JP5969870B2 - Photoelectric conversion device and manufacturing method thereof - Google Patents

Description

  The present invention relates to a photoelectric conversion device and a method for manufacturing the same, and more particularly to a photoelectric conversion device having a plurality of cells separated by cell separation grooves and having electrodes of adjacent cells connected to each other. is there.

  A photoelectric conversion device is a device that can directly convert sunlight into electrical energy, and has become widespread worldwide as a clean energy conversion device. The photoelectric conversion devices currently in practical use are roughly classified into a crystalline silicon type, a thin film silicon type, and a compound type.

  An index representing the performance of the photoelectric conversion device is conversion efficiency. This conversion efficiency represents the ratio of light energy poured into the photoelectric conversion device that can be converted into electric energy.

  The crystalline silicon photoelectric conversion device has high conversion efficiency and is currently mainstream. However, there is a problem that the amount of silicon used as a raw material is large and the manufacturing cost is high.

  A thin-film silicon photoelectric conversion device can produce an inexpensive module, but its conversion efficiency is lower than that of a crystal or compound photoelectric conversion device, and is sufficient in a limited area such as home use. I can't get power.

  In recent years, a thin film silicon type photoelectric conversion device having a structure in which a plurality of photoelectric conversion layers, each of which absorbs light of different wavelengths, is called a tandem structure or a triple structure has been developed. Although the development of the above-described thin film silicon type photoelectric conversion device has improved the conversion efficiency, it does not replace the crystal type or the compound type in terms of conversion efficiency.

  On the other hand, although the compound type photoelectric conversion device has not yet spread as a general photoelectric conversion device, the theoretical conversion efficiency is superior to the silicon type photoelectric conversion device, With future research and development progress, it can become the mainstream of photoelectric conversion devices in the future.

  The general structure of a CIGS photoelectric conversion device which is a compound photoelectric conversion device is as follows: first substrate / first electrode / CIGS photoelectric conversion layer / buffer layer / semi-insulating layer / second electrode / second substrate in this order. It has a laminated structure.

  In a thin film photoelectric conversion device such as a CIGS photoelectric conversion device, an output as a photoelectric conversion device can be increased by separating a plurality of cells in one photoelectric conversion device and connecting adjacent cells in series. .

  In order to realize the above series connection, it is necessary to form the first electrode separation groove, the photoelectric conversion layer separation groove, and the cell separation groove. In the CIGS photoelectric conversion device, each of the separation grooves is normally formed by a laser scribing method for forming the first electrode separation groove, and by a mechanical scribing method for forming the CIGS photoelectric conversion layer separation cell and the cell separation groove. Is called.

  However, in the mechanical scribing method, consumable members such as metal needles must be periodically replaced, and if the separation groove is not processed normally due to wear of the metal needles or the like, it remains between the cells. Leakage occurs due to the influence of the conductive material, leading to a decrease in conversion efficiency and yield.

  The above problem can be improved by using a laser scribing method in forming all the separation grooves of the CIGS photoelectric conversion device.

  In addition, since the size that can be produced by the photoelectric conversion device is limited, when using it in a large area, it is used as a large area photoelectric conversion device module by arranging multiple photoelectric conversion devices in series and connecting them in parallel Often done.

  However, when a plurality of photoelectric conversion devices having a metal substrate are arranged in series and connected in parallel, electrical wiring is provided between electrodes by soldering between adjacent photoelectric conversion devices, but exists between the photoelectric conversion devices. When solder or the like flows into a slight gap, a leak occurs between the electrode and the metal substrate, leading to a decrease in conversion efficiency and yield as a photoelectric conversion device module.

  In the photoelectric conversion device disclosed in Patent Document 1, leakage between the electrode and the metal substrate is prevented by using, as an oxide layer, an end surface of the metal substrate with which a wiring such as solder is in contact with the above problem. Specifically, in a solar cell module in which a plurality of solar cells formed on a metal substrate are arranged and electrical wiring is formed on adjacent solar cells, among the end surfaces of the metal substrate immediately below the wiring, An oxide layer is formed on at least one side. When removing the edge of the solar cell formed on the metal substrate, the oxide layer performs laser cutting or plasma cutting while supplying an oxidizing gas to the metal substrate, or supplies an oxidizing liquid to the metal substrate. However, it is formed by dicing.

JP 2007-305877 A (published November 22, 2007)

  As described above, in the CIGS photoelectric conversion device, it is desirable to use a laser scribing method in forming all the separation grooves.

  However, when forming the cell separation groove by a laser scribing method, the inventors have deposited a film containing metal Cu having good conductivity on the side wall portion of the cell separation groove due to heat generated by laser light irradiation. It has been found that the occurrence of leakage between the first electrode and the second electrode of the matching cell causes a problem that the conversion efficiency and the yield decrease.

  The invention according to Patent Document 1 can prevent a leak that occurs in the process of connecting a plurality of photoelectric conversion devices, but prevents a leak that occurs in the process of separating one photoelectric conversion device into a plurality of cells. It is not possible.

  The present invention has been made in view of the above-described problems, and the object thereof is to prevent a current leakage between the first electrode and the second electrode, thereby suppressing a decrease in conversion efficiency and a decrease in yield. It is in providing a photoelectric conversion apparatus and its manufacturing method.

  In order to solve the above problems, a photoelectric conversion device according to the present invention includes at least a first electrode, a photoelectric conversion layer, a second electrode, and a second substrate stacked in this order on a first substrate. The photoelectric conversion layer includes copper, and includes a cell separation groove that cuts through each layer of the photoelectric conversion layer and the second electrode, and the photoelectric conversion layer includes the cell separation groove. A copper oxide film is formed in a portion adjacent to the cell separation groove.

  According to said structure, the side part of the said photoelectric converting layer adjacent to the said cell separation groove is a highly insulating copper oxide film. Therefore, current can be prevented from leaking between the first electrode and the second electrode. Therefore, reduction in conversion efficiency and yield as a photoelectric conversion device can be suppressed.

Furthermore, the photoelectric conversion device according to the present invention is characterized in that at least a part of the copper oxide film is Cu ₂ O.

According to the above configuration, further, the copper oxide film exists containing Cu 2 _O to the side portion of the photoelectric conversion layer has excellent insulating properties. Therefore, current leakage between the first electrode and the second electrode can be prevented more reliably. Therefore, reduction in conversion efficiency and yield can be suppressed.

Furthermore, the photoelectric conversion device according to the present invention is characterized in that the copper oxide film has a higher ratio of Cu ₂ O to CuO as it is closer to the cell separation groove.

According to the above configuration, the copper oxide film containing a large amount of Cu ₂ O excellent in insulation is formed in a region close to the cell separation groove in the film thickness direction on the side wall of the cell separation groove where leakage is likely to occur. Is done. Therefore, it is possible to suppress the leak more reliably. Therefore, reduction in conversion efficiency and yield can be suppressed. Further, in the region close to the photoelectric conversion layer in the film thickness direction, a large amount of CuO having a lower resistivity than Cu ₂ O is present, so that the photoelectric conversion layer is compared with the case where the copper oxide film is entirely composed of Cu ₂ O. Since the resistance in the vicinity of can be reduced, it is possible to suppress a decrease in conversion efficiency.

  Furthermore, the photoelectric conversion device according to the present invention is characterized in that a film thickness from the cell separation groove of the copper oxide film to the photoelectric conversion layer is 100 nm or more and 1000 nm or less.

  According to the above configuration, the copper oxide film further has a film thickness of 100 nm or more, thereby sufficiently preventing leakage between the first electrode and the second electrode that causes a decrease in conversion efficiency. be able to. Moreover, since photoelectric conversion is not performed in the region where the copper oxide film is formed, if the film thickness is larger than necessary, the output is reduced. In this respect, in the case of 1000 nm or less, the output decrease is negligible, and a photoelectric conversion device that does not affect the performance can be provided.

  Furthermore, the photoelectric conversion device according to the present invention includes a first electrode separation groove that separates the first electrode, and a photoelectric conversion that vertically cuts the photoelectric conversion layer between the cell separation groove and the first electrode separation groove. A layer separation groove, and a conductor provided in the photoelectric conversion layer separation groove electrically connects one of the second electrode and the other first electrode of two adjacent cells. It is characterized by being.

  According to the above configuration, one photoelectric conversion device is further divided into a plurality of cells, and the second electrode of one divided cell is electrically connected to the first electrode of the cell existing next thereto. And become conductive. Each cell is connected in series with an adjacent cell. Therefore, a high-output photoelectric conversion device can be provided.

  In the method for manufacturing a photoelectric conversion device according to the present invention, at least a first electrode, a photoelectric conversion layer, a second electrode, and a second substrate are stacked in this order on a first substrate. A method of manufacturing an apparatus, comprising: laminating a first electrode, a photoelectric conversion layer, and a second electrode in this order on a first substrate; then, longitudinally cutting each layer of the photoelectric conversion layer and the second electrode. A step of forming a cell separation groove, and a step of forming the cell separation groove, wherein a copper oxide film is formed in a portion adjacent to the cell separation groove in the photoelectric conversion layer.

  According to the manufacturing method of the photoelectric conversion device, in the manufacturing process of the photoelectric conversion device having the photoelectric conversion layer, a highly insulating copper oxide film is formed on the side surface portion of the photoelectric conversion layer adjacent to the cell separation groove. can do. Therefore, current can be prevented from leaking between the first electrode and the second electrode. Therefore, reduction in conversion efficiency and yield as a photoelectric conversion device can be suppressed.

  Furthermore, in the method for manufacturing a photoelectric conversion device according to the present invention, in the step of forming the cell separation groove, the cell separation groove is formed in the atmosphere or in a low oxygen atmosphere in which the oxygen partial pressure is lower than that in the atmosphere. It is characterized by heating the part.

According to the method for manufacturing the photoelectric conversion device, the copper oxide film is further formed by heating in the air or in a low oxygen atmosphere, so that the copper oxide film contains Cu ₂ O having excellent insulating properties. It becomes. Therefore, leakage can be prevented more reliably.

  Furthermore, the method for manufacturing a photoelectric conversion device according to the present invention is characterized in that, in the step of forming the cell separation groove, a portion where the cell separation groove is formed is heated by irradiating a laser beam.

  According to the method for manufacturing a photoelectric conversion device, when laser light is further irradiated onto a solid, if the irradiation intensity of the laser light is equal to or higher than a threshold value, the solid surface is converted into electron, heat, photochemical or mechanical energy, and as a result A physical phenomenon called laser ablation occurs in which a solid surface is etched because neutral atoms, molecules, ions, clusters, electrons, or photons are emitted. By utilizing this phenomenon and irradiating a predetermined portion of the film formation layer with laser light, the layer in the irradiated region can be removed. At that time, since high heat is generated in the irradiation region, the copper oxide film can be formed on the side surface of the photoelectric conversion layer using this heat. Note that when the entire substrate is heated to form the copper oxide film, the region other than the region where the copper oxide film is formed is exposed to a high temperature, which causes deterioration in characteristics as a photoelectric conversion device. However, if heating is performed by laser light irradiation, it occurs in a very small region, so there is no effect on the substrate and the laminated film, and the characteristics are not deteriorated. As a result, current leakage between the first electrode and the second electrode can be prevented, and a photoelectric conversion device in which a decrease in conversion efficiency and yield is suppressed can be manufactured.

Furthermore, the method for manufacturing a photoelectric conversion device according to the present invention is characterized in that the laser beam has a power density of 1 to 4 MW / cm ² .

According to the method for manufacturing the photoelectric conversion device, further, the power density of the laser beam is set to 1 to 4 MW / cm ² , thereby utilizing the heat generated by the laser beam irradiation to form a copper oxide film having a thickness of 100 to 1000 nm. In addition to being formed, a copper oxide film containing Cu ₂ O having excellent insulating properties can be formed when the vicinity of the irradiated region reaches a high temperature. Therefore, since leakage between the first electrode and the second electrode can be suppressed, a photoelectric conversion device in which a decrease in conversion efficiency and yield is suppressed can be manufactured.

  Furthermore, the manufacturing method of the photoelectric conversion device according to the present invention is characterized in that the laser beam has an irradiation time of 10 to 100 nsec.

According to the method for manufacturing the photoelectric conversion device, when the irradiation time is set to 10 to 100 nsec and the laser light is irradiated, a film containing more Cu ₂ O having higher insulation than CuO is formed in the vicinity of the irradiation region. The necessary and sufficient instantaneous heating and cooling occurs. Therefore, a photoelectric conversion device in which a decrease in conversion efficiency and yield is suppressed can be manufactured.

  Furthermore, the method for manufacturing a photoelectric conversion device according to the present invention is characterized in that the temperature of the laser beam in the irradiation region of the photoelectric conversion layer is 1500 ° C. or more and 5000 ° C. or less.

  According to the method for manufacturing a photoelectric conversion device, it is possible to form a copper oxide film having an electrical resistivity that can prevent leakage.

  Furthermore, the method for manufacturing a photoelectric conversion device according to the present invention is characterized in that the temperature in the laser light irradiation region is about 3000 ° C.

  According to the method for manufacturing the photoelectric conversion device, it is possible to form a copper oxide film having the best electrical resistivity.

  Furthermore, in the method for manufacturing a photoelectric conversion device according to the present invention, the photoelectric conversion device further includes a buffer layer and a semi-insulating layer between the photoelectric conversion layer and the second electrode. The conversion layer is a CIGS photoelectric conversion layer, and the first electrode, the photoelectric conversion layer, the buffer layer, the semi-insulating layer, and the second electrode are stacked in this order on the first substrate. Thereafter, in the step of forming the cell separation groove, the cell separation groove is formed so as to cut through the photoelectric conversion layer, the semi-insulating layer, the buffer layer, and the second electrode. The wavelength of the laser beam for forming the cell separation groove is 600 nm or more and 750 nm or less.

  According to the method for manufacturing a photoelectric conversion device, when laser light with a wavelength of 600 nm or more and 750 nm or less is further irradiated, the laser light is not absorbed by the second electrode, the semi-insulating layer, and the buffer layer, but the CIGS photoelectric conversion layer is used. Absorption occurs due to absorption. As a result, when the CIGS photoelectric conversion layer is ejected from the substrate surface, these upper layers can be ejected from the substrate surface at the same time, so that a normal cell separation groove can be formed.

  Furthermore, the method for manufacturing a photoelectric conversion device according to the present invention includes a step of forming a first electrode separation groove for separating the first electrode, and the photoelectric conversion device between the cell separation groove and the first electrode separation groove. The method further includes the step of forming a photoelectric conversion layer separation groove that vertically cuts the conversion layer by laser light irradiation.

  According to the method for manufacturing a photoelectric conversion device, when laser light is further irradiated onto a solid, if the irradiation intensity of the laser light is equal to or higher than a threshold value, the solid surface is converted into electron, heat, photochemical or mechanical energy, and as a result A physical phenomenon called laser ablation occurs in which a solid surface is etched because neutral atoms, molecules, ions, clusters, electrons, or photons are emitted. By utilizing this phenomenon and irradiating a predetermined portion of the film formation layer with laser light, the layer in the irradiated region can be removed.

  Furthermore, in the method for producing a photoelectric conversion device according to the present invention, the photoelectric conversion layer is a CIGS photoelectric conversion layer, and the wavelength of the laser beam for forming the photoelectric conversion layer separation groove is 600 nm or more and 750 nm or less. It is characterized by being.

Here, CIGS is obtained by substituting Ga for a part of In in CuInSe ₂ (CIS) made of Cu, In, and Se. When Ga is substituted for all In sites, CuGaSe ₂ ( CGS). CIS has a high absorptance with respect to light having a wavelength of 1000 nm or less, but rapidly decreases from around 1100 nm, and almost no absorption occurs at around 1150 nm. Similarly, CGS has a high absorption rate up to around 750 nm, but rapidly decreases from around 800 nm and almost no absorption near 850 nm. Although the absorption edge wavelength of CIGS varies depending on the difference in the composition of In and Ga, it exists in the respective absorption edge wavelength regions of CIS and CGS. Therefore, the absorption edge wavelength of CIGS falls within the range of 850 nm to 1150 nm.

  Therefore, according to the manufacturing method of the photoelectric conversion device, by using a laser having a wavelength of 750 nm or less, the CIGS photoelectric conversion layer having an arbitrary In and Ga composition can be ablated and separated. Grooves can be formed. Further, since the first electrode has a relatively small absorption with respect to light having a wavelength of 600 nm or more, only the CIGS photoelectric conversion layer can be selectively removed without affecting the first electrode, and the normal photoelectric conversion can be performed. A layer separation groove can be formed.

  The photoelectric conversion device according to the present invention includes a cell separation groove that vertically cuts each layer of the photoelectric conversion layer and the second electrode, the photoelectric conversion layer contains copper, and the cell separation in the photoelectric conversion layer is performed. In this configuration, a copper oxide film is formed at a site adjacent to the groove.

  In the method for manufacturing a photoelectric conversion device according to the present invention, the first electrode, the photoelectric conversion layer, and the second electrode are stacked in this order on the first substrate, and then the photoelectric conversion layer and the second electrode are stacked. Including a step of forming a cell separation groove that vertically cuts each layer with the electrode, and a step of forming a copper oxide film in a portion adjacent to the cell separation groove in the photoelectric conversion layer in the step of forming the cell separation groove. The method includes a step of forming a copper oxide film in a portion adjacent to the cell separation groove in the photoelectric conversion layer.

  Therefore, since a highly insulating copper oxide film is formed on the side surface portion of the photoelectric conversion layer adjacent to the cell separation groove, current leakage between the first electrode and the second electrode is prevented. Can be prevented. Therefore, there is an effect that it is possible to suppress a decrease in conversion efficiency and yield.

It is a figure which shows the structure of the CIGS photoelectric conversion apparatus in embodiment of this invention, (a) has shown the top view of the CIGS photoelectric conversion apparatus, (b) has shown CIGS shown by Fig.1 (a) The arrow sectional drawing in the AA 'line of a photoelectric conversion apparatus is shown, (c) has shown the enlarged view of the principal part S in (b). It is a perspective view which shows the structure of the board | substrate of the CIGS photoelectric conversion apparatus in embodiment of this invention. Each temperature, _Cu in an oxygen partial pressure, Cu 2 O, is a state diagram of CuO. It is the figure which showed the relationship between the distance of a perpendicular direction from the CIGS photoelectric converting layer side surface, and ultimate temperature. It is the figure which showed the relationship between the distance of a perpendicular direction from the CIGS photoelectric converting layer side surface, and relative oxygen concentration. It is explanatory drawing of the manufacturing process which concerns on embodiment of this invention, Comprising: (a) is sectional drawing which shows the formation process of a 1st electrode, (b) is sectional drawing which shows the formation process of a 1st electrode separation groove | channel. . It is an external view of the laser scribing apparatus used for formation of each separation groove. It is explanatory drawing of the manufacturing process which concerns on embodiment of this invention, Comprising: (a) is sectional drawing which shows the film-forming process of a CIGS photoelectric converting layer, (b) is sectional drawing which shows the film-forming process of a buffer layer . It is explanatory drawing about the process of a three step method. It is explanatory drawing of the manufacturing process which concerns on embodiment of this invention, Comprising: (a) is sectional drawing which shows the film-forming process of a semi-insulating layer, (b) is sectional drawing which shows the formation process of a CIGS photoelectric converting layer isolation | separation groove | channel It is. It is the figure which showed the absorption coefficient with respect to the wavelength of CIS and CGS. It is explanatory drawing of the manufacturing process which concerns on embodiment of this invention, Comprising: (a) is sectional drawing which shows the film-forming process of a 2nd electrode, (b) is sectional drawing which shows the formation process of a cell isolation | separation groove | channel. It is the figure which showed the transmittance | permeability with respect to the wavelength of ZnO. It is explanatory drawing of the manufacturing process which concerns on embodiment of this invention, Comprising: (a) is sectional drawing which shows the structure of a side copper oxide film, (b) is an enlarged view of the principal part S in (a). It is the figure which showed the relationship between a laser power density and a side copper oxide film thickness. It is the figure which showed the relationship between laser beam irradiation time and the ultimate temperature of an irradiation area | region. It is a figure which shows the relationship between the temperature of a laser beam irradiation area | region at the time of irradiating a laser beam with each laser power density, and the electrical resistivity of a side copper oxide film. It is explanatory drawing of the manufacturing process which concerns on embodiment of this invention, Comprising: It is sectional drawing which shows the formation process of a 2nd board | substrate. It is sectional drawing which shows the structure of the other side copper oxide film of this invention.

  An embodiment of the present invention will be described below with reference to FIGS.

(Construction)
The structure of the CIGS photoelectric conversion apparatus (photoelectric conversion apparatus) 10 of this Embodiment is demonstrated based on FIGS.

  FIG. 1 is a diagram illustrating a configuration of a CIGS photoelectric conversion device, and FIG. 2 is a perspective view illustrating a configuration of a substrate in the CIGS photoelectric conversion device 10.

  In this embodiment, a CIGS photoelectric conversion layer is used as the photoelectric conversion layer, but a material containing copper such as CZTS (Cu, Zn, Sn, S) may be used as the other photoelectric conversion layer. it can.

  FIG. 1A shows a plan view of the CIGS photoelectric conversion device 10. The CIGS photoelectric conversion device 10 includes a structural unit including a first electrode separation groove 11, a photoelectric conversion layer separation groove 12, and a cell separation groove 13 in the vicinity of a cell boundary. The structural unit is a configuration in which the photoelectric conversion layer separation grooves 12 are arranged in parallel in the order in which the photoelectric conversion layer separation grooves 12 are sandwiched between the first electrode separation grooves 11 and the cell separation grooves 13. Further, the CIGS photoelectric conversion device 10 has a repeating structure of the above structural units.

  FIG. 1B shows a cross-sectional view taken along the line AA ′ of the CIGS photoelectric conversion apparatus 10 shown in FIG. The structure of the CIGS photoelectric conversion device 10 includes a first electrode 22, a CIGS photoelectric conversion layer (photoelectric conversion layer) 23, a buffer layer 24, a semi-insulating layer 25, a second electrode 26, a sealing material 27 on the first substrate 21. The second substrate 28 is laminated in this order. Further, the first electrode separation groove 11 divides the first electrode 22, and the photoelectric conversion layer separation groove 12 vertically cuts the CIGS photoelectric conversion layer 23, the buffer layer 24, and the semi-insulating layer 25. The cell separation groove 13 is divided by cutting the CIGS photoelectric conversion layer 23, the buffer layer 24, the semi-insulating layer 25, and the second electrode 26 vertically.

In addition, side surface copper oxide films (copper oxide films) 14 containing CuO or Cu ₂ O are provided on the side surface portions of the CIGS photoelectric conversion layers 23 on both sides adjacent to the cell separation grooves 13.

  As described above, in the CIGS photoelectric conversion device 10 of the present embodiment, one CIGS photoelectric conversion device 10 is divided into a plurality of cells, and the second electrode 26 of one divided cell and the adjacent one exist. The first electrode 22 of the cell is in contact and is in a conductive state. That is, each cell is connected in series, and the output of the CIGS photoelectric conversion device 10 can be increased by connecting the adjacent cells in series.

  The first substrate 21 is transparent and insulative, and is, for example, a soda lime glass substrate having a vertical width L1 of 1 m, a horizontal width L2 of 2 m, and a thickness L3 of 7 mm. FIG. 2 shows an example of the first substrate 21.

  In addition, the following 2 points | pieces are mentioned as a reason which uses soda-lime glass as the 1st board | substrate 21 in this Embodiment.

  The first point is that the thermal expansion coefficient of soda lime glass and the thermal expansion coefficient of CIGS are approximate, and it becomes possible to suppress defects due to the difference in expansion between the glass and CIGS when the substrate is heated. Because.

  Second, in the CIGS photoelectric conversion device 10, the conversion efficiency in the CIGS photoelectric conversion device 10 can be improved by the Na effect, which is a phenomenon in which CIGS crystal grains grow largely due to diffusion of Na from soda lime glass. Because it becomes.

  The first substrate 21 is not limited to soda lime glass as long as necessary conditions for the substrate are satisfied. In the present embodiment, the first substrate 21 is not necessarily transparent because light is incident from the second substrate 28 side.

The first electrode 22 is made of Mo having a thickness of 200 nm formed by sputtering. As a material of the first electrode 22, an electrical resistivity is desirably 10 ⁻³ [Ω · cm] or less. When light is incident from the second electrode 26 side and is not completely absorbed by the CIGS photoelectric conversion layer 23, the light that has not been absorbed is reflected by the first electrode 22, and again the CIGS photoelectric conversion layer By making it absorb in 23, light can be used efficiently. Therefore, it is desirable that the first electrode 22 is made of a material having a high reflectance with respect to the wavelength region used by the CIGS photoelectric conversion layer 23.

  Moreover, when Mo is used as the material of the first electrode 22, it is known that the Na effect is promoted, which contributes to improvement in conversion efficiency. Examples of other materials for the first electrode 22 include Ag and Al.

  Next, the CIGS photoelectric conversion layer 23 is made of CIGS formed with a film thickness of 2 μm by a three-step method.

CIGS is obtained by substituting Ga for a part of In in CuInSe ₂ (CIS) composed of Cu, In, and Se. When Ga is substituted for all In sites, CuGaSe ₂ (CGS) Become. The CIGS in the present invention includes CIS having a Ga composition of 0 and CGS having an In composition of 0.

  CIS has a high absorptance with respect to light having a wavelength of 1000 nm or less, but rapidly decreases from around 1100 nm, and almost no absorption occurs at around 1150 nm. Similarly, CGS has a high absorption rate up to around 750 nm, but rapidly decreases from around 800 nm and almost no absorption near 850 nm. Although the absorption edge wavelength of CIGS varies depending on the difference in composition between In and Ga, it exists in the respective absorption edge wavelength regions of CIS and CGS, and therefore falls within the range of 850 nm to 1150 nm.

  Here, the theoretical band gap of the photoelectric conversion layer where the conversion efficiency of the photoelectric conversion device is the highest is 1.4 eV, and the absorption edge wavelength at that time is 885 nm.

  Therefore, the conversion efficiency can be improved by changing the In and Ga compositions of the CIGS photoelectric conversion layer to bring the absorption edge wavelength closer to 885 nm.

  Next, the buffer layer 24 is made of ZnS formed with a film thickness of 80 nm by chemical bath deposition (CBD method). Since the lattice constant of CIS and CIGS approximates, the generation of defects can be suppressed, and the diffusion of Zn into the CIGS photoelectric conversion layer 23 makes the surface of the CIGS photoelectric conversion layer 23 an n-type layer. It is also considered that conversion efficiency is improved by forming a pn junction inside.

  As a material for the buffer layer 24, CdS has been generally used. However, since Cd is a harmful substance, a study on a material that replaces CdS and a structure without the buffer layer 24 are currently available. Consideration is ongoing.

  Next, the semi-insulating layer 25 is made of ZnO formed to a thickness of 100 nm by sputtering. The semi-insulating layer 25 is an i-type layer, and forms a pin junction between the p-type CIGS photoelectric conversion layer 23 and the n-type second electrode 26.

  Next, the second electrode 26 is made of ZnO (ZnO: Al) doped with Al and formed to a thickness of 200 nm by sputtering.

  In the present embodiment, since the light is incident from the second substrate 28 side, the second electrode 26 needs to be transparent. Therefore, a transparent conductive film generally called a TCO (Transparent Conductive Oxide) film is used for the second electrode 26. In addition to the above ZnO: Al, the TCO film includes tin oxide, tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), or the like. On the other hand, when the light is incident from the first substrate 21 side, the second electrode 26 is not necessarily transparent.

  Here, a structure for functioning as a photoelectric conversion device is realized by stacking up to the second electrode 26. When actually used as a module, the structure is provided on the second electrode 26. Substrate 28 must be formed.

  In the present embodiment, the second substrate 28 is made of 700 μm thick soda lime glass. In general, in the CIGS photoelectric conversion device, since light enters from the second substrate 28 side, the second substrate 28 must be transparent. For this reason, it is desirable to use a glass substrate such as soda lime glass for the second substrate, but the substrate is not limited to this as long as the conditions as a substrate are satisfied. Further, when the photoelectric conversion device is configured such that light is incident from the first substrate 21 side, the second electrode 26 is not necessarily transparent.

  The space between the second electrode 26 and the second substrate 28 is filled with a sealing material 27. When the second substrate 28 is formed, the sealing material 27 has a gap at the interface between the second electrode 26 and the second substrate 28, and the deterioration of the sealing material 27 is promoted by exposing the second electrode 26 to the atmosphere. This is to prevent the

Next, the side copper oxide film 14 is made of a copper oxide film made of CuO or Cu ₂ O.

  In the prior art, in the step of forming the cell separation groove 13 that divides the module of the CIGS photoelectric conversion device 10 by laser light irradiation into a plurality of cells, the temperature of the laser light irradiation region includes metal Cu in the formed film. Thus, a film containing metal Cu was formed on the side surface of the CIGS photoelectric conversion layer 23 adjacent to the cell separation groove 13. Further, due to the formation of the film containing the metal Cu, the first electrode 22 and the second electrode 26 of the adjacent cells are in a conductive state, thereby causing a leak and causing a decrease in conversion efficiency and yield. It was happening.

Therefore, in the CIGS photoelectric conversion device 10 of the present embodiment, the side copper oxide film 14 made of CuO or Cu ₂ O is formed on the side surface portion of the CIGS photoelectric conversion layer 23 adjacent to the cell isolation groove 13 in order to prevent the leakage. It has. Cu ₂ O is generally called cuprous oxide, but in the present invention, cuprous oxide is also included in the copper oxide.

The electrical resistivity of copper oxide is 16.8 × 10 ⁻⁹ Ω · m for Cu, whereas CuO is 1 to 10 Ω · m and Cu ₂ O is 10 ⁶ to 10 ⁷ Ω · m. It is an excellent material. Therefore, in this Embodiment, the film | membrane of the side part of the CIGS photoelectric converting layer 23 formed becomes insulating by controlling the heat | fever generate | occur | produced at the time of the cell separation groove | channel 13 division which divides a module into a some cell. The side copper oxide film 14 is excellent. As a result, the insulation between the first electrode 22 and the second electrode 26 can be sufficiently maintained, and current leakage can be suppressed. Therefore, it is possible to provide a CIGS photoelectric conversion device that can suppress a decrease in conversion efficiency and yield.

  FIG. 1C is an enlarged view of the region S in FIG. 1B and shows a cross-sectional view of the side copper oxide film 14.

The method for forming the side copper oxide film 14 will be described later in detail. When the side copper oxide film 14 is formed in the air or in a low oxygen atmosphere as in the present embodiment, it is shown in FIG. Thus, the side copper oxide film 14 containing a large amount of Cu ₂ O having excellent insulating properties is formed in a region near the cell isolation trench 13 in the film thickness direction of the side copper oxide film 14. A film containing a large amount of CuO is formed in the region 16 close to the CIGS photoelectric conversion layer 23.

The distribution of Cu ₂ O and CuO in the side copper oxide film 14 will be described in detail with reference to FIGS. FIG. 3 shows the states of Cu, Cu ₂ O, and CuO under various temperatures and oxygen partial pressures. When the Cu film is heated in an atmosphere in which oxygen is present, the state is any one of Cu, Cu ₂ O, and CuO. Since the oxygen partial pressure in the atmosphere is 0.21 atm (160 mmHg), the temperature at the point P at which Cu ₂ O begins to be formed when heated in the atmosphere is about 700 ° C. FIG. 4 shows the relationship between the distance in the vertical direction from the side surface of the CIGS photoelectric conversion layer 23 and the ultimate temperature of the heat generated when the cell separation groove 13 is formed. According to FIG. 4, when heat is generated on the side surface of the CIGS photoelectric conversion layer 23 by laser light irradiation, the temperature reached by the CIGS decreases as it deepens in the vertical direction from the outermost side surface of the CIGS photoelectric conversion layer 23. When the cell separation groove 13 is formed using laser light having a laser power density of 2 MW / cm ² as in the present embodiment, the heat generated on the outermost side of the CIGS photoelectric conversion layer 23 is about 3000 ° C. However, for example, when the depth is about 500 nm deep from the outermost surface in the vertical direction, the ultimate temperature is about 700 ° C. Thus, from the relationship between the depth from the side surface of the CIGS photoelectric conversion layer 23 and the reached temperature, in the side copper oxide film 14, it is close to the cell isolation groove 13 reaching the temperature at which the formed film contains metal Cu ₂ O. Cu ₂ O is formed in the region, and CuO is formed in the region close to the CIGS photoelectric conversion layer 23 that does not reach the temperature at which the formed film contains metal Cu ₂ O.

Therefore, the presence of Cu ₂ O having excellent insulation in the side copper oxide film 14 can surely prevent leakage between the first electrode 22 and the second electrode 26.

  Furthermore, the film thickness of the side copper oxide film 14 of the present embodiment will be described.

  When the side copper oxide film 14 is formed by laser light irradiation as in the present embodiment, the thickness of the side copper oxide film 14 is not less than 100 nm and not more than 1000 nm.

  FIG. 5 shows the relationship between the distance from the cell separation groove 13 in the CIGS photoelectric conversion layer 23 and the relative oxygen concentration. According to FIG. 5, the oxygen concentration in the CIGS photoelectric conversion layer 23 decreases with increasing depth from the outermost side surface of the CIGS photoelectric conversion layer 23 in the vertical direction. For example, when the oxygen concentration on the outermost side of the CIGS photoelectric conversion layer 23 is 1, the relative oxygen concentration is 0.15 in a region perpendicular to the outermost surface in a depth of about 500 nm, and almost in a region with a depth of 1000 nm. 0.

  As shown in FIG. 3, Cu oxidation hardly occurs in a situation where the amount of oxygen present is very small. For example, the side copper oxide film 14 is hardly formed in a region having a depth of 1000 nm in the vertical direction from the outermost side. .

  The film thickness of the side copper oxide film 14 can sufficiently maintain the insulation between the first electrode 22 and the second electrode 26 and suppress leakage. In addition, as the thickness of the side copper oxide film 14 increases, the insulation effect increases, and the effect of suppressing leakage between the first electrode 22 and the second electrode 26 also increases.

  Moreover, the film thickness of the said side copper oxide film 14 is the minimum thickness in which 100 nm or more has an insulating effect. A film thickness of 100 nm or more can sufficiently prevent leakage between the first electrode and the second electrode, which causes a reduction in conversion efficiency.

  Therefore, the thickness of the side copper oxide film 14 is preferably 100 nm or more and 1000 nm or less.

(Production method)
The manufacturing method of the CIGS photoelectric conversion apparatus 10 having the above configuration will be described below with reference to FIGS.

(Production method: first electrode and first electrode separation groove)
FIG. 6 shows a process of forming the first electrode 22 and the first electrode separation groove 11. As shown in FIG. 6A, the first electrode 22 is formed by, for example, placing a first substrate 21 of soda lime glass on an operation stage (not shown), and depositing a Mo film on the surface of the first substrate 21 by sputtering. This is done by forming a film. The thickness L3 of the first substrate 21 is 7 mm, and the film thickness L4 of the Mo film that is the first electrode 22 is 200 nm.

  Next, as shown in FIG. 6B, the first electrode separation groove 11 is formed at the laser light irradiation position R1 of the first electrode 22 by a laser scribing method using a laser light irradiation apparatus.

(Laser beam irradiation for forming first electrode separation groove)
A laser beam irradiation method for forming the first electrode separation groove 11 will be described in detail.

Laser light used for scribing, typically excimer gas laser such as CO _2, although the solid-state laser or a semiconductor laser such as YAG is used, but is not limited thereto. Note that a film removal method performed by irradiating a high-power laser beam uses a physical phenomenon called laser ablation. In general, laser ablation is converted to electron, heat, photochemistry, or mechanical energy on the solid surface when the irradiation intensity of the laser beam exceeds a threshold value. As a result, neutral atoms, molecules, ions, clusters, electrons, and photons are emitted. This is a phenomenon in which the solid surface is etched.

  For scribing the first electrode 22 with laser light, a laser scribing apparatus 40 as shown in FIG. 7 is used. The laser scribing apparatus 40 is provided with an X-axis stage 42 and a Y-axis stage 43 on a base 41, a sample mounting table 44 is provided on the X-axis stage 42, and a laser beam irradiation unit 45 is provided on the Y-axis stage 43. It is attached.

  In order to form the first electrode separation groove 11 by the laser scribing device 40, first, the first substrate 21 on which the first electrode 22 is formed is placed on the X-axis stage 42. In addition, when the first electrode 22 is installed so as to be on the sample mounting table 44 side, dust on the first electrode 22 due to scribing may enter the surface of the first electrode 22 or the first electrode separation groove 11. The possibility of adhering increases, which may cause defects. Therefore, it is desirable that the first substrate 21 be installed so that the first electrode 22 is on the laser light irradiation unit 45 side. However, for example, when a countermeasure is used to create a sufficient space between the sample mounting table 44 and the second electrode 26 using a spacer, the second electrode 26 is installed in the direction in which the first substrate 21 is installed. It may be on the sample mounting table 44 side.

  The X-axis stage 42 can move the sample mounting table 44 in the X-axis direction, and the Y-axis stage 43 can move the laser beam irradiation unit 45 in the Y-axis direction. With the above configuration, since the irradiation position of the laser light can be changed in the XY plane, an arbitrary region can be scribed. Next, the X-axis stage 42 and the Y-axis stage 43 are moved while moving the X-axis stage 42 and the Y-axis stage 43 so that the region scribed by the laser light irradiated from the laser light irradiation unit 45 is in a stripe shape (FIG. 1A). Remove.

  In the present embodiment, the laser scribing apparatus 40 as described above is used. However, the present invention is not limited to this configuration as long as the region irradiated with the laser light can be changed. For example, the same effect can be obtained by placing the first substrate 21 on which the first electrode 22 is formed on a fixed stage and irradiating the fixed laser beam irradiation unit while scanning the laser beam.

  As a laser beam for forming the first electrode separation groove 11, for example, a Nd-YAG laser converted to 532 nm, which is half of the conventional wavelength of 1064 nm, by incorporating a KTP crystal can be used.

  Since the Mo film forming the first electrode 22 has a metallic luster and has a certain degree of reflectivity in all wavelength regions, light absorption is not so much. However, while the absorption rate in the ultraviolet region and the infrared region is 30% or less, the absorption rate is relatively high at 50% or more at a wavelength of 400 to 600 nm. It is desirable to use laser light in the region. Note that the laser beam to be used is not limited to this as long as it has a wavelength within the range of 400 to 600 nm and can be irradiated with high output.

The laser light in this embodiment is a pulse laser, and the pulse laser conditions are set to a pulse frequency of 5 kHz, an irradiation time of 100 nsec, a laser power of 2 MW / cm ² , and a pulse laser light irradiation area of 80 μmφ. Under the above conditions, the laser light irradiation unit 45 attached to the Y-axis stage 43 is irradiated with laser light from the end of the first substrate 21 in the Y direction at a speed of 0.1 m / s in the Y direction. As a result, the first electrode separation groove 11 is formed in the Y direction on the surface of the first electrode 22. Thereafter, the same processing is repeated while moving the X-axis stage 42 in the X direction, and 20 striped first electrode separation grooves 11 are formed at intervals of 10 cm.

  Regarding the moving speed of the laser light irradiation unit 45 during continuous irradiation of the pulse laser, in order to make the scribe region into a groove shape, the operation stage is moved at such a speed that the two irradiation regions of the pulse laser overlap each other. I need to move it. Since the pulse laser used in this embodiment has a frequency of 5 kHz and an irradiation area of 80 μmφ, the condition is satisfied if the operation speed of the operation stage is 0.4 m / s or less. Further, in consideration of the fact that the in-plane intensity of the laser light irradiation is weaker in the peripheral part than in the central part, it is preferably 0.2 m / s or less.

  In addition, since the region removed by laser scribing does not contribute to power generation, the power generation amount decreases as the processing region increases. Therefore, the power generation amount of the cell increases as the laser light irradiation area decreases. However, when scribe processing is performed using a laser beam with an extremely small irradiation area, the width of the processing groove becomes narrow, and even a very small dust existing in the processing groove causes conduction with the adjacent cell. . As a result, the performance of the CIGS photoelectric conversion device 10 may be degraded. For this reason, in the scribing process using laser light with a very small irradiation area, after irradiating one line of laser light in the Y direction, the operating stage is moved in the X direction within a range that overlaps with the irradiation line, and scribe in the Y direction is performed. By irradiating again so as to be parallel to the processing groove, a processing groove having a width in the X direction can be formed.

(Manufacturing method: photoelectric conversion layer and buffer layer)
FIG. 8 shows a process for forming the CIGS photoelectric conversion layer 23 and the buffer layer 24.

  FIG. 8A shows a process for forming the CIGS photoelectric conversion layer 23. CIGS is formed as an upper layer of the first electrode 22 in which the first electrode separation groove 11 is formed by the three-stage method which is one of the evaporation methods shown in FIG. 9, and the CIGS photoelectric conversion layer 23 is formed. To do. The CIGS film thickness L5 is 2 μm.

  FIG. 8B shows a process for forming the buffer layer 24. A buffer layer 24 is formed by depositing ZnS as the upper layer of the CIGS photoelectric conversion layer 23 by chemical bath deposition (CBD method). The film thickness L6 of ZnS is 80 nm.

(Manufacturing method: Semi-insulating layer CIGS photoelectric conversion layer separation groove)
FIG. 10 shows a process of forming the semi-insulating layer 25 and the photoelectric conversion layer separation groove 12.

  FIG. 10A shows a process for forming the semi-insulating layer 25. A ZnO film is formed as an upper layer of the buffer layer 24 by sputtering to form the semi-insulating layer 25. The film thickness L7 of the ZnO film is 100 nm.

  FIG. 10B shows a process of forming the photoelectric conversion layer separation groove 12. After the formation of the semi-insulating layer 25, the photoelectric conversion layer separation groove 12 is formed at the laser light irradiation position R2 of the CIGS photoelectric conversion layer 23, the buffer layer 24, and the semi-insulating layer 25 by a laser scribing method.

(Laser irradiation of CIGS photoelectric conversion layer separation groove formation)
A laser scribing device 40 is used to form the photoelectric conversion layer separation groove 12.

  The first substrate 21 formed up to the semi-insulating layer 25 is set on the sample mounting table 44 so that the laser beam is irradiated from the semi-insulating layer 25 side, and the first electrode 21 is separated from the first electrode separation groove 11 by, for example, 150 μm. A scribing process is performed in the same manner as the formation of the first electrode separation groove 11 so as to be parallel to the first electrode separation groove 11 on one substrate 21.

  The wavelength of the laser beam forming the photoelectric conversion layer separation groove 12 is preferably 600 nm or more and 750 nm or less. In the present embodiment, a Q-switch ruby laser with a wavelength of 694 nm is used for the laser light used for forming the photoelectric conversion layer separation groove 12. Other laser light irradiation conditions are the same as those during the scribing process of the first electrode separation groove 11, and the description thereof is omitted.

  The wavelength of the laser beam for forming the photoelectric conversion layer separation groove 12 will be specifically described.

  FIG. 11 is a graph showing absorption coefficients with respect to wavelengths of CIS and CGS.

According to FIG. 11, the CIS layer has a high absorption coefficient of about 10 ⁵ / cm with respect to light having a wavelength of 1000 nm or less, but it suddenly decreases from around 1100 nm and is almost at around 1150 nm. Absorption is lost. Therefore, when scribing the CIS layer with laser light, it is necessary to use laser light having a wavelength of 1000 nm or less, which has a high absorption rate. Similarly, the CGS layer has a high absorptance of 10 ⁴ to 10 ⁵ / cm up to around 750 nm, but rapidly decreases from around 800 nm and almost no absorption near 850 nm. Therefore, when scribing the CGS layer with laser light, it is necessary to use laser light having a wavelength of 750 nm or less, which has a high absorption rate.

  Here, in the case of the CIGS layer, the absorption edge wavelength varies from 1150 nm to 850 nm depending on the composition ratio of In and Ga. Therefore, for example, when the CIGS photoelectric conversion layer 23 having an increased Ga composition and an absorption edge wavelength of 1000 nm or less is scribed with laser light, for example, a Q-switched YAG laser having a wavelength of about 1064 nm may be used. Can not. Therefore, the wavelength of the laser beam that forms the photoelectric conversion layer separation groove 12 needs to be shorter than the absorption edge wavelength of the CIGS photoelectric conversion layer 23. Moreover, ablation can be caused to the CIGS photoelectric conversion layer 23 having an arbitrary In and Ga composition by using a laser beam having a wavelength of 750 nm or less, which has a high CGS absorption rate.

  On the other hand, when a laser beam having a wavelength of 600 nm or less is used, absorption is increased even with Mo of the first electrode 22 and ablation is likely to occur. For this reason, it is necessary to use laser light having a wavelength of 600 nm or more, which has a relatively low absorption rate of the first electrode.

  Therefore, the CIGS photoelectric conversion layer 23 is selectively ablated by using laser light having a wavelength of 600 nm or more and 750 nm or less.

  In addition, when Mo is used as the first electrode 22 as in the present embodiment, it is necessary to irradiate the laser beam for forming the photoelectric conversion layer separation groove 12 from the semi-insulating layer 25 side. This is because when the laser beam is irradiated from the first substrate 21 side, the reflection at the first electrode 22 is large and the CIGS photoelectric conversion layer 23 cannot absorb the laser beam. However, when a material that transmits light in the wavelength region absorbed by the CIGS photoelectric conversion layer 23 is used as the material of the first electrode 22, it is not always necessary to irradiate laser light from the semi-insulating layer 25 side. Even if it irradiates from the 21st side, since the 1st board | substrate 21 and the 1st electrode 22 can permeate | transmit a laser beam and can make it absorb in the CIGS photoelectric converting layer 23, it causes ablation selectively in the CIGS photoelectric converting layer 23 It becomes possible.

(Manufacturing method: second electrode and cell separation groove)
FIG. 12 shows a process of forming the second electrode 26 and the cell separation groove 13.

  FIG. 12A shows a process for forming the second electrode 26. A second electrode 26 is formed by depositing an Al-added ZnO film (ZnO: Al) as the upper layer of the semi-insulating layer 25 by sputtering. The film thickness L8 of the ZnO: Al film is 200 nm.

  Here, ZnO: Al used as the second electrode 26 will be specifically described.

  FIG. 13 is a diagram showing the transmittance with respect to the wavelength of ZnO.

  According to FIG. 13, ZnO has a high absorptance of 90% or more for wavelengths of 350 nm or less, but rapidly decreases from around 380 nm and decreases to about 10% at 400 nm. Here, Al in ZnO: Al is added as an impurity and does not significantly affect the transmittance of ZnO. Therefore, ZnO: Al has an excellent transmittance in most of the wavelength region of 885 nm or less used by the CIGS photoelectric conversion layer 23 and is therefore suitable as a material for the second electrode 26.

  FIG. 12B shows a process of forming the cell separation groove 13. After the formation of the second electrode 26, the cell isolation groove 13 is formed at the laser light irradiation position R3 of the CIGS photoelectric conversion layer 23, the buffer layer 24, the semi-insulating layer 25, and the second electrode 26.

(Laser beam irradiation for cell separation groove formation)
A laser scribing device 40 is used to form the cell separation groove 13.

  The first substrate 21 formed up to the second electrode 26 is set on the sample mounting table 44 so that laser light is irradiated from the second electrode 26 side. Next, a scribing process is performed by a method similar to the formation of the first electrode separation groove 11 so as to be parallel to the first electrode separation groove 11 on the first substrate 21 at a location separated from the first electrode separation groove 11 by, for example, 200 μm. I do. Here, the cell separation groove 13 is formed in a region opposite to the first electrode separation groove 11 when viewed from the photoelectric conversion layer separation groove 12.

  The kind of laser beam and the laser beam irradiation conditions for forming the cell separation groove 13 are the same as those at the time of scribing the photoelectric conversion layer separation groove 12, unless otherwise specified, and are not described here.

  In forming the cell isolation trench 13, the buffer layer 24, the semi-insulating layer 25, and the second electrode 26 are simultaneously removed in addition to the CIGS photoelectric conversion layer 23.

  The wavelength of the laser beam for forming the cell separation groove 13 will be specifically described.

  The second electrode 26 made of ZnO: Al and the semi-insulating layer 25 made of ZnO have a very low absorptance for wavelengths of 400 nm or more, and the buffer layer 24 made of ZnS also has a low absorptance for light of 350 nm or more. Therefore, for example, when a laser beam having a wavelength of 694 nm is irradiated, the laser beam is hardly absorbed. That is, when laser light having a wavelength of 694 nm is irradiated, ablation does not occur in the second electrode 26, the semi-insulating layer 25, and the buffer layer 24.

  Laser light transmitted through the second electrode 26, the semi-insulating layer 25 and the buffer layer 24 is absorbed by the CIGS photoelectric conversion layer 23, and ablation occurs in the CIGS photoelectric conversion layer 23. As a result, when the CIGS photoelectric conversion layer 23 is emitted from the substrate surface, these upper layers are also emitted from the substrate surface at the same time. Therefore, the CIGS photoelectric conversion layer 23, the buffer layer 24, the semi-insulating layer 25, and the second electrode 26 are removed, and the cell isolation groove 13 can be formed.

  Thus, the wavelength of the laser beam for forming the cell separation groove 13 is preferably 600 nm or more and 750 nm or less, as in the formation of the photoelectric conversion layer separation groove 12.

(Manufacturing method: side copper oxide film)
FIG. 14A shows a process of forming the side copper oxide film 14.

  In the present embodiment, the side copper oxide film 14 is formed on the side surface of the CIGS photoelectric conversion layer 23 with the formation of the cell separation groove 13 in the air or in a low oxygen atmosphere. As a result, the occurrence of leakage between the first electrode 22 and the second electrode 26 can be suppressed. Note that the low oxygen atmosphere means a state where the oxygen partial pressure is lower than that in the atmosphere (0.21 atm). For example, in a sealed space, the air in the space is exhausted to such an extent that the oxygen concentration does not become zero, and thus, A low-oxygen atmosphere can be created by filling the space with a nitrogen atmosphere by filling the gas.

As shown in FIG. 14B, the side copper oxide film 14 containing a large amount of Cu ₂ O excellent in insulation is formed in a region near the cell isolation trench 13 in the film thickness direction of the side copper oxide film 14. A film containing a large amount of CuO is formed in the region 16 close to the CIGS photoelectric conversion layer 23.

  The oxygen concentration for forming the side copper oxide film 14 will be specifically described.

The electrical resistivity of copper oxide is 1 to 10 Ω · m for CuO, whereas Cu ₂ O is particularly high at 10 ⁶ to 10 ⁷ Ω · m, and Cu ₂ O is more excellent in insulation than CuO. Yes. Therefore, when the side copper oxide film 14 contains Cu ₂ O, it becomes possible to prevent leakage between the first electrode 22 and the second electrode 26 more reliably. Therefore, it is desirable that the side copper oxide film 14 contains Cu ₂ O.

As described in the structure of the side copper oxide film 14, FIG. 3 shows the states of Cu, Cu ₂ O, and CuO under various temperatures and oxygen partial pressures.

According to FIG. 3, when the Cu film is heated in an atmosphere in which oxygen is present, the state is any one of Cu, Cu ₂ O, and CuO. Since the oxygen partial pressure in the atmosphere is 0.21 atm (160 mmHg), the temperature at the point P at which Cu ₂ O begins to be formed when heated in the atmosphere is about 700 ° C.

Further, as the oxygen partial pressure is decreased, the temperature at which Cu ₂ O begins to be generated decreases accordingly. For example, when the oxygen partial pressure becomes 1/100 (1.60 mmHg) compared to the atmosphere, Cu ₂ O is reduced. The temperature of the point Q that starts to be generated is about 470 ° C.

Therefore, Cu ₂ O is easily obtained in a state where the oxygen partial pressure is lower than that in the atmosphere. Therefore, when laser light irradiation is performed in the atmosphere or in a low oxygen concentration, it is possible to form the side copper oxide film 14 containing Cu ₂ O having excellent insulating properties.

In addition, even when the oxygen concentration is raised to the atmosphere or higher, Cu ₂ O is generated by heating up to a certain oxygen partial pressure, but there is a great danger due to the presence of high-temperature heat in a high-oxygen atmosphere. It is desirable to carry out in a state where the oxygen concentration is lower than in the atmosphere. Cu metal deposition due to heat generated during the formation of the cell separation groove 13 by laser light can also occur during the formation of the photoelectric conversion layer separation groove 12, but the Cu film formed on the side wall of the photoelectric conversion layer separation groove 12 Is not a cause of leakage between the first electrode 22 and the second electrode 26 of adjacent cells, so that it is not necessary to form a copper oxide film by oxidation. Therefore, the formation of the photoelectric conversion layer separation groove 12 is not necessarily performed in the air or in a low oxygen atmosphere.

  Next, the laser power density for forming the side copper oxide film 14 will be described.

FIG. 15 shows the relationship between the laser power density of the irradiated laser light and the film thickness of the side copper oxide film 14 formed at that time. 15 shows the change in the state of Cu, CuO, and Cu ₂ O due to the change in temperature and oxygen partial pressure shown in FIG. 3, and the change in the temperature reached in the vertical direction from the side surface of the CIGS photoelectric conversion layer 23 shown in FIG. And changes in the relative oxygen concentration in the vertical direction from the side surface of the CIGS photoelectric conversion layer 23 shown in FIG. 5 and changes in the generated heat due to the difference in the irradiated laser power density.

According to FIG 15, in the general range of 1~4MW / cm ² is the laser power density used in the laser scribing, side copper oxide is formed when irradiated between 10nsec the laser power density of 1 MW / cm ² The film 14 has a thickness of about 180 nm. On the other hand, the thickness of the side copper oxide film 14 formed when the laser power density is 4 MW / cm ^{2 and} irradiation is performed for 100 nsec is 920 nm. Further, in the present embodiment, a preferable thickness of the side copper oxide film 14 is 100 nm or more and 1000 nm or less in order to maintain sufficient insulation.

Therefore, in order to obtain the side copper oxide film 14 having a film thickness that sufficiently retains insulation, a laser power density of 1 to 4 MW / cm ² is preferable.

  Next, the time and temperature of laser light irradiation for forming the side copper oxide film 14 will be specifically described.

  FIG. 16 shows the relationship between the laser beam irradiation time when the laser beam having each laser power density is irradiated and the ultimate temperature of the irradiation region. The heat generated by laser light irradiation increases as the laser light irradiation time increases. According to FIG. 16, at each laser power density, when the irradiation time is 10 nsec, the reached temperature is 1500 ° C. or higher, which surely exceeds 1050 to 1280 ° C. which is the melting point of CIGS.

  Therefore, the laser beam irradiation time is preferably 10 nsec or more.

On the other hand, in the prior art, the laser beam irradiation for forming the cell separation grooves 13 was performed in the atmosphere, but this was not a laser beam condition that focused on the temperature reached at the time of laser beam irradiation. For example, when the laser beam irradiation time is extremely long, such as 1 μsec or more, the reached temperature becomes high. According to FIG. 3, the thermodynamic region where Cu ₂ O can stably exist is small and becomes a narrow region surrounded by CuO and Cu, and the generated conditions are limited. Furthermore, even if Cu ₂ O is once generated in a state of being heated to 700 ° C. or higher in the atmosphere, a phenomenon of changing to CuO occurs in the process of being slowly cooled.

However, it has been found that when cooling is performed very instantaneously, the change from Cu ₂ O to CuO is suppressed and Cu ₂ O is easily obtained.

Furthermore, when the amount of heat accumulated by long-time laser light irradiation is large, the temperature drop time is long, and thus a large Cu crystal is easily formed as compared with the case of rapid cooling after short-time irradiation. Thereafter, the surface of the Cu metal crystal is oxidized to change to Cu ₂ O or CuO, but the metal Cu remains inside the crystal, and as a result, a film containing metal Cu is formed.

FIG. 17 shows the temperature of the laser light irradiation region and the electrical resistivity of the side copper oxide film 14 when laser light is irradiated at each laser power density. According to FIG. 17, the side copper oxide film 14 prevents leakage if the temperature of the laser light irradiation region R3 is 1500 ° C. or higher in the power density range (1-4 MW / cm ² ) that is generally implemented. It has an electrical resistivity of 300 Ω · m or more. On the other hand, when the laser power density is 4 MW / cm ² and the laser beam is irradiated, the side copper oxide film 14 can prevent leakage when the temperature of the laser beam irradiation region R3 is 5000 ° C. or less. Is provided. Therefore, the temperature of the laser beam irradiation region R3 is preferably 1500 ° C. or more and 5000 ° C. or less. According to FIG. 16, in laser light irradiation with a laser power density of 4 MW / cm ² , the laser light irradiation time is 100 nsec, and the temperature of the laser light irradiation region reaches 5000 ° C. Therefore, the laser beam irradiation time is preferably 100 nsec or less. Further, according to FIG. 17, when the temperature of the laser light irradiation region R3 is 3000 ° C., the side copper oxide film 14 can obtain the highest resistivity. Therefore, it is more preferable that the temperature of the laser light irradiation region R3 is approximately 3000 ° C.

(Manufacturing method: second substrate)
FIG. 18 shows a process of forming the second substrate 28.

For the second substrate 28, for example, soda lime glass having a thickness L9 of 7 mm is used. The space between the second electrode 26 and the second substrate 28 is filled with a sealing material 27.
With the above manufacturing method, in the CIGS photoelectric conversion device 10, the first electrode separation groove 11, the photoelectric conversion layer separation groove 12, and the cell separation groove 13 for realizing series connection of cells are all formed by a laser scribing method. It became possible. Moreover, when the CIGS photoelectric conversion device 10 was manufactured and the characteristics were evaluated, current leakage between the first electrode 22 and the second electrode 26, which had been a problem until now, was improved, and a decrease in conversion efficiency was recognized. I can't.

  Further, the side copper oxide film 14 a may be formed on a side other than the side wall of the CIGS photoelectric conversion layer 23.

  FIG. 19 shows another step of forming the side copper oxide film 14a. As shown in FIG. 19, the side copper oxide film 14 a is also formed on the side wall of the buffer layer 24 and the side wall of the semi-insulating layer 25. Specifically, the side copper oxide film 14a that has reached the melting point of CIGS due to the heat of laser light irradiation and instantaneously becomes a liquid is not only the CIGS photoelectric conversion layer 23 but also the side wall or semi-insulating layer of the buffer layer 24. It is formed (attached) to 25 side walls. According to said structure, there exists an effect that the current leak between the 1st electrode 22 and the 2nd electrode 26 can be prevented.

  In the photoelectric conversion device of the present invention, it is preferable that the first substrate is made of soda lime glass and the first electrode is made of Mo.

  According to the said structure, when the said 1st board | substrate consists of soda-lime glass, it is called the Na effect that the crystal grain of CIGS grows large when Na which exists in soda-lime glass diffuses in a CIGS photoelectric converting layer. A phenomenon occurs. The Na effect is promoted when the first electrode is made of Mo. As a result, conversion efficiency as a photoelectric conversion device is improved.

  Furthermore, in the photoelectric conversion device of the present invention, the first electrode preferably has an absorptance of 50% or more for light having a wavelength of 400 to 600 nm.

  According to the above configuration, for example, when the absorption rate of the first electrode is 50% or more with respect to laser light having a wavelength of 400 nm or more and 600 nm or less, ablation easily occurs in the irradiated region, and the film is easily removed. be able to.

  Furthermore, in the photoelectric conversion device of the present invention, the absorption edge wavelength of the CIGS photoelectric conversion layer is preferably 850 nm or more and 1150 nm or less.

  According to the above configuration, CIS has a high absorptance with respect to light having a wavelength of 1000 nm or less, but rapidly decreases from around 1100 nm, and almost no absorption occurs at around 1150 nm. Similarly, CGS has a high absorption rate up to around 750 nm, but rapidly decreases from around 800 nm and almost no absorption near 850 nm. Although the absorption edge wavelength of CIGS varies depending on the difference in the composition of In and Ga, it exists in the region of the absorption edge wavelengths of CIS and CGS, and therefore falls within the range of 850 nm to 1150 nm. Therefore, the In and Ga compositions of the CIGS photoelectric conversion layer can be brought close to the absorption edge wavelength (885 nm) at which the conversion efficiency of the photoelectric conversion device is theoretically the highest, so that the conversion efficiency can be improved.

Furthermore, in the method for manufacturing a photoelectric conversion device of the present invention, the laser light is used in at least the formation of the CIGS photoelectric conversion layer separation groove and the cell separation groove among the first electrode separation groove, the CIGS photoelectric conversion layer separation groove, and the cell separation groove. It is preferable to irradiate from the opposite side of the first substrate.
According to the manufacturing method, the CIGS photoelectric conversion layer separation groove and the cell separation groove are formed by irradiating laser light from the side opposite to the first substrate, without affecting the first electrode. The photoelectric conversion layer, the buffer layer, and the semi-insulation can be selectively removed. In the formation of the first electrode separation groove, if the first substrate is transparent, the irradiation of the laser light is the same as that from the first electrode side, even from the first substrate side. An effect can be obtained.

Furthermore, in the manufacturing method of the photoelectric conversion device of the present invention, the substrate moving speed or the laser beam scanning speed when forming the first electrode separation groove, CIGS photoelectric conversion layer separation groove, and cell separation groove is 0.2 m / second. It is preferable that it is s or less.
According to the manufacturing method, when the first electrode separation groove, the CIGS photoelectric conversion layer separation groove, and the cell separation groove are formed by continuous irradiation with pulsed laser light, the moving speed of the substrate or the scanning speed of the laser light is set to 0.2 m. By setting it to / s or less, two continuous pulsed laser light irradiation regions overlap each other, and a reliable separation groove shape can be obtained. Therefore, it is possible to prevent a decrease in conversion efficiency and yield due to defective formation of separation grooves.

  Furthermore, in the method for manufacturing a photoelectric conversion device of the present invention, the wavelength of the laser beam for forming the first electrode separation groove is preferably 400 nm or more and 600 nm or less.

  According to the above manufacturing method, the first electrode has a relatively high absorption rate for light having a wavelength of 400 nm or more and 600 nm or less, and therefore ablation can easily occur by using laser light in this wavelength region. It is possible to form a normal first electrode separation groove.

  Furthermore, in the method for manufacturing a photoelectric conversion device of the present invention, the wavelength of the laser light for forming the CIGS photoelectric conversion layer separation groove is preferably 600 nm or more and 750 nm or less.

CIS has a high absorptance with respect to light having a wavelength of 1000 nm or less, but rapidly decreases from around 1100 nm, and almost no absorption occurs at around 1150 nm. Similarly, CGS has a high absorption rate up to around 750 nm, but rapidly decreases from around 800 nm and almost no absorption near 850 nm. Although the absorption edge wavelength of CIGS varies depending on the difference in the composition of In and Ga, it exists in the respective absorption edge wavelength regions of CIS and CGS.
According to the said manufacturing method, it exists in the range of 850 nm or more and 1150 nm or less. Therefore, by using a laser having a wavelength of 750 nm or less, ablation can be caused to the CIGS photoelectric conversion layer having an arbitrary In and Ga composition, and a separation groove can be formed. In addition, since the first electrode has a relatively small absorption with respect to light having a wavelength of 600 nm or more, only the CIGS photoelectric conversion layer can be selectively removed without affecting the first electrode, and the normal CIGS photoelectric conversion can be performed. It is possible to form the conversion layer separation groove.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and the embodiments can be obtained by appropriately combining the technical means disclosed in the embodiments. The form is also included in the technical scope of the present invention.

  The present invention can be applied to a CIGS photoelectric conversion device in which a first electrode, a CIGS photoelectric conversion layer, a buffer layer, a semi-insulating layer, a second electrode, and a second substrate are stacked in this order on a first substrate. Is possible.

10 CIGS photoelectric conversion device (photoelectric conversion device)
11 First electrode separation groove 12 Photoelectric conversion layer separation groove 13 Cell separation groove 14, 14a Side copper oxide film (copper oxide film)
21 First substrate 22 First electrode 23 CIGS photoelectric conversion layer (photoelectric conversion layer)
24 Buffer layer 25 Semi-insulating layer 26 Second electrode 28 Second substrate R1 to R3 Laser beam irradiation position (laser beam irradiation region)

Claims (15)

A photoelectric conversion device in which at least a first electrode, a photoelectric conversion layer, a second electrode, and a second substrate are stacked in this order on a first substrate,
The photoelectric conversion layer contains copper,
A cell separation groove that vertically cuts each layer of the photoelectric conversion layer and the second electrode;
A copper oxide film is formed in a portion adjacent to the cell separation groove in the photoelectric conversion layer ,
At least a part of the copper oxide film is CuO,
The photoelectric conversion layer is a photoelectric conversion device according to claim CIGS photoelectric conversion layer der Rukoto. The photoelectric conversion device according to claim 1, wherein at least a part of the copper oxide film is Cu ₂ O. 3. The photoelectric conversion device according to claim 2, wherein the copper oxide film has a larger ratio of Cu ₂ O to CuO at a position closer to the cell separation groove. A photoelectric conversion device in which at least a first electrode, a photoelectric conversion layer, a second electrode, and a second substrate are stacked in this order on a first substrate,
The photoelectric conversion layer contains copper,
A cell separation groove that vertically cuts each layer of the photoelectric conversion layer and the second electrode;
A copper oxide film is formed in a portion adjacent to the cell separation groove in the photoelectric conversion layer,
The photoelectric conversion layer is a CIGS photoelectric conversion layer,
The photoelectric conversion device you wherein a film thickness from the cell isolation groove of the copper oxide film to the photoelectric conversion layer is 100nm or more and 1000nm or less. A photoelectric conversion device in which at least a first electrode, a photoelectric conversion layer, a second electrode, and a second substrate are stacked in this order on a first substrate,
The photoelectric conversion layer contains copper,
A cell separation groove that vertically cuts each layer of the photoelectric conversion layer and the second electrode;
A copper oxide film is formed in a portion adjacent to the cell separation groove in the photoelectric conversion layer,
The photoelectric conversion layer is a CIGS photoelectric conversion layer,
A first electrode separation groove for separating the first electrode;
Between the cell separation groove and the first electrode separation groove, a photoelectric conversion layer separation groove that vertically cuts the photoelectric conversion layer is provided,
The conductor provided in the photoelectric conversion layer separating groove, characterized in that the one of the second electrode and the other of the first electrodes of adjacent two cells are electrically connected light Electric conversion device. A method for manufacturing a photoelectric conversion device in which at least a first electrode, a photoelectric conversion layer, a second electrode, and a second substrate are stacked in this order on a first substrate, wherein the photoelectric conversion layer is CIGS A photoelectric conversion layer,
A step of forming a cell separation groove that vertically cuts each layer of the photoelectric conversion layer and the second electrode after laminating the first electrode, the photoelectric conversion layer, and the second electrode in this order on the first substrate. Including
In the step of forming the cell separation groove, a copper oxide film is formed in a portion adjacent to the cell separation groove in the photoelectric conversion layer.   The portion for forming the cell separation groove is heated in the step of forming the cell separation groove in the atmosphere or in a low oxygen atmosphere having an oxygen partial pressure lower than that in the atmosphere. Method for manufacturing a photoelectric conversion device.   The method for manufacturing a photoelectric conversion device according to claim 6 or 7, wherein, in the step of forming the cell separation groove, a portion where the cell separation groove is formed is heated by irradiating a laser beam. The method for manufacturing a photoelectric conversion device according to claim 8, wherein the laser light has a power density of 1 to 4 MW / cm ² .   The method for manufacturing a photoelectric conversion device according to claim 8, wherein the laser beam has an irradiation time of 10 to 100 nsec.   The method for manufacturing a photoelectric conversion device according to claim 8, wherein the laser light has a temperature in an irradiation region of the photoelectric conversion layer of 1500 ° C. or more and 5000 ° C. or less.   12. The method of manufacturing a photoelectric conversion device according to claim 11, wherein the temperature in the laser light irradiation region is about 3000.degree. The photoelectric conversion device further includes a buffer layer and a semi-insulating layer between the photoelectric conversion layer and the second electrode,
The photoelectric conversion layer is a CIGS photoelectric conversion layer,
A step of forming the cell separation groove after laminating the first electrode, the photoelectric conversion layer, the buffer layer, the semi-insulating layer, and the second electrode in this order on the first substrate. The cell separation groove is formed so as to cut through the photoelectric conversion layer, the semi-insulating layer, the buffer layer, and the second electrode.
13. The method of manufacturing a photoelectric conversion device according to claim 8, wherein a wavelength of the laser beam for forming the cell separation groove is 600 nm or more and 750 nm or less. Forming a first electrode separation groove for separating the first electrode;
7. The method further comprising: forming a photoelectric conversion layer separation groove that vertically cuts the photoelectric conversion layer between the cell separation groove and the first electrode separation groove by laser light irradiation. 14. The method for producing a photoelectric conversion device according to any one of items 1 to 13. The photoelectric conversion layer is a CIGS photoelectric conversion layer,
The method of manufacturing a photoelectric conversion device according to claim 14, wherein the wavelength of the laser beam for forming the photoelectric conversion layer separation groove is 600 nm or more and 750 nm or less.

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