JP2012015257A - Photoelectric conversion device and method for manufacturing photoelectric conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion device having high photoelectric conversion efficiency.SOLUTION: A photoelectric conversion device 10 has a I-III-VI compound semiconductor including a Group VI element which is a chalcogen element, as a main component, and includes a semiconductor layer 3 including a silicon element and an oxygen element. Moreover, a method for manufacturing the photoelectric conversion device 10 includes: a step of producing a precursor layer including a Group I element and a Group III element; and a step of producing the semiconductor layer 3 by placing the precursor layer and silicon in a calcination furnace and heating the precursor layer and the silicon while introducing gas including the chalcogen element into the calcination furnace.

Description

  The present invention relates to a photoelectric conversion device including a group I-III-VI compound semiconductor.

  As a photoelectric conversion device used for solar power generation or the like, there is one in which a light absorption layer is formed of a chalcopyrite-based I-III-VI group compound semiconductor such as CIGS having a high light absorption coefficient. I-III-VI group compound semiconductors have a high light absorption coefficient, and are suitable for reducing the thickness, area, and cost of photoelectric conversion devices, and research and development of next-generation solar cells using them is underway. .

  In a photoelectric conversion device using such an I-III-VI group compound semiconductor layer, it is difficult to improve the photoelectric conversion efficiency due to defects present in the I-III-VI group compound semiconductor layer. In Patent Document 1, by introducing water or a hydroxyl group when forming the I-III-VI group compound semiconductor layer, the anion vacancies generated in the I-III-VI group compound semiconductor layer are filled with oxygen and defects are removed. Inhibiting is described.

JP 2000-114561 A

  However, in the method of Patent Document 1, when forming the I-III-VI group compound semiconductor layer, since the oxidation of the raw metal proceeds, it is difficult to produce a good I-III-VI group compound semiconductor layer. is there. Therefore, the photoelectric conversion efficiency cannot be sufficiently increased.

  This invention is made | formed in view of the said subject, and it aims at providing the photoelectric conversion apparatus with high photoelectric conversion efficiency which forms the I-III-VI group compound semiconductor layer with few defects favorably.

  A photoelectric conversion device according to an embodiment of the present invention includes a semiconductor layer containing a silicon element and an oxygen element as a main component of a group I-III-VI compound semiconductor in which a group VI element is a chalcogen element. And

  A method for producing a photoelectric conversion device according to an embodiment of the present invention includes a step of producing a precursor layer containing a group I element and a group III element, placing the precursor layer and silicone in a firing furnace, And a step of producing the semiconductor layer by heating the precursor layer and the silicone while introducing a gas containing a chalcogen element into a baking furnace.

  ADVANTAGE OF THE INVENTION According to this invention, a photoelectric conversion apparatus with high photoelectric conversion efficiency can be provided.

It is a perspective view which shows an example of embodiment of the photoelectric conversion apparatus of this invention. It is sectional drawing of the photoelectric conversion apparatus of FIG. It is a principal part expanded sectional view which shows the other example of embodiment of the photoelectric conversion apparatus of this invention. It is sectional drawing which shows the other example of embodiment of the photoelectric conversion apparatus of this invention.

  FIG. 1 is a perspective view showing an example of an embodiment of a photoelectric conversion device of the present invention, and FIG. 2 is a sectional view thereof. FIG. 3 is an enlarged cross-sectional view of the main part showing another example of the embodiment of the photoelectric conversion device of the present invention. FIG. 4 is a cross-sectional view showing another example of the embodiment of the photoelectric conversion device of the present invention. (In FIG. 3, FIG. 4, the same code | symbol is attached | subjected to the site | part of the same structure as FIG.1,2.). The photoelectric conversion device 10 includes a substrate 1, a first semiconductor layer 3, a second semiconductor layer 4, and a second electrode layer 5. In this embodiment, an example is shown in which the first semiconductor layer 3 is a light absorption layer and the second semiconductor layer 4 is a buffer layer bonded to the first semiconductor layer 3, but the present invention is not limited thereto. Alternatively, the second semiconductor layer 4 may be a light absorption layer.

  1 and 2, a photoelectric conversion device 10 is formed by arranging a plurality of photoelectric conversion cells 11. The photoelectric conversion cell 11 includes a third electrode layer 6 provided on the substrate 1 side of the first semiconductor layer 3 so as to be separated from the first electrode layer 2. The second electrode layer 5 and the third electrode layer 6 are electrically connected by the connection conductor 7 provided in the first semiconductor layer 3. The third electrode layer 6 is integrated with the first electrode layer 2 of the adjacent photoelectric conversion cell 11. With this configuration, adjacent photoelectric conversion cells 11 are connected in series. In one photoelectric conversion cell 11, the connection conductor 7 is provided so as to penetrate the first semiconductor layer 3 and the second semiconductor layer 4, and the first electrode layer 2 and the second electrode layer are provided. The first semiconductor layer 3 and the second semiconductor layer 4 sandwiched between 5 and 5 perform photoelectric conversion.

  The substrate 1 is for supporting the photoelectric conversion device 10. Examples of the material used for the substrate 1 include glass, ceramics, resin, and metal.

  The first electrode layer 2 and the third electrode layer 6 are made of a conductor such as Mo, Al, Ti, or Au, and are formed on the substrate 1 by a sputtering method or a vapor deposition method.

The first semiconductor layer 3 has a chalcopyrite structure in which a group I-III-VI compound semiconductor whose group VI element is a chalcogen element is a main component (occupies 60 mol% or more of the compound constituting the first semiconductor layer 3). For example, it is formed in a layer shape having a thickness of 1.0 to 2.5 μm. The chalcogen element means S, Se, or Te among VI-B group elements (also referred to as group 16 elements). The I-III-VI group compound semiconductor is a compound semiconductor of a group IB element (also referred to as group 11 element), a group III-B element (also referred to as group 13 element), and a group VI-B element. It has a chalcopyrite structure and is called a chalcopyrite compound semiconductor. Examples of the I-III-VI group compound semiconductor include Cu (In, Ga) Se ₂ (also referred to as CIGS), Cu (In, Ga) (Se, S) ₂ (also referred to as CIGSS), and CuInS ₂ (CIS). Also called). Cu (In, Ga) Se ₂ refers to a compound mainly composed of Cu, In, Ga, and Se. Cu (In, Ga) (Se, S) ₂ refers to a compound mainly composed of Cu, In, Ga, Se, and S.

  The first semiconductor layer 3 further contains a silicon element and an oxygen element. As a result, the silicon element is uniformly incorporated into the I-III-VI group compound semiconductor in a state of being well bonded to the oxygen element. As a result, it is possible to fill the defects in the I-III-VI group compound semiconductor with the oxygen element while suppressing the oxidation of the raw material metal of the I-III-VI group compound semiconductor. It becomes a group VI compound semiconductor. As a result, the photoelectric conversion efficiency of the photoelectric conversion device 10 can be increased.

In the first semiconductor layer 3, the concentration of silicon element is preferably 5 to 40 at% and the concentration of oxygen element is preferably 5 to 60 at% from the viewpoint of increasing the photoelectric conversion efficiency. Furthermore, from the viewpoint of improving the adhesion with the first electrode layer 2, the concentration of silicon element is preferably 10 to 30 at%, and the concentration of oxygen element is preferably 30 to 60 at%. Such concentrations of silicon element and oxygen element are determined by energy dispersive X-ray analysis (EDS analysis) on any 10 or more points selected without any bias in the cross section of the first semiconductor layer 3. It can be measured by averaging the measured concentrations.

  Preferably, as shown in FIG. 3, the granular regions 9 containing the silicon element and the oxygen element at high concentrations are preferably scattered in the first semiconductor layer 3. Thereby, defects in the I-III-VI group compound semiconductor can be satisfactorily filled, and charge transfer in the I-III-VI group compound semiconductor is favorably performed. Note that the high concentration of silicon element and oxygen element means that the total concentration of silicon element and oxygen element in the granular region 9 is 4% higher than the total concentration of silicon element and oxygen element around the granular region 9. It is more than twice as expensive.

  The average particle size of the granular region 9 is preferably 5 to 100 nm from the viewpoint of improving charge transfer and supplying oxygen uniformly into the first semiconductor layer 3.

  Such a first semiconductor layer 3 is manufactured as follows. First, on the first electrode layer 2, a precursor layer containing the raw metal (IB group element and III-B group element) of the first semiconductor layer 3 is formed. The precursor layer is formed by forming a film by using a thin film forming method such as sputtering for the raw material metal, or by forming a film by applying a solution of an organic metal salt or organic metal complex containing the raw material metal. can do. These precursor layers may contain a chalcogen element.

  Then, the precursor layer is placed in a heating furnace, and the precursor layer is heated in an atmosphere containing the chalcogen element constituting the first semiconductor layer 3 in the heating furnace. At this time, by including silicon element and oxygen element in the atmosphere of the heating furnace, the raw material metal of the precursor layer is chalcogenized to form an I-III-VI group compound semiconductor, and at the same time, the silicon element and oxygen element are converted into this I It can be incorporated into a group III-VI compound semiconductor. The atmosphere containing a chalcogen element is an atmosphere containing a gas of a chalcogen element alone or a gas of a chalcogen compound such as a hydride of a chalcogen element.

  Examples of a method for containing silicon element and oxygen element in the atmosphere of the heating furnace include heating a compound containing silicon element and a compound containing oxygen element, or heating a compound containing both silicon element and oxygen element. Then, a decomposition substance generated by thermal decomposition may be mixed in an atmosphere containing the chalcogen element. As such a compound containing a silicon element, a compound containing an oxygen element, and a compound containing both a silicon element and an oxygen element, an organic compound, an inorganic compound, an organic-inorganic hybrid material, or the like is used. Then, by adjusting the thermal decomposition conditions of such a compound, specifically, the thermal decomposition temperature, heating temperature, heating rate, etc. of the compound, silicon element and oxygen element into the first semiconductor layer 3 are adjusted. The amount and state of mixing can be controlled.

  Preferably, a compound having a siloxane bond as a skeleton composed of silicon and oxygen is placed in the heating furnace and heated. Thereby, silicon and oxygen are taken into the first semiconductor layer 3 in a well-bonded state, and the oxidation of the raw material metal of the first semiconductor layer 3 can be satisfactorily suppressed.

As such a compound having a siloxane bond as a skeleton composed of silicon and oxygen, the thermal decomposition temperature is a crystallization temperature at the time of forming the I-III-VI group compound semiconductor constituting the first semiconductor layer 3 (for example, , 500-600 ° C.) is preferable to use silicone. Since silicone contains an organic substance, deterioration gradually proceeds even when the temperature is lower than the thermal decomposition temperature, and in particular, it becomes a granular state and silicon element and oxygen element are easily taken into the first semiconductor layer 3. .

  Alternatively, as another manufacturing method of the first semiconductor layer 3, a compound containing a silicon element, a compound containing an oxygen element in a solution such as an organometallic salt or organometallic complex containing a raw material metal of the first semiconductor layer 3, Alternatively, it can also be formed by mixing a compound containing both silicon element and oxygen element, coating it to form a film, and heat-treating it.

  Further, the silicon element and the oxygen element contained in the first semiconductor layer 3 also have an action of trapping the alkali metal element well. Therefore, when an alkali metal element is included in the precursor layer including the raw material of the first semiconductor layer 3 to promote crystallization, the alkali metal element is trapped well and the alkali metal element is crystallized during crystallization. Can be supplied satisfactorily. That is, the alkali metal element is easily diffused, so that it is difficult to remain in the first semiconductor layer 3 when crystallization progresses to some extent. Thus, the alkali metal element can be continuously supplied even after the crystallization progresses, and the crystallization can be further enhanced.

  The photoelectric conversion device 10 uses the first semiconductor layer 3 as a light absorption layer, and a second semiconductor layer 4 is formed on the first semiconductor layer 3 with a thickness of 10 to 200 nm. A second electrode layer 5 is formed on the layer 4. Note that the second electrode layer 5 may be formed on the first semiconductor layer 3 without forming the second semiconductor layer 4. Alternatively, the second semiconductor layer 4 can function as an electrode without forming the second electrode layer 5.

The second semiconductor layer 4 is a semiconductor layer that forms a heterojunction with the first semiconductor layer 3. The first semiconductor layer 3 and the second semiconductor layer 4 are preferably of different conductivity types. For example, when the first semiconductor layer 3 is a p-type semiconductor, the second semiconductor layer 4 is i-type or It is an n-type semiconductor. Preferably, from the viewpoint of reducing leakage current, the second semiconductor layer is a layer having a resistivity of 1 Ω · cm or more. Examples of the second semiconductor layer 4 include CdS, ZnS, ZnO, In ₂ Se ₃ , In (OH, S), (Zn, In) (Se, OH), and (Zn, Mg) O. For example, it is formed by a chemical bath deposition (CBD) method or the like. In (OH, S) refers to a compound mainly composed of In, OH, and S. (Zn, In) (Se, OH) refers to a compound mainly composed of Zn, In, Se, and OH. (Zn, Mg) O refers to a compound mainly composed of Zn, Mg and O. In order to increase the absorption efficiency of the first semiconductor layer 3, the second semiconductor layer 4 preferably has a light transmittance with respect to the wavelength region of light absorbed by the first semiconductor layer 3.

  The second electrode layer 5 is a 0.05 to 3.0 μm transparent conductive film such as ITO or ZnO. The second electrode layer 5 is formed by sputtering, vapor deposition, chemical vapor deposition (CVD), or the like. The second electrode layer 5 is a layer having a resistivity lower than that of the second semiconductor layer 4, and is for taking out charges generated in the first semiconductor layer 3. From the viewpoint of taking out charges well, it is preferable that the resistivity of the second electrode layer 5 is less than 1 Ω · cm and the sheet resistance is 50 Ω / □ or less. The second electrode layer 5 may be a semiconductor layer having a conductivity type different from that of the first semiconductor layer, and includes what is called a window layer.

  In order to increase the absorption efficiency of the first semiconductor layer 3, it is preferable that the second electrode layer 5 has optical transparency with respect to the absorbed light of the first semiconductor layer 3. The second electrode layer 5 has a thickness of 0.05 to 0.5 μm from the viewpoint of enhancing the light transmittance and at the same time enhancing the light reflection loss prevention effect and the light scattering effect and further transmitting the current generated by the photoelectric conversion. Thickness is preferred. From the viewpoint of preventing light reflection loss at the interface between the second electrode layer 5 and the second semiconductor layer 4, the refractive indexes of the second electrode layer 5 and the second semiconductor layer 4 are equal. preferable.

  The photoelectric conversion device 10 includes a plurality of photoelectric conversion cells 11 having a configuration in which the first and second semiconductor layers 3 and 4 are sandwiched between the first and second electrode layers 1 and 5 and are electrically connected to each other. It consists of In order to easily connect adjacent photoelectric converters 11 in series, as shown in FIG. 1 and FIG. 2, the photoelectric conversion cell 11 is connected to the first electrode layer 2 on the substrate 1 side of the first semiconductor layer 3. A third electrode layer 6 is provided so as to be spaced apart. The second electrode layer 5 and the third electrode layer 6 are electrically connected by the connection conductor 7 provided in the first semiconductor layer 3.

  The connection conductor 7 is made of a material having a lower electrical resistivity than the first and second semiconductor layers 3 and 4. Such a connection conductor 7 can be formed, for example, by forming a groove penetrating the first and second semiconductor layers 3 and 4 and forming a conductor in the groove. As such a conductor, for example, after forming a groove penetrating the first and second semiconductor layers 3, 4, the connection electrode 7 is formed by forming the upper electrode layer 5 also in this groove. Alternatively, the connection conductor 7 may be formed by filling the groove with a conductive paste (see FIG. 4). In FIG. 4, when the current collecting electrode 8 is formed of a conductive paste, the connecting conductor 7 is formed by filling the conductive paste in the grooves penetrating the first and second semiconductor layers 3 and 4. . Alternatively, it is possible to form the first and second semiconductor layers 3 and 4 by modifying a part of the first and second semiconductor layers 3 and 4 to lower the electric resistivity without forming the groove as described above.

  Moreover, as shown in FIGS. 1 and 2, the photoelectric conversion device 10 may have a collecting electrode 8 formed on the second electrode layer 5. The collecting electrode 8 is for reducing the electric resistance of the second electrode layer 5. For example, as shown in FIG. 1, the collector electrode 8 is formed in a linear shape from one end of the photoelectric conversion cell 11 to the connection conductor 7. Thereby, the current generated by the photoelectric conversion of the first semiconductor layer 3 is collected through the second electrode layer 5 to the current collecting electrode 8, and this current is collected to the adjacent photoelectric conversion cell 11 through the connection conductor 7. It can conduct well. Therefore, by providing the current collecting electrode 8, the current generated in the first semiconductor layer 3 can be efficiently taken out even if the second electrode layer 5 is thinned. As a result, power generation efficiency can be increased.

  The collector electrode 8 preferably has a width of 50 to 400 μm from the viewpoint of suppressing light from being blocked to the first semiconductor layer 3 and having good conductivity. The current collecting electrode 8 may have a plurality of branched portions.

  The collector electrode 8 can be formed, for example, by printing a metal paste in which a metal powder such as Ag is dispersed in a resin binder or the like in a pattern and curing it.

The photoelectric conversion device of the present invention was evaluated as follows. First, 1 mmol of Cu (CH ₃ CN) ₄ .PF ₆ as an organometallic complex of a group I-B element, 2 mmol of P (C ₆ H ₅ ) ₃ as a Lewis basic organic compound, and 10 ml of acetonitrile each. Dissolved. After confirming that these solutions were uniformly dissolved, the solution was stirred for 5 hours at room temperature with a magnetic stirrer to prepare a first complex solution 1 containing the first complex. On the other hand, a 4mmol the NaOCH _3, after the 4mmol the HSEC ₆ H ₅ as chalcogen element-containing organic compound, was dissolved in methanol 30 ml, the 0.7mmol and GaCl ₃ and InCl ₃ were dissolved 0.3 mmol. After confirming complete dissolution, the mixture was stirred with a magnetic stirrer at room temperature for 5 hours to prepare a second complex solution 2 containing a second complex. Next, the second complex solution 2 was added dropwise to the first complex solution 1 at a rate of 10 ml per minute. Thereby, it was confirmed that a white precipitate was generated during the dropping. After completion of the dropwise addition, the mixture was stirred for 1 hour at room temperature with a magnetic stirrer. In order to take out only this precipitate, the operation of separating the solvent with a centrifuge, dispersing it in 50 ml of methanol, and centrifuging it was repeated twice. As a result, it was confirmed that the residual amount of Na in the final product was 1 ppm or less. The precipitate was dried at room temperature in a vacuum to remove the solvent, and then the composition of the precipitate was analyzed by emission spectroscopic analysis (ICP). As a result, it was confirmed that the precipitate was a single source precursor containing triphenylphosphine, phenyl selenol, Cu, In and Ga. The molar ratio of Cu, In, Ga, and Se in the precipitate was 1.04: 0.77: 0.23: 4.05.

  Next, pyridine was added to the precipitate to prepare a solution having a precipitate content of 50% by mass, and then indium acetylacetonate and gallium acetylacetonate were added and dissolved as a third complex in the solution. A raw material solution was prepared such that the molar ratio of Cu, In, and Ga in the solution was 0.84: 0.62: 0.38.

  Next, a glass substrate having a first electrode layer made of Mo formed on the surface was prepared, and the raw material solution was applied by a blade method, and then dried at 200 ° C. to form a film.

  After a total of two coatings by this blade method, the sample substrate on which this film was formed was placed in a heating furnace and heat-treated in an atmosphere containing hydrogen gas and selenium vapor. At this time, a lump of silicone (product name: SR type manufactured by Tigers Polymer Co., Ltd.) was also placed in the heating furnace. The heat treatment was carried out by raising the temperature up to 560 ° C. at 12 ° C./min and then holding at 500 ° C. for 1 hour. This was naturally cooled to produce a first semiconductor layer made of CIGS having a thickness of 2 μm.

  Next, cadmium iodide and thiourea are dissolved in aqueous ammonia, and the substrate on which the first semiconductor layer is formed is immersed therein, and a second semiconductor layer made of CdS having a thickness of 50 nm is formed on the first semiconductor layer. Formed. Further, a transparent second electrode layer made of an Al-doped zinc oxide film was formed on the second semiconductor layer by a sputtering method. Finally, an aluminum electrode (extraction electrode) was formed by vapor deposition to produce a photoelectric conversion device as a sample.

  Moreover, the photoelectric conversion apparatus as a comparative example was produced by the same method as the photoelectric conversion apparatus as the sample except that the heat treatment was performed without placing the silicone in a heating furnace.

  About the photoelectric conversion apparatus as a sample produced as mentioned above and the photoelectric conversion apparatus as a comparative example, the cross section of the 1st semiconductor layer was observed by TEM. As a result, in the first semiconductor layer of the photoelectric conversion device as a sample, it was observed that granular regions having an average particle diameter of 60 nm were scattered with an average interval between the granular bodies of 500 nm. . On the other hand, such a granular region was not observed in the comparative example.

  Next, the cross section of the first semiconductor layer was analyzed by EDS. As a result, the first semiconductor layer of the photoelectric conversion device as a sample has a silicon element concentration of 3.1 at% and an oxygen element concentration of 7.27 at% in the remainder other than the granular region, whereas silicon in the granular region The element concentration was 17.4 at%, and the oxygen element concentration was as high as 42.6 at%. On the other hand, the first semiconductor layer of the photoelectric conversion device as a comparative example has no particularly high silicon element concentration and oxygen element concentration, and the silicon element concentration is 0.3 at% and the oxygen element concentration is 1.83 at%. It was.

And about these photoelectric conversion apparatuses, the photoelectric conversion efficiency was measured, respectively. In addition, about photoelectric conversion efficiency, what is called a stationary light solar simulator is used, and the irradiation intensity of the light with respect to the light-receiving surface of the photoelectric conversion apparatus 10 is 100 mW / cm < ² >, and AM (air mass) is 1.5. The conversion efficiency was measured.

  As a result of the measurement, the photoelectric conversion efficiency of the photoelectric conversion device as the comparative example was 11.65%, whereas the photoelectric conversion efficiency of the photoelectric conversion device as the sample was 12.89%, which is excellent. all right.

1: Substrate 2: First electrode layer 3: First semiconductor layer 4: Second semiconductor layer 5: Second electrode layer 6: Third electrode layer 7: Connection conductor 8: Current collecting electrode 9: Granularity Region 10: photoelectric conversion device

Claims (3)

  A photoelectric conversion device comprising: a semiconductor layer containing a silicon element and an oxygen element as a main component of a group I-III-VI compound semiconductor in which a group VI element is a chalcogen element.   The photoelectric conversion device according to claim 1, wherein granular regions containing the silicon element and the oxygen element at high concentrations are scattered in the semiconductor layer. It is a manufacturing method of the photoelectric conversion device according to claim 1 or 2,
Producing a precursor layer comprising a group I element and a group III element;
Placing the precursor layer and silicone in a firing furnace, and producing the semiconductor layer by heating the precursor layer and the silicone while introducing a gas containing a chalcogen element into the firing furnace. A method for manufacturing a photoelectric conversion device.

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