JP2017073426A - Imaging element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging element with improved photoelectric conversion efficiency in a red wavelength band.SOLUTION: An imaging element includes: a first electrode; a first red organic photoelectric conversion film disposed on one surface side of the first electrode and containing boron subnaphthalocyanine chloride; a second electrode disposed on the side opposite to the first electrode with respect to the first red organic photoelectric conversion film; a power supply including a positive electrode connected to the first electrode and a negative electrode connected to the second electrode; and a signal reading unit connected to the first electrode and the second electrode and reading an electric charge generated in photoelectric conversion in the first red organic photoelectric conversion film as an imaging signal. The first electrode or the second electrode is a transparent electrode, and light is made incident from the transparent electrode side to the first red organic photoelectric conversion film.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image sensor.

  2. Description of the Related Art Conventionally, there is an imaging device having an organic photoelectric conversion film sandwiched between at least two electrodes, the organic photoelectric conversion film containing a quinacridone derivative or a quinazoline derivative (for example, a patent) Reference 1).

JP 2006-1000076 A1

  However, since organic photoelectric conversion films containing a quinacridone derivative or a quinazoline derivative mainly improve the photoelectric conversion efficiency in the blue-green wavelength band, conventional image sensors have a photoelectric conversion efficiency in the red wavelength band. There is room for improvement.

  An object of the present invention is to provide an imaging device with improved photoelectric conversion efficiency in the red wavelength band.

  An image pickup device according to an embodiment of the present invention includes a first electrode, a first red organic photoelectric conversion film disposed on one surface side of the first electrode, and containing boron subnaphthalocyanine chloride; A second electrode, a positive electrode connected to the first electrode, and a second electrode disposed on the opposite side to the first electrode with respect to the first red organic photoelectric conversion film A power source having a negative electrode; and a signal reading unit that is connected to the first electrode and the second electrode and reads a charge generated by photoelectric conversion in the first red organic photoelectric conversion film as an imaging signal; One electrode or the second electrode is a transparent electrode, and light enters the first red organic photoelectric conversion film from the transparent electrode side.

  An imaging device with improved photoelectric conversion efficiency in the red wavelength band can be provided.

2 is a diagram illustrating a cross-sectional configuration of an image sensor 50 according to Embodiment 1. FIG. 4 is a diagram illustrating an example of ideal spectral characteristics of the image sensor 50. FIG. 3 is a diagram illustrating a configuration of a photoelectric conversion unit 100R according to an example of Embodiment 1. FIG. It is a figure which shows the wavelength characteristic of the external quantum efficiency obtained with the photoelectric conversion part 100R of FIG. It is a figure which shows the wavelength characteristic of the external quantum efficiency of the photoelectric conversion part 100R with respect to the output voltage of the power supply 160. FIG. It is a figure which shows the wavelength characteristic of the external quantum efficiency of the photoelectric conversion part 100R with respect to the film thickness of the organic photoelectric conversion film 130R, and the output voltage of the power supply 160. FIG. 6 is a diagram illustrating a configuration of a photoelectric conversion unit 200R according to an example of Embodiment 2. FIG. It is a figure which shows the wavelength characteristic of the external quantum efficiency obtained with the photoelectric conversion part 200R of FIG.

  Embodiments to which the image sensor of the present invention is applied will be described below.

<Embodiment 1>
FIG. 1 is a diagram illustrating a cross-sectional configuration of the image sensor 50 according to the first embodiment. FIG. 2 is a diagram illustrating an example of ideal spectral characteristics of the image sensor 50.

  The image sensor 50 includes glass substrates 10R, 10G, and 10B, TFT (Thin Film Transistor) readout circuits 20R, 20G, and 20B, a photoelectric conversion unit 100R, a photoelectric conversion unit 100G, and a photoelectric conversion unit 100B. As the reading circuit, not only the TFT but also a transistor using bulk Si or SOI (Silicon on Insulator) may be used.

  These components are in the order of the glass substrate 10R, the TFT readout circuit 20R, the photoelectric conversion unit 100R, the glass substrate 10G, the TFT readout circuit 20G, the photoelectric conversion unit 100G, the glass substrate 10B, the TFT readout circuit 20B, and the photoelectric conversion unit 100B. Are stacked. In order to eliminate the influence of defocusing of the optical image due to the separation between the layers of the photoelectric conversion units 100R, 100G, and 100B, the glass substrates 10G and 10B are made of, for example, a thin interlayer insulating film (silicon oxide of about 100 nm to 10 μm). It is desirable that the photoelectric conversion portions 100R, 100G, and 100B be arranged close to each other using a metal oxide such as silicon nitride, metal nitride, or an organic insulator material.

  In FIG. 1, light enters the image sensor 50 from the upper side as indicated by an arrow. In the following, for convenience of explanation, the light incident side in FIG. 1 is referred to as the upper side, and the side opposite to the light incident side is referred to as the lower side. However, this hierarchical relationship is merely for convenience of explanation and does not represent a universal hierarchical relationship.

  The glass substrate 10B, the TFT readout circuit 20B, and the photoelectric conversion unit 100B constitute an imaging unit having photosensitivity for blue of the three primary colors of light. The glass substrate 10G, the TFT readout circuit 20G, and the photoelectric conversion unit 100G construct an imaging unit that has photosensitivity in green among the three primary colors of light. In addition, the glass substrate 10R, the TFT readout circuit 20R, and the photoelectric conversion unit 100R construct an imaging unit having photosensitivity in red among the three primary colors of light.

  As an example, the spectral characteristics of the image sensor 50 are as shown in FIG. In FIG. 2, the horizontal axis represents the wavelength (nm), and the vertical axis represents the response signal amount with respect to the light of the photoelectric conversion units 100B, 100G, and 100R in arbitrary units (A.U.).

  As shown in FIG. 2, the spectral sensitivity (blue) of the photoelectric conversion unit 100B is in the range of about 400 nm to about 520 nm. The spectral sensitivity (green) of the photoelectric conversion unit 100G ranges from about 460 nm to about 620 nm. The spectral sensitivity (red) of the photoelectric conversion unit 100R ranges from about 535 nm to about 700 nm, and the wavelength that gives the peak value (maximum value) of the spectral sensitivity is about 600 nm.

  The image pickup device 50 according to the first embodiment is obtained by optimizing the photoelectric conversion unit 100R having spectral sensitivity in red. Therefore, hereinafter, the photoelectric conversion unit 100R will be described mainly.

  Next, details of each component shown in FIG. 1 will be described. First, the glass substrate 10R, the TFT readout circuit 20R, and the photoelectric conversion unit 100R will be described.

  The glass read-out circuit 20R is formed on one surface (upper surface in FIG. 1) of the glass substrate 10R. In FIG. 1, the imaging device 50 is shown in a simplified manner, but the glass substrate 10 </ b> R is a rectangular glass substrate when viewed from the incident direction of light (in plan view), and corresponds to a plurality of pixels arranged in a matrix. Has a region.

  The TFT readout circuit 20R is disposed on one surface (the upper surface in FIG. 1) of the glass substrate 10R, and has a plurality of regions that are divided corresponding to the pixels. The TFT readout circuit 20R reads out the electric charge output by the photoelectric conversion unit 100R as an imaging signal for each pixel.

  The photoelectric conversion unit 100R includes an anode 110R, a hole injection block layer 120R, an organic photoelectric conversion film 130R, an electron injection block layer 140R, and a cathode 150R. Although not shown in FIG. 1, a direct current power source is connected between the anode 110R and the cathode 150R. The positive terminal of the DC power supply is connected to the anode 110R, and the negative terminal is connected to the cathode 150R.

  The anode 110R is an electrode that extracts electrons out of charges generated in the organic photoelectric conversion film 130R. The anode 110R is an example of a first electrode.

  The anode 110R is composed of a transparent electrode or a non-transparent electrode. Examples of the transparent electrode include indium zinc oxide (IZO), indium tin oxide, indium oxide, tin oxide, and zinc oxide.

  If it is not a transparent electrode, metals such as aluminum, vanadium, gold, silver, platinum, iron, cobalt, carbon, nickel, tungsten, palladium, magnesium, calcium, tin, lead, titanium, yttrium, lithium, ruthenium, manganese, And these alloys can be used.

  The hole injection block layer 120R is disposed on the anode 110R. The hole injection block layer 120R can be formed of, for example, tris (8-quinolinolato) aluminum (Alq3). The hole injection blocking layer 120R suppresses injection of holes from the anode 110R to the organic photoelectric conversion film 130R, and causes electrons to flow out from the organic photoelectric conversion film 130R to the anode 110R.

  The organic photoelectric conversion film 130R is disposed on the hole injection block layer 120R. The organic photoelectric conversion film 130R uses a boron subnaphthalocyanine chloride (SubNc) film.

  Boron subnaphthalocyanine chloride (SubNc) film is known to be an ambipolar organic semiconductor molecule that has both an electron-accepting donor property and an electron-accepting property. It has the property of efficiently transporting both charge pairs generated by dissociation of excitons generated in a naphthalocyanine chloride (SubNc) film, that is, electrons and holes.

  Such a boron subnaphthalocyanine chloride (SubNc) film has been found to have spectral sensitivity in red of the three primary colors of light depending on the film thickness or applied voltage. Details of this will be described later with reference to FIGS.

  In addition, although the organic photoelectric converting film 130R demonstrates the form comprised by a boron sub naphthalocyanine chloride (SubNc) film | membrane (one layer) here, the organic photoelectric converting film 130R is a boron sub naphthalocyanine chloride (SubNc) film | membrane. In addition, a film having another composition may be included, or a film in which an organic material having another composition is mixed with boron subnaphthalocyanine chloride (SubNc) may be used.

  The electron injection block layer 140R is disposed on the organic photoelectric conversion film 130R. The electron injection blocking layer 140R can be formed of Spiro-2CBP (2,7-Bis (9-carbazolyl) -9,9-spirobifluorene). The electron injection block layer 140R suppresses injection of electrons from the cathode 150R to the organic photoelectric conversion film 130R, and allows holes to flow out from the organic photoelectric conversion film 130R to the cathode 150R.

  The cathode 150R is an electrode that extracts holes out of charges generated in the organic photoelectric conversion film 130R. The cathode 150R is an example of a second electrode.

  Since the cathode 150R is closer to the light incident side than the organic photoelectric conversion film 130R, the cathode 150R is formed of a transparent electrode. Examples of the transparent electrode include indium zinc oxide (IZO), indium tin oxide, indium oxide, tin oxide, and zinc oxide.

  Note that the photoelectric conversion unit 100R having the above-described configuration includes, for example, a TFT readout circuit 20R formed on a glass substrate 10R using a semiconductor manufacturing technology, an anode 110R, a hole injection block layer 120R, an organic The photoelectric conversion film 130R, the electron injection blocking layer 140R, and the cathode 150R can be formed by sequentially vapor-depositing or the like.

  Next, the glass substrate 10G, the TFT readout circuit 20G, and the photoelectric conversion unit 100G will be described.

  As for glass substrate 10G, TFT read-out circuit 20G is formed in one surface (upper surface in Drawing 1). The glass substrate 10G may be the same as the glass substrate 10R.

  The TFT readout circuit 20G is disposed on one surface (upper surface in FIG. 1) of the glass substrate 10G. As the TFT readout circuit 20G, the same one as the TFT readout circuit 20R may be used.

  The photoelectric conversion unit 100G includes an anode 110G, a hole injection block layer 120G, an organic photoelectric conversion film 130G, an electron injection block layer 140G, and a cathode 150G. These are superposed in this order. Although not shown in FIG. 1, a direct current power source is connected between the anode 110G and the cathode 150G. The positive terminal of the DC power supply is connected to the anode 110G, and the negative terminal is connected to the cathode 150G.

  The anode 110G and the cathode 150G may be composed of transparent electrodes used for the anode 110R and the cathode 150R, respectively.

  The hole injection block layer 120G is disposed on the anode 110G, and may be formed of, for example, a phenanthroline compound, an aluminum quinoline compound, an oxadiazole compound, a silole compound, or the like.

  The organic photoelectric conversion film 130G is disposed on the hole injection block layer 120G, and may be formed of, for example, a quinacridone compound (electron donating material) and a perylene compound (electron accepting material).

  The electron injection block layer 140G is disposed on the organic photoelectric conversion film 130G and may be formed of, for example, a triphenylamine compound or the like.

  Such a photoelectric conversion unit 100G has a spectral sensitivity corresponding to green in the range of about 460 nm to about 620 nm shown in FIG.

  Next, the glass substrate 10B, the TFT readout circuit 20B, and the photoelectric conversion unit 100B will be described.

  In the glass substrate 10B, a TFT readout circuit 20B is formed on one surface (the upper surface in FIG. 1). The glass substrate 10B may be the same as the glass substrate 10R.

  The TFT readout circuit 20B is disposed on one surface (the upper surface in FIG. 1) of the glass substrate 10B. As the TFT readout circuit 20B, the same one as the TFT readout circuit 20R may be used.

  The photoelectric conversion unit 100B includes an anode 110B, a hole injection block layer 120B, an organic photoelectric conversion film 130B, an electron injection block layer 140B, and a cathode 150B. These are superposed in this order. Although not shown in FIG. 1, a direct current power source is connected between the anode 110B and the cathode 150B. The positive terminal of the DC power supply is connected to the anode 110B, and the negative terminal is connected to the cathode 150B.

  The anode 110B and the cathode 150B may be composed of transparent electrodes used for the anode 110R and the cathode 150R, respectively.

  The hole injection block layer 120B is disposed on the anode 110B and may be formed of, for example, a phenanthroline compound, an aluminum quinoline compound, an oxadiazole compound, a silole compound, or the like.

  The organic photoelectric conversion film 130B is disposed on the hole injection block layer 120B, and may be formed of, for example, a coumarin compound (electron donating material) and a silole compound (electron accepting material).

  The electron injection block layer 140B is disposed on the organic photoelectric conversion film 130B and may be formed of, for example, a triphenylamine compound.

  Such a photoelectric conversion unit 100B has a spectral sensitivity corresponding to blue in the range of about 400 nm to about 520 nm shown in FIG.

  Note that, here, a description has been given of a mode in which the TFT read circuits 20R, 20G, and 20B are provided in the photoelectric conversion units 100B, 100G, and 100R, respectively, but a single TFT read circuit is provided below the photoelectric conversion unit 100R to provide photoelectric conversion. It may be connected to the conversion units 100B, 100G, and 100R with vias or the like, and image signals obtained by the photoelectric conversion units 100B, 100G, and 100R may be read out.

  FIG. 3 is a diagram illustrating a configuration of the photoelectric conversion unit 100R according to an example of the first embodiment.

  FIG. 3 shows a photoelectric conversion unit 100R formed on a glass substrate 30 in the order of a cathode 150R, an electron injection block layer 140R, an organic photoelectric conversion film 130R, a hole injection block layer 120R, and an anode 110R. Light is incident from below as indicated by arrows. In FIG. 3, the positive terminal of the power supply 160 is connected to the anode 110R, and the negative terminal is connected to the cathode 150R.

  As the anode 110R, the hole injection block layer 120R, the organic photoelectric conversion film 130R, the electron injection block layer 140R, and the cathode 150R, the following conditions were used. Here, the cathode 150R, the electron injection block layer 140R, the organic photoelectric conversion film 130R, the hole injection block layer 120R, and the anode 110R will be described in this order.

  As the cathode 150R, an IZO (indium oxide / zinc oxide composite) (registered trademark) thin film previously formed on the glass substrate 30 was used. The film thickness of the cathode 150R is 150 nm.

  On such a cathode 150R, an electron injection block layer 140R, an organic photoelectric conversion film 130R, a hole injection block layer 120R, and an anode 110R were sequentially formed by a vacuum deposition method.

  The electron injection block layer 140R is made of Spiro-2CBP (2,7-Bis (9-carbazolyl) -9,9-spirobifluorene) and has a film thickness of 30 nm. The organic photoelectric conversion film 130R is made of boron subnaphthalocyanine chloride (SubNc) and has a film thickness of 50 nm. The hole injection blocking layer 120R is made of tris (8-quinolinolato) aluminum (Alq3) and has a film thickness of 30 nm. The anode 110R is a thin film made of aluminum and has a thickness of 50 nm.

A voltage was applied from the power source 160 between the anode 110R and the cathode 150R of the photoelectric conversion unit 100R thus produced, and light was irradiated to measure the external quantum efficiency. The irradiation light was monochromatic light having a wavelength range of 320 nm to 800 nm, and the output was constant at 50 μW / cm ² .

  FIG. 4 is a diagram illustrating the wavelength characteristics of the external quantum efficiency obtained by the photoelectric conversion unit 100R of FIG. The horizontal axis represents wavelength (nm) and the vertical axis represents external quantum efficiency (%). The voltage applied between the anode 110R and the cathode 150R from the power supply 160 was set to 15V. In the following, boron subnaphthalocyanine chloride is referred to as SubNc.

  As shown in FIG. 4, it was found that the photoelectric conversion unit 100R using a 50 nm SubNc film as the organic photoelectric conversion film 130R has a large spectral sensitivity in a wavelength band of about 550 nm to about 730 nm. This is a wavelength band corresponding to red in the three primary colors of light.

The peak value of the external quantum efficiency was about 80%, and it was confirmed that it operates as a highly efficient red organic photoelectric conversion film. Further, the dark current value when the output voltage of the power supply 160 was set to 15 V was 20 nA / cm ² , and a sufficiently low value that can be used as the image sensor 50 was obtained.

  Further, when the output voltage of the power supply 160 was changed, the wavelength characteristic of the external quantum efficiency as shown in FIG. 5 was obtained.

  FIG. 5 is a diagram illustrating the wavelength characteristics of the external quantum efficiency of the photoelectric conversion unit 100R with respect to the output voltage of the power supply 160.

  FIG. 5 shows a characteristic (solid line) in which a voltage of 20 V is applied from the power supply 160 and a voltage of 15 V from the power supply 160 to the photoelectric conversion unit 100R including the organic photoelectric conversion film 130R having a SubNc film thickness of 100 nm. The characteristic (dashed line) and the characteristic (dot-dash line) which applied the voltage of 10V from the power supply 160 are shown.

  As shown in FIG. 5, it was found that the external quantum efficiency increases as the voltage of the power supply 160 increases. When the voltage of the power supply 160 is changed, the wavelength that gives the peak value of the external quantum efficiency changes somewhat, but the shape of the characteristics is almost the same. The wavelengths giving the peak value of the external quantum efficiency are all around 600 nm, and it has been found that the wavelength gradually shifts to the longer wavelength side as the voltage of the power supply 160 increases.

  From the above results, it was found that the external quantum efficiency greatly depends on the applied voltage of the SubNc film, and that the external quantum efficiency increases when the applied voltage is increased from 10V to 20V. It was also found that the distribution of the external quantum efficiency with respect to the wavelength hardly changed, but the wavelength giving the peak value gradually shifted to the longer wavelength side as the applied voltage increased.

  Moreover, when the photoelectric conversion part 100R from which the film thickness of the SubNc film | membrane used as the organic photoelectric conversion film 130R differs was produced and the output voltage of the power supply 160 was changed, the wavelength characteristic of the external quantum efficiency as shown in FIG. 6 was obtained. .

  FIG. 6 is a diagram illustrating the wavelength characteristics of the external quantum efficiency of the photoelectric conversion unit 100R with respect to the film thickness of the organic photoelectric conversion film 130R and the output voltage of the power supply 160.

  FIG. 6 shows the characteristic (solid line) of applying a voltage of 20 V from the power supply 160 with the thickness of the SubNc film (organic photoelectric conversion film 130R) being 100 nm and the thickness of the SubNc film (organic photoelectric conversion film 130R) being 50 nm. The characteristics (dashed line) when a voltage of 15 V is applied from the power source 160 and the characteristics (dotted line) where the film thickness of the SubNc film (organic photoelectric conversion film 130R) is 50 nm and a voltage of 10 V is applied from the power source 160 are shown. .

  As shown in FIG. 6, it was found that the wavelength that gives the peak value of the external quantum efficiency changes according to the thickness of the SubNc film and the voltage of the power supply 160. When the film thickness was 100 nm and the applied voltage was 20 V, a peak value of about 85% was obtained at about 600 nm.

  When the film thickness was 50 nm and the applied voltage was 15 V, a peak value of about 80% was obtained at about 670 nm. This characteristic is the same as that shown in FIG. Further, when the film thickness was 50 nm and the applied voltage was 10 V, a peak value of about 72% was obtained at about 670 nm.

  From the above results, it was found that the wavelength giving the peak value of the external quantum efficiency greatly depends on the thickness of the SubNc film.

  Therefore, when the organic photoelectric conversion film 130 </ b> R is used for the image sensor 50, the film thickness of the organic photoelectric conversion film 130 </ b> R is set so that the red external quantum efficiency peak value matches the characteristics of the red spectral sensitivity of the image sensor 50. Should be set.

  Further, in the characteristics shown in FIG. 6, when a SubNc film (broken line) having a film thickness of 50 nm and an applied voltage of 15 V is compared with a SubNc film (dotted line) having a film thickness of 50 nm and an applied voltage of 10 V, Both wavelength bands are about 550 nm to about 730 nm.

  On the other hand, the external quantum efficiency of the SubNc film (solid line) having a film thickness of 100 nm and an applied voltage of 20 V is increased by about 550 nm, and the wavelength band for red is expanded. From this result, it was found that the wavelength band width for red can be set by changing the thickness of the SubNc film.

  Therefore, when the organic photoelectric conversion film 130 </ b> R is used for the image sensor 50, the thickness of the organic photoelectric conversion film 130 </ b> R is set so that the red wavelength band matches the characteristics of the red spectral sensitivity of the image sensor 50. Good.

  As described above, according to the first embodiment, the SubNc film is used as the organic photoelectric conversion film 130R for red, and the hole injection block layer 120R and the electron injection block layer 140R are provided on both sides of the organic photoelectric conversion film 130R. The photoelectric conversion unit 100R having a very high photoelectric conversion efficiency in the red wavelength band can be realized.

  In addition, the blue photoelectric conversion unit 100B and the green photoelectric conversion unit 100G each include the organic photoelectric conversion film 130B and the organic photoelectric conversion film 130G having the above-described composition, so that very high photoelectric conversion is performed. It has been found that efficiency can be obtained.

As such a high-efficiency blue photoelectric conversion unit 100B, a mixed film of coumarin 30 or a coumarin derivative sensitive to blue light and an electron transporting organic material is used, and as a green photoelectric conversion unit 100G, green light is converted into green light. A mixed film of sensitive quinacridone or a quinacridone derivative and an electron-transporting organic material can be given, and both can achieve high photoelectric conversion efficiency of 60% or more. As the electron transporting organic material to be mixed, materials suitable for blue and green can be selected. Each The HOMO level and the LUMO level of the electron transporting organic material is less desirably than the HOMO level and the LUMO level of the organic molecules of the photoelectric conversion unit 100B or 100G, e.g. fullerene _{C 60, C 70,} fullerene derivatives, tris ( 8-quinolinolato) aluminum (Alq3) and the like. In order to reduce dark current, 100B and an electron / hole blocking layer may be combined.

  For this reason, according to Embodiment 1, the photoelectric conversion efficiency is increased by providing the red photoelectric conversion unit 100R on the blue photoelectric conversion unit 100B and the green photoelectric conversion unit 100G as described above. An improved imaging device 50 can be provided.

  In addition, by providing the hole injection block layer 120R and the electron injection block layer 140R on both sides of the organic photoelectric conversion film 130R, the dark current can be greatly reduced, so that the image pickup device in which noise due to the dark current is greatly reduced 50 can be provided.

  In the above description, the mode in which light enters the photoelectric conversion units 100B, 100G, and 100R from the cathodes 150B, 150G, and 150R side has been described. May be incident. In this case, the anode 110R may be configured with a transparent electrode, and the cathode 150R may be a non-transparent electrode.

<Embodiment 2>
FIG. 7 is a diagram illustrating a configuration of a photoelectric conversion unit 200R according to an example of the second embodiment.

  The imaging device of the second embodiment is obtained by replacing the photoelectric conversion unit 100R of the first embodiment with a photoelectric conversion unit 200R. The photoelectric conversion unit 200R includes an anode 110R, an organic photoelectric conversion film 230R, and a cathode 150R. The photoelectric conversion unit 200R has a configuration in which the organic photoelectric conversion film 130R of Embodiment 1 is replaced with the organic photoelectric conversion film 230R, and the hole injection block layer 120R and the electron injection block layer 140R are removed.

  FIG. 7 shows a photoelectric conversion unit 200R formed on the glass substrate 30 in the order of the cathode 150R, the organic photoelectric conversion film 230R, and the anode 110R. Light is incident from below as indicated by arrows. In FIG. 7, the positive terminal of the power supply 160 is connected to the anode 110R, and the negative terminal is connected to the cathode 150R.

  As the organic photoelectric conversion film 230R, a film under the following conditions was used. Note that the anode 110R and the cathode 150R are the same as the anode 110R and the cathode 150R of the photoelectric conversion unit 100R of Embodiment 1, and thus description thereof is omitted.

  As the organic photoelectric conversion film 230R, a zinc phthalocyanine (ZnPc) film and a boron subnaphthalocyanine chloride (SubNc) film were used. In the following, zinc phthalocyanine is referred to as ZnPc and boron subnaphthalocyanine chloride is referred to as SubNc.

  The organic photoelectric conversion film 230R was produced by sequentially forming a ZnPc film and a SubNc film on the cathode 150R by a vacuum deposition method. Both the ZnPc film and the SubNc film have a thickness of 50 nm.

A voltage was applied from the power source 160 between the anode 110R and the cathode 150R of the photoelectric conversion unit 200R thus produced, and the light was irradiated to measure the external quantum efficiency. As in the first embodiment, the irradiation light is monochromatic light having a wavelength range of 320 nm to 800 nm, and the output is constant at 50 μW / cm ² .

  FIG. 8 is a diagram illustrating the wavelength characteristics of the external quantum efficiency obtained by the photoelectric conversion unit 200R of FIG. The horizontal axis represents wavelength (nm) and the vertical axis represents external quantum efficiency (%). The voltage applied between the anode 110R and the cathode 150R from the power supply 160 was set to 2V.

  As shown in FIG. 8, it was found that the photoelectric conversion unit 200R using the 50 nm ZnPc film and the 50 nm SubNc film as the organic photoelectric conversion film 230R has spectral sensitivity in a wavelength band of about 550 nm to about 730 nm. This is a wavelength band corresponding to red in the three primary colors of light.

  The peak value of external quantum efficiency was about 30%. For comparison, an organic photoelectric conversion film having only a ZnPc film having a thickness of 100 nm was prepared, and the external quantum efficiency was measured in the same manner. As a result, the peak value was about 8%.

  For this reason, it was found that adding the SubNc film to the ZnPc film significantly improves the external quantum efficiency. The external quantum efficiency is lower than that of the organic photoelectric conversion film 130R of the first embodiment because the voltage applied to the organic photoelectric conversion film 230R is low and the hole injection block layer 120R and the electron injection block layer 140R are It seems to be due to not including.

Further, in the photoelectric conversion unit 200R using the 50 nm ZnPc film and the 50 nm SubNc film as the organic photoelectric conversion film 230R, the dark current when the output voltage of the power supply 160 was 2 V was 82 nA / cm ² .

  It has been found that when the voltage of the power supply 160 is further increased, the dark current increases rapidly. For this reason, it has been found that when the output voltage of the power supply 160 is, for example, 5 V or more, it is better to provide the hole injection block layer 120R and the electron injection block layer 140R.

  By the way, it has been found that the wavelength characteristics of the external quantum efficiency shown in FIG. 8 have a small hill-like characteristic in the range of about 530 nm to about 600 nm as compared with the characteristics shown in FIG.

  Further, the characteristics such as a small hill in the range of about 530 nm to about 600 nm are the characteristics (dashed line) of applying 15 V to the SubNc film (50 nm) shown in FIG. 6 of the first embodiment, and the SubNc film ( It does not occur in the characteristics (one-dot chain line) in which 10 V is applied to (50 nm).

  As can be seen from the comparison between the characteristic (dashed line) obtained by applying 15 V to the SubNc film (50 nm) shown in FIG. 6 of the first embodiment and the characteristic (dashed line) obtained by applying 10 V to the SubNc film (50 nm). The peak of the external quantum efficiency of the SubNc film having a thickness of 50 nm is about 670 nm.

  Therefore, the peak obtained at about 670 nm in FIG. 8 is considered to be obtained by the SubNc film (50 nm) in the organic photoelectric conversion film 230R.

  On the other hand, it has been found that ZnPc has a characteristic in which a peak value of external quantum efficiency exists around 600 nm.

  Therefore, in the wavelength characteristic of the external quantum efficiency shown in FIG. 8, the characteristics such as a small hill in the range of about 530 nm to about 600 nm are obtained by the ZnPc film (50 nm) in the organic photoelectric conversion film 230R. Conceivable.

  As described above, according to the second embodiment, it was found that the external quantum efficiency can be significantly improved by using the organic photoelectric conversion film 230R having a configuration in which the SubNc film is added to the ZnPc film.

  It was also found that the distribution of the wavelength characteristics of the external quantum efficiency can be adjusted by using a ZnPc film and a SubNc film having different wavelengths that cause the peak value of the external quantum efficiency. That is, when the external quantum efficiency is not improved by the ZnPc film alone, the external quantum efficiency can be greatly improved by adding the SubNc film. If the external quantum efficiency distribution includes a wavelength region that cannot be covered only by the SubNc film, the external quantum efficiency can be improved by adding a ZnPc film.

  As described above, according to the second embodiment, the photoelectric conversion efficiency in the red wavelength band is improved by using the organic photoelectric conversion film in which the ZnPc film and the SubNc film are stacked as the organic photoelectric conversion film 230R for red. Part 200R can be realized.

  In addition, by providing the blue photoelectric conversion unit 100B and the green photoelectric conversion unit 100G with the red photoelectric conversion unit 200R, an imaging element with improved photoelectric conversion efficiency can be provided.

  Examples of the red photoelectric conversion unit 200R include phthalocyanine derivatives, anthraquinone derivatives, triphenylmethane derivatives, and pyrazolopyrimidine derivatives.

  The image pickup device according to the exemplary embodiment of the present invention has been described above, but the present invention is not limited to the specifically disclosed embodiment, and does not depart from the scope of the claims. Various modifications and changes are possible.

10R, 10G, 10B Glass substrate 20R, 20G, 20B TFT readout circuit 100R, 100G, 100B Photoelectric conversion unit 110R, 110G, 110B Anode 120R, 120G, 120B Hole injection block layer 130R, 130G, 130B Organic photoelectric conversion film 140R, 140G, 140B Electron injection block layer 150R, 150G, 150B Cathode 200R Photoelectric conversion unit 230R Organic photoelectric conversion film

Claims (6)

A first electrode;
A first red organic photoelectric conversion film disposed on one side of the first electrode and containing boron subnaphthalocyanine chloride;
A second electrode disposed on a side opposite to the first electrode with respect to the first red organic photoelectric conversion film;
A power source having a positive electrode connected to the first electrode and a negative electrode connected to the second electrode;
A signal reading unit connected to the first electrode and the second electrode, and reading a charge generated by photoelectric conversion in the first red organic photoelectric conversion film as an imaging signal,
The imaging device, wherein the first electrode or the second electrode is a transparent electrode, and light enters the first red organic photoelectric conversion film from the transparent electrode side. A hole injection blocking layer disposed between the first red organic photoelectric conversion film and the first electrode;
The imaging device according to claim 1, further comprising: an electron injection block layer disposed between the first red organic photoelectric conversion film and the second electrode.   The imaging device according to claim 1, wherein a wavelength that gives a peak of red spectral sensitivity of the first red organic photoelectric conversion film is set by a film thickness of the first red organic photoelectric conversion film.   The imaging device according to claim 1 or 2, wherein a wavelength band of red spectral sensitivity of the first red organic photoelectric conversion film is set by a film thickness of the first red organic photoelectric conversion film.   Between the first electrode and the first red organic photoelectric conversion film or between the first red organic photoelectric conversion film and the second electrode and containing zinc phthalocyanine; The imaging device according to claim 1, further comprising a red organic photoelectric conversion film.   The imaging element according to claim 5, wherein a wavelength giving a spectral sensitivity peak of the second red organic photoelectric conversion film is different from a wavelength giving a spectral sensitivity peak of the first red organic photoelectric conversion film.

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