JP7086573B2 - Photoelectric conversion element, optical area sensor using it, image sensor, image sensor - Google Patents

Description

The present invention relates to a photoelectric conversion element provided with a photoelectric conversion layer made of an organic semiconductor.

In recent years, the development of a solid-state image sensor having a photoelectric conversion layer made of an organic compound and having a structure formed on a signal readout substrate has been progressing.
As a general structure of the organic photoelectric conversion layer, there is a bulk heterostructure formed by mixing two organic compounds of a p-type organic semiconductor and an n-type organic semiconductor, and a third organic semiconductor is added thereto. As a result, photoelectric conversion elements that exhibit higher performance are being developed.
In Patent Document 1, as a photoelectric conversion layer having excellent heat resistance that suppresses an increase in dark current due to an increase in temperature, a small amount of low molecular weight organic compound is provided in addition to the bulk heterostructure of a p-type organic semiconductor and an n-type organic semiconductor. The contained structure is disclosed. Further, Patent Document 2 discloses a photoelectric conversion layer having an improved absorption efficiency of incident light by having a structure containing two or more kinds of electron-donating polymer organic materials in addition to an electron-accepting material. Has been done.

JP-A-2015-92546 Japanese Unexamined Patent Publication No. 2005-32793 International Publication No. 2014/104315 Pamphlet

Advanced Functional Materials, 2011, Volume21, 4, p. 699-707

In Patent Documents 1 and 2, a third compound is added in addition to the p-type organic semiconductor and the n-type organic semiconductor as a photoelectric conversion layer made of an organic compound to suppress an increase in dark current due to an increase in temperature. Alternatively, it is disclosed to increase the absorption efficiency of incident light. However, there is no disclosure about a configuration for reducing the dark current of the photoelectric conversion element at room temperature.
An object of the present invention is to reduce dark current and improve sensitivity in a photoelectric conversion element having a photoelectric conversion layer having a bulk heterostructure of a p-type organic semiconductor and an n-type organic semiconductor, and to use the photoelectric conversion element to reduce noise. It is an object of the present invention to provide an optical area sensor, an image pickup element, and an image pickup device.

（一般式［２８］において、
Ｒ ₁ は水素原子、ハロゲン原子、置換或いは無置換のアルキル基、置換或いは無置換のアルコキシ基、置換或いは無置換のアリール基、置換或いは無置換の複素環基、置換或いは無置換のビニル基、置換或いは無置換のアミノ基、シアノ基を表す。
Ｒ ₃₉₁ 乃至Ｒ ₃₉₆ は水素原子、ハロゲン原子、置換或いは無置換のアルキル基、置換或いは無置換のアルコキシ基、置換或いは無置換のアリール基、置換或いは無置換の複素環基、置換或いは無置換のビニル基、置換或いは無置換のアミノ基、シアノ基からそれぞれ独立に選ばれる。Ｒ ₃₉₁ 乃至Ｒ ₃₉₆ のうちの隣接する２つは、互いに結合して環を形成してもよい。
Ｚ ₁ はハロゲン原子、シアノ基、置換或いは無置換のヘテロアリール基又は以下の一般式［１－１］乃至［１－９］で表される置換基のいずれかを表す。

（一般式［１－１］乃至［１－９］において、Ｒ ₅₂₁ 乃至Ｒ ₅₈₈ は水素原子、ハロゲン原子、置換或いは無置換のアルキル基、置換或いは無置換のアルコキシ基、置換或いは無置換のアリール基、置換或いは無置換の複素環基、置換或いは無置換のビニル基、置換或いは無置換のアミノ基、シアノ基からそれぞれ独立に選ばれる。＊は炭素原子との結合位置を表す。））

（一般式［２］において、
Ｒ ₂₀ 乃至Ｒ ₂₉ は水素原子、ハロゲン原子、置換或いは無置換のアルキル基、置換或いは無置換のアルコキシ基、置換或いは無置換のアリール基、置換或いは無置換の複素環基、置換或いは無置換のビニル基、置換或いは無置換のアミノ基、シアノ基からそれぞれ独立に選ばれる。Ｒ ₂₀ 乃至Ｒ ₂₉ のうちの隣り合う２つは互いに結合して環を形成してもよい。）

（一般式［３］乃至［５］において、
Ｍは金属原子であり、前記金属原子は酸素原子又はハロゲン原子を置換基として有してもよい。
Ｌ ₁ 乃至Ｌ ₉ は金属Ｍに配位する配位子であって、置換或いは無置換のアリール基、置換或いは無置換の複素環基からなり、それぞれＬ ₁ 乃至Ｌ ₉ のうちの隣り合う２つは互いに結合して環を形成してもよい配位子を表す。）
本発明の第二は、光電変換素子を備えた複数の画素を有し、前記複数の画素が二次元に配置されている光エリアセンサであって、
前記光電変換素子は本発明第一の光電変換素子であることを特徴とする。
本発明の第三は、光電変換素子と前記光電変換素子に接続されている読み出し回路とを備えた複数の画素、及び、前記画素に接続されている信号処理回路、を有する撮像素子であって、
前記光電変換素子は本発明第一の光電変換素子であることを特徴とする。
本発明の第四は、複数のレンズを有する撮像光学部と、前記撮像光学部を通過した光を受光する撮像素子とを有し、前記撮像素子が本発明第三の撮像素子であることを特徴とする撮像装置である。 The first of the present invention has at least an anode, a photoelectric conversion layer, and a cathode in this order, and the photoelectric conversion layer has at least the first organic semiconductor, the second organic semiconductor, and the third organic semiconductor. In the photoelectric conversion element consisting of
The first organic semiconductor, the second organic semiconductor, and the third organic semiconductor are all low molecular weight organic semiconductors.
The first organic semiconductor is an n-type semiconductor, the second organic semiconductor is a p-type semiconductor, and the like.
The mass ratio of the first organic semiconductor, the second organic semiconductor, and the third organic semiconductor is
The first organic semiconductor ≧ the second organic semiconductor ≧ the third organic semiconductor,
When the total of the first organic semiconductor, the second organic semiconductor and the third organic semiconductor is 100% by mass, the content of the second organic semiconductor is 6% by mass or more, and the third organic The content of the semiconductor is 3% by mass or more,
The second organic semiconductor and the third organic semiconductor are selected from the compounds represented by the following general formulas [2] to [5] and the compounds represented by the following general formula [28], respectively. At least one of the organic semiconductor and the third organic semiconductor is a compound represented by the following general formula [28].
A photoelectric conversion element having a photoelectric conversion layer having the first organic semiconductor and the second organic semiconductor, and a photoelectric conversion layer having the first organic semiconductor and the third organic semiconductor. When the conversion element and the two photoelectric conversion elements are configured, the peak wavelengths in the spectral sensitivity spectrum of the external quantum efficiency with respect to the incident light of the two photoelectric conversion elements are the same, or the following equations (1) and (2) are used. It is a photoelectric conversion element characterized by satisfying.
η ₁ > η ₂ ... (1)
| ΔEg | ≤0.052 eV ... (2)
(Η ₁ : Conversion efficiency represented by the external quantum efficiency / absorption rate of the photoelectric conversion layer of the photoelectric conversion element having the peak on the short wavelength side of the two photoelectric conversion elements η ₂ : Of the two photoelectric conversion elements Of these, the conversion efficiency ΔEg of the photoelectric conversion element having the peak on the long wavelength side: the energy difference determined by the difference in the wavelengths of the peaks of the two photoelectric conversion elements).

(In the general formula [28],
R ₁ is a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted vinyl group, Represents a substituted or unsubstituted amino group or cyano group.
R ₃₉₁ to R ₃₉₆ are hydrogen atom, halogen atom, substituted or unsubstituted alkyl group, substituted or unsubstituted alkoxy group, substituted or unsubstituted aryl group, substituted or unsubstituted heterocyclic group, substituted or unsubstituted. It is independently selected from a vinyl group, a substituted or unsubstituted amino group, and a cyano group. Adjacent two of R ₃₉₁ to R ₃₉₆ may be combined with each other to form a ring.
Z ₁ represents either a halogen atom, a cyano group, a substituted or unsubstituted heteroaryl group or a substituent represented by the following general formulas [1-1] to [1-9].

(In the general formulas [1-1] to [1-9], R ₅₂₁ to R ₅₈₈ are a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, and a substituted or unsubstituted aryl. It is independently selected from a group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted vinyl group, a substituted or unsubstituted amino group, and a cyano group. * Indicates a bond position with a carbon atom.))

(In the general formula [2]
R ₂₀ to R ₂₉ are hydrogen atom, halogen atom, substituted or unsubstituted alkyl group, substituted or unsubstituted alkoxy group, substituted or unsubstituted aryl group, substituted or unsubstituted heterocyclic group, substituted or unsubstituted. It is independently selected from a vinyl group, a substituted or unsubstituted amino group, and a cyano group. Two adjacent two of R ₂₀ to R ₂₉ may be combined with each other to form a ring. )

(In the general formulas [3] to [5],
M is a metal atom, and the metal atom may have an oxygen atom or a halogen atom as a substituent.
L ₁ to L ₉ are ligands coordinated to the metal M and consist of a substituted or unsubstituted aryl group and a substituted or unsubstituted heterocyclic group , which are adjacent 2 of L ₁ to L ₉ , respectively. Represents a ligand that may be bonded to each other to form a ring. )
The second aspect of the present invention is an optical area sensor having a plurality of pixels including a photoelectric conversion element, and the plurality of pixels are arranged two-dimensionally.
The photoelectric conversion element is the first photoelectric conversion element of the present invention.
A third aspect of the present invention is an image pickup device having a plurality of pixels including a photoelectric conversion element and a readout circuit connected to the photoelectric conversion element, and a signal processing circuit connected to the pixels. ,
The photoelectric conversion element is the first photoelectric conversion element of the present invention.
The fourth aspect of the present invention is to have an image pickup optical unit having a plurality of lenses and an image pickup element that receives light that has passed through the image pickup optical unit, and the image pickup element is the third image pickup element of the present invention. It is a characteristic image sensor .

According to the present invention, by forming the photoelectric conversion layer with three types of small molecule organic semiconductors, a photoelectric conversion element capable of photoelectric conversion with low dark current and high sensitivity is provided.

It is a schematic diagram which shows the generation mechanism of dark current in a photoelectric conversion layer. It is a schematic diagram for demonstrating the effect of the 3rd organic semiconductor which concerns on this invention. It is a schematic diagram of the mixed film of the first organic semiconductor and the second organic semiconductor which approximated a rectangular parallelepiped. It is a conceptual diagram showing the relationship between a ternary element and a configurable binary element. It is sectional drawing of one Embodiment of the photoelectric conversion element of this invention. FIG. 5 is an equivalent circuit diagram of an example of a pixel including the photoelectric conversion element shown in FIG. It is a top view schematically showing the structure of the photoelectric conversion apparatus using the photoelectric conversion element of this invention. It is a figure which plotted the increase rate of the conversion efficiency of the photoelectric conversion element of an Example with respect to ΔEg. It is a figure which showed the Arrhenius plot of the dark current value of the photoelectric conversion element of the Example of this invention.

The present invention will be described in detail with reference to the drawings as appropriate, but the present invention is not limited to the embodiments described below.

The photoelectric conversion element of the present invention relates to a dark current reduction of a photoelectric conversion element provided with a photoelectric conversion layer made of an organic compound between an anode and a cathode. In the present invention, as the organic compound constituting the photoelectric conversion layer, a p-type organic semiconductor and an n-type organic semiconductor are used in combination, and a third organic semiconductor is added to reduce dark current and sensitivity. It is characterized by improving. In the present invention, the p-type organic semiconductor, the n-type organic semiconductor, and the third organic semiconductor constituting the photoelectric conversion layer are all low molecular weight organic semiconductors.

In the present specification, the terms "dual element" and "ternary element" may be used. The "dual element" is a photoelectric mixed film having a dual structure of a kind of p-type semiconductor and a kind of n-type semiconductor selected from a first organic semiconductor, a second organic semiconductor and a third organic semiconductor. It is a photoelectric conversion element used as a conversion layer. Further, the "ternary element" is a photoelectric conversion element having a mixed film having a ternary structure of a first organic semiconductor, a second organic semiconductor and a third organic compound as a photoelectric conversion layer.

(Photoelectric conversion layer)
First, the photoelectric conversion layer, which is a feature of the present invention, will be described.
By absorbing light, the photoelectric conversion layer generates an electric charge according to the amount of light. The photoelectric conversion layer according to the present invention contains at least a first organic semiconductor, a second organic semiconductor, and a third organic semiconductor, and all of these organic semiconductors are low molecular weight organic semiconductors. Further, one of the first organic semiconductor and the second organic semiconductor is a p-type organic semiconductor (hereinafter referred to as "p-type semiconductor"), and the other is an n-type organic semiconductor (hereinafter referred to as "n-type semiconductor"). It is written as). Specifically, of the first organic semiconductor and the second organic semiconductor, the one having the smaller oxidation potential is the p-type semiconductor. External quantum efficiency (sensitivity) can be improved by mixing a p-type semiconductor and an n-type semiconductor in the photoelectric conversion layer.

In the present invention, the mass ratio of the first organic semiconductor, the second organic semiconductor, and the third organic semiconductor is the first organic semiconductor ≧ the second organic semiconductor ≧ the third organic semiconductor.
When the content (mass%) in the photoelectric conversion layer is the same in the first organic semiconductor, the second organic semiconductor, and the third organic semiconductor, the organic semiconductors having the largest molecular weights are listed first, second, and so on. Third. That is, when the three types of organic semiconductors are contained in equal mass, the organic semiconductor having the largest molecular weight is the first organic semiconductor, and the organic semiconductor having the smallest molecular weight is the third organic semiconductor. When the content of two types of organic semiconductors is the same and the content of the remaining one type is higher than that of the previous two types, the one having the larger molecular weight is the first of the above two types of organic semiconductors. The second organic semiconductor, the smaller one is the third organic semiconductor. When the content of two types of organic semiconductors is the same and the content of the remaining one type is smaller than that of the previous two types, the one having the larger molecular weight is the first of the above two types of organic semiconductors. One organic semiconductor, the smaller one is the second organic semiconductor.

Further, the photoelectric conversion layer of the present invention may be composed of at least the first organic semiconductor, the second organic semiconductor and the third organic semiconductor, but the photoelectric conversion function and the dark current reduction which is an effect of the present invention are effective. Materials other than these may be contained as long as the effect is not impaired. The content of the other material may be less than or equal to the content of the third organic semiconductor. When the content of the other material and the content of the third organic semiconductor are equal, the one having the larger molecular weight is the third organic semiconductor.

The third organic semiconductor of the present invention is added in order to suppress the dark current generated when the photoelectric conversion layer is composed of only the first organic semiconductor and the second organic semiconductor. When the second organic semiconductor is a p-type semiconductor, it is preferable that the third organic semiconductor is also a p-type semiconductor. Similarly, when the second organic semiconductor is an n-type semiconductor, the third organic semiconductor is also It is preferably an n-type semiconductor. Of the first organic semiconductor and the second organic semiconductor, the one having a smaller oxidation potential is a p-type semiconductor, and the one having a larger oxidation potential is an n-type semiconductor. When the oxidation potential of the third organic semiconductor is close to the oxidation potential of the compound which is a p-type semiconductor among the first organic semiconductor and the second organic semiconductor, the third organic semiconductor is a p-type semiconductor. Similarly, when the oxidation potential of the third organic semiconductor is close to the oxidation potential of the compound which is an n-type semiconductor among the first organic semiconductor and the second organic semiconductor, the third organic semiconductor is an n-type semiconductor. be. As a result, the photoelectric conversion function of the second organic semiconductor having a smaller content in the photoelectric conversion layer than that of the first organic semiconductor (electron donor function if the second organic semiconductor is a p-type semiconductor, electron if the second organic semiconductor is an n-type semiconductor). The acceptor function) can be supplemented by a third organic semiconductor.

The wavelength at which the absorption rate of the thin film of the third organic semiconductor in the visible light region (wavelength 400 nm to 730 nm) is maximum is the absorption rate of the first organic semiconductor and the second organic semiconductor in the visible light region, respectively. It is preferably a wavelength between the two maximum wavelengths. Thereby, the absorption in the wavelength region between the absorption band of the first organic semiconductor and the second organic semiconductor can be efficiently supplemented by the third organic semiconductor.

Further, when the total amount of the first organic semiconductor, the second organic semiconductor and the third organic semiconductor is 100% by mass, the content of the second organic semiconductor is 6% by mass or more, and the third organic The content of the semiconductor is 3% by mass or more. The present inventors have found that a photoelectric conversion element exhibiting good characteristics can be produced by setting the composition of the organic semiconductor in such a relationship. Details will be described below.

The bulk heterostructured photoelectric conversion layer formed by mixing a conventional p-type semiconductor and n-type semiconductor has a higher content (mass%) in the photoelectric conversion layer than a first organic semiconductor and a second less. It is a dual configuration that uses two types of organic semiconductors in combination. In such a photoelectric conversion layer, a panchromatic absorption can be obtained by complementing each other's absorption wavelength regions with the first organic semiconductor and the second organic semiconductor. In such a configuration, the higher the content of the second organic semiconductor in the photoelectric conversion layer, the more sufficient panchromatic absorption can be realized.

However, the present inventors have found that as the content of the second organic semiconductor increases, the dark current when a voltage is applied to the photoelectric conversion element increases. The reason will be explained below with reference to the drawings.
FIG. 1 is a schematic diagram showing a basic dark current generation mechanism in a photoelectric conversion layer, and is a HOMO (highest occupied molecular orbital) level and LUMO (lowest empty orbital) in a single molecule of a p-type semiconductor and an n-type semiconductor. ) The relationship of levels is illustrated. It is considered that the electrons existing in the HOMO level of the p-type semiconductor shown in FIG. 1 move to the LUMO level of the n-type semiconductor by thermal energy, causing charge separation and generating a dark current. The energy barrier of electron transfer at that time is ΔE ₁ .
However, in the mixed film of the first organic semiconductor and the second organic semiconductor, the same compounds associate with each other to form a dimer, for example, and the interaction due to stacking between the same molecules is strengthened. As a result, the density of states of the HOMO level and the LUMO level form an energetic spread.

FIG. 2 is a schematic diagram for explaining the effect of the third organic semiconductor according to the present invention. The solid line in FIG. 2 is a mixed film having a dual structure of the first organic semiconductor and the second organic semiconductor when the first organic semiconductor is an n-type semiconductor and the second organic semiconductor is a p-type semiconductor. , The energy distribution of the state densities of the HOMO level and the LUMO level is schematically shown. In this case, the energy barrier ΔE ₂ of electron transfer considering the energy spread of the density of states is smaller than ΔE ₁ when considered in terms of the energy level of a single molecule. Further, the wider the energetic spread of the density of states, the smaller ΔE ₂ and the easier it is for dark current to occur. It is considered that the higher the content of the second organic semiconductor in the photoelectric conversion layer, the easier it is for the second organic semiconductors to associate with each other, and the energetic spread of the density of states of the HOMO level and the LUMO level also tends to spread. it is conceivable that. Therefore, it is considered that the dark current increases as the content of the second organic semiconductor increases. In addition, the second organic semiconductor, which has a lower content in the photoelectric conversion layer than the first organic semiconductor, has an energetic spread of the density of states of the HOMO level and the LUMO level, depending on the content. It is expected to change.

The phenomenon of forming the energetic spread of the density of states of the HOMO level and the LUMO level due to the association between the second organic semiconductors described above is that the content of the second organic semiconductor is the first and second organic. It is known to occur when the total amount of semiconductors is 6% by mass or more. In Non-Patent Document 1, in a mixed film of two kinds of organic compounds, molecules of low-concentration organic compounds associate with each other at 6% by mass or more, so that the emission of the organic compound has a long wavelength and tends to be quenched. Is stated to begin to appear. It is considered that the longer wavelength of the light emission is due to the larger energetic spread of the density of states of the HOMO level and the LUMO level and the smaller effective bandgap.

As a countermeasure against the increase in dark current as the content of the second organic semiconductor increases, the present inventors have discovered the following as a result of diligent studies. Even when the content of the second organic semiconductor is 6% by mass or more, only the first organic semiconductor and the second organic semiconductor are mixed by mixing the third organic semiconductor so as to be 3% by mass or more. This means that the dark current can be reduced as compared with the case of mixing. In the present invention, the content of the second organic semiconductor is 6% by mass or more and the content of the third organic semiconductor is 3% by mass or more, both of which are the first organic semiconductors. It is the content when the total amount of the second organic semiconductor and the third organic semiconductor is 100% by mass.

Hereinafter, the mechanism of the dark current reduction effect by mixing the third organic semiconductor considered by the present inventors will be described with reference to FIG.
The broken line in FIG. 2 indicates that the first organic semiconductor is an n-type semiconductor, the second organic semiconductor is a p-type semiconductor, and in addition, the third organic semiconductor is mixed in the mixed film having a ternary structure. It is a schematic representation of the energy distribution of the state densities of the HOMO level and the LUMO level. It can be seen that the energetic spread of the density of states is suppressed as compared with the solid line showing the distribution of the density of states of the mixed film having a dual structure consisting of only the first organic semiconductor and the second organic semiconductor. Specifically, when a third organic semiconductor is mixed in addition to the first organic semiconductor and the second organic semiconductor, the second organic semiconductors are associated with each other and the interaction due to stacking is suppressed. Can be done. As a result, the energetic spread of the density of states of each level can be suppressed. The association of organic compounds, the formation of dimers, and the interaction due to stacking are particularly likely to occur between the same compounds, so that when different compounds are mixed, they are inhibited. Further, the effect of suppressing the energetic spread of the density of states due to the mixing of the third organic semiconductor is also provided to the first organic semiconductor. However, the second organic semiconductor having a lower content than the first organic semiconductor is more likely to realize a highly dispersible state by mixing the third organic semiconductor so that the molecules do not meet with each other. Therefore, it is considered that it is easy to greatly suppress the energetic spread of the density of states of each level.

In FIG. 2, the case where the first organic semiconductor is an n-type semiconductor and the second organic semiconductor is a p-type semiconductor has been described as an example, but the first organic semiconductor is a p-type semiconductor and the second organic semiconductor is an n-type semiconductor. In the case of semiconductors as well, it is considered that the effect of mixing the third organic semiconductor is similarly exhibited. It was found that the effect of adding the third organic semiconductor can be obtained even when the contents of the first organic semiconductor and the second organic semiconductor are equal.

In the present invention, the total amount of the first, second and third organic semiconductors is 100% by mass, the content of the third organic semiconductor is 3% by mass or more, and the dark current is reduced by adding the third organic semiconductor. The effect is exhibited, but it is preferably 6% by mass or more, and particularly preferably 10% by mass or more. Further, the mass ratio of the third organic semiconductor to the second organic semiconductor is 0.12 or more, and the association of the second organic semiconductor can be effectively suppressed by the third organic semiconductor, which is preferable. The mass ratio is more preferably 0.24 or more, and particularly preferably 0.4 or more.

In the present invention, when the total amount of the first, second and third organic semiconductors is 100% by mass and the content of the second organic semiconductor is 6% by mass or more, the darkness due to the addition of the third organic semiconductor The effect of reducing the current is exhibited, but the effect becomes remarkable at 10% by mass or more, which is preferable. Patent Document 3 describes that when two compounds are mixed, the concentration of light emission is markedly quenched when the compound having the lower mixed concentration is 10% by mass or more. Therefore, also in the present invention, when the total amount of the first, second, and third organic semiconductors is 100% by mass, and the second organic semiconductor is 10% by mass or more, the second organic semiconductors are separated from each other. It is considered that the meeting will be remarkable, and the effect of adding the third organic semiconductor will be more remarkable. Further, by setting the content of the second organic semiconductor to 10% by mass or more, the absorption rate of light in the absorption band of the second organic semiconductor can be increased.

Further, in the present invention, when the total amount of the first, second and third organic semiconductors is 100% by mass, it is preferable that the second organic semiconductor is 17% by mass or more. When the content of the second organic semiconductor is 17% by mass or more, the probability that the second organic semiconductors come into contact with each other on the surface is particularly high. Therefore, more remarkable interaction due to stacking is likely to occur, and the dark current reduction effect when the third organic semiconductor is mixed becomes remarkable accordingly. The reason will be described with reference to FIG.

FIG. 3 is a schematic diagram of a mixed film having a dual structure of a first organic semiconductor and a second organic semiconductor, which is similar to a rectangular parallelepiped.
The three-dimensional shape of a low-molecular-weight organic compound is the difference between the maximum and minimum values of the X, Y, and Z coordinate axes when plotting the position of each atom forming the organic compound in three-dimensional coordinates. It can be approximated to a rectangular parallelepiped whose one side is. When a rectangular parallelepiped of the same size is filled in a three-dimensional space, as shown in FIG. 3, for each surface of a certain rectangular parallelepiped A, two in the X-axis direction, two in the Y-axis direction, and two in the Z-axis direction. A total of 6 rectangular parallelepipeds B are adjacent to each other on the surface. In FIG. 3, in addition to the rectangular parallelepiped A and its center of gravity, six rectangular parallelepipeds B adjacent to the rectangular parallelepiped A in a plane and their centers of gravity are shown. Here, the second organic semiconductor having a small content (% by mass) in the mixed film is applied to the rectangular parallelepiped A. When all six rectangular parallelepipeds B are the first organic semiconductors, the second organic semiconductors do not come into contact with each other on the surface. On the other hand, when the rectangular parallelepiped A is the second organic semiconductor and at least one of the six rectangular parallelepipeds B is the second organic semiconductor, the second organic semiconductors come into contact with each other in a plane. That is, in the mixed film of the first organic semiconductor and the second organic semiconductor, when the content of the second organic semiconductor is 1/6, that is, about 17% by mass or more, the second organic semiconductor in the mixed film. It can be seen that they can come into contact with each other on the surface and cause an interaction due to strong stacking.

When a small molecule organic compound is approximated to a rectangular parallelepiped, remarkable stacking interaction is likely to occur when it is in contact with a plane, but it is considered that stacking interaction is caused in a small degree when it is in contact with a side. Here, in addition to the six rectangular parallelepipeds that are in contact with the rectangular parallelepiped A on the surface, the number of rectangular parallelepipeds that are in contact with the sides is 12, which is a total of 18. That is, in order for the second organic semiconductors to come into contact with each other on a surface or a side, the content in the mixed film needs to be 1/18, that is, about 6% by mass or more, and at least 6% by mass or more. It was found that the dark current reduction effect by mixing the third organic semiconductor is exhibited. As a result, the above-mentioned phenomenon of forming an energetic spread of the density of states of the HOMO level and the LUMO level due to the association between the second organic semiconductors may occur when the content of the second organic semiconductor is 6% by mass or more. , Not only from the description in Non-Patent Document 1, but also from the geometrical consideration.

From the above, in the present invention, when the total amount of the first, second and third organic semiconductors is 100% by mass, the second organic semiconductor is 6% by mass or more, preferably 17% by mass or more. The dark current reduction effect of mixing the third organic semiconductor was supported by geometrical considerations.

As described above, in the present invention, the dark current reduction effect by adding the third organic semiconductor to the mixed film of the first organic semiconductor and the second organic semiconductor is the first, second, and first. When the total amount of the three organic semiconductors is 100% by mass, the second organic semiconductor is obtained in an amount of 6% by mass or more. Further, the dark current reducing effect is exhibited when the amount of the third organic semiconductor is 3% by mass or more, but the effect is obtained until the amount of the second organic semiconductor becomes the same as that of the first organic semiconductor, and further, the third organic semiconductor is obtained. The third organic semiconductor can be added until the amount becomes the same as that of the second organic semiconductor. Therefore, in the present invention, the mass ratio of the first organic semiconductor, the second organic semiconductor, and the third organic semiconductor is determined.
The first organic semiconductor ≧ the second organic semiconductor ≧ the third organic semiconductor.

In the present invention, it is also possible to improve S while lowering N of S / N by reducing the dark current. For that purpose, two organic semiconductors, a p-type semiconductor selected from a first organic semiconductor, a second organic semiconductor, and a third organic semiconductor, and an n-type semiconductor, each having different photoelectric conversion layers are provided. When the photoelectric conversion element is configured, the wavelengths of the peaks (EQE peaks) in the spectral sensitivity spectrum of the external quantum efficiency (EQE) with respect to the incident light of the two photoelectric conversion elements are equal, or the following equations (1) and (2) are satisfied. I found that it was effective.

η ₁ > η ₂ ... (1)
| ΔEg | ≤0.052 eV ... (2)
(Η ₁ : Conversion efficiency of the photoelectric conversion element having an EQE peak on the short wavelength side of the two photoelectric conversion elements η ₂ : Conversion efficiency of the photoelectric conversion element having an EQE peak on the long wavelength side of the two photoelectric conversion elements ΔEg : Energy difference determined by the difference in wavelength of the EQE peaks of the two photoelectric conversion elements)

Even if the absorption characteristics for incident light are excellent, if the charge separation ability is low, a photoelectric conversion element with good sensitivity cannot be obtained. Along with the absorption characteristics, the photon-to-electron conversion efficiency is also an important factor in determining the sensitivity of the photoelectric conversion element. Here, in the photoelectric conversion element, the conversion efficiency (η) is defined as the probability of converting the absorbed photons into electrons as follows.
Conversion efficiency (η) = Absorption rate of EQE / photoelectric conversion layer ... (3)

Here, EQE (Quantum Quantum Efficiency) is also called quantum efficiency (Quantum Efficiency), and is the efficiency at which the total number of photons incident on the photoelectric conversion element is converted into an electric signal. A high EQE means that the sensitivity as a photoelectric conversion element is high. EQE is applied to a photoelectric conversion element applied with a predetermined voltage, for example, light from an A light source or an Xe light source is incident on the element with or without spectroscopy, and the number of electrons calculated by measuring the current value is applied to the element. It is a value obtained by dividing by the total number of incident photons. At this time, by dispersing the incident light and measuring the EQE of each wavelength, the spectral sensitivity spectrum of the EQE is obtained, and the peak (EQE peak) is observed.

The absorption rate of the photoelectric conversion layer is the ratio of light absorption by the photoelectric conversion layer to the total number of photons incident on the photoelectric conversion element. Therefore, the conversion efficiency (η) is the rate at which photons absorbed in the photoelectric conversion layer are converted into electrons.
The conversion efficiency (η) can be obtained, for example, as follows. Absorption rate measurement is possible by forming a transparent pixel portion of an organic photoelectric conversion element on a transparent substrate by using a transparent electrode such as IZO for both the anode and the cathode. As a measuring device, "Solidspec 3700" manufactured by Shimadzu Corporation can be used. Alternatively, as another method, it may be obtained from the extinction coefficient (k) obtained by analyzing the optical characteristics with spectroscopic ellipso or the like and the film thickness of the prepared photoelectric conversion layer. The photoelectric conversion current can be obtained by subtracting the dark current from the light current flowing during the light irradiation of the photoelectric conversion element, and the EQE can be obtained by converting it into the number of electrons and dividing by the number of irradiation photons. Then, as described above, the conversion efficiency (η) can be obtained from the EQE and the absorption rate of the photoelectric conversion layer.

The photoelectric conversion layer in the present invention has first, second, and third organic semiconductors, and the combination as these organic semiconductors is the case where two types of p-type semiconductors and one type of n-type semiconductors are used, and two. This is a case where a kind of n-type semiconductor and a kind of p-type semiconductor are used. Therefore, there are two combinations selected one by one from the p-type semiconductor and the n-type semiconductor. That is, when two types of p-type semiconductors and one type of n-type semiconductors are used as the first, second, and third organic semiconductors, two types of photoelectric conversion layers having different p-types are used. When the n-type semiconductor and a kind of p-type semiconductor are used, two kinds of photoelectric conversion layers having different n-types can be considered. A photoelectric conversion element provided with a photoelectric conversion layer that can be configured by two combinations selected from the first, second, and third organic semiconductors has a spectral sensitivity characteristic consisting of each absorption wavelength band and conversion efficiency. become.

Here, each configuration and its parameters are defined as follows, and the relationship between the ternary element and the configurable binary element will be described with reference to FIG.
Dual element 1: Photoelectric with a dual configuration that has an EQE peak wavelength on the short wavelength side and combines one of each of a p-type semiconductor and an n-type semiconductor selected from the first, second, and third organic semiconductors. Photoelectric conversion element with conversion layer Dual element 2: One of each of a p-type semiconductor and an n-type semiconductor that has an EQE peak wavelength on the long wavelength side and is selected from the first, second, and third organic semiconductors. Photoelectric conversion element having a combined dual-structured photoelectric conversion layer Tertiary element: A photoelectric conversion element having a ternary-structured photoelectric conversion layer in which first, second, and third organic semiconductors are combined.

The EQE peak wavelength is the sensitivity peak wavelength on the longest wavelength side of a photoelectric conversion element having a photoelectric conversion layer that can be composed of one p-type and one n-type organic semiconductor in the visible region. In essence, this EQE peak wavelength corresponds to the absorption peak wavelength of the organic semiconductor that causes absorption. That is, when the EQE peak wavelength is provided on the longest wavelength side, the first, second, or third organic semiconductor has the corresponding absorption peak wavelength. As shown in FIG. 4A, the EQE peak wavelength of the binary element 1 is λ ₁ (nm), and the conversion efficiency of the element is η ₁ . Further, the EQE peak wavelength of the dual element 2 is λ ₂ (nm), and the conversion efficiency of the element is η ₂ . Similarly, the conversion efficiency of the ternary element is η ₃ .
Here, ΔEg is defined as follows.
ΔEg = 1.24 × 10 ^-4 (10 ⁷ / λ ₁ -10 ⁷ / λ ₂ ) [Unit: eV] ... (4)

Since the spectral characteristics of the EQE and the absorption characteristics correspond to each other, the photoelectric conversion element made of an organic semiconductor having a smaller bandgap has the absorption peak wavelength on the long wavelength side, and the corresponding EQE peak wavelength is also on the long wavelength side. When the EQE peak wavelength is unclear, it can be determined by manufacturing a photoelectric conversion element in which the content of the organic semiconductor is adjusted so that the absorption rate is high. If the EQE peak wavelength cannot be confirmed at any content, the bending point at which the EQE value turns upward when viewed from the long wavelength side to the short wavelength side is used as an index as the spectral characteristic of EQE, and the bending point is used as the EQE. It can be considered as an alternative to the peak wavelength. This corresponds to the bandgap of any of the constituent organic semiconductor compounds. In that case, it is necessary to calculate both the binary element 1 and the binary element 2 at the bending points. If it is difficult to discriminate between the peak wavelength and the bending point from the spectral characteristics of the EQE, the absorption peak wavelength in the 100% film of the organic semiconductor or the band gap may be applied as equivalent thereto.

The absorption peak wavelength and band gap of the organic semiconductor can be used as an index representing the absorption band of the organic semiconductor. It is possible to obtain the absorption peak wavelength and the optical absorption edge by producing a thin film made of a single material of about 100 nm or less by vacuum deposition or spin coating method and measuring the absorption spectrum of the thin film. The absorption peak wavelength here refers to the peak on the longest wavelength side of the absorption band, and is the peak wavelength of the first absorption band. As for the absorption peak wavelength in the absorption band, for example, a single peak indicates the peak, and a multiple peak (also referred to as an oscillating structure) indicates the highest intensity peak. On the other hand, the optical absorption end corresponds to the band gap.

An energy transfer process occurs between the first, second, and third organic semiconductors in the photoelectric conversion layer until charge separation occurs from the organic semiconductor that has been excited by absorbing light. Excitation energy transfer is a high-speed phenomenon mainly called Förster type (fluorescence resonance) energy transfer. Basically, it occurs when there is an overlap between the emission spectrum of an organic semiconductor that has absorbed light and the absorption spectrum of another organic semiconductor that receives the energy, and the larger the overlap, the easier it is for energy to move. That is, the excitation energy moves from the light-absorbed organic semiconductor toward the organic semiconductor having an absorption band on the longer wavelength side. In particular, it is preferable that the organic semiconductor serving as the energy receptor has a high absorption probability, that is, it is important that the molar extinction coefficient is large. This energy transfer process is a very high-speed phenomenon as well as the electron transfer process.

The excitation energy of the photoexcited organic semiconductor moves toward the organic semiconductor having a small bandgap. Therefore, when the η 2 of the binary element ₂ is low, the η ₃ of the ternary element is also low. This can be said to be the result of η ₂ = η ₃ . However, the present inventors have found that η ₃ > η ₂ when the EQE peak wavelength satisfies a specific relationship. The mechanism will be described below.

As shown in FIG. 4A, the conversion efficiency (η ₁ ) of the dual element 1 of the combination of pn having the EQE peak wavelength on the relatively short wavelength side has the EQE peak wavelength on the relatively long wavelength side. The following relationship may be satisfied as the conversion efficiency (η ₂ ) of the dual element 2 of the combination.
η ₁ > η ₂ ... (1)
ΔEg ≤ 0.052 eV ... (2)
ΔEg is an energy difference obtained from the EQE peak wavelength difference of a dual element provided with a photoelectric conversion layer that can be composed of one p-type and one n-type organic semiconductor among the first, second, and third organic semiconductors. .. By satisfying the above relationship, energy can be exchanged between combinations of pn having different conversion efficiencies. Specifically, by making it possible to partially transfer energy from the combination of pn of the dual element 2 to the combination of pn of the dual element 1, the charge separation ability of the dual element 1 having high conversion efficiency is achieved. Can be utilized. As a result, a certain improvement in conversion efficiency can be expected, and it becomes possible to create a relationship of η ₁ > η ₃ > η ₂ as shown in FIG. 4 (B).

It is considered that the energy can be exchanged because the energy can be exchanged thermally due to the coupling factor of the molecular vibration. Molecules vibrate in the membrane, which is also a factor in the broad absorption band peculiar to organic materials. Vibration coupling is likely to occur between molecules with overlapping absorption bands. However, the larger the overlap of the absorption bands, the better, which leads to the fact that the peak wavelengths are close to each other, and as a result, the relationship as described in the above equation (2) becomes important. It is considered that Förster-type energy transfer is promoted through this vibration.
When ΔEg is larger than 0.052 eV, it is considered that the energy is transferred to the p or n-type semiconductor of the combination of the dual elements 2 and easily localized. This is because the coupling of molecular vibrations is weakened.

The combinations constituting the photoelectric conversion layer are as follows: a) The first organic semiconductor is n-type, and the second and third organic semiconductors are p-type.
b) The first organic semiconductor is p-type, the second and third organic semiconductors are n-type,
Is mainly considered. At that time, what is particularly important is the absorption characteristics between p-type semiconductors in a) and the absorption characteristics between n-type semiconductors in b). By considering the above, the sensitivity of the photoelectric conversion element having a ternary configuration is improved over the entire wavelength range having absorption, and the S / N ratio is further improved. The lower limit of ΔEg in the equation (2) is 0 eV, which is the case where the EQE peaks of the binary element 1 and the binary element 2 are the same.

On the other hand, the time in which the energy is bidirectional depends on the exciton lifetime of the organic semiconductor. At that time, it is preferable that the band gap is small, that is, the excited state lifetime of the organic semiconductor having a sensitivity peak on the long wavelength side is long. As a result, the probability that excitons accumulated in the lower energy level of the photoexcited state will be absorbed into an organic semiconductor with a slightly higher energy level and high conversion efficiency and charge separation will increase, and the conversion efficiency will increase. be. Specifically, the exciton lifetime is preferably 1 ns or more, and particularly preferably 3 ns or more.
It is preferable that η ₁ is at least 1% or more higher than η ₂ , and more preferably 5% or more, the effect tends to be remarkable.

On the other hand, since each content of the p-type −n type organic semiconductor having high conversion efficiency needs to function as an energy receptor, the content of the second organic semiconductor is preferably 6% by mass or more. Therefore, it is preferable that the combination having the higher conversion efficiency is the first and second organic semiconductors.
As a receptor for energy transfer, the molar extinction coefficient of the first absorption band of the organic semiconductor is at least 1000 molL ^-1 cm ^-1 , and more preferably 10,000 molL ^-1 cm ^-1 or more. For example, the first absorption band of the organic semiconductor group exemplified as the p-type organic semiconductor material is in the visible light region, and its molar extinction coefficient is at least 1000 molL ^-1 cm ^-1 or more. On the other hand, although fullerene C60 and the like have an absorption band in the visible region, their molar absorption coefficient is less than 1000 molL ^-1 cm ^-1 , and they do not function effectively as energy receptors.

The first, second, and third organic semiconductors in the present invention are all small molecule organic compounds. Organic compounds are roughly classified into small molecules, oligomer molecules, and polymers depending on the molecule. Polymers and oligomer molecules are defined by the International Union of Pure and Applied Chemicals (IUPAC) Polymer Naming Method Committee as follows.
Polymer, polymer molecule (macromolecule, polymer molecule): A molecule with a large molecular mass, which has a structure composed of a large number of repetitions of a unit obtained substantially or conceptually from a molecule having a small relative molecular mass. ..
Oligomer molecule: A molecule with a medium-sized relative molecular mass that has a structure composed of a small number of repetitions of units substantially or conceptually obtained from a molecule with a small relative molecular mass. To say.

The first, second, and third organic semiconductors in the present invention are molecules that do not meet the above definitions of polymer, polymer molecule, and oligomer molecule. That is, it is a molecule having 3 or less, preferably 1 in which the number of repetitions of the repeating unit is a small number or less.
For example, fullerene, which will be described later, is a closed-shell hollow compound, but one closed-shell structure is regarded as one repeating unit. For example, fullerene C60 is a small molecule because the number of repetitions is one.
In addition, there are two types of macromolecules: synthetic macromolecules obtained by chemical synthesis and natural macromolecules that exist in nature. A polymer having a monodisperse in molecular weight exists in a natural polymer, but a synthetic polymer generally has a dispersibility in molecular weight due to a difference in repeating units. On the other hand, the organic semiconductor used in the present invention does not exist naturally and is a molecule obtained by synthesis, but it does not have the dispersibility of the molecular weight due to the difference in the repeating unit.

The presence or absence of such dispersibility makes an important difference when used for the photoelectric conversion layer in the photoelectric conversion element. When a dispersible polymer compound is used for the photoelectric conversion layer, the energy spread of the HOMO level and LUMO level of the compound contained in the photoelectric conversion layer becomes large, and the HOMO level of the p-type semiconductor becomes large. The energy barrier between the LUMO levels of the n-type semiconductor becomes uncontrollable. As a result, a level that generates a dark current when an electric field is applied is formed. Therefore, in the present invention, the photoelectric conversion layer does not have dispersibility due to the difference in the repeating unit, is a low molecular weight organic semiconductor having a repeating unit of 3 or less, preferably 1 and more preferably a molecular weight of 1500 or less having sublimation property. Low molecular weight organic semiconductor is used.

In the present invention, the first organic semiconductor may be an n-type semiconductor or a p-type semiconductor, but when fullerene or a derivative thereof, which is an n-type semiconductor, is used as the first organic semiconductor, the heat resistance is easily stabilized and it is handled. Is preferable because it is easy to use.

(P-type semiconductor)
The p-type semiconductor used in the present invention is an electron donor organic semiconductor, which is mainly represented by a hole transporting organic compound and has a property of easily donating electrons. The p-type semiconductor preferably has an absorption wavelength in the visible region of 450 nm to 700 nm in order to obtain a panchromatic absorption band. In particular, in order to obtain a panchromatic absorption band, it is preferably at 500 nm to 650 nm. As a result, in addition to the green region, the sensitivity of the blue region around 450 nm to 470 nm and the red region around 600 nm to 630 nm can be improved together, and the panchromaticity is improved.

The p-type semiconductor is preferably any of the compounds represented by the following general formulas [1] to [5], quinacridone derivatives, and 3H-phenoxazine-3-one derivatives. In the present specification, "forming a ring" does not limit the ring structure to be formed unless otherwise specified. For example, the 5-membered ring may be condensed, the 6-membered ring may be condensed, or the 7-membered ring may be condensed. The ring structure to be condensed may be an aromatic ring or an alicyclic ring structure.

General formula [1]

In the general formula [1], R ₁ is a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocyclic group, a substituent. Alternatively, it represents an unsubstituted vinyl group, a substituted or unsubstituted amino group, or a cyano group.
n ₁ , n ₂ , and n ₃ independently represent integers from 0 to 4, preferably 0 to 3, respectively.
X ₁ to X ₃ represent any of a nitrogen atom, a sulfur atom, an oxygen atom, and a carbon atom which may have a substituent.
Ar ₁ and Ar ₂ are independently selected from a substituted or unsubstituted arylene group or a substituted or unsubstituted divalent heterocyclic group, respectively. When there are a plurality of Ar ₁ and Ar ₂ , they may be the same or different, and when X ₂ or X ₃ is a carbon atom, Ar ₁ and Ar ₂ may be bonded to each other to form a ring.
Z ₁ represents either a halogen atom, a cyano group, a substituted or unsubstituted heteroaryl group or a substituent represented by the following general formulas [1-1] to [1-9].

In the general formulas [1-1] to [1-9], R ₅₂₁ to R ₅₈₈ are a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, and a substituted or unsubstituted aryl group. , A substituted or unsubstituted heterocyclic group, a substituted or unsubstituted vinyl group, a substituted or unsubstituted amino group, and a cyano group are independently selected. * Represents the bond position with the carbon atom.

General formula [2]

In the general formula [2], R ₂₀ to R ₂₉ are a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocycle. It is independently selected from a group, a substituted or unsubstituted vinyl group, a substituted or unsubstituted amino group, and a cyano group. Two adjacent two of R ₂₀ to R ₂₉ may be combined with each other to form a ring.

General formulas [3] to [5]

In the general formulas [3] to [5], M is a metal atom, and the metal atom may have an oxygen atom or a halogen atom as a substituent.

L ₁ to L ₉ are ligands coordinated to the metal M and consist of a substituted or unsubstituted aryl group and a substituted or unsubstituted heterocyclic group, which are adjacent 2 of L ₁ to L ₉ , respectively. Represents a ligand that may be bonded to each other to form a ring.

Among the organic compounds represented by the general formula [1], Ar ₁ is preferably a substituted or unsubstituted aryl group or a substituted or unsubstituted heterocyclic group. The complex atom of the heterocyclic group is preferably nitrogen. X ₁ is preferably a sulfur or oxygen atom. It is preferred that n ₁ is 1, _{n 2} is 0, and Ar ₂ is 0 and represents a single bond.

The general formula [2] can be more specifically expressed by any of the following general formulas [11] to [27].

In the general formulas [11] to [27], R ₃₁ to R ₃₉₀ are a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryl group, a substituted or no substituted group. It is independently selected from a substituted heterocyclic group, a substituted or unsubstituted vinyl group, a substituted or unsubstituted amino group, and a cyano group.

Specific examples of the substituents of the general formulas [1] and [2], the general formulas [1-1] to [1-9], and the general formulas [11] to [27] are shown below.
Examples of the halogen atom include a chlorine atom, a bromine atom and an iodine atom, and a fluorine atom is preferable.

The alkyl group is preferably an alkyl group having 1 to 10 carbon atoms. For example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a tert-butyl group, a sec-butyl group, an octyl group, a 1-adamantyl group, a 2-adamantyl group and the like can be mentioned. The alkyl group may be an alkyl group having 1 to 4 carbon atoms.

The alkoxy group is preferably an alkoxy group having 1 to 10 carbon atoms. For example, a methoxy group, an ethoxy group, an n-propioxy group, an isopropioxy group, an n-butoxy group, a tert-butoxy group, a sec-butoxy group, an octoxy group and the like can be mentioned. The alkoxy group may be an alkoxy group having 1 to 4 carbon atoms.

The aryl group is preferably an aryl group having 6 to 20 carbon atoms. For example, a phenyl group, a naphthyl group, an indenyl group, a biphenyl group, a terphenyl group, a fluorenyl group, an anthrasenyl group, a pyrenyl group, a fluoranthenyl group, a peryleneyl group and the like can be mentioned. In particular, a phenyl group, a biphenyl group, a terphenyl group, a fluorenyl group, and a naphthyl group have a low molecular weight and are preferable in consideration of the sublimation property of the compound.

The heterocyclic group is preferably a heterocyclic group having 3 to 15 carbon atoms. For example, pyridyl group, pyrazil group, triazil group, thienyl group, furanyl group, pyrrolyl group, oxazolyl group, oxadiazolyl group, thiazolyl group, thiadiazolyl group, carbazolyl group, acridinyl group, phenanthrolyl group, benzothiophenyl group, dibenzothiophenyl group. , Benzothiazolyl group, benzoazolyl group, benzopyrrolyl group and the like. Nitrogen is preferable as the complex atom contained in the heterocyclic group.

The amino group is preferably an amino group having an alkyl group or an aryl group as a substituent. For example, N-methylamino group, N-ethylamino group, N, N-dimethylamino group, N, N-diethylamino group, N-methyl-N-ethylamino group, N-benzylamino group, N-methyl-N. -Benzylamino group, N, N-dibenzylamino group, anilino group, N, N-diphenylamino group, N, N-dinaphthylamino group, N, N-difluorenylamino group, N-phenyl-N- Trillamino group, N, N-ditrilamino group, N-methyl-N-phenylamino group, N, N-dianisoylamino group, N-mesityl-N-phenylamino group, N, N-dimesitylamino group, N-phenyl- Examples thereof include N- (4-tert-butylphenyl) amino group and N-phenyl-N- (4-trifluoromethylphenyl) amino group. The alkyl group and aryl group that the amino group has as a substituent are as shown in the above-mentioned examples of the substituent.

Alkyl group, aryl group, heterocyclic group, amino group, vinyl group in the general formulas [1] and [2], the general formulas [1-1] to [1-9], and the general formulas [11] to [27]. Examples of the substituent contained in the aryl group include the following substituents. The substituents include an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group and a butyl group, an aralkyl group such as a benzyl group, an aryl group such as a phenyl group and a biphenyl group, a pyridyl group and a pyrrolyl group. Amino groups such as heterocyclic groups, dimethylamino groups, diethylamino groups, dibenzylamino groups, diphenylamino groups and ditrilamino groups, methoxyl groups, ethoxyl groups, propoxyl groups, phenoxyl groups, etc. Alkenyl group, 1,3-indandionyl group, 5-fluoro-1,3-indandonyl group, 5,6-difluoro-1,3-indandionyl group, 5,6-dicyano-1,3-indandionyl group, 5- Cyano-1,3-indandanionyl group, cyclopenta [b] naphthalene-1,3 (2H) -dionyl group, phenalen-1,3 (2H) -dionyl group, 1,3-diphenyl-2,4,6 (1H) , 3H, 5H) -Cyclic ketone groups such as pyrimidinetrionyl group, cyano group, halogen atom and the like can be mentioned. The halogen atom is fluorine, chlorine, bromine, iodine or the like, and the fluorine atom is preferable.

The general formula [1] preferably has a structure represented by the following general formula [28].

In the above general formula [28], R ₃₉₁ to R ₃₉₆ are a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryl group, a substituted or unsubstituted complex. It is independently selected from a ring group, a substituted or unsubstituted vinyl group, a substituted or unsubstituted amino group, and a cyano group. Adjacent two of R ₃₉₁ to R ₃₉₆ may be combined with each other to form a ring. In particular, it is preferable that R ₃₉₄ and R ₃₉₅ combine to form a ring.

The organic compound represented by the general formula [28] is a material having strong absorption when the absorption peak wavelength is 522 nm or more and 600 nm or less. Having an absorption peak in this wavelength region is preferable because the photoelectric conversion layer has panchromaticity as described above.

In the above general formulas [3] to [5], when M is iridium, it is preferably a 6-coordination complex. When M is platinum, vanadium, cobalt, gallium, or titanium, it is preferably a tetracoordinated complex. This is because the stability of the complex is high by using the coordination number.

Specific examples of the ligands L ₁ to L ₉ for the above general formulas [3] to [5] are shown below.
The ligands L ₁ to L ₉ are ligands in which a plurality of substituents selected from a substituted or unsubstituted aryl group and a substituted or unsubstituted heterocyclic group are bonded.
Examples of the aryl group constituting the ligand include a phenyl group, a naphthyl group, an indenyl group, a biphenyl group, a terphenyl group, a fluorenyl group, an anthrasenyl group, a pyrenyl group, a fluoranthenyl group, a peryleneyl group and the like. Not limited to.

As the heterocyclic group constituting the ligand, a pyridyl group, a pyrazil group, a triazil group, a thienyl group, a furanyl group, a pyrrolyl group, an oxazolyl group, an oxadiazolyl group, a thiazolyl group, a thiadiazolyl group, a carbazolyl group, an acridinyl group, a phenanthrolic group, Examples thereof include, but are not limited to, a benzothiophenyl group, a dibenzothiophenyl group, a benzothiazolyl group, a benzoazolyl group and a benzopyrrolyl group.

The substituents of the ligands in the general formulas [3] to [5], that is, the substituents of the aryl group and the heterocyclic group have 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group and a butyl group. Alkyl group such as alkyl group and benzyl group, aryl group such as phenyl group and biphenyl group, heterocyclic group having nitrogen atom such as pyridyl group and pyrrolyl group as complex atom, dimethylamino group, diethylamino group and dibenzylamino group. , Amino groups such as diphenylamino group and ditrilamino group, methoxyl group, ethoxyl group, propoxyl group, alkoxyl group such as phenoxyl group, 1,3-indandenyl group, 5,-fluoro-1,3-indandenyl group, 5 , 6-Difluoro-1,3-indandionyl group, 5,6-dicyano-1,3-indandonyl group, 5-cyano-1,3-indandonyl group, cyclopenta [b] naphthalene-1,3 (2H) -dionyl Group, phenalene-1,3 (2H) -dionyl group, 1,3-diphenyl-2,4,6 (1H, 3H, 5H) -pyrimidinetrionyl group and other cyclic ketone groups, cyano group, halogen atom, etc. Can be mentioned. The halogen atom is fluorine, chlorine, bromine, iodine or the like, and the fluorine atom is preferable.
The ligand has a hydroxy group, a carboxyl group, or the like as a substituent, and may be bonded to a metal atom via the hydroxy group or the carboxyl group.

Hereinafter, preferable compounds among the p-type semiconductors represented by the above general formulas [1] to [5] are exemplified.

(N-type semiconductor)
The n-type semiconductor used in the present invention is an electron-accepting organic semiconductor material, and is an organic compound having a property of easily donating electrons. Examples of the n-type semiconductor include a fullerene compound, a metal complex compound, a phthalocyanine compound, a carboxylic acid diimide compound, and the like. It is preferable to include as. By connecting the fullerene molecule or the fullerene derivative molecule in the photoelectric conversion layer, an electron transport path is formed, so that the electron transport property is improved and the high-speed response of the photoelectric conversion element is improved. Among fullerene molecules or fullerene derivative molecules, fullerene C60 is particularly preferable because it easily forms an electron transport path. The content of fullerene or fullerene derivative is preferably 40% by mass or more and 85% by mass or less from the viewpoint of good photoelectric conversion characteristics when the total amount of the photoelectric conversion layer is 100% by mass.

Examples of the fullerene or the fullerene derivative include fullerene C60, fullerene C70, fullerene C76, fullerene C78, fullerene C80, fullerene C82, fullerene C84, fullerene C90, fullerene C96, fullerene C240, fullerene 540, mixed fullerene, fullerene nanotube and the like. Will be.
The fullerene derivative has a substituent on the fullerene. Examples of this substituent include an alkyl group, an aryl group, a heterocyclic group and the like.

The photoelectric conversion layer according to the present invention preferably does not emit light. The non-emission is a layer having a emission quantum yield of 1% or less, preferably 0.5% or less, more preferably 0.1% or less in the visible light region (wavelength 400 nm to 730 nm). If the emission quantum yield of the photoelectric conversion layer exceeds 1%, it affects the sensing performance or the imaging performance when applied to a sensor or an image pickup device, which is not preferable. The emission quantum yield is the ratio of the photons emitted by luminescence to the absorbed photons. The emission quantum yield is an absolute PL quantum yield measuring device designed to prepare a thin film with the same material composition as the photoelectric conversion layer on a substrate such as quartz glass as a sample, and to obtain the value of the thin film. Can be measured using. For example, as the absolute quantum yield measuring device, "C9920-02" manufactured by Hamamatsu Photonics Co., Ltd. can be used.

(Photoelectric conversion element)
FIG. 5 is a cross-sectional view schematically showing the configuration of an embodiment of the photoelectric conversion element of the present invention. The photoelectric conversion element of the present invention has at least an anode 5, a cathode 4, and a photoelectric conversion layer 1 as a first organic compound layer arranged between the anode 5 and the cathode 4, and the photoelectric conversion layer 1 is provided. However, it has the above-mentioned specific organic semiconductor composition. The photoelectric conversion element 10 of the present embodiment is an example including a second organic compound layer 2 and a third organic compound layer 3 with the photoelectric conversion layer 1 interposed therebetween.

The cathode 4 constituting the photoelectric conversion element 10 of the present embodiment is an electrode that collects holes generated in the photoelectric conversion layer 1 arranged between the anode 5 and the cathode 4. Further, the anode 5 is an electrode that collects electrons generated in the photoelectric conversion layer 1 arranged between the anode 5 and the cathode 4. The cathode is also called a hole collecting electrode, and the anode is also called an electron collecting electrode. Either the cathode or the anode may be arranged on the substrate side. The electrodes arranged on the substrate side are also called lower electrodes.
The photoelectric conversion element of the present embodiment may be an element used by applying a voltage between the cathode and the anode.

The constituent material of the cathode 4 is not particularly limited as long as it is a material having high conductivity and transparency. Specific examples thereof include metals, metal oxides, metal nitrides, metal boronides, organic conductive compounds, and mixtures in which a plurality of types thereof are combined. More specifically, conductive metal oxides such as antimony, fluorine-doped tin oxide (ATO, FTO), tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), indium zinc oxide, gold, etc. Metallic materials such as silver, chromium, nickel, titanium, tungsten, aluminum and conductive compounds such as oxides and nitrides of these metal materials (for example, titanium nitride (TiN)), and these metals and conductive metal oxidation. Examples thereof include a mixture or a laminate with a substance, an inorganic conductive substance such as copper iodide and copper sulfide, an organic conductive material such as polyaniline, polythiophene and polypyrrole, and a laminate of these with ITO or titanium nitride. As a constituent material of the cathode 4, a material selected from titanium nitride, molybdenum nitride, tantalum nitride and tungsten nitride is particularly preferable.
Specific examples of the constituent materials of the anode 5 include ITO, indium zinc oxide, SnO ₂ , ATO (antimony-doped tin oxide), ZnO, AZO (Al-doped zinc oxide), GZO (gallium-doped zinc oxide), and TiO ₂ . , FTO (fluorine-doped tin oxide) and the like.

The method for forming the electrode can be appropriately selected in consideration of the suitability with the electrode material. Specifically, it can be formed by a wet method such as a printing method or a coating method, a physical method such as a vacuum vapor deposition method, a sputtering method or an ion plating method, or a chemical method such as CVD or plasma CVD method.
When the electrode is ITO, it can be formed by a method such as an electron beam method, a sputtering method, a resistance heating vapor deposition method, a chemical reaction method (sol-gel method or the like), or application of an ITO dispersion. Further, the formed ITO can be subjected to UV-ozone treatment, plasma treatment and the like. When the electrode is TiN, various methods such as a reactive sputtering method are used, and further annealing treatment, UV-ozone treatment, plasma treatment and the like can be performed.

In the present embodiment, the second organic compound layer 2 may be composed of one layer, may be composed of a plurality of layers, or may be a mixed layer having a plurality of kinds of materials. In the photoelectric conversion element 10 of FIG. 5, the second organic compound layer 2 has a role of transporting holes transferred from the photoelectric conversion layer 1 to the cathode 4. Further, the second organic compound layer 2 suppresses the movement of electrons from the cathode 4 to the photoelectric conversion layer 1. That is, the second organic compound layer 2 functions as a hole transport layer or an electron blocking layer, and is a preferable constituent member in preventing the generation of dark current. Therefore, it is preferable that the second organic compound layer 2 has a small electron affinity or LUMO energy.

Further, in the present embodiment, the third organic compound layer 3 has a role of transporting electrons transferred from the photoelectric conversion layer 1 to the anode 5. Further, since the third organic compound layer 3 is a hole blocking layer that suppresses the flow of holes from the anode 5 to the photoelectric conversion layer 1, it is preferably a layer having a high ionization potential. The third organic compound layer 3 may be composed of one layer, may be composed of a plurality of layers, or may be a mixed layer having a plurality of kinds of materials.

In the present invention, the layer arranged between the anode 5 and the cathode 4 is limited to the above-mentioned three types of layers (photoelectric conversion layer 1, second organic compound layer 2, and third organic compound layer 3). It's not something. An intervening layer can be further provided between the second organic compound layer 2 and the cathode 4, and at least one between the third organic compound layer 3 and the anode 5. This intervening layer is provided for the purpose of improving the charge injection efficiency when the generated charge is injected at the electrode, or preventing the charge from being injected into the organic compound layer when the charge is applied. When this intervening layer is provided, the intervening layer may be an organic compound layer, an inorganic compound layer, or a mixed layer in which an organic compound and an inorganic compound are mixed.

Although the anode 5 of the photoelectric conversion element 10 of FIG. 5 is connected to the readout circuit 6, the readout circuit 6 may be connected to the cathode 4. The readout circuit 6 plays a role of reading out information based on the electric charge generated in the photoelectric conversion layer 1 and transmitting the information to, for example, a signal processing circuit (not shown) arranged in a subsequent stage. The readout circuit 6 includes, for example, a transistor that outputs a signal based on the electric charge generated in the photoelectric conversion element 10.

In the photoelectric conversion element 10 of FIG. 5, the inorganic protective layer 7 is arranged on the cathode 4. The inorganic protective layer 7 protects a member in which the anode 5, the third organic compound layer 3, the photoelectric conversion layer 1, the second organic compound layer 2, and the cathode 4 are laminated in this order. It is a layer for. Examples of the constituent material of the inorganic protective layer 7 include silicon oxide, silicon nitride, silicon nitride oxide, and aluminum oxide. Silicon oxide, silicon nitride, and silicon nitride can be formed by a sputtering method or a CVD method, and aluminum oxide can be formed by an ALD method (atomic layer deposition method). The sealing performance of the inorganic protective layer 7 may be such that the water transmittance is 10 ^-5 g / m ² · day or less. The film thickness of the inorganic protective layer 7 is not particularly limited, but is preferably 0.5 μm or more from the viewpoint of sealing performance. On the other hand, if the sealing performance can be maintained, it is better to be thin, and it is particularly preferable that the thickness is 1 μm or less. The reason why the inorganic protective layer 7 is preferable is that when the elements are arranged two-dimensionally and used as an area sensor, the effect of reducing the color mixing is as the distance from the photoelectric conversion layer to the color filter can be shortened.

In the photoelectric conversion element 10 of FIG. 5, a color filter 8 is arranged on the inorganic protective layer 7. Examples of the color filter 8 include a color filter that transmits red light among visible light. Further, in the present invention, as a method of providing the color filter 8, one may be provided for each photoelectric conversion element, or one may be provided for each plurality of photoelectric conversion elements. Further, when arranging the color filters 8, for example, a Bayer array may be formed with an adjacent photoelectric conversion element.

In the photoelectric conversion element 10 of FIG. 5, an optical member may be arranged on the color filter 8, and in FIG. 6, a microlens 9 is arranged as the optical member. The microlens 9 plays a role of condensing the incident light on the photoelectric conversion layer 1 which is a photoelectric conversion unit. Further, in the present invention, the microlens 9 may be provided once per photoelectric conversion element or one per plurality of photoelectric conversion elements. In the present invention, it is preferable to provide one microlens 9 for each photoelectric conversion element.

In FIG. 5, the microlens 9 is arranged on the cathode 4 side to be the light incident side, but the present invention is not limited to this, and the inorganic protective layer 7 and the color filter 8 are placed on the anode 5 side. A microlens 9 may be provided. In that case, the preferred electrode materials for each of the cathode 4 and the anode 5 shown above are reversed.
Further, although not shown in FIG. 5, the photoelectric conversion element of the present invention may have a substrate. Examples of the substrate include a silicon substrate, a glass substrate, a flexible substrate, and the like. It is not limited whether the anode 5 or the cathode 4 is arranged on the substrate side, and the anode 5 / photoelectric conversion layer 1 / cathode 4 may be arranged on the substrate, or the cathode 4 / photoelectric conversion layer 1 / anode 5 may be arranged. ..
The above is the main configuration of the photoelectric conversion element. Actually, it is preferable that the photoelectric conversion element is annealed after production, but the present invention is not particularly limited by the annealing conditions.

The photoelectric conversion element according to the present invention can be a photoelectric conversion element corresponding to light of different colors by selecting the organic semiconductor used for the photoelectric conversion layer 1. Corresponding to different colors means that the wavelength region of the light to be photoelectrically converted by the photoelectric conversion layer 1 changes.
Further, by stacking a plurality of photoelectric conversion elements corresponding to different colors, it is possible to obtain a photoelectric conversion device that does not require a color filter.

FIG. 6 is an equivalent circuit diagram of one pixel 20 using the photoelectric conversion element 10 of FIG. The lower layer of the anode 5 of the photoelectric conversion element 10 is electrically connected to the charge storage unit 15 formed in the semiconductor substrate, and further connected to the amplification transistor 23. The pixel circuit includes an amplification transistor (SF MOS) 23 for amplifying a signal from the photoelectric conversion element 10, a selection transistor (SEL MOS) 24 for selecting pixels, and a reset transistor (RES MOS) 22 for resetting node B.

With such a configuration, the amplification transistor 23 can output the signal generated by the photoelectric conversion element 10. The photoelectric conversion element 10 and the amplification transistor 23 may be short-circuited. Alternatively, as shown in FIG. 6, the transfer transistor 25 may be arranged as a switch in the electric path between the photoelectric conversion element 10 and the amplification transistor 23. The transfer transistor 25 is controlled so as to be switched on and off by the switching control pulse pTX. In the pixel configuration of FIG. 6, a node B representing an electrical connection between the photoelectric conversion element 10 and the amplification transistor 23 is shown. The node B is configured so that it can be electrically floated. By electrically floating the node B, the voltage of the node B can change according to the electric charge generated by the photoelectric conversion element 10. Therefore, a signal corresponding to the electric charge generated by the photoelectric conversion element 10 can be input to the amplification transistor 23.

The pixel configuration of FIG. 6 has a reset transistor 22 that resets the voltage of the node B in the semiconductor substrate. The reset transistor 22 supplies a reset voltage (not shown) to the node B. The reset transistor 22 is controlled so as to be switched on and off by the reset control pulse pRES. When the reset transistor 22 is turned on, the reset voltage is supplied to the node B. The charge storage unit 15 is a region for accumulating the charge generated by the photoelectric conversion element 10, and is configured by forming a P-type region and an N-type region in the semiconductor substrate.

A power supply voltage is supplied to the drain electrode of the amplification transistor 23. The source electrode of the amplification transistor 23 is connected to the output line 28 via the selection transistor 24. A current source 26 is connected to the output line 28. The amplification transistor 23 and the current source 26 form a pixel source follower circuit, and output the signal voltage of the charge storage unit 15 in which the signal charge from the photoelectric conversion element 10 is stored to the output line 28. A column circuit 27 is further connected to the output line 28. The signal from the pixel 20 output to the output line 28 is input to the column circuit 27. In FIG. 6, 29 is wiring.

(Photoelectric converter)
FIG. 7 is a plan view schematically showing the configuration of an embodiment of a photoelectric conversion device using the photoelectric conversion element of the present invention. The photoelectric conversion device of the present embodiment includes an imaging region 31, a vertical scanning circuit 32, two readout circuits 33, two horizontal scanning circuits 34, and two output amplifiers 35. The area other than the image pickup area 31 is the circuit area 36.

The imaging region 31 is configured by arranging a plurality of pixels in a two-dimensional manner. As the pixel structure, the structure of the pixel 20 shown in FIG. 6 can be appropriately used. Further, the above-mentioned photoelectric conversion element 10 of the present invention may be laminated to form the pixel 20. The read circuit 33 includes, for example, a column amplifier, a CDS circuit, an adder circuit, and the like, with respect to a signal read from a pixel in a row selected by the vertical scan circuit 32 via a vertical signal line (28 in FIG. 2). Amplifies, adds, etc. The row amplifier, the CDS circuit, the addition circuit, and the like are arranged for each pixel row or a plurality of pixel trains, for example. The horizontal scanning circuit 34 generates a signal for sequentially reading the signals of the reading circuit 33. The output amplifier 35 amplifies and outputs the signal of the column selected by the horizontal scanning circuit 34.

The above configuration is merely one configuration example of the photoelectric conversion device, and the present embodiment is not limited to this. The readout circuit 33, the horizontal scanning circuit 34, and the output amplifier 35 are arranged one above and one below the image pickup region 31 in order to form two output paths. However, three or more output paths may be provided. The signal output from each output amplifier is combined as an image signal by the signal processing unit.

(Optical area sensor)
By arranging the photoelectric conversion element of the present invention two-dimensionally in the in-plane direction, it can be used as a constituent member of the optical area sensor. The optical area sensor has a plurality of photoelectric conversion elements arranged two-dimensionally in the in-plane direction. In such a configuration, by individually outputting signals based on charges generated by a plurality of photoelectric conversion elements, it is possible to obtain information showing the distribution of light intensity in a predetermined light receiving area. The photoelectric conversion element included in this optical area sensor may be replaced with the above-mentioned photoelectric conversion device.

(Image sensor)
Further, the photoelectric conversion element of the present invention can be used as a constituent member of the image pickup element. The image pickup device includes a plurality of pixels (light receiving pixels). The plurality of pixels are arranged in a matrix containing a plurality of rows and a plurality of columns. In such a configuration, an image signal can be obtained by outputting the signal from each pixel as one pixel signal. In the image pickup device, each of the plurality of light receiving pixels has at least one photoelectric conversion element and a readout circuit connected to the photoelectric conversion element. The readout circuit includes, for example, a transistor that outputs a signal based on the charge generated in the photoelectric conversion element. Information based on the read charge is transmitted to the sensor unit connected to the image sensor. Examples of the sensor unit include a CMOS sensor and a CCD sensor. In the image pickup device, an image can be obtained by collecting the information acquired by each pixel in the sensor unit.

The image pickup device may have, for example, an optical filter such as a color filter so as to correspond to each light receiving pixel. When the photoelectric conversion element corresponds to light of a specific wavelength, it is preferable to have a color filter that transmits a wavelength region to which the photoelectric conversion element can correspond. One color filter may be provided for each light receiving pixel, or one color filter may be provided for each of a plurality of light receiving pixels. The optical filter of the image pickup element is not limited to the color filter, and other low-pass filters that transmit wavelengths above infrared rays, UV cut filters that transmit wavelengths below ultraviolet rays, long-pass filters, and the like can be used.

The image pickup device may have an optical member such as a microlens so as to correspond to each light receiving pixel, for example. The microlens included in the image pickup element is a lens that collects light from the outside onto the photoelectric conversion layer constituting the photoelectric conversion element included in the image pickup element. One microlens may be provided for each light receiving pixel, or one microlens may be provided for each of a plurality of light receiving pixels. When a plurality of light receiving pixels are provided, it is preferable to provide one microlens for each of the plurality of (two or more predetermined numbers) light receiving pixels.

(Image pickup device)
The photoelectric conversion element according to the present invention can be used in an image pickup apparatus. The image pickup apparatus has an image pickup optical unit having a plurality of lenses and an image pickup element that receives light that has passed through the image pickup optical unit, and the photoelectric conversion element of the present invention is used as the image pickup element. Further, the image pickup device may be an image pickup device having a junction portion that can be joined to the image pickup optical unit and an image pickup element. More specifically, the image pickup device here means a digital camera or a digital still camera.

Further, the image pickup apparatus may further have a receiving unit for receiving a signal from the outside. The signal received by the receiving unit is a signal that controls at least one of the imaging range of the imaging device, the start of imaging, and the end of imaging. Further, the image pickup apparatus may further have a transmission unit for transmitting the image acquired by the image pickup to the outside. By having the receiving unit and the transmitting unit in this way, the image pickup apparatus can be used as a network camera.

Further, the image pickup apparatus may further have a receiving unit for receiving a signal from the outside. The signal received by the receiving unit is a signal that controls at least one of the imaging range of the imaging device, the start of imaging, and the end of imaging. Further, the image pickup apparatus may further have a transmission unit for transmitting the captured image to the outside. By having a receiving unit and a transmitting unit in this way, it can be used as a network camera.

Hereinafter, examples of the present invention will be described, but the present invention is not limited to the scope described in the following examples.
The compounds used in the examples are shown below.

(Device production)
A cathode, an electron blocking layer (EBL), a photoelectric conversion layer, a hole blocking layer (HBL), and an anode were sequentially formed on a Si substrate to produce a photoelectric conversion element. The above compounds 1 to 10 were used for the electron blocking layer, the photoelectric conversion layer, and the hole blocking layer as described in the device configuration below. Hereinafter, unless otherwise specified, only the photoelectric conversion layer is different. The manufacturing procedure is as follows.
Element configuration: Si substrate / cathode / compound as electron blocking layer (EBL) 1 / compound shown in Tables 1 to 7 as photoelectric conversion layer / compound 2 / anode as hole blocking layer (HBL)

First, a Si substrate was prepared in which a wiring layer and an insulating layer were sequentially laminated, and contact holes were provided in the insulating layer from the wiring layer at locations corresponding to each pixel so as to be conductive. The contact hole is pulled out to the end of the substrate by wiring to form a pad portion. An IZO electrode was formed so as to overlap the contact hole portion, and desired patterning was performed to form an IZO electrode (cathode) having a size of 3 mm ² . At this time, the film thickness of the IZO electrode was set to 100 nm. An electron blocking layer, a photoelectric conversion layer, and a hole blocking layer were sequentially vacuum-deposited on the IZO substrate, and an IZO layer similar to the cathode was formed by sputtering to form an anode.

After forming the anode, hollow sealing was performed using a glass cap and an ultraviolet effect resin to obtain a photoelectric conversion element. The photoelectric conversion element thus obtained was annealed on a hot plate at 170 ° C. with the sealing surface facing upward for about 1 hour in order to stabilize the element characteristics.

When a voltage of 5 V was applied to the obtained photoelectric conversion element and the current value flowing was confirmed, the ratio of (current in bright place) / (current in dark place) = 10 times or more was found in all the elements. It was confirmed that it functions as a photoelectric conversion element. Next, the photoelectric conversion element was held in a constant temperature bath at 60 ° C., and a prober wired to a semiconductor parameter analyzer (Agilent Co., Ltd. “4155C”) was brought into contact with the electrode to measure the dark current.

In the table below, "% by mass" is the sum of the first organic semiconductor, the second organic semiconductor, and the third organic semiconductor in the ternary configuration, and the first organic semiconductor and the second organic semiconductor in the dual configuration. The content of each organic semiconductor is shown when the total of the above is 100% by mass. Further, also in the description of the table below, the "content" means the content of each organic semiconductor when the above-mentioned ternary composition or binary composition is 100% by mass. The "mass ratio" in the table is the content of the third organic semiconductor with respect to the content of the second organic semiconductor.

In Comparative Example 1 shown in Table 1, the photoelectric conversion layer is composed of two materials, compound 2 as a first organic semiconductor and compound 3 as a second organic semiconductor. In Comparative Examples 2 and 3, and Examples 1 to 4, the photoelectric conversion layer contains the compound 2 as the first organic semiconductor and the content as the second organic semiconductor in an amount of 25% by mass, which is the same as that of Comparative Example 1. It is composed of a compound 4 as a third organic semiconductor in addition to a certain compound 3. As shown in Table 4 described later, Comparative Examples 2, 3 and Examples 1 to 4 satisfy the above formulas (1) and (2). Here, the relative dark current in Comparative Examples 2 and 3 and Examples 1 to 4 is the ratio of the dark current to Comparative Example 1. From Table 1, in Examples 1 to 4 in which the content of the third organic semiconductor is 3% by mass or more, the dark current is significantly reduced as compared with Comparative Example 1 having no third organic semiconductor. I understand. On the other hand, in Comparative Examples 2 and 3 in which the content of the third organic semiconductor was less than 3% by mass, a decrease in dark current could not be confirmed as compared with Comparative Example 1 having no third organic semiconductor. Further, in the mass ratio of the third organic semiconductor to the second organic semiconductor, Examples 1 to 4 having the mass ratio of 0.12 or more are compared with Comparative Example 1 having no third organic semiconductor. , The dark current has decreased.

In Comparative Examples 1, 4, 5, 6 and 7 shown in Table 2, the photoelectric conversion layer is composed of two materials, compound 2 as a first organic semiconductor and compound 3 as a second organic semiconductor. In Examples 1, 5, 6, 7 and Comparative Example 8, the photoelectric conversion layer has compound 2 as the first organic semiconductor and Comparative Examples 1, 4, 5, 6 and 7 as the second organic semiconductor. In addition to the compound 3 which is the same as the above, the compound 4 as a third organic semiconductor is contained in an amount of 3% by mass. As shown in Table 4 described later, Examples 1, 5, 6, 7 and Comparative Example 8 satisfy the above formulas (1) and (2). Here, the relative dark currents in Examples 1, 5, 6, 7 and Comparative Example 8 are the ratios of the dark currents to Comparative Examples 1, 4, 5, 6, and 7, respectively. From Table 2, Examples 1, 5, 6 and 7 in which the content of the second organic semiconductor is larger than 6% by mass are shown in Comparative Examples 1, 4, 5 and 6 having no third organic semiconductor. On the other hand, it can be seen that the dark current is significantly reduced. On the other hand, in Comparative Example 8 in which the content of the second organic semiconductor was less than 6% by mass, a decrease in dark current could not be confirmed as compared with Comparative Example 7 having no third organic semiconductor. Further, when the content of the second organic semiconductor is 10% by mass or more, the dark current reduction effect by mixing the third organic semiconductor is larger than the relative dark currents of Examples 1, 5 and 6, which is preferable. I understand. Further, when the content of the second organic semiconductor is 17% by mass or more, the dark current reduction effect by mixing the third organic semiconductor is larger than the relative dark currents of Examples 1 and 5, which is more preferable. I understand.

In Comparative Examples 9 and 10 shown in Table 3, the photoelectric conversion layer is composed of two materials, compound 2 as a first organic semiconductor and compound 3 as a second organic semiconductor. In Examples 8 and 9 and Examples 10 and 11, in addition to the compound 2 having the photoelectric conversion layer as the first organic semiconductor and the compound 3 having the same photoelectric conversion layer as the comparative examples 9 and 10 as the second organic semiconductor. , Consists of compound 4 as a third organic semiconductor. As shown in Table 4 described later, Examples 8 to 11 satisfy the above formulas (1) and (2). Table 3 shows the case where the content of the second organic semiconductor is higher than that in Table 2.

(Evaluation result of conversion efficiency)
In order to obtain a high S / N ratio, it is preferable that the efficiency of photoelectric conversion is high, and the measurement and evaluation results of the efficiency of photoelectric conversion will be described below. First, in order to evaluate in advance the conversion efficiency (η) for each pair of p-type-n-type combinations, a photoelectric conversion element having a photoelectric conversion layer containing 25% by mass of each p-type semiconductor is subjected to photoelectric conversion. It was prepared and evaluated by the same method as in other examples except for the layer. The results are shown in Table 4. The conversion efficiency is
From the relationship of conversion efficiency (η) = EQE / absorption rate of the photoelectric conversion layer, EQE is a value obtained by dividing EQE by the absorption rate of the photoelectric conversion layer obtained from the extinction coefficient of a separately formed film. Specifically, only the photoelectric conversion layer was formed on the Si substrate, the extinction coefficient was obtained by spectroscopic ellipsometry, and the absorption rate calculated based on the film thickness was used. If the element is a transparent substrate instead of a Si substrate, the absorption rate may be directly obtained by measuring the transmitted light.

Table 4 shows the EQE peak and conversion efficiency (η) of the photoelectric conversion element by the combination of a pair of p-type −n type organic semiconductors. These are shown as the characteristics of the dual element configuration of the combination of pn included as the configuration in the photoelectric conversion layer having the ternary configuration. The EQE peak wavelength measures the current when light of each wavelength is irradiated and when it is not irradiated, using a spectral sensitivity light source and a semiconductor parameter analyzer (Agient Co., Ltd. "4155C") for a photoelectric conversion element placed in a dark place. And the optical current was calculated. The photocurrent was converted into the number of electrons and divided by the number of incident photons to obtain EQE. As a result, the EQE of each wavelength was measured to obtain the spectral sensitivity characteristics, and the sensitivity peak wavelength on the longest wavelength side was obtained. The bandgap is also shown as an index of the excitation energy of each material. This bandgap was calculated from the absorption spectrum measurement of a thin film formed by vacuum deposition of each 100% film with a film thickness of about 100 nm.
The conversion efficiency of the photoelectric conversion layer can be estimated from the conversion efficiency (η) of the photoelectric conversion element having the photoelectric conversion layer.

The conversion efficiency (η) in Table 4 was evaluated as follows as the conversion efficiency of the dual element at a drive voltage of 5 V.
A: η ≧ 80%
B: η <80%

In the above photoelectric conversion element configuration, the content of the second organic semiconductor is 25% by mass, but it is used as an index for comparing each combination, and the conversion efficiency (η) is evaluated. It is not limited to 25% by mass. For example, the present inventors have confirmed that the above-mentioned conversion efficiency (η) is substantially constant when the content of the second organic semiconductor is about 15 to 50% by mass, and such a content range is set. It suffices if the maximum conversion efficiency value is determined based on this.

Next, the energy difference (ΔEg) determined by the difference in the EQE peak wavelengths of the dual constituent elements using organic semiconductors contained in the constituent materials of the ternary element and the rate of increase in conversion efficiency at 550 nm in the ternary element are used as indicators. The result of evaluation as is shown. The "rate of increase in conversion efficiency at 550 nm" in Table 5 as an index of effect is the one with the lower conversion efficiency in the combination of pns in which the conversion efficiency of the ternary element of the present invention can be configured as a binary element. It is the value divided by. The OSC described in the table is an abbreviation for Organic Semiconductor and is described for convenience because it is abbreviated in the table. The contents of the second and third organic semiconductors are set as close as possible in order to determine the effect.

In Table 5, Comparative Example 11 and Comparative Examples 12 and 13 have a dual configuration and a ternary configuration. As a similar relationship, Examples 12 and 13 correspond to Comparative Example 14, Example 14 corresponds to Comparative Example 15, Example 15 corresponds to Comparative Example 16, and Example 16 corresponds to Comparative Example 17. do. From the results in Table 5, it can be seen that the closer the ΔEg of the configurable dual element is to 0, the higher the rate of increase in conversion efficiency. The data of the configurable binary element is based on the contents shown in Table 4.

The relationship between ΔEg in Table 5 and the rate of increase in conversion efficiency at 550 nm is shown in FIG. As shown in FIG. 8, it had a bending point near 0.052 eV. At that time, considering the accuracy of EQE measurement, it was judged to be effective that the rate of increase in conversion efficiency was 102% or more in this evaluation. As a result, it was shown that ΔEg is preferably 0.052 eV or less. This result shows that excitons relaxed to a low energy level can be charge-separated with high efficiency by using another pn combination if the barrier is about 0.052 eV or less. As for the rate of increase in conversion efficiency, the larger the difference between the conversion efficiencies η ₁ and η ₂ between the dual element 1 and the binary element 2 to be combined, the greater the effect, of course. In this example, η ₁ and η ₂ were selected to have a difference of 10% or more. However, in the present invention, the difference is not limited to 10% or more, and as described above, the energy level of each pn constituting the binary element 1 and the binary element 2 is not limited. The relationship of rank is important.

Next, the preferable contents of the first organic semiconductor, the second organic semiconductor and the third organic semiconductor were verified. In this verification, in the relationship between the binary element 1 and the binary element 2 shown in FIG. 4, it is a verification as to which concentration of the relationship between the second organic semiconductor and the third organic semiconductor should be higher.

From Table 6, as shown in Examples 12, 17 to 22, when the second organic semiconductor is compound 4, the conversion efficiency is high in the ternary element. This is because the higher the content of the organic semiconductor constituting the dual element 1 having high conversion efficiency, the higher the ratio of direct photoelectric conversion, and the charge separation by receiving energy from the organic semiconductor constituting the binary element 2. It is derived from the fact that the rate of increasing the probability of causing the disease increases. On the contrary, when the second organic semiconductor is compound 5 as in Examples 23 to 29, the conversion efficiency of the ternary element at 550 nm is increased, but the effect is not large. Therefore, it was shown that the first and second organic semiconductors are preferable as the combination having high conversion efficiency. Further, although not described, in any combination of Table 5, the dark current lowering effect of the ternary element as seen in Tables 1 to 3 was observed.

(Verification experiment)
In order to analyze the cause of the dark current generation, the temperature dependence of the dark current of the photoelectric conversion element of Comparative Example 18 was measured and an Arrhenius plot was performed, and the activation energy was obtained according to the following equation (5). The results are shown in FIG. The inclination increases toward the high temperature side from about 60 ° C. (T / 1000 = 3.0). From this slope, the activation energy was obtained according to the following equation (5).

Here, T: temperature, k _B : Boltzmann constant, E _a : activation energy, J: current value at temperature T, J ₀ : frequency factor.

The activation energies of the photoelectric conversion elements of Comparative Examples 19 and 20 and Example 30 were obtained in the same manner as in Comparative Example 18. Table 8 shows the activity of the photoelectric conversion layer in each photoelectric conversion element, and the activity standardized by the values of the photoelectric conversion element (Comparative Example 19) in which the photoelectric conversion layer containing 25% by mass of compound 3 has a dual configuration. The activation energy and dark current are summarized.

From Table 7, it can be seen that in the element having the dual structure of the photoelectric conversion layer, the activation energy decreases and the dark current increases as the content of the compound 3 which is the second organic semiconductor is increased. The reason is that when the content of the second organic semiconductor increases, the second organic semiconductors associate with each other and the energy distribution of the density of states of the HOMO level expands, so that the activation energy decreases and the dark current Is thought to increase.

On the other hand, the photoelectric conversion element of Example 30 is a comparative example in terms of the content of the p-type semiconductor (total amount of the second organic semiconductor and the third organic semiconductor) because the third organic semiconductor is mixed. Despite being more than 19, the activation energy is large and the dark current is low. This is because when the first organic semiconductor and the third organic semiconductor are mixed in addition to the second organic semiconductor, it is possible to suppress the association between the second organic semiconductors and the intensification of the interaction due to stacking. it is conceivable that. As a result, it is considered that the energetic spread of the density of states of the HOMO level can be suppressed.

As described above, the present invention focuses on the dark current generation mechanism and the energy transfer phenomenon in the photoelectric conversion layer, and is not limited by the configuration described in the present embodiment. For example, an electron blocking layer or a hole blocking layer different from the examples may be used. Further, in the present invention, the first organic semiconductor is n-type and the second and third organic semiconductors are p-type, but the present invention is not limited thereto. This is because the point of interest does not depend on whether it is n-type or p-type.

From the above, the organic photoelectric conversion element of the present invention is an element having excellent characteristics of being capable of photoelectric conversion with low dark current and high sensitivity. Therefore, in the optical area sensor, the image pickup device, and the image pickup device using the organic photoelectric conversion element of the present invention, the dark current noise derived from the photoelectric conversion element can be reduced.

1: Photoelectric conversion layer, 4: Cathode, 5: Anode, 6: Read circuit, 10: Photoelectric conversion element

Claims (15)

In a photoelectric conversion element having at least an anode, a photoelectric conversion layer, and a cathode in this order, wherein the photoelectric conversion layer is composed of at least a first organic semiconductor, a second organic semiconductor, and a third organic semiconductor. ,
The first organic semiconductor, the second organic semiconductor, and the third organic semiconductor are all low molecular weight organic semiconductors.
The first organic semiconductor is an n-type semiconductor, the second organic semiconductor is a p-type semiconductor, and the like.
The mass ratio of the first organic semiconductor, the second organic semiconductor, and the third organic semiconductor is
The first organic semiconductor ≧ the second organic semiconductor ≧ the third organic semiconductor,
When the total of the first organic semiconductor, the second organic semiconductor and the third organic semiconductor is 100% by mass, the content of the second organic semiconductor is 6% by mass or more, and the third organic The content of the semiconductor is 3% by mass or more,
The second organic semiconductor and the third organic semiconductor are selected from the compounds represented by the following general formulas [2] to [5] and the compounds represented by the following general formula [28], respectively. At least one of the organic semiconductor and the third organic semiconductor is a compound represented by the following general formula [28].
A photoelectric conversion element having a photoelectric conversion layer having the first organic semiconductor and the second organic semiconductor, and a photoelectric conversion layer having the first organic semiconductor and the third organic semiconductor. When the conversion element and the two photoelectric conversion elements are configured, the peak wavelengths in the spectral sensitivity spectrum of the external quantum efficiency with respect to the incident light of the two photoelectric conversion elements are the same, or the following equations (1) and (2) are used. A photoelectric conversion element characterized by satisfying.
η ₁ > η ₂ ... (1)
| ΔEg | ≤0.052 eV ... (2)
(Η ₁ : Conversion efficiency represented by the external quantum efficiency / absorption rate of the photoelectric conversion layer of the photoelectric conversion element having the peak on the short wavelength side of the two photoelectric conversion elements η ₂ : Of the two photoelectric conversion elements Of these, the conversion efficiency ΔEg of the photoelectric conversion element having the peak on the long wavelength side: the energy difference determined by the difference in the wavelengths of the peaks of the two photoelectric conversion elements).

(In the general formula [28],
R ₁ is a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted vinyl group, Represents a substituted or unsubstituted amino group or cyano group.
R ₃₉₁ to R ₃₉₆ are hydrogen atom, halogen atom, substituted or unsubstituted alkyl group, substituted or unsubstituted alkoxy group, substituted or unsubstituted aryl group, substituted or unsubstituted heterocyclic group, substituted or unsubstituted. It is independently selected from a vinyl group, a substituted or unsubstituted amino group, and a cyano group. Adjacent two of R ₃₉₁ to R ₃₉₆ may be combined with each other to form a ring.
Z ₁ represents either a halogen atom, a cyano group, a substituted or unsubstituted heteroaryl group or a substituent represented by the following general formulas [1-1] to [1-9].

(In the general formulas [1-1] to [1-9], R ₅₂₁ to R ₅₈₈ are a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, and a substituted or unsubstituted aryl. It is independently selected from a group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted vinyl group, a substituted or unsubstituted amino group, and a cyano group. * Indicates a bond position with a carbon atom.))

(In the general formula [2]
R ₂₀ to R ₂₉ are hydrogen atom, halogen atom, substituted or unsubstituted alkyl group, substituted or unsubstituted alkoxy group, substituted or unsubstituted aryl group, substituted or unsubstituted heterocyclic group, substituted or unsubstituted. It is independently selected from a vinyl group, a substituted or unsubstituted amino group, and a cyano group. Two adjacent two of R ₂₀ to R ₂₉ may be combined with each other to form a ring. )

(In the general formulas [3] to [5],
M is a metal atom, and the metal atom may have an oxygen atom or a halogen atom as a substituent.
L ₁ to L ₉ are ligands coordinated to the metal M and consist of a substituted or unsubstituted aryl group and a substituted or unsubstituted heterocyclic group, which are adjacent 2 of L ₁ to L ₉ , respectively. Represents a ligand that may be bonded to each other to form a ring. ) The first aspect of the present invention is characterized in that the second organic semiconductor and the third organic semiconductor are selected from the compound represented by the general formula [2] and the compound represented by the general formula [28], respectively. The photoelectric conversion element described. The photoelectric conversion element according to claim 1, wherein both the second organic semiconductor and the third organic semiconductor are compounds represented by the general formula [28]. The photoelectric conversion element according to any one of claims 1 to 3, wherein in the general formula [28], the R ₃₉₄ and the R ₃₉₅ are coupled to form a ring. The invention according to any one of claims 1 to 4, wherein the photoelectric conversion layer of the photoelectric conversion element having the peak on the short wavelength side is composed of the first organic semiconductor and the second organic semiconductor. Photoelectric conversion element. The photoelectric conversion element according to any one of claims 1 to 5, wherein the mass ratio of the third organic semiconductor to the second organic semiconductor is 0.12 or more. When the total of the first organic semiconductor, the second organic semiconductor and the third organic semiconductor is 100% by mass, the content of the second organic semiconductor is 10% by mass or more. Item 2. The photoelectric conversion element according to any one of Items 1 to 6. The photoelectric conversion element according to any one of claims 1 to 7, wherein the third organic semiconductor is a p-type semiconductor. The photoelectric conversion element according to any one of claims 1 to 8, wherein the first organic semiconductor is a fullerene or a fullerene derivative. The photoelectric conversion element according to claim 9, wherein the fullerene or the fullerene derivative is fullerene C60. An optical area sensor having a plurality of pixels including a photoelectric conversion element, and the plurality of pixels are arranged two-dimensionally.
The optical area sensor according to any one of claims 1 to 10, wherein the photoelectric conversion element is the photoelectric conversion element. An image pickup device having a plurality of pixels including a photoelectric conversion element and a readout circuit connected to the photoelectric conversion element, and a signal processing circuit connected to the pixels.
The image pickup element according to any one of claims 1 to 10, wherein the photoelectric conversion element is the photoelectric conversion element. An image pickup apparatus comprising an image pickup optical unit having a plurality of lenses and an image pickup element that receives light that has passed through the image pickup optical unit, wherein the image pickup element is the image pickup element according to claim 12. The image pickup device further includes a receiving unit that receives a signal from the outside, and the signal is a signal that controls at least one of the image pickup range, the start of image pickup, and the end of image pickup of the image pickup device. 13. The imaging device according to claim 13. The image pickup device according to claim 13, wherein the image pickup device further includes a transmission unit for transmitting the acquired image to the outside.

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