KR20160043016A - Photoelectric conversion element and imaging element - Google Patents

Abstract

In the photoelectric conversion element, a lower electrode, an electron blocking layer, a photoelectric conversion layer, an intermediate layer, and an upper electrode are stacked in this order. The photoelectric conversion layer is a bulk hetero layer in which a p-type organic semiconductor is mixed with a crystallized fullerene or a crystallized fullerene derivative. The intermediate layer contains amorphous fullerene or an amorphous fullerene derivative, and the upper electrode is composed of a transparent conductive film.

Description

[0001] PHOTOELECTRIC CONVERSION ELEMENT AND IMAGING ELEMENT [0002]

The present invention relates to a photoelectric conversion element and an image pickup element which are constituted by using an organic compound for generating a charge in response to light received and convert visible light images into electric signals, And a photoelectric conversion element and an image pickup device having low dark current.

2. Description of the Related Art [0002] An image sensor used in a digital still camera, a digital video camera, a camera for a mobile phone, a camera for an endoscope, or the like is a device in which pixels including a photodiode are arranged on a semiconductor substrate such as a silicon (Si) chip, Solid-state image pickup devices such as a CCD sensor and a MOS sensor that acquire signal charges corresponding to photoelectrons generated by a CCD type or CMOS type read circuit are widely known. At present, development of a photoelectric conversion device using an organic compound is proceeding (Patent Documents 1 to 3, etc.).

Patent Document 1 discloses an organic photoelectric conversion device having a structure in which a plurality of functional layers are stacked, such as a photoelectric conversion layer that absorbs light to generate charges and a charge blocking layer that suppresses charge injection from the electrodes.

Patent Document 2 discloses an organic photovoltaic device having an oriented film of an organic compound of the same composition and a laminated film of an amorphous film.

Here, high photoelectric conversion efficiency and low dark current are required for the photoelectric conversion element. Therefore, Patent Document 3 shows a structure including crystallized fullerene or fullerene derivative in the photoelectric conversion layer as a structure for realizing high photoelectric conversion efficiency and low dark current.

Patent Document 1: JP-A-2007-88033 Patent Document 2: JP-A-6-232435 Patent Document 3: JP-A-2011-14895

As described above, Patent Document 3 discloses a structure including fullerene or fullerene derivatives crystallized in the photoelectric conversion layer as a structure for realizing high photoelectric conversion efficiency and low dark current. However, a structure in which a high photoelectric conversion efficiency and a low dark current are required .

It is an object of the present invention to provide a photoelectric conversion element and an image pickup element which solve the problems based on the above-described conventional techniques and have high photoelectric conversion efficiency and low dark current.

In order to achieve the above object, a first aspect of the present invention is a photoelectric conversion device comprising a lower electrode, an electron blocking layer stacked on the lower electrode, a photoelectric conversion layer stacked on the blocking layer, an intermediate layer stacked on the photoelectric conversion layer, And an upper electrode stacked on the intermediate layer, wherein the photoelectric conversion layer is a bulk hetero layer in which a p-type organic semiconductor is mixed with a crystallized fullerene or a crystallized fullerene derivative, and the intermediate layer includes an amorphous fullerene or an amorphous fullerene derivative And the upper electrode is composed of a transparent conductive film.

The photoelectric conversion layer is preferably composed of a p-type organic semiconductor and a bulk hetero layer formed by mixing fullerene or crystallized fullerene derivative oriented in the (111) direction perpendicular to the surface of the lower electrode.

The photoelectric conversion layer preferably contains crystallized fullerene or crystallized fullerene derivative in a ratio of 30% to 80%.

The thickness of the intermediate layer is preferably one third or more of the thickness of the upper electrode, and the thickness of the intermediate layer is preferably not more than the thickness of the upper electrode.

The intermediate layer preferably further comprises at least one organic material. The intermediate layer is preferably a layer obtained by mixing amorphous fullerene or an amorphous fullerene derivative with a transparent hole transporting material having an ionization potential of 5.5 eV or more.

The upper electrode is made of ITO, and the thickness of the upper electrode is preferably 5 to 30 nm.

A second aspect of the present invention is to provide an image pickup device having the photoelectric conversion element of the first aspect of the present invention.

According to the present invention, in the photoelectric conversion element and the image pickup element, the photoelectric conversion efficiency can be improved and the dark current can be reduced.

1 (a) is a schematic cross-sectional view showing a photoelectric conversion element according to an embodiment of the present invention, (b) is an enlarged view of a main part of a photoelectric conversion element according to an embodiment of the present invention, Fig. 2 is an enlarged view of a main part showing a modification of the photoelectric conversion element according to the embodiment of the present invention.
2 (a) is a schematic cross-sectional view showing an image pickup device according to an embodiment of the present invention, and (b) is an enlarged view of a main part of an image pickup device according to an embodiment of the present invention.
3 (a) to 3 (c) are schematic cross-sectional views showing the manufacturing method of an image pickup device according to the embodiment of the present invention in the order of steps.
4 (a) to 4 (c) are schematic cross-sectional views showing the manufacturing method of an image pickup device according to the embodiment of the present invention in the order of steps, and show a step after the step of FIG. 3 (c).

Hereinafter, the photoelectric conversion element and the image pickup element of the present invention will be described in detail based on a preferred embodiment shown in the accompanying drawings.

Fig. 1 (a) is a schematic sectional view showing a photoelectric conversion element according to an embodiment of the present invention, Fig. 1 (b) is an enlarged view of a main part of a photoelectric conversion element according to an embodiment of the present invention, Sectional view showing a modified example of the photoelectric conversion element according to the embodiment of the present invention.

The photoelectric conversion element 100 shown in Fig. 1 converts the incident light L into an electric signal. The photoelectric conversion element 100 is formed by stacking a lower electrode 104 on a surface 102a of a substrate 102. [ An electron blocking layer 106 is formed on the lower electrode 104 and a photoelectric conversion layer 108 is stacked on the electron blocking layer 106.

An intermediate layer 110 is formed on the photoelectric conversion layer 108 and an upper electrode 112 is stacked on the intermediate layer 110. A sealing layer 114 covering the lower electrode 104, the organic layer 120, and the upper electrode 112 is formed.

The electron blocking layer 106, the photoelectric conversion layer 108, and the intermediate layer 110 are collectively referred to as an organic layer 120.

The incident light L is incident on the photoelectric conversion layer 108 of the organic layer 120 from the surface 112a side of the upper electrode 112 in the photoelectric conversion element 100 and the incident light L is incident on the photoelectric conversion layer 108 to an electrical signal. Accordingly, the sealing layer 114 and the upper electrode 112 transmit the incident light L as described later.

The substrate 102 is composed of, for example, a silicon substrate, a glass substrate, or the like. The substrate 102 is not particularly limited as long as the photoelectric conversion element 100 can be formed.

The lower electrode 104 is an electrode for trapping holes in the charge generated in the photoelectric conversion layer 108. Examples of the material of the lower electrode 104 include metals, metal oxides, metal nitrides, metal borides and organic conductive compounds, and mixtures thereof. Specific examples include conductive metal oxides such as tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), indium zinc oxide (IZO), indium tungsten oxide (IWO) and titanium oxide, metal nitride such as titanium nitride (TiN) A metal such as gold (Au), platinum (Pt), silver (Ag), chromium (Cr), nickel (Ni) and aluminum (Al), or a mixture or laminate of these metals and a conductive metal oxide, Organic conductive compounds such as thiophene and polypyrrole, and a laminate of these and ITO. Particularly preferable as the material of the lower electrode 104 is any one of titanium nitride, molybdenum nitride, tantalum nitride, and tungsten nitride.

The electron blocking layer 106 is a layer for preventing electrons from being injected from the lower electrode 104 into the photoelectric conversion layer 108, and is composed of a single layer or a plurality of layers. The electron blocking layer 106 may be composed of a single film of an organic material or a mixed film of a plurality of different organic materials.

As the electron blocking layer 106, an electron-donating organic material can be used. Specific examples of the low molecular material include N, N'-bis (3-methylphenyl) - (1,1'-biphenyl) -4,4'-diamine (TPD) or 4,4'-bis [N - (naphthyl) -N-phenyl-amino] biphenyl (? -NPD), oxazole, oxadiazole, triazole, imidazole, imidazolone, stilbene derivatives, pyrazoline derivatives , 4,4 ', 4 "-tris (N- (3-methylphenyl) N-phenylamino) triphenylamine (m-MTDATA), polyphosphine, tetraphenyl There may be mentioned a porphyrin compound such as phophinic copper, phthalocyanine, copper phthalocyanine, and titanium phthalocyanine oxide, a triazole derivative, an oxadiazole derivative, an imidazole derivative, a polyarylalkane derivative, a pyrazolone derivative, Derivatives, phenylene diamine derivatives, anilamine derivatives, amino substituted chalcone derivatives, oxazole derivatives, styryl anthracene derivatives, fluoro A carbazole derivative, a bifluorene derivative, or the like can be used as the polymer material. Examples of the polymer material include phenylene vinylene, fluorene, carbazole, indole, pyrene, pyrrole, picoline , Thiophene, acetylene, diacetylene, etc., and derivatives thereof can be used. Even if it is not an electron donor compound, a compound having sufficient hole transportability can be used.

The electron blocking layer 106 is preferably made of a material having a high electron injection barrier from the adjacent lower electrode 104 and high hole transportability. As the electron injection barrier, the electron affinity of the electron blocking layer 106 is preferably 1 eV or more, more preferably 1.3 eV or more, and particularly preferably 1.5 eV or more, more than the work function of the adjacent electrode.

The electron blocking layer 106 is formed to have a film thickness of 20 nm or less in order to sufficiently suppress contact between the lower electrode 104 and the photoelectric conversion layer 108 and to avoid the influence of defects and foreign substances present on the surface of the lower electrode 104. [ Or more, more preferably 40 nm or more, and particularly preferably 60 nm or more.

On the other hand, if the film thickness of the electron blocking layer 106 is too thick, there arises a problem that the supply voltage necessary for applying the appropriate electric field intensity to the photoelectric conversion layer 108 becomes high, There arises a problem that the process adversely affects the performance of the photoelectric conversion element. The thickness of the electron blocking layer 106 is preferably 300 nm or less, more preferably 200 nm or less, and further preferably 100 nm or less.

The photoelectric conversion layer 108 is a layer including a photoelectric conversion material which receives the incident light L and generates charges according to the amount of the light. In the photoelectric conversion layer 108, an organic compound can be used as the photoelectric conversion material.

The photoelectric conversion layer 108 is a bulk hetero layer in which a p-type organic semiconductor (organic p-type compound) and a crystallized fullerene or a crystallized fullerene derivative are mixed. The photoelectric conversion layer 108 has a bulk hetero structure. By using the bulk hetero layer as the photoelectric conversion layer 108, it is possible to improve the photoelectric conversion efficiency by making up for the drawback that the carrier diffusion length of the organic layer 120 is short. By forming the bulk hetero layer at the optimum mixing ratio, the electron mobility and hole mobility of the photoelectric conversion layer 108 can be increased, and the light response speed of the photoelectric conversion element 100 can be made sufficiently high. As a result, the ratio of the crystallized fullerene or the crystallized fullerene derivative in the photoelectric conversion layer 108 is preferably 30% to 80% by volume.

In the photoelectric conversion layer 108, since fullerene or a fullerene derivative is in a crystallized state, a higher photoelectric conversion efficiency can be obtained, and a fullerene or fullerene derivative carrier path is effectively formed, And can contribute to the high-speed response of the device 100. [ As means for crystallizing the fullerene or the fullerene derivative, a suitable photoelectric conversion material is selected and then the ratio of the fullerene type is increased, and the substrate is heated during the film formation.

Whether or not the fullerene or the fullerene derivative is in a crystallized state can be judged by whether or not a crystal peak derived from the crystal structure of the fullerene or the fullerene derivative is confirmed on the X-ray diffraction of the film containing the fullerene or the fullerene derivative. In addition, it can be judged whether or not the diffraction point derived from the crystal structure of the fullerene or the fullerene derivative is confirmed on the electron beam diffraction image of the cross section by the electron beam diffraction on the cross-sectional TEM of the film containing the fullerene or the fullerene derivative.

A fullerene or a fullerene derivative is added to the surface 104a of the lower electrode 104 (the surface 102a of the substrate 102) in the photoelectric conversion layer 108 including the crystallized fullerene or the crystallized fullerene derivative 111 ) Direction.

Since the fullerene or fullerene derivative is oriented in the (111) direction perpendicular to the substrate surface, the irregularities of the photoelectric conversion layer 108 including the fullerene fullerene derivative are suppressed compared with the case where the structure is randomly crystallized As a result, the upper electrode enters the concavity and convexity to suppress the increase of the leakage current in the vicinity of the lower electrode, or the flatness and coverage of the layer to be formed on the photoelectric conversion layer (for example, the charge blocking layer) Or a high dark current suppressing effect is obtained.

From this viewpoint, it is preferable that the crystallized fullerene or the crystallized fullerene derivative in the photoelectric conversion layer 108 is crystallized in the same manner, that is, the orientation direction is the same. Among them, the orientation direction is (111) direction preferably in a volume ratio of 50 to 100%, more preferably 80 to 100%.

In order to control the crystal orientation of the fullerene or fullerene derivative, the crystal orientation can be realized by adjusting the substrate temperature and the deposition rate at the time of film formation. Specifically, it is preferable to heat the substrate temperature to a higher temperature, and to set the deposition rate at a slower rate. However, if the excessively high temperature and low deposition rate are employed, the crystallization of the fullerene or the fullerene derivative is promoted, and the unevenness of the film surface in the mixed layer of the fullerene or the fullerene derivative and the photoelectric conversion material may be increased. If the irregularities on the film surface are increased, when an electrode is laid on the upper layer, a short circuit (leak current) is increased, and dark current is increased, which is not preferable.

The substrate temperature is preferably 120 占 폚 or lower, more preferably 100 占 폚 or lower, although it depends on the kind of the material other than the fullerene or the fullerene derivative present in the photoelectric conversion layer 108, the content ratio of the fullerene or the fullerene derivative, desirable. The lower limit of the substrate temperature is preferably 60 占 폚, and more preferably 70 占 폚 to 90 占 폚.

The deposition rate varies depending on the content ratio of the fullerene or the fullerene derivative other than the fullerene or the fullerene derivative present in the photoelectric conversion layer 108. The deposition rate is preferably 0.1 to 15 A / s, more preferably 0.5 to 3.0 A / s Is more preferable.

The reason why the fullerene or the fullerene derivative is oriented in the (111) direction perpendicular to the surface 104a of the lower electrode 104 is that the fullerene A crystal peak of a fullerene or a fullerene derivative is observed by measuring the film or the fullerene derivative film by an X-ray diffraction method and the peak is observed with respect to a direction perpendicular to the surface of the substrate corresponding to the surface 104a of the lower electrode 104 (111), (222), (333) in the direction of the arrow (111).

In addition to the X-ray diffraction method, the orientation in the (111) direction can be measured from the electron beam diffraction image of the cross section by the electron beam diffraction on the cross section TEM.

Hereinafter, fullerene and fullerene derivatives will be described in more detail.

The fullerene includes fullerene C ₆₀ , fullerene C ₇₀ , fullerene C ₇₆ , fullerene C ₇₈ , fullerene C ₈₀ , fullerene C ₈₂ , fullerene C ₈₄ , fullerene C ₉₀ , fullerene C ₉₆ , fullerene C ₂₄₀ , fullerene C ₅₄₀ , , And fullerene nanotubes.

The fullerene derivative is a compound to which a substituent is added to fullerene. The substituent is preferably an alkyl group, an aryl group or a heterocyclic group. The alkyl group preferably has 1 to 12 carbon atoms, more preferably 1 to 6 carbon atoms. Examples of the aryl group include a phenyl group, a naphthyl group and an anthryl group. Examples of the heterocyclic group include furyl, thienyl, pyrrolyl, oxazolyl, pyridyl, quinolyl, carbazolyl and the like. As the fullerene derivative, the following compounds are particularly preferable.

[Chemical Formula 1]

(2)

As fullerene and fullerene derivatives, there can be cited the Chemical Abstracts of the Chemical Society of Japan. 43 (1999), JP-A-10-167994, JP-A-11-255508, JP-A-11-255509, JP-A-2002-241323, and JP- -196881 or the like may be used.

The p-type organic semiconductor material (compound) is a donor organic semiconductor material (compound), which is represented by a hole-transporting organic compound, and is an organic compound having a property of donating electrons. More specifically, it refers to an organic compound having a small ionization potential when two organic materials are used in contact with each other. Therefore, any organic compound can be used as long as the donor organic compound is an organic compound having an electron donor. Examples of the compound include triarylamine compounds, benzidine compounds, pyrazoline compounds, styrylamine compounds, hydrazone compounds, triphenylmethane compounds, carbazole compounds, polysilane compounds, thiophene compounds, phthalocyanine compounds Anthracene derivatives, phenanthrene derivatives, tetracene derivatives, phenanthrene derivatives, phenanthrene derivatives, phenanthrene derivatives, phenanthrene derivatives, phenanthrene derivatives, phenanthrene derivatives, Derivatives, pyrene derivatives, perylene derivatives, fluoranthene derivatives), metal complexes having a nitrogen-containing heterocyclic compound as a ligand, and the like can be used. As described above, an organic compound having an ionization potential smaller than that of an organic compound used as an n-type (acceptor) compound may be used as a donor organic semiconductor.

As the p-type organic semiconductor material (compound) used for the photoelectric conversion layer 108, a triarylamine compound and a pyran compound are preferable, and a triarylamine compound is more preferable. As the triarylamine compound, a compound represented by the following general formula (1) is preferable.

(3)

In the general formula (1), Z ₁ represents a condensed ring containing at least any one of a 5-membered ring, a 6-membered ring, a 5-membered ring and a 6-membered ring, L ₁ , L ₂ , and L ₃ each independently represent an unsubstituted meta-popular, or a substituted meta-popular. D ₁ represents an atomic group. n represents an integer of 0 or more.

Z ₁ is a ring containing at least two carbon atoms, and represents a condensed ring containing at least one of a 5-membered ring, a 6-membered ring, or a 5-membered ring and a 6-membered ring. As the condensed ring containing at least one of a 5-membered ring, a 6-membered ring, or a 5-membered ring and a 6-membered ring, it is preferable that the condensed ring is usually used as an acidic nucleus in a merocyanine dye. Specific examples thereof include the following .

(a) a 1,3-dicarbonyl nucleus such as 1,3-indeundanone nucleus, 1,3-cyclohexanedione, 5,5-dimethyl-1,3-cyclohexanedione , 1,3-dioxane-4,6-dione, and the like.

(b) pyrazolone nucleus such as 1-phenyl-2-pyrazolin-5-one, 3-methyl-1-phenyl-2-pyrazolin- ) -3-methyl-2-pyrazolin-5-one.

(c) isoxazolinone nucleus such as 3-phenyl-2-isooxazolin-5-one, 3-methyl-2-isooxazolin-5-one and the like.

(d) oxyindole nucleus: for example, 1-alkyl-2,3-dihydro-2-oxyindole and the like.

(e) 2,4,6-Tricetohexahydropyrimidine nucleus: for example, bivalent or 2-thiobarbituric acid and derivatives thereof. Examples of the derivative include 1-alkyl such as 1-methyl and 1-ethyl, 1,3-dialkyl such as 1,3-dimethyl, 1,3-diethyl and 1,3- 1,3-di (p-chlorophenyl), and 1,3-di (p-ethoxycarbonylphenyl), and the like; 1-alkyl-1-aryl, 1,3-di (2-pyridyl), and the like.

(f) 2-thio-2,4-thiazolidinedione nucleus: for example, rhodanine and derivatives thereof. Examples of the derivatives include 3-alkylaldanines such as 3-methylordanine, 3-ethylordanine and 3-allyloxanine, 3-arylordanines such as 3- ) Third order heterocyclic substituted rhodanines such as rhodanine, and the like.

(g) 2-thio-2,4-oxazolidinedione (2-thio-2,4- (3H, 5H) -oxazole ion) 2,4-oxazolidinedione, and the like.

(h) Thianapthion nucleus: for example, 3 (2H) -thianaphthone-1,1-dioxide.

(i) 2-thio-2,5-thiazolidinedione ion nucleus such as 3-ethyl-2-thio-2,5-thiazolidinedione.

(j) 2,4-thiazolidinedione nuclei such as 2,4-thiazolidinedione, 3-ethyl-2,4-thiazolidinedione, 3-phenyl- Azolydinedione, and the like.

(k) Thiazolin-4-one nuclei such as 4-thiazolinone, 2-ethyl-4-thiazolinone, and the like.

(l) 2,4-imidazolidinedione (hydantoin) nucleus: 2,4-imidazolidinedione, 3-ethyl-2,4-imidazolidinedione, and the like.

(m) 2-thio-2,4-imidazolidinedione (2-thiohydantoin) nucleus: 2-thio-2,4-imidazolidinedione, -Thio-2,4-imidazolidinedione, and the like.

(n) imidazolin-5-one nuclei such as 2-propylmercapto-2-imidazolin-5-one and the like.

(o) 3,5-pyrazolidinedione nuclei such as 1,2-diphenyl-3,5-pyrazolidinedione, 1,2-dimethyl-3,5-pyrazolidinedione and the like.

(p) benzothiophen-3-one nuclei such as benzothiophen-3-one, oxobenzothiophen-3-one, dioxobenzothiophen-3-one and the like.

(q) indanone nucleus such as 1-indanone, 3-phenyl-1-indanone, 3-methyl-1-indanone, Methyl-1-indanone, and the like.

The ring formed of Z ₁ is preferably a 1,3-dicarbonyl nucleus, a pyrazolone nucleus, a 2,4,6-tricetohexahydropyrimidine nucleus (including a thioketone, for example, Thiobarbituric acid nucleus), 2-thio-2,4-thiazolidinedione nucleus, 2-thio-2,4-oxazolidinedione nucleus, 2-thio- Thiazolidinedione ion nucleus, 2,4-imidazolidinedione ion nucleus, 2-thio-2,4-imidazolidinedione ion nucleus, 2-thiazolidinedione ion nucleus, -Imidazoline-5-one nucleus, 3,5-pyrazolidinedione nucleus, benzothiophen-3-one nucleus, indanone nucleus, more preferably 1,3-dicarbonyl nucleus, 2,4 , 6-triketohexahydropyrimidine nucleus (including thioketone bodies, for example, bovital nucleus, 2-thiobarbital nucleus), 3,5-pyrazolidinedione nucleus, benzothiophene- 3-on nucleus, indanone nucleus, more preferably a 1,3-dicarbonyl nucleus, 2,4,6-tri Ketohexahydropyrimidine nucleus (including thioketone, for example, bovital nucleus and 2-thiobarbituric acid nucleus), particularly preferably 1,3-indeindan ion nucleus, bovisulphonic nucleus , 2-thiobarbituric acid nuclei and derivatives thereof.

L ₁ , L ₂ , and L ₃ each independently represent an unsubstituted meta-popular, or a substituted meta-popular. (E.g., a 6-membered ring, for example, a benzene ring) may be formed. The substituent of the substituted methoxy group may include the substituent W, but it is preferable that all of L ₁ , L ₂ and L ₃ are unsubstituted meta-groups.

L ₁ to L ₃ may be connected to each other to form a ring, and examples of the ring to be formed include a cyclohexane ring, a cyclopentane ring, a benzene ring, and a thiophene ring.

n represents an integer of 0 or more, preferably 0 or more and 3 or less, and more preferably 0. When n is increased, the absorption wavelength range can be set to a long wavelength or the decomposition temperature due to heat is lowered. N = 0 is preferable in that it has appropriate absorption in the visible region and suppresses thermal decomposition at the time of deposition film formation.

D ₁ represents an atomic group. D ₁ is preferably a group containing -NR ^a (R ^b ), and more preferably -NR ^a (R ^b ) represents a substituted arylene group. R ^a and R ^b each independently represent a hydrogen atom or a substituent.

The arylene group represented by D ₁ is preferably an arylene group having 6 to 30 carbon atoms, and more preferably an arylene group having 6 to 18 carbon atoms. The arylene group may have a substituent W described later, and is preferably an arylene group having 6 to 18 carbon atoms, which may have an alkyl group having 1 to 4 carbon atoms. For example, a phenylene group, a naphthylene group, an anthracenerene group, a pyreneylene group, a phenanthreneylene group, a methylphenylene group, a dimethylphenylene group and the like are exemplified, and a phenylene group or a naphthylene group is preferable.

As the substituent represented by R ^a and R ^b , there may be mentioned a substituent W described later, preferably an aliphatic hydrocarbon group (preferably an alkyl group or alkenyl group which may be substituted), an aryl group (preferably a phenyl group which may be substituted) , Or a heterocyclic group.

Each of the aryl groups represented by R ^a and R ^b is preferably an aryl group having 6 to 30 carbon atoms, and more preferably an aryl group having 6 to 18 carbon atoms. The aryl group may have a substituent, and is preferably an aryl group having 6 to 18 carbon atoms, which may have an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 18 carbon atoms. For example, a phenyl group, a naphthyl group, an anthracene group, a pyrenyl group, a phenanthrene group, a methylphenyl group, a dimethylphenyl group, a biphenyl group and the like are exemplified, and a phenyl group or a naphthyl group is preferable.

Each of the heterocyclic groups represented by R ^a and R ^b is independently a heterocyclic group having preferably 3 to 30 carbon atoms, more preferably a heterocyclic group having 3 to 18 carbon atoms. The heterocyclic group may have a substituent, and is preferably a heterocyclic group having 3 to 18 carbon atoms which may have an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 18 carbon atoms. The heterocyclic group represented by R ^a and R ^b is preferably a cyclic structure and may be a furan ring, a thiophene ring, a selenopentane ring, a silole ring, a pyridine ring, a pyrazine ring, a pyrimidine ring, an oxazole ring, (Identical to) a ring selected from a triazole ring, an oxadiazole ring and a thiadiazole ring, and is preferably a quinoline ring, an isoquinoline ring, a benzothiophene ring, a dibenzothiophene ring, a cyano A thiophene ring, a bicyanobenzene ring, and a bicyanothiophene ring are preferable.

The arylene group and the aryl group represented by D ₁ , R ^a and R ^b are preferably a benzene ring or a condensed ring structure, more preferably a condensed ring structure containing a benzene ring, more preferably a naphthalene ring, an anthracene ring, A benzene ring, a naphthalene ring or an anthracene ring is more preferable, and a benzene ring or a naphthalene ring is more preferable.

The substituent W includes a halogen atom, an alkyl group (including a cycloalkyl group, a bicycloalkyl group and a tricycloalkyl group), an alkenyl group (including a cycloalkenyl group and a bicycloalkenyl group), an alkynyl group, an aryl group, a heterocyclic group An alkoxy group, an aryloxy group, a silyloxy group, a heterocyclic oxy group, an acyloxy group, a carbamoyloxy group, an alkoxycarbonyl group, a carbamoyloxy group, an alkoxycarbonyl group, An alkoxycarbonyl group, an aryloxycarbonyl group, an amino group (including an anilino group), an ammonio group, an acylamino group, an aminocarbonylamino group, an alkoxycarbonylamino group, an aryloxycarbonylamino group, a sulfamoylamino group, an alkylsulfonylamino group, Alkyl and arylsulfinyl groups, an acyl group, an aryloxycarbonyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an aryloxycarbonyl group, an aryloxycarbonyl group, an aryloxycarbonyl group, A carbamoyl group, an aryl and a heterocyclic azo group, an imide group, a phosphino group, a phosphine group, a phosphineioxy group, a phosphinylamino group, a phosphono group, a silyl group, a hydrazino group, (-B (OH) ₂ ), phosphato group (-OPO (OH) ₂ ), sulfato group (-OSO ₃ H) and other known substituents.

When R ^a and R ^b represent a substituent (preferably an alkyl group or an alkenyl group), the substituent may be a hydrogen atom of an aromatic ring (preferably a benzene ring) skeleton of an aryl group substituted with -NR ^a (R ^b ) , Or may form a ring (preferably a 6-membered ring) by bonding with a substituent.

R ^a, R ^b are even with each other a substituent bonded to each other to form a ring (preferably a 5-or 6-membered rings, more preferably 6-membered ring), and R ^a, R ^b are each the L (L _1, L ₂ or L ₃ ) to form a ring (preferably a 5-membered or 6-membered ring, more preferably a 6-membered ring).

The compound represented by the general formula (1) is a compound described in Japanese Patent Application Laid-Open No. 2000-297068, and a compound not described in the above publication can be produced in accordance with the synthesis method described in the above publication.

Specific examples of the compound represented by the general formula (1) include the following compounds, but the present invention is not limited thereto.

[Chemical Formula 4]

(Molecular Weight)

The compound represented by the general formula (1) preferably has a molecular weight of 300 or more and 1500 or less, more preferably 350 or more and 1,200 or less, and still more preferably 400 or more and 900 or less from the viewpoint of film forming suitability. When the molecular weight is too small, the film thickness of the formed photoelectric conversion film is reduced due to volatilization. Conversely, when the molecular weight is too large, deposition is impossible and a photoelectric conversion element can not be produced.

(Melting point)

The compound represented by the general formula (1) preferably has a melting point of 200 ° C or higher, more preferably 220 ° C or higher, and still more preferably 240 ° C or higher, from the viewpoint of vapor deposition stability. If the melting point is low, the film is melted before deposition and can not be stably formed. In addition, since the decomposition products of the compound are increased, the photoelectric conversion performance deteriorates.

(Absorption spectrum)

The peak wavelength of the absorption spectrum of the compound represented by the general formula (1) is preferably from 400 nm to 700 nm, more preferably from 480 nm to 700 nm, further preferably from 510 nm to 680 nm from the viewpoint of absorbing light in a visible region Do.

(Molar extinction coefficient of peak wavelength)

From the viewpoint of efficiently using light, the compound represented by the general formula (1) has a higher molar absorptivity coefficient. Absorption spectrum (in chloroform solution) is, in the visible region at a wavelength of 400nm to 700nm, and the molar absorption coefficient of 20000M ^-1 cm ^-1 or more are preferred, more preferably more than 30000M ^-1 cm ^-1, 40000M ^-1 cm < ^-1 > is more preferable.

The intermediate layer 110 is a layer introduced between the photoelectric conversion layer 108 and the upper electrode 112.

The intermediate layer 110 has a function of transporting electrons generated in the photoelectric conversion layer 108 to the upper electrode 112 and suppressing hole injection from the upper electrode 112 to the photoelectric conversion layer 108. [

The intermediate layer 110 is composed of a layer containing amorphous fullerene or an amorphous fullerene derivative.

Since the photoelectric conversion layer 108 includes the crystallized structure as described above, when the upper electrode 112 is directly formed on the photoelectric conversion layer 108, the upper electrode 112 penetrates the crystal grain boundaries, The electric field is concentrated at the corner where the voltage is applied between the upper and lower electrodes and the injection current from the upper electrode 112 is increased. By forming a layer containing amorphous fullerene or an amorphous fullerene derivative as the intermediate layer 110 between the photoelectric conversion layer 108 and the upper electrode 112, The electric field concentration is suppressed, and the injection current can be suppressed to a large extent. Of the charges generated in the photoelectric conversion layer 108, electrons are collected in the upper electrode 112 via the intermediate layer 110, but by using a layer containing amorphous fullerene or an amorphous fullerene derivative in the intermediate layer 110, It is possible to transport electrons.

If the film thickness of the intermediate layer 110 is too small, the effect of suppressing the injection of holes from the upper electrode 112 into the photoelectric conversion layer 108 is not sufficiently exhibited. In order to sufficiently exhibit the effect of suppressing the hole injection, when the thickness of the intermediate layer 110 is t ₁ and the thickness of the upper electrode 112 is t ₂ , as shown in Fig. 1 (b) the thickness (t ₁₎ of 110 is preferably a _{t 1 ≥1 / 3 × t 2} .

On the other hand, if the film thickness of the intermediate layer 110 is made too thick, the supply voltage required for applying the appropriate electric field intensity to the photoelectric conversion layer 108 becomes high. For this reason, the upper limit value of the film thickness of the intermediate layer 110 is, for example, 100 nm or less, preferably 50 nm or less, more preferably 20 nm or less.

In addition, the upper limit value of the thickness (t ₁₎ of the middle layer 110, in the case where, based on the upper electrode 112, with respect to the thickness (t ₂₎ of the upper electrode 112, t ₁ ≤t preferably ₂ Do. The thickness (t ₁₎ at this point, the middle layer 110, in the case where, based on the upper electrodes 112, preferably 1/3 × t ₂ of ≤t ₁ ≤t _2.

The dark current can be reduced by defining the thickness t ₁ of the intermediate layer 110 as described above with respect to the thickness t ₂ of the upper electrode 112.

The intermediate layer 110 may be composed of amorphous fullerene or an amorphous fullerene derivative and a mixed layer of an organic p-type compound contained in the photoelectric conversion layer 108. In addition, the intermediate layer 110 can be formed of a mixed layer of amorphous fullerene or an amorphous fullerene derivative and a transparent hole transporting material.

In order to suppress the injection of the transparent hole, it is preferable to use a material having an ionization potential of 5.5 eV or more for the transparent hole transport material. By using a material having an ionization potential of 5.5 eV or more as the transparent hole transporting material, hole injection from the upper electrode 112 can be sufficiently suppressed. Thereby, the dark current can be reduced.

The transparent hole transporting material is preferably a material having an ionization potential of 6 eV or less and a difference between an ionization potential and an electron affinity of 3 eV or more. The ionization potential of the material can be measured by using a AC-2 surface analyzer manufactured by Riken Keiki Co., Ltd. and depositing a material on the quartz substrate to a film thickness of about 100 nm. In order to obtain the difference between the ionization potential and the electron affinity, the specularity of the material formed first is measured, and the energy of the absorption edge is obtained. The energy of the absorption edge corresponds to the energy difference between the ionization potential and the electron affinity.

The intermediate layer 110 may be a layer having a constant ratio of the fullerene or fullerene derivative and the transparent hole transporting material, or a gradation layer having a different ratio depending on the film thickness direction.

When the ratio of the amorphous fullerene or the amorphous fullerene derivative in the intermediate layer 110 is too small, the electron transporting ability of the intermediate layer 110 is lowered and the electrons generated in the photoelectric conversion layer 108 are transferred to the upper electrode 112, The efficiency of transport to the electrode is lowered, and the photoelectric conversion efficiency is lowered. The amorphous fullerene or the amorphous fullerene derivative absorbs visible light and thus carriers are generated by the absorbed light in the intermediate layer 110. When the ratio of the amorphous fullerene or the amorphous fullerene derivative in the intermediate layer 110 is too large, The hole transporting ability of the organic EL element is lowered, leading to a delay in the response speed. As a result, the ratio of the amorphous fullerene or the amorphous fullerene derivative in the intermediate layer 110 is preferably 30% to 80% by volume.

Hereinafter, specific examples of the transparent hole transporting material will be described.

As the transparent hole transporting material, an electron donating organic material can be used. Specific examples of the low molecular material include N, N'-bis (3-methylphenyl) - (1,1'-biphenyl) -4,4'-diamine (TPD) or 4,4'-bis [N - (naphthyl) -N-phenyl-amino] biphenyl (? -NPD), oxazole, oxadiazole, triazole, imidazole, imidazolone, stilbene derivatives, pyrazoline derivatives , 4,4 ', 4 "-tris (N- (3-methylphenyl) N-phenylamino) triphenylamine (m-MTDATA), polyphosphine, tetraphenyl There may be mentioned a porphyrin compound such as phophinic copper, phthalocyanine, copper phthalocyanine, and titanium phthalocyanine oxide, a triazole derivative, an oxadiazole derivative, an imidazole derivative, a polyarylalkane derivative, a pyrazolone derivative, Derivatives, phenylene diamine derivatives, anilamine derivatives, amino substituted chalcone derivatives, oxazole derivatives, styryl anthracene derivatives, fluoro And the like can be used as the polymer material. Examples of the polymer material include polymer materials such as phenylene vinylene, fluorene, carbazole, indole, pyrene, pyrrole, picoline, thiophene, acetylene, and diacetylene And a derivative thereof can be used as the hole transporting material of the present invention. A compound having sufficient hole transportability can be used even if it is not an electron donor compound. More specifically, the following compounds 1, 3, 4, and the like.

[Chemical Formula 5]

[Chemical Formula 6]

(7)

Hereinafter, a method of forming the layer containing the organic compound will be described.

The layer containing the organic compound can be formed by a dry film forming method or a wet film forming method. Specific examples of the dry film forming method include a physical vapor phase growth method such as a vacuum vapor deposition method, a sputtering method, an ion plating method and an MBE method, or a CVD method such as a plasma polymerization. As the wet film formation method, a cast method, a spin coat method, a dipping method, an LB method, or the like can be used.

When a polymer compound is used as at least one of a p-type semiconductor (compound) or an n-type semiconductor (compound), it is preferable to form a film by a wet film forming method which is easy to manufacture. In the case of using a dry film forming method such as vapor deposition, it is difficult to use a polymer because there is a risk of decomposition, and the oligomer can be preferably used instead. On the other hand, in the present invention, when a small molecule is used, a dry film forming method is preferably used, and a vacuum vapor deposition method is particularly preferably used. It is preferable that all processes at the time of vapor deposition are performed in a vacuum, and basically, the compound is not directly in contact with oxygen and moisture in the outside air. It is preferable to perform PI control or PID control of the deposition rate using a film thickness monitor such as a crystal oscillator or an interferometer. When two or more compounds are simultaneously deposited, a co-evaporation method, a flash evaporation method, or the like can be preferably used.

The upper electrode 112 is for increasing external quantum efficiency by increasing the absolute amount of light incident on the photoelectric conversion layer 108, and is composed of a transparent conductive film.

Preferred materials for the transparent conductive film are ITO, IZO, SnO ₂ , ATO (antimidodioxide tin oxide), ZnO, AZO (Al dope zinc oxide), GZO (gallium doped zinc oxide), TiO ₂ , Tin oxide, and tin oxide).

The light transmittance of the transparent electrode film is preferably 60% or more, more preferably 80% or more, more preferably 90% or more, and still more preferably 95% or more, in the visible light wavelength.

Generally, if the conductive thin film is made thinner than a predetermined range, an abrupt resistance value is increased. However, the sheet resistance of the transparent electrode film is preferably 100 Ω / □ or more and 10000 Ω / □ or less, and the flexibility of the film thickness range that can be made thin is large. Further, the thinner the thickness of the transparent electrode film, the smaller the amount of light absorbed, and the light transmittance generally increases. The increase of the light transmittance is highly preferable because it increases light absorption in the photoelectric conversion layer 108 and increases the photoelectric conversion ability. The film thickness of the transparent electrode film, that is, the upper electrode 112 is preferably 5 nm or more and 30 nm or less, more preferably 5 nm or more 20 nm or less.

As a method for manufacturing the upper electrode 112, various methods are used depending on the constituent material, and it is preferable to use the sputtering method.

The sealing layer 114 is a layer for preventing a factor that deteriorates an organic material such as water and oxygen from intruding into the photoelectric conversion layer 108 containing an organic material. The sealing layer 114 covers the lower electrode 104, the electron blocking layer 106, the photoelectric conversion layer 108, the intermediate layer 110, and the upper electrode 112, . The sealing layer 114 is required to have the following conditions.

First, when the sealing layer 114 is formed, the already formed photoelectric conversion layer 108 is not deteriorated.

Secondly, after fabrication of the photoelectric conversion element or the image pickup element, the penetration of a factor that deteriorates the organic photoelectric conversion material such as water molecules is prevented and the deterioration of the photoelectric conversion layer 108 .

Thirdly, in the manufacturing process of the imaging element after the sealing layer 114 is formed, the photoelectric conversion layer 108 is protected by inhibiting the penetration of a factor that deteriorates the organic photoelectric conversion material contained in solution, plasma, have.

Fourth, since the incident light reaches the photoelectric conversion layer 108 through the sealing layer 114, the sealing layer 114 must be transparent to the light of the wavelength detected by the photoelectric conversion layer 108.

The sealing layer 114 may be formed of a thin film made of a single material, but each layer may be provided with a multi-layered structure. A first sealing layer 116 that prevents penetration of a deterioration factor of a photoelectric conversion material such as water molecules and a second sealing layer 116 that prevents penetration of a deterioration factor such as water molecules are formed on the first sealing layer 116, Layered structure in which a sealing auxiliary layer 118 having a function that is difficult to achieve as the first sealing layer 116 is laminated on the first sealing layer 116. However, considering the manufacturing cost, it is preferable that the number of layers is as small as possible.

The sealing layer 114 can be formed, for example, as follows.

The organic photovoltaic conversion material is remarkably deteriorated in performance by the presence of deterioration factors such as water molecules. Therefore, it is necessary to seal and cover the entire photoelectric conversion layer with a dense metal oxide film, a metal nitride film, a metal nitride oxide film or the like that does not penetrate water molecules. Conventionally, various sealing films are formed by various vacuum film forming techniques using aluminum oxide, silicon oxide, silicon nitride or silicon oxynitride, a laminated structure of them, and a laminated structure of the organic polymer and the organic polymer as sealing layers. In the conventional sealing layer, it is difficult to grow the thin film because the steps become shadows in the step by the structure of the substrate surface, the micro-defect of the substrate surface, or the particles adhered to the surface of the substrate, The thickness is remarkably thinned. As a result, the step portion becomes a path through which the degradation factor penetrates. In order to completely cover the stepped portion with the sealing layer 114, it is necessary to form a film having a film thickness of at least 1 mu m in the flat portion so that the entirety of the sealing layer 114 becomes thick.

The atomic layer deposition (ALD) method is a kind of CVD method in which the adsorption and reaction of organic metal compound molecules, metal halide molecules, and metal hydride molecules to be a thin film material on the substrate surface and the unreacted Is repeated alternately to form a thin film. When the thin film material reaches the surface of the substrate, it is in the low molecular state, so that the thin film can grow if only a very small space into which small molecules can enter. This makes it possible to completely cover the step portion which has been difficult to achieve by the conventional thin film forming method, that is, the thickness of the thin film grown on the step portion is equal to the thickness of the thin film grown on the flat portion. The step difference due to the structure of the substrate surface, the micro-defect of the substrate surface, or the particles adhered to the substrate surface can be completely covered, so that the step portion does not become a path for the deterioration factor of the photoelectric conversion material. When the formation of the sealing layer 114 is performed by the atomic layer deposition (ALD) method, the thickness of the sealing layer can be effectively reduced more effectively than in the prior art.

When the sealing layer 114 is formed by the atomic layer deposition method, the material corresponding to the above-described preferable sealing layer can be appropriately selected. However, the organic photoelectric conversion material is limited to a material capable of growing a thin film at a relatively low temperature, which is not deteriorated. According to the atomic layer deposition method using an alkyl aluminum or a halogenated aluminum material, a dense aluminum oxide thin film can be formed at a temperature lower than 200 占 폚 at which the organic photoelectric conversion material does not deteriorate. Particularly, in the case of using trimethyl aluminum, it is preferable because an aluminum oxide thin film can be formed even at about 100 캜. Silicon oxide or titanium oxide is also preferable because a dense thin film can be formed as the sealing layer 114 at a temperature lower than 200 占 폚 like the aluminum oxide by appropriately selecting the material.

The sealing layer 114 preferably has a film thickness of 10 nm or more in order to sufficiently prevent the penetration of a factor that deteriorates the photoelectric conversion material such as water molecules. In the imaging device described later, if the thickness of the sealing layer is large, incident light is diffracted or diverged in the sealing layer, and color mixing occurs. For this reason, the film thickness of the sealing layer is preferably 200 nm or less.

The thin film formed by the atomic layer deposition method can attain a high quality thin film formation at low temperature comparatively in terms of step coverage and denseness. However, there are cases where the thin film is deteriorated by the chemical used in the photolithography process. For example, since the aluminum oxide thin film formed by the atomic layer deposition method is amorphous, the surface is eroded with an alkaline solution such as a developer and a peeling liquid. In such a case, a thin film excellent in chemical resistance is required on the aluminum oxide thin film formed by the atomic layer deposition method. That is, a sealing auxiliary layer that functions as a functional layer for protecting the sealing layer 114 is required. In this case, the sealing layer 114a having the two-layer structure shown in Fig. 1 (c) is formed as described above.

Next, a manufacturing method of the photoelectric conversion element 100 will be described.

First, as the lower electrode 104, for example, a TiN substrate having a TiN electrode formed on the surface 102a of the substrate 102 is prepared.

The TiN substrate is formed by depositing TiN as the lower electrode material on the surface 102a of the substrate 102 under a predetermined vacuum by the sputtering method and forming the TiN electrode as the lower electrode 104, for example.

Subsequently, an electron blocking material, for example, a carbazole derivative, and more preferably a bifluorene derivative is deposited on the lower electrode 104 under a predetermined vacuum using, for example, a vacuum deposition method An electron blocking layer 106 is formed.

Next, a p-type organic semiconductor material and a fullerene or a fullerene derivative, for example, as a photoelectric conversion material are co-deposited on the electron blocking layer 106 under a predetermined vacuum at a substrate temperature of 70 ° C or higher to form a photoelectric conversion layer (108). Thereby, crystallized fullerene or crystallized fullerene derivative can be obtained. In this case, it is preferable that the crystallized fullerene or the crystallized fullerene derivative is oriented in the (111) direction as described above.

Next, the intermediate layer 110 is formed on the photoelectric conversion layer 108 by, for example, depositing amorphous fullerene or an amorphous fullerene derivative under a predetermined vacuum at a substrate temperature of 20 ° C to 60 ° C. Thereby, an amorphous fullerene or an amorphous fullerene derivative can be obtained.

Next, an ITO film having a thickness of 5 to 30 nm is formed on the intermediate layer 110 by sputtering using, for example, ITO as a transparent conductive oxide. Thus, the upper electrode 112 made of a transparent conductive film is formed.

Next, an aluminum oxide layer, for example, is formed as an encapsulating layer 114 covering the lower electrode 104, the organic layer 120, and the upper electrode 112 using an atomic layer deposition (ALD) method.

In the photoelectric conversion element 100, when the photoelectric conversion element 100 is used, an external electric field can be applied. In this case, as the external electric field to be applied between the pair of electrodes in order to obtain excellent characteristics in the photoelectric conversion efficiency, the dark current and the light response speed, with the lower electrode 104 and the upper electrode 112 as a pair of electrodes, Is preferably 1 V / cm or more and 1 x 10 ⁷ V / cm or less, more preferably 1 x 10 ⁴ V / cm or more and 1 x 10 ⁷ V / cm or less. Particularly preferably 5 x 10 ⁴ V / cm or more and 1 x 10 ⁶ V / cm or less.

In the photoelectric conversion element 100, by providing the intermediate layer 110 including the amorphous fullerene or the amorphous fullerene derivative as described above, the photoelectric conversion efficiency can be increased and the dark current can be reduced.

Further, as described above, the photoelectric conversion efficiency can be improved by forming the photoelectric conversion layer 108 as a bulk hetero layer including crystallized fullerene or a crystallized fullerene derivative. Further, by orienting the crystallized fullerene or the crystallized fullerene derivative in the (111) direction as described above, further dark current can be suppressed.

Next, an image pickup device using the photoelectric conversion element 100 will be described.

2 (a) is a schematic cross-sectional view showing an image pickup device according to an embodiment of the present invention, and (b) is an enlarged view of a main part of an image pickup device according to an embodiment of the present invention.

The image pickup device 10 of the embodiment of the present invention can be used in an image pickup apparatus such as a digital camera and a digital video camera. Further, it can be mounted on an imaging module such as an electronic endoscope and a mobile phone.

The imaging device 10 shown in Fig. 2A converts a visible light image into an electric signal and includes a substrate 12, an insulating layer 14, a pixel electrode (lower electrode) 16, (Upper electrode) 26, the sealing layer 28, the color filter 32, the barrier ribs 34, the photoelectric conversion layer 22, the intermediate layer 24, the counter electrode A light-shielding layer 36, and an overcoat layer 38. The electron blocking layer 20, the photoelectric conversion layer 22 and the intermediate layer 24 are collectively referred to as an organic layer 30.

On the substrate 12, a read circuit 40 and a counter electrode voltage supply section 42 are formed.

The pixel electrode 16 corresponds to the lower electrode 104 of the photoelectric conversion element 100 described above and the counter electrode 26 corresponds to the upper electrode 112 of the photoelectric conversion element 100 described above, The organic layer 30 corresponds to the organic layer 120 of the photoelectric conversion element 100 and the sealing layer 28 corresponds to the sealing layer 114 of the photoelectric conversion element 100 described above.

As the substrate 12, for example, a glass substrate or a semiconductor substrate such as Si is used. On the substrate 12, an insulating layer 14 made of a known insulating material is formed. In the insulating layer 14, a plurality of pixel electrodes 16 are formed on the surface 14a. The pixel electrodes 16 are arranged in a one-dimensional or two-dimensional shape, for example.

A first connecting portion 44 for connecting the pixel electrode 16 and the reading circuit 40 is formed in the insulating layer 14. [ Further, a second connecting portion 46 for connecting the counter electrode 26 and the counter electrode voltage supplying portion 42 is formed. The second connection portion 46 is formed at a position not connected to the pixel electrode 16 and the organic layer 30. The first connecting portion 44 and the second connecting portion 46 are formed of a conductive material.

A wiring layer 48 made of a conductive material for connecting the reading circuit 40 and the counter electrode voltage supply portion 42 to the outside of the imaging element 10 is provided inside the insulating layer 14, Respectively.

The circuit board 11 is formed with the pixel electrodes 16 connected to the respective first connection portions 44 on the surface 14a of the insulating layer 14 on the substrate 12 as described above. The circuit board 11 is also referred to as a CMOS substrate.

The electron blocking layer 20 is formed on the pixel electrode 16 so as to cover the plurality of pixel electrodes 16 while avoiding the second connecting portions 46. The photoelectric conversion A layer 22 is formed. An intermediate layer 24 is formed on the photoelectric conversion layer 22.

The electron blocking layer 20 corresponds to the electron blocking layer 106 of the photoelectric conversion element 100 as described above and suppresses injection of electrons from the pixel electrode 16 into the photoelectric conversion layer 22 Lt; / RTI >

Since the photoelectric conversion layer 22 and the intermediate layer 24 correspond to the photoelectric conversion layer 108 and the intermediate layer 110 of the photoelectric conversion element 100 described above, detailed description thereof will be omitted. The photoelectric conversion layer 22 is a bulk hetero layer in which a p-type organic semiconductor (organic p-type compound) and a crystallized fullerene or a crystallized fullerene derivative are mixed.

If the electron blocking layer 20, the photoelectric conversion layer 22, and the intermediate layer 24 are all formed on the pixel electrode 16, the film thickness may not be constant.

The counter electrode 26 is an electrode facing the pixel electrode 16 and is provided so as to cover the organic layer 30 and the organic layer 30 is disposed between the pixel electrode 16 and the counter electrode 26 .

The counter electrode 26 is composed of a transparent conductive film with respect to incident light L (visible light) in order to make light incident on the photoelectric conversion layer 22. [ The counter electrode 26 is electrically connected to the second connection portion 46 disposed outside the photoelectric conversion layer 22 and is connected to the counter electrode voltage supply portion 42 through the second connection portion 46 .

Since the counter electrode 26 can be made of the same material as the upper electrode 112, a detailed description thereof will be omitted.

Similarly to the upper electrode 112, the counter electrode 26 preferably has a light transmittance of 60% or more, more preferably 80% or more, more preferably 90% or more, and still more preferably 90% It is more than 95%.

It is preferable that the counter electrode 26 has a thickness of 5 to 30 nm as in the case of the upper electrode 112. By setting the thickness of the counter electrode 26 to 5 nm or more, the intermediate layer 24 as a lower layer can be sufficiently coated, and a uniform performance can be obtained. On the other hand, if the thickness of the counter electrode 26 is set to a thickness exceeding 30 nm, the counter electrode 26 and the pixel electrode 16 are locally short-circuited, and the dark current may rise. By setting the thickness of the counter electrode 26 to 30 nm or less, occurrence of local short circuit can be suppressed.

The film thickness of the counter electrode 26 is a distance from the surface 24a of the intermediate layer 24 to the surface 26a of the counter electrode 26 of the organic layer 30 in the stacking direction m, The thickness of the portion connected to the second connecting portion 46 is not included.

2 (b), when the film thickness of the intermediate layer 24 is t _a and the film thickness of the counter electrode 26 is t _b , the photoelectric conversion element It is preferable that the film thickness t _a of the intermediate layer 24 is equal to or greater than 1/3 of the film thickness t _b of the counter electrode 26 and the upper limit is equal to the film thickness t _b ) or less. That is, the thickness (t _a) of the intermediate layer 24 is preferably a _{1 / 3t b ≤t a ≤t b} .

The film thickness t _a of the intermediate layer 24 corresponds to the film thickness t ₁ of the intermediate layer 110 of the photoelectric conversion element 100 and the film thickness t _b of the counter electrode 26 corresponds to and the photoelectric conversion element 100 corresponding to the thickness (t ₂₎ of the upper electrode 112.

The counter electrode voltage supply section 42 applies a predetermined voltage to the counter electrode 26 through the second connection section 46. When the voltage to be applied to the counter electrode 26 is higher than the power supply voltage of the image pickup device 10, the power supply voltage is boosted by a boost circuit such as a charge pump to supply the predetermined voltage.

The pixel electrode 16 is a charge collecting electrode for collecting charges generated in the photoelectric conversion layer 22 between the pixel electrode 16 and the counter electrode 26 opposed thereto. The pixel electrode 16 is connected to the readout circuit 40 through the first connecting portion 44. [ The readout circuit 40 is provided on the substrate 12 in correspondence with each of the plurality of pixel electrodes 16 and reads signals corresponding to the charges collected by the corresponding pixel electrodes 16. [

Since the pixel electrode 16 can be made of the same material as the lower electrode 104, a detailed description thereof will be omitted.

A step corresponding to the film thickness of the pixel electrode 16 may be steeper at the end of the pixel electrode 16 or a remarkable unevenness may exist at the surface of the pixel electrode 16, Particles are adhered to the pixel electrode 16, the layer on the pixel electrode 16 becomes thinner than a desired film thickness or cracks occur. If the counter electrode 26 is formed on the layer in such a state, a pixel defect such as an increase in dark current or a short circuit occurs due to contact between the pixel electrode 16 and the counter electrode 26 at the defective portion and electric field concentration do. Further, the above-described defects may lower the adhesion between the pixel electrode 16 and the layer thereon and the heat resistance of the imaging element 10.

In order to prevent the above defects and improve the reliability of the device, it is preferable that the surface roughness Ra of the pixel electrode 16 is 0.6 nm or less. The smaller the surface roughness of the pixel electrode 16, the smaller the unevenness of the surface, and the better the surface flatness is. In order to remove particles on the pixel electrode 16, it is particularly preferable to clean the pixel electrode 16 or the like by using a general cleaning technique used in a semiconductor manufacturing process before forming the electron blocking layer 20 Do.

The reading circuit 40 is composed of, for example, a CCD, a MOS circuit or a TFT circuit, and is shielded by a light shielding layer (not shown) provided in the insulating layer 14. [ It is preferable that the reading circuit 40 employs a CCD or CMOS circuit for general image sensor use, and it is preferable to use a CMOS circuit from the viewpoint of noise and high speed.

Although not shown, for example, a high concentration n region surrounded by a p region is formed on the substrate 12, and the first connection portion 44 is connected to the n region. A read circuit 40 is provided in the p region. The n region functions as a charge accumulating portion for accumulating charges of the photoelectric conversion layer 22. [ the signal charge accumulated in the n region is converted into a signal corresponding to the amount of charge by the reading circuit 40 and outputted to the outside of the imaging element 10 through the wiring layer 48, for example.

The sealing layer 28 is for protecting the photoelectric conversion layer 22 from deterioration factors such as water molecules. The sealing layer 28 is formed on the surface 14a of the insulating layer 14 so as to cover the entire surface 28a of the counter electrode 26. [ The sealing layer 28 can be formed of the same material as that of the sealing layer 114 of the photoelectric conversion element 100 and can be formed by the same manufacturing method, and a detailed description thereof will be omitted.

If the distance between the color filter 32 and the photoelectric conversion layer 22, that is, the thickness of the sealing layer 28, is large in the imaging element 10 having a pixel size of less than 2 m, especially about 1 m, 28, the incident light L is diffracted or diverged, resulting in color mixing. Thus, the imaging element 10 having a pixel size of about 1 mu m requires a sealing layer material in which the device performance is not deteriorated even if the film thickness of the entire sealing layer 28 is reduced, and a manufacturing method thereof. For example, by forming the sealing layer 28 with an aluminum oxide thin film formed by the above-described atomic layer deposition method, deterioration of element performance can be suppressed even if the film thickness is reduced.

The color filter 32 is formed on the surface 28a of the sealing layer 28 at a position facing each pixel electrode 16. [ The barrier ribs 34 are provided between the color filters 32 on the surface 28a of the sealing layer 28 to improve the light transmission efficiency of the color filters 32. [ The light shielding layer 36 is formed in a region other than the region (effective pixel region) provided with the color filter 32 and the partition wall 34 on the surface 28a of the sealing layer 28 and the photoelectric conversion layer 22 from entering. The color filter 32, the partition wall 34, and the light shielding layer 36 are formed to have substantially the same thickness, for example, through a photolithography process, and further, a resin firing process.

The overcoat layer 38 is for protecting the color filter 32 from a post-process or the like and is formed so as to cover the color filter 32, the partition wall 34, and the light shielding layer 36.

In the image pickup device 10, the pixel electrode 16 provided above the organic layer 30, the counter electrode 26 and the color filter 32, and one pixel electrode Px.

As the overcoat layer 38, a polymer material such as an acrylic resin, a polysiloxane resin, a polystyrene resin and a fluorine resin, and an inorganic material such as silicon oxide and silicon nitride can be suitably used. The overcoat layer 38 can be formed using a known one used for the organic solid-state image pickup device.

When the photosensitive resin such as polystyrene type is used, since the overcoat layer 38 can be patterned by the photolithography method, the peripheral light-shielding layer on the bonding pad, the sealing layer, the insulating layer, and the like can be used as the photoresist And the overcoat layer 38 itself can be easily processed as a microlens. On the other hand, it is also possible to use the overcoat layer 38 as an antireflection layer and to form various kinds of low refractive index materials used as the partition walls 34 of the color filter 32. The overcoat layer 38 may have a two-layer structure or a combination of the above materials in order to function as a protective layer for a post-process and to function as an antireflection layer.

Although the pixel electrode 16 is formed on the surface 14a of the insulating layer 14 in the present embodiment, the present invention is not limited to this, and the pixel electrode 16 may be formed on the surface 14a of the insulating layer 14 . Further, the second connection unit 46 and the counter electrode voltage supply unit 42 are provided in a single configuration, but a plurality of them may be provided. For example, by supplying a voltage from the both ends of the counter electrode 26 to the counter electrode 26, the voltage drop at the counter electrode 26 can be suppressed. The number of sets of the second connection unit 46 and the counter electrode voltage supply unit 42 may be appropriately increased or decreased in consideration of the chip area of the device.

Next, a manufacturing method of the imaging element 10 according to the embodiment of the present invention will be described.

FIGS. 3A to 3C are schematic sectional views showing a manufacturing method of an image pickup device according to an embodiment of the present invention in the order of steps. FIGS. 4A to 4C are cross- 3 (a) and 3 (b) are schematic cross-sectional views showing the manufacturing method of the device in the order of process, and show the later process of FIG. 3 (c).

3 (a), on the substrate 12 on which the readout circuit 40 and the counter electrode voltage supplying section 42 are formed, The first connecting portion 44 and the second connecting portion 46 and the insulating layer 14 provided with the wiring layer 48 are formed on the surface 14a of the insulating layer 14 and the first connecting portions 44 (CMOS substrate) on which the pixel electrode 16 connected to the pixel electrode 16 is formed. In this case, as described above, the first connecting portion 44 and the reading circuit 40 are connected, and the second connecting portion 46 and the counter electrode voltage supplying portion 42 are connected. The pixel electrode 16 is formed of, for example, TiN.

Next, the film is transported in a film forming chamber (not shown) of the electron blocking layer 20 through a predetermined transport path so that all the pixels except for the second connecting portion 46, as shown in Fig. 3 (b) An electron blocking material is deposited to cover the electrode 16 using a vacuum deposition method, for example, under a predetermined vacuum to form the electron blocking layer 20. [ As the electron blocking material, for example, a carbazole derivative, more preferably a bifluorene derivative, is used.

3 (c), on the surface 20a of the electron blocking layer 20, a photoelectric conversion layer 22 is formed on the surface of the photoelectric conversion layer 22, As the conversion material, for example, a p-type organic semiconductor material and a fullerene or a fullerene derivative are co-deposited under a predetermined vacuum at a substrate temperature of 70 ° C or higher to form the photoelectric conversion layer 22. Thereby, crystallized fullerene or crystallized fullerene derivative can be obtained. In this case, it is preferable that the crystallized fullerene or the crystallized fullerene derivative is oriented in the (111) direction with respect to the direction perpendicular to the surface 16a of the pixel electrode 16, as described above.

4A, the surface 22a of the photoelectric conversion layer 22 is transferred to a film formation chamber (not shown) of the intermediate layer 24 by a predetermined transport path, for example, , An amorphous fullerene or an amorphous fullerene derivative is deposited under a predetermined vacuum at a substrate temperature of 20 ° C to 60 ° C to form an intermediate layer 24. Thus, the organic layer 30 in which the electron blocking layer 20, the photoelectric conversion layer 22, and the intermediate layer 24 are laminated is formed in the stacking direction m.

4 (b), the intermediate layer 24 and the photoelectric conversion layer 22 are covered, and then, the intermediate layer 24 and the photoelectric conversion layer 22 are formed, The counter electrode 26 is formed in a pattern formed on the second connecting portion 46 at a thickness of 5 to 30 nm under a predetermined vacuum by using, for example, ITO for the counter electrode material, using a sputtering method .

Next, as shown in Fig. 4 (c), the entire surface 26a of the counter electrode 26 is covered so as to be transported to a film formation chamber (not shown) of the sealing layer 28 through a predetermined transport path An aluminum oxide layer, for example, is formed as the sealing layer 28 on the surface 14a of the insulating layer 14 by using an atomic layer deposition (ALD) method.

Next, a color filter 32, a partition wall 34 and a light shielding layer 36 are formed on the surface 28a of the sealing layer 28 by using, for example, photolithography. The color filter 32, the partition wall 34, and the light shielding layer 36 can be formed using a known one used in the organic solid-state image pickup device. The process of forming the color filter 32, the partition wall 34, and the light shielding layer 36 may be non-vacuum.

Next, the overcoat layer 38 is formed by, for example, a coating method so as to cover the color filter 32, the partition wall 34, and the light shielding layer 36. [ Thus, the imaging element 10 shown in Fig. 2 (a) can be formed. Further, the step of forming the overcoat layer 38 may be non-vacuum.

In the image pickup device 10, when the image pickup device 10 is used, an external electric field can be applied. In this case, as the external electric field to be applied between the pair of electrodes in order to obtain excellent characteristics in the photoelectric conversion efficiency, the dark current and the light response speed using the pixel electrode 16 and the counter electrode 26 as a pair of electrodes, Is preferably 1 V / cm or more and 1 x 10 ⁷ V / cm or less, more preferably 1 x 10 ⁴ V / cm or more and 1 x 10 ⁷ V / cm or less. Particularly preferably 5 x 10 ⁴ V / cm or more and 1 x 10 ⁶ V / cm or less.

Also in the image pickup device 10, by providing the intermediate layer 24 including amorphous fullerene or an amorphous fullerene derivative, the photoelectric conversion efficiency can be increased and the dark current can be reduced. Further, as described above, the photoelectric conversion efficiency can be improved by forming the photoelectric conversion layer 22 into a bulk hetero layer including crystallized fullerene or crystallized fullerene derivative. Further, by orienting the crystallized fullerene or the crystallized fullerene derivative in the (111) direction as described above, further dark current can be suppressed.

The present invention is basically configured as described above. The photoelectric conversion element and the image pickup element of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various modifications or changes may be made without departing from the gist of the present invention to be.

Example

Hereinafter, the effects of providing the intermediate layer in the present invention will be described in detail.

In this example, the photoelectric conversion elements of Examples 1 to 16 and Comparative Examples 1 to 3 were fabricated, and the dark current and the relative sensitivity were measured for the photoelectric conversion elements of Examples 1 to 16 and Comparative Examples 1 to 3 . The measurement results are shown in Table 2 below. The structure of the photoelectric conversion element is the structure shown in Fig. 1 and is a structure of the lower electrode / electron blocking layer / photoelectric conversion layer / intermediate layer / upper electrode / sealing layer formed on the substrate.

With respect to the dark current, an electric field of 2 x 10 ⁵ V / cm was applied to the upper electrode side in the state of shielding the photoelectric conversion element, and the electric current of the photoelectric conversion element measured using a source meter (6430 manufactured by Keithley) Was set as a dark current.

As for the relative sensitivity, the value of the external quantum efficiency at the maximum sensitivity wavelength when the electric field of 2 x 10 ⁵ V / cm was applied to each of the photoelectric conversion elements of Examples 1 to 16 and Comparative Examples 1 to 3 was measured. The value of the external quantum efficiency of the photoelectric conversion element of Example 3 was taken as 1 and the value of each external quantum efficiency was taken as the relative sensitivity.

The value of the external quantum efficiency is obtained by applying an external electric field of 2 x 10 ⁵ V / cm to the counter electrode and measuring the current value obtained when the light of an intensity of 50 μW / cm ² is irradiated from the upper electrode side of the photoelectric conversion element .

Hereinafter, the photoelectric conversion elements of Examples 1 to 16 and Comparative Examples 1 to 3 will be described.

(Example 1)

In the first embodiment, an electron blocking layer, a photoelectric conversion layer, an intermediate layer, an upper electrode, and a sealing layer are formed in this order. The lower electrode is formed of TiN. The electron blocking layer is formed by vacuum evaporation of the organic compound represented by the compound 1 to a film thickness of 50 nm. The photoelectric conversion layer was formed by depositing a mixed film (Compound 2: fullerene C ₆₀ = 1: 3 (volume ratio)) of an organic compound represented by Compound 2 and fullerene C ₆₀ (represented by C ₆₀ in Table 2 below) In a thickness of 400 nm by co-deposition. The middle layer, the fullerene C _60, at a substrate temperature of 10 ℃, by vacuum deposition to form a film thickness of 15nm. The film formation of the organic compound was performed at a degree of vacuum of 5.0 x 10 < ^-4 > Pa or less and at a deposition rate of 3 angstroms / s. ITO was formed by DC sputtering to a film thickness of 15 nm on the upper electrode. As the sealing layer, aluminum oxide was formed to have a thickness of 100 nm by atomic layer deposition.

The ionization potential of Compound 1 is 5.65 eV, and the ionization potential of Compound 2 is 5.55 eV.

(Example 2)

(Compound 2: fullerene C ₆₀ = 1: 2 (volume ratio)) of an organic compound represented by compound 2 and compound fullerene C ₆₀ (compound 2: fullerene C ₆₀ = 1: 2 (volume ratio)) as a middle layer was formed into a film thickness of 15 nm , A photoelectric conversion element was fabricated in the same manner as in Example 1.

(Example 3)

(Compound 1: fullerene C ₆₀ = 1: 1 (volume ratio)) of the organic compound represented by the compound 1 and the fullerene C ₆₀ (volume ratio) of the organic compound represented by the compound 1 was coevaporated at a substrate temperature of 30 캜 in vacuum to form a film thickness of 25 nm , A photoelectric conversion element was fabricated in the same manner as in Example 1.

(Example 4)

(Compound 1: fullerene C ₆₀ = 1: 1 (volume ratio)) of the organic compound represented by the compound 1 and the fullerene C ₆₀ (volume ratio) of the organic compound represented by the compound 1 was coevaporated at a substrate temperature of 30 캜 in vacuum to form a film thickness of 20 nm , A photoelectric conversion element was fabricated in the same manner as in Example 1.

(Example 5)

(Compound 1: fullerene C ₆₀ = 1: 1 (volume ratio)) of the organic compound represented by the compound 1 and the fullerene C ₆₀ (volume ratio) were co-deposited as a middle layer in a vacuum at a substrate temperature of 30 캜 in a vacuum of 15 nm , A photoelectric conversion element was fabricated in the same manner as in Example 1.

(Example 6)

(Compound 1: fullerene C ₆₀ = 1: 1 (volume ratio)) of the organic compound represented by the compound 1 and the fullerene C ₆₀ represented by the compound 1 as the intermediate layer was co-deposited in vacuum at a substrate temperature of 30 캜 in a vacuum of 10 nm , A photoelectric conversion element was fabricated in the same manner as in Example 1.

(Example 7)

(Compound 1: fullerene C ₆₀ = 1: 1 (volume ratio)) of the organic compound represented by the compound 1 and the fullerene C ₆₀ (the volume ratio of fullerene C ₆₀ ) was coacially deposited at a substrate temperature of 30 캜 in vacuum by a co- , A photoelectric conversion element was fabricated in the same manner as in Example 1.

(Example 8)

(Compound 1: fullerene C ₆₀ = 1: 1 (volume ratio)) of the organic compound represented by the compound 1 and the fullerene C ₆₀ (volume ratio)) was co-deposited at a substrate temperature of 30 캜 in a vacuum by co- , A photoelectric conversion element was fabricated in the same manner as in Example 1.

(Example 9)

(Compound 4: fullerene C ₆₀ = 1: 1 (volume ratio)) of the organic compound represented by the compound 4 and the fullerene C ₆₀ (compound 4: fullerene C ₆₀ = 1: 1 (volume ratio)) as the intermediate layer was co- , A photoelectric conversion element was fabricated in the same manner as in Example 1.

(Example 10)

As an intermediate layer, a mixed layer of an organic compound and a fullerene C ₆₀ represented by Compound 4 (Compound 4: fullerene C ₆₀ = 1: 1 (volume ratio)) to, at a substrate temperature of 30 ℃, by co-deposition in a vacuum, the film thickness of 15nm , A photoelectric conversion element was fabricated in the same manner as in Example 1.

(Example 11)

The organic compound represented by the intermediate layer of the compound 1 and fullerene C ₆₀ mixed film (Compound 1: fullerene C ₆₀ = 1 1 (volume ratio)), at a substrate temperature of 30 ℃, by co-deposition in a vacuum, to a thickness of 20nm . A photoelectric conversion element was produced in the same manner as in Example 1 except that the ITO film was formed to have a thickness of 20 nm by DC sputtering as the upper electrode.

(Example 12)

The organic compound represented by the intermediate layer of the compound 1 and fullerene C ₆₀ mixed film (Compound 1: fullerene C ₆₀ = 1 1 (volume ratio)), at a substrate temperature of 30 ℃, by co-deposition in a vacuum, to a thickness of 10nm . A photoelectric conversion element was produced in the same manner as in Example 1 except that the ITO film was formed to have a thickness of 20 nm by DC sputtering as the upper electrode.

(Example 13)

The organic compound represented by the intermediate layer of the compound 1 and fullerene C ₆₀ mixed film (Compound 1: fullerene C ₆₀ = 1 1 (volume ratio)), at a substrate temperature of 30 ℃, by co-deposition in a vacuum, to a thickness of 5nm . A photoelectric conversion element was produced in the same manner as in Example 1 except that the ITO film was formed to have a thickness of 20 nm by DC sputtering as the upper electrode.

(Example 14)

The photoelectric conversion layer was formed by co-evaporation in a vacuum at a substrate temperature of 130 占 폚 in a mixed film of an organic compound represented by compound 2 and fullerene C ₆₀ (compound 2: fullerene C ₆₀ = 1: 3 (volume ratio) . The organic compound represented by the intermediate layer of the compound 1 and fullerene C ₆₀ mixed film (Compound 1: fullerene C ₆₀ = 1 1 (volume ratio)), at a substrate temperature of 30 ℃, by co-deposition in a vacuum, to a thickness of 10nm . A photoelectric conversion element was produced in the same manner as in Example 1 except that the ITO film was formed to have a thickness of 20 nm by DC sputtering as the upper electrode.

(Example 15)

The photoelectric conversion layer was formed by co-evaporation in a vacuum at a substrate temperature of 130 占 폚 in a mixed film of an organic compound represented by compound 2 and fullerene C ₆₀ (compound 2: fullerene C ₆₀ = 1: 3 (volume ratio) . The organic compound represented by the intermediate layer of the compound 1 and fullerene C ₆₀ mixed film (Compound 1: fullerene C ₆₀ = 1 1 (volume ratio)), at a substrate temperature of 30 ℃, by co-deposition in a vacuum, to a thickness of 5nm . A photoelectric conversion element was produced in the same manner as in Example 1 except that the ITO film was formed to have a thickness of 20 nm by DC sputtering as the upper electrode.

(Example 16)

Mixed layer of the photoelectric conversion layer, the organic compound and the fullerene C ₆₀ represented by Compound 2 (Compound 2: fullerene C ₆₀ = 1: 1 (volume ratio)) to, at a substrate temperature of 90 ℃, by co-deposition in vacuo, 400nm in film . The organic compound represented by the intermediate layer of the compound 1 and fullerene C ₆₀ mixed film (Compound 1: fullerene C ₆₀ = 1 1 (volume ratio)), at a substrate temperature of 30 ℃, by co-deposition in a vacuum, to a thickness of 15nm A photoelectric conversion element was fabricated in the same manner as in Example 1.

(Comparative Example 1)

A photoelectric conversion element was produced in the same manner as in Example 1 except that no intermediate layer was formed.

(Comparative Example 2)

The photoelectric conversion layer was formed by using a mixed film of an organic compound represented by Compound 2 and fullerene C ₆₀ (Compound 2: fullerene C ₆₀ = 1: 3 (volume ratio)) at 30 ° C substrate temperature, A photoelectric conversion element was produced in the same manner as in Example 1 except that the film was formed to a thickness of 400 nm by vapor deposition.

(Comparative Example 3)

The photoelectric conversion layer was formed by using a mixed film of an organic compound represented by Compound 2 and fullerene C ₆₀ (compound 2: fullerene C ₆₀ = 1: 3 (volume ratio)) at a substrate temperature of 130 ° C, A photoelectric conversion element was produced in the same manner as in Example 1 except that the film was formed to a thickness of 400 nm by vapor deposition.

[Chemical Formula 8]

In the present embodiment, the X-ray diffraction measurement of the fullerene C ₆₀ and fullerene C ₆₀ mixed films formed under the respective conditions was carried out using an X-ray diffraction apparatus (2? -Theta method) to check the presence or absence of crystallization. A specimen in which fullerene C ₆₀ and a fullerene C ₆₀ mixed film formed on the substrate were set under the respective conditions was set so that? = 0 ° was in the horizontal direction of the substrate, and? = 90 ° was perpendicular to the substrate.

When fullerene C ₆₀ is crystallized, a diffraction pattern from (111) in the vicinity of 11 °, a diffraction pattern from (222) in the vicinity of 22 °, and a diffraction pattern from (220) in the vicinity of 18 ° are observed. When fullerene C ₆₀ is oriented in the (111) direction, a diffraction pattern from (111) or (222) is observed, but a diffraction pattern from (220) is not observed. The evaluation results are shown in Table 1.

[Table 1]

[Table 2]

As shown in Table 2, in Comparative Example 2 in which fullerene C ₆₀ of the photoelectric conversion layer is amorphous, Examples 1 to 16 and Comparative Examples 1 and 3 in which the photoelectric conversion layer is crystallized have improved photoelectric conversion efficiency. However, in Comparative Examples 1 and 3 in which there is no intermediate layer, the dark current greatly increases as compared with Examples 1 to 16.

Further, in Comparative Example 1, dark current is large even in Examples 2 to 10 in which the thickness of the upper electrode is the same. In Comparative Example 3, the dark current is large compared with Examples 14 and 15 of crystallization (no orientation). In Example 15, the dark current is smaller than that in Comparative Example 3, even though the thickness of the intermediate layer is less than 1/3 of the thickness of the upper electrode.

Compared with Example 1, the dark current in Example 5 is further lowered. Comparing Examples 3 to 8, it is found that dark currents are further lowered as the thickness of the intermediate layer is thicker. However, even when the film thickness of the intermediate layer is thicker than the film thickness of 15 nm of the upper electrode, The result was no.

When the film thickness of the intermediate layer is increased, the external voltage required for applying the same electric field intensity to the photoelectric conversion element becomes higher. Therefore, it is preferable that the film thickness is thinner within a range in which the effect of lowering the dark current is sufficiently obtained. desirable.

In Examples 8 and 13, the dark current is higher than that in Examples 5 and 11, and the effect of lowering the dark current is sufficiently obtained. The film thickness of the intermediate layer is preferably at least 1/3 of the film thickness of the upper electrode .

In comparison between Examples 5, 10, and 16 in which the upper electrode and the intermediate layer have the same structures, in Example 16, the ratio of the crystallized fullerene C ₆₀ was larger than that in Examples 5 and 10, but both the dark current and the relative sensitivity were equal.

10 image pickup element
12, 102 substrate
14 insulating layer
16 pixel electrode
20, 106 electron blocking layer
22, 108 photoelectric conversion layer
24, 110 intermediate layer
26 counter electrode
28, 114 sealing layer
40 Readout circuit
42 Opposite electrode voltage supply unit
44 first connection portion
46 second connection portion
100 photoelectric conversion element
104 lower electrode
112 upper electrode

Claims (9)

A lower electrode,
An electron blocking layer stacked on the lower electrode,
A photoelectric conversion layer stacked on the blocking layer,
An intermediate layer stacked on the photoelectric conversion layer,
And an upper electrode stacked on the intermediate layer,
The photoelectric conversion layer is a bulk hetero layer in which a p-type organic semiconductor is mixed with a crystallized fullerene or a crystallized fullerene derivative,
Wherein the intermediate layer comprises an amorphous fullerene or an amorphous fullerene derivative,
Wherein the upper electrode is made of a transparent conductive film. The method according to claim 1,
Wherein the photoelectric conversion layer is composed of the p-type organic semiconductor and a bulk hetero layer formed by mixing fullerene or crystallized fullerene derivative oriented in the (111) direction perpendicular to the surface of the lower electrode. The method according to claim 1 or 2,
Wherein the photoelectric conversion layer contains crystallized fullerene or a crystallized fullerene derivative in a ratio of 30% to 80%. The method according to any one of claims 1 to 3,
Wherein the thickness of the intermediate layer is 1/3 or more of the thickness of the upper electrode. The method according to any one of claims 1 to 4,
And the thickness of the intermediate layer is not more than the thickness of the upper electrode. The method according to any one of claims 1 to 5,
Wherein the intermediate layer further comprises at least one kind of organic material. The method according to any one of claims 1 to 6,
Wherein the intermediate layer is a layer in which the amorphous fullerene or the amorphous fullerene derivative is mixed with a transparent hole transporting material having an ionization potential of 5.5 eV or more. The method according to any one of claims 1 to 7,
Wherein the upper electrode is made of ITO, and the thickness of the upper electrode is 5 to 30 nm. An imaging device comprising a photoelectric conversion element according to any one of claims 1 to 8.

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