JP4461657B2 - Photoelectric conversion element - Google Patents

Description

【０３３７】
表１に示す結果から、短絡防止手段（バリヤ層またはスペーサ）を有する太陽電池（実施例１〜５）では、ＦＴＯ電極とＣｕＩ層との間での接触等による短絡が好適に防止または抑制され、光電変換効率に優れるものであった。
【０３３８】
これに対し、バリヤ層（短絡防止手段）を省略した比較例の太陽電池では、光電変換効率に劣るものであった。
【０３３９】
比較例において光電変換効率が劣るのは、評価１の結果からも明らかなように、ＦＴＯ電極とＣｕＩ層との間での短絡（接触）による漏れ電流の発生が原因であると考えられる。
【０３４０】
また、実施例１〜５の太陽電池は、いずれも、Ｒ₅₂／Ｒ₉₀が０．８５以上であり、このことは、実施例１〜５の太陽電池が、光に対する指向性がより低いことを示すものであった。
【０３４１】
【発明の効果】
以上述べたように、本発明によれば、短絡防止手段を設けたことにより、第１の電極と正孔輸送層との間での接触等による短絡を好適に防止または抑制しつつ、効率よく電子を発生することができ、その結果、極めて優れた光電変換効率が得られる。
【０３４２】
受光層材料の粉末を含有するゾル液を用いるゾル・ゲル法を用いることにより、受光層をより容易かつ確実に形成することができる。
【０３４３】
また、短絡防止手段としてバリヤ層を設ける場合には、ＭＯＤ法を用いることにより、バリヤ層をより容易かつ確実に形成することができる。
また、本発明の光電変換素子は、製造が容易であり、安価に製造できる。
【図面の簡単な説明】
【図１】 本発明の光電変換素子を太陽電池に適用した場合の第１実施形態を示す部分断面図である。
【図２】 第１実施形態の太陽電池の厚さ方向の中央部付近の断面を示す拡大図である。
【図３】 受光層の断面を示す部分拡大図である。
【図４】 図１に示す太陽電池回路の等価回路を示す図である。
【図５】 第１実施形態の太陽電池の他の製造方法を説明するための図（受光層と正孔輸送層とを接合する前の状態を示す拡大断面図）である。
【図６】 第２実施形態の太陽電池の構成を示す断面図である。
【図７】 第２実施形態の太陽電池の製造方法を説明するための図（受光層と正孔輸送層とを接合する前の状態を示す拡大断面図）である。
【符号の説明】
１Ａ、１Ｂ……太陽電池 ２……基板 ３……第１の電極 ４……受光層 ４１……孔 ５……正孔輸送層 ５１……凸部 ６……第２の電極 ７……スペーサ ８……バリヤ層 １１Ａ……積層体 １２Ａ……積層体 １１Ｂ……積層体１２Ｂ……積層体 １００……外部回路 ２００……ダイオード[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a photoelectric conversion element.
[0002]
[Prior art]
Conventionally, solar cells (photoelectric conversion elements) using silicon have attracted attention as environmentally friendly power sources. Among solar cells using silicon, there are single crystal silicon type solar cells used for artificial satellites and the like. However, as practical ones, especially solar cells using polycrystalline silicon and amorphous silicon are used. Practical use of solar cells for industrial use and home use has begun.
[0003]
However, all of these solar cells using silicon are expensive to manufacture and require a large amount of energy for manufacturing, and are not necessarily energy-saving power sources.
[0004]
In addition, dye-sensitized wet solar cells such as those disclosed in JP-A-01-220380, JP-A-05-504023 and JP-A-06-511113 use an electrolyte solution having a high vapor pressure. There was a problem that the electrolyte solution volatilized.
[0005]
In order to compensate for these drawbacks, the announcement of fully solid dye-sensitized solar cells (K. Tennakone, GRRA Kumara, IRM Kottegoda, KGU Wijiayantha, and VPS Perera: J. Phys. D: Appl. Phys. 31 (1998) 1492). This solar cell is made of TiO₂An electrode in which layers are laminated, and TiO₂And a p-type semiconductor layer provided on the layer. However, such a solar cell has a p-type semiconductor layer of TiO₂There was a drawback that it penetrated the layer and shorted with the electrode.
[0006]
In this announcement, CuI is used as a constituent material of the p-type semiconductor layer. This solar cell using CuI has a problem that the generated current decreases due to deterioration due to an increase in CuI crystal grains.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a solid-state dye-sensitized photoelectric conversion element that can be manufactured at low cost and has excellent photoelectric conversion efficiency.
[0008]
[Means for Solving the Problems]
  Such purposes are as follows (1) to (19This is achieved by the present invention.
[0009]
  (1) a first electrode;
  A second electrode disposed opposite the first electrode;
  A light-receiving layer located between the first electrode and the second electrode, at least a portion of which is porous;
  A hole transport layer located between the light receiving layer and the second electrode;
  A photoelectric conversion element in which a rectifying barrier is formed at an interface between the light receiving layer and the hole transport layer,
  As a short-circuit prevention means for preventing or suppressing a short circuit between the first electrode and the hole transport layer, electrical conductivity equivalent to that of the light receiving layer is provided between the first electrode and the light receiving layer. Having a barrier layer having a porosity of 2% or less,
  The thickness ratio between the barrier layer and the light receiving layer is 1:99 to 40:60, and the barrier layer has a porosity smaller than the porosity of the light receiving layer. When the porosity of the layer is A [%] and the porosity of the light receiving layer is B [%], B / A is 10 or more,
  The barrier layer is mainly composed of titanium oxide formed by a sol-gel method using a barrier layer material containing titanium alkoxide,
  The light-receiving layer is mainly composed of titanium oxide formed by a sol-gel method using a light-receiving layer material containing titanium alkoxide and titanium oxide powder.And
The hole transport layer is mainly composed of a metal iodide compound which is a substance having ion conduction characteristics, and a hole transport layer material containing the substance having ion conduction characteristics is applied onto the dye layer by a coating method. Formed by coating,
The hole transport layer material contains thiocyanate as a crystal size coarsening inhibitor having a function of suppressing an increase in crystal size when the metal iodide compound is crystallized.The photoelectric conversion element characterized by the above-mentioned.
(2) The crystal size coarsening-suppressing substance binds to a metal atom of the metal iodide compound to suppress an increase in crystal size when the metal iodide compound is crystallized (1) ).
  (3)A first electrode;
A second electrode disposed opposite the first electrode;
A light-receiving layer located between the first electrode and the second electrode, at least a portion of which is porous;
A hole transport layer located between the light receiving layer and the second electrode;
A photoelectric conversion element in which a rectifying barrier is formed at an interface between the light receiving layer and the hole transport layer,
As a short-circuit prevention means for preventing or suppressing a short circuit between the first electrode and the hole transport layer, electrical conductivity equivalent to that of the light receiving layer is provided between the first electrode and the light receiving layer. Having a barrier layer having a porosity of 2% or less,
The thickness ratio between the barrier layer and the light receiving layer is 1:99 to 40:60, and the barrier layer has a porosity smaller than the porosity of the light receiving layer. When the porosity of the layer is A [%] and the porosity of the light receiving layer is B [%], B / A is 10 or more,
The barrier layer is mainly composed of titanium oxide formed by a sol-gel method using a barrier layer material containing titanium alkoxide,
The light receiving layer is mainly composed of titanium oxide formed by a sol-gel method using a light receiving layer material containing titanium alkoxide and titanium oxide powder,
The hole transport layer is mainly composed of a metal iodide compound which is a substance having ion conduction characteristics, and a hole transport layer material containing the substance having ion conduction characteristics is applied onto the dye layer by a coating method. Formed by coating,
The hole transport layer material contains an ammonium halide as a hole transport efficiency improving substance having a function of improving hole transport efficiency.
[0017]
  (4The above barrier layer is formed by the MOD (Metal Organic Deposition or Metal Organic Decomposition) method.One of (1) to (3)The photoelectric conversion element as described in 2.
[0018]
  (5The barrier layer material used when forming the barrier layer by the MOD method includes a titanium alkoxide and an additive having a function of stabilizing the titanium alkoxide.4).
[0019]
  (6The above additive is a hydrolysis inhibitor that inhibits hydrolysis of the titanium alkoxide by substituting the alkoxyl group of the titanium alkoxide and coordinating with the titanium atom of the titanium alkoxide.5).
[0020]
  (7) The resistance value in the thickness direction of the entire barrier layer and the light receiving layer is 100 Ω / cm²Above (1) to ()6).
[0022]
  (8The interface between the barrier layer and the light receiving layer is unclear (1) to (1)7).
[0023]
  (9The barrier layer and the light receiving layer are integrally formed with each other (1) to (1)8).
[0024]
  (10(1) to (1) in which a part of the light receiving layer functions as the barrier layer.9).
[0027]
  (11The light-receiving layer is subjected to a visualization process that enables absorption of light having a wavelength in the visible light region.10).
[0028]
  (12The light-receiving layer has a film shape (1) to (11).
[0031]
  (13The titanium oxide powder has an average particle diameter of 1 nm to 1 μm.12).
[0033]
  (14) The content of the titanium oxide powder in the light receiving layer material is 0.1 to 10% by weight.13).
[0034]
  (15The light-receiving layer is mainly composed of titanium dioxide (1) to (14).
[0039]
  (16The hole transport layer is formed by applying the hole transport layer material onto the light receiving layer while heating the light receiving layer.One of (1) to (15)The photoelectric conversion element as described in 2.
[0050]
  (17(1) to (1) having a substrate for supporting the first electrode.16).
[0051]
  (18) When a voltage of 0.5 V is applied so that the first electrode is positive and the second electrode is negative, the resistance value is 100 Ω / cm.²(1) to (1) having the above characteristics17).
[0053]
  (19(1) to (1) are solar cells.18).
[0054]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the photoelectric conversion element of the present invention shown in the accompanying drawings will be described in detail.
[0055]
<First Embodiment>
FIG. 1 is a partial cross-sectional view showing a first embodiment when the photoelectric conversion element of the present invention is applied to a solar cell, and FIG. It is an enlarged view shown.
[0056]
A solar cell 1A shown in FIG. 1 is a so-called dry solar cell that does not require an electrolyte solution. A barrier layer 8 disposed on the upper surface of the light-receiving layer, a light-receiving layer 4 disposed on the upper surface of the barrier layer 8, a hole transport layer 5 disposed on the upper surface of the light-receiving layer 4, and a surface disposed on the upper surface of the hole transport layer 5. The second electrode 6 is provided.
[0057]
Hereinafter, each component will be described. In the following description, in FIGS. 1 and 2, the upper surface of each layer (each member) is referred to as “upper surface” and the lower surface is referred to as “lower surface”.
[0058]
The substrate 2 is for supporting the first electrode 3, the barrier layer 8, the light receiving layer 4, the hole transport layer 5, and the second electrode 6, and is composed of a flat plate member.
[0059]
In the solar cell 1A of the present embodiment, as shown in FIG. 1, light such as sunlight (hereinafter simply referred to as “light”) is incident from the substrate 2 and the first electrode 3 side described later, for example. (Irradiated) for use. For this reason, each of the substrate 2 and the first electrode 3 is preferably substantially transparent (colorless transparent, colored transparent, or translucent). Thereby, the light can efficiently reach the light receiving surface of the light receiving layer 4.
[0060]
Examples of the constituent material of the substrate 2 include various glass materials, various ceramic materials, various resin materials such as polycarbonate (PC) and polyethylene terephthalate (PET), and various metal materials such as aluminum.
[0061]
The average thickness of the substrate 2 is appropriately set depending on the material, application, and the like, and is not particularly limited. For example, the average thickness can be as follows.
[0062]
When the substrate 2 is made of a hard material such as a glass material, the average thickness is preferably about 0.1 to 1.5 mm, and preferably about 0.8 to 1.2 mm. More preferred.
[0063]
When the substrate 2 is made of a flexible material (flexible material) such as polyethylene terephthalate (PET), the average thickness is preferably about 0.5 to 150 μm, preferably 10 to 75 μm. More preferred is the degree.
In addition, the board | substrate 2 can also be abbreviate | omitted as needed.
[0064]
On the upper surface of the substrate 2, a layered (flat plate) first electrode 3 is provided. In other words, the first electrode 3 is disposed on the light receiving surface side of the light receiving layer 4 described later so as to cover the light receiving surface. The first electrode 3 receives electrons generated in the light receiving layer 4 through the barrier layer 8 and transmits the electrons to the external circuit 100 connected thereto.
[0065]
Examples of the constituent material of the first electrode 3 include indium tin oxide (ITO), fluorine-doped tin oxide (FTO), indium oxide (IO), and tin oxide (SnO).₂), Metal oxides such as aluminum, nickel, cobalt, platinum, silver, gold, copper, molybdenum, titanium, tantalum or alloys containing them, or various carbon materials such as graphite. These can be used alone or in combination of two or more.
[0066]
The average thickness of the first electrode 3 is appropriately set depending on the material, application, and the like, and is not particularly limited. For example, the average thickness can be as follows.
[0067]
When the first electrode 3 is composed of the metal oxide (transparent conductive metal oxide), the average thickness is preferably about 0.05 to 5 μm, preferably 0.1 to 1.5 μm. More preferred is the degree.
[0068]
Further, when the first electrode 3 is made of the above metal or an alloy containing these or various carbon materials, the average thickness is preferably about 0.01 to 1 μm, More preferably, it is about 0.1 μm.
[0069]
In addition, the 1st electrode 3 is not limited to the thing of the structure of illustration, For example, the thing etc. which have the shape which has several comb teeth may be sufficient. In this case, since the light passes between the plurality of comb teeth and reaches the light receiving surface of the light receiving layer 4, the first electrode 3 may not be substantially transparent. Thereby, the range of selection of the constituent material of the 1st electrode 3, a formation method (manufacturing method), etc. can be expanded. In this case, the average thickness of the first electrode 3 is not particularly limited, but is preferably about 1 to 5 μm, for example.
[0070]
Further, as the first electrode 3, such a comb-like electrode and a transparent electrode made of ITO, FTO, or the like can be used in combination (for example, laminated).
[0071]
On the upper surface of the first electrode 3, a film-like (layer-like) barrier layer (short-circuit preventing means) 8 is provided. The details of this barrier layer will be described later.
[0072]
On the upper surface of the barrier layer 8, a light-receiving layer 4 preferably having a film shape (layer shape) is provided. That is, the light receiving layer 4 is located between the first electrode 3 and a second electrode 6 described later. The light receiving layer 4 generates electrons and holes by receiving light.
[0073]
Examples of the constituent material of the light receiving layer 4 include titanium dioxide (TiO 2).₂), Titanium monoxide (TiO), dititanium trioxide (Ti)₂O₃) And the like, zinc oxide (ZnO), tin oxide (SnO)₂) And other n-type semiconductor materials can be used, and one or more of these can be used in combination. Among these, titanium oxide, particularly, Titanium dioxide is preferably used. That is, it is preferable that the light receiving layer 4 is mainly composed of titanium dioxide.
[0074]
Since titanium dioxide is highly sensitive to light, light utilization efficiency is further improved in the light-receiving layer 4 mainly using titanium dioxide as titanium oxide.
[0075]
In addition, since the crystal structure of titanium dioxide is stable, the light-receiving layer 4 mainly composed of titanium dioxide has little secular change (deterioration) even when exposed to a harsh environment, and has stable performance. It has the advantage that it can be obtained continuously for a long time.
[0076]
Furthermore, as titanium dioxide, the crystal structure is mainly composed of anatase-type titanium dioxide, mainly composed of rutile-type titanium dioxide, or a mixture of anatase-type titanium dioxide and rutile-type titanium dioxide. Any of those may be used.
[0077]
Due to the relatively unstable crystal structure of anatase-type titanium dioxide, the light-receiving layer 4 mainly composed of anatase-type titanium dioxide has an advantage that electrons are easily generated.
[0078]
In addition, when mixing rutile type titanium dioxide and anatase type titanium dioxide, the mixing ratio of rutile type titanium dioxide and anatase type titanium dioxide is not particularly limited. It is preferably about 5:95, and more preferably about 80:20 to 20:80.
[0079]
The light receiving layer 4 is porous and has a plurality of holes (pores) 41. FIG. 3 schematically shows a state where light is incident on the light receiving layer 4. As shown in FIG. 3, the light (arrow in FIG. 3) that has passed through the barrier layer 8 penetrates into the light receiving layer 4 and is transmitted through the light receiving layer 4 or reflected in an arbitrary direction within the hole 41. (Diffuse reflection, diffusion, etc.) Thereby, light can generate electrons with high frequency.
[0080]
The porosity of the light receiving layer 4 is not particularly limited. For example, it is preferably about 5 to 90%, more preferably about 15 to 50%, and about 20 to 40%. Further preferred.
[0081]
The light receiving layer 4 may have a relatively large thickness, but preferably has a film shape (layer shape) as described above. Thereby, the solar cell 1A can be thinned (downsized) and the manufacturing cost can be reduced, which is advantageous.
[0082]
In this case, although it does not specifically limit as average thickness (film thickness) of the light reception layer 4, For example, it is preferable that it is about 0.1-300 micrometers, and it is more preferable that it is about 0.5-100 micrometers. More preferably, it is about ˜25 μm.
[0083]
Furthermore, it is preferable that such a light receiving layer 4 is subjected to a visualization process so as to be able to absorb light in a wide range of wavelengths in the visible light region (usually about 400 to 750 nm). Thereby, the light receiving layer 4 can further improve the light utilization efficiency and generate electrons more reliably.
[0084]
Examples of such a visualization method include (1) an oxygen defect forming method for forming oxygen defects, and (2) an atomic substitution method for replacing a part of titanium atoms with a metal atom different from titanium atoms. These 1 type or 2 types can be used together. Hereinafter, the methods (1) and (2) will be described in detail.
[0085]
(1) Oxygen defect formation method
The oxygen defect forming method is not particularly limited. For example, titanium oxide powder, or a film-like body formed by forming a light-receiving layer material (sol solution, coating liquid) described later into a film shape (hereinafter simply referred to as “film-like body”). A method of heat treatment in a hydrogen atmosphere (reducing atmosphere), vacuum (for example, 1 × 10^-Five~ 1x10^-6A method of heat treatment under Torr), a method of low-temperature plasma treatment, and the like. Among these, the oxygen defect forming method is preferably a method in which a titanium oxide powder or a film-like body is heat-treated in a hydrogen atmosphere.
[0086]
(2) Atomic substitution method
As the atomic substitution method, for example, a method of firing (sintering) a film-like body of a light-receiving layer material to which an inorganic sensitizer composed of the metal atom or its oxide is added, Examples thereof include a method of injecting (implanting) an ionized metal atom. Among these, as the atomic substitution method, a method of firing a film-like body of a light receiving layer material to which an inorganic sensitizer is added is more preferable.
Such an atomic substitution method can also be applied to titanium oxide powder.
[0087]
The visualization process is not limited to the methods (1) and (2), and any method may be used as long as the light-receiving layer 4 can be visualized. For example, a method using a dye. Can be mentioned.
[0088]
As such a method, for example, a method of forming a dye (for example, a ruthenium complex compound, a phthalocyanine compound, a porphyrin compound, or the like) in layers along the outer surface of the light receiving layer 4 and the inner surface of the hole 41, or And a method of dispersing in. Such a method may be used in combination with the methods (1) and / or (2).
[0089]
A layered (flat plate) hole transport layer 5 is provided on the upper surface of the light receiving layer 4. That is, the hole transport layer 5 is located between the light receiving layer 4 and a second electrode 6 described later. The hole transport layer 5 has a function of capturing and transporting holes generated in the light receiving layer 4. In other words, the hole transport layer 5 has a function of transporting holes to the external circuit 100 via a second electrode 6 described later or the hole transport layer 5 itself becomes an electrode.
[0090]
The average thickness of the hole transport layer 5 is not particularly limited. For example, it is preferably about 1 to 500 μm, more preferably about 10 to 300 μm, and further preferably about 10 to 30 μm. .
[0091]
Examples of the constituent material of the hole transport layer 5 include substances having various ion conduction characteristics, triphenyldiamine (monomers, polymers, etc.), polyaniline, polypyrrole, polythiophene, phthalocyanine compounds (for example, copper phthalocyanine) or derivatives thereof. Various p-type semiconductor materials, or metals such as aluminum, nickel, cobalt, platinum, silver, gold, copper, molybdenum, titanium, and tantalum, or alloys containing these, and one or more of these Two or more kinds can be used in combination.
[0092]
A layered (flat plate) second electrode 6 is provided on the upper surface of the hole transport layer 5. The average thickness of the second electrode 6 is appropriately set depending on the material, application, etc., and is not particularly limited.
[0093]
The constituent material of the second electrode 6 is, for example, a metal such as aluminum, nickel, cobalt, platinum, silver, gold, copper, molybdenum, titanium, tantalum or an alloy containing these metals, or a graphite. Various carbon materials etc. are mentioned, Among these, it can use combining 1 type (s) or 2 or more types.
Note that the second electrode 6 may be omitted as necessary.
[0094]
In the solar cell 1A, a rectifying barrier having diode characteristics is formed at the interface between the hole transport layer 5 and the light receiving layer 4, and a rectifying action is generated.
[0095]
In the solar cell 1 </ b> A, when light is incident on the light receiving layer 4, electrons are excited in the light receiving layer 4 to generate electrons and holes. An electric field is present in the rectifying barrier due to the interface potential. Therefore, these electrons and holes are drawn by the electric field at the interface, and a potential difference (photoelectromotive force) is generated between the first electrode 3 and the second electrode 6, and the external circuit 100 Current (photoexcitation current) flows.
[0096]
When this state is represented by an equivalent circuit, a current circulation circuit having a diode 200 as shown in FIG. 4 is formed.
[0097]
In the case of obtaining such a rectifying barrier, as the constituent material of the hole transport layer 5, a material having ion conduction characteristics is preferably used among the materials described above. That is, it is preferable that the hole transport layer 5 is mainly composed of a substance having ion conduction characteristics. Thereby, the hole transport layer 5 can transport holes generated in the light receiving layer 4 more efficiently.
[0098]
In addition, examples of the substance having the ionic conductivity include metal iodide compounds such as CuI and AgI, metal halide compounds such as a metal bromide compound such as AgBr, and metal thiocyanate such as RhoSCN (rhodan). Metal compounds) and the like, and one or more of them can be used in combination.
[0099]
Among these, metal halide compounds such as metal iodide compounds and metal bromide compounds are preferable as substances having ion conduction characteristics. The metal halide compound is particularly excellent in ion conduction characteristics.
[0100]
Furthermore, it is particularly preferable to use one or more of metal iodide compounds such as CuI and AgI in combination as the substance having ion conduction characteristics. Metal iodide compounds are extremely excellent in ion conduction characteristics. For this reason, by using a metal iodide compound as the main material of the hole transport layer 5, the photoelectric conversion efficiency (energy conversion efficiency) of the solar cell 1A can be further improved.
[0101]
Further, the hole transport layer 5 is formed so as to enter the hole 41 of the light receiving layer 4 as shown in FIG. Thereby, the formation area of the rectifying barrier can be increased, and holes generated in the light receiving layer 4 can be transmitted to the hole transport layer 5 more efficiently. As a result, the solar cell 1A can further improve the power generation efficiency.
[0102]
Note that the rectifying barrier may also be formed at the interface between the light receiving layer 4 and the first electrode 3.
[0103]
Electron and hole are simultaneously generated in the light receiving layer 4 by light irradiation (light reception), but in the following description, for convenience, “electron is generated” is described.
[0104]
Now, the present invention is characterized in that a short-circuit prevention means for preventing or suppressing a short-circuit (leakage) between the first electrode 3 and the hole transport layer 5 is provided.
[0105]
Hereinafter, this short-circuit prevention means will be described in detail.
In the present embodiment, as a short-circuit prevention means, a barrier layer 8 is provided which is in the form of a film (layer) and is positioned between the first electrode 3 and the light receiving layer 4. The barrier layer 8 is formed so that the porosity is smaller than the porosity of the light receiving layer 4.
[0106]
When manufacturing the solar cell 1A, as will be described later, for example, a hole transport layer material is applied to the upper surface of the light receiving layer 4 by a coating method.
[0107]
In this case, in the solar cell in which the barrier layer 8 is not provided, when the porosity of the light receiving layer 4 is increased, the hole transport layer material penetrates into the holes 41 of the light receiving layer 4 and the first electrode 3 may be reached. That is, in a solar cell that does not have the barrier layer 8, contact (short circuit) occurs between the first electrode 3 and the hole transport layer 5, thereby increasing leakage current and generating efficiency (photoelectric conversion efficiency). May be reduced.
[0108]
On the other hand, in the solar cell 1 </ b> A provided with the barrier layer 8, the above-described disadvantages are prevented, and a decrease in power generation efficiency is preferably prevented or suppressed.
[0109]
Further, when the porosity of the barrier layer 8 is A [%] and the porosity of the light receiving layer 4 is B [%], B / A is preferably about 1.1 or more, for example. More preferably, it is about 5 or more, and more preferably about 10 or more. Thereby, the barrier layer 8 and the light receiving layer 4 can each exhibit their functions more suitably.
[0110]
More specifically, the porosity A of the barrier layer 8 is, for example, preferably about 20% or less, more preferably about 5% or less, and still more preferably about 2% or less. . That is, the barrier layer 8 is preferably a dense layer. Thereby, the said effect can be improved more.
[0111]
Furthermore, the ratio of the thickness of the barrier layer 8 and the light receiving layer 4 is not particularly limited, but is preferably about 1:99 to 60:40, for example, about 10:90 to 40:60. More preferred. In other words, the ratio of the thickness of the barrier layer 8 to the entire barrier layer 8 and the light receiving layer 4 is preferably about 1 to 60%, and more preferably about 10 to 40%. As a result, the barrier layer 8 can more reliably prevent or suppress a short circuit due to contact between the first electrode 3 and the hole transport layer 5, and the light arrival rate to the light receiving layer 4 is reduced. This can be suitably prevented. In addition, the light receiving layer 4 can suitably generate electrons.
[0112]
More specifically, the average thickness (film thickness) of the barrier layer 8 is, for example, preferably about 0.01 to 10 μm, more preferably about 0.1 to 5 μm, 0.5 More preferably, it is about ˜2 μm. Thereby, the said effect can be improved more.
[0113]
The constituent material of the barrier layer 8 is not particularly limited. For example, in addition to titanium oxide which is the main constituent material of the light receiving layer 4, for example, SrTiO.₃, ZnO, SiO₂, Al₂O₃, SnO₂Various metal oxides such as CdS, CdSe, TiC, Si₃N₄, SiC, B₄One or two or more of various metal compounds such as N and BN can be used in combination. Among these, it is preferable to have an electrical conductivity equivalent to that of the light receiving layer 4, and in particular, oxidation Those mainly composed of titanium are more preferable. By configuring the barrier layer 8 with such a material, electrons generated in the light receiving layer 4 can be more efficiently transferred to the barrier layer 8, and as a result, the power generation efficiency of the solar cell 1A can be further improved. Can do.
[0114]
The resistance values in the thickness direction of the barrier layer 8 and the electron transport layer 4 are not particularly limited, but the resistance values in the thickness direction of the barrier layer 8 and the electron transport layer 4 as a whole, that is, the barrier layer 8 and The resistance value in the thickness direction of the laminate with the electron transport layer 4 is 100 Ω / cm.²It is preferable that it be about 1 kΩ / cm or more.²More preferably, it is about the above. Thereby, the leak (short circuit) between the 1st electrode 3 and the positive hole transport layer 5 can be prevented or suppressed more reliably, and the advantage that the fall of the power generation efficiency of 1 A of solar cells can be prevented. There is.
[0115]
Further, the interface between the barrier layer 8 and the light receiving layer 4 may not be clear or may be clear, but is preferably not clear (unclear). That is, it is preferable that the barrier layer 8 and the light receiving layer 4 are integrally formed and partially overlap each other. Thereby, the transmission of electrons between the barrier layer 8 and the light receiving layer 4 can be performed more reliably (efficiently).
[0116]
Further, the barrier layer 8 and the light receiving layer 4 are made of materials having the same composition (for example, a material mainly made of titanium dioxide), and only different in their porosity, that is, the light receiving layer 4 A part may function as the barrier layer 8.
[0117]
In this case, the light receiving layer 4 has a dense portion and a rough portion in the thickness direction, and the dense portion functions as the barrier layer 8.
[0118]
In this case, the dense portion is preferably formed on the first electrode 3 side of the light-receiving layer 4, but can also be formed at an arbitrary position in the thickness direction.
[0119]
Further, in this case, the light receiving layer 4 may have a configuration having a portion where a rough portion is sandwiched between dense portions, a configuration having a portion where a dense portion is sandwiched between rough portions, or the like. .
[0120]
In such a solar cell 1A, the photoelectric conversion efficiency is R when the incident angle of light to the light receiving layer 4 is 90 °.₉₀And the photoelectric conversion efficiency when the incident angle of light is 52 ° is R₅₂R₅₂/ R₉₀Is preferably about 0.8 or more, and more preferably about 0.85 or more. Satisfying such a condition means that the light receiving layer 4 has low directivity with respect to light, that is, has isotropic properties. Therefore, such a solar cell 1A can generate power more efficiently over almost the entire solar sunshine duration.
[0121]
Furthermore, in the solar cell 1A, when a voltage of 0.5 V is applied so that the first electrode 3 is positive and the second electrode 6 (hole transport layer 5) is negative, the resistance value is For example, 100Ω / cm²It is preferable to have a characteristic of about 1 kΩ / cm or more.²It is more preferable to have characteristics that are about the above. Having such characteristics indicates that in the solar cell 1A, a short circuit (leakage) due to contact or the like between the first electrode 3 and the hole transport layer 5 is preferably prevented or suppressed. Is. Therefore, in such a solar cell 1A, the power generation efficiency (photoelectric conversion efficiency) can be further improved.
[0122]
Such a solar cell 1A can be manufactured as follows, for example. First, a substrate 2 made of, for example, soda glass is prepared. A substrate having a uniform thickness and no deflection is preferably used for the substrate 2.
[0123]
<1> First, the first electrode 3 is formed on the upper surface of the substrate 2.
The first electrode 3 can be formed by using, for example, a vapor deposition method, a sputtering method, a printing method, or the like as the material of the first electrode 3 made of, for example, FTO.
[0124]
<2> Next, the barrier layer 8 is formed on the upper surface of the first electrode 3.
The barrier layer 8 can be formed by, for example, a sol-gel method, a vapor deposition (vacuum vapor deposition) method, a sputtering method (high frequency sputtering, DC sputtering), a spray pyrolysis method, a jet mold (plasma spraying) method, a CVD method, or the like. Of these, the sol-gel method is preferable.
[0125]
This sol-gel method is very easy to operate. For example, it can be used in combination with various coating methods such as dipping, dripping, doctor blade, spin coating, brush coating, spray coating, roll coater, etc. However, the barrier layer 8 can be suitably formed into a film shape (thick film and thin film).
[0126]
Further, according to the coating method, the barrier layer 8 having a desired pattern shape can be easily obtained by performing masking using a mask or the like, for example.
[0127]
As this sol-gel method, a method of preventing (preventing) a reaction (for example, hydrolysis, polycondensation, etc.) of a titanium compound (organic or inorganic) described later in the barrier layer material (hereinafter referred to as “MOD (Metal Organic Deposition or Metal Organic Decomposition) method ”), or a method that allows this, and the MOD method is particularly preferred.
[0128]
According to this MOD method, the stability of the titanium compound (organic or inorganic) in the barrier layer material is maintained, and the barrier layer 8 is more easily and reliably (with good reproducibility) and dense (within the above range). Inside porosity).
[0129]
In particular, organic titanium such as titanium alkoxide (metal alkoxide) that is chemically very unstable (decomposable) such as titanium tetraisopropoxide (TPT), titanium tetramethoxide, titanium tetraethoxide, titanium tetrabutoxide, etc. Using compound, dense TiO₂This MOD method is optimal when forming a layer (barrier layer 8 of the present invention).
[0130]
Hereinafter, a method of forming the barrier layer 8 by the MOD method will be described.
[Preparation of barrier layer material]
For example, one or a combination of two or more organic titanium compounds such as titanium tetraisopropoxide (TPT), titanium tetramethoxide, titanium tetraethoxide, titanium alkoxide (metal alkoxide) such as titanium tetrabutoxide First, the organic titanium compound (or this solution) is added to an organic solvent (or a mixed solvent thereof) such as anhydrous ethanol, 2-butanol, 2-propanol, 2-n-butoxyethanol, or the like. Dissolve.
[0131]
Thereby, the density | concentration (content) in the said solution of an organic titanium compound is prepared (for example, about 0.1-10 mol / L), and the viscosity of the barrier layer material obtained is prepared. The viscosity of the barrier layer material is appropriately set depending on the type of coating method and the like, and is not particularly limited. However, when spin coating is used, the viscosity is preferably high (for example, about 0.5 to 20 cP (room temperature)). When spray coating is used, the viscosity is preferably low (for example, about 0.1 to 2 cP (room temperature)).
[0132]
Next, an additive having a function of stabilizing the titanium alkoxide (metal alkoxide) such as titanium tetrachloride, acetic acid, acetylacetone, triethanolamine, diethanolamine is added to the solution.
[0133]
By adding these additives, these additives replace the alkoxide (alkoxyl group) coordinated to the titanium atom in the titanium alkoxide, and coordinate to the titanium atom. Thereby, hydrolysis of titanium alkoxide is suppressed and stabilized. That is, these additives function as a hydrolysis inhibitor that inhibits hydrolysis of titanium alkoxide. In this case, the compounding ratio of this additive and titanium alkoxide is not particularly limited, but is preferably about 1: 2 to 8: 1 in terms of a molar ratio, for example.
[0134]
More specifically, when diethanolamine is coordinated to titanium alkoxide, it replaces (substitutes) the alkoxide (alkoxyl group) of titanium alkoxide, and two molecules of diethanolamine are coordinated to the titanium atom. The compound substituted with diethanolamine is a compound that is more stable in producing titanium dioxide than titanium alkoxide.
The same applies to other combinations.
[0135]
Thereby, a barrier layer material (a sol solution for forming a barrier layer: a sol solution for MOD) is obtained.
[0136]
Further, when an inorganic titanium compound such as titanium tetrachloride (TTC) is used, the inorganic titanium compound (or this solution) is converted into an organic material such as absolute ethanol, 2-butanol, 2-propanol, or 2-n-butoxyethanol. By dissolving in a solvent (or a mixed solvent thereof), the organic solvent is coordinated to titanium and becomes a stable compound without adding an additive.
[0137]
Furthermore, when an organic titanium compound such as titanium oxyacetylacetonate (TOA) is used, this organic titanium compound (or this solution) is stable by itself, and thus stable when dissolved in the organic solvent. A barrier layer material can be obtained.
[0138]
In the present invention, when the barrier layer 8 is formed by the MOD method, it is optimal to use a solution prepared by the following method among the three solutions described above. That is, an organic titanium compound (or this solution) such as titanium tetraisopropoxide (TPT), titanium tetramethoxide, titanium tetraethoxide, or titanium alkoxide such as titanium tetrabutoxide is dissolved (or diluted) with a solvent, It is optimal to use a solution prepared by a method of adding an additive such as titanium tetrachloride, acetic acid, acetylacetone, triethanolamine, diethanolamine to the solution. According to this method, a compound stabilized in producing titanium dioxide by coordinating the additive to the titanium atom of the titanium alkoxide can be obtained.
[0139]
Thereby, a chemically unstable titanium alkoxide can be made into a chemically stable compound. Such a compound is extremely useful in forming the barrier layer 8 of the present embodiment, that is, the dense barrier layer 8 mainly composed of titanium dioxide.
[0140]
[Formation of barrier layer 8]
A barrier layer material is applied to the upper surface of the first electrode 3 by a coating method (for example, spin coating) to form a film. When spin coating is used as the coating method, it is preferable to perform the rotation at about 500 to 4000 rpm.
[0141]
Next, heat treatment is applied to the coating film. Thereby, the organic solvent is volatilized and removed. The heat treatment conditions are preferably about 50 to 250 ° C. and about 1 to 60 minutes, more preferably about 100 to 200 ° C. and about 5 to 30 minutes.
[0142]
Such heat treatment can be performed, for example, in the atmosphere or in nitrogen gas, for example, various inert gases, vacuum, reduced pressure (for example, 1 × 10^-1~ 1x10^-6(Torr) may be performed in a non-oxidizing atmosphere.
[0143]
Note that the barrier layer material may be applied to the upper surface of the first electrode 3 while the first electrode 3 is heated.
[0144]
Further, the coating film is subjected to heat treatment at a temperature higher than the heat treatment. As a result, organic components remaining in the coating film are removed, and titanium dioxide (TiO₂) To form a barrier layer 8 made of titanium dioxide having an amorphous or anatase type crystal structure. The heat treatment condition is preferably about 300 to 700 ° C. for about 1 to 70 minutes, more preferably about 400 to 550 ° C. for about 5 to 45 minutes.
[0145]
In addition, the atmosphere of this heat processing can be made into the atmosphere similar to the said heat processing.
[0146]
The above operation is preferably performed about 1 to 20 times, more preferably about 1 to 10 times to form the barrier layer 8 having the average thickness as described above.
[0147]
In this case, the thickness (film thickness) of the coating film obtained by one operation is preferably about 100 nm or less, and more preferably about 50 nm or less. By laminating such thin films to form the barrier layer 8, the barrier layer 8 can be made more uniform and dense. Moreover, adjustment of the film thickness obtained by the said operation of 1 time can be easily performed by adjusting the viscosity of barrier layer material.
[0148]
Prior to the formation of the barrier layer 8, the upper surface of the first electrode 3 is, for example, O₂The organic substance adhering to the upper surface of the first electrode 3 may be removed by performing plasma treatment, EB treatment, cleaning treatment with an organic solvent (for example, ethanol, acetone, etc.), or the like. In this case, a mask layer is formed on the upper surface of the first electrode 3 except for a portion where the barrier layer 8 is to be formed and masked. The mask layer may be removed after the barrier layer 8 is formed, or may be removed after the solar cell 1A is completed.
[0149]
<3> Next, the light receiving layer 4 is formed on the upper surface of the barrier layer 8.
The light-receiving layer 4 can be formed by, for example, a sol / gel method, a vapor deposition method, a sputtering method, or the like, and among these, it is preferably formed by a sol / gel method.
[0150]
This sol-gel method is very easy to operate. For example, it can be used in combination with various coating methods such as dipping, dripping, doctor blade, spin coating, brush coating, spray coating, roll coater, etc. However, the light receiving layer 4 can be suitably formed into a film shape (thick film and thin film).
[0151]
Further, according to the coating method, the light-receiving layer 4 having a desired pattern shape can be easily obtained by performing masking using a mask or the like, for example.
[0152]
For the formation of the light receiving layer 4, it is preferable to use a sol solution containing powder of the light receiving layer material. Thereby, the light receiving layer 4 can be made porous easily and reliably.
[0153]
The average particle size of the powder of the light receiving layer material is not particularly limited, but is preferably about 1 nm to 1 μm, and more preferably about 5 to 50 nm, for example. By setting the average particle diameter of the powder of the light receiving layer material within the above range, the uniformity of the powder of the light receiving layer material in the sol liquid can be improved. In addition, by reducing the average particle diameter of the powder of the light receiving layer material in this way, the surface area (specific surface area) of the obtained light receiving layer 4 can be increased, which contributes to the improvement of the power generation efficiency of the solar cell 1A. .
[0154]
Below, an example of the shaping | molding method of the light reception layer 4 is demonstrated. In the following description, the description will be made by distinguishing between different visualization methods (<3A>, <3B> oxygen defect formation method, <3C> atom substitution method), but the same matters will be described later. I will omit it. Further, the oxygen defect forming method will be described separately for the case of applying to <3A> titanium oxide powder and the case of applying to <3B> film-like body.
[0155]
<3A>: Oxygen defect formation method (when applied to titanium oxide powder)
[Preparation of titanium oxide powder (light-receiving layer material powder)]
<A0> Rutile-type titanium dioxide powder and anatase-type titanium dioxide powder are blended and mixed at a predetermined blending ratio (including only rutile-type titanium dioxide powder).
[0156]
The average particle size of these rutile type titanium dioxide powders and the average particle size of anatase type titanium dioxide powders may be different or the same, but are preferably different.
In addition, the average particle diameter as a whole titanium oxide powder shall be the above-mentioned range.
[0157]
In addition, when it is assumed that the crystal structure of titanium dioxide is changed (changed) from anatase type to rutile type by the heat treatment by the oxygen defect formation method described later, only anatase type titanium dioxide powder may be used. Good.
[0158]
Next, the blended titanium oxide powder is subjected to heat treatment by an oxygen defect forming method. As heat treatment conditions at this time, in a hydrogen atmosphere, preferably at a temperature of about 800 to 1200 ° C. and about 0.2 to 3 hours, more preferably at a temperature of about 900 to 1200 ° C. and about 0.5 to 1 hour. Is done.
[0159]
At this time, when the titanium oxide powder contains anatase-type titanium dioxide powder, depending on the heat treatment temperature and heat treatment time, the anatase-type titanium dioxide may be partly or entirely transferred to the rutile type. There are things to do.
[0160]
The oxygen defect formation method is performed before the present step <A0>, and is applied to the rutile type titanium dioxide powder and / or the anatase type titanium dioxide powder, and the titanium dioxide powder is blended to prepare the titanium oxide powder. It may be.
[0161]
[Preparation of sol solution (light-receiving layer material)]
<A1> First, for example, titanium tetraisopropoxide (TPT), titanium tetramethoxide, titanium tetraethoxide, titanium alkoxide such as titanium tetrabutoxide, organic titanium compounds such as titanium oxyacetylacetonate (TOA), One or a combination of two or more inorganic titanium compounds such as titanium tetrachloride (TTC), for example, an organic solvent such as anhydrous ethanol, 2-butanol, 2-propanol, 2-n-butoxyethanol (or the like) It dissolves in these mixed solvents).
[0162]
At this time, although it does not specifically limit as a density | concentration (content) in the solution of a titanium compound (organic or inorganic), For example, it is preferable to set it as about 0.1-3 mol / L.
[0163]
Next, various additives are added to this solution as necessary. For example, when titanium alkoxide is used as the organic titanium compound, since titanium alkoxide has low chemical stability, for example, an additive such as acetic acid, acetylacetone, or nitric acid is added. Thereby, titanium alkoxide can be made into a chemically stable compound. In this case, the compounding ratio of this additive and titanium alkoxide is not particularly limited, but is preferably about 1: 2 to 8: 1 in terms of a molar ratio, for example.
[0164]
<A2> Next, for example, water such as distilled water, ultrapure water, ion-exchanged water, or RO water is mixed with this solution. The mixing ratio of water and titanium compound (organic or inorganic) is preferably about 1: 4 to 4: 1 in molar ratio.
[0165]
<A3> Next, the titanium oxide powder prepared in the step <A0> is mixed with this solution to obtain a suspension (dispersion) liquid.
[0166]
<A4> Further, the suspension is diluted with the organic solvent (or mixed solvent). Thereby, a sol solution is prepared. The dilution factor is preferably about 1.2 to 3.5 times, for example.
[0167]
In addition, the content of the titanium oxide powder (light receiving layer material powder) in the sol liquid is not particularly limited, but is preferably about 0.1 to 10 wt% (% by weight), for example, 0.5 to More preferably, it is about 5 wt%. Thereby, the porosity of the light receiving layer 4 can be preferably within the above range.
[0168]
[Formation of light-receiving layer 4]
<A5> While the barrier layer 8 is preferably heated, a sol solution is applied to the upper surface of the barrier layer 8 by a coating method (for example, dropping) to obtain a film-like body. Although it does not specifically limit as this heating temperature, For example, it is preferable that it is about 80-180 degreeC, and it is more preferable that it is about 100-160 degreeC.
[0169]
The above operation is preferably performed about 1 to 10 times, more preferably about 5 to 7 times, to form the light receiving layer 4 having the average thickness as described above.
[0170]
Next, the light-receiving layer 4 may be subjected to heat treatment (for example, firing) at a temperature of about 250 to 500 ° C. for about 0.5 to 3 hours as necessary.
[0171]
<A6> The light-receiving layer 4 obtained in the step <A5> can be post-treated as necessary.
[0172]
Examples of the post-processing include mechanical processing (post-processing) such as grinding and polishing for adjusting the shape, and post-processing such as cleaning and chemical processing.
[0173]
<3B>: Oxygen defect formation method (when applied to a film-like body)
[Preparation of titanium oxide powder (light-receiving layer material powder)]
<B0> A rutile type titanium dioxide powder and an anatase type titanium dioxide powder are blended and mixed at a predetermined blending ratio (including the case of only a rutile type titanium dioxide powder). In addition, when it is assumed that the crystal structure of titanium dioxide is changed (changed) from anatase type to rutile type by heat treatment by the oxygen defect formation method described later, only anatase type titanium dioxide powder may be used. Good.
[0174]
[Preparation of sol solution (light-receiving layer material)]
<B1> to <B4> Steps similar to the steps <A1> to <A4> are performed.
[0175]
[Formation of light-receiving layer 4]
<B5> After performing the same process as the process <A5>, the film-like body is subjected to a heat treatment by an oxygen defect forming method to obtain the light receiving layer 4. As the heat treatment conditions, in a hydrogen atmosphere, the temperature is preferably about 800 to 1200 ° C. and about 0.2 to 3 hours, more preferably the temperature is about 900 to 1200 ° C. and about 0.5 to 1 hour. .
[0176]
In this case, the heat treatment (for example, firing) in the step <A5> can be combined with the heat treatment by the oxygen defect forming method.
[0177]
<B6> If necessary, the same step as the step <A6> is performed.
[0178]
<3C>: Atom substitution method
[Preparation of titanium oxide powder (light-receiving layer material powder)]
<C0> A rutile type titanium dioxide powder and an anatase type titanium dioxide powder are blended and mixed at a predetermined blending ratio (including only a rutile type titanium dioxide powder). In addition, when it is assumed that the crystal structure of titanium dioxide is transferred (changed) from anatase type to rutile type by firing by an atomic substitution method described later, only anatase type titanium dioxide powder may be used. .
[0179]
[Preparation of sol solution (light-receiving layer material)]
<C1> to <C2> Steps similar to the steps <A1> to <A2> are performed.
[0180]
<C3> In the same step as the step <A3>, an inorganic sensitizer is added to the suspension.
[0181]
Although it does not specifically limit as this inorganic sensitizer, For example, chromium, vanadium, nickel, iron, manganese, copper, zinc, niobium, or these oxides etc. are mentioned, Of these, 1 type or 2 types A combination of the above can be used.
[0182]
Further, the content of the inorganic sensitizer is not particularly limited, but is preferably about 0.1 to 2.5 μmol per 1 g of titanium oxide powder (light receiving layer material powder). More preferably, it is about 5 to 2.0 μmol.
[0183]
If the titanium oxide powder contains anatase-type titanium dioxide powder and it is desired to prevent the crystal structure of the anatase-type titanium dioxide from transitioning to the rutile type, a sintering aid is added.
[0184]
The sintering aid is preferably a metal oxide having a melting point of 900 ° C. or lower. Examples of the metal oxide include, but are not limited to, molybdenum trioxide, dibismuth trioxide, lead oxide, palladium oxide, antimony trioxide, tellurium dioxide, and dithallium trioxide. Among these, One kind or a combination of two or more kinds can be used.
[0185]
In this case, the blending ratio of the sintering aid and the titanium oxide powder (light receiving layer material powder) is not particularly limited, but is preferably about 1:99 to 40:60, for example, by volume ratio. : It is more preferable that it is about 95-20: 80.
[0186]
Thereby, since the film-like body can be fired (sintered) at a temperature of 900 ° C. or lower, it is possible to more reliably prevent (suppress) the transition of the crystal structure of titanium dioxide from the anatase type to the rutile type.
[0187]
<C4> A step similar to the step <A4> is performed. Thereby, a sol solution (light-receiving layer material) is prepared.
[0188]
[Formation of light-receiving layer 4]
<C5> After performing the same process as the process <A5>, the film-like body is, for example, air, nitrogen gas, various inert gases, vacuum, reduced pressure (for example, 1 × 10^-1~ 1x10^-6Firing (sintering) in a non-oxidizing atmosphere such as Torr).
As firing conditions at this time, for example, the following can be performed.
[0189]
(1) When the titanium oxide powder does not contain anatase-type titanium dioxide powder, or when it is assumed that the crystal structure of titanium dioxide transitions from anatase-type to rutile-type, the temperature is preferably about 1000 to 1200 ° C. And about 0.5 to 10 hours.
[0190]
{Circle around (2)} When the crystal structure of titanium dioxide is not supposed to be transferred from anatase type to rutile type (to be prevented), the temperature is preferably about 900 ° C. or less and about 1 to 26 hours.
[0191]
In this case, the heat treatment (for example, firing) in the step <A5> can also be used for firing by this atomic substitution method.
[0192]
Further, such an atomic substitution method may be applied to rutile type titanium dioxide powder and / or anatase type titanium dioxide powder before the preparation of titanium oxide powder (light receiving layer material powder), or oxidation. You may make it apply to this titanium oxide powder after preparation of titanium powder. In these cases, the firing by the atomic substitution method in this step <C5> can be omitted.
[0193]
<C6> If necessary, the same step as the step <A6> is performed.
[0194]
The light receiving layer 4 can also be formed as follows, for example. Hereinafter, another method for forming the light receiving layer 4 will be described. In the following description, differences from the above-described formation method will be mainly described, and description of similar matters will be omitted. Further, in the following description, the visualization processing method (<3A ′>, <3B ′> oxygen defect formation method, <3C ′> atom substitution method) will be described in distinction, but the same matters will be described later. It is omitted in the explanation. Further, the oxygen defect forming method will be described separately for the case of applying to <3A '> titanium oxide powder and the case of applying to <3B'> film-like body.
[0195]
<3A '>: Oxygen defect formation method (when applied to titanium oxide powder)
[Preparation of titanium oxide powder (light-receiving layer material powder)]
<A′0> A step similar to the step <A0> is performed.
[0196]
[Preparation of coating solution (light-receiving layer material)]
<A′1> First, the titanium oxide powder prepared in the above step is suspended in an appropriate amount of water (for example, distilled water, ultrapure water, ion-exchanged water, RO water, or the like).
[0197]
<A′2> Next, a stabilizer such as nitric acid is added to the suspension, and the suspension is sufficiently kneaded in an agate (or alumina) mortar.
[0198]
<A′3> Next, the above water is added to the suspension and further kneaded. At this time, the blending ratio of the stabilizer and water is preferably about 10:90 to 40:60, more preferably about 15:85 to 30:70 in volume ratio, and the viscosity of the suspension is For example, it is set to about 0.2 to 30 cP (normal temperature).
[0199]
<A′4> Thereafter, a surfactant is added to the suspension so as to have a final concentration of about 0.01 to 5 wt%, and kneaded. Thereby, a coating liquid (light receiving layer material) is prepared.
[0200]
The surfactant may be cationic, anionic, amphoteric or nonionic, but preferably a nonionic one.
[0201]
Further, as the stabilizer, a surface modifying reagent of titanium oxide such as acetic acid or acetylacetone can be used instead of nitric acid.
[0202]
Moreover, you may add various additives, such as binders, such as polyethyleneglycol, a plasticizer, antioxidant, in a coating liquid (light receiving layer material) as needed.
[0203]
[Formation of light-receiving layer 4]
<A′5> On the upper surface of the first electrode 3, a coating solution is applied and dried by a coating method (for example, dipping) to form a film-like body (coating film). Alternatively, the coating and drying operations may be performed a plurality of times for lamination. Thereby, the light receiving layer 4 is obtained.
[0204]
Next, the light-receiving layer 4 may be subjected to heat treatment (for example, firing) at a temperature of about 250 to 500 ° C. for about 0.5 to 3 hours as necessary. Thereby, the titanium oxide powders (powder of the light receiving layer material) that have stopped merely contacting each other are diffused at the contact portions, and the titanium oxide powders are fixed (fixed) to some extent.
[0205]
<A′6> A step similar to the step <A6> is performed.
[0206]
<3B>: Oxygen defect formation method (when applied to a film-like body)
[Preparation of titanium oxide powder (light-receiving layer material powder)]
<B′0> A step similar to the step <B0> is performed.
[0207]
[Preparation of coating solution (light-receiving layer material)]
<B′1> to <B′4> Steps similar to the steps <A′1> to <A′4> are performed.
[0208]
[Formation of light-receiving layer 4]
<B′5> After performing the same step as the step <A′5>, heat treatment is performed in the same manner as the step <B5>.
[0209]
<B′6> If necessary, the same step as the step <A′6> is performed.
[0210]
<3C '>: Atom substitution method
[Preparation of titanium oxide powder (light-receiving layer material powder)]
<C′0> A step similar to the step <C0> is performed.
[0211]
[Preparation of coating solution (light-receiving layer material)]
<C′1> to <C′3> Steps similar to the steps <A′1> to <A′3> are performed.
[0212]
<C′4> In the same step as the step <A′4>, in the suspension, in the same manner as in the step <C3>, the inorganic sensitizer and, if necessary, the sintering Add auxiliary agent and knead. Thereby, a coating liquid (light receiving layer material) is prepared.
[0213]
[Formation of light-receiving layer 4]
<C′5> After performing the same step as the step <A′5>, firing is performed in the same manner as the operation described in the step <C5>.
The light receiving layer 4 is obtained through the above steps.
[0214]
<4> Next, the hole transport layer 5 is formed on the upper surface of the light receiving layer 4.
For the hole transport layer 5, for example, a hole transport layer material (electrode material) containing a substance having ion conduction characteristics such as CuI is applied to the upper surface of the light receiving layer 4, for example, dipping, dropping, doctor blade, spin coating, brush It is preferably formed by coating by various coating methods such as coating, spray coating, and roll coater.
[0215]
According to such a coating method, the hole transport layer 5 can be formed so as to surely penetrate into the hole 41 of the light receiving layer 4.
[0216]
Further, after the coating film is formed, the coating film may be subjected to a heat treatment, but it is preferable to apply the hole transport layer material to the upper surface of the light receiving layer 4 while heating the light receiving layer 4. This is advantageous for forming the hole transport layer 5 more quickly, that is, for shortening the manufacturing time of the solar cell 1A.
[0217]
The heating temperature is preferably about 50 to 150 ° C. In addition, when performing heat processing after coating film formation, you may dry a coating film before this heat processing.
The above operation may be repeated a plurality of times.
[0218]
More specifically, a laminate of the substrate 2, the first electrode 3, the barrier layer 8 and the light receiving layer 4 is placed on a hot plate heated to about 80 ° C., and the hole transport layer material is used as the light receiving layer 4. Drip onto the top surface of and dry. This operation is performed a plurality of times to form the hole transport layer 5 having the average thickness as described above.
[0219]
Although it does not specifically limit as a solvent used for a positive hole transport layer material, For example, organic solvents, such as acetonitrile, ethanol, methanol, isopropyl alcohol, or 1 type, or 2 or more types, such as various water, can be used in combination. .
[0220]
In addition, acetonitrile is preferably used as the solvent for dissolving the substance having ion conduction characteristics. In addition, for example, a cyanoethylated product such as cyanoresin may be added as a binder to an acetonitrile solution of a substance having ionic conductivity. In this case, it is preferable to mix (blend) the cyanoethylated substance with a mass ratio (weight ratio) of 5 to 0.5 wt% with respect to the substance having ion conduction characteristics.
[0221]
Further, the hole transport layer material preferably contains a hole transport efficiency improving substance having a function of improving the hole transport efficiency. When the hole transport layer material contains this hole transport efficiency improving substance, the hole transport layer 5 has higher carrier mobility due to the improvement of ion conduction characteristics. As a result, the hole transport layer 5 has improved electrical conductivity.
[0222]
The substance for improving hole transport efficiency is not particularly limited, and examples thereof include halides such as ammonium halide, and it is particularly preferable to use ammonium halide such as tetrapropylammonium iodide (TPAI). By using ammonium halide, in particular, tetrapropylammonium iodide, as the substance for improving the hole transport efficiency, the hole transport layer 5 is further improved in ion conduction characteristics, thereby further increasing the carrier mobility. As a result, the hole transport layer 5 is further improved in electrical conductivity.
[0223]
The content of the hole transport efficiency improving substance in the hole transport layer material is not particularly limited, but is 1 × 10^-Four~ 1x10^-1It is preferably about wt% (wt%), 1x10^-Four~ 1x10^-2More preferably, it is about wt%. Within such a numerical range, the above-described effect becomes more remarkable.
[0224]
In addition, when the hole transport layer 5 is composed mainly of a substance having ion conduction characteristics, the hole transport layer material increases in crystal size when the substance having ion conduction characteristics is crystallized. It is preferable to contain a crystal size coarsening-suppressing substance that suppresses this.
[0225]
The substance for suppressing the coarsening of crystal size is not particularly limited, and examples thereof include thiocyanate (rhodanide) in addition to the aforementioned cyanoethylated substance and hole transport efficiency improving substance. Moreover, the crystal size coarsening inhibitor can be used alone or in combination of two or more thereof.
[0226]
As thiocyanate, for example, sodium thiocyanate (NaSCN), potassium thiocyanate (KSCN), copper thiocyanate (CuSCN), ammonium thiocyanate (NH₄SCN) and the like.
[0227]
In addition, when a hole transport efficiency improving substance is used as the crystal size coarsening suppressing substance, ammonium halide is preferable. Among the materials that improve the hole transport efficiency, ammonium halide has a particularly excellent function of suppressing an increase in crystal size of a material having ion conduction characteristics.
[0228]
Here, if the hole transport layer material does not contain this crystal size coarsening suppression substance, the substance having ion conduction characteristics may crystallize depending on the kind of substance having ion conduction characteristics, the heating temperature described above, and the like. In this case, the crystal size becomes too large, and the volume expansion of the crystal may proceed excessively. In particular, when such crystallization occurs in the pores (micropores) of the barrier layer 8, cracks occur in the barrier layer 8, and as a result, a partial transfer occurs between the hole transport layer 5 and the first electrode 3. May cause a short circuit due to contact.
[0229]
Further, when the crystal size of the substance having ion conduction characteristics is increased, the contact property with the light receiving layer 4 may be lowered depending on the kind of the substance having ion conduction characteristics. As a result, the material having ion conduction characteristics, that is, the hole transport layer 5 may be peeled off from the light receiving layer 4.
[0230]
Therefore, such solar cells may have reduced device characteristics such as photoelectric conversion efficiency.
[0231]
On the other hand, when the hole transport layer material contains this crystal size coarsening-suppressing substance, the substance having ion conduction characteristics is suppressed from increasing in crystal size, and the crystal size is extremely small or relatively small. It becomes.
[0232]
For example, when thiocyanate is added to an acetonitrile solution of CuI, thiocyanate ions (SCN) are formed around Cu atoms of CuI dissolved in a saturated state.⁻) Are adsorbed to form Cu—S (sulfur, Sulfor) bonds. As a result, the bonding between CuI molecules dissolved in a saturated state is remarkably inhibited, and as a result, CuI crystal growth can be prevented, so that a finely grown CuI crystal can be obtained.
[0233]
For this reason, the solar cell 1A can suitably suppress the disadvantages caused by the coarsening of the crystal size of the substance having the ion conduction characteristics as described above.
[0234]
Further, the content of the crystal size coarsening inhibitor in the hole transport layer material is not particularly limited, but is 1 × 10.^{- 6}It is preferably about 10 wt% (wt%), or 1 × 10^-Four~ 1x10^-2More preferably, it is about wt%. Within such a numerical range, the above-described effect becomes more remarkable.
[0235]
When the hole transport layer 5 is composed of the p-type semiconductor material as described above, the p-type semiconductor material is made of various organic solvents such as acetone, isopropyl alcohol (IPA), and ethanol (or these). The hole transport layer material is prepared by dissolving (or suspending) in a mixed solvent containing). Using this hole transport layer material, the hole transport layer 5 is formed (formed) in the same manner as described above.
[0236]
<5> Next, the second electrode 6 is formed on the upper surface of the hole transport layer 5.
The second electrode 6 can be formed by using, for example, a vapor deposition method, a sputtering method, a printing method, or the like as the material of the second electrode 6 made of platinum or the like.
Through the steps as described above, the solar cell 1A is manufactured.
[0237]
Next, another manufacturing method of the solar cell 1A will be described.
FIG. 5 is a view (an enlarged cross-sectional view showing a state before joining the light receiving layer and the hole transport layer) for explaining another method for manufacturing the solar cell of the first embodiment. In the following description, in FIG. 5, the upper surface of each layer (each member) is referred to as “upper surface” and the lower surface is referred to as “lower surface”.
[0238]
Hereinafter, another manufacturing method of the solar cell 1A will be described focusing on differences from the manufacturing method described above, and description of similar matters will be omitted.
[0239]
In this method, as shown in FIG. 5, a laminate 12A of a coating film in which a hole transport layer material is applied to the lower surface (one surface) of the second electrode 6, the substrate 2, the first electrode 3, and 1 A of solar cells are manufactured by joining 11 A of laminated layers of the light reception layer 4 so that the light reception layer 4 and the positive hole transport layer 5 may contact.
[0240]
<1 '> to <3'> Steps similar to the steps <1> to <3> are performed. Thereby, the laminated body 11A is obtained.
[0241]
<4 ′> On the other hand, a hole transport layer material is applied to one surface of the second electrode 6 made of, for example, platinum.
[0242]
This can be performed in the same manner as in step <4>. In this case, the heat treatment to the coating film is omitted, and the coating film of the hole transport layer material is not solidified. Thereby, the laminated body 12A is obtained.
[0243]
Hereinafter, the coating film of the hole transport layer material that is not solidified is referred to as a hole transport layer 5.
[0244]
At this time, a plurality of convex portions 51 are formed on the lower surface (the lower surface in FIG. 5) of the hole transport layer 5 and are in an uneven state.
[0245]
<5 ′> Next, the stacked body 11A and the stacked body 12A are joined so that the light receiving layer 4 and the hole transport layer 5 are in contact with each other.
[0246]
Here, in the solar cell in which the barrier layer 8 is not installed, especially when the porosity (degree of porosity) of the light receiving layer 4 is increased, the hole transport layer 5 is separated from each convex portion 51 to the hole of the light receiving layer 4. 41 may penetrate into (infiltrate) 41, penetrate through the light receiving layer 4, and almost all of the convex portions 51 (a part of the hole transport layer 5) may come into contact with the first electrode 3. . Thereby, in such a solar cell, the leakage current increases and the power generation efficiency decreases.
[0247]
On the other hand, in the solar cell 1A, since the barrier layer (short-circuit prevention means) 8 is provided, when the stacked body 12A is brought close to the stacked body 11A from the state shown in FIG. From each convex part 51, it penetrates into the hole 41 of the light receiving layer 4 so as to penetrate (permeate). However, when the hole transport layer 5 reaches the barrier layer 8, the barrier layer 8 prevents further access to the first electrode 3.
[0248]
Further, the surface area (formation region) of the rectifying barrier as described above is increased by joining the hole transport layer 5 so that the hole transport layer 5 penetrates (embeds) into the hole 41 of the light receiving layer 4. be able to. For this reason, it is possible to more efficiently transfer holes generated in the light receiving layer 4 to the hole transport layer 5.
[0249]
Therefore, in such a solar cell 1A, generation of leakage current is prevented or suppressed, and power generation efficiency (photoelectric conversion efficiency) is improved.
[0250]
Second Embodiment
Next, the solar cell of 2nd Embodiment is demonstrated.
[0251]
FIG. 6 is a cross-sectional view showing the configuration of the solar cell of the second embodiment, and FIG. 7 is a diagram for explaining the method of manufacturing the solar cell of the second embodiment (joining the light receiving layer and the hole transport layer). It is an expanded sectional view showing a previous state. In the following description, in FIG. 6 and FIG. 7, the upper surface of each layer (each member) is referred to as “upper surface” and the lower surface is referred to as “lower surface”.
[0252]
Hereinafter, the solar cell 1 </ b> B illustrated in FIG. 6 will be described with a focus on differences from the first embodiment, and description of similar matters will be omitted.
[0253]
In the solar cell 1B of the second embodiment, a spacer is provided as a short-circuit preventing means instead of the barrier layer, and other than that, the solar cell 1B is the same as the solar cell 1A of the first embodiment.
[0254]
That is, the spacer 7 is provided between the first electrode 3 and the second electrode 6 so as to surround the light receiving layer 4 and the hole transport layer 5.
[0255]
The spacer 7 defines the distance between the first electrode 3 and the hole transport layer 5 (maintains constant).
[0256]
Such a spacer 7 is made of an insulating material. As this insulating material, for example, one kind or a combination of two or more of a photo-curing resin such as an ultraviolet curable resin and a thermosetting resin such as an epoxy resin can be used.
[0257]
The spacer 7 may not be configured to cover the entire circumference of the light receiving layer 4 and the hole transport layer 5 as long as the distance between the first electrode 3 and the hole transport layer 5 can be defined. For example, a configuration in which a sphere, a rod-like body (for example, a cross-sectional shape is a circle, an ellipse, a polygon such as a triangle, a quadrangle, etc.) or the like may be disposed around them. .
[0258]
This solar cell 1B can be manufactured through substantially the same manufacturing process as the solar cell 1A of the first embodiment (see other manufacturing method of the first embodiment). In this case, in the final process, 2, a laminate 11B composed of the first electrode 3, the light-receiving layer 4 and the spacer 7, and a laminate 12B composed of a coating film (hole transport layer 5) of the hole transport layer material and the second electrode 6, The light receiving layer 4 and the coating film of the hole transport layer material are joined so as to be in contact with each other.
[0259]
Here, in the solar cell in which the spacer 7 is not installed, when the porosity (degree of porosity) of the light-receiving layer 4 is increased, the hole transport layer 5 moves from each convex portion 51 to the hole 41 of the light-receiving layer 4. Intrusion (penetration) into the inside, and further penetrates the light receiving layer 4, so that almost all of the convex portions 51 (a part of the hole transport layer 5) may come into contact with the first electrode 3. Thereby, in such a solar cell, the leakage current increases and the power generation efficiency decreases.
[0260]
On the other hand, since the spacer (short-circuit prevention means) 7 is provided in the solar cell 1B, when the stacked body 12B is brought close to the stacked body 11B from the state shown in FIG. From the convex portion 51, the light enters into the hole 41 of the light receiving layer 4 so as to penetrate (permeate). However, when the upper surface of the spacer 7 and the lower surface of the second electrode 6 come into contact with each other, the stacked body 12B and the stacked body 11B are further prevented from approaching each other. At this time, the hole transport layer 5 is sufficiently infiltrated into the hole 41 of the light receiving layer 4.
[0261]
The average thickness (length H in FIG. 7) of the spacer 7 is set to such a size that the hole transport layer 5 (convex portion 51) does not contact the first electrode 3.
[0262]
For this reason, in the solar cell 1B, the contact of the hole transport layer 5 with the first electrode 3 is prevented or suppressed. Therefore, in such a solar cell 1B, generation | occurrence | production of a leakage current is prevented or suppressed, and electric power generation efficiency (photoelectric conversion efficiency) improves.
[0263]
From such a viewpoint, the average thickness H of the spacer 7, the maximum thickness of the hole transport layer 5 (length h1 in FIG. 7), and the maximum thickness of the light receiving layer 4 (length h2 in FIG. 7) For example, it is preferable that the relationship h1 + h2> H ≧ h1 is satisfied, and it is more preferable that the relationship 1.1h1 ≧ H ≧ h1 is satisfied. By setting the average thickness H of the spacer 7 within the above range, the hole transport layer 5 is preferably prevented or suppressed from being short-circuited due to contact between the first electrode 3 and the hole transport layer 5. And a sufficient contact area between the light receiving layer 4 can be secured.
[0264]
In this embodiment, a barrier layer having the same configuration as that of the barrier layer 8 described in the first embodiment is provided below the light receiving layer 4 (between the light receiving layer 4 and the first electrode 3). Thus, the effect can be further improved.
[0265]
As mentioned above, although the photoelectric conversion element of this invention was demonstrated based on each embodiment of illustration, this invention is not limited to this. Each unit constituting the photoelectric conversion element can be replaced with any component that can exhibit the same function.
[0266]
The photoelectric conversion element of the present invention may be a combination of any two or more configurations of the first and second embodiments.
[0267]
The photoelectric conversion element of the present invention can be applied not only to solar cells but also to various elements (light receiving elements) that receive light and convert it into electrical energy, such as optical sensors and optical switches. It is.
[0268]
Moreover, in the photoelectric conversion element of this invention, the incident direction of light may be from the reverse direction unlike the thing of illustration. That is, the incident direction of light is arbitrary.
[0269]
【Example】
Next, specific examples of the present invention will be described.
[0270]
Example 1
The solar cell shown in FIG. 1 was manufactured as follows.
[0271]
First, a soda glass substrate having dimensions: 30 mm long × 35 mm wide × 1.0 mm thick was prepared. Next, this soda glass substrate was cleaned by immersing it in a cleaning solution (mixed solution of sulfuric acid and hydrogen peroxide solution) at 85 ° C. to clean the surface.
[0272]
-1- Next, an FTO electrode (first electrode) having dimensions: length 30 mm × width 35 mm × thickness 1 μm was formed on the upper surface of the soda glass substrate by vapor deposition.
[0273]
-2- Next, a barrier layer was formed in an area of 30 mm length × 30 mm width on the upper surface of the formed FTO electrode. This was done as follows.
[0274]
[Preparation of barrier layer material]
First, titanium tetraisopropoxide (organic titanium compound) was dissolved in 2-n-butoxyethanol so as to be 0.5 mol / L.
[0275]
Then, diethanolamine (additive) was added to this solution. The mixing ratio of diethanolamine and titanium tetraisopropoxide was 2: 1 (molar ratio).
[0276]
Thereby, a barrier layer material was obtained. The barrier layer material had a viscosity of 3.3 cP (normal temperature).
[0277]
[Formation of barrier layer]
The barrier layer material was applied by spin coating (coating method) to obtain a coating film. This spin coating was performed at a rotation speed of 1500 rpm.
[0278]
Subsequently, the laminated body of the soda glass substrate, the FTO electrode, and the coating film was placed on a hot plate, and the coating film was dried by heat treatment at 160 ° C. for 10 minutes.
[0279]
Further, the laminate was subjected to heat treatment in an oven at 480 ° C. for 30 minutes to remove organic components remaining in the coating film.
Such an operation was repeated 10 times to laminate.
[0280]
Thereby, a barrier layer having a porosity of less than 1% was obtained. The average thickness of this barrier layer was 1.2 μm.
[0281]
-3- Next, a light receiving layer was formed on the upper surface (entire) of the barrier layer. This was done as follows.
[0282]
[Preparation of titanium oxide powder]
A titanium oxide powder comprising a mixture of a rutile type titanium dioxide powder subjected to oxygen defect formation by performing a heat treatment at 1000 ° C. for 0.5 hour in a hydrogen atmosphere and an anatase type titanium dioxide powder was prepared. . The average particle diameter of the titanium oxide powder was 40 nm, and the mixing ratio of the rutile type titanium dioxide powder and the anatase type titanium dioxide powder was 60:40 by weight.
[0283]
[Preparation of sol solution (light-receiving layer material)]
First, titanium tetraisopropoxide was dissolved in 2-propanol so as to be 1 mol / L.
[0284]
Next, acetic acid (additive) and distilled water were mixed with this solution. The mixing ratio of acetic acid and titanium tetraisopropoxide is 1: 1 (molar ratio), and the mixing ratio of distilled water and titanium tetraisopropoxide is 1: 1 (molar ratio). It was made to become.
[0285]
Subsequently, the prepared titanium oxide powder was mixed with this solution. Further, this suspension was diluted 2-fold with 2-propanol. Thus, a sol solution (light receiving layer material) was prepared.
The content of titanium oxide powder in the sol liquid was 3 wt%.
[0286]
[Formation of light-receiving layer]
The laminated body of the soda glass substrate, the FTO electrode, and the barrier layer was placed on a hot plate heated to 140 ° C., and a sol solution (light receiving layer material) was dropped onto the upper surface of the barrier layer (coating method) and dried. This operation was repeated 7 times to laminate.
[0287]
As a result, a light receiving layer having a porosity of 36% was obtained. The light receiving layer had an average thickness of 8.5 μm.
[0288]
The resistance value in the thickness direction of the entire barrier layer and light receiving layer is 1 kΩ / cm.²That was all.
[0289]
-4- Next, the laminated body of the soda glass substrate, the FTO electrode and the light receiving layer was placed on a hot plate heated to 80 ° C., and an acetonitrile solution of CuI (hole transport layer material) was dropped on the upper surface of the light receiving layer. And dried. By repeating this operation, a CuI layer (hole transport layer) having dimensions of 30 mm in length, 30 mm in width, and 30 μm in thickness was formed.
[0290]
In the acetonitrile solution, tetrapropylammonium iodide was added at 1 × 10 6 as a hole transport efficiency improving substance.^-3It added so that it might become wt%.
[0291]
Further, cyanoresin (cyanoethylated product) was added to the acetonitrile solution as a CuI binder. CuI and cyanoresin were blended so that the mass ratio (weight ratio) was 97: 3.
[0292]
Further, in the acetonitrile solution, sodium thiocyanate (NaSCN) is used as a crystal size coarsening inhibitor.^-3It added so that it might become wt%.
[0293]
−5- Next, a platinum electrode (second electrode) having dimensions: 30 mm long × 30 mm wide × 0.1 mm thick was formed on the upper surface of the CuI layer by vapor deposition.
[0294]
(Example 2)
Using the barrier layer material shown below, a solar cell was produced in the same manner as in Example 1 except that the operation in forming the barrier layer was repeated twice and the titanium oxide powder shown below was used. did.
[0295]
-2- Formation of barrier layer
[Preparation of barrier layer material]
First, titanium tetrachloride (inorganic titanium compound) was dissolved in absolute ethanol so as to be 1.0 mol / L.
[0296]
Thereby, a barrier layer material was obtained. The viscosity of the barrier layer material was 1.2 cP (normal temperature).
[0297]
The obtained barrier layer had a porosity of less than 1% and an average thickness of 2.0 μm.
[0298]
-3- Formation of light receiving layer
[Preparation of titanium oxide powder]
A titanium oxide powder made of a mixture of a rutile type titanium dioxide powder and an anatase type titanium dioxide powder was prepared. The average particle diameter of the titanium oxide powder was 40 nm, and the mixing ratio of the rutile type titanium dioxide powder and the anatase type titanium dioxide powder was 60:40 by weight.
[0299]
Next, the titanium oxide powder was subjected to an oxygen defect formation method by performing a heat treatment at 1000 ° C. for 0.5 hours in a hydrogen atmosphere.
[0300]
In addition, the obtained light receiving layer had a porosity of 34% and an average thickness of 7.5 μm.
[0301]
In the obtained light receiving layer, rutile type titanium dioxide and anatase type titanium dioxide were present at 70:30.
[0302]
The resistance value in the thickness direction of the entire barrier layer and light receiving layer is 1 kΩ / cm.²That was all.
[0303]
(Example 3)
Using the barrier layer material shown below, the operation in forming the barrier layer was repeated three times, and in place of the titanium oxide powder, a film-like body (coating film) was subjected to an oxygen defect formation method, A solar cell was manufactured in the same manner as in Example 1.
[0304]
-2- Formation of barrier layer
[Preparation of barrier layer material]
First, titanium oxyacetylacetonate (organic titanium compound) was dissolved in 2-butanol so as to be 1.5 mol / L.
[0305]
Thereby, a barrier layer material was obtained. The viscosity of the barrier layer material was 1.5 cP (normal temperature).
[0306]
The obtained barrier layer had a porosity of less than 1% and an average thickness of 3.4 μm.
[0307]
-3- Formation of light receiving layer
[Preparation of sol solution (light-receiving layer material)]
A sol solution (light-receiving layer material) was prepared in the same manner as in Example 1.
[0308]
In addition, in order to give an oxygen defect formation method with respect to a film-form body (coating film), the heat processing by the oxygen defect formation method to a titanium oxide powder was abbreviate | omitted.
[0309]
[Formation of light-receiving layer]
By forming a film-like body (coating film) in the same manner as in Example 1, and then subjecting the film-like body to heat treatment (oxygen defect formation method) at 1000 ° C. for 0.5 hours in a hydrogen atmosphere. A light receiving layer was obtained.
[0310]
In addition, the obtained light receiving layer had a porosity of 32% and an average thickness of 6.7 μm.
[0311]
In the obtained light-receiving layer, rutile type titanium dioxide and anatase type titanium dioxide were present at 75:25.
[0312]
The resistance value in the thickness direction of the entire barrier layer and light receiving layer is 1 kΩ / cm.²That was all.
[0313]
Example 4
Using the barrier layer material shown below, the operation in the formation of the barrier layer was repeated 5 times, and the atomic substitution method was used in place of the oxygen defect formation method. A solar cell was manufactured.
[0314]
-2- Formation of barrier layer
[Preparation of barrier layer material]
First, titanium tetraisopropoxide (organic titanium compound) was dissolved in 2-propanol so as to be 2.0 mol / L.
[0315]
To this solution was then added acetic acid (additive). The mixing ratio of acetic acid and titanium tetraisopropoxide was 1: 1 (molar ratio).
[0316]
Thereby, a barrier layer material was obtained. The barrier layer material had a viscosity of 1.7 cP (normal temperature).
[0317]
The obtained barrier layer had a porosity of less than 1% and an average thickness of 4.5 μm.
[0318]
-3- Formation of light receiving layer
[Preparation of sol solution (light-receiving layer material)]
Dichromium trioxide (inorganic sensitizer) and molybdenum trioxide (sintering aid) are mixed with the undiluted suspension prepared in the same manner as in Example 1, and the suspension is diluted. Thus, a sol solution (light-receiving layer material) was prepared. The mixing ratio of dichromium trioxide and molybdenum trioxide is as follows.
[0319]
<Dichromium trioxide> 0.9 μmol with respect to 1 g of titanium oxide powder
<Molybdenum trioxide> Titanium oxide powder: Molybdenum trioxide = 90: 10 (volume ratio)
[0320]
[Formation of light-receiving layer]
A film-like body (coating film) was formed in the same manner as in Example 3, and then the film-like body was baked in the atmosphere at 800 ° C. for 3 hours to obtain a light receiving layer.
[0321]
In addition, the obtained light receiving layer had a porosity of 33% and an average thickness of 6.9 μm.
[0322]
The resistance value in the thickness direction of the entire barrier layer and light receiving layer is 1 kΩ / cm.²That was all.
[0323]
(Example 5)
A solar cell (photoelectric conversion element) shown in FIG. 6 having a spacer instead of the barrier layer was produced in the same manner as in Example 1.
[0324]
-0'-, -1'- Performed in the same manner as in Steps 0-0 and -1- of Example 1.
[0325]
-2'- Next, a light receiving layer was formed in an area of 30 mm length × 30 mm width on the upper surface of the formed FTO electrode. This was performed in the same manner as in step 3-3 in Example 1.
[0326]
As a result, a light-receiving layer having a porosity of 34% was obtained. The maximum thickness of the light receiving layer was 10.5 μm. The resistance value in the thickness direction of the light receiving layer is 20 Ω / cm.²Met.
[0327]
-3'- Next, the outer edge portion of the light receiving layer was surrounded by epoxy resin (spacer material) and then solidified.
[0328]
This obtained the laminated body of the soda glass substrate, the FTO electrode, the light receiving layer, and the spacer. The spacer had an average thickness of 31.0 μm.
[0329]
-4'- Next, an acetonitrile solution (a hole transport layer material) of CuI was applied to a region 30 mm long by 30 mm wide on one surface of the platinum electrode (second electrode). This was performed in the same manner as in Step-5--5 of Example 1, but the heat treatment was omitted.
[0330]
Thereby, the laminated body of the platinum electrode and the CuI coating film (CuI layer) was obtained. The maximum thickness of this CuI layer was 30.1 μm.
[0331]
-5'- Next, the laminates were bonded so that the light receiving layer and the CuI layer were in contact with each other.
[0332]
(Comparative example)
A solar cell was manufactured in the same manner as in Example 1 except that the barrier layer (short-circuit prevention means) was omitted.
[0333]
In addition, the obtained light receiving layer had a porosity of 34% and an average thickness of 10.2 μm.
The resistance value in the thickness direction of the light receiving layer is 20 Ω / cm.²Met.
[0334]
(Evaluation 1)
In the solar cells manufactured in Examples 1 to 5 and the comparative example, the resistance values were measured when a voltage of 0.5 V was applied so that the FTO electrode was positive and the platinum electrode was negative.
[0335]
(Evaluation 2)
The solar cells manufactured in Examples 1 to 5 and the comparative example were each irradiated with light from an artificial solar lamp, and the photoelectric conversion efficiency at this time was measured. The incident angle of light to the light receiving layer is set to 90 ° and 52 °, and the photoelectric conversion efficiency when the incident angle of light is 90 ° is R₉₀And the photoelectric conversion efficiency at 52 ° is R₅₂It was.
The results of Evaluation 1 and Evaluation 2 are shown in Table 1.
[0336]
[Table 1]

[0337]
From the results shown in Table 1, in the solar cells (Examples 1 to 5) having the short-circuit prevention means (barrier layer or spacer), the short-circuit due to contact between the FTO electrode and the CuI layer is suitably prevented or suppressed. The photoelectric conversion efficiency was excellent.
[0338]
On the other hand, in the solar cell of the comparative example in which the barrier layer (short-circuit preventing means) is omitted, the photoelectric conversion efficiency is inferior.
[0339]
The reason why the photoelectric conversion efficiency is inferior in the comparative example is considered to be caused by the occurrence of leakage current due to a short circuit (contact) between the FTO electrode and the CuI layer, as is clear from the result of Evaluation 1.
[0340]
Moreover, as for the solar cell of Examples 1-5, all are R₅₂/ R₉₀Is 0.85 or more, and this indicates that the solar cells of Examples 1 to 5 have lower directivity to light.
[0341]
【The invention's effect】
As described above, according to the present invention, by providing the short-circuit prevention means, it is possible to efficiently prevent or suppress a short-circuit due to contact or the like between the first electrode and the hole transport layer, and efficiently. Electrons can be generated, and as a result, extremely excellent photoelectric conversion efficiency can be obtained.
[0342]
By using a sol-gel method using a sol liquid containing powder of the light receiving layer material, the light receiving layer can be formed more easily and reliably.
[0343]
In addition, when a barrier layer is provided as a short-circuit prevention means, the barrier layer can be formed more easily and reliably by using the MOD method.
The photoelectric conversion element of the present invention is easy to manufacture and can be manufactured at low cost.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view showing a first embodiment when a photoelectric conversion element of the present invention is applied to a solar cell.
FIG. 2 is an enlarged view showing a cross section in the vicinity of the central portion in the thickness direction of the solar cell of the first embodiment.
FIG. 3 is a partially enlarged view showing a cross section of a light receiving layer.
4 is a diagram showing an equivalent circuit of the solar cell circuit shown in FIG. 1. FIG.
FIG. 5 is a view (an enlarged cross-sectional view showing a state before joining a light receiving layer and a hole transport layer) for explaining another method for manufacturing the solar cell of the first embodiment.
FIG. 6 is a cross-sectional view showing a configuration of a solar cell according to a second embodiment.
FIG. 7 is a view (an enlarged cross-sectional view showing a state before joining a light receiving layer and a hole transport layer) for explaining a method for manufacturing a solar cell according to a second embodiment.
[Explanation of symbols]
1A, 1B ... Solar cell 2 ... Substrate 3 ... First electrode 4 ... Light receiving layer 41 ... Hole 5 ... Hole transport layer 51 ... Projection 6 ... Second electrode 7 ... Spacer 8 ... Barrier layer 11A ... Laminated body 12A ... Laminated body 11B ... Laminated body 12B ... Laminated body 100 ... External circuit 200 ... Diode

Claims (19)

A first electrode;
A second electrode disposed opposite the first electrode;
A light-receiving layer located between the first electrode and the second electrode, at least a portion of which is porous;
A hole transport layer located between the light receiving layer and the second electrode;
A photoelectric conversion element in which a rectifying barrier is formed at an interface between the light receiving layer and the hole transport layer,
As a short-circuit prevention means for preventing or suppressing a short circuit between the first electrode and the hole transport layer, electrical conductivity equivalent to that of the light receiving layer is provided between the first electrode and the light receiving layer. Having a barrier layer having a porosity of 2% or less,
The thickness ratio between the barrier layer and the light receiving layer is 1:99 to 40:60, and the barrier layer has a porosity smaller than the porosity of the light receiving layer. When the porosity of the layer is A [%] and the porosity of the light receiving layer is B [%], B / A is 10 or more,
The barrier layer is mainly composed of titanium oxide formed by a sol-gel method using a barrier layer material containing titanium alkoxide,
The light-receiving layer comprises a titanium alkoxide, which is formed by the sol-gel method using a light-receiving layer material containing titanium oxide powder is composed mainly of titanium oxide,
The hole transport layer is mainly composed of a metal iodide compound which is a substance having ion conduction characteristics, and a hole transport layer material containing the substance having ion conduction characteristics is applied onto the dye layer by a coating method. Formed by coating,
The hole transport layer material contains thiocyanate as a crystal size coarsening inhibitor having a function of suppressing an increase in crystal size when the metal iodide compound is crystallized. Photoelectric conversion element. The crystal size coarse suppressing substance, by binding to the metal atom of the metal iodide compound, when the metal iodide compound crystallizes, according to suppress claim 1 that the crystal size increases Photoelectric conversion element. A first electrode;
  A second electrode disposed opposite the first electrode;
  A light-receiving layer located between the first electrode and the second electrode, at least a portion of which is porous;
  A hole transport layer located between the light receiving layer and the second electrode;
  A photoelectric conversion element in which a rectifying barrier is formed at an interface between the light receiving layer and the hole transport layer,
  As a short-circuit prevention means for preventing or suppressing a short circuit between the first electrode and the hole transport layer, electrical conductivity equivalent to that of the light receiving layer is provided between the first electrode and the light receiving layer. Having a barrier layer having a porosity of 2% or less,
  The thickness ratio between the barrier layer and the light receiving layer is 1:99 to 40:60, and the barrier layer has a porosity smaller than the porosity of the light receiving layer. When the porosity of the layer is A [%] and the porosity of the light receiving layer is B [%], B / A is 10 or more,
  The barrier layer is mainly composed of titanium oxide formed by a sol-gel method using a barrier layer material containing titanium alkoxide,
  The light receiving layer is mainly composed of titanium oxide formed by a sol-gel method using a light receiving layer material containing titanium alkoxide and titanium oxide powder,
  The hole transport layer is mainly composed of a metal iodide compound which is a substance having ion conduction characteristics, and a hole transport layer material containing the substance having ion conduction characteristics is applied onto the dye layer by a coating method. Formed by coating,
  The hole transport layer material contains an ammonium halide as a hole transport efficiency improving substance having a function of improving hole transport efficiency. 4. The photoelectric conversion element according to claim 1, wherein the barrier layer is formed by a MOD (Metal Organic Deposition or Metal Organic Decomposition) method. The photoelectric conversion element according to claim 4 , wherein a barrier layer material used when forming the barrier layer by the MOD method includes a titanium alkoxide and an additive having a function of stabilizing the titanium alkoxide. The photoelectric additive according to claim 5 , wherein the additive is a hydrolysis inhibitor that inhibits hydrolysis of the titanium alkoxide by substituting for an alkoxyl group of the titanium alkoxide and coordinates to a titanium atom of the titanium alkoxide. Conversion element. The photoelectric conversion device according to any one of the resistance value in the thickness direction in the entire of the light receiving layer and the barrier layer claims 1 is 100 [Omega / cm ² or more and 6. An interface between the light-receiving layer and the barrier layer, the photoelectric conversion device according to any one of claims 1 to 7 is uncertain. Wherein A barrier layer and the light-receiving layer, the photoelectric conversion device according to any one of claims 1 to 8 are integrally formed. Some of the light receiving layer, the photoelectric conversion device according to any one of claims 1 to 9 functioning as the barrier layer. The light receiving layer, the photoelectric conversion element according to any one of claims 1 visualization process that enables light absorption in the wavelength of visible light region is applied 10. The light receiving layer, the photoelectric conversion device according to any one of claims 1 to 11 formed into a film shape. The titanium oxide powder is a photoelectric conversion device according to any one of claims 1 to 12 average particle size of from 1 nm to 1 [mu] m. The photoelectric conversion element according to any one of claims 1 to 13 , wherein a content of the titanium oxide powder in the light receiving layer material is 0.1 to 10% by weight. The light receiving layer, the photoelectric conversion device according to any one of constituted claims 1 to 14 mainly titanium dioxide. The photoelectric conversion element according to claim 1 , wherein the hole transport layer is formed by applying the hole transport layer material onto the light receiving layer while heating the light receiving layer. . The photoelectric conversion device according to any one of claims 1 to 16 having a substrate supporting the first electrode. The first electrode is positive, as the second electrode is negative, when applying a voltage of 0.5V, the resistance value of claims 1 to 17 having the property of a 100 [Omega / cm ² or more The photoelectric conversion element in any one. The photoelectric conversion device according to any one of claims 1 to 18, which is a solar cell.

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