JP2009076840A - Method of manufacturing photoelectric conversion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a photoelectric conversion device with an excellent conversion efficiency by reducing the occurrence of grinding of a semiconductor portion of a second conductivity type during the manufacturing process. <P>SOLUTION: A concavo-convex structure with the top of convex portions being formed into a curved surface is formed on the surface of crystal semiconductor particles of a first conductivity type. Next, the crystal semiconductor particles are pressed against and joined to one principal plane of a conductive substrate. Thereafter, an insulation layer is formed between the crystal semiconductor particles on one principal plane of the conductive substrate in such a manner that upper parts of the crystal semiconductor particles may be exposed. Then, a transparent conductive layer is formed on the upper parts of the crystal semiconductor particles and on the insulation layer to attain completion of manufacturing the photoelectric conversion device. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a photoelectric conversion device used for solar power generation or the like.

  In recent years, since sufficient photoelectric conversion is possible even with a small amount of crystals, photoelectric conversion devices using crystal semiconductor particles as photoelectric conversion elements instead of large crystal ingots have been developed.

  In particular, in recent years, a photoelectric conversion device having high conversion efficiency has been demanded, and improvement of conversion efficiency is also being studied for a photoelectric conversion device using crystalline semiconductor particles as a photoelectric conversion element.

For example, Patent Document 1 describes a method for producing crystalline semiconductor particles in which a concavo-convex structure is formed on a surface layer that performs photoelectric conversion in order to efficiently guide light to a pn junction. In the invention described in this document, when the crystalline semiconductor particles and the conductive substrate are joined to be electrically connected, the crystalline semiconductor particles are pressed against the conductive substrate.
JP 2005-159167 A

  However, in the invention described in Patent Document 1, since the concavo-convex structure is provided on the surface of the crystalline semiconductor particles by the sandblast method, it is difficult to form a uniform concavo-convex structure. Light could not be efficiently guided to the pn junction.

  In addition, when bonding to the conductive substrate by pressing, the tip of the convex portion of the concavo-convex structure on the surface layer of the crystalline semiconductor particles may come into contact with a jig or the like used for pressing, and the semiconductor portion of the second conductivity type may be scraped. In some cases, sufficient conversion efficiency could not be obtained.

  Accordingly, an object of the present invention is to provide a method for manufacturing a photoelectric conversion device that enables formation of a uniform uneven structure on the surface of the semiconductor particles.

  It is another object of the present invention to provide a method for manufacturing a photoelectric conversion device that exhibits excellent conversion efficiency by reducing the occurrence of chipping of the second conductivity type semiconductor portion during fabrication.

  In the method for manufacturing a photoelectric conversion device according to the present invention, the surface of the spherical first conductive type crystalline semiconductor particles having the second conductive type semiconductor portion formed on the surface layer is etched using the etching processing solution. Step 1 of forming the concavo-convex structure in which the tip of the convex portion is formed into a curved surface is formed on the surface of the crystalline semiconductor particle.

  It is preferable that the etching treatment solution used for the etching treatment in the step 1 includes sodium hydroxide and at least one selected from the group consisting of isopropyl alcohol, lauric acid, and n-octanoic acid.

  It is preferable that the concentration of sodium hydroxide in the etching treatment solution is 0.7 to 3%.

  In the etching process in the step 1, it is preferable that the crystalline semiconductor particles are treated with the etching treatment solution and the etching treatment solution is moved relative to the crystalline semiconductor particles.

  The etching process in the step 1 has a gap on the side that can discharge the etching process solution to the outside and does not discharge the crystalline semiconductor particles to the outside, and the etching process solution is continuously supplied. The etching treatment solution, which is performed in the container, is pressed against the side by the centrifugal force generated by rotating the container, and the etching solution supplied into the container is continuously supplied from the gap. The crystalline semiconductor particles are preferably treated while being discharged.

  Preferably, the method further includes a step 2 of pressing and bonding the crystalline semiconductor particles obtained in the step 1 to one main surface of the conductive substrate.

  By performing an etching process on the surface of the spherical first conductive type crystalline semiconductor particles having the second conductive type semiconductor part formed on the surface layer using an etching process solution, the tip of the convex part is formed into a curved surface. The uneven structure thus formed can be uniformly formed on the surface of the crystalline semiconductor particles.

  Further, according to the method for manufacturing a photoelectric conversion device of the present invention, the surface of the spherical first conductive type crystalline semiconductor particles having the second conductive type semiconductor portion formed on the surface layer is etched to thereby form the convex portion. An uneven structure having a curved tip is formed on the surface of the crystalline semiconductor particle.

  As a result, when the obtained crystalline semiconductor particles are bonded to the conductive substrate by being bonded, the occurrence of abrasion of the second conductive type semiconductor portion caused by contacting with the jig used for pressing can be reduced, and excellent A photoelectric conversion device exhibiting conversion efficiency can be obtained.

  An etching process solution used for the etching process includes sodium hydroxide and at least one selected from the group consisting of isopropyl alcohol, lauric acid, and n-octanoic acid, thereby allowing the anisotropic etching of the etching process solution. Therefore, the tip of the obtained convex portion can be controlled to have a gently curved shape.

  According to the method for manufacturing a photoelectric conversion device of the present invention, the crystal semiconductor particles are treated with the etching treatment solution, and the etching treatment solution is moved relative to the crystal semiconductor particles. Thus, bubbles generated on the semiconductor particles can be removed. Thereby, since the uniform etching process to the said semiconductor particle surface is possible, an uneven structure can be uniformly formed in the surface of the said crystalline semiconductor particle.

  The etching process has a gap in the side that can discharge the etching process solution to the outside and does not discharge the crystalline semiconductor particles to the outside, and is in a container to which the etching process solution is continuously supplied. It is done. Then, the semiconductor particles are pressed by the centrifugal force generated by the container rotation, and further, the etching process is performed while discharging the etching process solution from the gap by the centrifugal force, thereby continuously supplying a new etching process solution. It is possible to remove the bubbles smoothly.

  The method for producing a photoelectric conversion device of the present invention includes (1) etching the surface of a spherical first conductive type crystalline semiconductor particle having a second conductive type semiconductor portion formed on the surface layer, so that the tip of the convex portion Forming a concavo-convex structure having a curved surface on the surface of the crystalline semiconductor particles. (Hereinafter referred to as step 1). In addition, it is preferable to include after the process 1 (2) the process (henceforth process 2) which presses and joins the said crystalline semiconductor particle to one main surface of an electroconductive board | substrate.

  Hereinafter, each process will be described with reference to the drawings. FIG. 1 is a cross-sectional view of crystalline silicon particles having an uneven structure on the surface. FIG. 2 is a drawing-substituting photograph in which the surface of the photoelectric conversion device of the present invention is observed obliquely from above with a scanning electron microscope. FIG. 3 is a drawing-substituting photograph in which the surface of the photoelectric conversion device of the present invention is observed from above with a scanning electron microscope. FIG. 4 is a cross-sectional view of the photoelectric conversion device in the process of the method for manufacturing a photoelectric conversion device of the present invention.

  In the method for manufacturing a photoelectric conversion device of the present invention, prior to step 1, a step of forming the second conductive type semiconductor portion 2 on the surface layer of the spherical first conductive type crystalline semiconductor particles 1 is performed. Here, examples of the crystalline semiconductor particles 1 include silicon. Moreover, the particle diameter of the crystalline semiconductor particle 1 is 0.2-0.8 mm. The crystalline semiconductor particles 1 exhibit a first conductivity type (for example, p-type). In the case of p-type, dopants such as B, Al, and Ga are used. It is obtained by making it contain in a raw material when manufacturing by. The crystalline semiconductor particle 1 is formed as a single crystal in a granular form by, for example, a jet method.

  The step of forming the second conductive type semiconductor portion 2 on the surface layer of the spherical first conductive type crystalline semiconductor particles 1 is performed by a thermal diffusion method or a vapor phase growth method.

  In the case of the thermal diffusion method, for example, by inserting the crystalline semiconductor particles 1 into a high-temperature quartz tube for a certain period of time using a phosphorus compound such as phosphorus oxychloride as a diffusing agent, if the semiconductor portion is n-type, the crystalline semiconductor particles An n-type semiconductor portion 2 can be formed on the surface of 1. As an example, by inserting the crystalline semiconductor particles 1 into a quartz tube at 900 ° C. for 30 minutes, an n-type semiconductor portion 2 having a thickness of 1 μm can be formed on the surface thereof.

  In the case of a vapor phase growth method or the like, for example, the n-type semiconductor portion 2 can also be formed by introducing a small amount of a vapor phase of a phosphorus compound serving as an n-type dopant into the vapor phase of a silane compound.

(Process 1)
The crystalline semiconductor particles 1 formed in step 1 are shown in FIG. In step 1, the surface of the spherical first conductive type crystalline semiconductor particle 1 having the second conductive type semiconductor portion 2 formed on the surface layer is etched so that the tip of the convex portion has a curved surface. A structure 3 is formed on the surface of the crystalline semiconductor particle 1. The uneven structure 3 is formed in the second conductivity type semiconductor portion 2 corresponding to the surface of the crystalline semiconductor particle 1. Here, whether or not the tip of the convex portion has a curved surface can be confirmed by observing from a lateral direction or obliquely upward with a magnification of 3000 to 10000 times with an electron microscope or the like.

  FIG. 2 is an SEM photograph (magnification 3000 times) when the surface of the crystalline semiconductor particles obtained in step 1 is measured obliquely from above. From this figure, it can be seen that the tip of the convex portion is curved.

  In order to make the tip of the convex portion have a curved surface shape, it is necessary to etch the semiconductor portion 2 of the second conductivity type on the surface layer of the crystalline semiconductor particles 1.

  As such an etching process, a wet etching process is preferable, and in particular, a wet etching process under alkaline conditions is preferable.

  In particular, when the crystalline semiconductor particles 1 are silicon, the solution used for the wet etching process is sodium hydroxide (NaOH) and at least one selected from the group consisting of isopropyl alcohol, lauric acid, and n-octanoic acid. It is preferable to include. By performing wet etching using such an etching treatment solution, the etching rate in each direction is suitable for curving the tip of the convex portion, so that not only the uneven structure 3 is produced on the surface layer of the crystalline semiconductor particles 1, The convex portion can be a gently curved surface. Note that the NaOH content in the wet etching solution is 0.7 to 3 wt%, preferably 0.5 to 3 wt%. The content of at least one selected from the group consisting of isopropyl alcohol, lauric acid and n-octanoic acid in the wet etching solution is 2 to 8 vol%.

  Examples of the alkali component used for wet etching under alkaline conditions generally include sodium hydroxide (NaOH), potassium hydroxide (KOH), etc., but the etching anisotropy is low and the convex portion is curved. Sodium hydroxide (NaOH) is optimal in the present invention because it is optimal for tip formation.

  The width of the base of the convex portion of the concavo-convex structure 3 is preferably 0.1 to 5 μm. If the width of the base portion is less than 0.1 μm, the width of the base portion of the convex portion becomes small, and the strength of one convex portion is not sufficient, so that it is difficult to reduce the occurrence of abrasion of the second conductive type semiconductor portion. There is. Further, if the width of the base portion exceeds 5 μm, the number of convex portions is reduced, so that it is difficult to reduce the occurrence of abrasion of the second conductivity type semiconductor portion. Here, as shown in FIG. 3, the width of the base portion can be obtained by measuring the length of the bottom surface of the quadrangular pyramidal protrusion when the crystalline semiconductor particles are observed from above at a magnification of 3500 times.

  The ten-point average roughness Rz of the concavo-convex structure 3 produced as described above is preferably 0.1 to 3.5 μm. If the ten-point average roughness Rz is less than 0.1 μm, the ten-point average roughness Rz is almost the same as the state without the concavo-convex structure 3, and therefore there is a tendency that sufficient conversion efficiency cannot be obtained. In addition, when the ten-point average roughness Rz exceeds 3.5 μm, the distance between the top of the convex portion and the bottom point of the concave portion is large, so that it is difficult to reduce the occurrence of abrasion of the second conductivity type semiconductor portion. is there. Here, the ten-point average roughness Rz is the average of the highest elevation of the peak from the highest to the fifth and the lowest elevation of the valley from the deepest to the fifth in the portion where only the reference length is extracted from the cross-sectional curve. It represents the value of the difference from the value.

  It is preferable that 4 to 100 convex portions of the concavo-convex structure 3 exist per 10 μm × 10 μm. If the concavo-convex structure 3 has less than four convex portions, the number of convex portions in a certain range is small, and thus it is difficult to reduce the occurrence of abrasion of the second conductivity type semiconductor portion. In addition, when the number of convex portions of the concavo-convex structure 3 exceeds 100, the strength of one convex portion cannot be obtained sufficiently, and it tends to be difficult to reduce the occurrence of abrasion of the second conductivity type semiconductor portion.

  In the present invention, crystalline semiconductor particles are made of silicon, and by using a wet etching treatment solution containing NaOH and at least one selected from the group consisting of isopropyl alcohol, lauric acid and n-octanoic acid, The tip of the convex portion can be curved, the width of the base of the convex portion of the concavo-convex structure 3 is 0.1 to 5 μm, the ten-point average roughness Rz of the concavo-convex structure 3 is 0.1 to 3.5 μm, The convex portions can be controlled to 4 to 100 per 10 μm × 10 μm.

  Hereinafter, an example of the etching process of step 1 is shown as a specific example, but step 1 is not limited to this method.

  FIG. 7A is a perspective view of the container 11 used in the etching process, and FIG. 7B is a diagram schematically showing a cross section of the container 11.

  In FIG. 7, the container 11 is open at the top, and can supply an etching treatment solution. Further, the container 11 has an inner wall surface and a bottom surface, and the etching treatment solution can be held in the container. Furthermore, the container 11 has a gap 12 connected to the inside of the container on the outer periphery thereof, and the etching treatment solution inside the container is released from the gap 12 to the outside by rotating around the central axis of the container 11. Can do.

  Crystal semiconductor particles 1 are placed in the container 11. The gap 12 in the container 11 has such a size that the etching solution can be discharged to the outside, but the crystal semiconductor particles 1 are not discharged to the outside, and the width of the gap 12 is smaller than the diameter of the crystal semiconductor particles 1 ( For example, when the diameter of the crystalline semiconductor particles 1 is 300 μm, the gap width is 200 μm). Then, the etching solution is continuously supplied into the container 11, and the etching solution is discharged from the gap 12 of the container 11. As described above, since the etching process solution is continuously supplied and discharged, a new etching process solution can be continuously brought into contact with the crystalline semiconductor particles 1, so that the etching process can be performed smoothly.

  When the container 11 is rotated, the crystalline semiconductor particles 1 are attracted and pressed to the side as shown in FIG. 7B by the centrifugal force generated by the rotation. In order to press the crystalline semiconductor particles 1 against the side portion of the container 11, the rotational speed of the outer periphery of the container 11 may be 200 m / min or more.

  Similarly, the surface of the crystalline semiconductor particles 1 is washed away by discharging the etching treatment solution in the direction B by the centrifugal force generated by the rotation. And it is suppressed that a bubble adheres to the crystalline semiconductor particle 1, and it becomes possible to etch the surface of the crystalline semiconductor particle 1 uniformly.

  Ordinary etching has been performed by placing an object to be etched and an etching treatment solution in a beaker or the like and stirring the object to be etched and the etching treatment solution with a stirrer or the like. However, in that case, since bubbles generated by stirring adhere to the object to be etched, it is difficult to uniformly etch the surface of the object to be etched. On the other hand, in the method for producing crystalline semiconductor particles of this embodiment, bubbles can be removed, and the surface of the crystalline semiconductor particles can be uniformly etched.

  Examples of the shape of the container 11 include a columnar shape and a shape in which the upper portion is tapered as shown in FIG. In particular, since the evaporation of the etching treatment liquid can be suppressed because water / IPA vapor is difficult to escape to the outside, a shape in which the upper part is tapered is preferably used.

  The container 11 is made of a material that does not change depending on the etching solution.

  In addition, although the manufacturing method using the container 11 was described in the specific example mentioned above, if the manufacturing method of the photoelectric conversion apparatus of this invention moves an etching process solution relatively with respect to the crystalline semiconductor particle 1, as a result Bubbles generated on the crystalline semiconductor particles 1 can be removed.

(Process 2)
4A and 4B are cross-sectional views of the photoelectric conversion device in step 2 in the method for manufacturing a photoelectric conversion device of the present invention.

  Step 2 is a step of pressing and bonding the crystalline semiconductor particles 1 to one main surface of the conductive substrate 5.

  As a specific example of the bonding method, when aluminum is used as the conductive substrate 5 and silicon is used as the crystalline semiconductor grain 2, the eutectic portion 6 is formed at the interface by pressing and heating to a predetermined temperature. And can be joined via the eutectic part 6.

  For pressing the crystalline semiconductor particles 1 onto one main surface of the conductive substrate 5, a jig 4 used for pressing is used. For example, as shown in FIG. 4A, it is preferable that the crystalline semiconductor particles 1 are held and can be transported onto the conductive substrate 5 and can be pressed from the conductive substrate 5.

  In order for the jig 4 to hold the crystalline semiconductor particles 1 as described above, for example, as shown in FIG. 4A, the jig 4 preferably has a suction port 10.

  The heating temperature in the step 2 is the material of the crystalline semiconductor particles 1 such as aluminum that is the material of the conductive substrate 1 in order to form the eutectic portion 6 between the conductive substrate 5 and the crystalline semiconductor particles 1. The eutectic temperature with silicon or the like (577 ° C.) or higher is preferable.

  For example, as shown in FIG. 4A, the heating in step 2 is performed by pressing the conductive substrate 5 and the crystalline semiconductor particles 1 with the jig 4, and then, out of the main surface of the conductive substrate 5. This can be done by bringing the hot plate 7 into contact with the main surface opposite to the main surface in contact with the particles 1. Here, the hot plate may be formed, for example, by incorporating a heater in a heat resistant alloy.

  The manufacturing method of the present invention further includes (3) a step of forming an insulating layer between the crystalline semiconductor particles on one main surface of the conductive substrate so that the upper part of the crystalline semiconductor particles is exposed (hereinafter, And (4) a step of forming a translucent conductive layer on the top of the crystalline semiconductor particles and on the insulating layer (hereinafter referred to as step 4).

  These steps will be described with reference to FIG. 5A is a cross-sectional view of the photoelectric conversion device in Step 3, and FIG. 5B is a cross-sectional view of the photoelectric conversion device in Step 4.

(Process 3)
Step 3 is a step of forming the insulating layer 8 so that the upper part of the crystalline semiconductor particles 1 is exposed between the crystalline semiconductor particles 1 on one main surface of the conductive substrate 5. Further, in step 3, pn separation of the crystalline semiconductor particles 1 is also performed, for example, by etching the base of the crystalline semiconductor particles 1 with an acid such as hydrofluoric acid nitric acid.

  The insulating layer 8 formed between the crystalline semiconductor particles 1 is provided to separate the positive electrode and the negative electrode and is made of an insulating material.

  In step 3, the insulating material is softened by heating or the like, thereby filling between the crystalline semiconductor particles 1. In this case, the heating temperature is preferably lower than the eutectic temperature of the conductive substrate 5 and the crystalline semiconductor particles 1. This is because melting of the eutectic part (joint part) formed in step 2 can be prevented.

As the insulating material forming the insulating layer _8, to _{SiO 2, B 2 O 3,} Al 2 O 3, CaO, MgO, P 2 O 5, Li 2 O, SnO, ZnO, BaO, and TiO ₂ or the like as optional components Examples thereof include a low-temperature firing glass material comprising a material, a glass composition containing a filler comprising one or more of the above materials, and an organic material such as polyimide or silicone resin. The thickness of the insulating material is not particularly limited, and the light-transmitting conductive layer 9 provided on the insulating layer 8 may be provided uniformly.

(Process 4)
Step 4 is a step of forming a translucent conductive layer 9 on the top of the crystalline semiconductor particles 1 and on the insulating layer 8.

The translucent conductive layer 9 is formed by a sputtering method, a vapor phase growth method, a coating baking method, or the like. The translucent conductive layer 9 is composed of one or more oxide-based films selected from SnO ₂ , In ₂ O ₃ , ITO, ZnO, TiO _{2 and the} like.

  The translucent conductive layer 9 is preferably formed along the surface of the semiconductor portion 2 and along the concavo-convex portion 3 of the crystalline semiconductor particle 1. This is because carriers formed inside the crystalline semiconductor particles 1 can be efficiently collected.

  The translucent conductive layer 9 is preferably formed along the surface of the semiconductor layer and along the convex curved surface of the crystalline semiconductor particle 1. In this case, it is possible to efficiently collect carriers generated inside the crystalline semiconductor particles 1.

  Moreover, in the process 4, it is preferable to provide an electrode on the translucent conductive layer 9 (not shown). By providing the electrode in this way, a sufficient current collecting effect can be obtained. Further, by providing the finger electrode while avoiding the crystal semiconductor particle 1, it is possible to eliminate the formation of a shadow area directly by the finger electrode. The collected electricity is transmitted from the finger electrode to the outside.

  Further, in step 4, it is preferable to form a protective layer by CVD or PVD after forming the translucent conductive layer 9 (not shown). The protective layer preferably has a transparent dielectric property. For example, silicon oxide, cesium oxide, aluminum oxide, silicon nitride, titanium oxide, tantalum oxide, yttrium oxide, or the like can be used in a single composition or multiple compositions. A layer or a combination thereof formed on the semiconductor layer 2 or the light-transmitting conductive layer 9 can be used.

  Since the protective layer is on the light incident surface side, the protective layer needs to be transparent, and is an insulator in order to prevent current leakage between the semiconductor layer 2 or the translucent conductive layer 9 and the outside. It is necessary. In addition, if the thickness of the protective layer is optimized with respect to the wavelength of transmitted light, a function as an antireflection film can be provided.

  Hereinafter, the present invention will be described in detail based on examples. However, the present invention is not limited to the above-described embodiments and examples, and various modifications are made without departing from the gist of the present invention. be able to.

(Example)
The p-type crystalline silicon particle 1 having an average particle diameter (diameter) of 300 μm, which is a crystalline semiconductor particle, is subjected to a phosphorous thermal diffusion treatment so that the outer surface (surface layer) of the crystalline silicon particle is an n + layer. Part 2 was formed to form a pn junction.

  Next, the crystalline silicon particles formed with the pn junction are immersed for 30 minutes in a mixed aqueous solution of 1.5 wt% NaOH and 5 vol% IPA heated to 65-70 ° C. An uneven structure 3 was prepared (see FIG. 1). In the present drawing, the concavo-convex structure 3 on the surface layer of the crystalline silicon particles is indicated by a thick line, but in actuality, it is assumed that the concavo-convex structure as indicated by the tip of the arrow is shown.

  FIG. 2 shows data when the uneven structure 3 on the surface layer of the crystalline silicon particles at a magnification of 3000 is observed obliquely from above using a scanning electron microscope (SEM). From FIG. 2, the tip of the convex part of the obtained crystalline semiconductor particles showed a curved surface.

  Further, FIG. 3 shows data obtained when the concavo-convex structure 3 on the surface layer of the crystalline silicon particles at a magnification of 3500 is observed from above. From FIG. 3, the ten-point average roughness Rz in the concavo-convex structure is 0.1 to 3.5 μm, the width of the base of the convex part of the concavo-convex structure is 0.1 to 5.0 μm, and the convex part of the concavo-convex structure is 10 μm × It was found that there were 4-100 pieces per 10 μm.

  Next, a large number (10,000 particles) of crystalline silicon particles 1 having a concavo-convex structure 3 are arranged on the main surface of the conductive substrate 5 made of aluminum, with an interval of about 0.6 times the diameter thereof. And a silicon eutectic temperature of 577 ° C. or higher at 630 ° C. for about 10 minutes to bond a large number of crystalline silicon particles on the conductive substrate (reference numeral 6 indicates a eutectic portion). At that time, after the crystalline silicon particles are sucked and aligned by the jig 4 having the suction port 10, the jig 4 placed on the aluminum substrate 5 is pressed against the hot plate 7, and the crystalline silicon particles are applied to the aluminum substrate. They were joined (see (a) and (b) of FIG. 4).

  Next, the base of the crystalline silicon particles 1 bonded to the aluminum substrate 5 is etched with a mixed acid of hydrofluoric nitric acid to perform pn separation, and then an insulating layer made of polyimide between a large number of crystalline silicon particles on the aluminum substrate 5 8 was formed (see FIG. 5A).

  Then, an ITO film as the translucent conductive layer 9 was formed by sputtering so as to continuously cover the crystalline silicon particles 1 and the insulating layer 8 with a thickness of 80 nm, thereby producing a photoelectric conversion device (see FIG. 5 (b)).

(Comparative example)
The crystalline silicon particles in which the pn junction part was formed were immersed in an aqueous solution of 0.7 wt% NaOH at 70 to 80 ° C. for 30 minutes, so that the crystalline silicon particles 1 were textured, and the examples were the same as in the examples. A photoelectric conversion device was manufactured by the same method.

  FIG. 6 shows data when the uneven structure of the surface layer of the crystalline silicon particles in the comparative example is observed obliquely from above using a scanning electron microscope (SEM) at a magnification of 10,000 times. From FIG. 6, the tip of the convex part of the obtained crystalline semiconductor particles showed a sharp point as compared with the example of the present invention.

(Data comparison of Example and Comparative Example)
Using the photoelectric conversion devices obtained in the obtained Examples and Comparative Examples, the short-circuit current density (Jsc), open-circuit voltage (Voc), and fill factor (FF) were measured, and the conversion efficiency was calculated from these measured values. . The respective values are shown in Table 1.

  From Table 1, the photoelectric conversion apparatus of the Example showed high conversion efficiency.

  On the other hand, since the photoelectric conversion device of the comparative example has low Voc and FF, only low conversion efficiency was obtained. The reason for this is that since the tips of the convex portions of the crystalline semiconductor particles are sharp, chipping occurs at the tips of the convex portions that come into contact with the jig in the bonding process with the conductive substrate. It is thought that the part was missing.

(Example 2)
In the example, the manufacturing process of the concavo-convex structure of the crystalline silicon particles was performed by rotating the stirrer chip in the beaker. In Example 2, the concavo-convex structure of the crystalline silicon particles was manufactured in the container 11. Details will be described below.

  First, a mixed aqueous solution composed of 1.5 wt% NaOH and 5 vol% IPA was prepared in a separate container and heated to 65 to 70 ° C.

  Then, crystalline silicon particles are put into the container 11, the container is rotated at a speed of 270 m / min, the mixed aqueous solution is discharged from the gap 12 by centrifugal force, and the mixed aqueous solution in the container 11 is not depleted. A mixed aqueous solution of 65 to 70 ° C. was supplied into the container 11 from another container continuously from the top of the container.

  After the above operation is performed for 30 minutes, the supply of the mixed aqueous solution is stopped, and the container 11 is rotated at a rotational speed of 400 m / min for 1 minute to remove excess mixed aqueous solution from the crystalline silicon particles. Uneven structure 3 was produced.

(Data comparison between Example and Example 2)
FIG. 8 shows data when the concavo-convex structure 3 of the crystalline silicon particles of Example and Example 2 at a magnification of 3500 is observed from above using a scanning electron microscope (SEM). In addition, (a) shows the data of Example 2, (b) shows the data of Example.

  The concavo-convex structure of the crystalline semiconductor particle in FIG. 8 (a) has a concavo-convex structure in which the width of the base of the convex portion of the concavo-convex structure is 3.0 μm on average to 1.0 μm on average compared to the concavo-convex structure of the crystal semiconductor particle. The protrusions of 10 mm × 10 μm had an average of 10 to 100, and the unevenness was finer and uniform.

It is sectional drawing of the crystalline silicon particle which has an uneven structure on the surface. It is a drawing substitute photograph which observed the surface of the photoelectric conversion apparatus of this invention with the scanning electron microscope from diagonally upward. It is the drawing substitute photograph which observed the surface of the photoelectric conversion apparatus of this invention with the scanning electron microscope from upper direction. (A) And (b) is sectional drawing of the photoelectric conversion apparatus of the process in the manufacturing method of the photoelectric conversion apparatus of this invention. (A) And (b) is sectional drawing of the photoelectric conversion apparatus of the process in the manufacturing method of the photoelectric conversion apparatus of this invention. It is the drawing substitute photograph which observed the surface of the photoelectric conversion apparatus of the comparative example with the scanning electron microscope. (A) is a perspective view of the container 11, and (b) is a cross-sectional view of the container 11. FIG. 3 is a drawing-substituting photograph in which the surface of the photoelectric conversion device of the present invention is observed from above with a scanning electron microscope and shows data of Example 2. It is a drawing substitute photograph which observed the surface of the photoelectric conversion apparatus of this invention with the scanning electron microscope from upper direction, and shows the data of an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Crystal semiconductor particle 2 2nd conductivity type semiconductor part 3 Uneven structure 4 Jig 5 Conductive substrate 6 Eutectic part 7 Heat plate 8 Conductive substrate 9 Translucent conductive layer 10 Suction port 11 Container 12 Crevice A Etching solution Supply direction B Etching solution discharge direction C Container rotation direction

Claims (6)

  By performing an etching process on the surface of the spherical first conductive type crystalline semiconductor particles having the second conductive type semiconductor part formed on the surface layer using an etching process solution, the tip of the convex part is formed into a curved surface. The manufacturing method of the photoelectric conversion apparatus including the process 1 which forms the uneven structure formed on the surface of the said crystalline semiconductor particle. The etching treatment solution used for the etching treatment in the step 1 is
Sodium hydroxide,
At least one selected from the group consisting of isopropyl alcohol, lauric acid and n-octanoic acid;
The manufacturing method of the photoelectric conversion apparatus of Claim 1 containing this.   The method for manufacturing a photoelectric conversion device according to claim 2, wherein a concentration of sodium hydroxide in the etching treatment solution is 0.7 to 3%. The etching process in the step 1 is
Treating the crystalline semiconductor particles with the etching treatment solution;
The method for manufacturing a photoelectric conversion device according to claim 1, wherein the etching solution is moved relative to the crystalline semiconductor particles. The etching process in the step 1 has a gap on the side that can discharge the etching process solution to the outside and does not discharge the crystalline semiconductor particles to the outside, and the etching process solution is continuously supplied. In a container,
The crystalline semiconductor particles are processed while the crystalline semiconductor particles are pressed against the sides by the centrifugal force generated by rotating the container, and the etching solution supplied into the container is continuously discharged from the gap. The manufacturing method of the photoelectric conversion apparatus of Claim 4 which was made to do.   The method for manufacturing a photoelectric conversion device according to claim 1, further comprising a step 2 of pressing and bonding the crystalline semiconductor particles obtained in the step 1 to one main surface of a conductive substrate.