JP2011018683A - Thin-film solar cell and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the electric resistance between adjacent photoelectric conversion cells by improving coverage of conductive thin films in open grooves for connection even if the conductive thin films for connection are thinner than the thickness of photoelectric conversion layers.SOLUTION: In the thin-film solar cell, a plurality of thin-film solar cell elements are disposed on a transparent insulating substrate 1 while sandwiching a groove 22 for connection, and thin-film solar cell elements are mutually connected in series within the groove 22 for connection. The thin-film solar cell includes an inclination part 8 made of an insulating material on a side within the groove 22 for connection. By a conductive film 6 formed on an incline at the inclination part 8, a rear side of one of the adjacent thin-film solar cell elements is electrically and serially connected to a front side of the other thin-film solar cell element.

Description

  The present invention relates to a thin film solar cell having an integrated structure and a method for manufacturing the same.

  As a photoelectric conversion device that converts light energy into electrical energy, a thin film solar cell in which a first conductive layer, a photoelectric conversion layer, and a second conductive layer are sequentially stacked on a substrate is known. The photoelectric conversion layer is generally a semiconductor, and a three-layer stacked pin diode structure of a p-type layer, a high-resistance i layer, and an n-type layer is used. As a semiconductor material for the photoelectric conversion layer, there are amorphous silicon mainly containing silicon, microcrystalline silicon, a mixed material of silicon and germanium, and the like. The photoelectric conversion layer of these films can be formed by, for example, a plasma CVD method using a source gas containing silicon such as silane gas. In addition, compound semiconductor materials such as I-III-VI group compounds are also used as semiconductor materials.

  The first conductive layer and the second conductive layer serve as electrodes for extracting electric power (current) converted by the photoelectric conversion layer. Of the first conductive layer and the second conductive layer, the surface electrode on the light incident side is made of a transparent electrode made of a conductive film material having transparency. In addition, among the first conductive layer and the second conductive layer, the back electrode on the side opposite to the light incident side is made of a highly reflective metal material that reflects light toward the photoelectric conversion layer.

  In solar cells installed outdoors, a super straight structure is often used in which a transparent insulating glass substrate is installed on the light incident side. The photoelectric conversion element is formed on the back surface side of the glass substrate, and the back surface side is further covered with a sealing sheet so that it is not easily affected by humidity or the like.

  In the thin film solar cell, an integrated structure in which the photoelectric conversion layer on the substrate is divided into a plurality of unit cells by grooves or the like is used. The groove for dividing the photoelectric conversion layer and the electrode is formed using a laser scribing method in which a laser beam is irradiated and the photoelectric conversion layer and the electrode in the irradiated portion are removed by the heat. In this integrated structure, a structure in which a first conductive layer of a certain unit cell and a second conductive layer of an adjacent unit cell are electrically connected in series is common. Connection between the first conductive layer (transparent conductive layer) and the second conductive layer (back electrode layer) of adjacent unit cells is made through a groove formed in the photoelectric conversion layer.

  In addition, a thin film solar cell is known to have a tandem structure in which the conversion efficiency is increased by extending the light absorption wavelength range. In the tandem type, the photoelectric conversion layer has a stacked structure of a first semiconductor photoelectric conversion layer and a second semiconductor photoelectric conversion layer having different light absorption wavelength characteristics. In general, a photoelectric conversion layer that absorbs light in a short wavelength region is provided on the front surface side where light enters, and a photoelectric conversion layer that absorbs light in a long wavelength region is provided on the back surface side. When all the photoelectric conversion layers are semiconductors, a semiconductor configuration with a large band gap on the front surface side and a semiconductor configuration with a small band gap on the back surface side is taken.

  In Patent Document 1, a transparent electrode layer, a silicon photoelectric conversion unit layer, and a back electrode layer laminated on a transparent insulating substrate are separated by a plurality of separation grooves so as to form a plurality of photoelectric conversion cells. An integrated thin film solar cell is shown in which are connected in series. A connection opening groove for electrically connecting adjacent photoelectric conversion cells in series is formed between the groove for separating the transparent electrode layer between the cells and the groove for separating the back electrode layer. The groove is formed so that the crystalline silicon photoelectric conversion unit layer is removed by laser scribing and the transparent electrode layer is exposed at the bottom. Then, a metal back electrode layer is buried in the groove to connect the photoelectric conversion unit layer of one cell and the transparent electrode layer of the adjacent cell.

JP 2001-267613 A

  In the integrated thin film solar cell as described above, a conductive thin film is formed in the connection opening groove formed by removing the photoelectric conversion layer and on the photoelectric conversion layer, and electrical connection between adjacent cells is made. Is done. However, when examining the structure of such a thin film solar cell, the inventors have found that the electrical resistance between the back surface of the photoelectric conversion layer, the adjacent transparent electrode layer, and the transparent electrode layer of the adjacent cell often increases. When the electrical resistance between the cells increases, the photoelectric conversion efficiency decreases. This problem is likely to occur when the thickness of the photoelectric conversion layer is sufficiently larger than the thickness of the conductive film formed in the connection opening groove. As a result of the investigation, it was estimated that one of the causes was insufficient coverage of the conductive layer in the opening groove for connection. For example, when the opening groove for connection is removed from the transparent insulating substrate by laser scribing that irradiates a laser beam, the side surface of the groove is generally perpendicular to the substrate, but when observed in detail, the side surface is uneven, especially the side surface. Overhanging part of the. In particular, when the side surface of the groove near the boundary with the transparent electrode layer is in an overhang shape, the conductive film becomes thin or interrupted at that portion, and the electrical resistance is remarkably increased.

  Therefore, the present invention solves such a problem and improves the coverage of the conductive film in the connection opening groove even when the conductive film for connection is thinner than the thickness of the photoelectric conversion layer. It aims at reducing the electrical resistance between photoelectric conversion cells.

  The thin film solar cell of the present invention is a thin film solar cell in which a plurality of thin film solar cell elements are arranged on a transparent insulating substrate with a connection groove interposed therebetween, and the thin film solar cell elements are mutually connected in series within the connection groove. And having a slope portion made of an insulating material on a side surface in the connection groove, and a conductive film formed on the slope surface of the slope portion, and a back surface side of one adjacent thin film solar cell element The thin film solar cell is electrically connected in series with the surface side of the other thin film solar cell element.

  In the method for manufacturing a thin film solar cell of the present invention, a plurality of thin film solar cell elements are arranged on a transparent insulating substrate with a connection groove interposed therebetween, and adjacent thin film solar cell elements are connected in series in the connection groove. A thin film solar cell manufacturing method, comprising: a laminating step of laminating a transparent electrode having a transparent electrode separation groove on the transparent insulating substrate; and a photoelectric conversion layer on the transparent electrode; and the adjacent thin film solar cell A connecting groove forming step of forming a connecting groove so as to remove the photoelectric conversion layer between the battery elements and exposing the connecting portion of the transparent electrode at the bottom; and a back surface side of the photoelectric conversion layer and the connecting groove An insulating film forming step of forming an insulating film in the inner surface, removing the insulating film on the back surface side of the photoelectric conversion layer and the connecting portion of the transparent electrode at the bottom in the connecting groove, and An inclined portion made of the insulating film is formed on the side surface in the groove for use. Forming a conductive film that is continuous with the back surface side of the photoelectric conversion layer, the inclined surface of the inclined portion, and the connecting portion of the transparent electrode, and the conductivity between the thin-film solar cell elements. And a step of separating the film.

  The thin film solar cell of the present invention has an inclined portion made of an insulating material on the side surface of the connecting groove, and a conductive film formed on the inclined surface of the inclined portion, and the back surface side of one adjacent thin film solar cell element Since the surface side of the other thin film solar cell element is electrically connected in series, even when the conductive film is thin, the coverage of the conductive film in the opening groove for connection is improved and the electricity between adjacent photoelectric conversion cells is improved. Resistance can be reduced.

  In addition, as a manufacturing method thereof, an insulating film forming step of forming an insulating film on the back surface side of the photoelectric conversion layer and in the connection groove, and a connection between the back surface side of the photoelectric conversion layer and the transparent electrode at the bottom in the connection groove And the step of forming the inclined portion made of the insulating film on the side surface in the connecting groove by removing the insulating film on the connecting portion, the inclined portion having a narrow width can be easily formed.

It is a perspective view which shows the structure of the thin film solar cell of Embodiment 1 of this invention. It is a fragmentary sectional view which shows the structure of the thin film solar cell of Embodiment 1 of this invention. It is sectional drawing explaining the manufacturing method of the thin film solar cell of Embodiment 1 of this invention. It is sectional drawing explaining the manufacturing method of the thin film solar cell of Embodiment 1 of this invention. It is sectional drawing explaining the manufacturing method of the thin film solar cell of Embodiment 1 of this invention. It is sectional drawing explaining the manufacturing method of the thin film solar cell of Embodiment 1 of this invention. It is sectional drawing explaining the manufacturing method of the thin film solar cell of Embodiment 1 of this invention. It is sectional drawing explaining the manufacturing method of the thin film solar cell of Embodiment 1 of this invention. It is sectional drawing explaining the manufacturing method of the thin film solar cell of Embodiment 2 of this invention. It is sectional drawing explaining the manufacturing method of the thin film solar cell of Embodiment 2 of this invention. It is sectional drawing explaining the manufacturing method of the thin film solar cell of Embodiment 2 of this invention. It is sectional drawing explaining the manufacturing method of the thin film solar cell of Embodiment 2 of this invention. It is sectional drawing explaining the partial structure of the thin film solar cell of Embodiment 2 of this invention. It is sectional drawing explaining the manufacturing method of the thin film solar cell of Embodiment 3 of this invention. It is sectional drawing explaining the manufacturing method of the thin film solar cell of Embodiment 3 of this invention. It is sectional drawing explaining the partial structure of the thin film solar cell of Embodiment 3 of this invention. It is sectional drawing explaining the manufacturing method of the thin film solar cell of Embodiment 4 of this invention. It is sectional drawing explaining the manufacturing method of the thin film solar cell of Embodiment 4 of this invention. It is sectional drawing explaining the manufacturing method of the thin film solar cell of Embodiment 4 of this invention. It is sectional drawing explaining the partial structure of the thin film solar cell of Embodiment 4 of this invention.

  Embodiments of a thin film solar cell and a method for manufacturing the same according to the present invention will be described below with reference to the drawings. In addition, this invention is not limited to the following description, In the range which does not deviate from the summary of this invention, it can change suitably. In the drawings shown below, the scale of each member may be different from the actual scale for easy understanding. The same applies between the drawings. Further, in the embodiment, the same components are denoted by the same reference numerals, and the detailed description of the components described in one embodiment will be omitted in another embodiment.

<Embodiment 1. >
FIG. 1 is a perspective view showing the structure of the thin-film solar cell of the first embodiment, and is a view seen from the back side. In the thin film solar cell 100, a plurality of thin film solar cell elements 11 are arranged on the transparent insulating substrate 1. The thin film solar cell 100 is a solar cell that photoelectrically converts light S incident from the surface side of the transparent insulating substrate 1 opposite to the thin film solar cell element 11. The thin film solar cell element 11 has a structure in which a transparent electrode 2, a photoelectric conversion layer 4, and a back electrode 6 are laminated in order from the transparent insulating substrate 1 side. The photoelectric conversion layer 4 used in Embodiment 1 has a tandem structure in which a first photoelectric conversion layer 41, an intermediate layer 43, and a second photoelectric conversion layer 42 are stacked in this order from the substrate side. A part of the light S incident from the transparent insulating substrate 1 side is subjected to photoelectric conversion by the first photoelectric conversion layer 41, and the rest passes through the intermediate layer 43, and further photoelectrically converted by the second photoelectric conversion layer 42 in the subsequent stage. Is done. The intermediate layer 43 has conductivity, and the first photoelectric conversion layer 41 and the second photoelectric conversion layer 42 are connected in series in the thin film solar cell element 11. Electric power generated from the electrodes of the elements located at both ends of the plurality of thin film solar cell elements 11 connected in series with each other is taken out. Although the tandem structure is used in Embodiment 1, a structure including only a single photoelectric conversion layer may be used.

  Adjacent thin film solar cell elements 11 are separated by grooves formed in the transparent electrode 2, the photoelectric conversion layer 4, and the back electrode 6. The thin film solar cell of Embodiment 1 has a transparent electrode separation groove 21 that separates the transparent electrode 2 and a back electrode separation groove 23 that separates the back electrode 6. A connection groove 22 is formed between the transparent electrode separation groove 21 and the back electrode separation groove 23. One back electrode 6 of an element adjacent in the connection groove 22 is electrically connected to the other transparent electrode 2, and the elements are connected in series. In the first embodiment, a typical thin-film solar cell element 11 has an elongated rectangular shape. However, the thin-film solar cell element 11 is not necessarily rectangular. In the figure, it is shown that the narrow photoelectric conversion layer 4 remains between the connection groove 22 and the back electrode separation groove 23 to form an island-shaped portion 25. The island portion 25 is not essential, and the back electrode separation groove 23 may be integrated with the connection groove 22.

  FIG. 2 is a cross-sectional view showing a partial structure of the thin-film solar cell of the first embodiment, and shows a cross section in a direction perpendicular to the substrate at the dotted line X1-X2 in FIG. This figure shows the structure of the connecting portion of adjacent thin film solar cell elements 11. The back side of the photoelectric conversion layer 4 of one element A and the substrate side of the other element B are connected in series via the connection groove 22. In the first embodiment, the back surface continues from the back surface of the photoelectric conversion layer 4 of one element A through the side surface in the connection groove 22 to the transparent electrode 2 of the other element B exposed at the bottom of the connection groove 22. Electrode 6 is formed. The structure in which electrical connection is made via the side surface in the connection groove 22 does not necessarily require the back electrode 6 and the transparent electrode 2 to be in direct contact. For example, another conductive film may be formed in the connection groove 22. May be.

  An inclined portion 8 made of an insulating material is provided on a side surface in the connection groove 22, and a conductive film such as a back electrode 6 that connects elements in series is formed on the inclined portion 8. In the connecting groove 22, the thickness of the inclined portion 8 from the side surface of the photoelectric conversion layer 4 to the surface of the inclined portion 8 is thin on the back electrode 6 side and becomes thicker as it approaches the transparent electrode 2. For this reason, the surface of the inclined portion 8 has a shallower angle than perpendicular to the substrate. For example, even if the angle of the side surface of the photoelectric conversion layer 4 with respect to the substrate is 90 degrees or partially has an overhanging portion of 90 degrees or more, the angle of the surface of the inclined portion 8 with respect to the substrate is 70 to 80 degrees or the like. it can. Since the conductive film that electrically connects the elements is formed on the inclined portion 8, the inclination at the side surface portion becomes gentle, and disconnection hardly occurs on the inner surface of the connection groove 22, and the elements are connected in series. Defects and resistance increase can be prevented.

3-8 is sectional drawing explaining the manufacturing method of the thin film solar cell of this Embodiment 1, and shows the same part as FIG. Processes other than the formation of the inclined portion 8 may be the same as the manufacturing method disclosed in, for example, Japanese Patent Application Laid-Open No. 2001-267613. First, as shown in FIG. 3, a transparent insulating substrate 1 such as glass on which a transparent electrode 2 made of a transparent conductive material mainly composed of SnO ₂ , ZnO or the like is formed is prepared. The transparent electrode 2 is formed with a transparent conductive film having a thickness of, for example, 0.3 to 1 micron by sputtering or CVD, and then a transparent electrode separation groove 21 for separating elements is formed by laser scribing or the like. In the figure, a transparent electrode separation groove 21 indicates a groove extending in a direction perpendicular to the paper surface. Fine irregularities may be formed on the transparent electrode 2.

Next, as shown in FIG. 4, the photoelectric conversion layer 4 is formed on the transparent electrode 2. In the first embodiment, the photoelectric conversion layer 4 includes a first photoelectric conversion layer 41 made of an amorphous silicon layer, an intermediate layer 43 made of a light-transmitting conductive material, and a second photoelectric conversion layer 42 made of a microcrystalline silicon layer in order. Laminate. The first photoelectric conversion layer 41 and the second photoelectric conversion layer 42 made of these semiconductor materials can be formed by a plasma CVD method using a semiconductor material gas such as a silane gas. For example, the thickness of the amorphous silicon layer is 0.3 to 0.5 microns, and the thickness of the microcrystalline silicon layer is 2 to 4 microns. In these semiconductor layers, p-type and n-type layers to which impurities are added with a high-resistance i-type layer interposed are formed on the substrate side and the back side. The intermediate layer 43 is an oxide film such as ZnO or SiO _X (0 <X <2), and has a thickness of about several to 100 nm. In addition to the above-described layer structures and materials, various other semiconductor materials and conductive materials can be used, and their thicknesses can be changed. It is good also as the photoelectric converting layer 4 which consists of one semiconductor layer.

  Next, a connection groove 22 is formed as shown in FIG. A groove is formed in the photoelectric conversion layer 4 and the transparent electrode 2 is exposed at the bottom. If the photoelectric conversion layer 4 is a semiconductor layer containing silicon, germanium, or the like, it is relatively easy to form a groove by a laser scribing method using a visible laser. When the light beam of the second harmonic of the YAG pulse laser is irradiated from the front side of the transparent insulating substrate 1, the light beam that has passed through the transparent insulating substrate 1 and the transparent electrode 2 is absorbed by the photoelectric conversion layer 4, and the photoelectric conversion layer 4 has a high temperature. It is removed by a phenomenon such as evaporation. When a light beam is scanned along the groove in the immediate vicinity of the transparent electrode separation groove 21, the photoelectric conversion layer 4 is removed in a groove shape. In this case, the width of the connecting groove 22 depends on the condensing size of the light beam, and a typical width is 30 to 100 microns. The method for forming the connection groove 22 is not limited to such a laser scribing method, and a dry etching method in which silicon is etched with plasma of a reactive gas using a mask may be used. Although a step of forming a mask is required, it is possible to form a connection groove 22 that is narrower than that of the laser scribing method.

  Next, as shown in FIG. 6, an insulating film 18 is formed. An insulating film 18 is formed so as to cover the entire back surface of the thin film battery 100, and the insulating film 18 is also attached to the side surface of the connection groove 22. In the first embodiment, since the insulating film 18 is processed by anisotropic etching as described later, a material that can be easily etched is desirable. For example, when a silicon oxide film formed by plasma CVD using tetraethoxysilane (TEOS) and an oxidizing gas is used as the insulating film 18, the side surface of the connection groove 22 is satisfactorily covered and anisotropic etching is easy. So good. In the plasma CVD method, a layer is uniformly formed even on a wall surface close to vertical, so that the layer is continuously formed on the photoelectric conversion layer 4, the side surface of the photoelectric conversion layer 4, and the transparent electrode 2 at the bottom of the connection groove 22. It is formed. The thickness of the insulating film 18 is desirably a film that is somewhat thicker than the thickness of the photoelectric conversion layer 4. For example, it may be 30% or more of the thickness of the photoelectric conversion layer 4, more preferably 50% or more, and even more preferably equal to or more than the thickness of the photoelectric conversion layer 4. In the case of a tandem-type thin film battery, the thickness is preferably equal to or greater than the thickness of the photoelectric conversion layer 4 on the substrate side. As the material of the insulating film 18, in the case of a photoelectric conversion layer mainly composed of silicon, the silicon oxide film as described above is excellent in terms of adhesion and the like, but not limited thereto, other materials are used. There may be. Further, as the film forming method, an isotropic film forming method in which the film thicknesses attached to the upper surface portion and the side surface portion are almost the same is excellent in terms of coverage, such as plasma CVD or sputtering. A film forming method using a plasma atmosphere is preferable.

Next, as shown in FIG. 7, the insulating film 18 is anisotropically etched. Anisotropic etching is etching with different etching rates depending on the direction. In particular, the anisotropic etching in the case of the first embodiment is such that the etching rate in the direction perpendicular to the substrate surface is several times to 10 times or more compared to the etching rate in the direction horizontal to the substrate surface. Big enough. As such an anisotropic etching method, for example, reactive ion etching including a parallel plate type electrode pair may be used. When the insulating film 18 is a silicon oxide material, a hydrocarbon-based gas containing fluorine such as CHF ₃ or C ₂ F ₆ can be used as an etching gas. By such anisotropic etching, the inclined portion 8 made of the insulating film 18 is formed on the side surface of the photoelectric conversion layer 4 in the connection groove 22. On the other hand, the insulating film 18 on the photoelectric conversion layer 4 and on the connection portion of the transparent electrode 2 in the connection groove 22 is removed, and these portions are exposed. Such an inclined portion 8 is also referred to as a sidewall, and the thickness from the side surface increases as it approaches the substrate from above. Note that when the entire insulating film 18 is dry-etched with the gas as described above, even a part of the photoelectric conversion layer 4 containing silicon as a main component may be etched. Therefore, after the reactive ion etching is performed so that the insulating film 18 remains a little, the photoelectric conversion layer 4 can be prevented from being etched by removing it by wet etching such as hydrofluoric acid.

  Further, a method by wet etching may be used as a method for anisotropic etching. For example, when shower etching is performed with a silicon oxide etchant such as ammonium fluoride, the etchant hits the silicon oxide insulating film 18 from the upper surface side, so that etching proceeds from the top to the bottom. When the etching is completed when the insulating film 18 between the upper part of the photoelectric conversion layer 4 and the upper part of the transparent electrode 2 disappears, the insulating film 18 remains on the side surface portion of the photoelectric conversion layer 4, and the surface thereof is an etching solution. It becomes a shape with a taper along the flow. Moreover, it is preferable to use such wet etching because the surface of the inclined portion 8 becomes a smooth surface and the coverage of the conductive film is further improved.

Next, as shown in FIG. 8, the back electrode 6 is formed, and the back side of the photoelectric conversion layer 4 of one thin film battery element and the transparent electrode 2 of the other thin film battery element are electrically connected. The back electrode 6 is formed so as to cover the entire back surface of the thin film battery 100, and is attached so as to be continuous from the back surface of the photoelectric conversion layer 4 to the side surface and the bottom surface of the connection groove 22. The back electrode 6 is a conductive film made of Ag, Al, or an alloy material thereof. The typical thickness of the film is 0.2-0.5 microns, etc. The back electrode 6 is formed on the inclined surface of the inclined portion 8 on the side surface of the connection groove 22. It is desirable that the back electrode 6 be formed by sputtering using Ar gas plasma or the like so that the coverage on the side surface in the connection groove 22 is improved. Thereafter, a back electrode separation groove 23 for separating the back electrode 6 between the elements is formed. The back electrode separation groove 23 can be formed by a laser scribing method similar to the case where the connection groove 22 is formed. When the photoelectric conversion layer 4 is evaporated by the laser irradiated from the substrate side, the upper surface back electrode 6 is also peeled off simultaneously to form a groove. A thin film solar cell is formed through the above steps.
In addition, although the above connected the back surface of the photoelectric conversion layer 4 and the transparent electrode 2 via the back surface electrode 6 attached to the inclined surface of the inclined portion 8, the connection was made using a conductive film for connection other than the back surface electrode 6. May be. For example, after forming the back electrode 6 on the photoelectric conversion layer 4, the connecting groove 22 is formed, and then the inclined portion 8 is formed, and 0.2 to 0.5 is formed on the inclined surface of the inclined portion 8. A conductive film having a micron thickness is formed, and a separation groove is formed in this conductive film in the same manner as the back electrode separation groove 23 described above. Even in this case, a thin film solar cell similar to the above is formed.

  If the back electrode 6 and the conductive film for connection are made as thick as the photoelectric conversion layer 4, the coverage in the connection groove 22 is improved, but the elements can be separated by the back electrode separation groove 23. It becomes extremely difficult to cause problems such as short-circuiting by the back electrode 6 and the conductive film that are insufficiently separated.

  The side surface obtained by processing the photoelectric conversion layer 4 by a laser scribing method or the like is largely uneven, and often has a vertical or overhang portion. When a conductive film is formed on such a side surface, a portion that is not covered or disconnected is generated even if a sputtering method or the like is used. In particular, the influence is large in a structure in which the thickness of the photoelectric conversion layer is one digit or more larger than that of the conductive film. Further, in the case where the photoelectric conversion layer includes a microcrystalline semiconductor layer, unevenness is easily generated on the side surface, which is greatly affected. Although a method of increasing the thickness of the conductive film is also conceivable, in that case, not only the material increase but also the processing for separating the conductive film between elements becomes difficult, resulting in a decrease in yield and an increase in cost. In the structure of the first embodiment, even when the conductive film is thin, the coating in the connection groove 22 is good, and the elements can be connected with low resistance. Further, if the surface of the inclined portion 8 is made smooth by wet etching or the like, it is desirable that disconnection hardly occurs even when the back electrode 6 is thin.

  In addition, since the insulating film 18 having a thickness of several tens% to the same thickness as the thickness of the photoelectric conversion layer 4 is processed into the inclined portion 8, the thickness is smaller than the thickness of the photoelectric conversion layer 4. For this reason, even if it is the narrow connection groove | channel 22, since the contact area of the back surface electrode 6 and the transparent electrode 2 can be enlarged enough, it can connect to low resistance. A method of applying a liquid resin to the side surface of the connecting groove 22 to form an insulating portion having an inclined surface is also conceivable, but in that case, the width of the insulating portion is that of the photoelectric conversion layer 4 due to the fluidity of the coating resin. The width of the connecting groove 22 needs to be sufficiently wide in order to be much wider than the thickness and expose the transparent electrode 2. Therefore, the structure of the first embodiment can achieve both good electrical connection between elements and an increase in the light receiving area due to the narrow width of the connection groove 22, thereby realizing a highly efficient solar cell.

  Furthermore, in the case of a tandem solar cell, loss due to leakage current on the side surface can be prevented by the inclined portion 8 made of an insulating material. In the tandem-type thin film solar cell, an n-type or p-type low-resistance layer is exposed near the boundary between different light conversion layers, in the first embodiment, near the intermediate layer 43. If a conductive film is formed directly on these, a short circuit occurs and a loss due to leakage current occurs. It is preferable that the inclined portion 8 covers the side portions of these low resistance layers. For example, the side electrical parts of the photoelectric conversion layer 41 formed on the substrate side may be covered. According to the first embodiment, since the inclined portion 8 is obtained by processing the insulating film 8 once formed, the inclined portion 8 has a thickness sufficient to prevent a leakage current of at least 0.1 microns or more. Is easy.

  In addition, although it is most desirable to cover the inclined part 8 to the upper end part of the side surface of the photoelectric conversion layer 4, it is not essential. For example, even if the upper end portion of the inclined portion 8 is, for example, the upper end of the inclined portion 8 being in the middle of the thickness of the photoelectric conversion layer 4, the boundary portion between the transparent electrode 2 and the side portion can be inclined, and the connection between the portions becomes good. Therefore, an effect of improving the inter-element connectivity can be obtained.

<Embodiment 2. >
FIG. 13 is a cross-sectional view for explaining a partial structure of the thin-film solar cell of the second embodiment, and shows the same portion as that of FIG. 2 of the first embodiment. 9-12 is sectional drawing explaining the manufacturing method of the thin film solar cell of this Embodiment 2. FIG. The thin film solar cell of the second embodiment is basically the same as that of the first embodiment, but the formation method and material of the inclined portion 8 are different. The inclined portion 8 of the second embodiment is made of an insulating resin material. Below, the formation method is demonstrated.

  After forming the connecting groove 22 as shown in FIG. 5 of the first embodiment, the insulating film 18 made of a liquid resin material is applied and formed so as to fill the connecting groove 22 as shown in FIG. After that, after the solvent contained in the resin material is removed by baking and solidified, the insulating film 18 adhered on the photoelectric conversion layer 4 is removed by oxygen plasma treatment or the like as shown in FIG. Only 22 is left. Further, as shown in FIG. 11, the insulating film 18 in the connection groove 22 is processed so that the central portion is removed except for the side portion of the connection groove 22. This processing can be performed by irradiating the insulating film 18 with a laser beam from the back side. The size of the laser beam is preferably a groove slightly narrower than the width of the connection groove 22. Further, as shown in FIG. 12, the insulating film 18 on the side of the connection groove 22 is deformed by heating. Thereby, the insulating film 18 becomes the inclined portion 8 inclined toward the substrate side. Further, a back electrode 6 is formed thereon to electrically connect the back side of the photoelectric conversion layer 4 of one cell A and the transparent electrode 2 of the other cell B. Finally, the back electrode separation groove 23 is formed to complete the thin film solar cell of the second embodiment shown in FIG.

  In the second embodiment, the resin material once solidified after application is processed so as to remain only on the side portion of the connection groove 2, and then the portion is deformed to form the inclined portion 8. Therefore, the narrow inclination Part 8 can be fabricated. For example, the width of the inclined portion 8 may be equal to the thickness of the photoelectric conversion layer 22. The width of the inter-element connection portion C can be narrowed to increase the area of the light receiving portion.

<Embodiment 3. >
FIG. 16 is a cross-sectional view for explaining a partial structure of the thin-film solar cell of the third embodiment, and shows the same portion as that of FIG. 2 of the first embodiment. 14-15 is sectional drawing explaining the manufacturing method of the thin film solar cell of this Embodiment 3. FIG. The thin film solar cell of the third embodiment is basically the same as that of the first embodiment, but has a transparent conductive layer 33 made of a metal oxide on the photoelectric conversion layer 4. This transparent conductive layer 33 is a layer formed by sputtering, for example, ZnO.

  Basically, the manufacturing process is the same as in the first embodiment, but the transparent conductive layer 33 is used as an etching stopper during the anisotropic etching of the inclined portion 8. For this reason, a material whose etching rate of the transparent conductive layer 33 is smaller by one digit or more than the etching rate of the insulating film 18 is used as an etching gas or liquid. After forming the insulating film 18 as shown in FIG. 14, when the insulating film 18 is anisotropically etched as shown in FIG. 15, the etching stops when the etching reaches the transparent conductive layer 33, so that the photoelectric conversion layer 4 is etched. Can be easily prevented. Since the transparent conductive layer 33 such as ZnO is used as a stopper, the back electrode 6 can be formed directly on the transparent conductive layer 33, and the manufacture is easy. Thereafter, by forming the back electrode 6 and the back electrode separation groove 23 on the transparent conductive layer 33, the thin film solar cell of the third embodiment as shown in FIG. 16 is completed.

<Embodiment 4. >
FIG. 20 is a cross-sectional view for explaining a partial structure of the thin-film solar cell according to the fourth embodiment, and shows the same portion as FIG. 2 according to the first embodiment. 17-19 is sectional drawing explaining the manufacturing method of the thin film solar cell of this Embodiment 4. FIG. The thin-film solar cell of the fourth embodiment is basically the same as that of the first embodiment, but the inclined portion 8 in the connection groove 22 includes an insulating film 18 having an inclined surface and the photoelectric conversion layer 4. A thin second insulating film 28 is provided between the side surface and the transparent electrode 2. The insulating film 18 and the second insulating film 28 are made of different materials, and the second insulating film 28 is used as a stopper when the insulating film 18 is anisotropically etched using the difference in etching characteristics.

  For example, the insulating film 18 is a film made of an organic resin material, and the second insulating film 28 is a silicon oxide or silicon nitride film, for example. The insulating film 18 made of an organic resin material is processed by anisotropic etching with oxygen plasma or the like to form an inclined surface. At this time, since the second insulating film 28 is not etched by oxygen plasma, the etching is stopped when the second insulating film 28 is exposed. Thereafter, the second insulating film 28 is removed using an appropriate etching solution or the like.

  The insulating film 18 is substantially insulative even if it is not completely insulative if it has a sufficiently high resistance, such as a resistivity of 3 digits or more as compared with the n layer or p layer in the photoelectric conversion layer 4. Can be used as A non-doped polysilicon film may be used as the insulating film 18. In that case, anisotropic dry etching is preferably performed using the second insulating film 28 as silicon oxide and a halogen-based etching gas.

  After processing the connection groove 22, as shown in FIG. 17, the second insulating film 28 is formed so as to cover the entire exposed portion on the back surface side of the photoelectric conversion layer 4. When the second insulating film 28 is a silicon oxide film or a silicon nitride film, it can be formed using a sputtering method or a plasma CVD method. The second insulating film 28 also adheres to the side surface of the photoelectric conversion layer 4 in the connection groove 22. However, as described above, when the connecting groove 22 has the reverse tapered portion or the like, it is difficult to cover these portions, and it is not always necessary to completely cover the entire surface. An insulating film 18 is further formed on the second insulating film 28. The insulating film 18 made of an organic resin material is, for example, a polyparaxylylene film using a chemical vapor deposition method under reduced pressure and can be satisfactorily covered also in the connection groove 22. When a polysilicon film is used as the insulating film 18, it can be formed by a plasma CVD method using silane gas.

  Next, as shown in FIG. 18, the insulating film 18 is processed by anisotropic etching to form an inclined surface. Thereafter, the second insulating film 28 on the back surface side of the photoelectric conversion layer 4 is removed as shown in FIG. If it is silicon oxide, it can be easily removed with a hydrogen fluoride aqueous etching solution.

  Thereafter, by forming the back electrode 6 and the back electrode separation groove 23, the thin film solar cell of the fourth embodiment as shown in FIG. 20 is completed. As described above, in Embodiment 4, the insulating film is formed by stacking a plurality of films made of different materials, and the films made of different materials are etched using different etching methods. Since the inclined portion 8 is formed using two films having different etching characteristics, it is easy to stop the etching and the workability is excellent.

  As described above, in the thin film solar cell of the present invention, a plurality of thin film solar cell elements 11 are arranged on the transparent insulating substrate 1 with the connection groove 22 interposed therebetween, and the thin film solar cell elements 11 are connected within the connection groove 22. A thin film solar cell 100 connected in series with each other, which has an inclined portion 8 made of an insulating material on the side surface in the connecting groove 22 and is adjacent to each other by a conductive film formed on the inclined surface of the inclined portion 8. The back surface side of one thin film solar cell element 11 and the front surface side of the other thin film solar cell element 11 are electrically connected in series. For this reason, even if it is the connection groove | channel 22 which has a part of a reverse taper partially, a favorable electrical connection is attained with a thin electroconductive film. Leakage current through the side surface in the connection groove 22 can be prevented. Further, it is desirable to make the width of the inclined portion 8 less than twice the thickness of the photoelectric conversion layer 4, or more preferably less than the same thickness, because the width of the inter-element connection portion C that does not contribute to power generation can be reduced.

  In the method for manufacturing a thin film solar cell of the present invention, a plurality of thin film solar cell elements 11 are arranged on the transparent insulating substrate 1 with the connection groove 22 interposed therebetween, and the adjacent thin film solar cell elements 11 are connected to the connection groove 22. In which a transparent electrode 2 having a transparent electrode separation groove 21 on a transparent insulating substrate 1 and a photoelectric conversion layer 4 are laminated on the transparent electrode 2. A stacking step, a connecting groove forming step of removing the photoelectric conversion layer 4 between the adjacent thin-film solar cell elements 11 and exposing the connecting portion of the transparent electrode 2 at the bottom, and a photoelectric conversion An insulating film forming step for forming an insulating film 18 on the back surface side of the layer 4 and in the connection groove 22; on the back surface side of the photoelectric conversion layer 4; and on the connection portion of the transparent electrode 2 at the bottom in the connection groove 22. The insulating film 18 is removed, and the insulating film 1 is formed on the side surface in the connecting groove 22. A step of forming an inclined portion 8 made from the above, a step of forming a conductive film continuous with the back surface side of the photoelectric conversion layer 4, on the inclined surface of the inclined portion 8, and the connecting portion of the transparent electrode 2, and a thin film solar cell element 11 to separate the conductive film between the two. According to this method, since the inclined portion 8 is formed by processing the insulating film 18 once formed, it is easy to reduce the thickness to less than twice the thickness of the photoelectric conversion layer 4, more preferably less than the same size. Can be realized. Thereby, even when there is a portion having a reverse taper when the connection groove 22 is formed, the elements can be electrically connected well. Leakage current through the side surface in the connection groove 22 can be prevented. In addition, as the method of forming the inclined portion 8, by forming the insulating film 18 isotropically and then etching it anisotropically, the manufacturing thereof becomes easy. At this time, if the inclined portion 8 is formed using a plurality of layers having different etching characteristics, and the lower layer is used as an etching stopper, the processing is further facilitated.

  The present invention realizes a laminated thin film solar cell having excellent performance and facilitates its manufacture.

DESCRIPTION OF SYMBOLS 1 Transparent insulating substrate, 2 Transparent electrode, 4 Photoelectric conversion layer, 6 Back surface electrode, 8 Inclined part, 11 Thin film solar cell element, 18 Insulating film, 21 Transparent electrode separation groove, 22 Connection groove | channel, 23 Back surface electrode separation groove, 25 Island-shaped part, 28 2nd insulating film, 41 1st photoelectric converting layer, 42 2nd photoelectric converting layer, 43 intermediate | middle layer, 100 thin film solar cell.

Claims (5)

A thin-film solar cell manufacturing method in which a plurality of thin-film solar cell elements are arranged on a transparent insulating substrate with a connection groove interposed therebetween, and adjacent thin-film solar cell elements are connected in series in the connection groove. ,
A lamination step of laminating a transparent electrode having a transparent electrode separation groove on the transparent insulating substrate, and a photoelectric conversion layer on the transparent electrode;
A connecting groove forming step of forming a connecting groove so as to expose the connecting portion of the transparent electrode at the bottom by removing the photoelectric conversion layer between the adjacent thin film solar cell elements;
An insulating film forming step of forming an insulating film on the back surface side of the photoelectric conversion layer and in the connection groove;
The insulating film on the back surface side of the photoelectric conversion layer and the connecting portion of the transparent electrode at the bottom in the connecting groove is removed, and an inclined portion made of the insulating film is formed on the side surface in the connecting groove. Forming, and
Forming a continuous conductive film on the back surface side of the photoelectric conversion layer, on the inclined surface of the inclined portion, and on the connecting portion of the transparent electrode;
Separating the conductive film between the thin-film solar cell elements;
The manufacturing method of the thin film solar cell which has this. It is a manufacturing method of the thin film solar cell of Claim 1, Comprising: The manufacturing method of the thin film solar cell which forms the said inclination part by anisotropically etching the said insulating film in the process of forming the said inclination part. It is a manufacturing method of the thin film solar cell according to claim 1, wherein in the insulating film forming step, a film made of a plurality of different materials is laminated to produce the insulating film,
A method of manufacturing a thin film solar cell, wherein in the step of forming the inclined portion, films made of different materials are etched using different etching methods. A thin film solar cell in which a plurality of thin film solar cell elements are arranged on a transparent insulating substrate with a connection groove interposed therebetween, and the thin film solar cell elements are connected in series in the connection groove, and the connection groove The inner side surface has an inclined portion made of an insulating material, and the conductive film formed on the inclined surface of the inclined portion causes the back surface side of one adjacent thin film solar cell element and the surface of the other thin film solar cell element to Thin-film solar cell in which the side is electrically connected in series. 5. The thin film solar cell according to claim 4, wherein a thickness from a side surface in the connection groove of the inclined portion is 0.1 μm or more and less than a thickness of the photoelectric conversion layer.

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