JP6646995B2 - Image sensor - Google Patents

Description

  The present invention relates to an image sensor.

  BACKGROUND ART Conventionally, there is an imaging device having an organic photoelectric conversion film sandwiched between at least two electrodes, wherein the organic photoelectric conversion film contains a quinacridone derivative or a quinazoline derivative. Reference 1).

JP 2006-100767 A

  However, since an organic photoelectric conversion film containing a quinacridone derivative or a quinazoline derivative mainly improves the photoelectric conversion efficiency in the blue-green wavelength band, the conventional imaging device has a photoelectric conversion efficiency in the red wavelength band. There is room for improvement.

  Therefore, it is an object 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 of the first red organic photoelectric conversion film from the first electrode; A power supply having a negative electrode; and a signal reading unit connected to the first electrode and the second electrode, the signal reading unit reading an electric charge generated by photoelectric conversion in the first red organic photoelectric conversion film as an imaging signal, and The first electrode or the second electrode is a transparent electrode, and light is incident on the first red organic photoelectric conversion film from the transparent electrode side, and the red spectral sensitivity peak of the first red organic photoelectric conversion film is reduced . The wavelength to be given is the first red organic photoelectric conversion film. It is set by the thickness.

  An image sensor having improved photoelectric conversion efficiency in the red wavelength band can be provided.

FIG. 2 is a diagram illustrating a cross-sectional configuration of an image sensor 50 according to the first embodiment. FIG. 4 is a diagram illustrating an example of ideal spectral characteristics of the imaging element 50. FIG. 2 is a diagram illustrating a configuration of a photoelectric conversion unit 100R according to an example of the first embodiment. FIG. 4 is a diagram illustrating wavelength characteristics of external quantum efficiency obtained by the photoelectric conversion unit 100R in FIG. 3. FIG. 9 is a diagram illustrating a wavelength characteristic of an external quantum efficiency of the photoelectric conversion unit 100R with respect to an output voltage of the power supply 160. FIG. 9 is a diagram illustrating wavelength characteristics of the external quantum efficiency of the photoelectric conversion unit 100R with respect to the thickness of the organic photoelectric conversion film 130R and the output voltage of the power supply 160. FIG. 13 is a diagram illustrating a configuration of a photoelectric conversion unit 200R according to an example of the second embodiment. FIG. 8 is a diagram illustrating wavelength characteristics of external quantum efficiency obtained by the photoelectric conversion unit 200R in FIG. 7.

  Hereinafter, embodiments to which the image pickup device of the present invention is applied will be described.

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

  The imaging device 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 read circuit, not only a TFT but also a transistor using bulk Si or SOI (Silicon on Insulator) may be used.

  These components are in the order of glass substrate 10R, TFT readout circuit 20R, photoelectric conversion unit 100R, glass substrate 10G, TFT readout circuit 20G, photoelectric conversion unit 100G, glass substrate 10B, TFT readout circuit 20B, and photoelectric conversion unit 100B. Stacked. In order to eliminate the influence of defocusing of the optical image caused by the separation between the photoelectric conversion units 100R, 100G, and 100B, the glass substrates 10G and 10B are formed with a thin interlayer insulating film (silicon oxide, for example, about 100 nm to 10 μm). And a metal oxide such as silicon nitride, a metal nitride, or an organic insulator material), and the photoelectric conversion units 100R, 100G, and 100B are desirably disposed close to each other.

  In FIG. 1, light is incident on the image sensor 50 from above as indicated by the arrow. In the following, for convenience of description, the light incident side in FIG. 1 is referred to as an upper side, and the side opposite to the light incident side is referred to as a 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 form an imaging unit having photosensitivity to blue of the three primary colors of light. The glass substrate 10G, the TFT readout circuit 20G, and the photoelectric conversion unit 100G constitute an imaging unit that has photosensitivity to green among the three primary colors of light. Further, the glass substrate 10R, the TFT readout circuit 20R, and the photoelectric conversion unit 100R form an imaging unit having photosensitivity to red light among the three primary colors of light.

  The spectral characteristics of the image sensor 50 are as shown in FIG. 2 as an example. In FIG. 2, the horizontal axis represents the wavelength (nm), and the vertical axis represents the response signal amount 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 ranges from 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 is in a range from about 535 nm to about 700 nm, and the wavelength giving the peak value (maximum value) of the spectral sensitivity is about 600 nm.

  The imaging device 50 of the first embodiment is obtained by optimizing the photoelectric conversion unit 100R having the red spectral sensitivity. Therefore, hereinafter, the photoelectric conversion unit 100R will be mainly described.

  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.

  On the glass substrate 10R, a TFT readout circuit 20R is formed on one surface (the upper surface in FIG. 1). Although the imaging device 50 is simplified in FIG. 1, the glass substrate 10 </ b> R is a rectangular glass substrate when viewed from the light incident direction (in a plan view), and corresponds to a plurality of pixels arranged in a matrix. With regions.

  The TFT readout circuit 20R is provided on one surface (upper surface in FIG. 1) of the glass substrate 10R, and has a plurality of regions divided corresponding to pixels. The TFT readout circuit 20R reads out the electric charge that is photoelectrically converted and 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 DC power supply 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 from the charges generated in the organic photoelectric conversion film 130R. The anode 110R is an example of a first electrode.

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

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

  The organic photoelectric conversion film 130R is provided on the hole injection block layer 120R. As the organic photoelectric conversion film 130R, a boron subnaphthalocyanine chloride (SubNc) film is used.

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

  It has been found that such a boron subnaphthalocyanine chloride (SubNc) film has a spectral sensitivity to red light among the three primary colors of light depending on the film thickness or applied voltage. The details will be described later with reference to FIGS.

  Here, an embodiment in which the organic photoelectric conversion film 130R is configured by a boron subnaphthalocyanine chloride (SubNc) film (one layer) will be described. In addition to the above, 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 provided on the organic photoelectric conversion film 130R. The electron injection block layer 140R may 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 from the organic photoelectric conversion film 130R to the cathode 150R.

  The cathode 150R is an electrode for extracting holes from the charges generated in the organic photoelectric conversion film 130R. The cathode 150R is an example of a second electrode.

  Since the cathode 150R is on the light incident side of the organic photoelectric conversion film 130R, it is formed of a transparent electrode. Examples of the transparent electrode include an indium oxide / zinc oxide composite (IZO), indium tin oxide, indium oxide, tin oxide, zinc oxide, and the like.

  The photoelectric conversion unit 100R having the above-described configuration includes, for example, a TFT readout circuit 20R formed on a glass substrate 10R by using a semiconductor manufacturing technique, and an anode 110R, a hole injection block layer 120R, It can be manufactured by forming the photoelectric conversion film 130R, the electron injection block layer 140R, and the cathode 150R 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.

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

  The TFT readout circuit 20G is provided on one surface (upper surface in FIG. 1) of the glass substrate 10G. As the TFT read circuit 20G, the same one as the TFT read 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 superimposed in this order. Although not shown in FIG. 1, a DC power supply 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 provided on the anode 110G, and may be formed of, for example, a phenanthroline-based compound, an aluminum quinoline-based compound, an oxadiazole-based compound, a silole-based compound, or the like.

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

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

  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.

  The TFT reading circuit 20B is formed on one surface (the upper surface in FIG. 1) of the glass substrate 10B. The same thing as the glass substrate 10R may be used as the glass substrate 10B.

  The TFT read circuit 20B is provided on one surface (the upper surface in FIG. 1) of the glass substrate 10B. As the TFT read circuit 20B, the same one as the TFT read 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 superimposed in this order. Although not shown in FIG. 1, a DC power supply 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 provided on the anode 110B, and may be formed of, for example, a phenanthroline-based compound, an aluminum quinoline-based compound, an oxadiazole-based compound, a silole-based compound, or the like.

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

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

  Here, the mode in which the TFT readout circuits 20R, 20G, and 20B are provided in the photoelectric conversion units 100B, 100G, and 100R, respectively, has been described. The conversion units 100B, 100G, and 100R may be connected to each other with vias or the like, and image signals obtained by the photoelectric conversion units 100B, 100G, and 100R may be read.

  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 enters from below, as indicated by the 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.

  The following conditions were used 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. 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 formed in advance on the glass substrate 30 was used. The 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 thickness of 30 nm. The organic photoelectric conversion film 130R is made of boron subnaphthalocyanine chloride (SubNc) and has a thickness of 50 nm. The hole injection block layer 120R is made of tris (8-quinolinolato) aluminum (Alq3) and has a 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 supply 160 between the anode 110R and the cathode 150R of the thus-manufactured photoelectric conversion unit 100R, irradiated with light, and the external quantum efficiency was measured. 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 a wavelength characteristic of the external quantum efficiency obtained by the photoelectric conversion unit 100R in FIG. The horizontal axis indicates the wavelength (nm), and the vertical axis indicates the external quantum efficiency (%). The voltage applied between the anode 110R and the cathode 150R from the power supply 160 was set to 15V. Hereinafter, boron subnaphthalocyanine chloride is referred to as SubNc.

  As shown in FIG. 4, it was found that the photoelectric conversion unit 100R using the 50 nm SubNc film as the organic photoelectric conversion film 130R has a large spectral sensitivity in a wavelength band from 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 the film operates as a highly efficient organic photoelectric conversion film for red. When the output voltage of the power supply 160 was set to 15 V, the dark current value was 20 nA / cm ² , and a sufficiently low value usable as the image sensor 50 was obtained.

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

  FIG. 5 is a diagram illustrating a wavelength characteristic 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 in which the thickness of the SubNc film is 100 nm. (Dashed line) and the characteristic (dashed-dotted line) when a voltage of 10 V is applied from the power supply 160.

  As shown in FIG. 5, it has been found that the external quantum efficiency increases as the voltage of the power supply 160 increases. When the voltage of the power supply 160 was changed, the wavelength at which the peak value of the external quantum efficiency was slightly changed, but the shape of the characteristics was almost the same. The wavelengths giving the peak value of the external quantum efficiency are all about 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 the external quantum efficiency increases when the applied voltage is increased from 10 V to 20 V. Further, it was 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.

  In addition, when a photoelectric conversion unit 100R having a different thickness of the SubNc film used as the organic photoelectric conversion film 130R was manufactured and the output voltage of the power supply 160 was changed, a wavelength characteristic of the external quantum efficiency was obtained as shown in FIG. .

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

  FIG. 6 shows a characteristic (solid line) in which the thickness of the SubNc film (organic photoelectric conversion film 130R) is 100 nm and a voltage of 20 V is applied from the power supply 160 (solid line), and the thickness of the SubNc film (organic photoelectric conversion film 130R) is 50 nm. And the characteristic (dashed line) of applying a voltage of 10 V from the power supply 160 with the thickness of the SubNc film (organic photoelectric conversion film 130R) being 50 nm. .

  As shown in FIG. 6, it was found that the wavelength giving 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 the characteristic shown in FIG. 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 130R is used for the imaging device 50, the thickness of the organic photoelectric conversion film 130R is adjusted so that the peak value of the external quantum efficiency for red matches the spectral sensitivity characteristics of the imaging device 50 for red. Should be set.

  In the characteristics shown in FIG. 6, when comparing the SubNc film having a thickness of 50 nm and an applied voltage of 15 V (broken line) with the SubNc film having a thickness of 50 nm and an applied voltage of 10 V (dashed line), Both wavelength bands are from 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 increases at about 550 nm, and the wavelength band for red is expanded. From this result, it was found that the width of the wavelength band for red can be set by changing the thickness of the SubNc film.

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

  As described above, according to the first embodiment, a 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.

  Further, the photoelectric conversion unit 100B for blue and the photoelectric conversion unit 100G for green include the organic photoelectric conversion film 130B and the organic photoelectric conversion film 130G having the above-described compositions, respectively. It has been found that efficiency can be obtained.

Such a highly efficient photoelectric conversion unit 100B for blue is a coumarin 30 having a sensitivity to blue light or a mixed film of a coumarin derivative and an electron transporting organic material, and a photoelectric conversion unit 100G for green is converted to green light. A mixed film of quinacridone or a quinacridone derivative having high sensitivity 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, a material suitable for each of blue and green can be selected. It is desirable that the HOMO level and the LUMO level of the electron transporting organic material are lower than the HOMO level and the LUMO level of the organic molecules of the photoelectric conversion unit 100B or 100G, respectively. For example, fullerenes C ₆₀ , C ₇₀ , fullerene derivatives, 8-quinolinolato) aluminum (Alq3) and the like. Note that 100B may be combined with an electron / hole blocking layer to reduce dark current.

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

  In addition, since 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 dark current can be significantly reduced. 50 can be provided.

  In the above description, the mode in which light is incident on the photoelectric conversion units 100B, 100G, and 100R from the cathodes 150B, 150G, and 150R is described. However, light is incident on the photoelectric conversion units 100B, 100G, and 100R from the anodes 110B, 110G, and 110R. May be incident. In this case, the anode 110R may be formed of 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 has 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 the first embodiment is replaced with an 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 a glass substrate 30 in the order of a cathode 150R, an organic photoelectric conversion film 230R, and an anode 110R. Light enters from below, as indicated by the 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.

  The following conditions were used as the organic photoelectric conversion film 230R. 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 the description 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 manufactured by sequentially forming a ZnPc film and a SubNc film on the cathode 150R by a vacuum deposition method. The thickness of each of the ZnPc film and the SubNc film is 50 nm.

A voltage was applied from the power supply 160 between the anode 110R and the cathode 150R of the thus-produced photoelectric conversion unit 200R, irradiated with light, and the external quantum efficiency was measured. Note that, similarly to Embodiment 1, the irradiation light was monochromatic light having a wavelength range of 320 nm to 800 nm, and the output was kept constant at 50 μW / cm ² .

  FIG. 8 is a diagram illustrating a wavelength characteristic of the external quantum efficiency obtained by the photoelectric conversion unit 200R of FIG. The horizontal axis indicates the wavelength (nm), and the vertical axis indicates the 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 from 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 30%. For comparison, an organic photoelectric conversion film consisting only of 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%.

  Therefore, it was found that adding the SubNc film to the ZnPc film greatly improved the external quantum efficiency. Note that 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 different from each other. It seems to be due to not including.

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 was found that when the voltage of the power supply 160 was further increased, the dark current sharply increased. Therefore, it has been found that when the output voltage of the power supply 160 is set to, 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, in the wavelength characteristic of the external quantum efficiency shown in FIG. 8, it was found that a characteristic like a small hill occurred in a range of about 530 nm to about 600 nm as compared with the characteristic shown in FIG.

  In addition, such characteristics as a small hill having a range of about 530 nm to about 600 nm include the characteristic (dashed line) of applying 15 V to the SubNc film (50 nm) shown in FIG. This does not occur in the characteristics (dot-dash line) when 10 V is applied to (50 nm).

  As can be seen from the comparison between the characteristics (dashed line) of 15 V applied to the SubNc film (50 nm) shown in FIG. 6 of the first embodiment and the characteristics (dashed-dotted line) of 10 V applied to the SubNc film (50 nm). The peak of the external quantum efficiency of the 50 nm thick SubNc film is about 670 nm.

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

  On the other hand, it is known that ZnPc has a characteristic in which a peak value of the external quantum efficiency exists at about 600 nm.

  Therefore, the characteristic of the wavelength characteristic of the external quantum efficiency shown in FIG. 8 such as a small hill in the range of about 530 nm to about 600 nm is obtained by the ZnPc film (50 nm) of 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.

  In addition, it was found that the distribution of the wavelength characteristic of the external quantum efficiency can be adjusted by using the ZnPc film and the SubNc film having different wavelengths that provide the peak value of the external quantum efficiency. That is, when the external quantum efficiency is not improved only by the ZnPc film, the external quantum efficiency can be significantly improved by adding the SubNc film. When the distribution of the external quantum efficiency has a wavelength region that cannot be covered only by the SubNc film, the external quantum efficiency can be improved by adding the 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. The unit 200R can be realized.

  Further, by providing the photoelectric conversion unit 100R for red on the photoelectric conversion unit 100B for blue and the photoelectric conversion unit 100G for green, an image sensor with improved photoelectric conversion efficiency can be provided.

  Examples of the photoelectric conversion unit 200R for red include a phthalocyanine derivative, an anthraquinone derivative, a triphenylmethane derivative, and a pyrazolopyrimidine derivative.

  As described above, the imaging device according to the exemplary embodiment of the present invention has been described. However, the present invention is not limited to the specifically disclosed embodiment, without departing 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 part 230R Organic photoelectric conversion film

Claims (5)

A first electrode;
An organic photoelectric conversion film for a first red color, which is disposed on one surface side of the first electrode and contains 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 supply having a positive electrode connected to the first electrode and a negative electrode connected to the second electrode;
A signal reading unit that is connected to the first electrode and the second electrode and reads an electric charge generated by photoelectric conversion in the first red organic photoelectric conversion film as an image signal;
The first electrode or the second electrode is a transparent electrode, and light is incident on the first red organic photoelectric conversion film from the transparent electrode side,
An imaging device , wherein a wavelength at which a peak of the red spectral sensitivity of the first red organic photoelectric conversion film is given is determined by a film thickness of the first red organic photoelectric conversion film . A first electrode;
An organic photoelectric conversion film for a first red color, which is disposed on one surface side of the first electrode and contains 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 supply having a positive electrode connected to the first electrode and a negative electrode connected to the second electrode;
A signal reading unit that is connected to the first electrode and the second electrode and reads an electric charge generated by photoelectric conversion in the first red organic photoelectric conversion film as an image signal;
The first electrode or the second electrode is a transparent electrode, and light is incident on the first red organic photoelectric conversion film from the transparent electrode side,
An imaging device , wherein a wavelength band of a 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 . A hole injection block layer disposed between the first red organic photoelectric conversion film and the first electrode;
The image pickup 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. A second layer comprising zinc phthalocyanine, which is disposed 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; further comprising a red organic photoelectric conversion film, an image pickup device of any one of claims 1 to 3. The imaging device according to claim 4 , wherein a wavelength at which the second red organic photoelectric conversion film has a spectral sensitivity peak is different from a wavelength at which the first red organic photoelectric conversion film has a spectral sensitivity peak.

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