A solar cell was produced in the same manner as in Example 1 except that an n-type (100) substrate of the same grade as that in Example 1 was used.

  In Example 1, as shown in Table 1, by using an n-type (110) substrate, higher conversion efficiency can be obtained than a solar cell using the same grade n-type (100) substrate (Comparative Example 1). It was.

  This is because the mobility in the [110] direction is high and the diffusion length is longer than that in the [111] direction. FIG. 7 shows the results obtained by measuring the mobility of the n-type single crystal silicon substrate by changing the electric field. The decimal carrier lifetime is not significantly different whether in the [110] direction or the [111] direction. That is, the direction dependence of the capture cross section is small in crystalline silicon. However, whether or not the excited minority carriers can reach the pn junction depends on the diffusion length. If the mobility is large as in the present invention, the minority carriers generated near the back surface of the solar cell are more Since the pn junction formed near the light receiving surface can be reached, the amount of power generation is increased.

  In general, the relationship of the following equation (1) is established among the carrier diffusion length L, the diffusion coefficient D, and the lifetime t.

  On the other hand, if the carrier mobility is μ, Einstein's relational expression is established between D and μ,

Can be expressed as In Equation (2), k is Boltzmann's constant, T is absolute temperature, and q is electric charge. From the above formulas (1) and (2),

Thus, the higher the mobility μ, the longer the diffusion length L, satisfying the above theory.

  Furthermore, in Example 2, the substrate thickness direction is tilted by 10 degrees in the [110] direction, so that the transmittance from the silicon to the outside on the V groove surface is lower than in Example 1 in which the substrate thickness direction is not tilted in the [110] direction. Therefore, the light taken into the solar cell is less likely to leak to the outside, and the power generation amount can be further increased.

(Examples 3-7 and Comparative Examples 2-5)
The crossing angle between the groove line direction X of the troughs 12 constituted by {111} planes and the longitudinal direction Y of the finger electrodes 19 is 0 degree (comparative example) on the substrate whose substrate thickness direction is not tilted with respect to the [110] direction. A solar cell was produced in the same manner as in Example 1 except that 2), 30 degrees (Comparative Example 3), 45 degrees (Example 3), and 60 degrees (Example 4). Furthermore, the crossing angle between the groove line direction X of the trough groove 12 constituted by the {111} plane and the longitudinal direction Y of the finger electrode 19 is set on the substrate whose substrate thickness direction is tilted by 10 degrees with respect to the [110] direction. A solar cell was produced in the same manner as in Example 1 except that the angle was 0 degrees (Comparative Example 4), 30 degrees (Comparative Example 5), 45 degrees (Example 5), and 60 degrees (Example 6). The characteristic average values and yields of the respective solar cells are shown in Table 2 together with the numerical values of the solar cells of Example 1 and Example 2 having an intersection angle of 90 degrees.

  As shown in Table 2, the yield could be improved by bringing the intersection angle between the longitudinal direction Y of the finger electrode and the groove line direction X of the trough constituted by the {111} planes to 90 degrees. At the same time, resistance loss can be reduced by shortening the effective current path in the emitter layer, and as a result, a solar cell with higher conversion efficiency can be obtained. Furthermore, by using a substrate whose substrate thickness direction is tilted by 10 degrees in the [110] direction, a solar cell with even higher conversion efficiency can be obtained. The same experiment was performed on the substrate whose substrate thickness direction was tilted at an angle of more than 0 degrees and less than 10 degrees in the [110] direction, and a solar cell with improved conversion efficiency was obtained as in the case of tilting by 10 degrees. Confirmed that it can be obtained.

1 is a perspective explanatory view schematically showing one embodiment of a solar cell according to the present invention. It is a flowchart which shows an example of the process order of this invention method. It is a figure which shows one structural example of the conventional solar cell. It is explanatory drawing which shows an example of the trough structure in a crystalline solar cell. It is explanatory drawing which shows one path | route of the light in the solar cell which has a trough structure on the surface and a structure where the back surface is flat, (a) is a board | substrate whose substrate thickness direction is 0 degree | times with respect to a [110] direction, b) shows the case of the substrate in which the substrate thickness direction is tilted with respect to the [110] direction. It is explanatory drawing which shows an example of the antireflection structure (random texture) in a crystalline solar cell. It is a graph which shows the magnitude | size of the mobility with respect to the crystal-axis direction in the (110) board | substrate of a n-type single crystal silicon, and a (100) board | substrate.

Explanation of symbols

  10A: Solar cell of the present invention, 10B: Solar cell of conventional structure, 11: Substrate (n-type silicon), 12: Valley groove, 12a: V-groove surface, 14: Emitter layer (high concentration p-type diffusion layer), 14a , 14b: current path in the emitter layer, 16: insulating film (nitride film), 18: finger electrode, 20: BSF layer (high concentration n-type diffusion layer), 22: back electrode, 24: incident light, 26: outgoing light .

Claims (4)

  A first conductivity type (110) substrate having a [110] direction in the substrate thickness direction and having a trough formed by {111} planes on the upper surface of the substrate, and a second conductivity type emitter layer provided on the upper surface of the substrate And a finger electrode formed on the upper surface of the emitter layer, and the longitudinal direction of the finger electrode and the groove line direction of the valley groove intersect at an angle of 45 degrees or more and 90 degrees or less. Solar cell featuring.   1st conductivity type (110) board | substrate which has the trough groove | channel comprised by the angle of more than 0 degree | times and below 10 degree | times with respect to the [110] direction, and the board | substrate thickness direction comprised by the {111} surface on the board | substrate upper surface And a second conductivity type emitter layer provided on the upper surface of the substrate, and a finger electrode formed on the upper surface of the emitter layer, wherein the longitudinal direction of the finger electrode and the groove line direction of the valley groove are A solar cell characterized by intersecting at an angle of 45 degrees or more and 90 degrees or less.   The solar cell according to claim 1 or 2, wherein the first conductivity type substrate is an n-type substrate. Providing a first conductivity type substrate in which the substrate thickness direction is set at an angle of 0 degrees to 10 degrees with respect to the [110] direction; and forming an etching mask on at least one surface of the substrate; The etching mask

Forming a valley groove by cutting in the direction or [001] direction, forming a second conductivity type emitter layer on the upper surface of the substrate, and 45 degree to the groove line direction of the valley groove on the upper surface of the emitter layer. And a step of forming finger electrodes intersecting at an angle of 90 degrees or less.

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