JP5729093B2 - The evaluation apparatus of a compound semiconductor thin film, the evaluation method of a compound semiconductor thin film, and the manufacturing method of a solar cell. - Google Patents

Description

  The present invention relates to a compound semiconductor thin film evaluation apparatus, a compound semiconductor thin film evaluation method, and a solar cell manufacturing method.

In place of the bulk crystal silicon solar cells that have been spreading in recent years, solar cells using compound semiconductor thin films as light absorption layers have been developed. Among them, a solar cell including a p-type compound semiconductor thin film including a group Ib, a group IIIb, and a group VIb as a light absorption layer exhibits high energy conversion efficiency and is not easily affected by deterioration due to light. It is expected as a solar cell. Specifically, CuInSe ₂ (hereinafter referred to as “CIS”) composed of Cu, In, and Se, or Cu (In _1−a , Ga _a ) in which part of In that is a group IIIb in CIS is replaced with Ga. ) High conversion efficiency is obtained in solar cells using Se ₂ (hereinafter referred to as “CIGS”) as a light absorption layer (see Patent Documents 1 and 2 below). In addition, a method for evaluating the light absorption characteristics of a compound semiconductor by using its electrolytic response with an electrolytic solution is known (see Patent Document 3 below).

Special table 2009-515343 Japanese National Patent Publication No. 10-513606 PCT / EP2010 / 055657

  In the industrial production of solar cells using a compound semiconductor thin film as a light absorbing layer, defects such as pinholes and low-resistance sites consisting of by-products are formed in the compound semiconductor thin film in the formation process of the compound semiconductor thin film. . These defects cause defects in the solar cell and reduce the yield of the solar cell. However, conventionally, it has been difficult to inspect for the presence of defects in a short time when a compound semiconductor thin film is formed during the production of a solar cell.

  As a method for evaluating a compound semiconductor thin film at a laboratory level, there is a method of electrochemically measuring the light response characteristics of a light absorption layer while blinking light in an electrolytic solution. However, when such an evaluation method is applied to, for example, a relatively large light absorption layer of 10 cm square, it is difficult to apply uniform light to the entire surface of the light absorption layer, and a large electrolytic bath that can accommodate the entire light absorption layer Was a problem. Therefore, it has been difficult to carry out the laboratory-level evaluation method during the industrial production of solar cells. Further, in the laboratory level evaluation method, light is irradiated on the entire surface of the light absorption layer, so that only average information of the entire light absorption layer can be obtained. Further, in the evaluation method using the electrolytic solution tank, even if an attempt is made to cover the entire region of the light absorption layer by moving only the place where light is applied in the light absorption layer, the entire light absorption layer is immersed in the electrolyte solution. Local evaluation of current cannot be performed. Therefore, even if a short circuit failure is found, it is difficult to identify the location of the defect that is the cause.

  The present invention has been made in view of the above-described problems of the prior art, and includes an evaluation apparatus and an evaluation method for a compound semiconductor thin film capable of detecting a partial defect in the compound semiconductor thin film and inspecting the entire compound semiconductor thin film, And it aims at providing the manufacturing method of the solar cell which can detect the partial defect of a compound semiconductor thin film, and the test | inspection of the whole compound semiconductor thin film in the middle of manufacture of a solar cell.

  In order to achieve the above object, a compound semiconductor thin film evaluation apparatus according to the present invention includes a light-shielding exterior body in which an opening is formed, and a translucent material positioned inside the opening to close the opening. A polymer gel electrolyte layer, an electrolyte infiltrated into the polymer gel electrolyte layer, a light source for irradiating light on the surface of the polymer gel electrolyte layer located inside the exterior body and facing the interior of the exterior body, and the exterior body The counter electrode that contacts part of the surface of the polymer gel electrolyte layer facing the inside, the reference electrode that contacts part of the surface of the polymer gel electrolyte layer facing the inside of the exterior body, and the counter electrode and reference electrode are electrically And a potentiostat connected to the main body.

  In the method for evaluating a compound semiconductor thin film according to the present invention, only a part of the surface of the compound semiconductor thin film formed on the conductive layer that is the working electrode is covered with a light-transmitting polymer gel electrolyte layer infiltrated with an electrolyte solution. The compound semiconductor thin film and the polymer gel electrolyte layer are brought into close contact with each other, the counter electrode and the reference electrode are brought into contact with a part of the surface of the polymer gel electrolyte layer facing away from the compound semiconductor thin film, and the counter electrode and the reference electrode are brought into contact with each other. When the applied polymer gel electrolyte layer is confined inside the light-shielding exterior body and a voltage is applied between the working electrode and the counter electrode while the light source placed inside the exterior body emits light, the reference electrode is used as a standard. Measure the potential of the working electrode and the current between the working electrode and the counter electrode, and when the voltage is applied between the working electrode and the counter electrode without causing the light source to emit light, the reference electrode is used as a reference. Measure the potential of the working electrode and the current between the working electrode and the counter electrode. , Comprising a partial inspection step, by repeating the partial inspection step to inspect the entire compound semiconductor thin film.

  According to the compound semiconductor thin film evaluation apparatus of the present invention, the semiconductor thin film evaluation method of the present invention can be easily implemented.

  According to the method for evaluating a compound semiconductor thin film according to the present invention, it is possible to detect a partial defect of the compound semiconductor thin film and to inspect the entire compound semiconductor thin film by electrochemical measurement.

  In the compound semiconductor thin film evaluation apparatus and evaluation method according to the present invention, the electrolytic solution is preferably an aqueous solution of a europium salt. When the compound semiconductor thin film contains CIGS, an aqueous solution of europium salt is suitable as the electrolytic solution.

  In the method for manufacturing a solar cell according to the present invention, the step of forming the compound semiconductor thin film on the conductive layer, and the compound semiconductor thin film evaluation method according to the present invention are performed on the compound semiconductor thin film, and then the compound semiconductor thin film Forming another thin film on the surface.

  According to the method for manufacturing a solar cell according to the above basic invention, it is possible to detect a partial defect in the compound semiconductor thin film and inspect the entire compound semiconductor thin film during the manufacturing of the solar cell.

  According to the present invention, an evaluation apparatus and an evaluation method for a compound semiconductor thin film capable of detecting a partial defect in the compound semiconductor thin film and inspecting the entire compound semiconductor thin film, and a compound semiconductor thin film in the course of manufacturing a solar cell. It is possible to provide a method of manufacturing a solar cell that can detect a partial defect and inspect the entire compound semiconductor thin film.

FIG. 1 is a perspective view of a compound semiconductor thin film evaluation apparatus according to an embodiment of the present invention. 2 is a cross-sectional view taken along the line II-II of the evaluation apparatus shown in FIG. 3 is a cross-sectional view of the evaluation apparatus shown in FIGS. 1 and 2 taken along the line III-III. FIG. 4A is a diagram illustrating a method for evaluating a compound semiconductor thin film according to an embodiment of the present invention, using the compound semiconductor thin film evaluation apparatus according to an embodiment of the present invention. 4B is a cross-sectional view of the evaluation apparatus, the compound semiconductor thin film, the conductive layer, and the substrate shown in FIG. 4A taken along line BB. FIG. 4C is an enlarged view of region C shown in FIG. 4B. FIG. 5 is a cross-sectional view of a solar cell obtained by the method for manufacturing a solar cell according to one embodiment of the present invention. FIG. 6 is a schematic diagram showing a method for evaluating a compound semiconductor thin film according to a comparative example of the present invention.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings. In the drawings, the same or equivalent elements are denoted by the same reference numerals. Also, the positional relationship between the top, bottom, left and right is as shown in the drawing. Further, when the description overlaps, the description is omitted.

(Evaluation equipment for compound semiconductor thin films)
As shown in FIGS. 1 to 4, the compound semiconductor thin film evaluation apparatus 2 according to this embodiment includes a light-shielding exterior body 4, a transparent polymer gel electrolyte layer 6, an electrolyte solution holding layer 12, a counter electrode 8, and a reference electrode. 10, a transparent separator 14, a pin 20, an optical filter 16, a light source 18, and a potentiostat 60.

  The light-shielding exterior body 4 has a hollow box-like structure. An opening is formed at the bottom of the exterior body 4.

  The flat polymer gel electrolyte layer 6 is located inside the opening of the outer package 4 and closes the opening. That is, the polymer gel electrolyte layer 6 constitutes a flat bottom surface of the evaluation device 2. The polymer gel electrolyte layer 6 is infiltrated with an electrolytic solution.

  The polymer gel electrolyte layer 6 is not particularly limited as long as it has conductivity of ions derived from the electrolyte dissolved in the electrolyte solution infiltrated therein.

  As a specific polymer gel electrolyte layer 6, for example, a highly water-absorbing polymer having a property of absorbing water to swell can be used as a host, and a gel formed by impregnating an electrolytic solution can be used. Examples of superabsorbent polymers include cellulose acetate, polyvinyl alcohol, poly N vinyl pyrrolidone, polyacrylamide, cellulose, carboxymethyl cellulose, nitrocellulose, cyanoethyl cellulose, cellulose sulfate, heparin, pectin, alginic acid, hydroxymethyl cellulose, isopropyl cellulose, polyacrylic. Examples thereof include polymers, such as acid, polyethylene oxide, poly (3,4-ethylenedioxythiophene) -poly (styrenesulfonic acid), which are insolubilized in water by heat treatment or crosslinking. Moreover, you may use the copolymer obtained by bridge | crosslinking 2 or more types of polymers among said water-soluble polymer. For example, when the water-soluble polymer is polyvinyl alcohol, by adding boric acid as a cross-linking agent, the polyvinyl alcohol is secondarily cross-linked to become a quasi-solid state, and the strength of the polymer gel electrolyte layer is increased.

  Even a water-insoluble polymer that hardly swells with water can be used as the polymer gel electrolyte layer 6 by copolymerizing with a water-soluble polymer at an appropriate fraction to improve the degree of swelling in water. it can. Examples of the water-insoluble polymer include polyvinylidene fluoride and polytetrafluoroethylene.

  After forming a water-soluble polymer solution in which a photocrosslinkable monomer is dissolved, a highly water-absorbing polymer can be obtained by irradiating the film with light to form a crosslinked structure. Such a superabsorbent polymer may be used as the polymer gel electrolyte layer 6. Examples of such a polymer include photocrosslinkable polyvinyl alcohol, photocrosslinkable polyethylene oxide, and photocrosslinkable polyethylene glycol.

  A water-soluble polymer coated with an ionic polymer may be used as the polymer gel electrolyte layer 6. By coating the water-soluble polymer with the ionic polymer, the ion conductivity of the water-soluble polymer is improved, and the defect detection accuracy of the compound semiconductor thin film is improved. Examples of the ionic polymer include polyvinyl sulfonic acid, polystyrene sulfonic acid, and Nafion.

  The electrolyte solution holding layer 12 made of a translucent electrolyte solution is disposed on the surface of the polymer gel electrolyte layer 6 facing the inside of the outer package 4. When the evaluation device 2 includes the electrolyte solution holding layer 12, a large amount of electrolyte exists between the compound semiconductor thin film formed on the working electrode and the counter electrode 8 as compared with the case where the electrolyte solution holding layer 12 is not provided. A large current is allowed to flow between the working electrode and the counter electrode, a current is generated for a long time, or the current can easily flow, thereby improving the defect detection accuracy. Even in the case where the electrolyte solution holding layer 12 is not provided, the effect of the present invention can be achieved if the electrolyte solution is infiltrated into the polymer gel electrolyte layer 6, and therefore the electrolyte solution holding layer 12 is not essential. .

The electrolytic solution is preferably an aqueous solution of europium salt. When the compound semiconductor thin film is a CIGS thin film, an aqueous solution of a europium salt is suitable as an electrolytic solution. The redox potential of Eu ²⁺ / Eu ³⁺ is close to the conduction band edge of CIGS in the dark, and can correspond to the solid state pn junction of CIGS / CdS. As an electrolyte other than the europium salt, a vanadium salt may be used. That is, the evaluation method for a compound semiconductor thin film according to the present invention can be carried out using the redox potential of V ²⁺ / V ³⁺ .

  The counter electrode 8 is in partial contact with the surface of the polymer gel electrolyte layer 6 facing the inside of the outer package 4. As shown in FIG. 3, the counter electrode 8 has a frame-like structure along the four sides of the rectangular polymer gel electrolyte layer 6. The counter electrode 8 is made of a metal such as Pt, for example.

  The reference electrode 10 is in contact with a part of the surface of the polymer gel electrolyte layer 6 facing the inside of the exterior body. As shown in FIG. 3, the reference electrode 10 is located at each of the four corners of the rectangular polymer gel electrolyte layer 6. The reference electrode 10 is made of, for example, Ag / AgCl. The reference electrode 10 is fixed to the exterior body 4 by pins 20 connected thereto. The pin 20 may have a wiring function for electrically connecting the reference electrode 10 and the potentiostat 60. The pin 20 is not essential in the present invention.

  The counter electrode 8 is separated from the reference electrode 10. Further, the counter electrode 8 and the reference electrode 10 do not cover the entire surface of the polymer gel electrolyte layer 6 but only a part thereof. In other words, the light from the light source 18 must not be completely blocked by the counter electrode 8 and the reference electrode 10. As long as these conditions are satisfied, the positions and shapes of the counter electrode 8 and the reference electrode 10 are not particularly limited.

  The transparent separator 14 separates the polymer gel electrolyte layer 6, the electrolyte solution holding layer 12, the counter electrode 8 and the reference electrode 10, the optical filter 16 and the light source 18.

  The optical filter 16 has a function of transmitting, for example, only light (for example, monochromatic light) in a predetermined wavelength region that excites electrons in the valence band of the compound semiconductor thin film to the conduction band among the light emitted from the light source 18. The optical filter 16 may be replaced according to the wavelength region of light to be shielded. By exchanging the optical filter 16, the response characteristic of the compound semiconductor thin film with respect to a predetermined wavelength region can be examined. Further, a shutter having a function of blocking part or all of the light emitted from the light source 18 may be replaced with the optical filter 16. A shutter may be provided at a position adjacent to the optical filter 16. When the light source 18 that emits only light in a predetermined wavelength region is selected, the effects of the present invention can be achieved even if the evaluation device 2 does not include the optical filter 16 or the shutter. Therefore, the optical filter 16 and the shutter are not essential in the present invention.

  The light source 18 is installed on the upper surface inside the exterior body 4. The light source 18 irradiates light toward the surface of the polymer gel electrolyte layer 6 facing the inside of the exterior body 4. The light source 18 emits light in a predetermined wavelength region that excites electrons in the valence band of the compound semiconductor thin film to the conduction band. As long as this is the case, the light source 18 is not particularly limited. For example, an LED or a flat organic EL may be used as the light source 18.

  The counter electrode 8 is electrically connected to the potentiostat 60 via the wiring 8L. The reference electrode 10 is electrically connected to the potentiostat 60 via the wiring 10L.

(Method for evaluating compound semiconductor thin film)
Below, the evaluation method of the compound semiconductor thin film using the above-mentioned evaluation apparatus 2 is demonstrated as an evaluation method of the compound semiconductor thin film which concerns on this embodiment.

  As shown in FIG. 4B, a conductive layer as the working electrode 42 is formed on the surface of the substrate 44. A compound semiconductor thin film 40 is formed on the surface of the working electrode 42. The working electrode 42 is electrically connected to the potentiostat 60 via the wiring 42L. The substrate 44 is not essential in the method for evaluating the compound semiconductor thin film 40.

[Partial inspection process]
In the partial inspection process, as shown in FIG. 4C, the polymer gel electrolyte layer 6 located on the bottom surface of the evaluation device 2 is brought into close contact with the surface of the compound semiconductor thin film 40. When the polymer gel electrolyte layer 6 is brought into close contact with the compound semiconductor thin film 40, excess electrolyte infiltrated into the polymer gel electrolyte layer 6 oozes out to the interface 46 between the compound semiconductor thin film 40 and the polymer gel electrolyte layer 6. The area of the polymer gel electrolyte layer 6 is smaller than the area of the compound semiconductor thin film 40 to be evaluated. Therefore, the polymer gel electrolyte layer 6 covers only a part of the surface of the compound semiconductor thin film 40.

As shown in FIG. 4C, the polymer gel electrolyte layer 6 is confined inside the light-shielding exterior body 4. Therefore, when the light source 18 disposed inside the exterior body 4 emits light, only the light from the light source 18 is irradiated onto the compound semiconductor thin film 40 covered with the polymer gel electrolyte layer 6. That is, light from the outside of the outer package 4 is blocked from the compound semiconductor thin film 40. When the compound semiconductor thin film 40 is irradiated with light from the light source 18, electrons in the valence band of the compound semiconductor thin film 40 are excited to the conductor. When the light source 18 emits light, a voltage is applied between the working electrode 42 and the counter electrode 8, and the potential of the working electrode 42 with respect to the reference electrode 10 is adjusted to a negative value. Ions move and are reduced on the surface of the compound semiconductor thin film 40. As a result, a current (photocurrent) flows between the working electrode 42 and the counter electrode 8. For example, when the electrolytic solution is an aqueous solution of Eu salt, Eu ³⁺ moved from the counter electrode 8 to the compound semiconductor thin film 40 is reduced on the surface of the compound semiconductor thin film 40 to generate Eu ²⁺ .

In the partial inspection step, the potential of the working electrode 42 with respect to the reference electrode 10 and the photocurrent corresponding to the potential are measured by the method described above. More specific photocurrent measurement methods include a potential scanning method in which the potential of the working electrode 42 with respect to the reference electrode 10 is changed, or a constant potential method in which the potential of the working electrode 42 with respect to the reference electrode 10 is maintained at a constant value. It is done. During the measurement of the photocurrent, the light source 18 may be blinked as in a normal electrochemical measurement method.

  In the partial inspection process, when the voltage is applied between the working electrode 42 and the counter electrode 8 without causing the light source to emit light while the polymer gel electrolyte layer 6 is in close contact with the compound semiconductor thin film 40, the action on the reference electrode 10 is performed. The potential of the pole 42 and the current (dark current) between the working electrode 42 and the counter electrode 8 are measured.

  The entire region of the surface of the compound semiconductor thin film 40 can be inspected by repeating the above partial inspection process while changing the position of the evaluation apparatus 2 with respect to the compound semiconductor thin film 40. The pinhole formed in the compound semiconductor thin film 40 reduces photocurrent and dark current. The low resistance portion formed in the compound semiconductor thin film 40 increases photocurrent and dark current. When the specific surface area of the low resistance portion is large, the low resistance portion may increase the dark current as a double layer capacity. That is, in a region where a pinhole or a low resistance region exists, a photocurrent or dark current having a value different from that of other regions is measured. Therefore, by comparing the photocurrent and dark current measured in each partial inspection step with each other, it is possible to specify a portion where a defect such as a pinhole or a low resistance portion is formed in the compound semiconductor thin film 40.

(Method for manufacturing solar cell)
Below, the manufacturing method of a solar cell provided with the CIGS thin film which is 1 type of a p-type compound semiconductor thin film as a light absorption layer is demonstrated.

  As shown in FIGS. 4B and 5, a back electrode layer 42 as a conductive layer (working electrode) is formed on soda lime glass 44 as a substrate. The back electrode layer 42 is usually a metal layer made of Mo. Examples of the method for forming the back electrode layer 42 include sputtering of a Mo target.

  After the back electrode layer 42 is formed on the soda lime glass 44, the CIGS thin film 40 is formed on the back electrode layer 42. Examples of the method of forming the CIGS thin film 40 include electrolytic deposition, one-step simultaneous vapor deposition (one-step), three-step simultaneous vapor deposition (NREL), solid-phase selenization, or vapor-phase selenization. . In the process of forming the CIGS thin film 40, defects such as pinholes and metallic low-resistance portions may be formed in the CIGS thin film 40 in some cases.

  After the CIGS thin film 40 is formed on the back electrode layer 42, the CIGS thin film 40 is inspected using the compound semiconductor thin film evaluation method according to this embodiment described above. This makes it possible to specify the location of defects formed in the CIGS thin film 40 in the process of forming the CIGS thin film 40 and to inspect the entire CIGS thin film 40.

After the CIGS thin film 40 is inspected, another thin film (n-type compound semiconductor thin film 61) is formed on the CIGS thin film 40, a semi-insulating layer 63 is formed on the n-type compound semiconductor thin film, and the semi-insulating layer 63 is formed on the semi-insulating layer 63. A window layer 65 is formed, and an upper electrode 67 is formed on the window layer 65. Thereby, the solar cell 102 is obtained. Note that an antireflection layer made of MgF ₂ may be formed on the window layer 65.

Examples of the n-type compound semiconductor thin film 61 include a CdS thin film, a ZnO (S 2 _, Se) thin film _{, and an} n-type CIGS thin film. The CdS thin film or the ZnO (S 2 _, Se) thin film can be formed by a chemical solution growth method, a sputtering method, a vapor deposition method, or the like. The n-type CIGS thin film can be formed by the same method as the p-type CIGS thin film 40 described above. Examples of the semi-insulating layer 63 include an i-ZnO layer. Examples of the window layer 65 include ZnO: B or ZnO: Al. The upper electrode 67 is made of a metal such as Al or Ni. The semi-insulating layer 63, the window layer 65, and the upper electrode 67 can be formed by sputtering or MOCVD, for example.

  In the present embodiment, as described above, the presence or absence of defects can be inspected when the compound semiconductor thin film 40 is formed during the production of the solar cell. That is, in this embodiment, a nondestructive inspection of a solar cell is possible. In other words, in this embodiment, in order to evaluate the compound semiconductor thin film 40, it is not necessary to destroy the completed solar cell 102 and expose the compound semiconductor thin film 40. Moreover, in this embodiment, the partial evaluation process with respect to the area | region covered with the polymer gel electrolyte layer 6 whose area is smaller than the compound semiconductor thin film 40 is implemented in multiple times, and the whole compound semiconductor thin film can be test | inspected. Therefore, in this embodiment, unlike the conventional evaluation method, a large electrolytic bath that accommodates the entire compound semiconductor thin film is not required. Therefore, the evaluation method of this embodiment can be easily implemented during the industrial production of solar cells.

  In the present embodiment, even when a relatively large compound semiconductor thin film 40 is evaluated, the entire region to be evaluated is confined by enclosing a part of the compound semiconductor thin film 40 as an evaluation target in the exterior body 4 of the evaluation apparatus 2. The light can be evenly applied to. Further, in this embodiment, it is possible to measure not only the average photoresponse characteristics of the entire compound semiconductor thin film but also the local photoresponse characteristics of the compound semiconductor thin film by electrochemical measurement. Local defects in the semiconductor thin film can be detected.

  As mentioned above, although one suitable embodiment of the present invention was described in detail, the present invention is not limited to the above-mentioned embodiment.

For example, the method for evaluating a compound semiconductor thin film and the method for manufacturing a solar cell according to the present invention can be applied even when the compound semiconductor thin film is not a CIGS thin film. For example, the compound semiconductor thin film is a GaAs based semiconductor thin film, a SiGe based semiconductor thin film, a CIS based semiconductor thin film, a Cu ₂ ZnSnS ₄ based semiconductor thin film, a CdTe based semiconductor thin film, a CdS based semiconductor thin film, an InP based semiconductor thin film, a ZnO based semiconductor thin film, or Even in the case of a CuAlO ₂ -based semiconductor thin film or the like, the same effects as those of the above-described embodiment can be achieved.

  A non-hydrophilic polymer gel electrolyte layer and a non-aqueous electrolyte may be used. Also in this case, the same effect as the above-described embodiment can be achieved.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

Example 1
As shown in FIGS. 4A and 4B, a Mo back electrode layer 42 was formed on the soda lime glass 44 as a working electrode. Sputtering was used to form the Mo back electrode layer 42. A Cu _0.75 In _0.7 Ga _0.30 Se ₂ thin film 40 was formed as a compound semiconductor thin film on the Mo back electrode layer 42. For the formation of the Cu _0.75 In _0.7 Ga _0.30 Se ₂ thin film 40, electrolytic deposition was used. The surface area of the Mo back electrode layer 42 was 10 cm × 10 cm. The surface area of the Cu _0.75 In _0.7 Ga _0.30 Se ₂ thin film 40 was made substantially the same as that of the Mo back electrode layer 42. Thus, to prepare three samples 1 to 3 comprising a soda lime glass substrate 44, Mo back electrode layer 42 and _Cu 0.75 _In 0.7 _{Ga 0.30} Se ₂ thin film 40.

Using the evaluation apparatus 2 shown in FIGS. 1 to 3, as shown in FIGS. 4A, 4B and 4C, the Cu _0.75 In _0.7 Ga _0.30 Se ₂ thin film 40 of each of the samples 1 to 3 The partial inspection process described above was performed. Also, moving the evaluation device 2 so as to cover the entire surface of each of the _Cu 0.75 _In 0.7 _{Ga 0.30} Se ₂ thin film 40 was performed several times a partial inspection process.

As the polymer gel electrolyte layer 6, a layer made of polyvinyl alcohol (PVA) was used. The dimension of the polymer gel electrolyte layer 6 was 1 cm × 1 cm. The polymer gel electrolyte layer 6 was infiltrated with 0.2 M Eu (NO ₃ ) ₃ aqueous solution as an electrolytic solution. Further, a 0.2 M Eu (NO ₃ ) ₃ aqueous solution was used as the electrolyte holding layer 12. A 0.6 cm × 0.6 cm Pt electrode was used as the frame-shaped counter electrode 8. As the reference electrode 10, an Ag / AgCl electrode was used. As the light source 18, an LED was used.

  In the partial inspection step, the photocurrent density and dark current density between the Mo back electrode layer 42 and the Pt electrode 8 were measured by a constant potential method. In the constant potential method, the light source 18 was blinked at a frequency of 20 Hz, the potential of the Mo back electrode layer 42 was fixed to −0.3 V with respect to the Ag / AgCl electrode 10, and the current was applied for 0.5 seconds.

For the Cu _0.75 In _0.7 Ga _0.30 Se ₂ thin film 40 of Samples 1 and 2, a good and uniform photocurrent density and a low level of dark current were measured over the entire region. In the Cu _0.75 In _0.7 Ga _0.30 Se ₂ thin film 40 of Sample 3, photoresponse failure (small photocurrent compared to other regions) was confirmed in the partial inspection process in a certain region. This poor optical response is considered to be caused by pinholes formed in the Cu _0.75 In _0.7 Ga _0.30 Se ₂ thin film 40. In other areas, a larger dark current density was observed than in other areas. This large dark current density is caused by the electric double layer generated at the interface between the low resistance portion formed on the surface of the Cu _0.75 In _0.7 Ga _0.30 Se ₂ thin film 40 and the polymer gel electrolyte layer 6. This is thought to be due to the increase in the capacitance at the interface. As described above, in Example 1, not only the optical response characteristics of the entire surface of the Cu _0.75 In _0.7 Ga _0.30 Se ₂ thin film 40 but also the defective part of the optical response characteristics and the cause thereof could be specified.

(Comparative Example 1)
In Comparative Example 1, the Cu _0.75 In _0.7 Ga _0.30 Se ₂ thin film 40 of Samples 1 to 3 used in Example 1 was individually evaluated with the evaluation apparatus shown in FIG. In addition, the whole evaluation apparatus shown in FIG. 6 is installed in the dark box under room temperature.

As an evaluation apparatus of Comparative Example 1, an electrolyte tank 52 (beaker) filled with 10 mL of an electrolyte solution 54, a reference electrode 56 and a counter electrode 58 which are arranged in the electrolyte tank 52 and electrically connected to the potentiogalvanostat 60. The apparatus provided with these was used. As the electrolytic solution 54, a 0.2M Eu (NO ₃ ) ₃ aqueous solution was used. A normal Ag / AgCl electrode was used as the reference electrode 56. As the counter electrode 58, a Pt spiral electrode was used.

In Comparative Example 1, the Mo back electrode layer 42 included in the sample disposed in the electrolytic solution 54 was electrically connected to the potentiostat 60. The Cu _0.75 In _0.7 Ga _0.30 Se ₂ thin film 40 included in the sample disposed in the electrolytic solution 54 was opposed to the light source 50. An LED was used as the light source 50.

In Comparative Example 1, the photocurrent density between the Mo back electrode layer 42 and the Pt electrode 8 and the dark current density were measured by a constant potential method inside the dark box. In the constant potential method, the light source 50 was blinked at a frequency of 20 Hz, and the entire surface of the Cu _0.75 In _0.7 Ga _0.30 Se ₂ thin film 40 was irradiated with light. In the constant potential method, the potential of the Mo back electrode layer 42 was fixed to −0.3 V with respect to the Ag / AgCl electrode 56, and the current was applied for 0.5 seconds.

In Comparative Example 1, a significant difference in the photoresponse characteristics of Samples 1 to 3 could not be confirmed. In Comparative Example 1, the local photoresponse characteristics of Samples 1 to 3 could not be evaluated. Therefore, in Comparative Example 1, it was not possible to detect an abnormality in the light response characteristics in the Cu _0.75 In _0.7 Ga _0.30 Se ₂ thin film 40 of Sample 3.

DESCRIPTION OF SYMBOLS 2 ... Evaluation apparatus of a compound semiconductor thin film, 4 ... Exterior body, 6 ... Polymer gel electrolyte layer, 8, 58 ... Counter electrode, 10, 56 ... Reference electrode, 12 ... Electrolysis Liquid retaining layer, 14 ..Transparent separator, 16... Optical filter, 18, 50... Light source, 20... Pin, 40 ... compound semiconductor thin film (CIGS thin film), 42. (Conductive layer or Mo back electrode layer), 44 ... substrate (soda lime glass), 52 ... electrolytic bath, 54 ... electrolytic solution, 62 ... insulating PTFE tape, 60 ... potentiometer Stat, 61 ... n-type compound semiconductor thin film, 63 ... semi-insulating layer, 65 ... window layer (transparent conductive layer), 67 ... upper electrode (extraction electrode), 102 ... solar cell.

Claims (5)

A light-shielding exterior body in which an opening is formed;
A flat and square translucent polymer gel electrolyte layer that is located inside the opening and that covers the opening and forms a flat bottom surface;
An electrolyte solution infiltrated into the polymer gel electrolyte layer;
A light source that is located inside the exterior body and uniformly irradiates light onto the surface of the polymer gel electrolyte layer facing the inside of the exterior body;
A part of the surface of the polymer gel electrolyte layer facing the inside of the outer package , and along the four sides of the polymer gel electrolyte layer , and a frame-shaped counter electrode;
A reference electrode in contact with a part of the surface of the polymer gel electrolyte layer facing the inside of the exterior body;
The polymer gel electrolyte layer, the counter electrode and the reference electrode, and a transparent separator for isolating the light source,
A potentiostat in which the counter electrode and the reference electrode are electrically connected;
Comprising
Evaluation equipment for compound semiconductor thin films. The electrolyte is an aqueous solution of a europium salt;
The apparatus for evaluating a compound semiconductor thin film according to claim 1. Only a part of the surface of the compound semiconductor thin film formed on the conductive layer, which is the working electrode, is a flat and square translucent polymer gel electrolyte layer that forms a flat bottom surface infiltrated with the electrolyte. Covering and adhering the compound semiconductor thin film and the polymer gel electrolyte layer,
A part of the surface of the polymer gel electrolyte layer facing the opposite side to the compound semiconductor thin film , along the four sides of the polymer gel electrolyte layer , and a frame-shaped counter electrode and a reference electrode are contacted,
The polymer gel electrolyte layer in contact with the counter electrode and the reference electrode is confined inside a light-shielding exterior body,
A light source arranged so as to be separated from the polymer gel electrolyte layer, the counter electrode and the reference electrode by a transparent separator on the inner side of the outer package, and emitting light uniformly, while the working electrode and the counter electrode Measuring a potential of the working electrode relative to the reference electrode and a current between the working electrode and the counter electrode when a voltage is applied between them;
When a voltage is applied between the working electrode and the counter electrode without causing the light source to emit light, a potential of the working electrode with respect to the reference electrode, and a current between the working electrode and the counter electrode, A partial inspection process,
Inspecting the entire compound semiconductor thin film by repeating the partial inspection step,
Evaluation method of compound semiconductor thin film. The electrolyte is an aqueous solution of a europium salt;
The method for evaluating a compound semiconductor thin film according to claim 3. Forming a compound semiconductor thin film on the conductive layer;
A step of forming another thin film on the surface of the compound semiconductor thin film after performing the method for evaluating a compound semiconductor thin film according to claim 3 or 4 on the compound semiconductor thin film;
Comprising
A method for manufacturing a solar cell.

Images