JP2016162890A - Photoelectric conversion element, photoelectric conversion device and method for manufacturing photoelectric conversion element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion element having a high photoelectric conversion efficiency.SOLUTION: A photoelectric conversion element 100 includes: an electron transport layer 110 containing a dopant; a hole transport layer 130 containing an additive material acting as a hole acceptor; metal bodies 150 disposed to be separated as islands, along an interface between the electron transport layer 110 and the hole transport layer 130. When light is applied from a side of the hole transport layer 130, electronic vibration (plasmon resonance) is induced in each island of the metal bodies 150, charge separation is caused in each island of the metal bodies 150, and photoelectric conversion is performed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a photoelectric conversion element, a photoelectric conversion device, and a method for manufacturing a photoelectric conversion element.

  In recent years, environmental problems and energy problems have become apparent on a global scale, and research on the construction of photoenergy conversion systems such as photocatalysts and solar cells has attracted attention. Silicon solar cells are widely used as a kind of such light energy conversion systems.

  However, the theoretical limit of the photoelectric conversion efficiency of this silicon solar cell is about 30%, and it is difficult to say that the silicon solar cell is highly efficient energy conversion. Further, as solar cells, dye-sensitized solar cells and tandem solar cells in which semiconductors having different band gaps are stacked have been developed. These solar cells have a wavelength range capable of photoelectric conversion. There is a problem that it is limited or a manufacturing process becomes complicated.

  The present inventors have succeeded in the construction of a wet photoelectric conversion system (Patent Document 1) and a solid solar cell (Patent Document 2) using localized surface plasmons so far.

International Publication No. 2011/027830 JP 2014-67988 A

  However, in the photoelectric conversion device described in Patent Document 2, it is difficult to say that the characteristics of each component, particularly the hole transport layer, are sufficient from the viewpoint of material science. For this reason, the photoelectric conversion efficiency described in Patent Document 2 is still insufficient.

  The present invention has been made in view of such a background, and an object of the present invention is to provide a photoelectric conversion element having higher photoelectric conversion efficiency. Another object of the present invention is to provide a photoelectric conversion device having such a photoelectric conversion element. Furthermore, an object of the present invention is to provide a method for producing such a photoelectric conversion element.

In the present invention,
An electron transport layer containing a dopant;
A hole transport layer including an additive disposed so as to contact the electron transport layer and acting as a hole acceptor;
A metal body arranged in an island shape along the interface between the electron transport layer and the hole transport layer, and
A photoelectric conversion element is provided.

Further, in the present invention, a photoelectric conversion element having the characteristics as described above,
A first conductive member electrically connected to the electron transport layer;
A second conductive member electrically connected to the hole transport layer;
A photoelectric conversion device is provided.

Furthermore, in the present invention, a method for producing a photoelectric conversion element,
(1) providing an electron transport layer containing a dopant;
(2) A step of separating and arranging a metal body in an island shape on the electron transport layer;
(3) forming a hole transport layer on the electron transport layer so as to cover the metal body;
Have
The hole transport layer includes a manufacturing method of a photoelectric conversion element including an additive that acts as a hole acceptor.

  In the present invention, a photoelectric conversion element having higher photoelectric conversion efficiency can be provided. In the present invention, a photoelectric conversion device having such a photoelectric conversion element can be provided. Furthermore, in this invention, the manufacturing method of such a photoelectric conversion element can be provided.

It is the figure which showed typically an example of the cross section of the photoelectric conversion element by one Embodiment of this invention. It is the figure which showed typically an example of the cross section of a photoelectric conversion apparatus provided with the photoelectric conversion element by one Embodiment of this invention. It is the flowchart which showed typically an example of the manufacturing method of the photoelectric conversion element by one Embodiment of this invention. 2 is a photograph showing an example of a surface form of a titanium oxide substrate in Example 1. FIG. 3 is a diagram illustrating an example of a current-voltage curve obtained in the photoelectric conversion device according to Example 1. FIG. 6 is a diagram showing an example of a current-voltage curve obtained in the photoelectric conversion device according to Example 2. FIG. It is the figure which showed an example of the current-voltage curve obtained in the photoelectric conversion apparatus which concerns on the comparative example 1. FIG. It is the figure which showed collectively the relationship between the wavelength calculated in each photoelectric conversion apparatus, and internal conversion efficiency IPCE (%).

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

(Photoelectric Conversion Element According to One Embodiment of the Present Invention)
In FIG. 1, an example of the cross section of the photoelectric conversion element by one Embodiment of this invention is typically shown.

  As shown in FIG. 1, the photoelectric conversion element 100 includes an electron transport layer 110, a hole transport layer 130, and a metal body 150.

  The electron transport layer 110 has a first surface 112 and a second surface 114. The electron transport layer 110 is made of, for example, an electron transporter including a dopant, for example, an n-type semiconductor. A hole transport layer 130 is disposed on the first surface 112 of the electron transport layer 110. In addition, the metal body 150 is disposed between the electron transport layer 110 and the hole transport layer 130 in an island shape. Each island of the metal body 150 is configured with fine dimensions, for example, dimensions on the order of nanometers.

  Next, the operation of the photoelectric conversion element 100 will be described.

  In the photoelectric conversion element 100, when light is irradiated from the hole transport layer 130 side, electronic vibration (plasmon resonance) is induced in each island of the metal body 150. This also causes charge separation in each island of the metal body 150, generating electrons and holes. Electrons generated by the charge separation move to the conduction band (conduction band) of the electron transport layer 110, and the holes move to the valence band of the hole transport layer 130. As a result, when the photoelectric conversion element 100 is connected to an external load, a photocurrent that circulates between the electron transport layer 110 and the hole transport layer 130 can be generated.

  In particular, in the photoelectric conversion element 100, the metal bodies 150 are arranged in a fine island shape. Therefore, the metal body 150 can collect light of various wavelengths and functions as an optical antenna that localizes and amplifies the collected light.

  For example, when the size and / or arrangement of the metal body 150 is controlled so that the plasmon resonance wavelength of the metal body 150 is in the visible light region or the near infrared light region, the electron transport layer 110 alone is transmitted. It is possible to advance the photoelectric conversion reaction using light having such a wavelength. In addition, if the configuration of the metal body 150 is designed so that the plasmon resonance wavelength matches the wavelength band of solar energy, it is possible to convert solar energy into electric energy more efficiently.

  Here, in the photoelectric conversion element 100, the hole transport layer 130 has a feature of including an additive that acts as a hole acceptor.

  In the hole transport layer 130 including such an additive, holes generated by charge separation in each island can be more effectively drawn out toward the hole transport layer 130 than in a hole transport layer including no additive. it can. Further, the carrier (hole) concentration itself in the hole transport layer 130 can be increased by the additive contained in the hole transport layer 130, thereby improving the hole transport efficiency.

  Similarly, in the photoelectric conversion element 100, the electron transport layer 110 contains a dopant. For this reason, when the photoelectric conversion element 100 is operated, electrons generated by charge separation in each island of the metal body 150 can be more effectively drawn out to the electron transport layer 110 side. In addition, the carrier (electron) concentration in the electron transport layer 110 can be increased.

  In the present photoelectric conversion element 100, the photoelectric conversion efficiency can be significantly increased as compared with the conventional photoelectric conversion element due to such effects.

In particular, in the photoelectric conversion element 100, by adjusting the amount of the additive in the hole transport layer 130 and the amount of the dopant in the electron transport layer 110, the open-circuit voltage (V _OC ) and the short-circuit current of the photoelectric conversion element 100 can be relatively easily adjusted. Etc. can be controlled. Furthermore, in the photoelectric conversion element 100, it is possible to easily optimize the photoelectric conversion efficiency for light having a desired wavelength.

(Constituent Member of Photoelectric Conversion Element According to One Embodiment of the Present Invention)
Next, each component included in the photoelectric conversion element according to the embodiment of the present invention will be described in more detail. Here, as an example, each constituent member will be described using the configuration of the photoelectric conversion element 100 illustrated in FIG. 1 as an example. Therefore, when referring to each constituent member, the reference numerals used in FIG. 1 are used. However, it will be apparent to those skilled in the art that the following description can be similarly applied to photoelectric conversion elements having other configurations according to the present invention.

(Metal body 150)
As described above, the metal body 150 is arranged in an “island shape” between the electron transport layer 110 and the hole transport layer 130. That is, the metal body 150 is arranged as a plurality of fine islands when the photoelectric conversion element 100 is viewed from the upper surface (the second surface side of the electron transport layer 110).

  The dimension when each island is viewed from above (hereinafter referred to as “maximum dimension”) is, for example, in the range of 1 nm to 200 nm. The “maximum dimension” of each island is preferably in the range of 10 nm to 100 nm, for example.

  Moreover, the three-dimensional form of each island of the metal body 150 is not particularly limited. Each island has, for example, a substantially hemispherical shape, a substantially cylindrical shape, a substantially elliptical columnar shape, a substantially prismatic shape (for example, a triangular prism, a quadrangular column, or a polygonal column (pentagonal prism, hexagonal column ...)), a substantially conical shape, and a substantially elliptical cone shape. The shape may be a substantially pyramid (for example, a triangular pyramid, a quadrangular pyramid, or a polygonal pyramid (pentagonal pyramid, hexagonal pyramid ...)).

  The height of each island is not particularly limited, but may be in the range of 1 nm to 50 nm, for example.

  It should be noted that the shape and / or dimensions of an island having the metal body 150 may be different from the shapes and / or dimensions of other islands. Moreover, each island of the metal body 150 may be arrange | positioned at a periodic pattern, or may be arrange | positioned at random.

  The coverage of the metal body 150 is preferably in the range of 20% to 50%. Here, the coverage of the metal body 150 represents the ratio of the area occupied by the metal body 150 to the active region, that is, the area contributing to the photoelectric conversion reaction of the first surface 112 of the electron transport layer 110.

  The configuration of the metal body 150 (material, dimensions of each island, island arrangement pattern, etc.) is not particularly limited as long as it has plasmon resonance absorption with respect to predetermined incident light. Here, the plasmon resonance absorptivity means a property that enhances an electric field by resonating with incident light and localizing the light, thereby causing a so-called localized surface plasmon phenomenon.

  The metal body 150 may be made of at least one material selected from the group of gold, silver, copper, platinum, aluminum, and alloys thereof, for example.

  Note that the islands of the metal body 150 are not necessarily made of the same material. For example, the first island may be made of a first material (for example, gold), and the second island may be made of a second material (for example, silver).

  With such a configuration, the bandwidth that can be used in the photoelectric conversion element is widened, and it is possible to significantly use light having various wavelengths.

(Hall transport layer)
The structure of the hole transport layer 130 is not particularly limited as long as it is a layer that can draw holes generated by plasmon resonance in the metal body 150.

  However, the hole transport layer 130 is preferably composed of a p-type semiconductor. When the hole transport layer 130 is formed of a p-type semiconductor, the hole transport to the hole transport layer 130 can be made efficient, and the photoelectric conversion efficiency is improved.

  Examples of such a p-type semiconductor include, but are not limited to, at least one of nickel oxide, cobalt oxide, copper iodide, and gallium nitride. Since these materials have a wide band gap, they are transparent to visible light, and have a feature that the valence band upper end position is large on the positive side and a relatively large photovoltaic force can be obtained upon light irradiation.

  The thickness of the hole transport layer 130 may be in the range of 5 nm to 1000 nm, for example.

  On the other hand, the additive contained in the hole transport layer 130 is not particularly limited as long as it is a material that functions as a hole acceptor. The additive may include, for example, at least one of lithium, boron, and aluminum.

The amount of the additive is not particularly limited as long as it is contained in a small amount in the hole transport layer 130. However, the content of the additive in the hole transport layer 130 is preferably 0.001 wt% or more and 0.01 wt% or less with respect to the total weight of the hole transport layer 130. If the content of the additive is less than 0.001% by weight, a sufficient carrier (hole) concentration may not be obtained in the hole transport layer 130, and the hole transport efficiency may decrease. On the other hand, when the content of the additive exceeds 0.01% by weight, the charge separation efficiency may decrease and the open circuit voltage (V _OC ) of the photoelectric conversion element 100 may decrease.

  The content of the additive in the hole transport layer 130 is more preferably in the range of 0.002 wt% to 0.006 wt% with respect to the total weight of the hole transport layer 130.

(Electron transport layer)
The configuration of the electron transport layer 110 is not particularly limited as long as it is a layer that can extract electrons generated by plasmon resonance in the metal body 150.

  However, the electron transport layer 110 is preferably composed of an n-type semiconductor containing a dopant. When the electron transport layer 110 is made of an n-type semiconductor containing a dopant, the electron transport in the electron transport layer 110 can be made efficient, and the photoelectric conversion efficiency is improved.

  Examples of such an n-type semiconductor include, but are not limited to, titanium oxide, strontium titanate, zinc oxide, and gallium nitride. Since these materials have a wide band gap, they are transparent to visible light. In addition, these materials have a feature that a relatively large photovoltaic force can be obtained upon light irradiation because the lower end of the conduction band is larger on the negative side.

  The dopant contained in the electron transport layer 110 is not limited to this, but may be at least one of niobium, nitrogen, phosphorus, and arsenic, for example. This is because any of these materials has a property of functioning as a good electron donor in an n-type semiconductor.

  The amount of the dopant contained in the electron transport layer 110 is not particularly limited, but is, for example, in the range of 0.001 wt% to 0.1 wt% with respect to the total weight of the electron transport layer 110.

  The thickness of the electron transport layer 110 may be in the range of 5 nm to 1000 nm, for example. However, as will be described later, when the electron transport layer 110 is also used as a substrate for supporting an element, the electron transport layer 110 may have a thickness that can ensure strength, for example, a range of 0.1 mm to 5 mm. .

(Other)
In addition, the photoelectric conversion element 100 may include a substrate that supports each component member. Such a substrate may be made of, for example, glass or plastic.

  Alternatively, the above-described constituent member, for example, the electron transport layer 110 may be formed thick and used as a substrate.

(Photoelectric conversion device according to one embodiment of the present invention)
Next, a configuration example of a photoelectric conversion device including the photoelectric conversion element having the above-described characteristics will be described with reference to FIG.

  FIG. 2 schematically shows a cross section of such a photoelectric conversion device.

  As illustrated in FIG. 2, the photoelectric conversion device 200 includes a photoelectric conversion element 101, a first electrode 260, and a second electrode 270.

  Among these, the photoelectric conversion element 101 has the same configuration as the photoelectric conversion element 100 described with reference to FIG. That is, the photoelectric conversion element 101 includes an electron transport layer 210, a hole transport layer 230, and a metal body 250 disposed in an island shape between the two.

  The first electrode 260 is disposed in contact with the hole transport layer 230 of the photoelectric conversion element 101.

  In the example of FIG. 1, the first electrode 260 is composed of particles of a conductive material dispersedly disposed immediately above the hole transport layer 230. The particles may be made of, for example, gold, platinum, silver, or copper.

  When the first electrode 260 is composed of particles dispersed on the surface of the hole transport layer 230, light incident on the photoelectric conversion device 200 is not shielded so much by the first electrode 260. The transport layer 230 can be reached. For this reason, the photoelectric conversion apparatus 200 can use incident light more effectively, and photoelectric conversion efficiency improves.

  The second electrode 270 is disposed so as to be electrically connected to the electron transport layer 210 of the photoelectric conversion element 101. When it is difficult to directly connect the electron transport layer 210 of the photoelectric conversion element 101 and the second electrode 270, a conductive adhesive layer 280 may be interposed between the two as shown in FIG. . However, installation of the conductive adhesive layer 280 is optional.

  The second electrode 270 is made of a conductive material such as gold, platinum, silver, or copper. Further, the conductive adhesive layer 280 may be made of, for example, an indium gallium alloy.

  When the photoelectric conversion device 200 is operated, light is incident from the first electrode 260 side. When this incident light is applied to the metal body 230 of the photoelectric conversion element 101, plasmon resonance is induced in the metal body 250, and charge separation occurs. The holes generated by the charge separation move to the hole transport layer 230 side of the photoelectric conversion element 101 and further to the first electrode 260. On the other hand, electrons generated by the charge separation move to the electron transport layer 210 side of the photoelectric conversion element 101 and further to the second electrode 270. Thereby, an electromotive force is generated between the first electrode 260 and the second electrode 270.

  Therefore, when the first electrode 260 and the second electrode 270 of the photoelectric conversion device 200 are connected to an external load, a photocurrent flows and work can be performed on the external load.

  Here, as described above, the hole transport layer 230 of the photoelectric conversion element 101 includes an additive that acts as a hole acceptor. For this reason, the holes generated by the charge separation in the metal body 250 move to the hole transport layer 230 more effectively, and further move to the first electrode 260 side.

  Similarly, the electron transport layer 210 of the photoelectric conversion element 101 contains a dopant. For this reason, the electrons generated by the charge separation in the metal body 250 move to the electron transport layer 210 more effectively and further to the second electrode 270 side.

  As a result, the photoelectric conversion device 200 can significantly increase the photoelectric conversion efficiency as compared with the conventional photoelectric conversion device.

(Method for Producing Photoelectric Conversion Element According to One Embodiment of the Present Invention)
Next, an example of the manufacturing method of the photoelectric conversion element by one Embodiment of this invention is demonstrated.

  In the following description, the reference numerals used in FIG. 1 will be used for explaining each member for the sake of clarity.

  In FIG. 3, the flow of the manufacturing method of the photoelectric conversion element by one Embodiment of this invention is shown roughly.

As shown in FIG. 3, the manufacturing method of this photoelectric conversion element is as follows:
Preparing an electron transport layer containing a dopant (S110);
A step (S120) of disposing a metal body in an island shape on the electron transport layer;
Forming a hole transport layer on the electron transport layer so as to cover the metal body, the hole transport layer including an additive that acts as a hole acceptor (S130);
Have

  Hereinafter, each step will be described in detail.

(Step S110)
First, the electron transport layer 110 containing a dopant is prepared. The dopant may be at least one of niobium, nitrogen, phosphorus, and arsenic. The concentration of the dopant may be in the range of 0.001 wt% to 0.1 wt%.

The method for preparing such an electron transport layer 110 is not particularly limited. For example, the electron transport layer 110 may be configured by injecting a dopant into a semiconductor substrate such as TiO ₂ .

  Alternatively, a commercially available n-type semiconductor substrate containing a predetermined amount of dopant in advance may be used as the electron transport layer 110.

(Step S120)
Next, the metal body 150 is arranged in an island shape on the electron transport layer 110.

  Note that the following first and second processes can be considered as simple processes for arranging the metal bodies 150 in an island shape.

(First process)
In the first process, first, a continuous metal film is formed on the electron transport layer 110. Although the film forming method is not particularly limited, for example, a vacuum deposition method, a sputtering method, or the like can be used.

  For example, gold, silver, copper, platinum, aluminum, and alloys thereof may be selected as the metal to be formed.

  The thickness of the continuous metal film is, for example, in the range of 1 nm to 10 nm.

  Next, the electron transport layer 110 provided with the metal continuous film is heat-treated. By the heat treatment, each metal atom in the continuous film diffuses on the surface of the electron transport layer 110. As a result, the metal continuous film is separated into a plurality of islands, and islands (for example, approximately hemispherical) of the metal body 150 are formed.

  The heat treatment is performed, for example, in an inert gas atmosphere, an oxygen atmosphere, an air atmosphere, or a vacuum (including a reduced pressure environment). The heat treatment temperature is, for example, in the range of 600 ° C. to 850 ° C., and the heat treatment time is, for example, 30 minutes to 1 hour.

  Here, when the metal continuous film is made of gold, since gold atoms easily diffuse on the surface of the electron transport layer 110, a large number of islands can be formed relatively easily.

  In the case where the island of the metal body 150 is formed of a plurality of materials, the process of forming the island by the above-described continuous metal film formation to heat treatment may be repeated by changing the material.

(Second process)
In the second process, first, a first mask having a predetermined pattern is disposed on the electron transport layer 110. In the first mask, a plurality of openings corresponding to positions where the metal bodies 150 are arranged are formed.

  Next, a first metal film is formed through the first mask. For film formation, for example, a sputtering method may be used. The layer thickness of the first metal is, for example, in the range of 1 nm to 10 nm.

  Thus, the first metal island is arranged on the electron transport layer 110 in a predetermined pattern.

  Next, if necessary, a second mask having a predetermined pattern is disposed on the electron transport layer 110. Then, the second metal film is formed by the method as described above through the second mask.

  As a result, the metal body 150 having a plurality of first metal islands and a plurality of second metal islands can be disposed on the electron transport layer 110.

  If necessary, third and fourth metal islands may be formed through the third and fourth masks, respectively.

  Through the above steps, the metal body 150 can be arranged in an island shape on the electron transport layer 110.

(Step S130)
Next, a hole transport layer 130 is formed on the electron transport layer 110 and the metal body 150 so as to cover the metal body 150. As described above, the hole transport layer 130 is made of, for example, a p-type semiconductor. The hole transport layer 130 includes an additive that becomes a hole acceptor.

  The hole transport layer 130 may be formed by an atomic layer deposition (ALD) method, a pulse laser deposition (PLD) method, a molecular beam epitaxial film formation (MBE) method, a sputtering method, or the like. In particular, the ALD method and the PLD method are preferable. This is because these methods can uniformly disperse the additive in the hole transport layer 130 at the atomic level.

  Alternatively, the hole transport layer 130 may be formed by first forming a film that does not contain an additive, and then injecting the additive into this film.

  After the formation of the hole transport layer 130, the obtained stacked body (photoelectric conversion element) may be heat-treated. By performing the heat treatment, the hole transport layer 130 with few defects can be obtained.

  Note that in the case where a metal oxide such as nickel oxide (NiO) is formed by the ALD method and the PLD method, the film formation atmosphere is an atmosphere containing oxygen (for example, a mixed atmosphere of oxygen and an inert gas). preferable. Thereby, decomposition | disassembly of the formed metal oxide can be suppressed.

  The thickness of the hole transport layer 130 is, for example, in the range of 5 nm to 200 nm. Note that in the ALD method, the PLD method, and the like, it may be difficult to form a thick film in a realistic film formation time by a single film formation process. In such a case, the film can be thickened by repeating the film formation process to the heat treatment described above.

  Next, examples of the present invention will be described.

Example 1
The photoelectric conversion device as shown in FIG. 2 was manufactured by the following method, and its characteristics were evaluated.

(Manufacture of photoelectric conversion devices)
A titanium oxide substrate (single crystal) doped with 0.05 wt% niobium was prepared as a substrate that also functions as an electron transport layer.

  Next, a gold continuous film having a thickness of 3 nm was formed on one surface (first surface) of the titanium oxide substrate by vacuum deposition. Thereafter, the titanium oxide substrate was heat-treated at 800 ° C. for 1 hour in a nitrogen atmosphere.

  Thereby, gold was arranged in an island shape on the first surface of the titanium oxide substrate.

  In FIG. 4, an example (SEM photograph) of the form of the 1st surface of a titanium oxide board | substrate is shown. As shown in FIG. 4, it can be seen that fine islands of gold are distributed almost uniformly on the first surface of the titanium oxide substrate. The gold island is substantially circular in top view, and the maximum dimension of the island is in the range of 1 nm to 30 nm. Although not shown in the figure, the three-dimensional shape of each island was a substantially hemispherical shape.

  Next, nickel oxide containing lithium was formed as a hole transport layer on the first surface of the titanium oxide substrate so as to cover these gold islands. The amount of lithium was 0.005 wt% with respect to nickel oxide.

For the film formation of nickel oxide, a pulse laser deposition apparatus (manufactured by Pascal) was used, and the target thickness was 100 nm. The titanium oxide substrate during the nickel oxide film formation was heated to 200 ° C. The atmosphere during film formation was a mixed atmosphere of oxygen and argon, and the oxygen partial pressure was 1 × 10 ⁻² Pa. The laser energy was 40 mJ and the pulse frequency was 10 Hz.

  Through the above steps, a photoelectric conversion element was obtained.

  Next, a dispersion film of gold nanoparticles (thickness 4 nm) was formed on the surface of nickel oxide of the obtained photoelectric conversion element by a sputtering method.

  Next, a copper foil having a thickness of 20 nm was attached to the exposed surface (second surface) of the titanium oxide substrate, that is, the bottom surface of the photoelectric conversion element via an indium-gallium adhesive paste. Thereafter, the adhesive paste was dried and solidified.

  Through the above steps, a photoelectric conversion device having a first electrode (gold nanoparticles) and a second electrode (copper foil) on both surfaces of the photoelectric conversion element was obtained.

(Example 2)
A photoelectric conversion device was manufactured by the same method as in Example 1 described above. However, in Example 2, the amount of lithium as an acceptor contained in nickel oxide was 0.009 wt% with respect to the entire hole transport layer.

(Comparative Example 1)
A photoelectric conversion device was manufactured by the same method as in Example 1 described above. However, in Comparative Example 1, lithium was not added to nickel oxide. That is, a hole transport layer made only of nickel oxide was formed.

(Evaluation)
Using the photoelectric conversion devices according to Example 1, Example 2, and Comparative Example 1, photoelectric conversion characteristics were evaluated.

  Evaluation of photoelectric conversion characteristics of each photoelectric conversion device was performed as follows.

  Using the first electrode (gold nanoparticles) of the photoelectric conversion device as an anode and the second electrode (copper foil) as a cathode, the photoelectric conversion device is an electrochemical measurement device (ALS / CH Instruments 870DH: manufactured by ALS). Connected.

In this state, the photoelectric conversion device was irradiated with irradiation light vertically from the first electrode side. A solar simulator (WXS-156SL2: manufactured by WACOM) was used for irradiation. In this sunlight simulator, simulated sunlight with an irradiation intensity of 100 mA / cm ² can be irradiated as irradiation light.

  The current-voltage characteristics obtained were measured with an electrochemical measurement device before and during irradiation of the photoelectric conversion device with irradiation light.

  In FIG. 5, an example of the current-voltage curve obtained with the photoelectric conversion apparatus which concerns on Example 1 is shown. FIG. 6 shows an example of a current-voltage curve obtained by the photoelectric conversion device according to Example 2. Furthermore, in FIG. 7, an example of the current-voltage curve obtained with the photoelectric conversion apparatus which concerns on the comparative example 1 is shown. 5-7, the broken line has shown the current-voltage curve in the state which is not irradiating light, and a continuous line is the current-voltage curve in the state which irradiated pseudo sunlight by the above-mentioned method. Is shown.

From the measured current-voltage curve, the open circuit voltage V _OC (V) and the short circuit current density J _SC (mA / cm ² ) in each photoelectric conversion device were calculated. The open circuit voltage V _OC (V) is obtained from the voltage at which the current becomes 0 (zero) in the current-voltage curve. The short-circuit current density _JSC is obtained from the current density at which the voltage is 0 (zero) in the current-voltage curve.

  Furthermore, the fill factor ff and the sunlight conversion efficiency η (%) of each photoelectric conversion device were calculated. The curve factor ff is expressed by the following formula:

The solar conversion efficiency η (%) is expressed by the following formula:

Here, V _max (V) and J _max (mA / cm ² ) are the maximum voltage and the maximum current density, respectively, at the maximum output power, that is, at the maximum power P _max (W).

  Table 1 below collectively shows each parameter value obtained in each photoelectric conversion device.

As shown in Table 1, when the hole transport layer contains an additive (lithium) (Examples 1 and 2), the solar conversion is higher than when the hole transport layer does not contain an acceptor (Comparative Example 1). It can be seen that the efficiency η can be obtained.

  In addition, it turns out from the comparison of Example 1 and Example 2 that there exists a tendency for sunlight conversion efficiency (eta) to fall conversely when an additive (lithium) is put too much. This is considered to be because if the lithium as an acceptor is excessively added to the hole transport layer, the width of the depletion layer of the photoelectric conversion element becomes too narrow and the electromotive force decreases.

  Next, the internal conversion efficiency IPCE (%) was calculated from the following formula:

Here, _Jph is the short-circuit current density (mA / cm ² ) under monochromatic irradiation, and is obtained from a current density-time curve with the initial potential set to zero. Also, λ is the wavelength (nm), and φ is the intensity of irradiation light (mW / cm ² ).

  The internal conversion efficiency IPCE (%) calculated in each photoelectric conversion device is collectively shown in FIG. In FIG. 8, the horizontal axis is the wavelength λ (nm), and the vertical axis is the internal conversion efficiency IPCE (%).

  As shown in FIG. 8, in the photoelectric conversion devices according to Example 1 and Example 2, the internal conversion efficiency IPCE (%) in the visible light region is significantly increased as compared with the photoelectric conversion device according to Comparative Example 1. You can see that Thus, from the evaluation of the internal conversion efficiency IPCE (%), it was confirmed that the photoelectric conversion efficiency is increased by adding the additive to the hole transport layer.

  The present invention can be used for optical energy conversion devices such as photocatalysts and solar cells.

100, 101 Photoelectric conversion element 110 Electron transport layer 112 First surface 114 Second surface 130 Hole transport layer 150 Metal body 200 Photoelectric conversion device 210 Electron transport layer 230 Hole transport layer 250 Metal body 260 First electrode 270 Second Electrode 280 conductive adhesive layer

Claims (17)

An electron transport layer containing a dopant;
A hole transport layer including an additive disposed so as to contact the electron transport layer and acting as a hole acceptor;
A metal body arranged in an island shape along the interface between the electron transport layer and the hole transport layer, and
A photoelectric conversion element comprising:   The photoelectric conversion element according to claim 1, wherein the electron transport layer includes an n-type semiconductor.   The photoelectric conversion element according to claim 1, wherein the hole transport layer includes a p-type semiconductor.   4. The photoelectric conversion element according to claim 1, wherein the concentration of the additive contained in the hole transport layer is 0.001% by weight or more of the total weight of the hole transport layer.   5. The photoelectric conversion element according to claim 1, wherein the additive contained in the hole transport layer includes at least one selected from lithium, boron, and aluminum.   6. The metal body according to claim 1, wherein the metal body has first and second islands, and the first islands are made of a different kind of material from the second islands. Photoelectric conversion element.   The photoelectric conversion according to claim 1, wherein the metal body is made of at least one material selected from the group consisting of gold, silver, copper, platinum, aluminum, and alloys thereof. element. The photoelectric conversion element according to any one of claims 1 to 7,
A first conductive member electrically connected to the electron transport layer;
A second conductive member electrically connected to the hole transport layer;
A photoelectric conversion device. A method for producing a photoelectric conversion element, comprising:
(1) providing an electron transport layer containing a dopant;
(2) A step of separating and arranging a metal body in an island shape on the electron transport layer;
(3) forming a hole transport layer on the electron transport layer so as to cover the metal body;
Have
The said hole transport layer is a manufacturing method of a photoelectric conversion element containing the additive which acts as a hole acceptor.   The manufacturing method according to claim 9, wherein the concentration of the additive contained in the hole transport layer is greater than 0.001% by weight of the total weight of the hole transport layer.   The manufacturing method according to claim 9 or 10, wherein the additive contained in the hole transport layer includes at least one selected from lithium, boron, and aluminum. The step (3)
(4) The method includes: depositing the hole transport layer on the electron transport layer by an atomic layer deposition (ALD) method or a pulse laser deposition (PLD) method. The manufacturing method as described in.   The manufacturing method according to claim 9, wherein the metal body is made of a material selected from the group consisting of gold, silver, copper, platinum, aluminum, and alloys thereof. The step (2) includes
(5-1) installing a continuous film composed of a first material on the electron transport layer; and (5-2) heat treating the continuous film to form the first material into an island shape. The manufacturing method according to claim 9, further comprising a step of changing. The step (2) includes
(6-1) Forming a first material in an island shape on the electron transport layer through a first mask;
(6-2) Forming a second material different from the first material in an island shape on the electron transport layer through a second mask;
Have
The manufacturing method according to claim 9, wherein an island of the first and second materials is formed as the metal body after the step (2).   The manufacturing method according to claim 9, wherein the additive is introduced into the hole transport layer simultaneously with the formation of the hole transport layer in the step (3).   The manufacturing method according to claim 9, wherein the additive is introduced into the hole transport layer after the formation of the hole transport layer in the step (3).