WO2018147202A1

WO2018147202A1 - Photoelectric conversion element, optical area sensor using same, imaging element, and imaging device

Info

Publication number: WO2018147202A1
Application number: PCT/JP2018/003691
Authority: WO
Inventors: 哲生高橋; 塩原　悟; 鎌谷　淳; 山田　直樹; 智奈山口; 博揮大類; 岩脇　洋伸; 真澄板橋; 洋祐西出; 広和宮下; 典史梶本; 萌恵野口; 功河田; 祐斗伊藤
Original assignee: キヤノン株式会社
Priority date: 2017-02-07
Filing date: 2018-02-02
Publication date: 2018-08-16

Abstract

Provided is a photoelectric conversion element that includes: an anode; a photoelectric conversion layer comprising a first organic semiconductor, a second organic semiconductor, and a third organic semiconductor; and a cathode. The first organic semiconductor, second organic semiconductor, and third organic semiconductor are all low-molecular organic semiconductors; the mass ratio thereof satisfies the first organic semiconductor ≥ second organic semiconductor ≥ third organic semiconductor; and when the sum of the first organic semiconductor, second organic semiconductor, and third organic semiconductor is 100 mass%, the content of the second organic semiconductor is 6 mass% or more, and the content of the third organic semiconductor is 3 mass% or more.

Description

Photoelectric conversion element, and optical area sensor, imaging element, and imaging apparatus using the same

This invention relates to the photoelectric conversion element provided with the photoelectric converting layer comprised with an organic semiconductor.

2. Description of the Related Art In recent years, development of solid-state imaging devices having a structure including a photoelectric conversion layer made of an organic compound and formed on a signal readout substrate has been progressing.
A general structure of the organic photoelectric conversion layer includes 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. Thus, development of photoelectric conversion elements that exhibit higher performance has been performed.
Patent Document 1 discloses a small amount of low-molecular-weight organic compound in addition to a bulk heterostructure of a p-type organic semiconductor and an n-type organic semiconductor as a photoelectric conversion layer excellent in heat resistance that suppresses an increase in dark current accompanying a temperature rise. The containing structure is disclosed. Further, Patent Document 2 discloses a photoelectric conversion layer that has improved incident light absorption efficiency by including a structure containing two or more types of electron-donating polymer organic materials in addition to an electron-accepting material. Has been.
In

Patent Documents

1 and 2, as a photoelectric conversion layer made of an organic compound, by adding a third compound in addition to a p-type organic semiconductor and an n-type organic semiconductor, an increase in dark current due to a temperature rise is suppressed. Alternatively, it is disclosed to increase the absorption efficiency of incident light. However, there is no disclosure about a configuration that reduces the dark current of the photoelectric conversion element at room temperature.
Therefore, the present invention aims to reduce dark current in a photoelectric conversion element having a photoelectric conversion layer composed of a bulk heterostructure of a p-type organic semiconductor and an n-type organic semiconductor, and using the photoelectric conversion element, a low-noise optical area. An object is to provide a sensor, an imaging device, and an imaging device.

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

The photoelectric conversion element of the present invention has an anode, a photoelectric conversion layer, and a cathode in this order, and the photoelectric conversion layer includes 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 organic semiconductors, and the first organic semiconductor and the second organic semiconductor Among the semiconductors, one is a p-type semiconductor, the other is an n-type semiconductor, and the mass ratio of the first organic semiconductor, the second organic semiconductor, and the third organic semiconductor is:
First organic semiconductor ≧ second organic semiconductor ≧ third organic semiconductor, and when the total of the first organic semiconductor, the second organic semiconductor, and the third organic semiconductor is 100% by mass, The photoelectric conversion element is characterized in that 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.

According to the present invention, a photoelectric conversion element capable of performing photoelectric conversion with a low dark current can be provided by configuring the photoelectric conversion layer with three kinds of low-molecular organic semiconductors.

FIG. 1 is a schematic diagram showing a dark current generation mechanism in a photoelectric conversion layer. FIG. 2 is a schematic diagram for explaining the effect of the third organic semiconductor according to the present invention. FIG. 3 is a schematic view of a mixed film of a first organic semiconductor and a second organic semiconductor approximated to a rectangular parallelepiped. FIG. 4 is a diagram showing a correspondence relationship between experimental values and calculated values of SP values of organic semiconductors. FIG. 5 is a schematic diagram showing an example of a preferable relationship between the oxidation potential and the reduction potential of the organic semiconductor according to the present invention. FIG. 6 is a schematic diagram showing an example of a preferable oxidation potential / reduction potential relationship of the organic semiconductor according to the present invention. FIG. 7 is a schematic cross-sectional view of one embodiment of the photoelectric conversion element of the present invention. FIG. 8 is an equivalent circuit diagram of an example of a pixel including the photoelectric conversion element shown in FIG. FIG. 9 is a plan view schematically showing a configuration of a photoelectric conversion device using the photoelectric conversion element of the present invention. FIG. 10 is a diagram showing a waveform example when determining the oxidation potential and reduction potential of the organic semiconductor used in the present invention by cyclic voltammetry. FIG. 11 is a diagram illustrating an Arrhenius plot of the dark current value of the photoelectric conversion element of the example of the present specification. FIG. 12 is a graph in which the increase rate of the conversion efficiency of the photoelectric conversion element of the example of the present specification is plotted against ΔEg.

The embodiments of the present invention will be described in detail with reference to the drawings as appropriate, but are not limited to the embodiments described below. In addition, a well-known or publicly known technique in the technical field can be applied to a part not specifically described in the following description or a part not specifically illustrated in the drawings.

The photoelectric conversion element of the present invention is a photoelectric conversion element having a reduced dark current, which includes a photoelectric conversion layer made of an organic compound between an anode and a cathode. The photoelectric conversion layer of the present invention has a p-type organic semiconductor and an n-type organic semiconductor, and further has a third organic semiconductor to reduce dark current. 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 organic semiconductors.

(Photoelectric conversion layer)
First, the photoelectric conversion layer that is a feature of the present invention will be described.
The photoelectric conversion layer generates charges according to the amount of light by absorbing 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 these organic semiconductors are all low molecular organic semiconductors. 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”). ). Specifically, of the first organic semiconductor and the second organic semiconductor, the one with a lower oxidation potential is a p-type semiconductor, and the one with a higher oxidation potential is an n-type semiconductor. Photoelectric conversion 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 such that the first organic semiconductor ≧ the second organic semiconductor ≧ the third organic semiconductor.
In addition, in the first organic semiconductor, the second organic semiconductor, and the third organic semiconductor, when the content (% by mass) in the photoelectric conversion layer is equal, the first, second, Third. That is, when three types of organic semiconductors are equally contained, the organic semiconductor having the largest molecular weight among the three types of organic semiconductors is the first organic semiconductor, and the molecular weight of the three types of organic semiconductors is the same. The smallest organic semiconductor is the third organic semiconductor. Moreover, when two types of content is equal among three types of organic semiconductors and the content of the remaining one type is higher than the previous two types, the higher the molecular weight among the two types of organic semiconductors. The smaller one of the two organic semiconductors is the third organic semiconductor. Moreover, when two types of content is equal among three types of organic semiconductors and the content of the remaining one type is less than the previous two types, the higher the molecular weight of the two types of organic semiconductors, One organic semiconductor and the smaller one is the second organic semiconductor.

Moreover, the photoelectric conversion layer according to the present invention may be composed of at least the first organic semiconductor, the second organic semiconductor, and the third organic semiconductor. Other than these materials, that is, other materials may be included as long as the current reduction effect is not impaired. The mass ratio of the other material may be equal to or less than the content of the third organic semiconductor. The other material may be an organic semiconductor different from the first to third organic semiconductors. In this case, the mass ratio of the other material that is the organic semiconductor is not more than the content of the third organic semiconductor. is there. When the other material is an organic semiconductor and the content thereof is equal to the content of the third organic semiconductor, the one having a higher molecular weight is the third organic semiconductor.

The third organic semiconductor of the present invention is added to suppress 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, the third organic semiconductor is also preferably a p-type semiconductor. Similarly, when the second organic semiconductor is an n-type semiconductor, the third organic semiconductor is also An n-type semiconductor is preferable. Whether the third organic semiconductor is a p-type semiconductor or an n-type semiconductor can be estimated by its oxidation potential. When the oxidation potential of the third organic semiconductor is close to the oxidation potential of a compound that 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 a compound that is an n-type semiconductor of the first organic semiconductor and the second organic semiconductor, the third organic semiconductor is an n-type semiconductor. is there. As a result, the photoelectric conversion function of the second organic semiconductor having a lower content in the photoelectric conversion layer than the first organic semiconductor (the electron donor function if the second organic semiconductor is a p-type semiconductor, the electron if the second organic semiconductor is an n-type semiconductor) The acceptor function) may be supplemented by a third organic semiconductor.

The wavelength at which the absorptance in the visible light region (wavelength 400 nm to 730 nm) of the third organic semiconductor thin film is maximized is the absorptance in the visible light region of each of the first organic semiconductor and the second organic semiconductor. It is preferable that the wavelength is between two wavelengths that are maximum. Thereby, the absorption of the wavelength region between the absorption bands 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 semiconductor The semiconductor content is 3% by mass or more. The present inventors have found that a photoelectric conversion element exhibiting good photoelectric conversion characteristics can be produced when the composition of the organic semiconductor in the photoelectric conversion layer satisfies the above relationship. Details will be described below.

A conventional photoelectric conversion layer has a bulk heterostructure in which a p-type semiconductor and an n-type semiconductor are mixed. That is, the photoelectric conversion layer has a binary configuration in which two types of organic semiconductors, a first organic semiconductor and a second organic semiconductor, are used in combination. The mass ratio of the first organic semiconductor in the photoelectric conversion layer is larger than the mass ratio of the second organic semiconductor. In such a photoelectric conversion layer, the first organic semiconductor and the second organic semiconductor supplement each other's absorption wavelength region, whereby panchromatic absorption can be obtained. In such a configuration, sufficient panchromatic absorption can be realized when the mass ratio of the second organic semiconductor in the photoelectric conversion layer is larger.

However, the present inventors have found that the dark current when a voltage is applied to the photoelectric conversion element increases as the mass ratio of the second organic semiconductor increases. The reason will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing a basic dark current generation mechanism in a photoelectric conversion layer. HOMO (highest occupied orbital) level, LUMO (lowest empty orbital) in a single molecule of a p-type semiconductor and an n-type semiconductor. ) The level relationship is illustrated. It is considered that the dark current is generated when electrons existing in the HOMO level of the p-type semiconductor move to the LUMO level of the n-type semiconductor by thermal energy. In this case, the energy barrier for electron transfer is ΔE ₁ .

However, in the mixed film of the first organic semiconductor and the second organic semiconductor, each is associated with the same compound, for example, by forming a dimer. As a result, the density of states of the HOMO level and the LUMO level forms an energy spread.

FIG. 2 is a schematic view for explaining the effect of the third organic semiconductor of the photoelectric conversion element of the present invention. The solid line in FIG. 2 schematically represents the energy distribution of the state density of the HOMO level and the LUMO level in the binary mixed film of the first organic semiconductor and the second organic semiconductor. On the other hand, the broken line is a schematic diagram of the state density energy distribution in the mixed film of the ternary configuration of the first organic semiconductor, the second organic semiconductor, and the third organic semiconductor. The broken line will be described later. In FIG. 2, the first organic semiconductor is an n-type semiconductor, and the second organic semiconductor is a p-type semiconductor.
The energy barrier ΔE _{2 for} electron transfer considering the energy spread of the binary density of states is smaller than ΔE ₁ when considered in terms of the energy level of a single molecule. The smaller the energy barrier ΔE _{2 for} electron transfer, the greater the dark current. That is, as the energy spread of the state density is wider, ΔE ₂ becomes smaller and dark current is more likely to occur. Therefore, as the mass ratio of the second organic semiconductor in the photoelectric conversion layer increases, the compounds in the second organic semiconductor are more likely to associate with each other, and the energy density of the state density of the HOMO level and the LUMO level is increased. It is thought that it becomes easy to spread. For this reason, it is considered that the dark current increases as the mass ratio of the second organic semiconductor increases.

The phenomenon of forming an energy spread of the density of states of the HOMO level and the LUMO level due to the association of the compounds in the second organic semiconductor described above is that the mass ratio of the second organic semiconductor is the first and the second. It is known that when the sum of the two organic semiconductors is 100% by mass, it occurs when the amount is 6% by mass or more. Non-Patent Document 1 describes that in a mixed film of two kinds of organic compounds, molecules are associated with each other when the organic compound at a low concentration is 6% by mass or more. Specifically, it is described that at a mass ratio of 6% by mass or more, the emission of the organic compound becomes longer in wavelength and the tendency of concentration quenching begins to appear. The increase in the wavelength of light emission is considered to be due to the fact that the energy spread of the state density of the HOMO level and the LUMO level is increased and the effective band gap is reduced.

As a countermeasure against an increase in dark current as the mass ratio of the second organic semiconductor increases, the present inventors have discovered the following as a result of intensive studies. Even if the mass ratio of the second organic semiconductor is 6% by mass or more, only the first organic semiconductor and the second organic semiconductor can be obtained 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 mass ratio of the second organic semiconductor is 6% by mass or more, and the mass ratio of the third organic semiconductor is 3% by mass or more. And the mass ratio when the total amount of the second organic semiconductor and the third organic semiconductor is 100% by mass.

Below, the mechanism of the dark current reduction effect by the mixing of the third organic semiconductor considered by the present inventors will be described with reference to FIG.
The state density energy represented by the broken line in FIG. 2 represents the HOMO level in the binary mixed film of the first organic semiconductor and the second organic semiconductor of the photoelectric conversion element of the present invention having the third organic semiconductor. 4 schematically shows an energy distribution of density of states of LUMO levels. The state density energy represented by the broken line is less spread than the state density energy represented by the solid line. This is considered that the association of the compounds in the second organic semiconductor is suppressed by further having the third organic semiconductor. As a result, the energy spread of the state density of each level can be suppressed. Interactions due to association of organic compounds, dimer formation, stacking, and the like are particularly likely to occur between the same compounds, and therefore, when different compounds coexist, they are inhibited. Moreover, the effect of suppressing the energy spread of the state density by the third organic semiconductor is also brought about for the first organic semiconductor. However, the second organic semiconductor having a smaller mass ratio than the first organic semiconductor is more likely to achieve a highly dispersible state because the molecules are not associated with each other due to the mixing of the third organic semiconductor. As a result, it is considered that the second organic semiconductor can more easily suppress the energy spread of the state density of each level.

In FIG. 2, the first organic semiconductor is an n-type semiconductor and the second organic semiconductor is a p-type semiconductor. However, the first organic semiconductor is a p-type semiconductor and the second organic semiconductor. In the case where n is an n-type semiconductor, it is considered that the effect of mixing the third organic semiconductor is similarly exhibited. The effect obtained by adding the third organic semiconductor can be obtained even when the mass ratio of the first organic semiconductor and the second organic semiconductor is equal.

In the present invention, the total amount of the first, second, and third organic semiconductors is 100% by mass, and the mass ratio of the third organic semiconductor is 3% by mass or more. , Preferably 6% by mass or more, particularly preferably 10% by mass or more. The ratio of the mass ratio of the third organic semiconductor to the mass ratio of the second organic semiconductor is preferably 0.12 or more. This is because the association of the second organic semiconductor can be effectively suppressed by the third organic semiconductor. The ratio is more preferably 0.24 or more, and particularly preferably 0.4 or more.

In the photoelectric conversion element according to the present invention, the total amount of the first, second, and third organic semiconductors is 100% by mass, and the mass ratio of the second organic semiconductor is more preferably 10% by mass or more. Patent Document 3 describes that when two compounds are mixed, concentration quenching of light emission occurs remarkably when the compound having the lower mixing concentration is 10% by mass or more. That is, when the content is 10% by mass or more, more remarkable association occurs. Therefore, also in the present invention, when the total amount of the first, second, and third organic semiconductors is 100% by mass, the second organic semiconductors are It is considered that the association is remarkable, and the effect of adding the third organic semiconductor is considered to be more remarkable. Moreover, the light absorption factor of the absorption band of a 2nd organic semiconductor can be made high by making a 2nd organic semiconductor into 10 mass% or more.
That is, if the mass ratio of the second organic semiconductor of the photoelectric conversion element of the present invention is 10% by mass or more, the light absorption rate can be increased while suppressing dark current.

Furthermore, 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 preferably 17% by mass or more. When the mass ratio of the second organic semiconductor is 17% by mass or more, the probability that the second organic semiconductors are in contact with each other is particularly high. Therefore, it is easy to cause the interaction by more remarkable stacking, and the dark current reduction effect when the third organic semiconductor is mixed becomes remarkable by that amount. The reason will be described with reference to FIG.

FIG. 3 is a schematic diagram of a mixed film of a binary configuration of a first organic semiconductor and a second organic semiconductor approximated to a rectangular parallelepiped.
The three-dimensional shape of the low-molecular organic compound is that when the position of each atom forming the organic compound is plotted in three-dimensional coordinates, the difference between the maximum value and the minimum value of each coordinate axis of X, Y, Z is the length and Can be approximated to a rectangular parallelepiped with one side as a side. When a rectangular parallelepiped of the same size is filled in a three-dimensional space, as shown in FIG. 3, two in the X-axis direction, two in the Y-axis direction, and two in the Z-axis direction with respect to each surface of a certain rectangular parallelepiped A A total of six cuboids B are adjacent on the surface. In addition to the rectangular parallelepiped A and its center of gravity, FIG. 3 shows six rectangular parallelepipeds B adjacent to the rectangular parallelepiped A in terms of surfaces and their centers of gravity. Here, it is assumed that the second organic semiconductor having a small mass ratio in the mixed film is a rectangular parallelepiped A. When all of the six rectangular parallelepipeds B are the first organic semiconductors, the second organic semiconductors are not in 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 are in contact with each other on the surface. That is, in the mixed film of the first organic semiconductor and the second organic semiconductor, when the mass ratio of the second organic semiconductor is 1/6, that is, approximately 17% by mass or more, the second organic semiconductors are mixed in the mixed film. It can be seen that the surfaces touch each other and can cause strong stacking interactions.

When a low molecular weight organic compound is approximated to a rectangular parallelepiped, a significant stacking interaction is likely to occur when contacting with a surface, but a small degree of contact with a side may cause an interaction due to stacking. Here, in addition to the six rectangular parallelepipeds that contact the rectangular parallelepiped A on the surface, the number of rectangular parallelepipeds that contact with the sides is 12 for a total of 18. That is, the condition in which the second organic semiconductors are in contact with each other at the face or side is estimated to be 1/18, that is, approximately 6% by mass or more in the mixed film. That is, when the amount is less than 6% by mass, the interaction between the second organic semiconductors is small, so that the dark current reduction effect due to the mixing of the third organic semiconductors is hardly exhibited.
As described above, the phenomenon of forming the energy spread of the state density of the HOMO level and the LUMO level due to the association between the second organic semiconductors occurs when the content of the second organic semiconductor is 6% by mass or more. What happened was supported not only from the description in Non-Patent Document 1, but also from geometric considerations.

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 effect of reducing the dark current by mixing the third organic semiconductor was supported by geometrical considerations.

As described above, in the present invention, the dark current reduction effect obtained 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 second. When the total amount of the three organic semiconductors is 100% by mass, the second organic semiconductor is obtained at 6% by mass or more. In addition, the dark current reducing effect is exhibited in the third organic semiconductor at 3% by mass or more, but such an effect is obtained until the second organic semiconductor has the same amount as the first organic semiconductor. Three organic semiconductors can be added until the same amount as 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
The first organic semiconductor ≧ the second organic semiconductor ≧ the third organic semiconductor.
The photoelectric conversion element which concerns on this invention reduces dark current by having 3 mass% or more of 3rd organic semiconductors. In order to further enhance this effect, it is preferable to select a third organic semiconductor having a high effect. The highly effective third organic semiconductor can be selected by using the solubility parameter.

The solubility parameter (hereinafter sometimes simply referred to as “SP value”) can be obtained by an experimentally obtained value or calculation. Experimentally, it can be determined experimentally by examining the solubility in various solvents as in Non-Patent Document 3. When the experimental value cannot be used, a method proposed by Fedors (Non-Patent Document 2) can be used as a theoretical estimation method of the SP value.

In the method proposed by Fedors, the SP value is obtained as follows. First, a molecular structure is divided into atoms or atomic groups constituting it. The divided unit is hereinafter referred to as a divided unit. From the table described in Non-Patent Document 2, the evaporation energy (ΔE _k ) (J / mol) and the molar volume (ΔV _k ) (cm ³ / mol) are determined for each divided unit.
Next, using these values, the value defined by Equation 1 below is called an SP value. This method is called group contribution method. The SP value is the square root of the cohesive energy density. In the present invention, the unit is (J / cm ³ ) ^1/2 .

However, this calculation method cannot be used for compounds having an excluded volume in the molecular structure. Examples of the compound having an excluded volume in the molecular structure include fullerene derivatives such as C60. This is because a fullerene derivative having a spherical molecular structure has an excluded volume inside the molecular structure, and thus it is difficult to determine the molecular volume. Similarly, calixarene derivatives and cyclodextrin derivatives are also difficult to calculate because they have an excluded volume inside the molecular structure.
Experimental values can be used for SP values of fullerene derivatives and the like that cannot be calculated by this calculation method. The experimental value of the SP value can be obtained according to Non-Patent Document 3. For C60, the SP value (σT) 20.0 obtained by Non-Patent Document 3 can be used.

Table 1 shows the calculated values and experimental values based on Non-Patent Document 2. In Table 1, [4] indicates a quoted value from Non-Patent Document 4, and [5] indicates a quoted value from Non-Patent Document 5.

FIG. 4 is a diagram showing the relationship between the experimental values and the calculated values in Table 1. The calculated value and the experimental value show linearity, and there is no big difference. That is, the SP value of Equation 1 shown in this specification may be handled in the same way as the experimental value.
In Table 1, the order of the experimental values and the calculated values may be reversed, such as pyridine and aniline, but when looking at FIG. 4 in which the above is plotted, the calculated values and the experimental values are close to each other as a whole. The order relationship does not change greatly.
In this specification, SP value of the first organic semiconductor is SP1, and SP value of the second organic semiconductor is

SP2 and the SP value of the third organic semiconductor are denoted as SP3.
These three SP values preferably satisfy the relationships of the following formulas (2) and (3).
| SP1-SP2 |> | SP2-SP3 | (2)
| SP1-SP3 |> | SP2-SP3 | (3)
By satisfying this relationship, the second organic semiconductor becomes easier to mix with the third organic semiconductor than to mix with the first organic semiconductor. Similarly, the third organic semiconductor is easily mixed with the second organic semiconductor. By mixing the second and third organic semiconductors, the spread of the state density energy of the HOMO level and the LUMO level due to the association between the second organic semiconductors is suppressed. Thereby, for example, the decrease in ΔE12 shown in FIG. 5 is suppressed, and the dark current is reduced.

More preferably, the SP values of the first to third organic semiconductors satisfy the relationships of the following formulas (4) to (6).
| SP1-SP2 | ≧ 2.5 (4)
| SP1-SP3 | ≧ 2.5 (5)
| SP2-SP3 | ≦ 2.5 (6)

By considering the combination of materials so as to have the above relationship, the second and third organic semiconductors are preferentially mixed rather than mixed with the first organic semiconductor.
More preferably, the solubility parameters of the second and third organic semiconductors satisfy the relationship of the following formula (7).
| SP2-SP3 | ≦ 1.0 (7)

When the first organic semiconductor is n-type, the second and third organic semiconductors are preferably p-type. On the other hand, when the first organic semiconductor is p-type, the second and third organic semiconductors are preferably n-type.

Such a relationship is preferable because a phase of the first organic semiconductor as the main component is easily formed and a phase in which the second and third organic semiconductors are mixed is easily formed. At that time, the first organic semiconductor as the main component becomes the main structure of the phase separation structure as the internal structure of the photoelectric conversion layer, and it is considered that high charge separation efficiency and high charge transport ability are easily realized. At this time, the generation of dark current due to thermal excitation is reduced by the mixed state of the second and third organic semiconductors. Therefore, a dark current is reduced and a photoelectric conversion element having high photoelectric conversion characteristics can be obtained.

As described above, it has been explained that the dark current is reduced by reducing N of the S / N ratio according to the present invention.

In order to improve the resolution of the photoelectric conversion element, it is preferable not only to lower N of the S / N ratio but also to improve S. For this purpose, when two types of photoelectric conversion elements are formed from the first, second, and third organic semiconductors, an element having an EQE peak on the long wavelength side is more preferable than an element having an EQE peak on the short wavelength side. However, it is preferable that the conversion efficiency (η) is high.
More specifically, when the first organic semiconductor is an n-type semiconductor and the second and third organic semiconductors are p-type semiconductors, a photoelectric conversion element constituted by the first organic semiconductor and the second organic semiconductor 1 and a photoelectric conversion element 2 composed of a first organic semiconductor and a third organic semiconductor are assumed.
And the spectrum which shows the value of the external quantum efficiency (EQE) with respect to the wavelength of each photoelectric conversion element is obtained. In the photoelectric conversion element 1, when the peak of the spectrum appears on the shorter wavelength side than the photoelectric conversion element 2, the conversion efficiency of the photoelectric conversion element 2 is preferably higher than the conversion efficiency of the photoelectric conversion element 1.

On the other hand, the photoelectric conversion element 1 and the photoelectric conversion element 2 are assumed as described above. In the photoelectric conversion element 1, when the spectrum peak appears on the longer wavelength side than the photoelectric conversion element 2, the photoelectric conversion element 1 and the photoelectric conversion element 2 preferably satisfy the following relational expressions (8) and (9). .
η ₁ > η ₂ (8)
| ΔEg | ≦ 0.052 eV (9)
η ₁ is the conversion efficiency of the photoelectric conversion element 1, and η ₂ is the conversion efficiency of the photoelectric conversion element 2. And the conversion efficiency of the photoelectric conversion element which has a 1st thru | or 3rd organic semiconductor is represented as (eta) ₃ .
ΔEg is an energy difference obtained from an EQE peak wavelength difference between the photoelectric conversion element 1 and the photoelectric conversion element 2. By satisfying the above relationship, energy can be transferred between combinations of p-type semiconductors and n-type semiconductors having different conversion efficiencies. Specifically, a part of energy can be transferred from the combination of the p-type semiconductor-n-type semiconductor of the photoelectric conversion element 2 to the combination of the p-type semiconductor-n-type semiconductor of the photoelectric conversion element 1, so that the conversion efficiency is high. The charge separation ability of the photoelectric conversion element 1 can be utilized. As a result, a certain improvement in conversion efficiency can be expected, and a relationship of η ₁ > η ₃ > η ₂ can be created.

In the sensitivity of the photoelectric conversion element, it is preferable that the light absorption characteristics and the conversion efficiency from light to electrons are high. This is because a device with high sensitivity cannot be obtained if the ability to separate charges is low even though the absorption characteristics are excellent. Therefore, the conversion efficiency (η) is represented by the following equation (10) as the probability of converting the absorbed photons into electrons.
Conversion efficiency (η) = external quantum yield / absorption rate of photoelectric conversion layer (10)

External quantum efficiency is also called quantum efficiency, and is the efficiency at which the total number of photons incident on an element changes to an electrical signal. A high EQE means a high sensitivity as a photoelectric conversion element. Hereinafter, the external quantum efficiency or quantum efficiency is also referred to as “EQE”.
The EQE is incident on a photoelectric conversion element applied with a predetermined voltage, for example, with an A light source (standard light source) or an Xe light source without being split or split, and is converted from photons to electrons out of all the incident photons. This is the efficiency obtained by measuring the current value with an ammeter instead of an electrical signal. At this time, the spectral sensitivity spectrum is obtained by measuring the EQE of each wavelength by separating the incident light.
The absorptance of the photoelectric conversion layer is the ratio of light absorption by the film disposed between the electrodes out of the total number of photons incident on the photoelectric conversion element.
The conversion efficiency (η) can be obtained, for example, as follows. The absorptance can be measured by forming a transparent pixel portion by using a transparent electrode such as IZO, which is an organic photoelectric conversion element on a transparent substrate, both of which is a lower electrode and an upper electrode. As a measuring device, it is possible to use Shimadzu Solidspec 3700. The photoelectric conversion current can be obtained by subtracting the dark current from the photocurrent that flows during light irradiation of this element, and the external quantum yield can be obtained by converting them into the number of electrons and dividing by the number of irradiated photons. As described above, the conversion efficiency (η) can be determined from the external quantum yield and the absorption rate of the photoelectric conversion layer.

The photoelectric conversion layer in the present invention is composed of at least first, second and third organic semiconductors, and there are at least two combinations of p-type and n-type ones. A photoelectric conversion element having a photoelectric conversion layer that can be configured by the two combinations has spectral sensitivity characteristics composed of respective absorption wavelength bands and conversion efficiency.

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. An absorption peak wavelength and an optical absorption edge can be obtained by preparing a thin film made of a single material of about 100 nm or less by vacuum deposition or the like by spin coating or by measuring an absorption spectrum of the film. The absorption peak wavelength here refers to the peak on the longest wavelength side as 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 a vibration structure) indicates the longest wavelength peak. On the other hand, the optical absorption edge corresponds to a band gap.

Since the absorption characteristics and the spectral characteristics of EQE correspond to each other, the photoelectric conversion element made of an organic semiconductor having a smaller band gap has a longer absorption peak wavelength and a corresponding EQE peak wavelength on the longer wavelength side. When the EQE peak wavelength is unclear, it can be determined by fabricating an element in which the concentration of the organic semiconductor is adjusted so as to increase the absorption rate. If the EQE peak wavelength cannot be confirmed at any concentration, the inflection point at which the EQE value tends to increase when viewed from the long wavelength side to the short wavelength side is used as an index as the spectral characteristics of the EQE. It can be considered as a similar index.

Between the first, second, and third organic semiconductors in the photoelectric conversion layer, an energy transfer process occurs until charge separation occurs from the organic semiconductor that is in an excited state by absorbing light. Excitation energy transfer is a phenomenon called mainly Förster type (fluorescence resonance) energy transfer. This occurs when there is an overlap between the emission spectrum of the light-absorbed organic semiconductor and the absorption spectrum of another organic semiconductor that receives the energy. The larger the overlap, the easier the energy moves. And energy tends to move from a high state to a low state. 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, the organic semiconductor serving as the energy acceptor preferably has a high absorption probability, that is, preferably has a large molar extinction coefficient. This energy transfer process is a phenomenon with a very small time constant as well as an electron transfer process.

The excitation energy of the photoexcited organic semiconductor moves toward the organic semiconductor with a small band gap. Then, charge separation occurs between a pair of p-type and n-type organic semiconductors including the p-type or n-type organic semiconductor to which the excitation energy has been transferred. It is a feature of the present invention that this combination is a combination of organic semiconductors having sensitivity on the long wavelength side. The combination is included in a photoelectric conversion element having a photoelectric conversion layer made of the first, second, and third organic semiconductors, so that photoexcitation energy absorbed at various wavelengths can be converted into p-type with high conversion efficiency. -It becomes possible to collect charge in n-type combinations and separate them. That is, a photoelectric conversion element having an EQE peak on the short wavelength side in an element provided with a photoelectric conversion layer that can be composed of one organic semiconductor of p-type and n-type among the first, second, and third organic semiconductors A photoelectric conversion element having a high sensitivity can be obtained because the conversion efficiency (η) of a photoelectric conversion element having an EQE peak on the longer wavelength side is high. As a result, the sensitivity of the photoelectric conversion element is improved over the entire wavelength region having absorption, and the S / N ratio is improved.

Each content of the p-type-n-type organic semiconductor having high conversion efficiency needs to function as an energy acceptor. Therefore, in any organic semiconductor, it is at least 3% or more, preferably 6% or more. As a receptor for energy transfer, the organic semiconductor has a molar extinction coefficient of at least 1000 mol L ⁻¹ cm ⁻¹ , more preferably 10000 mol L ⁻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 the molar extinction coefficient thereof is at least 1000 mol L ⁻¹ cm ⁻¹ or more. On the other hand, although C60 and the like have an absorption band in the visible range, the molar extinction coefficient is less than 1000 mol L ⁻¹ cm ⁻¹ and does not function effectively as an energy acceptor.

The first, second, and third organic semiconductors in the present invention are all low molecular organic compounds. Organic compounds are broadly classified into low molecules, oligomer molecules, and polymers, depending on the molecule. The polymer and oligomer molecules are defined by the International Pure Chemicals Association (IUPAC) Polymer Nomenclature Committee as follows.
Macromolecule, polymer molecule: A molecule having a large molecular mass and having a structure composed of many repetitions of units substantially or conceptually obtained from a molecule having a small relative molecular mass. .
Oligomer molecule: A molecule having a medium relative molecular mass and a structure composed of a small number of repetitions of units substantially or conceptually obtained from a molecule having a small relative molecular mass Say.

The first, second, and third organic semiconductors in the present invention are molecules that do not meet the definition of the polymer, polymer molecule, and oligomer molecule. That is, it is a molecule in which the number of repeating units is a small number of times, preferably 3 or less, more preferably 1.
For example, fullerene described later is a closed-shell hollow compound, but one closed-shell structure is regarded as one repeating unit. For example, C60 has a low molecular weight because the number of repetitions is one.
In addition, there are mainly synthetic polymers obtained by chemical synthesis and natural polymers existing in nature. Although natural polymers include monodisperse polymers, synthetic polymers generally have molecular weight dispersibility due to differences in repeating units. On the other hand, the organic semiconductor used in the present invention does not exist in nature and is a molecule obtained by synthesis, but does not have molecular weight dispersibility due to a difference in repeating units.

The presence or absence of such dispersibility makes an important difference when used for a photoelectric conversion layer in a photoelectric conversion element. When a polymer compound having dispersibility is used for the photoelectric conversion layer, the energy spread of the state density of the HOMO and LUMO levels of the compound contained in the photoelectric conversion layer increases, and the HOMO of the p-type semiconductor and the n-type semiconductor The energy barrier between LUMOs 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 has a low molecular organic semiconductor having no dispersibility due to the difference in the repeating unit and having a repeating unit of 3 or less, preferably 1, more preferably a molecular weight of 1500 or less having sublimation properties. The low molecular organic semiconductor is used.

The present invention is not limited to the oxidation potential and reduction potential relationship of the first organic semiconductor, the second organic semiconductor, and the third organic semiconductor. And LUMO level energy spread is suppressed. Therefore, although the dark current reduction effect appears in the present invention, it is preferable because the dark current reduction effect tends to be large when an oxidation potential and reduction potential relationship described below is satisfied.

FIG. 5 shows a preferred oxidation potential and reduction potential relationship with the third organic semiconductor when the first organic semiconductor is an n-type semiconductor and the second organic semiconductor is a p-type semiconductor in the present invention. The oxidation potential corresponds to the HOMO level of each organic semiconductor. The reduction potential corresponds to the LUMO level of each organic semiconductor. The oxidation-reduction potential is a potential energy difference between a molecule in a solution and an electrode, and is a physical property value of the molecule alone. In the configuration of FIG. 5, it is preferable that the relationship between the potentials satisfies the following expressions (11) and (12).

Eox2 ≦ Eox3 (11)
Ered1 ≧ Ered3 (12)
Eox2: oxidation potential of the second organic semiconductor Eox3: oxidation potential of the third organic semiconductor Ered1: reduction potential of the first organic semiconductor Ered3: reduction potential of the third organic semiconductor

When the above formulas (11) and (12) are satisfied, the LUMO of the first organic semiconductor with respect to ΔE ₁₂ formed at the LUMO level of the first organic semiconductor and the HOMO level of the second organic semiconductor. ΔE ₁₃ formed between the level and the HOMO level of the third organic semiconductor is equal to or larger. Similarly, with respect to Delta] E _12, Delta] E ₂₃ to form a third organic semiconductor LUMO level and the HOMO level of the second organic semiconductor is equal to or greater. As a result, the dark current generated between the first organic semiconductor and the second organic semiconductor is reduced in contribution to the dark current generated between the third organic semiconductor and the other organic semiconductor. Can do.

FIG. 6 shows a preferable oxidation potential and reduction potential relationship with the third organic semiconductor when the first organic semiconductor is a p-type semiconductor and the second organic semiconductor is an n-type semiconductor in the present invention. . In the configuration of FIG. 6, it is preferable that the relationship between the potentials satisfies the following expressions (13) and (14).

Eox1 ≦ Eox3 (13)
Ered2 ≧ Ered3 (14)
Eox1: oxidation potential of the first organic semiconductor Eox3: oxidation potential of the third organic semiconductor Ered2: reduction potential of the first organic semiconductor Ered3: reduction potential of the third organic semiconductor

The reason why such an oxidation potential / reduction potential relationship is preferable is that ΔE12 ≦ ΔE13, ΔE12 ≦ ΔE23, as in the case where the first organic semiconductor is an n-type semiconductor and the second organic semiconductor is a p-type semiconductor. This is because it is preferable.

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

(P-type semiconductor)
The p-type semiconductor used in the present invention is an electron donor organic semiconductor, which is mainly an organic compound 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, the thickness is preferably 500 nm to 650 nm. Thereby, the sensitivity of the blue region near 450 nm to 470 nm and the red region near 600 nm to 630 nm can be improved together with the green region, and the panchromatic property is improved.

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

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 substituted Alternatively, it represents an unsubstituted vinyl group, a substituted or unsubstituted amino group, or a cyano group.
n ₁ , n ₂ and n ₃ each independently represents an integer of 0 to 4.
X _{1 to} X _{3 each} represent a nitrogen atom, a sulfur atom, an oxygen atom, or a carbon atom that may have a substituent.
Ar ₁ and Ar ₂ are each independently selected from a substituted or unsubstituted aryl group or a substituted or unsubstituted heterocyclic group. When there are a plurality of Ar ₁ and Ar ₂ , they may be the same or different, and Ar ₁ and Ar ₂ may be bonded to each other to form a ring when X ₂ or X ₃ is a carbon atom.
Z ₁ is any of a halogen atom, a cyano group, a vinyl group substituted with a cyano group, a substituted or unsubstituted heteroaryl group, or a substituent represented by the following general formulas [1-1] to [1-9] Represents

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, a substituted or unsubstituted aryl group. Each independently selected from a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted vinyl group, a substituted or unsubstituted amino group, and a cyano group. * Represents a bonding position with a carbon atom.

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 hetero atom contained in the heterocyclic group is preferably nitrogen. X ₁ is preferably a sulfur atom or an oxygen atom. n ₁ is preferably 1 and n ₂ is preferably 0. When n ₂ is 0, Ar ₂ represents a single bond.

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 heterocyclic ring. Each independently selected from a group, a substituted or unsubstituted vinyl group, a substituted or unsubstituted amino group, and a cyano group. Two adjacent R _{20 to} R ₂₉ may be bonded to each other to form a ring.

More specifically, the general formula [2] can be represented 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, substituted or unsubstituted. Each 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. Examples include 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, and a 2-adamantyl group. 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. Examples include methoxy group, ethoxy group, n-propoxy group, isopropyloxy group, n-butoxy group, tert-butoxy group, sec-butoxy group, octoxy group and the like. 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. Examples include a phenyl group, a naphthyl group, an indenyl group, a biphenyl group, a terphenyl group, a fluorenyl group, an anthracenyl group, a pyrenyl group, a fluoranthenyl group, and a perylenyl group. 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, pyrazyl group, triazyl group, thienyl group, furanyl group, pyrrolyl group, oxazolyl group, oxadiazolyl group, thiazolyl group, thiadiazolyl group, carbazolyl group, acridinyl group, phenanthryl group, benzothiophenyl group, dibenzothiophenyl group Benzothiazolyl group, benzoazolyl group, benzopyrrolyl group and the like. The hetero atom contained in the heterocyclic group is preferably nitrogen.

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- Tolylamino group, N, N-ditolylamino group, N-methyl-N-phenylamino group, N, N-dianisoylamino group, N-mesityl-N-phenylamino group, N, N-dimesitylamino group, N-phenyl- N- (4-tert-butylphenyl) amino group, N-phenyl-N- (4-trifluoromethylphenyl) amino group and the like can be mentioned. The alkyl group and aryl group which the amino group has as a substituent are as shown in the above examples of the substituent.

In general formulas [1] and [2], general formulas [1-1] to [1-9], and general formulas [11] to [27], an alkyl group, an aryl group, a heterocyclic group, an amino group, a vinyl group, Examples of the substituent that the aryl group has include the following substituents. The substituent is an alkyl group having 1 to 4 carbon atoms such as methyl group, ethyl group, propyl group or butyl group, aralkyl group such as benzyl group, aryl group such as phenyl group or biphenyl group, pyridyl group, pyrrolyl group. Heterocyclic groups containing nitrogen atoms such as, dimethylamino group, diethylamino group, dibenzylamino group, diphenylamino group, amino group such as ditolylamino group, alkoxyl group such as methoxyl group, ethoxyl group, propoxyl group, phenoxyl group 1,3-indandionyl group, 5-fluoro-1,3-indandionyl group, 5,6-difluoro-1,3-indandionyl group, 5,6-dicyano-1,3-indandionyl group, 5-cyano-1 , 3-indandionyl group, cyclopenta [b] naphthalene-1,3 (2H) -dionyl group, Examples include cyclic ketone groups such as enalen-1,3 (2H) -dionyl group, 1,3-diphenyl-2,4,6 (1H, 3H, 5H) -pyrimidinetrionyl group, cyano group, and halogen atom. . The halogen atom is fluorine, chlorine, bromine, iodine or the like, and a fluorine atom is preferable.

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

In the 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, Each is independently selected from a cyclic group, a substituted or unsubstituted vinyl group, a substituted or unsubstituted amino group, and a cyano group. Two adjacent R _{391 to} R ₃₉₆ may be bonded to each other to form a ring. In particular, R ₃₉₄ and R ₃₉₅ are preferably bonded to form a ring.

The organic compound represented by the general formula [28] is a material having strong absorption at an absorption peak wavelength of 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 panchromic properties as described above.

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 are composed of a substituted or unsubstituted aryl group or a substituted or unsubstituted heterocyclic group, and two adjacent L _{1 to} L ₉ are adjacent to each other. Represents a ligand which may be bonded to each other to form a ring.

In the above general formulas [3] to [5], when M is iridium, a hexacoordinate complex is preferable. When M is platinum, vanadium, cobalt, gallium, or titanium, a tetracoordinate complex is preferable. This is because the stability of the complex is high by setting the coordination number.

Specific examples of the ligands L _{1 to} L _{9 for} the general formulas [3] to [5] are shown below.
The ligands L _{1 to} L ₉ are ligands in which a substituted or unsubstituted aryl group and a plurality of substituents selected from substituted or unsubstituted heterocyclic groups are bonded.
Examples of the aryl group constituting the ligand include phenyl group, naphthyl group, indenyl group, biphenyl group, terphenyl group, fluorenyl group, anthracenyl group, pyrenyl group, fluoranthenyl group, and perylenyl group. It is not limited.

As the heterocyclic group constituting the ligand, pyridyl group, pyrazyl group, triazyl group, thienyl group, furanyl group, pyrrolyl group, oxazolyl group, oxadiazolyl group, thiazolyl group, thiadiazolyl group, carbazolyl group, acridinyl group, phenanthroyl 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 that the ligands in the general formulas [3] to [5] have, that is, the substituents that the aryl group and heterocyclic group have have 1 to 4 carbon atoms such as methyl group, ethyl group, propyl group, and butyl group. Alkyl groups, aralkyl groups such as benzyl groups, aryl groups such as phenyl groups and biphenyl groups, heterocyclic groups containing nitrogen atoms such as pyridyl groups and pyrrolyl groups, dimethylamino groups, diethylamino groups, dibenzylamino groups, diphenylamino Group, amino group such as ditolylamino group, alkoxyl group such as methoxyl group, ethoxyl group, propoxyl group, phenoxyl group, 1,3-indandionyl group, 5, -fluoro-1,3-indandionyl group, 5,6- Difluoro-1,3-indandionyl group, 5,6-dicyano-1,3-indandionyl group, 5-cyano-1 3-indandionyl 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 groups, halogen atoms and the like. The halogen atom is fluorine, chlorine, bromine, iodine or the like, and a fluorine atom is preferable.
The ligand may have 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, preferred compounds among the p-type semiconductors represented by the general formulas [1] to [5] are exemplified.

(N-type semiconductor)
The n-type semiconductor used in the present invention is an electron acceptor organic semiconductor material, which is an organic compound having a property of easily accepting 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, and it is preferable to include fullerene or a fullerene derivative as an n-type semiconductor. Since the fullerene molecule or the fullerene derivative molecule is continuous in the first organic semiconductor 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 fullerene or fullerene derivatives 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 nanotubes, and the like. It is done.
The fullerene derivative is a fullerene having a substituent. Examples of this substituent include an alkyl group, an aryl group, and a heterocyclic group.

(Near-infrared absorbing material)
In a ternary photoelectric conversion element, the sensitivity region can be made near infrared by using a compound having an absorption band in the near infrared region. In that case, as the first, second, or third organic semiconductor, a compound having an absorption band in the near infrared region may be included. The near-infrared region generally refers to a wavelength band of 800 to 2500 nm, but the following compounds are known as absorbing materials using organic materials.

Since a material having absorption in the near infrared region has a small band gap, ΔE shown in FIG. 1 tends to be small and dark current tends to be large. For this reason, in a photoelectric conversion element including a material having absorption in the near infrared, it is preferable to apply the SP value relationship described above between the organic semiconductors used to reduce dark current.

The photoelectric conversion layer according to the present invention preferably does not emit light. The term “non-emission” means that the emission quantum efficiency is 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). In the photoelectric conversion layer, if the emission quantum efficiency exceeds 1%, it is not preferable because it affects sensing performance or imaging performance when applied to a sensor or an imaging device. Luminescence quantum yield is the ratio of photons emitted by luminescence to absorbed photons. Luminescence quantum yield is an absolute PL quantum yield measurement device designed to produce a thin film of the same material composition as the photoelectric conversion layer on a substrate such as quartz glass as a sample and to determine the value of the thin film. Can be measured using. For example, “C9920-02” manufactured by Hamamatsu Photonics can be used as an absolute quantum yield measuring apparatus.

(Photoelectric conversion element)
FIG. 7 is a cross-sectional view schematically showing a configuration of one 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 disposed between the anode 5 and the cathode 4, and the photoelectric conversion layer 1 However, it has the specific organic semiconductor composition described above. The photoelectric conversion element 10 of this embodiment is an example provided with the second organic compound layer 2 and the 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 disposed between the anode 5 and the cathode 4. The anode 5 is an electrode that collects electrons generated in the first photoelectric conversion layer 1 disposed between the anode 5 and the cathode 4. The cathode 4 is also called a hole collecting electrode, and the anode 5 is also called an electron collecting electrode. Either the cathode 4 or the anode 5 may be disposed on the substrate side. The electrode arranged on the substrate side is also called a lower electrode.
The photoelectric conversion element of the present embodiment may be an element used by applying a voltage between the cathode 4 and the anode 5.

The constituent material of the cathode 4 is not particularly limited as long as it is highly conductive and transparent. Specific examples include metals, metal oxides, metal nitrides, metal borides, organic conductive compounds, and a mixture of a plurality of these. More specifically, conductive metal oxides such as tin oxide (ATO, FTO) doped with antimony or fluorine, tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), zinc indium oxide, gold, Metal materials such as silver, chromium, nickel, titanium, tungsten, and 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 laminate with a material, an inorganic conductive material 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.

Specifically, the constituent material of the anode 5 is ITO, indium zinc oxide, SnO ₂ , ATO (antimony-doped tin oxide), ZnO, AZO (Al-doped zinc oxide), GZO (gallium-doped zinc oxide), TiO _2. , FTO (fluorine-doped tin oxide) and the like.

The method for forming the electrode can be appropriately selected in consideration of 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 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, the electrode 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 (such as a sol-gel method), or an ITO dispersion. Furthermore, 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 can be used, and annealing treatment, UV-ozone treatment, plasma treatment, and the like can be further performed.

In the present embodiment, the second organic compound layer 2 may be composed of a single layer, a plurality of layers, or a mixed layer having a plurality of types of materials. In the photoelectric conversion element 10 of FIG. 7, the second organic compound layer 2 has a role of transporting holes transferred from the photoelectric conversion layer 1 to the hole collecting electrode 4. In addition, the second organic compound layer 2 suppresses electrons from moving from the hole collection electrode 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 for 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.

In the present embodiment, the third organic compound layer 3 has a role of transporting electrons moved from the photoelectric conversion layer 1 to the anode 5. Moreover, since the 3rd organic compound layer 3 is a hole blocking layer which suppresses a hole flowing into the photoelectric converting layer 1 from the anode 5, it is preferable that it is a layer with high ionization potential. The third organic compound layer 3 may be composed of a single layer, a plurality of layers, or a mixed layer having a plurality of types of materials.

In the present invention, the layer disposed between the anode 5 and the cathode 4 is limited to the three types of layers described above (the photoelectric conversion layer 1, the second organic compound layer 2, and the third organic compound layer 3). It is not something. An intervening layer can be further provided between at least one of the second organic compound layer 2 and the cathode 4 and between the third organic compound layer 3 and the anode 5. This intervening layer is provided for the purpose of improving the injection efficiency of the charge 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.

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

In the photoelectric conversion element 10 of FIG. 7, an inorganic protective layer 7 is disposed 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 oxide 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 permeability is 10 ⁻⁵ g / m ² · day or less. The 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, the thinner one is preferable, and the thickness is particularly preferably 1 μm or less. The reason why the inorganic protective layer 7 is preferably thin is that, when elements are arranged two-dimensionally and used as an area sensor, there is an effect of reducing color mixing as the distance from the photoelectric conversion layer to the color filter 8 can be shortened.

7, the color filter 8 is disposed on the inorganic protective layer 7 in the photoelectric conversion element 10 of FIG. Examples of the color filter 8 include a color filter that transmits red light of visible light. In the present invention, the color filter 8 may be provided for one photoelectric conversion element or for a plurality of photoelectric conversion elements. Further, when the color filters 8 are arranged, for example, a Bayer arrangement may be formed with adjacent photoelectric conversion elements.

In the photoelectric conversion element 10 of FIG. 7, an optical member may be disposed on the color filter 8, and in FIG. 7, a micro lens 9 is disposed as the optical member. The microlens 9 plays a role of collecting incident light onto the photoelectric conversion layer 1 that is a photoelectric conversion unit. In the present invention, the number of microlenses 9 may be one for each photoelectric conversion element or one for a plurality of photoelectric conversion elements. In the present invention, it is preferable to provide one microlens 9 per photoelectric conversion element.

In FIG. 7, the microlens 9 is arranged on the cathode 4 side to be the light incident side. However, the present invention is not limited to this, and the inorganic protective layer 7, the color filter 8, A micro lens 9 may be provided. In that case, the preferred electrode materials for the cathode 4 and anode 5 shown above are reversed.

Although not shown in FIG. 7, the photoelectric conversion element of the present invention may have a substrate. Examples of the substrate include a silicon substrate, a glass substrate, and a flexible substrate. Which of the anode 5 and the cathode 4 is arranged on the substrate side is not limited, and may be the order of anode 5 / photoelectric conversion layer 1 / cathode 4 on the substrate, or may be cathode 4 / photoelectric conversion layer 1 / anode 5. .

The above is the main configuration of the photoelectric conversion element. Actually, the photoelectric conversion element is preferably annealed after fabrication, but the present invention is not particularly limited by the annealing conditions.

The photoelectric conversion element which concerns on this invention can be made into the photoelectric conversion element corresponding to the light of a different color by selecting the organic semiconductor used for the photoelectric converting layer 1. FIG. “Corresponding to different colors” means that the wavelength region of the light photoelectrically converted by the photoelectric conversion layer 1 changes.
Further, by stacking a plurality of photoelectric conversion elements corresponding to different colors, a photoelectric conversion device that does not require the color filter 8 can be obtained.

FIG. 8 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 is further connected to the amplification transistor 23. The pixel circuit includes an amplification transistor (SF MOS) 23 that amplifies a signal from the photoelectric conversion element 10, a selection transistor (SEL MOS) 24 that selects a pixel, and a reset transistor (RES MOS) 22 that resets the node B.

With such a configuration, the amplification transistor 23 can output a signal generated by the photoelectric conversion element 10. The photoelectric conversion element 10 and the amplification transistor 23 may be short-circuited. As shown in FIG. 8, a transfer transistor 25 may be arranged as a switch in the electrical path between the photoelectric conversion element 10 and the amplification transistor 23. The transfer transistor 25 is controlled to be switched on and off by a switching control pulse pTX. In the pixel configuration of FIG. 8, a node B representing electrical connection between the photoelectric conversion element 10 and the amplification transistor 23 is shown. Node B is configured to be electrically floating. When the node B is electrically floating, the voltage of the node B can be changed according to the electric charge generated in the photoelectric conversion element 10. Therefore, a signal corresponding to the charge generated in the photoelectric conversion element 10 can be input to the amplification transistor 23.

8 includes 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 to be switched on and off by a reset control pulse pRES. When the reset transistor 22 is turned on, a reset voltage is supplied to the node B. The charge storage unit 15 is a region for storing charges generated in the photoelectric conversion element 10 and is configured by forming a P-type region and an N-type region in a 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 constitute 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. A signal from the pixel 20 output to the output line 28 is input to the column circuit 27. In FIG. 8, 29 is a wiring.

(Photoelectric conversion device)
FIG. 9 is a plan view schematically showing a configuration of one 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. An area other than the imaging area 31 is a circuit area 36.

The imaging region 31 is configured by arranging a plurality of pixels in a two-dimensional manner. As the structure of the pixel, the structure of the pixel 20 shown in FIG. 7 can be used as appropriate. In addition, the pixel 20 may be configured by stacking the photoelectric conversion elements 10 of the present invention described above. The readout circuit 33 includes, for example, a column amplifier, a CDS circuit, an addition circuit, and the like, and with respect to a signal read out from a pixel in a row selected by the vertical scanning circuit 32 via a vertical signal line (28 in FIG. 8). Amplification, addition, etc. The column amplifier, the CDS circuit, the addition circuit, and the like are arranged for each pixel column or a plurality of pixel columns, 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 only 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 the other with the imaging region 31 in between in order to form two systems of output paths. However, three or more output paths may be provided. Signals output from the output amplifiers are synthesized as image signals by the signal processing unit 37.

(Optical area sensor)
The photoelectric conversion element of the present invention can be used as a constituent member of an optical area sensor by two-dimensionally arranging it in the in-plane direction. The optical area sensor has a plurality of photoelectric conversion elements arranged two-dimensionally in the in-plane direction. In such a configuration, information representing the light intensity distribution in a predetermined light receiving area can be obtained by individually outputting signals based on charges referred to by a plurality of photoelectric conversion elements. In addition, you may replace the photoelectric conversion element contained in this optical area sensor with the photoelectric conversion apparatus mentioned above.

(Image sensor)
Furthermore, the photoelectric conversion element of the present invention can be used as a constituent member of an imaging element. The imaging device includes a plurality of pixels (light receiving pixels). The plurality of pixels are arranged in a matrix including a plurality of rows and a plurality of columns. In such a configuration, an image signal can be obtained by outputting a signal from each pixel as one pixel signal. In the imaging element, 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 reading circuit includes, for example, a transistor that outputs a signal based on electric charges 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 sensor, an image can be obtained by collecting information acquired by each pixel in the sensor unit.

The image sensor 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 supports light of a specific wavelength, it is preferable to have a color filter that transmits a wavelength region that can be handled by the photoelectric conversion element. One color filter may be provided for each light receiving pixel, or one color filter may be provided for a plurality of light receiving pixels. The optical filter included in the imaging element is not limited to a color filter, and other low-pass filters that transmit wavelengths of infrared rays or more, UV cut filters that transmit wavelengths of ultraviolet rays or less, and long-pass filters can be used.

The imaging element 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 imaging element is a lens that condenses light from the outside onto a photoelectric conversion layer included in the photoelectric conversion element included in the imaging element. One microlens may be provided for each light receiving pixel, or one microlens may be provided for a plurality of light receiving pixels. When a plurality of light receiving pixels are provided, it is preferable that one microlens is provided for a plurality (two or more predetermined numbers) of light receiving pixels.

(Imaging device)
The photoelectric conversion element according to the present invention can be used in an imaging apparatus. The imaging apparatus includes an imaging optical unit having a plurality of lenses and an imaging element that receives light that has passed through the imaging optical unit, and uses the photoelectric conversion element of the present invention as the imaging element. Further, the imaging device may be an imaging device having a joint portion that can be joined to the imaging optical unit and an imaging element. More specifically, the imaging device here refers to a digital camera, a digital still camera, or the like. The imaging device may be added to the mobile terminal. Although a portable terminal is not specifically limited, A smart phone, a tablet terminal, etc. may be sufficient.

Further, the imaging device may further include a receiving unit that receives 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 apparatus, the start of imaging, and the end of imaging. The imaging device may further include a transmission unit that transmits an image acquired by imaging to the outside. As described above, the imaging device can be used as a network camera by including the reception unit and the transmission unit.

In addition, the imaging apparatus may further include a receiving unit that performs an external signal. 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. The imaging device may further include a transmission unit that transmits the captured image to the outside. Thus, having a receiving unit and a transmitting unit can be used as a network camera.

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

Evaluation of electrochemical characteristics such as oxidation potential of the compounds used in the examples can be performed by cyclic voltammetry (CV).
A CV measurement sample was prepared by dissolving about 1 mg of each compound in 10 mL of orthodichlorobenzene solution of 0.1 M tetrabutylammonium perchlorate and performing a deaeration treatment with nitrogen. The three-electrode method is used for the measurement. Each electrode is composed of a nonaqueous solvent type Ag / Ag ⁺ reference electrode, a platinum counter electrode having a diameter of 0.5 mm and a length of 5 cm, and a glassy carbon working electrode having an inner diameter of 3 mm (both -ASS Co., Ltd. was used. A model 660C manufactured by ALS Co., Ltd. and an electrochemical analyzer were used as the apparatus, and the measurement insertion speed was 0.1 V / s. An example of the waveform at this time is shown in FIG. By changing the bias polarity, the oxidation potential (Eox) and the reduction potential (Ered) can be measured by the same method. Table 2 shows the oxidation potential and reduction potential of each material.

On the Si substrate, a cathode, an electron blocking layer (EBL), a photoelectric conversion layer, a hole blocking layer (HBL), and an anode were sequentially formed to produce a photoelectric conversion element. In the electron blocking layer, the photoelectric conversion layer, and the hole blocking layer, the above-described compounds 1 to 14 were used in combinations shown in Table 3. The production procedure is as follows.

First, a Si substrate was prepared in which a wiring layer and an insulating layer were sequentially stacked, and contact holes were formed from the wiring layer at locations corresponding to the respective pixels so as to be conductive by providing an opening in the insulating layer. The contact hole is drawn 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) of 3 mm ² . At this time, the film thickness of the IZO electrode was 100 nm. On this IZO substrate, an electron blocking layer, a photoelectric conversion layer, and a hole blocking layer shown in Table 2 having the following constitution were sequentially vacuum-deposited, 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 for about 1 hour on a 170 ° C. hot plate with the sealing surface facing upward in order to stabilize the element characteristics.

When the value of the flowing current was confirmed by applying a voltage of 5 V to the obtained photoelectric conversion element, the ratio of (current in the light place) / (current in the dark place) = 10 times or more in any element. It confirmed that it functioned as a photoelectric conversion element. Next, the photoelectric conversion element was held in a constant temperature bath at 60 ° C., and a probe connected to a semiconductor parameter analyzer (Agilent “4155C”) was brought into contact with the electrode to measure dark current.

Table 3 shows compounds used for the electron blocking layer, the photoelectric conversion layer, and the hole blocking layer of the photoelectric conversion element, and their compositions. In the table below, “% by mass” is the total 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 in the binary configuration. The content of each organic semiconductor when the total organic semiconductor is 100% by mass is shown. In the description of the following table, “content” means the content of each organic semiconductor when the ternary configuration or the binary configuration is 100 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.

Hereinafter, description will be made based on the table for extracting the comparative examples and comparative examples.

In Comparative Example 1 shown in Table 4, the photoelectric conversion layer is composed of two materials of Compound 2 as the first organic semiconductor and Compound 3 as the second organic semiconductor. In Comparative Examples 2 and 3 and Examples 1 to 4, the photoelectric conversion layer is 25% by mass, which is the same as that of Comparative Example 1 in which the compound 2 as the first organic semiconductor and the content as the second organic semiconductor are the same. In addition to a certain compound 3, it is constituted by containing a compound 4 as a third organic semiconductor. Here, the relative dark current in Comparative Examples 2 and 3 and Examples 1 to 4 is the ratio of dark current to Comparative Example 1. From Table 4, Examples 1 to 4 in which the content of the third organic semiconductor is 3% by mass or more have a lower dark current than that of Comparative Example 1 that does not have the 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 in which the mass ratio is 0.12 or more are compared with Comparative Example 1 that does not have the third organic semiconductor. The dark current decreased.

In Comparative Examples 1, 4, 5, 6, and 7 shown in Table 5, the photoelectric conversion layer is composed of two materials, compound 2 as the first organic semiconductor and compound 3 as the second organic semiconductor. . In Examples 1, 5, 6, 7, and Comparative Example 8, the photoelectric conversion layer has Comparative Example 1, 4, 5, 6, 7 in which the photoelectric conversion layer is Compound 2 as the first organic semiconductor and the second organic semiconductor. In addition to compound 3 which is the same as the above, 3% by mass of compound 4 as a third organic semiconductor is contained. Here, the relative dark current in Examples 1, 5, 6, 7, and Comparative Example 8 is the ratio of dark current to Comparative Examples 1, 4, 5, 6, and 7, respectively. From Table 5, Examples 1, 5, 6, and 7 in which the content of the second organic semiconductor is larger than 6% by mass are compared with Comparative Examples 1, 4, 5, and 6 that do not have the 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. In addition, it can be seen from the relative dark currents of Examples 1, 5, and 6 that 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 large and preferable. . In addition, it can be seen from the relative dark currents of Examples 1 and 5 that 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 large, which is more preferable.

In Comparative Example 1 shown in Table 6, the photoelectric conversion layer is composed of two materials of Compound 2 as the first organic semiconductor and Compound 3 as the second organic semiconductor. In Examples 3, 8 to 11, the photoelectric conversion layer is added to Compound 2 as the first organic semiconductor and Compound 3 whose content as the second organic semiconductor is 25% by mass as in Comparative Example 1, It is comprised by containing the compound shown in Table 6 as a 3rd organic semiconductor, respectively. In the photoelectric conversion element shown in Table 6, compound 2 is an n-type semiconductor, and compounds 3 to 8 are p-type semiconductors. Here, the relative dark current in Examples 3 and 8 to 11 is the ratio of the dark current to Comparative Example 1. From Table 6, the expression expressed using the oxidation potential Eox2 of the second organic semiconductor, the oxidation potential Eox3 of the third organic semiconductor, the reduction potential Ered1 of the first organic semiconductor, and the reduction potential Ered3 of the third organic semiconductor. In (15) and (16), ΔEox and ΔEred are 0 or more.
ΔEox = (Eox3) − (Eox2) (15)
ΔEred = (Ered1) − (Ered3) (16)
That is, it can be seen that Examples 3, 8 to 10 satisfying the following (11) and (12) have a large dark current reducing effect due to the third organic semiconductor inclusion.
Eox2 ≦ Eox3 (11)
Ered1 ≧ Ered3 (12)

Here, in Example 11, ΔEox is negative, and the dark current reduction effect by the third organic semiconductor inclusion of Example 11 is compared with the dark current reduction effects of Examples 3 and 8 to 10 in which ΔEox is 0 or more. I understand that it is small.

On the other hand, in Comparative Example 9, the photoelectric conversion layer is composed of two materials of the compound 2 as the first organic semiconductor and the compound 7 as the second organic semiconductor. In Example 12, the photoelectric conversion layer has a third organic compound in addition to the compound 2 as the first organic semiconductor and the compound 7 whose content as the second organic semiconductor is 25% by mass as in Comparative Example 1. It is comprised by containing the compound 3 as a semiconductor. Here, the relative dark current in Example 12 is the ratio of dark current to Comparative Example 9.

From the above results, in Examples 11 and 12 in which ΔEox is negative, the dark current reduction effect due to the mixing of the third organic semiconductor is recognized, but rather than Examples 3, 8 to 10 in which ΔEox is 0 or more, It can be seen that the dark current reduction effect is small.

In Comparative Example 10 shown in Table 7, the photoelectric conversion layer is composed of two materials of Compound 7 as the first organic semiconductor and Compound 2 as the second organic semiconductor. In Example 13, the photoelectric conversion layer has a third organic compound in addition to the compound 7 as the first organic semiconductor and the compound 2 whose content as the second organic semiconductor is 40% by mass as in Comparative Example 1. It is comprised by containing the compound 3 as a semiconductor. In Examples 1 to 12 and Comparative Examples 1 to 9, the first organic semiconductor is an n-type semiconductor and the second organic semiconductor is a p-type semiconductor, whereas Comparative Examples 10 and 13 are the first The organic semiconductor is a p-type semiconductor, and the second organic semiconductor is an n-type organic semiconductor. Here, the relative dark current in Example 13 is the ratio of dark current to Comparative Example 10.

From the above results, even when the first organic semiconductor is a p-type semiconductor and the second organic semiconductor is an n-type semiconductor, the dark current reducing effect by containing the third organic semiconductor was shown.

Table 8 shows that the third organic material can be used regardless of the type of compound even if the compounds constituting the electron blocking layer, the photoelectric conversion layer, and the hole blocking layer are changed to different compounds. It is confirmed that the dark current reduction effect by using a semiconductor is manifested.

The relative dark current in Examples 3 and 14 to 20 in Table 8 is the ratio of dark current to Comparative Examples 1 and 13 to 18, respectively. The element configuration of Examples 14 to 20 is any one of the electron blocking layer, the hole blocking layer, the first organic semiconductor, the second organic semiconductor, and the third organic semiconductor with respect to the element configuration of Example 3. One or two elements are changed to different compounds. From Table 8, Example 14 thru | or 20 has confirmed the dark current reduction effect by mixing of the 3rd organic semiconductor.

Examples 20, 21, and 22 and Comparative Examples 19 and 22 are device configurations in which the contents of the compound 13 that is the second organic semiconductor and the compound 14 that is the third organic semiconductor are changed. The relative dark currents of Examples 20 and 21 and Comparative Example 19 are the ratio of dark current to that of Comparative Example 18. The relative dark currents of Example 22 and Comparative Example 22 are ratios of dark currents to Comparative Examples 20 and 21, respectively. In Examples 20, 21, and 22 where 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, the dark current is reduced by mixing the third organic semiconductor. The effect was confirmed. On the other hand, Comparative Example 19 in which the content of the second organic semiconductor is 6% by mass or more and the content of the third organic semiconductor does not satisfy 3% by mass or more is an effect of reducing dark current by mixing the third organic semiconductor. Could not be confirmed. Further, in Comparative Example 22 in which the content of the third organic semiconductor is 3% by mass or more and the content of the second organic semiconductor does not satisfy 6% by mass or more, the dark current reduction effect by mixing the third organic semiconductor is Could not be confirmed.

(Verification experiment)
In order to analyze the cause of the dark current, FIG. 11 shows the results of measuring the temperature dependence of the dark current of the photoelectric conversion element of Comparative Example 1 and performing an Arrhenius plot. As shown in FIG. 11, the inclination increases from about 60 ° C. (T / 1000 = 3.0) toward the high temperature side (the left side of the horizontal axis in FIG. 11). The activation energy was determined from this slope according to the following equation (17).

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

For the photoelectric conversion elements of Comparative Examples 11 and 12 and Example 8, the activation energy was determined in the same manner as in Comparative Example 1. Table 9 shows the activity of the photoelectric conversion layer in each photoelectric conversion element, and the photoelectric conversion layer in which the compound 3 is 25% by mass is normalized by the value of the binary conversion photoelectric conversion element (Comparative Example 1). Energy and dark current are summarized.

From Table 9, it can be seen that in the element having a binary 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 for this is that as the content of the second organic semiconductor increases, the second organic semiconductors associate with each other and the energy distribution of the state density of the HOMO level widens, so that the activation energy decreases, and the dark current This is thought to increase.

On the other hand, in the photoelectric conversion element of Example 8, since the third organic semiconductor is mixed, the content of the p-type semiconductor (total amount of the second organic semiconductor and the third organic semiconductor) is a comparative example. Despite being greater than 1, the activation energy is increased and the dark current is reduced. This is considered to be because when the third organic semiconductor is mixed in addition to the first organic semiconductor and the second organic semiconductor, the second organic semiconductors can be associated with each other and the interaction due to stacking can be suppressed. . As a result, it is considered that the energy spread of the state density of the HOMO level can be suppressed.

In Comparative Example 1, the photoelectric conversion layer is composed of two materials of Compound 2 as the first organic semiconductor and Compound 3 as the second organic semiconductor. In Example 3, the photoelectric conversion layer has a third organic compound in addition to the compound 2 as the first organic semiconductor and the compound 3 whose content as the second organic semiconductor is 25% by mass as in Comparative Example 1. It is comprised by containing the compound 4 as a semiconductor. In Example 3, the first organic semiconductor is an n-type semiconductor, the second organic semiconductor is a p-type semiconductor, and the third organic semiconductor is a p-type semiconductor. In Example 23, in addition to the compound 2 in which the photoelectric conversion layer is the first organic semiconductor and the compound 3 in which the content as the second organic semiconductor is 25% by mass as in Comparative Example 1, the third organic semiconductor is used. It is comprised by containing the compound 10 as. In Example 23, the first organic semiconductor is an n-type semiconductor, the second organic semiconductor is a p-type semiconductor, and the third organic semiconductor is an n-type semiconductor.

The relative dark current, which is the ratio of dark current to Comparative Example 1, was smaller in Example 3 than in Example 23. From this, it can be seen that when the first organic semiconductor is an n-type semiconductor and the second organic semiconductor is a p-type semiconductor, the third organic semiconductor is preferably a p-type semiconductor.

In Comparative Example 10, the photoelectric conversion layer is composed of two materials of Compound 7 as the first organic semiconductor and Compound 2 as the second organic semiconductor. In Example 13, the photoelectric conversion layer has a third organic compound in addition to the compound 7 as the first organic semiconductor and the compound 2 whose content as the second organic semiconductor is 40% by mass as in Comparative Example 1. It is comprised by containing the compound 3 as a semiconductor. In Example 13, the first organic semiconductor is a p-type semiconductor, the second organic semiconductor is an n-type semiconductor, and the third organic semiconductor is a p-type semiconductor. In Example 24, in addition to the compound 2 having a photoelectric conversion layer as the first organic semiconductor and the compound 3 having the same content of 40% by mass as the comparative example 1 as the second organic semiconductor, the third organic semiconductor is used. It is comprised by containing the compound 10 as. In Example 24, the first organic semiconductor is a p-type semiconductor, the second organic semiconductor is an n-type semiconductor, and the third organic semiconductor is an n-type semiconductor.

The relative dark current, which is the ratio of dark current to Comparative Example 10, was smaller in Example 24 than in Example 13. From this, it can be seen that when the first organic semiconductor is a p-type semiconductor and the second organic semiconductor is an n-type semiconductor, the third organic semiconductor is preferably an n-type semiconductor.

(Conversion efficiency evaluation results)
In order to obtain a high S / N ratio, the photoelectric conversion efficiency measurement and evaluation results, which preferably have high photoelectric conversion efficiency, are described below. First, in order to evaluate the conversion efficiency for each combination of p-type and n-type in advance, a photoelectric conversion element having a photoelectric conversion layer containing 25% of each p-type material is excluded from the photoelectric conversion layer. Table 1 shows the results of manufacturing and evaluation performed in the same manner as described above. The conversion efficiency is
Conversion efficiency (η) = external quantum yield (EQE) / a value calculated after separately obtaining the external quantum efficiency and the absorption rate of the photoelectric conversion layer from the relationship of the absorption rate of the photoelectric conversion layer. The following table shows the EQE peak wavelength and the conversion efficiency of a photoelectric conversion element using a combination of p-type and n-type organic semiconductors. The EQE peak wavelength is obtained by measuring the current at the time of irradiating the light of each wavelength and the non-irradiation with the spectral sensitivity light source and the semiconductor parameter analyzer (Agilent 4155C) for the element placed in the dark place. Asked. The photocurrent was converted to the number of electrons and divided by the number of incident photons to obtain EQE. Thereby, EQE of each wavelength was measured to obtain spectral sensitivity characteristics, and the sensitivity peak wavelength on the longest wavelength side was obtained. The band gap is also shown as an index of excitation energy of each material. This band gap was calculated from the absorption spectrum measurement of each 100% film formed by vacuum deposition with a film thickness of about 100 nm.
The conversion efficiency of the photoelectric conversion layer can be estimated from the efficiency of the photoelectric conversion element having the photoelectric conversion layer.

The conversion efficiency (η) in Table 11 was evaluated as follows as the conversion efficiency of the binary element at a drive voltage of 5V.
A: η ≧ 80
B: 80> η ≧ 60
C: η <60

In the above element configuration, the mass percentage concentration of the second organic semiconductor is 25%, but this is an index for comparing each combination, and the weight ratio of the second organic semiconductor is limited to 25%. I can't. For example, the present inventors have confirmed that the above conversion efficiency is almost constant until the concentration of the second organic semiconductor is about 15 to 50%. Based on such a concentration range, the maximum conversion efficiency is confirmed. It is sufficient that the value is determined.
From the above results, it can be seen that the use of fullerene C60 of Compound 2 as an n-type organic semiconductor does not affect the conversion efficiency of photoelectric conversion. This indicates that the absorption transition in the visible part of C60 is a forbidden transition and the molar extinction coefficient is less than 1000 mol L ⁻¹ cm ⁻¹ , and does not function effectively as an energy acceptor.

Based on the above, a photoelectric conversion element in which the first, second, and third organic semiconductors forming the first organic semiconductor layer described in Table 2 are configured as follows is manufactured, and the conversion efficiency of the element is determined. evaluated.
Table 12 shows the relationship between the configuration of the photoelectric conversion layer of the photoelectric conversion element of the present invention and the conversion efficiency, based on the results of Table 11, in order to obtain a photoelectric conversion element with a better S / N ratio. In addition, the element of the Example in the following table | surface and the comparative example produces parts other than a photoelectric converting layer with the method similar to another Example. The conversion efficiency was a value of 500 nm close to the sensitivity peak in Table 11, and the effect of the present invention was verified.

Explain the above results. As in Examples 25 to 50, an element having an EQE peak on the long wavelength side and a p-type / n-type combination having high conversion efficiency showed high conversion efficiency. Compared with the conversion efficiency of the

organic semiconductors

2 and 3 only in Examples 25 to 30, the conversion efficiency of the element including the combination of the

organic semiconductors

2 and 4 having an EQE peak having a higher conversion efficiency on the longer wavelength side is higher. The result was high. In particular, the device including any combination of the organic semiconductor 2 and the

organic semiconductors

6, 13, 15, 16, and 18 showed particularly high conversion efficiency.

On the other hand, an element composed of a combination of the organic semiconductor number 2 and the p-type semiconductor-n-type semiconductor combined among the

organic semiconductors

4, 5, and 14 has a low conversion efficiency as in Comparative Examples 24-28 (

organic semiconductor

4 , 5, and 14 are shown in italics).

In Comparative Example 23, the concentration of the organic semiconductor 4 out of the organic semiconductor 2 and the organic semiconductor 4 that are a combination of the p-type semiconductor and the n-type semiconductor constituting the side that accepts the excitation energy is effective. The conversion efficiency did not increase because the excitation energy could not be collected.

In Examples 25 to 50 and Comparative Examples 23 to 28, the dark current reduction effect of about 0.1 to 0.6 times was observed with the inclusion of the third organic semiconductor as mentioned in the previous examples. It was. In addition, Example 3 and Example 25, Example 8 and Example 40, Example 20 and Example 43 are the elements of the same photoelectric converting layer, respectively.

Therefore, a photoelectric conversion element having an EQE peak on the short wavelength side in an element having a photoelectric conversion layer that can be composed of one of the p-type and n-type organic semiconductors among the first, second, and third organic semiconductors. Since the conversion efficiency (η) of the photoelectric conversion element having an EQE peak on the longer wavelength side is high, a photoelectric conversion element with high sensitivity can be obtained. And dark current also falls. Thereby, a photoelectric conversion element having a high S / N ratio is obtained.

On the other hand, the case where the conversion efficiency of the element having the EQE peak on the short wavelength side is higher than that of the element having the EQE peak on the long wavelength side is as follows.

Table 13 shows the EQE peak wavelength and the conversion efficiency (η) of a photoelectric conversion element by a combination of a pair of p-type semiconductor and n-type semiconductor. These are shown as characteristics of a binary element configuration of a combination of a p-type semiconductor and an n-type semiconductor included as a configuration in a photoelectric conversion layer having a ternary configuration. The EQE peak wavelength is measured using a spectral sensitivity light source and a semiconductor parameter analyzer (Agilent “4155C”) for photoelectric conversion elements placed in the dark. Then, the photocurrent was obtained. The photocurrent was converted to the number of electrons and divided by the number of incident photons to obtain EQE. Thereby, the EQE of each wavelength was measured to obtain the spectral sensitivity characteristic, and the sensitivity peak wavelength on the longest wavelength side was obtained. The band gap is also shown as an index of excitation energy of each material. This band gap was calculated from the absorption spectrum measurement of each 100% film formed by vacuum deposition 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 13 was evaluated as follows as the conversion efficiency of the binary element at a drive voltage of 5V.
A: η ≧ 80%
B: η <80%

In the above photoelectric conversion element configuration, the content of the second organic semiconductor is set to 25% by mass, but is used as an index for comparing the respective combinations, in order to evaluate the conversion efficiency (η). However, it is not limited to 25% by mass. For example, the present inventors have confirmed that the above conversion efficiency (η) is substantially constant up to the content of the second organic semiconductor of about 15 to 50% by mass. It is sufficient that the maximum conversion efficiency value is determined based on this.

Next, the energy difference (| ΔEg |) determined from the difference in the EQE peak wavelength of the binary constituent element using the organic semiconductor contained in the constituent material of the ternary element, and the increase rate of the conversion efficiency of 550 nm in the ternary element The results of evaluation using as an index are shown. The “rate of increase in conversion efficiency at 550 nm” in Table 14 as an effect index is the conversion in the p-type semiconductor-n-type semiconductor combination 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 lower efficiency. The OSC described in the table is an abbreviation for Organic Semi-Conductor and is described for the sake of simplicity in the table. The reason why the contents of the second and third organic semiconductors are set as close as possible is to determine the effect.

In Table 14, Comparative Example 23 and Comparative Examples 24 and 25 are in a binary configuration and a ternary configuration. In a similar relationship, Examples 51 and 52 correspond to Comparative Example 26, Example 53 corresponds to Comparative Example 27, Example 54 corresponds to Comparative Example 28, and Example 55 corresponds to Comparative Example 29. To do. From the results of Table 14, there is a tendency that the rate of increase in conversion efficiency increases as | ΔEg | of the configurable binary element is closer to zero. The data of the configurable binary element is based on the contents described in Table 4.

FIG. 12 shows the relationship between | ΔEg | in Table 14 and the rate of increase in conversion efficiency at 550 nm. As shown in FIG. 12, it had a bending point in the vicinity of 0.052 eV. At that time, considering the accuracy of EQE measurement, it was determined that the rate of increase in conversion efficiency was 102% or higher in this evaluation. As a result, it was shown that | ΔEg | is preferably 0.052 eV or less. This result shows that the exciton relaxed to a low energy level can be separated with high efficiency by using another p-type semiconductor-n-type semiconductor 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 of the binary element 1 and the binary element 2 to be combined, of course, the greater the effect. In this embodiment, both η ₁ and η ₂ are selected with a difference of 10% or more. However, in the present invention, the difference is not limited to 10% or more. As described so far, each p-type semiconductor-n-type semiconductor constituting the binary element 1 and the binary element 2 is used. The energy level relationship of is important.

Next, the preferred contents of the first organic semiconductor, the second organic semiconductor, and the third organic semiconductor were verified. This verification verified which concentration of the second organic semiconductor and the third organic semiconductor should be higher.

From Table 15, when the second organic semiconductor is Compound 4 as in Examples 51 and 56 to 61, the conversion efficiency is high in the ternary element. This is because the ratio of direct photoelectric conversion increases when the content of the organic semiconductor constituting the binary element 1 having high conversion efficiency is high, and charge separation is performed by receiving energy from the organic semiconductor constituting the binary element 2. It is derived from the fact that the ratio of increasing the probability of causing an increase is increased. On the contrary, when the second organic semiconductor is Compound 5 as in Examples 62 to 68, the conversion efficiency of the ternary element at 550 nm increases, but the effect is not great. Therefore, it was shown that the first and second organic semiconductors are preferable as a combination with high conversion efficiency. Moreover, although not described, the dark current lowering effect in the ternary element was observed in any combination of Tables 14 and 15.

(Solubility parameter calculation results)
As the second organic semiconductor and the third organic semiconductor are selectively mixed easily, the phenomenon of forming an energy spread of the state density of the HOMO and LUMO levels due to the association between the second organic semiconductors is caused. It is suppressed. It calculated about several organic semiconductors in an Example, and verified whether it was said relationship. The table | surface which put together the relationship of SP value of each organic semiconductor is shown below. In addition, in SP value, since the compound 2 which is a 1st organic semiconductor is C60, the value of the nonpatent literature 3 was used. The SP values of the second organic semiconductor and the third organic semiconductor were obtained by calculation based on Non-Patent Document 2.

A similar device was prepared except that Compound 6 contained in Verification Example E in Table 13 was replaced with dimethylanthracene (SP3 = 20.2). When the dark current of the device was evaluated, the relative dark current (ternary / binary) was about 0.9, and a decrease in dark current was confirmed, but the amount of dark current decrease was less than that of other devices. It was small.
As described above, the photoelectric conversion element having a ternary structure according to the present invention has low dark current characteristics when the mass of the third organic semiconductor is 3 mass% or more.

From the above, the organic photoelectric conversion element of the present invention is an element having an excellent characteristic of low dark current. Therefore, in the optical area sensor, the imaging element, and the imaging device using the organic photoelectric conversion element of the present invention, dark current noise derived from the photoelectric conversion element can be reduced.

This application is Japanese Patent Application No. 2017-020239 filed on Feb. 7, 2017, Japanese Patent Application No. 2017-221684 filed on Nov. 17, 2017, and filed on Dec. 27, 2017. And claims the priority of Japanese Patent Application No. 2017-250929, which is incorporated herein by reference.

1: photoelectric conversion layer (first organic compound layer), 2: second organic compound layer, 3: third organic compound layer, 4: cathode, 5: anode, 6: readout circuit, 7: inorganic protective layer 8: Color filter, 9: Micro lens, 10: Photoelectric conversion element, 15: Charge storage unit, 20: One pixel, 22: Reset transistor, 23: Amplification transistor, 24: Selection transistor, 25: Transfer transistor, 26: Current source, 27: column circuit, 28: output line, 29: wiring, 31: imaging region, 32: vertical scanning circuit, 33: readout circuit, 34: horizontal scanning circuit, 35: output amplifier, 36: circuit region, 37 : Signal processing unit, A: Node, B: Node

Claims

An anode, a photoelectric conversion layer, and a cathode in this order, the photoelectric conversion layer is a photoelectric conversion element having 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 organic semiconductors,
Of the first organic semiconductor and the second organic semiconductor, one is a p-type semiconductor and the other is an n-type semiconductor,
The mass ratio of the first organic semiconductor, the second organic semiconductor, and the third organic semiconductor is
First organic semiconductor ≧ second organic semiconductor ≧ 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 The content of the organic semiconductor is 3% by mass or more.
The photoelectric conversion element according to claim 1, wherein a 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. The photoelectric conversion element according to claim 1 or 2.
The photoelectric conversion element according to any one of claims 1 to 3, wherein the first organic semiconductor is an n-type semiconductor, and the second organic semiconductor is a p-type semiconductor.
The photoelectric conversion element according to claim 4, wherein the third organic semiconductor is a p-type semiconductor.
When the solubility parameter of the first organic semiconductor is SP1, the solubility parameter of the second organic semiconductor is SP2, and the solubility parameter of the third organic semiconductor is SP3, the SP1, SP2, and SP3 are The photoelectric conversion element according to claim 1, wherein the formulas (2) and (3) are satisfied.
| SP1-SP2 |> | SP2-SP3 | (2)
| SP1-SP3 |> | SP2-SP3 | (3)
The photoelectric conversion element according to claim 6, wherein the SP1, the SP2, and the SP3 satisfy the formulas (4) to (6).
| SP1-SP2 | ≧ 2.5 (4)
| SP1-SP3 | ≧ 2.5 (5)
| SP2-SP3 | ≦ 2.5 (6)
The photoelectric conversion element according to claim 6 or 7, wherein the SP2 and the SP3 satisfy the formula (7).
| SP2-SP3 | ≦ 1.0 (7)
When the oxidation potential of the second organic semiconductor is Eox2, the oxidation potential of the third organic semiconductor is Eox3, the reduction potential of the first organic semiconductor is Ered1, and the reduction potential of the third organic semiconductor is Ered3. The photoelectric conversion element according to claim 4, wherein the relationship between the potentials satisfies the expressions (11) and (12).
Eox2 ≦ Eox3 (11)
Ered1 ≧ Ered3 (12)
Among the first organic semiconductor, the second organic semiconductor, and the third organic semiconductor, an organic semiconductor that is a p-type semiconductor is a compound represented by general formulas [1] to [5], a quinacridone derivative, 3H 10. The photoelectric conversion device according to claim 1, wherein the photoelectric conversion device is any one of -phenoxazin-3-one derivatives.

(In 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 substituted or unsubstituted vinyl group, A substituted or unsubstituted amino group or a cyano group is represented.
n 1 , n 2 , and n 3 each independently represents an integer of 0 to 4.
X 1 to X 3 each represents a nitrogen atom, a sulfur atom, an oxygen atom, or a carbon atom that may have a substituent.
Ar 1 and Ar 2 are each independently selected from a substituted or unsubstituted aryl group or a substituted or unsubstituted heterocyclic group. When there are a plurality of Ar 1 and Ar 2 , they may be the same or different, and Ar 1 and Ar 2 may be bonded to each other to form a ring when X 2 or X 3 is a carbon atom.
Z 1 is any of a halogen atom, a cyano group, a vinyl group substituted with a cyano group, a substituted or unsubstituted heteroaryl group, or a substituent represented by the following general formulas [1-1] to [1-9] Represents

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, a substituted or unsubstituted aryl group. Each independently selected from a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted vinyl group, a substituted or unsubstituted amino group, and a cyano group. * Represents a bonding position with a carbon atom. )

(In 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 Each is independently selected from a vinyl group, a substituted or unsubstituted amino group, and a cyano group. Two adjacent R 20 to R 29 may be bonded to 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 are composed of a substituted or unsubstituted aryl group or a substituted or unsubstituted heterocyclic group, and two adjacent L 1 to L 9 are adjacent to each other. Represents a ligand which may be bonded to each other to form a ring. )
The photoelectric semiconductor according to any one of claims 1 to 10, wherein an organic semiconductor that is an n-type semiconductor among the first organic semiconductor and the second organic semiconductor is a fullerene or a fullerene derivative. Conversion element.
The photoelectric conversion element according to claim 11, wherein the fullerene derivative is fullerene C60.
The photoelectric conversion element according to any one of claims 1 to 12, wherein the first organic semiconductor, the second organic semiconductor, and the third organic semiconductor satisfy the following conditions.
(Conditions) When two different photoelectric conversion layers are formed using the bodies of the first organic semiconductor, the second organic semiconductor, and the third organic semiconductor,
Of the two different photoelectric conversion layers, the conversion efficiency of the photoelectric conversion layer having the EQE peak on the long wavelength side is the conversion efficiency of the photoelectric conversion layer having the EQE peak on the short wavelength side of the two different photoelectric conversion layers. More than conversion efficiency.
The photoelectric conversion element according to any one of claims 1 to 12, wherein the first organic semiconductor, the second organic semiconductor, and the third organic semiconductor satisfy the following conditions.
(Condition) When two different photoelectric conversion layers are formed using the first organic semiconductor, the second organic semiconductor, and the third organic semiconductor, the following formulas (8) and (9) Is satisfied.
η 1 > η 2 (8)
| ΔEg | ≦ 0.052 eV (9)
η 1 is the conversion efficiency of an element having an EQE peak on the long wavelength side, and η 2 is the conversion efficiency of an element having an EQE peak on the short wavelength side. And the conversion efficiency of the photoelectric conversion element which has a 1st thru | or 3rd organic semiconductor is represented as (eta) 3 .
ΔEg is an energy difference obtained from an EQE peak wavelength difference of a binary element having a photoelectric conversion layer composed of one organic semiconductor of p-type and n-type among the first, second, and third organic semiconductors.
An optical area sensor having a plurality of pixels including photoelectric conversion elements, wherein the plurality of pixels are two-dimensionally arranged,
The said photoelectric conversion element is a photoelectric conversion element as described in any one of Claims 1 thru | or 14, The optical area sensor characterized by the above-mentioned.
An imaging device having a plurality of pixels each including a photoelectric conversion element and a readout circuit connected to the photoelectric conversion element, and a signal processing circuit connected to the pixel,
The said photoelectric conversion element is a photoelectric conversion element as described in any one of Claims 1 thru | or 14, The imaging element characterized by the above-mentioned.
An imaging apparatus comprising: an imaging optical unit having a plurality of lenses; and an imaging device that receives light that has passed through the imaging optical unit, wherein the imaging device is the imaging device according to claim 16.
The imaging apparatus further includes a receiving unit that receives a signal from the outside, and the signal is a signal that controls at least one of an imaging range, an imaging start, and an imaging end of the imaging apparatus. The imaging device according to claim 17.
The imaging apparatus according to claim 17 or 18, wherein the imaging apparatus further includes a transmission unit that transmits an acquired image to the outside.