JP2014194878A - Photoelectric conversion element, and solar battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel photoelectric conversion element which is improved in durability by use of a novel oxide semiconductor.SOLUTION: A photoelectric conversion element comprises: a transparent substrate; a first electrode provided on the transparent substrate; an oxide semiconductor layer provided on the first electrode; a second electrode provided to be opposed to the oxide semiconductor layer; and an electrolyte which is sealed in between the first electrode and the second electrode. The oxide semiconductor layer includes a complex oxide of a perovskite structure including bismuth and iron.

Description

  The present invention relates to a photoelectric conversion element using an oxide semiconductor and a solar cell.

  DESCRIPTION OF RELATED ART Conventionally, the dye-sensitized solar cell which uses the oxide semiconductor which adsorb | sucked the pigment | dye as an electrode is known (refer patent documents 1-3). Such a solar cell is composed of a solar cell formed by arranging a cathode electrode and an anode electrode so as to face each other at a predetermined interval through a side wall, and an electrolyte sealed inside the solar cell, and the cathode electrode Is made of conductive glass or the like, and the anode electrode is made of a conductive substrate made of conductive glass or the like, and an oxide semiconductor electrode formed on the electrolyte side surface of the substrate. The oxide semiconductor electrode constituting the anode electrode is composed of a porous layer on which a large number of oxide semiconductor fine particles (oxide semiconductor electrode material) having a dye adsorbed on the surface are deposited.

Japanese Patent No. 2664194 JP-A-6-163966 JP-A-9-259943

In the dye-sensitized solar cell described above, anatase-type titanium oxide (TiO ₂ ) fine particles are generally used as the oxide semiconductor fine particles, but TiO ₂ does not absorb visible light, and therefore absorbs visible light. A sensitizing dye is used as a function. However, there is a problem that a sensitizing dye that is an organic substance is deteriorated by light, and the life of the dye-sensitized solar cell is insufficient.
This invention is made | formed in view of the said condition, and it aims at providing the novel photoelectric conversion element and solar cell which improved durability using the novel oxide semiconductor.

An aspect of the present invention that solves the above problems includes a transparent substrate, a first electrode provided on the transparent substrate, an oxide semiconductor layer provided on the first electrode, and the oxide semiconductor layer. And an electrolyte sealed between the first electrode and the second electrode, and the oxide semiconductor layer is made of a complex oxide having a perovskite structure containing bismuth and iron. It is in the photoelectric conversion element characterized by this.
In such an embodiment, an oxide semiconductor layer containing a composite oxide having a perovskite structure containing bismuth and iron as a component absorbs visible light, operates in the same manner as dye-sensitized titanium oxide, and generates power. Since it does not need to be used, it has durability.

  Here, the oxide semiconductor layer preferably contains a composite oxide having a perovskite structure containing bismuth and iron as a main component. According to this, more efficient power generation becomes possible.

  Moreover, it is preferable that the said complex oxide contains manganese further. According to this, more efficient power generation becomes possible.

  The composite oxide preferably further contains a lanthanoid element. According to this, more efficient power generation becomes possible.

  The composite oxide preferably further contains titanium. According to this, more efficient power generation becomes possible.

Moreover, the other aspect of this invention exists in the solar cell using the photoelectric conversion element of the said aspect.
In such an embodiment, an oxide semiconductor layer containing a composite oxide having a perovskite structure containing bismuth and iron as a component absorbs visible light, operates in the same manner as dye-sensitized titanium oxide, and generates power. Since it does not need to be used, it has durability.

It is a figure which shows schematic structure of the photoelectric conversion element which concerns on embodiment of this invention. It is a figure which shows the ultraviolet-visible light absorption spectrum of the oxide semiconductor layer of embodiment.

  Hereinafter, the present invention will be described in detail based on embodiments. Such an embodiment shows one aspect of the present invention, and is not intended to limit the present invention, and can be arbitrarily changed within the scope of the present invention.

FIG. 1 is a diagram illustrating a schematic configuration of a photoelectric conversion element according to an embodiment of the present invention.
As shown in FIG. 1, the photoelectric conversion element 10 includes a first electrode 12 and an oxide semiconductor layer 13 provided on the first electrode 12 on a transparent substrate 11. Comprises a second electrode 15. The transparent substrate 11 and the counter substrate 14 are arranged to face each other, and the electrolyte 16 is sealed between the oxide semiconductor layer 13 and the second electrode 15 via the sealing member 17.

Here, the transparent substrate 11 is not particularly limited as long as it is a substrate having transparency that transmits at least visible light. For example, a glass substrate such as quartz or soda-lime glass can be used. The first electrode 12 is translucent and uses various transparent electrodes such as a transparent electrode (ITO) made of indium tin oxide, a zinc oxide-based transparent electrode, lanthanum nickelate (LNO), and the like. Can do.
The oxide semiconductor layer 13 is made of a complex oxide having a perovskite structure containing bismuth and iron.

  A typical example is a bismuth ferrate-based composite oxide having a perovskite structure. In such a complex oxide having a perovskite structure, oxygen is 12-coordinated at the A site, and oxygen is 6-coordinated at the B site to form an octahedron. Bismuth (Bi) is located at the A site and iron (Fe) is located at the B site. However, Bi at the A site and part of Fe at the B site may be substituted with various elements. Examples of the element substituting Bi at the A site include a lanthanoid element and barium (Ba). Examples of the lanthanoid element include lanthanum (La), samarium (Sm), and cerium (Ce). it can. Examples of the element that substitutes Fe at the B site include manganese (Mn), aluminum (Al), cobalt (Co), and titanium (Ti).

Specifically, bismuth ferrate (BiFeO ₃ ), bismuth ferrate aluminate (Bi (Fe, Al) O ₃ ), bismuth ferrate manganate (Bi (Fe, Mn) O ₃ ), bismuth ferrate manganate Lanthanum ((Bi, La) (Fe, Mn) O ₃ ), bismuth barium titanate manganate ((Bi, Ba) (Fe, Mn, Ti) O ₃ ), bismuth ferrate cobaltate (Bi (Fe , Co) O ₃ ), bismuth cerium ferrate ((Bi, Ce) FeO ₃ ), bismuth cerium ferrate manganate ((Bi, Ce) (Fe, Mn) O ₃ ), bismuth lanthanum cerium ferrate ((Bi , La, Ce) FeO ₃ ), bismuth lanthanum cerium ferrate manganate ((Bi, La, Ce) (Fe, Mn) O ₃ ), bismuth samarium ferrate ((Bi, Sm) FeO ₃ ), Bismuth barium titanate manganate ((Bi, Ba) (Fe, Mn, Ti) O ₃ ), bismuth ferrate chromate (Bi (Cr, Fe) O ₃ ), bismuth ferrate manganate titanate Examples include potassium ((Bi, K) (Fe, Mn, Ti) O ₃ ) and the like.

In addition, the oxide semiconductor layer 13 of the present invention includes, for example, Bi (Zn, Ti) O ₃ , (Bi, K) TiO ₃ , (Bi, Na) TiO ₃ , (Li, Na) in the composite oxide described above. , K) (Ta, Nb) O ₃ may be added.

  The counter substrate 14 can be provided with the second electrode 15 and is not particularly limited as long as it has mechanical strength for sealing the electrolyte 16; however, a glass substrate, a silicon substrate, a plastic substrate, or the like can be used.

  Since the oxide semiconductor layer 13 absorbs light in the ultraviolet-visible region, it is not necessary to use a sensitizing dye. In addition, since the oxide semiconductor layer 13 is substantially transparent, the oxide semiconductor layer 13 as a whole absorbs ultraviolet to visible light, so that the efficiency is further improved.

The 2nd electrode 15 does not need to be transparent, and should just have electroconductivity, for example, can use a platinum electrode.
As the electrolyte 16, for example, an electrolyte used in a conventional dye-sensitized photoelectric conversion element can be used, and examples thereof include an iodine-based electrolyte solution, a bromine-based electrolyte solution, and a cobalt complex-based electrolyte solution.
The sealing member 17 is not particularly limited as long as it joins the transparent substrate 11 and the counter substrate 14 and seals the electrolyte 16.

When such a photoelectric conversion element 10 is irradiated with light from the transparent substrate 11 side, for example, Fe in the oxide semiconductor layer 13 is oxidized from Fe ²⁺ to Fe ³⁺ as represented by the following formula, and electrons are the first electrode. 12 flows. Further, Fe ^{3+ that} has lost electrons is reduced by taking electrons from, for example, iodine in the electrolyte 16 and returns to Fe ²⁺ , and iodine that has lost electrons receives electrons from the second electrode 15 serving as the positive electrode and returns to the source. . By this series of reactions, electrons flow from the first electrode 12 to the second electrode 15 and current is obtained.

Fe ²⁺ + light → Fe ³⁺ + e ⁻

(Test Example 1)
A BiFeO ₃ film was formed on a synthetic quartz substrate by spin coating.
First, a BiFeO ₃ raw material solution prepared by mixing a bismuth 2-ethylhexanoate and an n-octane solution of iron 2-ethylhexanoate so as to have a composition of Bi / Fe = 100/100 was prepared. Then, the raw material solution was dropped on the synthetic quartz substrate, and the substrate was rotated at 2000 rpm to form a BiFeO ₃ precursor film. Next, it was dried at 180 ° C. for 2 minutes. Subsequently, degreasing was performed at 350 ° C. for 2 minutes. Next, baking was performed at 650 ° C. for 5 minutes in a nitrogen atmosphere using a RTA (Rapid Thermal Annealing) apparatus.

On the other hand, as a comparison, a titanium oxide precursor solution consisting of an n-octane solution of titanium 2-ethylhexanoate was similarly spin-coated on a synthetic quartz substrate and baked at 750 ° C. in an oxygen atmosphere. Used a similar process to form a titanium oxide film.
About these, the result of having measured the ultraviolet-visible absorption spectrum is shown in FIG.

As a result, it was confirmed that the titanium oxide film only absorbs light of 360 nm or less, whereas the BiFeO ₃ film absorbs light of wavelength 360 nm or more and 500 nm or less.

(Test Example 2)
First, a silicon oxide (SiO ₂ ) film having a thickness of 1070 nm was formed on the surface of a (110) single crystal silicon (Si) substrate by thermal oxidation. Next, a titanium film with a thickness of 20 nm was formed on the SiO ₂ film by RF magnetron sputtering, and a titanium oxide film with a thickness of 40 nm was formed by thermal oxidation at 700 ° C. Next, a platinum film having a thickness of 130 nm oriented on the (111) plane was formed on the titanium oxide film by DC sputtering.

Next, a (Bi, La) (Fe, Mn, Ti) O ₃ film was formed on the platinum film by spin coating. The method is as follows.
First, n-octane solution of bismuth 2-ethylhexanoate, lanthanum 2-ethylhexanoate, iron 2-ethylhexanoate, manganese 2-ethylhexanoate, titanium 2-ethylhexanoate was mixed, and Bi / La / Fe A raw material solution prepared to have a composition of / Mn / Ti = 85/15/92/1/7 was prepared. The raw material solution was dropped on the substrate on which the titanium oxide film and the platinum film were formed, and the substrate was rotated at 2000 rpm to form a (Bi, La) (Fe, Mn, Ti) O ₃ precursor film. (Application process). Next, it was dried at 180 ° C. for 2 minutes (drying step). Next, degreasing was performed at 350 ° C. for 2 minutes (degreasing step). Subsequently, after repeating the process which consists of said application | coating process, a drying process, and a degreasing process 4 times, baking was performed at 650 degreeC for 5 minute (s) with the RTA apparatus in nitrogen atmosphere (baking process).

Thereafter, a circular platinum pattern having a diameter of 540 μm and a thickness of 100 nm was formed on the (Bi, La) (Fe, Mn, Ti) O ₃ film by sputtering, and then using an RTA apparatus in a nitrogen atmosphere. By baking at 650 ° C. for 5 minutes, a photoelectric conversion element having a (Bi, La) (Fe, Mn, Ti) O ₃ film having a thickness of 140 nm was formed.

  When turned on / off by irradiating a fluorescent lamp from between the platinum patterns, a current of 10 pA flows at the time of ON against a dark current of 1 pA at the time of OFF, and it was confirmed that the photoelectric conversion element is sensitive to light.

Example 1
A first electrode 12 made of LNO was provided on a transparent substrate 11 made of synthetic quartz. The LNO electrode was produced by a solution method. The method is as follows.
First, a raw material solution was prepared by preparing an acetic acid solution of lanthanum acetate and nickel acetate. Then, the raw material solution was dropped on the synthetic quartz substrate, and the substrate was rotated at 1500 rpm to form an LNO precursor film (coating process). Next, it was dried at 180 ° C. for 2 minutes (drying step). Next, degreasing was performed at 350 ° C. for 2 minutes (degreasing step). Next, firing was performed at 650 ° C. for 5 minutes in an oxygen atmosphere using an RTA apparatus (firing step). The process consisting of the coating process, the drying process, the degreasing process and the firing process was repeated twice.

Next, on the LNO electrode, a (Bi, La) (Fe, Mn) O ₃ film having a composition of Bi / La / Fe / Mn = 85/15/92/8 is formed by the same method as in Test Example 1. An oxide semiconductor layer 13 was formed.
Next, a sealing member 17 was attached on the (Bi, La) (Fe, Mn) O ₃ film and filled with an electrolyte 16 made of an aqueous solution of silver iodide.

Furthermore, the opposing substrate 14 made of Si, on which a platinum film was formed as the second electrode 15 on the surface, was bonded to produce the photoelectric conversion element 10.
When the produced photoelectric conversion element 10 was irradiated with a fluorescent lamp (0.04 mW / cm ^{2 at a} wavelength of 420 nm), an electromotive force of 16 mV and 6 μA / cm ² was confirmed.

  Since the photoelectric conversion element of the present invention does not use an organic dye as compared with a conventional dye-sensitized photoelectric conversion element, the photoelectric conversion element is excellent in durability and applicable to applications requiring durability.

  DESCRIPTION OF SYMBOLS 10 Photoelectric conversion element, 11 Transparent substrate, 12 1st electrode, 13 Oxide semiconductor layer, 14 Opposite substrate, 15 2nd electrode, 16 Electrolyte, 17 Sealing member

Claims (6)

  A transparent substrate; a first electrode provided on the transparent substrate; an oxide semiconductor layer provided on the first electrode; a second electrode provided opposite to the oxide semiconductor layer; A photoelectric conversion element comprising: an electrolyte enclosed between one electrode and the second electrode, wherein the oxide semiconductor layer includes a complex oxide having a perovskite structure including bismuth and iron.   2. The photoelectric conversion element according to claim 1, wherein the oxide semiconductor layer contains a composite oxide having a perovskite structure containing bismuth and iron as a main component.   The photoelectric conversion element according to claim 1, wherein the composite oxide further contains manganese.   The photoelectric conversion element according to claim 1, wherein the composite oxide further contains a lanthanoid element.   The photoelectric conversion element according to claim 1, wherein the composite oxide further contains titanium.   The solar cell using the photoelectric conversion element as described in any one of Claims 1-5.

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