JP2015008218A - Photoelectric conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance photoelectric conversion efficiency of a photoelectric conversion device.SOLUTION: A photoelectric conversion device 11 comprises: an electrode layer 2 containing Mo; an intermediate layer 3 located on the electrode layer 2 and containing MoO; a first semiconductor layer 4 located on the intermediate layer 3 and containing a metal chalcogenide; and a second semiconductor layer 5 located on the first semiconductor layer 4 and having a conductivity type different from that of the first semiconductor layer 4.

Description

  The present invention relates to a photoelectric conversion device using a semiconductor layer containing a metal chalcogenide.

As a photoelectric conversion device such as a solar cell, there is one using a metal chalcogenide such as an I-III-VI group compound as a light absorption layer. In this photoelectric conversion device, for example, an electrode layer made of Mo is formed on a substrate made of soda lime glass, and a light absorption layer is formed on the electrode layer. Further, a transparent transparent conductive film made of ZnO, ITO or the like is formed on the light absorption layer through a buffer layer containing ZnS, CdS, In ₂ S ₃ or the like.

Japanese Patent Laid-Open No. 08-330614

  The photoelectric conversion device is desired to further improve the photoelectric conversion efficiency. Therefore, an object of the present invention is to increase the photoelectric conversion efficiency of the photoelectric conversion device.

A photoelectric conversion device according to one embodiment of the present invention includes an electrode layer including Mo, an intermediate layer including MoO ₃ positioned on the electrode layer, and a first semiconductor layer including a metal chalcogenide positioned on the intermediate layer And a second semiconductor layer having a conductivity type different from that of the first semiconductor layer located on the first semiconductor layer.

  ADVANTAGE OF THE INVENTION According to this invention, the photoelectric conversion efficiency of a photoelectric conversion apparatus can be improved.

It is a perspective view which shows an example of embodiment of a photoelectric conversion apparatus. It is sectional drawing of the photoelectric conversion apparatus of FIG.

<(1) Configuration of photoelectric conversion device>
FIG. 1 is a perspective view showing an example of a photoelectric conversion apparatus according to an embodiment of the present invention. 2 is an XZ sectional view of the photoelectric conversion device of FIG. 1 to 2 are provided with a right-handed XYZ coordinate system in which the arrangement direction of photoelectric conversion cells 10 (the horizontal direction in the drawing in FIG. 1) is the X-axis direction.

  The photoelectric conversion device 11 has a configuration in which a plurality of photoelectric conversion cells 10 are arranged in parallel on a substrate 1. In FIG. 1, only two photoelectric conversion cells 10 are shown for convenience of illustration, but an actual photoelectric conversion device 11 has a large number of photoelectric conversion cells in the X-axis direction of the drawing or further in the Y-axis direction of the drawing. The conversion cells 10 are arranged two-dimensionally (two-dimensionally).

  Each photoelectric conversion cell 10 mainly includes a lower electrode layer 2, an intermediate layer 3, a first semiconductor layer 4, a second semiconductor layer 5, an upper electrode layer 6, and a collecting electrode 7. In the photoelectric conversion device 11, the main surface on the side where the upper electrode layer 6 and the collecting electrode 7 are provided is a light receiving surface.

  The substrate 1 supports the plurality of photoelectric conversion cells 10 and is made of, for example, a material such as glass, ceramics, resin, or metal. As a specific example, for example, a blue plate glass (soda lime glass) having a thickness of about 1 to 3 mm may be used as the substrate 1.

  The lower electrode layer 2 is a conductive layer provided on one main surface of the substrate 1 and contains molybdenum (Mo). From the viewpoint of enhancing the electrical connection between the first semiconductor layer 4 and the lower electrode layer 2, the concentration of Mo in the lower electrode layer 2 may be 70 to 100 mol%. The lower electrode layer 2 has a thickness of about 0.1 to 1 μm. The lower electrode layer 2 can be formed by a known thin film forming method such as sputtering or vapor deposition.

  The first semiconductor layer 4 is a semiconductor layer that absorbs light and performs photoelectric conversion, and functions as a light absorption layer. The first semiconductor layer 4 has the first conductivity type (here, p-type conductivity type), and is, for example, about 1 to 3 μm on the + Z side main surface 2a of the lower electrode layer 2. Thickness is provided. The first semiconductor layer 4 may be a semiconductor containing metal chalcogenide.

  A metal chalcogenide is a compound of a metal element and a chalcogen element. The chalcogen element refers to sulfur (S), selenium (Se), and tellurium (Te) among group 16 elements (also referred to as group VI-B elements). Metal chalcogenides include group 11 elements (also referred to as group IB elements), group 13 elements (also referred to as group III-B elements) and group 16 elements, group III-VI compounds, group 11 elements. I-II-IV-VI group compounds and 12-group elements and 16-group elements (also referred to as II-B group elements), 14-group elements (also referred to as IV-B group elements) and 16-group elements II-VI group compounds that are compounds with group elements can be employed.

Examples of the I-III-VI group compound include CuInSe ₂ (indium diselenide,
CIS), Cu (In, Ga) Se ₂ (also called copper indium gallium selenide, CIGS), Cu (In, Ga) (Se, S) ₂ (diselen copper indium gallium indium gallium, CIGSS). Alternatively, the first semiconductor layer 4 may be formed of a multi-component compound semiconductor thin film such as copper indium selenide / gallium having a thin film of selenite / copper indium sulfide / gallium as a surface layer.

Examples of the I-II-IV-VI group compound include Cu ₂ ZnSnS ₄ (also referred to as CZTS), Cu ₂ ZnSn (S, Se) ₄ (also referred to as CZTSSe), and Cu ₂ ZnSnSe ₄ (also referred to as CZTSe). Can be mentioned. Moreover, as a II-VI group compound, CdTe etc. are mentioned, for example.

  The first semiconductor layer 4 can be formed by a so-called vacuum process such as a sputtering method or a vapor deposition method, or can be formed by a process called a coating method or a printing method. A process referred to as a coating method or a printing method is a process in which a complex solution of constituent elements of the first semiconductor layer 4 is applied on the lower electrode layer 2 and then dried and heat-treated.

The intermediate layer 3 is a semiconductor layer containing molybdenum oxide (VI) (MoO ₃ ), and is located at the interface between the lower electrode layer 2 and the first semiconductor layer 4. With such a configuration, a band mismatch of the conduction band between the first semiconductor layer 4 and the intermediate layer 3 is formed. As a result, the recombination of carriers at the surface portion of the first semiconductor layer 4 on the lower electrode layer 2 side is effectively reduced, and the photoelectric conversion efficiency of the photoelectric conversion device 11 is improved.

Mo contained in the lower electrode 2 tends to generate MoO _{2 due} to natural oxidation, but this MoO ₂ hardly functions as a semiconductor for forming the band mismatch as described above. Intermediate layer 3 containing MoO _3, the lower electrode layer 2, for example in an atmosphere containing oxygen atmosphere such as, by heating in 150 to 500 ° C., to chemically changing the surface of the lower electrode layer 2 to MoO ₃ Can be produced. MoO ₃ can be analyzed using, for example, X-ray photoelectron spectroscopy (XPS).

From the viewpoint of better conduction of carriers from the first semiconductor layer 4 to the lower electrode layer 2 through the intermediate layer 3, the first semiconductor layer 4 contains 70 to 100 mol% of metal chalcogenide and the intermediate layer 3 the MoO ₃ may contain 70~100mol%.

  The thickness of the intermediate layer 3 may be 1 to 30 nm, for example. With such a configuration, charge transfer between the first semiconductor layer 4 and the lower electrode layer 2 is favorably performed, and the photoelectric conversion efficiency of the photoelectric conversion device 11 is further improved.

  Further, the first semiconductor layer 4 may further contain oxygen from the viewpoint of enhancing the bonding property with the intermediate layer 3. The oxygen concentration in the first semiconductor layer 4 may be, for example, 0.01 to 1 atomic%. The oxygen concentration in the first semiconductor layer 4 can be measured using, for example, secondary ion mass spectrometry (SIMS).

  The second semiconductor layer 5 is a semiconductor layer having a second conductivity type (here, n-type conductivity type) different from that of the first conductivity type first semiconductor layer 4, and the first semiconductor layer 4 And are electrically connected. The first conductivity type and the second conductivity type refer to one and the other of p-type and n-type. If the first conductivity type is p-type, the second conductivity type is n-type. If the first conductivity type is n-type, the second conductivity type is p-type. Charge separation of positive and negative carriers generated by light irradiation in the first semiconductor layer 4 and the second semiconductor layer 5 can be performed satisfactorily.

  From the viewpoint of reducing the leakage current, the second semiconductor layer 5 may have a resistivity of 1 Ω · cm or more. The second semiconductor layer 5 has a thickness in the normal direction of one main surface of the first semiconductor layer 4. This thickness is set to, for example, 5 to 200 nm. The second semiconductor layer 5 may be a plurality of layers.

Examples of the second semiconductor layer 5 include CdS, ZnS, ZnO, In ₂ Se ₃ , In (OH, S), (Zn, In) (Se, OH), and (Zn, Mg) O. The second semiconductor layer 5 is formed by, for example, a chemical bath deposition (CBD) method or the like. Note that In (OH, S) refers to a compound containing In, OH, and S as main components. (Zn, In) (Se, OH) refers to a compound containing Zn, In, Se, and OH as main components. (Zn, Mg) O refers to a compound containing Zn, Mg, and O as main components. In order to increase the absorption efficiency of the first semiconductor layer 4, the second semiconductor layer 5 may have a high light transmittance with respect to the wavelength region of light absorbed by the first semiconductor layer 4. The thickness of the second semiconductor layer 5 is, for example, 5 to 200 nm.

  The upper electrode layer 6 is a transparent conductive film provided on the second semiconductor layer 5, and is an electrode that extracts charges generated in the first semiconductor layer 4. The upper electrode layer 6 is made of a material having a lower resistivity than the second semiconductor layer 5. The upper electrode layer 6 includes what is called a window layer. When a transparent conductive film is further provided in addition to the window layer, these may be regarded as an integrated upper electrode layer 6.

The upper electrode layer 6 mainly includes a material having a wide forbidden band, transparent, and low resistance. As such a material, for example, a metal oxide semiconductor such as ZnO, In ₂ O ₃ and SnO ₂ can be adopted. These metal oxide semiconductors may contain any element of Al, B, Ga, In, F, and the like. Specific examples of the metal oxide semiconductor containing such an element include, for example, AZO (Aluminum Zinc Oxide), GZO (Gallium Zinc Oxide),
Examples include IZO (Indium Zinc Oxide), ITO (Indium Tin Oxide), and FTO (Fluorine tin Oxide).

  The upper electrode layer 6 is formed to have a thickness of 0.05 to 3 μm, for example. Here, from the viewpoint of good charge extraction from the first semiconductor layer 4, the upper electrode layer 6 has a resistivity of less than 1 Ω · cm and a sheet resistance of 50Ω / □ or less. Can do.

  The upper electrode layer 6 can be formed by sputtering, vapor deposition, chemical vapor deposition (CVD), or the like.

  A collecting electrode 7 may be provided on the upper electrode layer 6. The collecting electrodes 7 are spaced apart in the Y-axis direction, and each extend in the X-axis direction. The current collecting electrode 7 is a conductive electrode, and includes, for example, a metal such as silver (Ag).

  The collecting electrode 7 plays a role of collecting charges generated in the first semiconductor layer 4 and taken out in the upper electrode layer 6. If the current collecting electrode 7 is provided, the upper electrode layer 6 can be thinned.

  The electric charges collected by the collector electrode 7 and the upper electrode layer 6 are adjacent to each other through the connection conductor 8 provided in the groove P2 that divides the first semiconductor layer 4, the second semiconductor layer 5, and the upper electrode layer 6. Is transmitted to the photoelectric conversion cell 10. For example, as shown in FIG. 2, the connection conductor 8 is constituted by a portion extending in the Y axis direction of the current collecting electrode 7. Thereby, in the photoelectric conversion apparatus 11, one lower electrode layer 2 of the adjacent photoelectric conversion cell 10 and the other collector electrode 7 are electrically connected in series via the connection conductor 8 provided in the groove portion P2. It is connected to the. In addition, the connection conductor 8 is not limited to this, You may be comprised by the extension part of the upper electrode layer 6. FIG.

  The current collecting electrode 8 has a width of 50 to 400 μm so that good conductivity is ensured and a decrease in the light receiving area that affects the amount of light incident on the first semiconductor layer 4 is minimized. Can be.

  The present invention is not limited to the above-described embodiment, and various changes and improvements can be made without departing from the scope of the present invention.

1: Substrate 2: Lower electrode layer 3: Intermediate layer 4: First semiconductor layer 5: Second semiconductor layer 6: Upper electrode layer 7: Current collecting electrode 8: Connection conductor 10: Photoelectric conversion cell 11: Photoelectric conversion device

Claims (3)

An electrode layer containing Mo;
An intermediate layer comprising MoO ₃ located on the electrode layer;
A first semiconductor layer comprising a metal chalcogenide located on the intermediate layer;
A photoelectric conversion device comprising: a second semiconductor layer having a conductivity type different from that of the first semiconductor layer located on the first semiconductor layer.   The photoelectric conversion device according to claim 1, wherein the first semiconductor layer further contains oxygen.   The photoelectric conversion device according to claim 1, wherein the intermediate layer has a thickness of 1 to 30 nm.

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