WO2017187871A1 - High power generation efficiency compound semiconductor thin-film solar cell, and method for manufacturing same - Google Patents

Abstract

The present invention addresses the problem that a decrease in power generation efficiency which is caused when a CIGS thin-film solar cell is laser scribed occurs as a result of the presence of a defect (recombination center), caused by the influence of heat, which provides a starting point where electrons and holes produced in the light absorption layer of the CIGS thin-film solar cell during light irradiation are recombined and deactivated without contributing to optical current (second problem). The decrease in power generation efficiency is suppressed by removing the defect (recombination center), caused in the vicinity of the light absorption layer surface by the influence of heat during laser scribing, by performing a heat treatment in the vicinity of the absorption layer surface.

Description

High power generation efficiency compound semiconductor thin film solar cell and method of manufacturing the same

The present invention relates to a compound thin film solar cell and a method of manufacturing the same, and more particularly to a compound thin film solar cell manufactured using a laser scribing method.

Conventionally, a basic method of manufacturing a compound thin film solar cell represented by CIGS is as follows. First, a back electrode layer (molybdenum film (Mo)) is formed on a substrate such as soda glass, and then a p-type CIGS is formed thereon. Light absorbing layer (Cu (In _1-x Ga _x ) Se ₂ , mixed crystal prepared by combining copper indium diselenide and copper gallium diselenide at a ratio of (1-x): x), buffer layer (such as CdS) A CIGS compound solar cell is manufactured by laminating a high-resistance buffer layer (such as ZnO) and an n-type oxide transparent conductive film layer (such as ZnO: Al) in this order.

The process of producing a large-area module in a form in which a compound thin film solar cell such as this CIGS compound thin film solar cell is actually used includes a step of forming dividing grooves.
This is because, when the area of the compound thin film solar cell is increased, the series resistance component in the conductive film layer is increased, which causes Joule loss to lower the power generation efficiency of the compound semiconductor solar cell.
In the structure of the module, a plurality of narrow narrow strip-shaped thin film solar battery cells are arranged so that the major axis directions coincide with each other, and a front electrode and a rear electrode made of transparent conductive film layers of adjacent solar cells An extraction module is placed on the top and back electrodes of an integrated module connected in series with a layer electrically connected via division grooves and connected in series, or a solar cell divided into a certain area, and connected by a surface focusing electrode Grid type module.
In any case, by operating as a thin film solar cell module in which solar cells having a small area are connected, an increase in the direct resistance component in the conductive film layer is reduced, and a reduction in the power generation efficiency of the compound thin film solar cell is suppressed.

In the case of the integrated module, the cell division process is a back electrode layer removal scribing process (first scribing process), a high resistance buffer layer / buffer layer / light absorbing layer removal scribing process (second scribing process), and transparent The conductive film layer / high-resistance buffer layer / buffer layer / light absorption layer removing scribing step (third scribing step) is a total of three types of scribing steps.
On the other hand, in the case of the grid type module, it is only one kind of transparent conductive film layer / high resistance buffer layer / buffer layer / light absorption layer removing scribing step (third scribing step).

The mechanical scribing method and the laser scribing method are used in the step of forming the dividing groove. In the mechanical scribing method, it is difficult in principle to reduce the groove width to less than the thickness of the blade because the blade is in contact for scribing.
In addition, when scribing, there is a problem that a crack is generated in the light absorption layer, and peeling of the back electrode and the light absorption layer occurs. Also with regard to the use of a flexible and light-flexible polymer substrate and the like, which will be increasingly in need in the future, there is a problem that the mechanical scribing method in which processing is performed with a blade in contact makes it difficult to apply to flexible substrates.
Therefore, in various solar cells including Si solar cells, the use of a laser scribing method which is most effective in reducing the width of the dividing groove and which can easily cope with an increase in area and flexibility has been promoted (Patent Document 1, Patent Literature 2).

However, when the laser scribing method is applied to a CIGS thin film solar cell, high heat is locally generated, which causes a disadvantage that the power generation efficiency of the CIGS thin film solar cell is deteriorated.
Therefore, when producing an integrated module of a CIGS thin film solar cell, generally, only the first scribing step is performed by a laser method, and the second and third scribing steps for scribing the CIGS light absorption layer Is implemented by mechanical scribing (Patent Document 3).
When mechanical scribing is performed, the layer to be scribed is determined based on the difference in mechanical strength of each layer, so the bottom of the second and third scribed grooves is the molybdenum film of the back electrode layer.
In the CIGS thin film solar cell, the degradation of the power generation efficiency at the time of laser scribing occurs because the CIGS layer, which is the light absorption layer of the CIGS thin film solar cell, is melted by the thermal effect of the laser and changes to a low resistance, the upper electrode A short circuit between the conductive layer and the lower electrode (first problem), a defect serving as a starting point where electrons and holes generated at the time of light irradiation recombine without contributing to the photocurrent (recombination center ) Is known to be caused by the influence of heat (the second problem).

The inventors of the present invention utilized ultra-short pulse laser light as a method for suppressing processing deterioration due to the thermal effect of the laser, and limited the incident energy to considerably suppress the decrease in the power generation efficiency (Patent Document 4).
In addition, as a method of solving the first problem, it has been reported that it is effective to limit the removal layer by the third scribing to the buffer layer and the upper electrode layer (Non-Patent Document 1, Non-patent Document 1) Patent Document 2).

The efficiency recovery of the solar cell by heat treatment is disclosed, for example, in Patent Document 5, and the amorphous silicon thin film solar cell is heat-treated at a temperature of 130 ° C. or more.
However, this heat treatment is an operation for passivating the amorphous silicon semiconductor which causes the short circuit of the upper electrode and the lower electrode.
For the CIGS thin film solar cell, there is a report example by Non-Patent Document 2 about the efficiency recovery by laser scribing only the upper electrode layer and the buffer layer and heat treatment.
The reported conversion efficiency of solar cells is as low as 6.77% after laser drift and 13.18% after recovery by heat treatment, and the factors causing the decrease in efficiency and the reason for heat treatment have not been fully elucidated.

JP-A-59-220979 Japanese Patent Application Laid-Open No. 7-45584 Patent No. 3867230 Unexamined-Japanese-Patent No. 2015-32731 JP 2000-340814 A

By limiting the layer to be removed by the third scribing to two layers of the above-mentioned buffer layer and upper electrode layer, there exists a melted layer in the form of a sidewall of a groove which is a cause of short circuit between upper electrode and lower electrode. Since the power generation layer (light absorption layer) which has not been removed and has not been removed has a high resistance, it does not contribute to a short circuit between the upper electrode and the lower electrode, thereby solving the first problem.
However, the solution to the second problem is not enough.

Under the influence of heat generated at the time of laser scribing, electrons and holes generated at the time of sunlight irradiation are generated near the surface of the light absorption layer adjacent to the buffer layer 5 and the high resistance buffer layer 6 removed by laser scribing The heat generation was applied to the vicinity of the surface of the light absorption layer to remove the defect (recombination center) that becomes the starting point of recombination and deactivation without contributing to the reduction of the power generation efficiency.

Heat recovery at a temperature of 85 ° C. for 15 hours was observed in the vicinity of the surface of the light absorption layer of the sample subjected to the laser scribing.

An increase in the copper concentration of the light absorbing layer is known to indicate the formation of defects leading to a decrease in power generation efficiency.

The depth of the chemical composition of the light absorbing layer near the surface of the light absorbing layer where defects are generated by laser scribing is analyzed by the depth analysis. As a result, in the power generation layer immediately after laser scribing, the deeper region is up to 90 nm deep. It was shown that the concentration of copper increased by about 30%.

The laser beam having a wavelength of 1.04 μm used for the laser scribing passes through the transparent conductive film layer, the high resistance buffer layer, and the buffer layer, and is absorbed by the CIGS light absorbing layer.
The penetration depth of light into the interior of the CIGS layer determined from the light absorption coefficient of the CIGS layer is about 1 μm, but even within this 1 μm layer, the intensity of the light decreases exponentially, so the change in the chemical composition in particular The area in which the high temperature is reached is limited by the outermost surface.
Since the use of an ultrashort pulse laser can almost neglect the influence of heat diffusion, it is considered that the affected depth is a shallow region up to 90 nm.

In the sample heat-treated at 85 ° C. for 5 hours, the above-mentioned increase in copper concentration is not observed, and the composition ratio to the depth is almost constant except for the outermost surface.

The recovery of the efficiency was similarly observed in dry annealing (5% or less of humidity, heat treatment for 15 hours) and vacuum annealing (heat treatment under vacuum conditions of about 10 kPa for 15 hours).
That is, the heat treatment suppresses the increase in the local concentration of copper and reduces the defect density.

There is no decline in conversion efficiency due to heat generation in cell division by laser scribing method, so mechanical scribing that is expected to be more and more in the future is applied to polymer bases with light weight flexibility that is difficult to process and flexible large scale compound thin film solar cells It will be possible to make it.
Furthermore, in this structure, since the adhesion is weak, peeling between the molybdenum film of the back electrode layer and the CIGS light absorption layer is difficult to occur, and the molybdenum film is not exposed, deterioration due to oxidation of molybdenum is caused. There is an advantage that it can prevent.

It is a figure showing the time change of curve factor FF during heat processing for 5 hours, temperature 68 ° C. It is a figure showing the time change of curve factor FF during heat processing for 5 hours, temperature 85 ° C. It is a figure which shows the Auger-electron spectroscopy measurement area | region (part enclosed by the square on the center of a photograph) of the CIGS layer exposed to the bottom part of the dividing groove produced by laser scribing. FIG. 4A is a diagram showing the results of depth direction analysis of the concentration of copper (Cu) by Auger electron spectroscopy of a CIGS layer exposed at the bottom of a dividing groove fabricated by laser scribing, and FIG. As a result of analysis, FIG. 4 (b) is a diagram showing the analysis result of the sample 3 of Example 3 and FIG. 4 (c) is a diagram showing the analysis result of the sample 4 of Example 3. It is a sectional view of a compound thin film solar cell showing the present invention. FIGS. 5 (a) and 5 (b) are structural diagrams of each grid type and integrated type solar battery cell. It is sectional drawing showing the structure of the grid-type module which consists of a compound thin film solar cell of this invention. It is sectional drawing which shows the preparation processes and structure of the integrated module which consists of a compound thin film solar cell of this invention.

Hereinafter, the compound thin film solar cell 1 of the present invention and the structure thereof will be described with reference to the drawings, but the drawings represent one embodiment of the present invention and the present invention is not limited thereto.

The present example is an example of producing a single compound semiconductor solar battery cell which is a unit structure of a grid type module structure shown in FIG. 6, and only one type of laser scribing process (that is, transparent conductive film layer / high resistance buffer) Layer / buffer layer removal laser scribing step only).
Next, although it demonstrates taking one solar cell (FIG. 5 (a)), it manufactures similarly in another solar cell.

As shown in FIG. 5A, first, about 800 nm of Mo was laminated as a metal to be the back electrode layer 3 on the substrate layer 2.
Subsequently, a CIGS light absorption layer is formed to a thickness of about 2 μm as the compound semiconductor light absorption layer 4, and a CdS layer which is a buffer layer 5 and a ZnO layer which is a high resistance buffer layer 6 are formed thereon. It laminated | stacked sequentially by the thickness of nm, and also laminated | stacked the transparent conductive film layer 7 of Al dope ZnO transparent conductive film (ZnO: Al) with the film thickness of about 500 nm.

Thereafter, a laser scribing process is performed in which femtosecond laser light is linearly scanned on the surface of ZnO: Al to divide the laminated portion from the buffer layer 5 to the transparent conductive film layer 7 (ZnO: Al) into a plurality of regions. went.
At this time, an ultrashort pulse laser with a pulse width of 400 fs (femtoseconds) was used as the laser light in order to reduce even a slight thermal damage of the CIGS light absorption layer which is relatively low in melting temperature and weak in heat.

For the laser wavelength, a near infrared wavelength of 1.04 μm was used. This wavelength is a wavelength at which CIGS can absorb light and can efficiently ablate the CIGS light absorption layer.
The pulse laser beam is formed into a rectangular shape with a side of 26 μm, the intensity distribution of which is made uniform by a diffractive optical element, and the irradiation energy density per pulse of the ultrashort pulse laser is about It was reduced to a low value of 0.4 J / cm ² .

In order to suppress heat storage due to multiple pulse continuous irradiation, the “pulse repetition” of the ultrashort pulse laser is 10 kHz, and scanning is performed once at a speed of 0.22 m / s to form the buffer layer 5 to the transparent conductive film layer 7 A dividing groove 8 to be removed was produced.
The scribing was performed for a total length of 32 mm surrounding a power generation area of about 52 mm ² in area.
In the grid type module, each extraction electrode 33 attached to the back electrode layer 12a, 12b, 12c of the solar battery cell having the unit structure described above, and each extraction electrode 34 attached to the transparent conductive film layers 16a, 16b, 16c It can be electrically connected and integrated.

The curve factor FF and the cell conversion efficiency Eff of the solar cell fabricated as above were evaluated.
The curve factor FF is, as is well known, a value obtained by dividing the product of the maximum output voltage and the maximum output current by the product of the open circuit voltage and the short circuit current.
Further, the conversion efficiency Eff is a value obtained by dividing the maximum power that can be taken out by the product of the radiation intensity and the light receiving area.

After the evaluation, the solar battery cell was heated to a temperature of 68 ° C. in the atmosphere, and heat treatment was performed for 5 hours.
The curve factor FF and the cell conversion efficiency Eff were evaluated for the solar cells returned to room temperature after the heat treatment.

As is clear from Table 1, both the fill factor FF and the battery conversion efficiency Eff are increased by the heat treatment.

FIG. 1 shows changes in fill factor FF of cell 1 described in Table 1 measured during heat treatment.
During the heat treatment, the curve factor FF increases as the treatment time passes, and it has been shown that the treatment for 5 hours is approaching saturation.
Since the diode characteristics of the battery change depending on the temperature during heating, the fill factor FF has a small value compared to that measured at room temperature shown in Table 1.

The curvilinear factor FF and the cell conversion efficiency Eff of a manufactured solar cell prepared by laser scribing a solar cell manufactured by the same method as in Example 1 were evaluated.
After the evaluation, the solar battery cell was heated to a temperature of 85 ° C. in the atmosphere, and heat treatment was performed for 5 hours. The curve factor FF and the cell conversion efficiency Eff were evaluated for the solar cells returned to room temperature after the heat treatment.

As is clear from Table 2, both the fill factor FF and the cell conversion efficiency Eff are increased by the heat treatment.
FIG. 2 shows changes in fill factor FF of cell 1 described in Table 1 measured during heat treatment.

It can be seen that the curve factor FF increases as the treatment time passes during the heat treatment, but unlike the heat treatment at 68 ° C., the increase of the curve factor FF reaches saturation by the treatment for about 1.5 hours. It is done.

In order to compare and evaluate the solar cell conversion efficiency of the present laser scribing technology and the conventional mechanical scribing technology, all the conditions up to the film forming step of the transparent conductive film layer are the same as Example 1, and from the light absorbing layer to the transparent conductive film layer In the scribing step of the laminated structure of the above, a sample 1 having a plurality of division grooves formed was manufactured using a conventional mechanical scribing step.

In addition, among the division grooves of Sample 1, one division groove was formed not by mechanical scribing but by laser scribing under the same conditions as in Example 1.

Furthermore, samples 3 and 4 were prepared by subjecting the samples prepared by the same method as sample 2 to heat treatment at 85 ° C. under a reduced pressure of about 10 kPa for 0.5 hours and 3 hours.

The curve factor FF and the cell conversion efficiency Eff were evaluated for samples 1, 2, 3 and 4.

As apparent from Table 3, the conversion efficiency of sample 2 in which the dividing groove is formed by laser scribing is 16.9%, which is 1.0 to 17.9% of that of sample 1 formed by using the mechanical scribing step. Although low, this indicates a reduction in efficiency due to thermal damage during the laser scribing process.

Depending on the conditions under which scribing is performed, a large reduction in efficiency can be observed in many cases (for example, Comparative Example 1), and even when using a femtosecond laser, maintaining the conversion efficiency of the CIGS thin film solar cell is extremely difficult.

The curve factor of sample 3 is increased to 0.754 as compared to sample 2 and is further increased to 0.762 for sample 4.
By increasing the heat treatment time from 0.5 hours of sample 3 to 3 hours of sample 4, the efficiency reduced by the thermal damage in the laser scribing process is recovered, and sample 4 is almost completely eliminated. Is shown.

In order to clarify the influence of the heat damage and the change caused by the subsequent heat treatment, Augers electron spectroscopy is performed on the CIGS layer exposed at the bottom of the dividing groove prepared by laser scribing for the samples 2, 3 and 4. Analysis in the depth direction by.

FIG. 3 shows an electron microscope image (secondary electron image) of the measurement point.
Further, FIG. 4 shows the distribution of Cu concentration in the depth direction obtained by Auger electron spectroscopy. The same figure (a) shows the analysis result of sample 2, the same figure (b) shows the analysis result of sample 3, and the same figure (c) shows the analysis result of sample 4.

FIG. 4 (a) shows the distribution in the depth direction of the Cu concentration observed for sample 2 in which a 1.0% efficiency drop was observed.
A local increase of the Cu concentration is observed in a region of depth 60 to 90 nm (symbol 9 in FIG. 5) indicated by symbol S in the figure.

This result indicates that the Cu concentration is locally high as a result of relatively decreasing In, Ga, and Se having a low melting point compared to Cu due to the thermal effect at the time of laser scribing.
In the CIGS solar cell, it is known that a site where the Cu concentration is high acts as a defect.
The maximum signal strength Is in the region of depth 90 nm or less is 48000, and the average value Id of signal intensities which is substantially constant in the deeper region D (depth 240 to 750 nm (10 in FIG. 5)) It is .34 times.

On the other hand, FIG. 4B shows the result of sample 3 in which the conversion efficiency has recovered to 17.3% by performing the heat treatment for 0.5 hours.

The maximum signal strength Is of the area S is 38,700, and the average value Id of the signal strengths of the area D is reduced to 1.09 times 35500. Furthermore, in the result of sample 4 in which the efficiency decrease due to heat damage shown in FIG. 4C is completely suppressed, Is decreases to 36000, which is 0.98 times Id and 36,600.

From the above results, it was shown that the thermal damage causing the reduction of conversion efficiency occurred at the time of laser scribing is generated due to the local increase of the Cu concentration at a depth of about 90 nm.

By eliminating the locally rising region of the Cu concentration by the heat treatment, the conversion efficiency reduced due to the thermal damage is recovered, and a solar cell exhibiting high power generation efficiency can be manufactured.

More specifically, the average value Id of the signal intensity derived from copper in a sufficiently deep region (for example, a region with a depth of 240 to 750 nm) and the maximum signal intensity Is seen in a region with a depth of 90 nm or less near the surface When (Is ≦ Id) is satisfied, the solar cell exhibits high power generation efficiency without the influence of heat damage.

The present example is an example of manufacturing a compound semiconductor solar cell of the integrated module structure shown in FIG.
FIG. 5 (b) is a structural view showing one of the solar cells.

First, as shown in FIG. 7A, about 800 nm of Mo was laminated on the substrate 11 as a metal to be the back electrode layer 12.
Thereafter, as shown in FIG. 7B, a first laser scribing step of scanning a nanosecond laser beam with a wavelength of 1064 nm in a line on the Mo surface to form a groove with a width of 40 μm and dividing it into a plurality of regions Did.

Subsequently, as shown in FIGS. 7C and 7D, a CIGS light absorption layer is formed to a thickness of about 2 μm as the compound semiconductor light absorption layer 13, and CdS which is the buffer layer 14 is formed thereon. The layer and the ZnO layer which is the high resistance buffer layer 15 were sequentially laminated in a thickness of several tens of nm.

Thereafter, as shown in FIG. 7E, the CIGS light absorbing layer / buffer layer / high resistance buffer layer is formed in a plurality of regions at a position approximately 20 μm laterally away from the groove 17 produced by the first scribing step. A second scribing step was performed to divide.

The second scribing step was performed by mechanical scribing or laser scribing.
The laser scribing step was performed using an ultrashort pulse laser with a pulse width of 400 fs (femtoseconds) having a laser wavelength of 1.04 μm as in Examples 1 to 3, but CIGS light with a thickness of about 2 μm was used. In order to completely remove the absorption layer, the number of pulse irradiations was increased by performing “pulse repetition” of the ultrashort pulse laser at 200 kHz and scanning once at a speed of 0.14 m / s.

As shown in FIG. 7 (f), after the compound semiconductor light absorption layer 13, the buffer layer 14 and the high resistance buffer layer 15 are divided, an Al doped ZnO transparent conductive film (ZnO: Al) is formed as the transparent conductive film layer 16 It laminated | stacked by the film thickness of 700 nm.

Thereafter, as shown in FIG. 7G, in the third scribing step, femtosecond laser light is lined on the surface of the ZnO: Al at a position laterally separated from the groove 18 produced by the second scribing step. Scan and run.

In this scribing step, as in the laser scribing of the grid-type modules of Examples 1 to 3, the dividing grooves 19 for removing the buffer layer to the transparent conductive film were produced.

The curve factor FF and the cell conversion efficiency Eff of the solar cell fabricated as described above were evaluated.
Samples 1 and 2 were mechanical scribing in the second scribing step, and the third scribing step was performed by laser scribing. Samples 3 and 4 were both the second and third scribing steps performed by laser scribing. It is.

After the evaluation, the solar battery cell was heated to a temperature of 85 ° C. under a reduced pressure of about 10 kPa and subjected to a heat treatment for 15 hours.
The curve factor FF and the cell conversion efficiency Eff were evaluated about the photovoltaic cell which returned to room temperature after heat processing.

As is clear from Table 4, both the fill factor FF and the cell conversion efficiency Eff were increased by the heat treatment as in the case of the grid module.

(Comparative example)
As a comparative example, in this example, a single compound semiconductor solar cell which is a unit structure of a grid type module structure is manufactured under the same conditions as in Examples 1 to 3 and without applying the present invention.

Although there is only one type of laser scribing process, in addition to the transparent conductive film layer / high-resistance buffer layer / buffer layer as in the conventional mechanical scribing, a laser scribing process for removing the CIGS light absorbing layer is performed. .

In order to reduce even slight thermal damage to the CIGS light absorption layer which is weak to heat, an ultrashort pulse laser with a pulse width of 400 fs (femtoseconds) was used as the laser light.

The irradiation energy density per pulse of the ultrashort pulse laser is reduced to a low value of about 0.3 J / cm ² , the “pulse repetition” is 200 kHz, and scanning is performed twice at a speed of 0.43 m / s, A dividing groove for completely removing the CIGS light absorbing layer to the transparent conductive film layer was produced.
The scribing was performed for a total length of 32 mm surrounding a power generation area of about 52 mm ² in area.

The curve factor FF and the cell conversion efficiency Eff of the solar battery cells thus divided and created were evaluated.
The curve factor FF exhibited by 4 cells manufactured under the above conditions was 0.687 on average, and the cell conversion efficiency Eff was 15.4%.

On the other hand, for cells divided by mechanical scribing, the curvilinear factor FF was 0.782, and the battery conversion efficiency Eff was 17.8%.
In the cell divided by laser scribing, a reduction in conversion efficiency of about 2.3% was observed as compared with the cell divided by mechanical scribing.

It is used for module manufacturing of compound thin film solar cells represented by CIGS.

1 compound thin film solar cell 2 substrate layer 3 back electrode layer 4 compound semiconductor layer (CIGS light absorption layer)
5 buffer layer 6 high resistance buffer layer 7 transparent conductive film layer 8, 31 groove 9 shallow region 10 deep region 11, 11a, 11b, 11c substrate 12, 12a, 12b, 12c back electrode layer 13, 13a, 13b, 13c compound semiconductor Light absorbing layer 14, 14a Buffer layer 15, 15a High resistance buffer layer 16, 16a, 16b, 16c Transparent conductive film layer 17 First divided groove 18 Second divided groove 19 Third divided groove 21a, 21b, 21c, 21d by scribing Compound semiconductor light absorption layer / buffer layer / high- resistance buffer layer 23a, 23b, 23c divided by scribing back electrode layer 22a, 22b, 22c, 22d Transparent conductive film layer 32 divided by scribing Wiring 33, 34 Extraction electrode

Claims (7)

1. A substrate, a lower electrode formed by dividing a back electrode layer formed on the substrate by forming a first groove, and a second electrode formed on the plurality of lower electrodes at a position different from the first groove A structure in which a buffer layer and a high resistance buffer layer are sequentially stacked on a light absorption layer made of a compound semiconductor containing copper as a component, which is divided into a plurality of parts by groove formation, and the light absorption layer / buffer divided into the plurality A transparent conductive film layer formed in the upper surface of the layer / high resistance buffer layer laminate structure, and a second groove dividing the light absorption layer / buffer layer / high resistance buffer layer laminate structure, and the transparent conductive film layer A compound semiconductor constituted by an upper electrode formed by dividing a buffer layer / high-resistance buffer layer / transparent conductive film layer by forming a third groove leaving a light absorption layer at a position adjacent to the second groove A thin film solar cell,
   The compound semiconductor of the remaining light absorption layer is exposed at the bottom of the third groove,
   It is the Auger electron spectroscopy signal intensity derived from the copper contained in the compound semiconductor in the direction from the bottom face of the third groove to the back electrode with respect to the compound semiconductor, and the average value I _d of the signal intensity in the sufficiently deep region is the above What is claimed is: 1. A compound thin film solar cell characterized by not being larger than the maximum signal strength Is in a shallow region near the surface of a compound semiconductor.
2. A substrate, a back electrode layer formed on the substrate, and a light absorption layer made of a compound semiconductor containing copper as a component, a buffer layer, a high resistance buffer layer, and a transparent conductive film layer on the back electrode layer Divide the buffer layer / high-resistance buffer layer / transparent conductive film layer of the stacked structure into a small area solar battery cell constituted by the upper electrode formed by dividing the fourth groove leaving the light absorption layer A compound semiconductor thin film solar cell having the following structure;
   The compound semiconductor of the remaining light absorption layer is exposed at the bottom of the fourth groove,
   It is the Auger electron spectroscopy signal intensity derived from the copper contained in the compound semiconductor in the direction from the bottom surface of the fourth groove to the back electrode with respect to the compound semiconductor, and the average value I _d of the signal intensity in the sufficiently deep region is the above What is claimed is: 1. A compound thin film solar cell characterized by not being larger than the maximum signal strength Is in a shallow region near the surface of a compound semiconductor.
3. The compound thin film sun according to any one of claims 1 and 2, wherein the depth of the sufficiently deep region is 240 to 750 nm, and the depth of the shallow region is 90 nm or less. battery.
4. It is a manufacturing method of the compound thin film solar cell of any one of Claim 1 thru | or 3, Comprising:
   The third or fourth groove is scanned at least once in a line while irradiating a predetermined portion of the transparent conductive film layer with a pulse laser beam (referred to as a laser scribing step).
   Next, the manufacturing method of a compound thin film solar cell characterized by heat-processing and manufacturing the surface vicinity of the said compound semiconductor of the said light absorption layer exposed to the said scanned location.
5. The method for producing a compound thin film solar cell, wherein the pulse laser light is an ultrashort pulse laser having a pulse width of picosecond or femtosecond order.
6. The method of manufacturing a compound thin film solar cell according to claim 1, wherein the heat treatment is a heat treatment of heating at a temperature of 85 degrees for 1.5 hours or more, or at a temperature of 68 degrees for 5 hours or more.
7. A method of manufacturing a compound thin film solar cell having an integrated module structure, comprising:
   A laser beam is scanned on the back electrode layer (first laminated structure) formed on the substrate to form line-shaped first division grooves only in the back electrode layer, and the back electrode layer is formed on the substrate A first laser scribing step of dividing into a plurality of regions of 1;
   The high resistance buffer layer of a second laminated structure in which a light absorption layer made of a compound semiconductor, a buffer layer and a high resistance buffer layer are laminated in this order on the first laminated structure in which the first divided groove is formed. At the position different from the one division groove, scanning is performed in a line while irradiating pulse laser light under a predetermined irradiation condition, and a second division groove in a line shape having the back electrode layer as the bottom surface in the second laminated structure A second laser scribing step of forming the second laminated structure on the back electrode layer to form a second plurality of regions on the back electrode layer;
   The pulse laser beam is scanned in the form of a line while being irradiated with the pulse laser beam on the third laminated structure in which the transparent conductive layer is laminated on the second laminated structure in which the second divided groove is formed. Forming a line-shaped third divided groove whose bottom surface is the light absorption layer in the third laminated structure, and the transparent conductive layer and the back electrode are sequentially wired (connected) in pairs. And a third laser scribing step of dividing the third laminated structure into a plurality of third regions on the light absorption layer,
   The method for manufacturing a compound thin film solar cell having an integrated module structure according to any one of claims 4 to 6, wherein the laser scribing step is the third laser scribing step.

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