JP2012129420A - Photoelectric conversion element and solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion element in which a short circuit current (Jsc) is increased, a high photoelectric conversion efficiency (PCE) is achieved, and generation of a leakage current is suppressed.SOLUTION: A photoelectric conversion element 100 includes at least a pair of electrodes 120, 160 and an active layer 140. In the photoelectric conversion element, there exist a diffraction peak corresponding to a lattice plane [10-1] and a diffraction peak corresponding to a lattice plane [101] in a thin film X ray diffraction spectrum of the active layer by an out-of-plane measurement. A relative intensity of the diffraction peak corresponding to the lattice plane [101] relative to the diffraction peak corresponding to the lattice plane [10-1] is 40% or more.

Description

  The present invention relates to a photoelectric conversion element and a solar cell.

As organic thin film solar cells, those using a polymer coated semiconductor layer or a low molecular vapor deposition semiconductor layer are known, and in recent years, organic thin film solar cells using a coating conversion semiconductor layer such as tetrabenzoporphyrin have been known. It has been proposed (Patent Document 1). As the polymer-coated semiconductor layer, polyhexylthiophene (P3HT), which is a conjugated polymer soluble as a p-type semiconductor, is often used, and a derivative with increased solubility of fullerene, such as PCBM, as an n-type semiconductor, Most of them are composed only of a bulk heterolayer in which p-type and n-type molecules coexist. The low molecular deposition based semiconductor layer, phthalocyanines as a p-type semiconductor, pentacene, or oligothiophene is often C ₆₀ is used as the n-type semiconductor, and a p-type semiconductor and the n-type semiconductor p-n junction interface Some have a p-i-n stacked structure in which i layers coexisting with each other are introduced. The coating conversion type thin film solar cell has a laminated structure similar to that of a low molecular vapor deposition type, and tetrabenzoporphyrin or the like is used as a p-type semiconductor, and a fullerene derivative or the like is used as an n-type semiconductor (Patent Document 1). .

  Non-Patent Document 1 introduces an i-layer having a characteristic column / canyon structure at the pn interface in an organic thin film solar cell using tetrabenzoporphyrin as a p-type semiconductor and a fullerene derivative as an n-type semiconductor. It is described that a photoelectric conversion efficiency exceeding 5% can be obtained by producing a p-i-n structure. However, these photoelectric conversion elements still have a low conversion efficiency (PCE: Power Conversion Efficiency), and the study of improving the conversion efficiency is eagerly underway for practical use. In order to improve the conversion efficiency, it is necessary to increase an open circuit voltage (Voc: Open-Circuit Voltage) and a short circuit current (Jsc: Short-Circuit Current).

International Publication No. 2007/126102

Y. Matsuo et al. J. et al. Am. Chem. Soc. 2009, 131, 16048-16050.

According to the study of the present inventor, in the photoelectric conversion element using, for example, tetrabenzoporphyrin as the p-type semiconductor material compound, the short-circuit current (Jsc) of the photoelectric conversion element is insufficient and less than 10 mA / cm ² , Has been found to hinder the improvement of photoelectric conversion efficiency (PCE). Further, when the p-type semiconductor layer is formed on the electrode or the hole extraction layer, the crystal shape of the p-type semiconductor material compound becomes non-uniform, and the film on the surface of the electrode or the hole extraction layer is not sufficiently coated. For this reason, it has been found that there are some photoelectric conversion elements in which leakage current is generated.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor has controlled the crystal orientation and crystal shape of the semiconductor material compound, thereby expanding the light absorption wavelength region and improving the light absorption efficiency. (Jsc) is increased, high photoelectric conversion efficiency (PCE) is obtained, and it has been found that a photoelectric conversion element in which generation of leakage current is suppressed with good reproducibility is obtained, and the present invention has been achieved.

That is, the gist of the present invention is as follows.
[1] A photoelectric conversion element having at least a pair of electrodes and an active layer,
In the thin-film X-ray diffraction spectrum of the active layer obtained by the out-of-plane measurement method, there are a diffraction peak corresponding to the lattice plane [10-1] and a diffraction peak corresponding to the lattice plane [101]. The relative intensity of the diffraction peak corresponding to the lattice plane [101] with respect to the diffraction peak corresponding to 10-1] is 40% or more.
[2] In the thin-film X-ray diffraction spectrum of the active layer by the out-of-plane measurement method, there is a diffraction peak corresponding to the lattice plane [002], and the diffraction peak corresponding to the lattice plane [10-1] The photoelectric conversion element according to [1], wherein the relative intensity of the diffraction peak corresponding to the lattice plane [002] is 30% or more.
[3] In the thin-film X-ray diffraction spectrum of the active layer by the out-of-plane measurement method, there is a diffraction peak corresponding to the lattice plane [200], and the diffraction peak corresponding to the lattice plane [10-1] The photoelectric conversion element according to [1] or [2], wherein the relative intensity of the diffraction peak corresponding to the lattice plane [200] is 50% or more.
[4] In the thin-film X-ray diffraction spectrum of the active layer by the out-of-plane measurement method, there is a diffraction peak corresponding to the lattice plane [202], and the diffraction peak corresponding to the lattice plane [10-1] The photoelectric conversion element according to any one of [1] to [3], wherein the relative intensity of the diffraction peak corresponding to the lattice plane [202] is 15% or more.
[5] In the thin-film X-ray diffraction spectrum of the active layer by the out-of-plane measurement method, there is a diffraction peak corresponding to the lattice plane [004], and the diffraction peak corresponding to the lattice plane [10-1] The photoelectric conversion element according to any one of [1] to [4], wherein the relative intensity of the diffraction peak corresponding to the lattice plane [004] is 20% or more.
[6] The photoelectric conversion element according to any one of [1] to [5], wherein the active layer contains a porphyrin compound.
[7] A photoelectric conversion element having at least a pair of electrodes and an active layer,
The active layer contains a porphyrin compound;
In the ultraviolet visible transmission spectrum of the active layer, the half width of a peak having an absorption maximum wavelength in the range of 670 to 700 nm is 40 nm or more.
[8] The active layer is
Applying a semiconductor material precursor;
Converting the semiconductor material precursor into a semiconductor material compound;
The photoelectric conversion element according to any one of [1] to [7], wherein the photoelectric conversion element is formed by a method including:
[9] A photoelectric conversion element having at least a pair of electrodes and an active layer,
The active layer is
Forming a first layer including a first semiconductor material; and a second layer adjacent to the first semiconductor layer and including the first semiconductor material and the second material;
Simultaneously crystallizing the first semiconductor material contained in the first layer and the first semiconductor material contained in the second layer;
It is formed by the method containing this, The photoelectric conversion element characterized by the above-mentioned.
[10] A photoelectric conversion element having at least a pair of electrodes and an active layer,
The active layer is
After the step of forming a first layer including a first semiconductor material and a second layer adjacent to the first semiconductor layer and including a second semiconductor material,
A step of crystallizing the first semiconductor material contained in the first layer, or the first semiconductor material contained in the first layer and the second semiconductor contained in the second layer. It is formed by performing the process of crystallizing material simultaneously, The photoelectric conversion element characterized by the above-mentioned.
[11] A solar cell comprising the photoelectric conversion element according to any one of [1] to [10].

  According to the present invention, by controlling the crystal orientation and crystal shape of the semiconductor material compound, the light absorption wavelength region is broadened and the light absorption efficiency is improved, so that the short-circuit current (Jsc) is increased and high photoelectric conversion is achieved. It is possible to provide a photoelectric conversion element that has high efficiency (PCE) and suppresses generation of leakage current.

The figure which shows the photoelectric conversion element which concerns on one Embodiment of this invention. The figure which shows the transmitted light spectrum of the active layer of the photoelectric conversion element which concerns on one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail. The description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and is not specified in these contents unless it exceeds the gist of the present invention.

[1 Photoelectric Conversion Element According to the Present Invention]
The photoelectric conversion element according to the present invention includes at least an active layer and a buffer layer between a pair of electrodes. Hereinafter, an embodiment of the photoelectric conversion element according to the present invention will be described. In FIG. 1, the photoelectric conversion element 100 which is one Example which concerns on this invention is shown. FIG. 1 shows a photoelectric conversion element used in a general organic thin film solar cell, but the photoelectric conversion element according to the present invention is not limited to the structure of FIG. The photoelectric conversion element 100 in FIG. 1 includes electrodes 120 and 160 and an active layer 140 disposed between the electrodes. Furthermore, the photoelectric conversion element according to the present embodiment may include a substrate 110 and buffer layers 130 and 150 as shown in FIG. In FIG. 1, the electrode 120 is an electrode (anode) suitable for collecting holes, and the electrode 160 is an electrode (cathode) suitable for collecting electrons. Of course, in another embodiment according to the present invention, the anode 120 and the cathode 160 may be reversed, and in this case, the buffer layer 130 and the buffer layer 150 may be reversed. Hereinafter, each of these parts will be described.

[2 Active layer 140]
In the photoelectric conversion element 100 according to this example, the active layer 140 includes a p-type semiconductor material and an n-type semiconductor material. The active layer 140 preferably includes a crystalline semiconductor material compound. This crystalline semiconductor material compound is at least one of a p-type semiconductor material compound and an n-type semiconductor material compound, and is preferably a p-type semiconductor material compound. In the photoelectric conversion element, light is absorbed by the active layer, electricity is generated at the interface between the p-type semiconductor and the n-type semiconductor, and the generated electricity is extracted from the electrode.

  The larger the contact area between each electrode and the p-type semiconductor material compound and n-type semiconductor material compound, the better. In particular, a large contact area between the p-type semiconductor and the electrode is preferable because the leakage current can be reduced. When the buffer layer is included between the p-type semiconductor and the electrode, it is preferable that the contact area between the p-type semiconductor and the buffer layer is large.

  The layer configuration of the active layer 140 is arbitrary, but for example, a thin film stacked type in which a p-type semiconductor layer and an n-type semiconductor layer are stacked is preferable. In particular, the mixed layer (i) includes a p-type semiconductor layer and an n-type semiconductor layer, and a p-type semiconductor material and an n-type semiconductor material are mixed between the p-type semiconductor layer and the n-type semiconductor layer. Layer). By having a mixed layer, the part which generate | occur | produces a photocurrent can be increased.

  Further, it is more preferable that the mixed layer has a nanostructure. For example, in the mixed layer, there are a portion composed of an n-type semiconductor material and a portion composed of a p-type semiconductor material, and the average size (for example, the major axis) of each portion is 1 nm to 1000 nm. Preferably there is. By having a nanostructure in the mixed layer, a route for transporting electrons and holes generated in the mixed layer is supplied, and the photocurrent is expected to increase. A method for forming such a nanostructure will be described later.

(Thin film X-ray diffraction)
In the diffraction pattern in the thin film X-ray diffraction spectrum by the out-of-plane measurement method, the active layer 140 according to this example has a diffraction peak (hereinafter referred to as peak A) corresponding to the lattice plane [10-1], and a lattice plane [ 101] and a diffraction peak (hereinafter referred to as peak B). Furthermore, the relative intensity of the interplanar peak B with respect to the peak A is 40% or more, preferably 70% or more, more preferably 100% or more, on the other hand, usually 500% or less, preferably 400% or less. More preferably, it is 300% or less. It is suggested that the relative intensity of peak B with respect to peak A is 40% or more, which suggests that the crystal orientation of the semiconductor material compound is distributed without being strongly biased in one direction.

  In addition, the active layer 140 according to this example has a diffraction peak (hereinafter referred to as peak C) corresponding to the lattice plane [002], a lattice plane [200] in a diffraction pattern in a thin film X-ray diffraction spectrum by an out-of-plane measurement method. ] At least one of a diffraction peak corresponding to the lattice plane [202], a diffraction peak corresponding to the lattice plane [202], and a diffraction peak corresponding to the lattice plane [004] (hereinafter referred to as peak F). It is preferable to have.

  S. Aramaki, J. et al. Mizuguchi Acta Cryst. 2003, E59, o1556-o1558. According to the crystal lattice constant described in the above, the diffraction peaks corresponding to the respective lattice planes of the crystal of tetrabenzoporphyrin (BP), which is a p-type semiconductor material used in Example 1 described later, are as follows. That is, a diffraction peak having a surface spacing d (λ / 2 sin θ) of 10.1 Å corresponds to the lattice plane [10-1]. Similarly, a diffraction peak having a surface separation d (λ / 2 sin θ) of 8.5８ corresponds to the lattice plane [101]. Further, the diffraction peak having a surface separation d (λ / 2 sin θ) of 7.3 mm corresponds to the lattice plane [002]. Further, the diffraction peak having an interplanar spacing d (λ / 2 sin θ) of 6.0 mm corresponds to the lattice plane [200]. Further, the diffraction peak having a surface spacing d (λ / 2 sin θ) of 4.3 Å corresponds to the lattice plane [202]. Furthermore, a diffraction peak having a surface separation d (λ / 2 sin θ) of 3.7Å corresponds to the lattice plane [200].

  The relative intensity of peak C to peak A is preferably 30% or more, more preferably 50% or more, and more preferably 80% or more. On the other hand, it is preferably 400% or less, more preferably 300% or less, and even more preferably 200% or less.

  The relative intensity of peak D with respect to peak A is preferably 50% or more, more preferably 70% or more, and even more preferably 90% or more. On the other hand, it is preferably 400% or less, more preferably 300% or less, and even more preferably 200% or less.

  The relative intensity of peak E to peak A is preferably 15% or more, more preferably 20% or more, and more preferably 25% or more. On the other hand, it is preferably 200% or less, more preferably 150% or less, and even more preferably 100% or less.

  The relative intensity of peak F to peak A is preferably 15% or more, more preferably 20% or more, and more preferably 25% or more. On the other hand, it is preferably 200% or less, more preferably 150% or less, and even more preferably 100% or less.

  The high intensity of these peaks (peaks A, B, C, D, E, and F) means that there are many crystals of the semiconductor material compound whose b-axis is parallel to the sample (substrate) surface. means. On the other hand, these peaks (peaks A, B, C, D, E, and F) are present and have the above-described relative intensities with respect to peak A, indicating that the crystal orientation of the semiconductor material compound is in one direction. It is shown that it is uniformly distributed without being strongly biased. Such an active layer is expected to collect light of a wider range of wavelengths and improve photoelectric conversion efficiency. In addition, the high intensity of these peaks (peaks A, B, C, D, E, and F) suggests that the crystal shape of the semiconductor material compound is uniform. In this case, since the electrodes 120 and 160 or the buffer layers 130 and 150 are uniformly and sufficiently coated with the active layer 140, generation of leakage current is expected to be suppressed, which is preferable.

  The active layer 140 according to the present embodiment preferably has at least a peak A and a peak D in a diffraction pattern in a thin film X-ray diffraction spectrum by an in-plane measurement method. In this case, the relative intensity of the peak D with respect to the peak A is preferably 140% or more, more preferably 150% or more, and more preferably 160% or more. On the other hand, it is preferably 500% or less, more preferably 400% or less, and even more preferably 300% or less. It is suggested that the relative intensity of the peak D with respect to the peak A is 140% or more, suggesting that the crystal orientation of the semiconductor material compound is distributed without being strongly biased in one direction.

  Further, the active layer 140 according to the present embodiment may have at least one of the peak B and the peak C in the in-plane diffraction pattern in the thin film X-ray diffraction spectrum. The relative intensity of peak B with respect to peak A is preferably 30% or more, more preferably 40 or more, and more preferably 50% or more. On the other hand, it is preferably 150% or less, more preferably 140% or less, more preferably 130% or less.

  The relative intensity of peak D with respect to peak A is preferably 130% or more, more preferably 140% or more, and more preferably 150% or more. On the other hand, it is preferably 500% or less, more preferably 400% or less, and even more preferably 300% or less.

  The high intensity of these peaks (peaks A, B, C, and D) means that there are many crystals of the semiconductor material compound whose b-axis is parallel to the sample (substrate) surface. On the other hand, when these peaks (peaks A, B, C, and D) exist and each has the above-described relative intensity with respect to peak A, the crystal orientation of the semiconductor material compound is strongly biased in one direction. It is shown that it is distributed without any problem. Such an active layer is expected to collect light of a wider range of wavelengths and improve photoelectric conversion efficiency.

  if there is a difference in peak pattern between the out-of-plane X-ray diffraction method and the in-plane X-ray diffraction method, a crystal that is oriented at a low angle (ie, in a direction close to horizontal) with respect to the sample surface; It can mean that there is a difference in the degree of growth between crystals oriented at a high angle (ie, in a direction close to vertical). For example, when the peak intensity is strong in the X-ray diffraction spectrum by the out-of-plane measurement method and the peak is weak in the X-ray diffraction spectrum by the in-plane measurement method, the crystal growth of the low angle orientation is higher than that of the high angle orientation. Suggested to be weak.

  In the present example, it is preferable that the relative intensity of peak B to peak A in the out-of-plane X-ray diffraction method is stronger than the relative intensity of peak B to peak A in the in-plane X-ray diffraction method. In this case, it is considered that crystal growth in the b-axis (π-π stacking) direction, which is the crystal growth direction, is poor. This suggests that the crystal growth direction is not single. It is considered that crystals having various orientations exist in the active layer where such a difference in relative strength exists. Therefore, such an active layer is expected to collect light of a wider range of wavelengths and improve the photoelectric conversion efficiency.

The in-plane measurement method and the out-of-plane measurement method for the thin film X-ray diffraction spectrum are not particularly limited, and can be measured according to a known method. In this specification, as an example, an X-ray diffraction apparatus (also referred to as Rigaku ATX-G: XRD apparatus) manufactured by Rigaku is used, and measurement is performed under the following measurement conditions.
X-ray source: synchrotron radiation (SPring-8 BL46XU)
X-ray wavelength: 1.0 mm, 1.1809 mm
Scan axis: out-of-plane 2θ
in-plane 2θχ
Measurement mode: Continuous
Reading width: 0.05 °
Scanning speed: 5 deg / min (out-of-plane)
10 deg / min (in-plane)
Measurement temperature: room temperature

  By dividing the X-ray wavelength λ by 2 sin θ for the obtained peak, the surface separation d [Å] (= λ / 2 sin θ) is obtained. Which plane corresponds to the lattice plane corresponding to the interplanar spacing d can be determined using the crystal lattice constant of the semiconductor material compound.

(Light absorption)
The light absorption of the active layer can be measured by an absorption spectrum or a transmission light spectrum. For example, the absorption spectrum or transmitted light spectrum of the thin film in the ultraviolet-visible region (UV-Vis) may be measured. Further, the absorption spectrum or transmitted light spectrum of the thin film in the infrared region may be measured.

  The absorption spectrum of the active layer preferably satisfies the following conditions. In particular, when the semiconductor material compound contained in the active layer is a porphyrin compound, it is preferable to satisfy the following conditions. That is, in the absorption spectrum of the active layer, the full width at half maximum of a peak having an absorption maximum wavelength (λmax) in the range of 670 to 700 nm (hereinafter referred to as Q-band peak) is preferably 40 nm or more, more preferably Is 50 nm or more. Further, the half width of the peak of the Q band is preferably 200 nm or less, and more preferably 150 nm or less. It is preferable that the half width of the peak of the Q band is in such a range because light of a wider wavelength can be efficiently absorbed and the photoelectric conversion element can perform photoelectric conversion more efficiently. The transmitted light spectrum of the active layer also preferably satisfies the same conditions as the absorption spectrum.

  In this specification, the half width of the absorption spectrum (or transmitted light spectrum) is determined as follows. That is, a baseline that passes through the smallest (larger) point of the absorption spectrum (or transmitted light spectrum) in a predetermined wavelength region is drawn. The height from this baseline to the peak apex is defined as peak intensity, and the width between wavelengths giving half the peak intensity is defined as the half width. The predetermined wavelength region may be between 400 nm and 800 nm, for example.

[2.1 Formation Method of Active Layer 140]
In the photoelectric conversion element according to this example, the active layer 140 is preferably a thin film stacked type in which a p-type semiconductor layer and an n-type semiconductor layer are stacked. In particular, the active layer 140 includes a p-type semiconductor layer containing a p-type semiconductor material, a mixed layer (a layer containing a p-type semiconductor material and an n-type semiconductor material), and an n-type semiconductor layer containing an n-type semiconductor material. It is preferable to have a structure (hereinafter referred to as a pin structure). Examples of the p-type semiconductor material and the n-type semiconductor material will be described later.

  When forming the active layer 140, it is preferable to crystallize the semiconductor material compound contained in one layer and the semiconductor material compound contained in another layer at the same time. For example, when forming the active layer 140 having a pin structure, it is preferable to simultaneously crystallize the semiconductor material compound contained in the semiconductor layer and the semiconductor material compound contained in the mixed layer. When forming the active layer 140 having a structure in which a p-type semiconductor layer and an n-type semiconductor layer are joined (hereinafter referred to as a pn structure), a p-type semiconductor material compound contained in the p-type semiconductor layer The n-type semiconductor material compound contained in the n-type semiconductor layer may be crystallized at the same time. In forming the active layer 140 having a structure in which the p-type semiconductor layer and the n-type semiconductor layer are joined (hereinafter referred to as a pn structure), the p-type semiconductor material compound contained in the p-type semiconductor layer is added. The n-type semiconductor layer may be formed and then crystallized.

  Hereinafter, as an example, a case where the p-type semiconductor material compound contained in the p-type semiconductor layer and the p-type semiconductor material compound contained in the mixed layer are crystallized simultaneously will be described. However, the same applies to the case where the n-type semiconductor material compound contained in the n-type semiconductor layer and the n-type semiconductor material compound contained in the mixed layer are crystallized at the same time, and are included in the scope of the present invention. The same applies to the case where the p-type semiconductor material compound contained in the p-type semiconductor layer and the n-type semiconductor material compound contained in the n-type semiconductor layer are crystallized at the same time, and are included in the scope of the present invention.

  When the p-type semiconductor material compound contained in the p-type semiconductor layer is crystallized, then the mixed layer is stacked, and when the p-type semiconductor material compound contained in the mixed layer is crystallized, the influence of crystals in the p-type semiconductor layer As a result, the crystal orientation of the p-type semiconductor material compound formed in the mixed layer may be aligned (epitaxial growth). On the other hand, when the p-type semiconductor material compound contained in the p-type semiconductor layer and the p-type semiconductor material compound contained in the mixed layer are crystallized simultaneously, the p-type semiconductor material compound having various orientations in the mixed layer Is expected to occur. Therefore, the active layer formed in this manner is expected to collect light of a wider range of wavelengths and improve the photoelectric conversion efficiency. That is, in the absorption spectrum of the active layer, it is expected that the half width of the peak of the Q band becomes larger.

  Further, since the crystal orientation of the semiconductor material compound is not strongly biased in one direction, it is expected that the peak intensity satisfies the above-mentioned standard in the thin film X-ray diffraction spectrum. Furthermore, it is expected that the mixed layer formed in this manner contains a semiconductor material compound having various crystal orientations and a uniform crystal shape. In this case, it is expected that the electrodes 120 and 160 or the buffer layers 130 and 150 are sufficiently covered with the active layer 140 and the generation of leakage current is suppressed.

  Below, the case where a mixed layer is laminated | stacked after laminating | stacking a p-type semiconductor layer is demonstrated. However, the same applies to the case where the p-type semiconductor layer is stacked after stacking the mixed layers, and is included in the scope of the present invention. In this embodiment, after the p-type semiconductor layer is stacked, the p-type semiconductor material compound contained in the p-type semiconductor layer is prevented from crystallizing. For example, the crystallization of the compound can be prevented from proceeding by not heating after the p-type semiconductor layer is stacked or by heating for a short time. When heating is performed, the temperature is preferably in the range of 150 ° C to 250 ° C, and more preferably in the range of 170 ° C to 200 ° C. The heating time is preferably 5 minutes or less, more preferably 3 minutes or less, and particularly preferably 1 minute or less. By heating within this range, crystallization of the compound can be suppressed, and photoelectric conversion efficiency is expected to improve.

Whether or not the p-type semiconductor material compound is crystallized in the p-type semiconductor layer can be determined, for example, by thin film X-ray diffraction spectrum measurement or absorption spectrum measurement. For example, in a thin film X-ray diffraction spectrum (particularly a spectrum obtained by an out-of-plane X-ray diffraction method), it can be determined that crystallization has not progressed when the peak is not sharp. For example, in a spectrum in which the horizontal axis is sin θ / λ and the vertical axis is intensity, the peak is determined not to be sharp when the half width of the peak having the maximum intensity is larger than 1.0E + 8 [m ⁻¹ ]. May be. In particular, when the semiconductor material compound is a porphyrin-based compound containing benzoporphyrin (BP), which will be described later, the peak intensity of the above-mentioned Q band is 0. When it is less than 3, it may be determined that the p-type semiconductor material compound is not crystallized.

  And after laminating | stacking a mixed layer, it is preferable to advance crystallization of a p-type semiconductor material compound by performing sufficient heating. For example, crystallization of the p-type semiconductor material compound can be promoted by heating. When heating is performed, the temperature is preferably in the range of 150 ° C to 250 ° C, and more preferably in the range of 170 ° C to 200 ° C. The heating time is preferably 5 minutes or more, more preferably 10 minutes or more, and particularly preferably 15 minutes or more. The heating time is preferably 180 minutes or less, more preferably 120 minutes or less, and particularly preferably 90 minutes or less. By heating within this range, sufficient crystallization can be performed while preventing deterioration of the active layer, so that the conversion efficiency of the photoelectric conversion element is expected to be improved.

  Whether or not the p-type semiconductor material compound is sufficiently crystallized can be determined, for example, by thin film X-ray diffraction spectrum measurement or absorption spectrum measurement. That is, crystallization may be promoted, for example, by heating until the thin film X-ray diffraction spectrum or the absorption spectrum does not change. As described above, it may be determined whether the peak of the thin film X-ray diffraction spectrum is sharp, or whether the p-type semiconductor material compound is sufficiently crystallized according to the peak intensity of the Q band.

  In this embodiment, the active layer 140 is completed by further stacking an n-type semiconductor layer on the mixed layer. In this case, the p-type semiconductor material compound may be crystallized before the n-type semiconductor layer is stacked or after the n-type semiconductor layer is stacked. The active layer 140 thus obtained preferably has a thin film X-ray diffraction spectrum that satisfies the above-described conditions.

  Various methods can be used for forming the p-type semiconductor layer, the n-type semiconductor layer, and the mixed layer. For example, the film may be formed using a vapor deposition method, or may be formed using a coating method such as a die coating method, a spin coating method, a dip coating method, a roll coating method, a spray coating method, or an ink jet method. Good. In the case of using the coating method, for example, an organic solvent can be used as the solvent, and it is particularly preferable to use a non-halogen solvent from the viewpoint of environmental load. For example, toluene, xylene, cyclohexylbenzene, or the like can be used.

  Furthermore, a semiconductor material precursor can be used. The semiconductor material precursor will be described in detail later. For example, a semiconductor layer containing a semiconductor material compound can be formed by preparing a solution of a semiconductor material precursor, applying the prepared solution, and then converting the semiconductor material precursor into a semiconductor material compound. The semiconductor material compound obtained by the conversion may be a p-type semiconductor material compound or an n-type semiconductor material compound.

  The case where the p-type semiconductor material compound contained in the p-type semiconductor layer and the p-type semiconductor material compound contained in the mixed layer are simultaneously crystallized has been described above. Also in this case, the p-type semiconductor layer and the mixed layer can be formed using the semiconductor material precursor. However, when a p-type semiconductor layer containing a p-type semiconductor material compound is formed by heating the semiconductor material precursor, the p-type semiconductor material compound may be crystallized if heated for a predetermined time or longer. is there.

  That is, in this case, the temperature at which the semiconductor material precursor is converted into the semiconductor material compound is preferably 150 ° C. or higher and 250 ° C., more preferably 170 ° C. or higher and 200 ° C. or lower. The heating time is preferably 5 seconds or more and 5 minutes or less, more preferably 10 seconds or more and 2 minutes or less, and particularly preferably 20 seconds or more and 1 minute or less. By setting the temperature and heating time within this range, it is possible to sufficiently convert the semiconductor material precursor to the semiconductor material compound while suppressing crystallization of the p-type semiconductor material compound.

  As described above, the active layer preferably has a nanostructure. Such a nanostructure can be obtained, for example, by simultaneously depositing an n-type semiconductor material compound and a p-type semiconductor material compound. Further, for example, by applying a solution containing an n-type semiconductor material compound and a p-type semiconductor material compound, a mixed layer having such a nanostructure can be formed.

  As another method for forming the nanostructure, the dummy compound may be replaced with an n-type semiconductor material compound after forming a layer containing a p-type semiconductor material compound and a dummy compound. For example, the dummy compound can be replaced with the n-type semiconductor material compound by applying a solution containing the n-type semiconductor material compound on the layer containing the p-type semiconductor material compound and the dummy compound. Alternatively, the dummy compound may be removed by applying a solvent, and then the dummy compound may be replaced with the n-type semiconductor material compound by applying a solution containing the n-type semiconductor material compound.

  On the contrary, the dummy compound may be replaced with the p-type semiconductor material compound after the layer including the n-type semiconductor material compound and the dummy compound is formed. Thus, when controlling the nanostructure of a mixed layer using a dummy compound, it is not necessary to consider the nanostructure of a mixed layer when selecting a semiconductor material compound. For this reason, an increase in the photocurrent and an improvement in the open-circuit voltage can be achieved independently.

  As the dummy compound, for example, adamantane, p-terphenyl, calix [4] arenetetra-n-propyl ether, phthalocyanine derivative, fullerene derivative, or the like can be used.

  Specifically, the active layer 140 can be formed as follows. First, a p-type semiconductor layer is formed on the electrode 120 or the buffer layer 130. Here, the p-type semiconductor material precursor is applied and heated to convert the p-type semiconductor material precursor into a p-type semiconductor material compound. Since the p-type semiconductor material compound is usually less soluble than the p-type semiconductor material precursor, the compound can be prevented from dissolving out of the p-type semiconductor layer when the next solution is applied by conversion. At this time, as described above, the conversion is performed so that the crystallization of the p-type semiconductor material compound does not proceed. Although there is no restriction | limiting in the film thickness of a p-type semiconductor layer, From a viewpoint of obtaining a uniform film | membrane, it is preferable that it is 10 nm or more, and it is more preferable that it is 20 nm or more. Further, from the viewpoint of reducing the internal resistance, it is preferably 1000 nm or less, and more preferably 200 nm or less.

  Next, a layer (mixed layer) including the p-type semiconductor material compound and the dummy compound is formed. Specifically, a solution containing a p-type semiconductor material precursor and a dummy compound is prepared and applied onto the p-type semiconductor layer. Then, by heating as described above, the p-type semiconductor material precursor in the mixed layer is converted into a p-type semiconductor material compound, and the p-type semiconductor material compound in the p-type semiconductor layer and p in the mixed layer are converted. And simultaneously crystallizing the type semiconductor material compound. Although there is no restriction | limiting in the film thickness of a mixed layer, From a viewpoint of obtaining a uniform film | membrane, it is preferable that it is 10 nm or more, and it is further more preferable that it is 20 nm or more. Further, from the viewpoint of reducing the internal resistance, it is preferably 1000 nm or less, and more preferably 200 nm or less.

  Furthermore, by applying a solution containing an n-type semiconductor material compound on the mixed layer, the dummy compound in the mixed layer is replaced with the n-type semiconductor material compound, and an n-type semiconductor layer is formed on the mixed layer. As the solution containing the n-type semiconductor material compound, a solution capable of dissolving the dummy compound in the mixed layer and not dissolving the p-type semiconductor material compound in the mixed layer as much as possible is used. Specifically, the solubility of the dummy compound in the solution containing the n-type semiconductor material compound is preferably 0.1% by weight or more, and the solubility of the p-type semiconductor material compound is preferably less than 0.1% by weight. Although there is no restriction | limiting in the film thickness of an n-type semiconductor layer, From a viewpoint of obtaining a uniform film | membrane, it is preferable that it is 10 nm or more, and it is more preferable that it is 20 nm or more. Further, from the viewpoint of reducing the internal resistance, it is preferably 1000 nm or less, and more preferably 200 nm or less. In this way, the active layer 140 can be formed.

[2.1 p-type semiconductor materials]
The p-type semiconductor material according to this example is preferably a low molecular organic semiconductor material compound. The molecular weight of the low molecular weight organic compound is not particularly limited both at the upper limit and the lower limit, but is usually 5000 or less, preferably 2000 or less, and is usually 100 or more, preferably 200 or more.

  The low molecular organic semiconductor material compound preferably has crystallinity. The reason is that the p-type semiconductor material compound having crystallinity has a strong intermolecular interaction, and holes generated at the interface between the p-type semiconductor and the n-type semiconductor in the active layer can be efficiently transported to the positive electrode. This is because it is expected.

The crystallinity in the present invention refers to the property of taking a three-dimensional periodic array with uniform orientation due to intermolecular interaction or the like. Examples of the crystallinity measuring method include X-ray diffraction (XRD), field effect mobility measurement, and the like. In particular, in the field effect mobility measurement, a crystalline compound having a hole mobility of 1.0 × 10 ⁻⁵ cm ² / (Vs) or more is preferable, and 1.0 × 10 ⁻⁴ cm ² / (Vs) or more is preferable. Certain crystalline compounds are more preferred.

  The low molecular weight organic semiconductor material compound according to this example preferably has the above properties, but there is no particular limitation. Specific examples of the low molecular weight organic semiconductor material compound according to this example include condensed aromatic hydrocarbons such as naphthacene, pentacene, and pyrene; oligothiophenes containing four or more thiophene rings such as α-sexithiophene; A combination of at least one of at least one of thiophene ring, benzene ring, fluorene ring, naphthalene ring, anthracene ring, thiazole ring, thiadiazole ring, and benzothiazole ring; phthalocyanine compound and metal complex thereof, tetrabenzoporphyrin, etc. And a macrocyclic compound such as a metal complex thereof. A phthalocyanine compound and a metal complex thereof, or a porphyrin compound such as tetrabenzoporphyrin and a metal complex thereof are preferable.

  Examples of the porphyrin compound and its metal complex (Q is CH in the lower figure), the phthalocyanine compound and its metal complex (Q is N in the lower figure) used as the p-type semiconductor material include compounds having the following structures.

Here, M represents a metal or two hydrogen atoms. As the metal, in addition to a divalent metal such as Cu, Zn, Pb, Mg, Co, Ni, a trivalent or higher metal having an axial ligand. Examples thereof include TiO, VO, SnCl ₂ , AlCl, InCl, and Si.

Y ^{1 to} Y ⁴ may each independently be a hydrogen atom or an alkyl group having 1 to 24 carbon atoms. The alkyl group having 1 to 24 carbon atoms is a saturated or unsaturated chain hydrocarbon group having 1 to 24 carbon atoms, or a saturated or unsaturated cyclic hydrocarbon group having 1 to 24 carbon atoms. Among them, a saturated or unsaturated chain hydrocarbon group having 1 to 12 carbon atoms or a saturated or unsaturated cyclic hydrocarbon group having 1 to 12 carbon atoms is preferable.

  Among the phthalocyanine compounds and metal complexes thereof, 29H, 31H-phthalocyanine, copper phthalocyanine complex, zinc phthalocyanine complex, titanium phthalocyanine oxide complex, magnesium phthalocyanine complex, lead phthalocyanine complex, copper 4,4 ′, 4 ″, 4 '' '-Tetraaza-29H, 31H-phthalocyanine complex, more preferably 29H, 31H-phthalocyanine, copper phthalocyanine complex. In addition, the above kind of compound or a mixture of plural kinds of compounds may be used.

  Among the porphyrin compounds and metal complexes thereof, 5,10,15,20-tetraphenyl-21H, 23H-porphine, 5,10,15,20-tetraphenyl-21H, 23H-porphine cobalt (II), 5,10,15,20-tetraphenyl-21H, 23H-porphine copper (II), 5,10,15,20-tetraphenyl-21H, 23H-porphine zinc (II), 5,10,15,20- Tetraphenyl-21H, 23H-porphine nickel (II), 5,10,15,20-tetraphenyl-21H, 23H-porphine vanadium (IV) oxide, 5,10,15,20-tetra (4-pyridyl)- 21H, 23H-porphine, 29H, 31H-tetrabenzo [b, g, l, q] porphine, 2 H, 31H-tetrabenzo [b, g, l, q] porphine cobalt (II), 29H, 31H-tetrabenzo [b, g, l, q] porphine copper (II), 29H, 31H-tetrabenzo [b, g, l, q] porphine zinc (II), 29H, 31H-tetrabenzo [b, g, l, q] porphine nickel (II), 29H, 31H-tetrabenzo [b, g, l, q] porphine vanadium (IV) oxide And more preferably 5,10,15,20-tetraphenyl-21H, 23H-porphine, 29H, 31H-tetrabenzo [b, g, l, q] porphine. In addition, the above kind of compound or a mixture of plural kinds of compounds may be used.

  Note that the p-type semiconductor material according to the present embodiment may be composed of one kind of compound or a mixture of plural kinds of compounds.

(Thermal stability)
Although there is no limitation in particular as glass transition temperature of the p-type semiconductor material which concerns on a present Example, 250 degreeC or more is preferable, More preferably, it is 280 degreeC or more. The upper limit is not particularly limited and is usually 350 ° C. or lower, preferably 400 ° C. or lower, but the glass transition temperature may not be observed. When the glass transition temperature is low, the compound changes in an amorphous state and a crystalline state in a temperature range in the film forming process, thereby impairing functional stability as a p-type semiconductor, so that the photoelectric conversion element efficiency can be lowered.

  The glass transition temperature in the present specification is defined as a point at which the specific heat of an organic compound in an amorphous state is changed to a temperature at which local molecular motion is started by thermal energy. When the temperature further increases, the solid structure changes and crystallization occurs (the temperature at this time is defined as the crystallization temperature (Tc)). When the temperature rises further, it generally melts at the melting point (Tm) and changes to a liquid state. However, the molecules may be decomposed or sublimated at a high temperature, and their phase transition may not be observed. What is necessary is just to measure a glass transition temperature by a well-known method, for example, DSC method is mentioned.

  The DSC method is a thermophysical property measurement method (differential scanning calorimetry method) defined in JIS K-0129 “General Rules for Thermal Analysis”. The glass transition temperature of the amorphous solid state of the organic material is a temperature at which molecular motion starts from the glass state, and can be measured by DSC as the temperature at which the specific heat changes. In order to determine the glass transition temperature more clearly, it is desirable to measure after quenching a sample once heated to a temperature higher than the glass point transfer.

  The energy level of the highest occupied molecular orbital (HOMO) of a compound used as a p-type semiconductor material is not particularly limited, but is a value with respect to a vacuum level calculated by, for example, photoelectron yield spectroscopy (PYS) (ionization potential) Is usually -6.0 eV or more, preferably -5.5 eV or more. The energy level of the highest unoccupied molecular orbital (LUMO) of a compound used as a p-type semiconductor material is not particularly limited. For example, a value (electron affinity) with respect to a vacuum level calculated by a cyclic voltammogram is usually −4. 0.0 eV or more, preferably -3.5 eV or more.

  In order to efficiently transfer electrons from the electron donor layer (p-type semiconductor layer) to the electron acceptor layer (n-type semiconductor layer), a compound used as a p-type semiconductor material and an n-type semiconductor material are used. The relative relationship of the lowest unoccupied molecular orbital (LUMO) with the compound is important. Specifically, the LUMO of the p-type semiconductor material compound is higher than the LUMO of the n-type semiconductor material compound by a predetermined energy, in other words, the electron affinity of the electron acceptor is higher than the electron affinity of the electron donor. It is preferable that only the energy is large. If the LUMO of the electron acceptor is too high, the electron transfer is difficult to occur, so that the short circuit current (Jsc) tends to be low. Since the open-circuit voltage (Voc) is determined by the difference between the highest occupied orbital (HOMO) of the p-type semiconductor material compound and the lowest unoccupied molecular orbital (LUMO) of the n-type semiconductor material compound, the HOMO of the electron donor is too high. Voc tends to be low.

  As a method for calculating the HOMO energy level, there are a method obtained by theoretical calculation and a method of actual measurement. Examples of the method to be obtained by theoretical calculation include a semi-empirical molecular orbital method and a non-empirical molecular orbital method. In addition, examples of the actual measurement method include photoelectron spectroscopy (PES) and photoelectron yield spectroscopy (PYS). Among them, photoelectron yield spectroscopy is preferable, and photoelectron yield spectroscopy is employed in this specification.

  Also, the LUMO energy level calculation method includes a method of obtaining by theoretical calculation and a method of actually measuring. Examples of the method to be obtained by theoretical calculation include a semi-empirical molecular orbital method and a non-empirical molecular orbital method. Examples of the actual measurement method include ultraviolet-visible absorption spectrum measurement method, cyclic voltammogram measurement method, and inverse photoelectron spectroscopy (IPES). Among them, the cyclic voltammogram measurement method is preferable, and the cyclic voltammogram measurement method is adopted in this specification.

  The size of the unit structure of the p-type semiconductor is not particularly limited, but the average minor axis is usually 5 nm or more, preferably 10 nm or more. Moreover, it is 500 nm or less normally, Preferably it is 100 nm or less. If it is too small, there is a problem that charges generated by charge separation are likely to recombine. If it is too large, excitons generated inside the structure diffuse to the interface with the opposite polarity semiconductor. However, there is a problem that the generation efficiency of charges is lowered.

(Semiconductor material precursor)
The semiconductor material compound according to the present embodiment may be generated from a semiconductor material precursor. By applying an external stimulus such as heating or light irradiation to the semiconductor material precursor, the semiconductor material precursor is converted into a semiconductor material compound. Moreover, it is preferable that the semiconductor material precursor which concerns on a present Example is excellent in film forming property. In particular, in order to deposit a semiconductor material precursor using a coating method, the semiconductor material precursor itself can be applied in a liquid state, or the semiconductor material precursor is highly soluble in any solvent and can be applied as a solution. It is preferable that When the preferable range of the solubility is raised, the solubility of the semiconductor material precursor in the solvent is usually 0.1% by weight or more, preferably 0.5% by weight or more, more preferably 1% by weight or more. The higher the solubility, the easier it is to form a film containing the semiconductor material precursor.

  The type of the solvent is not particularly limited as long as it can uniformly dissolve or disperse the semiconductor material precursor. For example, aliphatic hydrocarbons such as hexane, heptane, octane, isooctane, nonane, decane; toluene, xylene Aromatic hydrocarbons such as chlorobenzene and orthodichlorobenzene; lower alcohols such as methanol, ethanol and propanol; ketones such as acetone, methyl ethyl ketone, cyclopentanone and cyclohexanone; esters such as ethyl acetate, butyl acetate and methyl lactate Halogen hydrocarbons such as chloroform, methylene chloride, dichloroethane, trichloroethane, trichloroethylene; ethers such as ethyl ether, tetrahydrofuran, dioxane; dimethylformamide, dimethylacetate Amides such as bromide, and the like. Among these, aromatic hydrocarbons such as toluene, xylene, chlorobenzene and orthodichlorobenzene, and halogen hydrocarbons such as chloroform, methylene chloride, dichloroethane, trichloroethane and trichloroethylene are preferable.

  It is preferable that the semiconductor material precursor according to this example can be easily converted into a semiconductor material compound. In the step of converting the semiconductor material precursor to the semiconductor material compound, what kind of external stimulus is given to the semiconductor precursor is arbitrary. For example, heat treatment and / or light treatment can be performed. Preferably, it is heat treatment. In this case, it is preferable that a part of the skeleton of the semiconductor material precursor contains a group that can be removed by a reverse Diels-Alder reaction. This detachable group is preferably solvophilic with respect to a predetermined solvent.

  Moreover, it is preferable that the semiconductor material precursor which concerns on this invention is converted into a semiconductor material compound with a high yield. Under the present circumstances, the yield of the semiconductor material compound obtained by converting from a semiconductor material precursor is arbitrary unless the performance of an organic photoelectric conversion element is impaired. If the suitable range of yield is raised, the yield of the semiconductor material compound obtained from the semiconductor material compound precursor is preferably as high as possible, usually 90 mol% or more, preferably 95 mol% or more, more preferably 99 mol% or more. is there. The higher the yield, the higher the conversion efficiency of the photoelectric conversion element is expected.

  The semiconductor material precursor according to the present embodiment preferably has the characteristics as described above, but is not particularly limited. Specific examples of the semiconductor material precursor include compounds described in JP-A-2007-324587. Among them, a preferable example is a compound represented by the following formula (A1).

In Formula (A1), at least one of X ¹ and X ² represents a group that forms a π-conjugated divalent aromatic ring, and Z ¹ -Z ² is a group that can be removed by heat or light. By desorption of Z ¹ -Z ² , a π-conjugated compound that is a semiconductor material compound is generated. The π-conjugated compound produced is preferably a pigment molecule. Further, X ¹ and X ² which are not a group that forms a π-conjugated divalent aromatic ring may be a substituted or unsubstituted ethenylene group.

In the compound represented by the formula (A1), Z ¹ -Z ² is eliminated by heat or light as shown in the following formula (A2) to form a π-conjugated compound having high planarity. This produced π-conjugated compound is a semiconductor material compound according to the present invention. In the present invention, the semiconductor material compound preferably exhibits semiconductor characteristics.

  Examples of the compound represented by the formula (A1) include the following. T-Bu represents a t-butyl group. M represents a divalent metal atom or an atomic group in which a trivalent or higher metal and another atom are bonded.

  For example, specific examples of converting the semiconductor material precursor into a semiconductor material compound include the following.

  The semiconductor material precursor represented by the formula (A1) may take a structure in which a positional isomer exists. That is, the semiconductor material precursor according to the present embodiment may be a mixture of positional isomers. A semiconductor material precursor which is a mixture of positional isomers is preferable because solubility in a solvent is improved as compared with a semiconductor material precursor composed of a single isomer component. In particular, the higher the solubility in a non-halogen solvent, the more advantageous in the production process. The reason why the solubility is improved is that although the crystallinity of the compound itself is potentially retained, regular three-dimensional intermolecular interactions are less likely to occur due to the presence of multiple isomers in the solution. Conceivable. In the present invention, the solubility of the regioisomer mixture in the non-halogen solvent is usually 0.1% by weight or more, preferably 1% by weight or more, more preferably 5% by weight or more. The higher the solubility, the easier it is to form a film containing the semiconductor material precursor.

  Non-halogen solvents include non-halogen aromatic hydrocarbons such as toluene and xylene; non-halogen ketones such as cyclopentanone and cyclohexanone; non-halogen aliphatic ethers such as tetrahydrofuran and 1,4-dioxane Is mentioned. In addition, a solvent may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

[2.2 n-type semiconductor materials]
The n-type semiconductor material according to the present embodiment is not particularly limited. For example, fullerene compounds, quinolinol derivative metal complexes typified by 8-hydroxyquinoline aluminum, condensed ring tetracarboxylic acid diimides such as naphthalene tetracarboxylic acid diimide, perylene tetracarboxylic acid diimide, terpyridine metal complex, tropolone metal complex, flavonol metal Complexes, perinone derivatives, benzimidazole derivatives, benzoxazole derivatives, benzthiazole derivatives, oxadiazole derivatives, thiadiazole derivatives, triazole derivatives, aldazine derivatives, bisstyryl derivatives, pyrazine derivatives, phenanthroline derivatives, quinoxaline derivatives, benzoquinoline derivatives, bipyridine derivatives, Condensed polycyclic aromatic total fluoride such as anthracene, pyrene, naphthacene, pentacene, single-walled carbon nanochu , Polyquinoline, polypyridine, polyaniline, poly (benzo-bis-imidazo benzo phenanthroline), boron polymer, cyano-substituted polyphenylene vinylene, and the like. Among them, a fullerene compound is preferable. The n-type semiconductor material may be composed of one kind of compound, or may be composed of two or more kinds of compounds.

The n-type semiconductor material according to this example can be, for example, a fullerene compound represented by the general formula (B1). In the formula (B1), m is usually an integer of 1 to 10, preferably an integer of 2 to 6. When a plurality of additional groups R ²¹ are present, each additional group R ²¹ may be the same or different. In addition, each additional group R ²¹ may form a ring directly or via an additional group. However, it is preferable that all the additional groups R ²¹ are not hydrogen. When there are a plurality of addition groups R ²¹ , isomers may exist depending on the position of addition. In this case, a single isomer may be used as the n-type semiconductor material, or a mixture of a plurality of isomers may be used as the n-type semiconductor material.

The fullerene (FLN) according to the present invention is a carbon cluster having a closed shell structure. The carbon number of fullerene is not particularly limited as long as it is usually an even number of 60 to 130. Examples of fullerenes include C ₆₀ , C ₇₀ , C ₇₆ , C ₇₈ , C ₈₂ , C ₈₄ , C ₉₀ , C ₉₄ , C ₉₆ and higher carbon clusters having more carbon than these. . Among these, _C60 or _C70 is preferable and _C60 is more preferable.

  As fullerenes, carbon-carbon bonds on some fullerene rings may be broken. Some carbon atoms may be replaced with other atoms. Furthermore, a metal atom, a non-metal atom, or an atomic group composed of these may be included in the fullerene cage.

The additional group R ²¹ may be anything, for example, a hydrogen atom, a halogen atom, an oxygen atom, a sulfur atom, a hydroxyl group, a cyano group, an amino group, an ester group, a carboxyl group, a carbonyl group, an oxycarbonyl group, a carbonyloxy group, a sulfonyl group, It may be a silyl group, a boryl group, a nitrile group, an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an aromatic group, or the like.

  As the alkyl group, those having 1 to 20 carbon atoms are preferred, and specific examples include methyl group, ethyl group, i-propyl group, n-propyl group, n-butyl group, i-butyl group, t-butyl group, Examples include n-hexyl group, cyclohexyl group, octyl group, 2-propylpentyl group, 2-ethylhexyl group, cyclohexylmethyl group, benzyl group and the like. A fluorinated alkyl group or a perfluoroalkyl group having 1 to 12 carbon atoms such as a trifluoromethyl group, a perfluorooctyl group, a perfluorohexyl group, or a perfluorobutyl group is also preferable. Furthermore, silylalkyl groups such as trimethylsilylmethyl group, diarylmethylsilylmethyl group, dimethylarylsilylmethyl group, and triarylsilylmethyl group are also preferable.

  The alkenyl group preferably has 2 to 20 carbon atoms, and specific examples thereof include a vinyl group, a styryl group, and a diphenylvinyl group.

  As the alkynyl group, those having 2 to 20 carbon atoms are preferable, and specific examples include a methylethynyl group, a phenylethynyl group, a trimethylsilylethynyl group, and the like.

  As the alkoxy group, those having 1 to 20 carbon atoms are preferable, and specific examples include methoxy group, ethoxy group, n-propoxy group, i-propoxy group, n-butoxy group, i-butoxy group, t-butoxy group, Examples include linear or branched alkoxy groups such as 2-ethylhexyloxy group.

  The aryloxy group preferably has 2 to 20 carbon atoms, and specific examples include a phenoxy group.

  As an alkylthio group, a C1-C20 thing is preferable and a methylthio group, an ethylthio group, etc. are mentioned as a specific example.

  As the arylthio group, those having 2 to 20 carbon atoms are preferable, and specific examples thereof include a phenylthio group.

  The amino group preferably has 0 to 30 carbon atoms, and examples thereof include alkylamino groups such as dimethylamino group, diethylamino group and diisopropylamino group, and arylamino groups such as diphenylamino group, ditolylamino group and carbazoyl group.

  As a carbonyl group, a C1-C20 thing is preferable and alkyl carbonyl groups, aryl carbonyl groups, etc., such as an acetyl group and a phenyl carbonyl group, are mentioned.

  As the oxycarbonyl group, those having 1 to 20 carbon atoms are preferable. A methoxycarbonyl group, an ethoxycarbonyl group, an n-propoxycarbonyl group, an i-propoxycarbonyl group, an n-butoxycarbonyl group, an i-butoxycarbonyl group, an n- Examples thereof include a hexoxycarbonyl group, an octoxycarbonyl group, a 2-propylpentoxycarbonyl group, a 2-ethylhexoxycarbonyl group, a cyclohexylmethoxycarbonyl group, and a benzyloxycarbonyl group.

  As a carbonyloxy group, a C1-C20 thing is preferable and an acetyloxy group, an ethylcarbonyloxy group, etc. are mentioned.

  As the silyl group, those having 1 to 20 carbon atoms are preferable, and specific examples include a silyl group having an alkyl group or an aryl group as a substituent such as a trimethylsilyl group, a dimethylphenyl group, or a triphenylsilyl group.

  As the boryl group, those having 1 to 20 carbon atoms are preferred, and examples thereof include a dimesitylboryl group substituted with an aryl group.

  The aromatic group is preferably one having 6 to 30 carbon atoms, and is not limited to a monocyclic group, and may be a condensed polycyclic hydrocarbon group or a condensed ring hydrocarbon group. For example, phenyl group, naphthyl group, biphenyl group, phenanthryl group, biphenylenyl group, triphenylene group, anthryl group, pyrenyl group, fluorenyl group, azulenyl group, acenaphthenyl group, fluoranthenyl group, naphthacenyl group, perylenyl group, pentacenyl group, triphenylenyl Group, aromatic hydrocarbon group such as terphenyl group, quarterphenyl group, pyridyl group, thienyl group, furyl group, pyrrole group, oxazole group, thiazole group, oxadiazole group, thiadiazole group, pyrazyl group, pyrimidyl group, pyrazoyl group Group, imidazolyl group, benzothienyl group, dibenzofuryl group, dibenzothienyl group, phenylcarbazoyl, phenoxathienyl group, xanthenyl group, benzofuranyl group, thianthenyl group, indolizinyl group, phenoxy group Jiniru group, phenothiazinyl group, acridinyl group, phenanthridinyl group, quinolyl group, isoquinolyl group, indolyl group, an aromatic heterocyclic group such as a quinoxalinyl group. Preferably, an aromatic hydrocarbon group such as phenyl group, naphthyl group, phenanthryl group, triphenylene group, anthryl group, pyrenyl group, fluorenyl group, acenaphthenyl group, fluoranthenyl group, perylenyl group, triphenylenyl group; pyridyl group, pyrazyl group , Pyrimidyl group, pyrazoyl group, quinolyl group, isoquinolyl group, imidazoyl group, acridinyl group, phenanthridinyl group, quinoxalinyl group, dibenzofuryl group, dibenzothienyl group, phenylcarbazoyl, xanthenyl group, phenoxazinyl group, etc. It is a cyclic group.

  The ring forming the condensed polycyclic aromatic group is preferably a cyclic alkyl group which may have a substituent, an aromatic hydrocarbon group which may have a substituent, or a substituent. An aromatic heterocyclic group. Specific examples of the cyclic alkyl group include a cyclopentyl group and a cyclohexyl group. A specific example of the aromatic hydrocarbon group is a phenyl group. Specific examples of the aromatic heterocyclic group include pyridyl group, thienyl group, furyl group, pyrrole group, oxazole group, thiazole group, oxadiazole group, thiadiazole group, pyrazyl group, pyrimidyl group, pyrazoyl group, as specific examples. An imidazolyl group, and the like. As the aromatic heterocyclic group, a pyridyl group and a thienyl group are preferable. The condensed polycyclic aromatic group is a group in which these rings are condensed.

The additional group R ²¹ may further have a substituent. Any substituent may be present in the additional group R ²¹ . For example, the additional group R ²¹ may have the group exemplified as the additional group R ²¹ as a substituent. When the additional group R ²¹ has a substituent, the number is not limited, but is preferably 1 to 3, and more preferably 1.

Further, substituents added group R ²¹ has may have further substituents. This further substituent well anything, for example, a substituent addition group R ²¹ has the groups mentioned as examples of additional radicals R ²¹ may have a further substituent.

When the substituent that the additional group R ²¹ or the additional group R ²¹ has has a coordination ability to a metal, a metal complex may be formed through a coordination bond with a metal atom.

The n-type semiconductor material according to this example is more preferably a fullerene compound having a structure represented by the general formula (B2) and / or (B3).

In the formulas (B2) and (B3), FLN represents fullerene as in the formula (1). In the formula, p and q are each an integer, and the sum of p and q is usually 1 to 5, preferably 1 to 3. The addition groups R ^{22 to} R ²⁴ each independently represent an addition group added to the fullerene skeleton. The addition groups R ^{22 to} R ²⁴ are preferably added to the same 5-membered ring or 6-membered ring in the fullerene skeleton. R ²² and R ²³ may form a ring directly or through a substituent. The addition groups R ^{22 to} R ²⁴ may be any group. For example, the additional groups R ^{22 to} R ²⁴ may be the groups given as examples of the additional group R ²¹ .

The n-type semiconductor material according to this example is more preferably a fullerene compound having at least one of the structures represented by the general formulas (B4) to (B7).

  In formulas (B4) to (B7), FLN represents fullerene as in formula (1). In the formula, r, s, t and u are each an integer, and the sum of r, s, t and u is usually 1 to 5, preferably 1 to 3. The structures represented by the general formulas (B4) to (B7) are preferably added to the same five-membered ring or six-membered ring in the fullerene skeleton. L is an integer of 1 to 8, preferably an integer of 1 to 4, and more preferably an integer of 1 to 2.

The additional groups R ^{25 to} R ³⁹ are each an independent group. Also, additional groups ^R 25 ^{to R 39} may be any group. For example, the additional groups R ^{25 to} R ³⁹ can be the groups listed as examples of the additional group R ²¹ . Ar ¹ can be any aromatic ring.

Further, a ring may be formed directly or through a substituent between R ³⁴ or R ³⁵ and R ³⁶ or R ³⁷ . Furthermore, a ring may be formed directly or via a substituent between any of R ^{34 to} R ³⁷ and the carbon atom forming the skeleton of the compound of formula (B6). For example, the n-type semiconductor material according to this embodiment can have a structure represented by the general formula (B8).

  In the formula (B8), X represents an oxygen atom or a sulfur atom, a nitrogen atom which may have a substituent, a methano group which may have a substituent, an ethano group which may have a substituent, and the like. sell. The substituent that the nitrogen atom may have may be an alkyl group having 1 to 6 carbon atoms such as a methyl group and an ethyl group. Moreover, as a substituent which a methano group or an ethano group may have, it may be a C1-C6 alkoxyl group such as a methoxy group or a C1-C5 hydrocarbon group. v may be an integer from 1 to t.

Preferably, as the structure of the formula (B7), R ³⁸ and R ³⁹ are both alkoxycarbonyl groups, R ³⁸ and R ³⁹ are both aromatic groups, or R ³⁸ is an aromatic group and R ³⁹ is R ^39. 3- (alkoxycarbonyl) propyl group.

  There is no restriction | limiting in particular as a manufacturing method of the above-mentioned fullerene compound. For example, fullerene having a structure represented by the formula (B4) can be obtained according to the method described in International Publication No. 2008/059771 or J. Am. Chem. Soc., 2008, 130 (46), 15429-15436. It can be synthesized. In addition, fullerenes having a structure represented by the formula (B5) are J. Am. Chem. Soc. 1993, 115, 9798-9799, Chem. Mater. 2007, 19, 5363-5372, or Chem. Mater. 2007. , 19, 5194-5199. In addition, fullerenes having a structure represented by the formula (B6) are Angew. Chem. Int. Ed. Engl. 1993, 32, 78-80, Tetrahedron Lett. 1997, 38, 285-288, or International Publication No. 2009. Can be synthesized according to the method described in Japanese Patent No. 086210. In addition, fullerenes having a structure represented by the formula (B7) are described in J. Chem. Soc., Perkin Trans. 1, 1997, 1595, Thin Solid Films 489 (2005) 251-256, Adv. Funct. Mater. It can be synthesized according to the method described in 2005, 15, 1979-1987, or J. Org. Chem. 1995, 60, 532-538.

  The n-type semiconductor material according to this example may include one type of compound or a plurality of compounds.

  Specific examples of the fullerene compound that can be used as the n-type semiconductor material according to this embodiment include the following.

  The glass transition temperature of the fullerene compound that can be used as the n-type semiconductor material according to this example is not particularly limited, but is preferably 250 ° C. or higher, and more preferably 280 ° C. or higher. The upper limit is not particularly limited and is usually 350 ° C. or lower, preferably 400 ° C. or lower, but the glass transition temperature may not be observed. When the glass transition temperature is low, the compound changes between an amorphous state and a crystalline state in the temperature range in the film forming process, and thus the functional stability as an n-type semiconductor is impaired. sell. What is necessary is just to measure a glass transition temperature by a well-known method, for example, DSC method is mentioned.

  The energy level of the lowest unoccupied molecular orbital (LUMO) of the fullerene compound that can be used as the n-type semiconductor material according to the present embodiment is not particularly limited, but is a value with respect to the vacuum level calculated by, for example, a cyclic voltammogram measurement method. Is usually −3.85 eV or more, preferably −3.80 eV or more. As described above, when the LUMO of the n-type semiconductor material is too low, the open circuit voltage of the photoelectric conversion element can be lowered.

[3 electrodes 120, 160]
The electrode according to this example has a function of collecting holes and electrons generated by light absorption. Therefore, the pair of electrodes includes an electrode 120 suitable for collecting holes (hereinafter also referred to as an anode) and an electrode 160 suitable for collecting electrons (hereinafter also referred to as a cathode). Is preferably used. Any one of the pair of electrodes may be translucent, and both may be translucent. Translucency means that sunlight passes through 40% or more. In addition, it is preferable that the transparent electrode has a solar ray transmittance of 70% or more in order to allow light to reach the active layer through the transparent electrode. The light transmittance can be measured with a normal spectrophotometer.

[3.1 Electrode 120 (Anode) Suitable for Collecting Holes]
For the electrode 120 (anode) suitable for collecting holes, it is generally preferable to use a conductive material having a work function higher than that of the cathode electrode. In this case, holes generated in the active layer can be taken out smoothly.

  Examples of the material of the anode 120 include conductive metal oxidation such as nickel oxide, tin oxide, indium oxide, indium tin oxide (ITO), indium-zirconium oxide (IZO), titanium oxide, indium oxide, and zinc oxide. And metals such as gold, platinum, silver, chromium, and cobalt, or alloys thereof.

  These materials are preferred because they have a high work function. Further, these materials are preferable because a conductive polymer material represented by PEDOT / PSS in which a polythiophene derivative is doped with polystyrene sulfonic acid can be laminated. When such a conductive polymer is laminated, since the work function of the conductive polymer material is high, it is suitable for a cathode such as Al or Mg instead of the high work function material as described above. It is also possible to use a metal.

  PEDOT / PSS in which a polythiophene derivative is doped with polystyrene sulfonic acid, or a conductive polymer material in which polypyrrole, polyaniline, or the like is doped with iodine or the like can also be used as the material of the anode 120.

  Further, when the anode 120 is a transparent electrode, it is preferable to use a light-transmitting conductive metal oxide such as ITO, zinc oxide, or tin oxide, and ITO is particularly preferable.

  The thickness of the anode 120 is not particularly limited, but is 10 nm to 10 μm, preferably 20 nm to 1 μm, and more preferably 50 nm to 500 nm. If it is too thin, the sheet resistance increases, and if it is too thick, the light transmittance decreases. When used for a transparent electrode, it is necessary to select a film thickness that achieves both light transmittance and sheet resistance.

The sheet resistance of the anode 120 is not particularly limited, but is usually 1Ω / □ or more, on the other hand, 1000Ω / □ or less, preferably 500Ω / □ or less, more preferably 100Ω / □ or less. From the viewpoint of extracting a larger current, the sheet resistance is preferably small.
[3.2 Electrode 160 (Cathode) Suitable for Electron Collection]

  The material of the electrode 160 (cathode) suitable for collecting electrons is generally preferably a conductive material having a work function higher than that of the anode 120. In this case, the cathode 160 can smoothly extract electrons generated in the active layer. When the photoelectric conversion element according to this example includes the buffer layer 150 (electron extraction layer), the electrode 160 is preferably adjacent to the buffer layer 150.

  Examples of the material of the cathode 160 include metals such as platinum, gold, silver, copper, iron, tin, zinc, aluminum, indium, chromium, lithium, sodium, potassium, cesium, calcium and magnesium, and alloys thereof, fluoride Examples thereof include inorganic salts such as lithium and cesium fluoride, and metal oxides such as nickel oxide, aluminum oxide, lithium oxide, and cesium oxide. These materials are preferable because they are materials having a low work function.

  In addition, the photoelectric conversion element 100 according to this embodiment may include an electron extraction layer 150 between the cathode 160 and the active layer 140. For example, the electron extraction layer 150 can be made of an n-type semiconductor such as titania and a conductive material. In this case, as the material of the cathode 160, a material having a high work function suitable for the anode can be used. From the viewpoint of electrode protection, a material suitable for the anode is preferably a metal such as platinum, gold, silver, copper, iron, tin, aluminum, calcium and indium, or an alloy using these metals.

  The film thickness of the cathode 160 is not particularly limited, but is 10 nm or more and 10 μm or less, preferably 20 nm or more and 1 μm or less, and more preferably 50 nm or more and 500 nm or less. When used for a transparent electrode, it is necessary to select a film thickness that achieves both light transmittance and sheet resistance. If it is too thin, the sheet resistance increases, and if it is too thick, the light transmittance decreases.

  The sheet resistance of the cathode 160 is not particularly limited, but is 1000Ω / □ or less, preferably 500Ω / □ or less, and more preferably 100Ω / □ or less. Although there is no restriction on the lower limit, it is usually 1Ω / □ or more. The smaller the sheet resistance, the more efficiently the current can be taken out.

[3.3 Method for Forming Electrodes 120 and 160]
Examples of a method for forming the electrodes 120 and 160 include a vacuum film formation method such as vapor deposition and sputtering, and a method in which an ink containing nanoparticles or an electrode material precursor is applied to form a film. Further, the electrodes 120 and 160 may have a laminated structure including two or more layers. In addition, characteristics (electric characteristics, wetting characteristics, etc.) may be improved by subjecting the electrodes 120 and 160 to surface treatment.

[4 Substrate 110]
The photoelectric conversion element 100 according to the present embodiment has a substrate 110 that is normally a support. That is, the electrodes 120 and 160 and the active layer 140 are formed on the substrate 110. The material of the substrate 100 (substrate material) is arbitrary as long as the effects of the present invention are not significantly impaired. Preferred examples of the substrate material include inorganic materials such as quartz, glass, sapphire, and titania; polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyimide, nylon, polystyrene, polyvinyl alcohol, ethylene vinyl alcohol copolymer, Organic materials such as fluororesin film, polyolefins such as vinyl chloride and polyethylene, cellulose, polyvinylidene chloride, aramid, polyphenylene sulfide, polyurethane, polycarbonate, polyarylate, polynorbornene, and epoxy resins; paper materials such as paper and synthetic paper; Examples thereof include composite materials such as those obtained by coating or laminating the surface of a metal such as stainless steel, titanium, or aluminum in order to provide insulation. Examples of the glass include soda glass, blue plate glass, and alkali-free glass. As for the glass material, alkali-free glass is preferred because it is better that there are fewer ions eluted from the glass.

  There is no restriction | limiting in the shape of a board | substrate, For example, shapes, such as a board, a film, a sheet | seat, can be used. There is no limitation on the thickness of the substrate. However, it is preferably 5 μm or more, especially 20 μm or more, and usually 20 mm or less, especially 10 mm or less. If the substrate is too thin, the strength of the semiconductor device may be insufficient, and if the substrate is too thick, the cost may be increased or the weight may be increased. Further, when the substrate is made of glass, if it is too thin, the mechanical strength is lowered and the substrate is easily broken, so that the thickness is preferably 0.01 mm or more, more preferably 0.1 mm or more. Moreover, since weight will become heavy when too thick, Preferably it is 1 cm or less, More preferably, it is 0.5 cm or less.

[5 Buffer layers 130 and 150]
The photoelectric conversion element 100 according to this embodiment can further include one or more buffer layers in addition to the pair of electrodes 120 and 160 and the active layer 140 disposed therebetween. The buffer layer can be classified into a hole extraction layer 130 and an electron extraction layer 150. Usually, the hole extraction layer 130 is disposed between the active layer 140 and the anode 120, and the electron extraction layer 150 is disposed between the active layer 140 and the cathode 160.

[5.1 Electron extraction layer 150]
The material of the electron extraction layer 150 is not particularly limited as long as it can improve the efficiency of extracting electrons from the active layer 140 to the cathode 160. Specifically, bathocuproin (BCP) or bathophenanthrene (Bphen), (8-hydroxyquinolinato) aluminum (Alq3), boron compound, oxadiazole compound, benzimidazole compound, naphthalenetetracarboxylic anhydride (NTCDA) Perylenetetracarboxylic anhydride (PTCDA), phosphine oxide compounds, and phosphine sulfide compounds. Among them, a phosphine oxide compound substituted with an aryl group and a phosphine sulfide compound substituted with an aryl group are preferable, and two triaryl phosphine oxide compounds, triaryl phosphine sulfide compounds, and two diaryl phosphine oxide units are more preferable. Aromatic hydrocarbon compounds having two or more diarylphosphine sulfide units, triarylphosphine oxide compounds composed of aryl substituted with fluorine atoms or perfluoroalkyl groups, two or more diarylphosphine oxide units It is an aromatic hydrocarbon compound. In addition to the above materials, alkali metal or alkaline earth metal may be doped.

式中、Ｒ^５１〜Ｒ^５２は各々独立して置換基を有しても良い縮合多環芳香族基もしくは芳香族基を表わし、ｎは１以上の整数を表す。Ｒ^５３は芳香族基である。Ｘは酸素原子もしくは硫黄原子である。Ｒ^５１，Ｒ^５２，Ｒ^５３は、例えば、付加基Ｒ^２１について挙げた上述の基でありうる。 The phosphine oxide compound substituted with an aryl group and the phosphine sulfide compound substituted with an aryl group can be, for example, a compound represented by the following general formula.

In the formula, R ^{51 to} R ⁵² each independently represents a condensed polycyclic aromatic group or an aromatic group which may have a substituent, and n represents an integer of 1 or more. R ⁵³ is an aromatic group. X is an oxygen atom or a sulfur atom. R ⁵¹ , R ⁵² , and R ⁵³ can be, for example, the above-described groups mentioned for the additional group R ²¹ .

  Although there is no limitation in particular as a glass transition temperature of the compound used with the electron extraction layer which concerns on a present Example, 50 degreeC or more is preferable, More preferably, it is 80 degreeC or more. The upper limit is not particularly limited, and it is also preferably a compound whose glass transition temperature by DSC method is not observed below 300 ° C.

  If the glass transition temperature is too low, the organic compound tends to change in structure with respect to external stress such as applied electric field, flowing current, stress due to bending or temperature change, and this causes a problem in terms of durability. In addition, if the glass transition temperature is too low, crystallization of the thin film of the organic compound tends to proceed, so that the organic compound changes between an amorphous state and a crystalline state in the operating temperature range, thereby causing an electron. Since the stability as the extraction layer is lost, there is a problem in terms of durability. Among the compounds that can be used as the electron extraction layer 150 according to this example, there are compounds in which the glass transition temperature by the DSC method is not observed below 300 ° C., which is preferable because it has high thermal stability. Is.

  The thickness of the electron extraction layer 150 is not particularly limited, but is preferably 0.01 nm or more. Moreover, it is preferably 40 nm or less, and more preferably 20 nm or less. There is a problem that it becomes difficult to take out too large electrons and the photoelectric conversion efficiency is lowered, and when it is too small, there is a problem that the function as a buffer material cannot be performed.

[5.2 Hole Extraction Layer 130]
The material of the hole extraction layer 130 is not particularly limited as long as it can improve the efficiency of extracting holes from the active layer 140 to the anode 120. Specific examples include conductive organic compounds such as polythiophene, polypyrrole, polyacetylene, and triphenylenediamine. A thin film of metal such as Au, In, Ag, and Pd can also be used. Further, a thin film of metal or the like can be used alone as the hole extraction layer 130, or a thin film of metal or the like and the above organic material can be used in combination as the hole extraction layer 130.

  The thickness of the hole extraction layer is not particularly limited, but is usually 2 nm or more, and usually 40 nm or less, preferably 20 nm or less. When it is too thick, it becomes difficult to extract holes, and the photoelectric conversion efficiency tends to decrease. On the other hand, if it is too thin, for example, a uniform film cannot be obtained, so that the function as a buffer material may not be achieved.

[5.2 Film Formation Method of Buffer Layers 130 and 150]
The formation method of the buffer layers 120 and 160 is arbitrary. For example, a vacuum film formation method such as vapor deposition or sputtering may be used, or a coating film formation method such as spin coating may be used.

[6 Annealing treatment]
In order to improve the performance of the photoelectric conversion element, it is preferable to heat (anneal) the stacked structure after forming the stacked structure including the active layer 140 and the electrodes 120 and 160. Specifically, when producing the photoelectric conversion element 100, the laminated structure is usually heated in a temperature range of 50 ° C. or higher, more preferably 80 ° C. or higher, and usually 280 ° C. or lower, more preferably 250 ° C. or lower. It is preferable. If the annealing temperature is too low, for example, the adhesion between the electron extraction layer 150 and the cathode 160 and between the electron extraction layer 150 and the active layer 140 may not be sufficiently improved. If the annealing temperature is too high, for example, a compound contained in the active layer 140 may be thermally decomposed. Note that the annealing treatment may include heating at a plurality of temperatures.

  The heating time is usually 1 minute or longer, preferably 3 minutes or longer, and usually 3 hours or shorter, preferably 1 hour or shorter. The annealing treatment is preferably terminated when the open circuit voltage, short circuit current, and fill factor, which are parameters of the solar cell performance, reach constant values. The annealing treatment is preferably performed under normal pressure, and is preferably performed in an inert gas atmosphere.

  By the annealing treatment, for example, adhesion between the electron extraction layer 150 and the cathode 160 and between the electron extraction layer 150 and the active layer 140 can be improved. In this case, the thermal stability and durability of the photoelectric conversion element 100 can be improved. In addition, the self-organization of the active layer 140 is promoted, and conversion efficiency can be improved. As a heating method, the laminated structure may be placed on a heat source such as a hot plate, or the laminated structure may be put in a heating atmosphere such as an oven. Further, the annealing treatment may be performed according to a batch production method, or the annealing treatment may be performed according to a continuous production method.

[7 Solar Cell According to the Present Invention]
A solar cell can be produced using the photoelectric conversion element according to the present invention. In particular, the photoelectric conversion element according to the present invention is preferably used as a solar cell element in a solar cell (or a solar cell module).

  There is no restriction | limiting in the preparation methods of the solar cell concerning this invention. For example, a solar cell can be manufactured by using a sealing material and sealing a photoelectric conversion element between film-like or sheet-like members. As a film-like or sheet-like member, for example, a glass plate can be used.

  Moreover, it is preferable that the photoelectric conversion element which concerns on this invention is used as a solar cell element in a thin film solar cell. Such a thin film solar cell can be manufactured as follows, for example. That is, one or two or more photoelectric conversion elements may be connected in series or in parallel between film-like or sheet-like members and laminated with a general vacuum laminating apparatus using a sealing material. A weather-resistant protective film can also be used as the film. In addition, the thin film solar cell may include at least one of an ultraviolet cut film, a gas barrier film, and a getter material film supplementing oxygen and / or moisture together with the photoelectric conversion element.

  EXAMPLES Hereinafter, although the Example of this invention is shown and this invention is demonstrated more concretely, this invention is not limited to a following example, unless it deviates from the summary.

[Synthesis Example 1: Synthesis of bicycloporphyrin compound CP-1]
(Synthesis of Compound E2)

In a 500 mL four-necked flask equipped with a condenser under a nitrogen atmosphere, ethyl-4,7-dihydro-8,8-dimethyl-4,7-ethano-2H-isoindole-1-carboxylate (E1) ( 5.00 g, 20.4 mmol) and sodium hydroxide (6.25 g, 150 mmol) previously ground in a mortar were dissolved in ethylene glycol (150 mL), and the solvent was degassed and replaced with nitrogen. The reaction vessel was shielded from light, stirred at 170 ° C. for 60 minutes, and then cooled to room temperature. The reaction solution was poured into ice water (300 mL), extracted with chloroform, anhydrous sodium sulfate was added, and the organic layer was dried. After filtering the powder, the filtrate was concentrated under reduced pressure. The obtained oil was purified by sublimation to obtain compound (E2) (2.54 g, 14.7 mmol, 72%). It was confirmed by ¹ H NMR that the obtained compound was the compound (E2). The result of ¹ H NMR is shown below.

Compound (E2): ¹ H NMR (400 MHz, CDCl ₃ ) δ 7.46 (br s, 1H), 6.54 (m, 1H), 6.48 (m, 1H), 6.47 (m, 1H), 6.41 (m, 1H ), 3.70 (m, 1H), 3.22 (d, 1H, J = 5.9 Hz), 1.41 (dd, 1H, J = 11.5, 2.7 Hz), 1.24 (dd, 1H, J = 11.5, 2.7 Hz), 1.04 (s, 3H), and 0.72 (s, 3H).

(Synthesis of Bicycloporphyrin Compound Isomeric Mixture CP-1)

  Compound (E2) synthesized as described above (3.81 g, 22 mmol) was dissolved in chloroform (containing amylene) (400 mL), and paraformaldehyde (850 mg) was added thereto under a nitrogen atmosphere. Toluenesulfonic acid monohydrate (200 mg) was added and stirred at room temperature for 5 hours. Subsequently, p-chloranil (2.17 g) was added and stirred for another 5 hours. The reaction solution was poured into water, the organic layer was separated, washed successively with saturated sodium hydrogen carbonate solution, water, and saturated brine, and dried over anhydrous sodium sulfate. After filtering the powder, the filtrate was concentrated under reduced pressure. The residue was purified by alumina column chromatography (solvent: chloroform) and then purified by silica gel chromatography (solvent: ethyl acetate / chloroform) to obtain a regioisomer mixture CP-1 of a bicycloporphyrin compound (2.44 g). , 3.30 mmol, 60%).

It was confirmed by ¹ H NMR, LC analysis, and MS analysis that the obtained compound was a regioisomer mixture of the target bicycloporphyrin compound. That is, m / z: 736 [M ⁺ ] corresponding to the mass of the target product was detected by mass spectrometry (FAB-MS method). The LC analysis results are shown in Table 1. The results of ¹ H NMR are shown below.

Bicycloporphyrin compound isomer mixture CP-1: ¹ H NMR (400 MHz, CDCl ₃ ) δ 10.26-10.33 (m, 4H), 7.11-7.26 (m, 8H), 5.63 (m, 4H), 5.12-5.16 ( m, 4H), 2.06-2.11 (m, 4H), 1.75-1.88 (m, 4H), 1.55-1.56 (m, 12H), 0.59-0.80 (m, 12H), and -4.63 (br s, 2H) .

[Synthesis Example 2: Synthesis of bicycloporphyrin compound CP-2]

The compound was synthesized according to the description in paragraphs [0060] to [0066] of JP-A-2003-304014. By mass spectrometry (FAB-MS method), m / z: 623 [M ⁺ +1] consistent with the mass of the target product was detected. The LC analysis results of the obtained compound are shown in Table 1.

Tetrakis (bicyclo [2.2.2] octadiene) porphyrin (CP-2): ¹ H NMR (400 MHz, CDCl ₃ ) δ 10.40 (m, 4H), 7.20 (m, 8H), 5.81 (m, 8H) , 2.24 (m, 8H), and -4.80 (br s, 2H).

ＳＩＭＥＦ２（フラーレン化合物Ａ）の合成は、以下のように行った。 [Synthesis Example 3: Synthesis of SIMEF2 (fullerene compound A)]

The synthesis of SIMEF2 (fullerene compound A) was performed as follows.

(Synthesis of Intermediate E12)

To a 500 mL three-necked eggplant flask, a 1.0 M THF solution (100 mL, 0.1 mol) of 2-methoxyphenylmagnesium bromide (E11) was added under a nitrogen atmosphere and stirred at room temperature. Chloromethyldimethylchlorosilane (11.25 mL, 0.085 mol) was slowly added dropwise thereto. After stirring at room temperature for 1 hour, the mixture was stirred at 40 ° C. for 3 hours. It returned to room temperature and water was added slowly. The mixture was extracted with ethyl acetate, washed with saturated brine, dried over sodium sulfate, filtered, and concentrated under reduced pressure. The obtained liquid was distilled under reduced pressure to obtain the desired product (chloromethyl (2-methoxyphenyl) dimethylsilane ((o-MeO-Ph) Me ₂ SiCH ₂ Cl) (E12) as a colorless liquid (11.2 g). , 0.0522 mol, 52%).

(Synthesis of Intermediate E14)

Under a nitrogen atmosphere, N, N-dimethylformamide (6.45 mL, 83.3 mmol), fullerene C ₆₀ (E13) (2.00 g, 2.78 mmol), and 1,2-dichlorobenzene (500 mL) were mixed and degassed. Then, the pressure was restored with nitrogen. A THF solution (9.80 mL, 0.850 M, 8.33 mmol) of dimethylphenylsilylmethyl magnesium chloride (PhMe ₂ SiCH ₂ MgCl) was added thereto at 25 ° C. After stirring for 10 minutes, degassed saturated aqueous ammonium chloride solution (1.0 mL) was added and stirred. The resulting solution was concentrated, passed through toluene (200 mL) and a silica gel filtration column, and concentrated. Methanol (ca. 100-200 mL) was added and reprecipitated to obtain a brown solid. The obtained solid was separated by HPLC (Buckyprep column, solvent: toluene / 2-propanol = 7/3) to obtain 1- (dimethylphenylsilylmethyl) -1,9-dihydro (C ₆₀ -I _h) [5,6] to obtain a fullerene _{(C 60 (CH 2 SiMe 2} Ph) H) (E14) (1.99 g, 2.28 mmol, 82% isolated yield, analytically pure).

(Synthesis of SIMEF2 (fullerene compound A))

After degassing the benzonitrile solution of intermediate (E14) (1.02 g, 1.17 mmol) obtained as described above under a nitrogen atmosphere, THF solution (1.41 mL, 1.0 M, 1.41 mmol) of t-butoxypotassium was used. Was added at 25 ° C. After stirring for 10 minutes, the intermediate (E12) (5.03 g, 23.4 mmol) obtained above and potassium iodide were added and stirred at 110 ° C. for 17 hours. To the resulting solution, 1.0 mL of saturated aqueous ammonium chloride solution was added and concentrated. Toluene (100 mL) was added to the obtained crude product, and after concentration by filtration, methanol (ca. 50-100 mL) was added to perform reprecipitation. The obtained crude product was produced by silica gel column chromatography (solvent: carbon disulfide / hexane = 1/1), followed by HPLC fractionation (Buckyprep column, solvent: toluene / 2-propanol = 7/3). _{purification, SIMEF2 (C 60 (CH 2} SiMe 2 Ph) [CH 2 SiMe 2 (o-MeO-Ph)]) was obtained (0.810 g, 0.772 mmol, 66 % isolated yield).

[Synthesis Example 4: Synthesis of C ₆₀ (QM) ₂ (fullerene compound B)]

Under a nitrogen atmosphere, in a 500 mL three-necked eggplant flask, fullerene C ₆₀ (E13) (500 mg, 0.694 mmol), tetra n-butylammonium iodide (TBAI) (1.28 g, 3.47 mmol, 5 mol eq.), And toluene ( 230 mL) was added. After degassing under reduced pressure, α, α'-dibromo-o-xylene (916 mg, 3.47 mmol, 5 mol eq.) Was added and heated to reflux. After 10 hours, the temperature was returned to room temperature, passed through a silica gel filtration column (solvent: toluene), and then concentrated. After purification by silica gel column chromatography (solvent: carbon disulfide / hexane = 1/2), further GPC purification (solvent: chloroform) is performed to obtain the target product C ₆₀ (QM) ₂ (fullerene compound B). Got. (304 mg, 0.328 mmol, 47%). By mass spectrometry (APCI method, negative), m / z: 928 [M ⁻ ] corresponding to the mass of the target product was detected.

[Synthesis Example 5: Synthesis of POPy ₂ ]

  In a nitrogen atmosphere, 1-bromopyrene (E21) (manufactured by Tokyo Chemical Industry) (14 g, 50 mmol) was dissolved in dehydrated THF (manufactured by Kanto Chemical) (200 mL), cooled to -78 ° C. (Chemical) (33 mL, 1.6 M, 53 mmol) was slowly added dropwise, and the mixture was stirred for 30 minutes while maintaining -78 ° C. Subsequently, dichlorophenylphosphine (manufactured by Tokyo Chemical Industry) (4.3 g, 9.0 mmol) was added dropwise, stirred for 10 minutes, then warmed to room temperature, and further stirred for 1.5 hours. Methanol (manufactured by Junsei Kagaku) (30 mL) was added to the obtained reaction solution, and the resulting crude product was filtered and recrystallized using benzene to obtain an intermediate (E22) (10.7 g). ).

The obtained intermediate (E22) was dissolved in THF (manufactured by Junsei Chemical) (350 mL), dichloromethane (manufactured by Kanto Chemical) (300 mL), and acetone (manufactured by Kanto Chemical) (100 mL), and further hydrogen peroxide. Water (manufactured by Wako Pure Chemical Industries, Ltd.) (30%, 10 mL) was added, and the mixture was stirred at room temperature for 30 minutes. Water (30 mL) was added to the reaction solution, and the mixture was concentrated to a total volume of 600 mL, followed by filtration to obtain the target compound POPy ₂ (7.5 g).

[Example 1: Production and evaluation of photoelectric conversion device according to the present invention]
First, a hole extraction layer was formed on the substrate. A poly (3,4-ethylenedioxythiophene) poly (styrenesulfonic acid) aqueous dispersion (manufactured by H.C. Starck, Inc., trade name “CLEVIOUS ^™ PVP” as a hole extraction layer on a glass substrate on which an ITO electrode is patterned. AI4083 ") was applied by spin coating, and then the substrate was subjected to heat treatment on the hot plate at 120 ° C for 10 minutes in the air. The film thickness of the hole extraction layer was about 30 nm.

  Subsequently, an active layer was formed on the hole extraction layer. In this embodiment, the active layer includes a p-type semiconductor layer, a mixed layer (i layer), and an n-type semiconductor layer.

  Specifically, first, a p-type semiconductor layer was formed on the hole extraction layer. That is, the substrate on which the hole extraction layer was formed was first heat-treated at 180 ° C. for 3 minutes in a nitrogen atmosphere. Next, a toluene solution containing 0.4% by weight of the bicycloporphyrin compound CP-1 synthesized in Synthesis Example 1 was prepared, filtered, and applied by spin coating on the substrate at 1500 rpm. Further, the substrate was heat-treated at 195 ° C. for 30 seconds in a nitrogen atmosphere. Bicycloporphyrin compound CP-1 is converted into tetrabenzoporphyrin (BP) which is a p-type semiconductor material by heat treatment. Thus, a p-type semiconductor layer of about 25 nm was formed on the hole extraction layer.

  Next, a mixture layer was formed on the p-type semiconductor layer. That is, chloroform: chlorobenzene = 1: 1 (containing 0.75% by weight of the bicycloporphyrin compound CP-2 synthesized in Synthesis Example 2 and 1.75% by weight of SIMEF2 (fullerene compound A) produced in Synthesis Example 3) (Weight ratio) solution was prepared. The prepared solution was filtered, and the filtrate obtained under a nitrogen atmosphere was spin-coated on the p-type semiconductor layer at 1500 rpm and heated at 160 ° C. for 120 minutes. Bicycloporphyrin compound CP-2 is converted into tetrabenzoporphyrin (BP) which is a p-type semiconductor material by heat treatment. Thus, a layer of about 100 nm containing tetrabenzoporphyrin (BP) and SIMEF2 was formed on the p-type semiconductor layer.

Next, an n-type semiconductor layer was formed on the layer containing tetrabenzoporphyrin (BP) and SIMEF2. That is, a toluene solution containing 0.65% by weight of C ₆₀ (QM) ₂ (fullerene compound B), which is an n-type semiconductor material, synthesized in Synthesis Example 4 was prepared. The prepared solution was filtered, and the filtrate obtained under a nitrogen atmosphere was spin-coated at 3000 rpm. By this treatment, SIMEF2 is replaced by the fullerene compound B. Further, the substrate after spin coating was subjected to heat treatment at 120 ° C. for 5 minutes. Through the above steps, a mixture layer (i layer) containing tetrabenzoporphyrin (BP) and fullerene compound B is formed on the p-type semiconductor layer, and an n-type semiconductor layer containing fullerene compound B is further formed on the mixture layer. It was done.

  A thin film X-ray diffraction spectrum was measured for the active layer thus formed. Table 2 shows peaks and their relative intensities for both the diffraction pattern in out-of-plane measurement and the diffraction pattern in in-plane measurement. Furthermore, the UV-Vis transmission light spectrum was measured about this active layer. The obtained UV-Vis transmitted light spectrum is shown in FIG. Table 3 shows the absorption maximum wavelength λmax and its half-value width for the absorption peak in the Q band (wavelength range: 670 to 700 nm).

Subsequently, a buffer layer was formed on the active layer. That is, POPy ₂ synthesized in Synthesis Example 5 was placed in a metal boat placed in a vacuum vapor deposition apparatus and heated to deposit POPy ₂ on the active layer until the film thickness reached 6 nm.

  Then, an aluminum electrode having a thickness of 80 nm was provided on the buffer layer by vacuum deposition. After providing the electrodes, the manufactured laminate was heated on a 180 ° C. hot plate for 10 minutes, further heated on a 210 ° C. hot plate for 10 minutes, further heated on a 220 ° C. hot plate for 10 minutes, and further 230 ° C. The photoelectric conversion element was produced by heating with a hot plate for 10 minutes.

About the produced photoelectric conversion element, the characteristic was measured as follows. That is, the solar cell was produced by sealing the obtained photoelectric conversion element using a glass plate as a sealing plate. Then, a solar simulator (AM1.5G) is used to irradiate light with an intensity of 100 mW / cm ² from the ITO electrode side of the photoelectric conversion element, and using a source meter (type 2400, manufactured by Keithley), an ITO electrode and an aluminum electrode The current-voltage characteristics during the period were measured.

  Twenty photoelectric conversion elements were produced using the above method. And the open circuit voltage (Voc) of the photoelectric conversion element, the short circuit current (Jsc), the fill factor (FF), and the photoelectric conversion efficiency (PCE) were measured about each of 20 photoelectric conversion elements. Table 4 shows the average and standard deviation of the 20 open-circuit voltages (Voc), short-circuit current (Jsc), fill factor (FF), and photoelectric conversion efficiency (PCE) for 20 photoelectric conversion elements. Furthermore, Table 4 shows the ratio (%) of photoelectric conversion elements in which leakage current was observed among the 20 photoelectric conversion elements.

[Comparative Example 1: Production and Evaluation of Photoelectric Conversion Element as Comparative Example]
A photoelectric conversion element was produced in the same manner as in Example 1 except that, when the p-type semiconductor layer was formed, heat treatment was performed at 180 ° C. for 20 minutes instead of heat treatment at 195 ° C. for 30 seconds. Moreover, the thin film X-ray diffraction spectrum of the active layer was measured in the same manner as in Example 1, and the current-voltage characteristics of the photoelectric conversion element were further measured. The results are shown in FIG. 2 and Tables 2 to 4 as in Example 1.

  As described above, in the thin film X-ray diffraction spectrum of the active layer by the out-of-plane measurement method, the photoelectric conversion element according to Example 1 has a lattice plane [10] with respect to the diffraction peak corresponding to the lattice plane [10-1]. 101], the lattice plane [002], the lattice plane [200], the lattice plane [202], and the lattice plane [004], the relative intensity of the peaks is higher than that of the photoelectric conversion element according to Comparative Example 1. In addition, regarding the absorption peak in the Q band of the active layer, the photoelectric conversion element according to Example 1 has a larger half-width than the photoelectric conversion element according to Comparative Example 1. That is, since the photoelectric conversion element according to Example 1 can absorb light having a wider wavelength, it is expected that the photoelectric conversion efficiency is improved.

  Moreover, it turns out that the short circuit current (Jsc) and photoelectric conversion efficiency (PCE) improved the photoelectric conversion element which concerns on Example 1 compared with the photoelectric conversion element which concerns on the comparative example 1. FIG. It can also be seen that the number of photoelectric conversion elements in which leakage current was observed was greatly reduced.

Claims (11)

A photoelectric conversion element having at least a pair of electrodes and an active layer,
In the thin-film X-ray diffraction spectrum of the active layer obtained by the out-of-plane measurement method, there are a diffraction peak corresponding to the lattice plane [10-1] and a diffraction peak corresponding to the lattice plane [101]. The relative intensity of the diffraction peak corresponding to the lattice plane [101] with respect to the diffraction peak corresponding to 10-1] is 40% or more.   In the thin film X-ray diffraction spectrum of the active layer obtained by the out-of-plane measurement method, there is a diffraction peak corresponding to the lattice plane [002], and the lattice plane corresponding to the diffraction peak corresponding to the lattice plane [10-1] [ The photoelectric conversion element according to claim 1, wherein a relative intensity of a diffraction peak corresponding to 002] is 30% or more.   In the thin-film X-ray diffraction spectrum of the active layer by the out-of-plane measurement method, there is a diffraction peak corresponding to the lattice plane [200], and the lattice plane corresponding to the diffraction peak corresponding to the lattice plane [10-1] [ The photoelectric conversion element according to claim 1 or 2, wherein the relative intensity of the diffraction peak corresponding to 200] is 50% or more.   In the thin film X-ray diffraction spectrum of the active layer obtained by the out-of-plane measurement method, there is a diffraction peak corresponding to the lattice plane [202], and the lattice plane corresponding to the diffraction peak corresponding to the lattice plane [10-1] [ 202], the relative intensity of a diffraction peak corresponding to 202] is 15% or more, and the photoelectric conversion element according to any one of claims 1 to 3.   In the thin-film X-ray diffraction spectrum of the active layer by the out-of-plane measurement method, there is a diffraction peak corresponding to the lattice plane [004], and the lattice plane corresponding to the diffraction peak corresponding to the lattice plane [10-1] [ The photoelectric conversion element according to any one of claims 1 to 4, wherein the relative intensity of the diffraction peak corresponding to [004] is 20% or more.   The photoelectric conversion element according to claim 1, wherein the active layer contains a porphyrin compound. A photoelectric conversion element having at least a pair of electrodes and an active layer,
The active layer contains a porphyrin compound;
In the ultraviolet visible transmission spectrum of the active layer, the half width of a peak having an absorption maximum wavelength in the range of 670 to 700 nm is 40 nm or more. The active layer is
Applying a semiconductor material precursor;
Converting the semiconductor material precursor into a semiconductor material compound;
The photoelectric conversion element according to claim 1, wherein the photoelectric conversion element is formed by a method including: A photoelectric conversion element having at least a pair of electrodes and an active layer,
The active layer is
Forming a first layer including a first semiconductor material; and a second layer adjacent to the first semiconductor layer and including the first semiconductor material and the second material;
Simultaneously crystallizing the first semiconductor material contained in the first layer and the first semiconductor material contained in the second layer;
It is formed by the method containing this, The photoelectric conversion element characterized by the above-mentioned. A photoelectric conversion element having at least a pair of electrodes and an active layer,
The active layer is
After the step of forming a first layer including a first semiconductor material and a second layer adjacent to the first semiconductor layer and including a second semiconductor material,
A step of crystallizing the first semiconductor material contained in the first layer, or the first semiconductor material contained in the first layer and the second semiconductor contained in the second layer. It is formed by performing the process of crystallizing material simultaneously, The photoelectric conversion element characterized by the above-mentioned.   A solar cell provided with the photoelectric conversion element of any one of Claims 1 thru | or 10.

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