Organic semiconductor light receiving device

Abstract

This organic semiconductor light receiving device comprises: a transparent substrate (12); a first electrode (13) composed of a transparent conductive film formed on the transparent substrate (12); an active layer (15) formed on the first electrode (13) and having a bulk heterojunction structure in which a donor material and an acceptor material are mixed; an electron blocking layer (16) formed on the active layer (15); and a second electrode (17) composed of a metal and formed on the electron blocking layer (16). The mixing ratio of the donor material to the acceptor material is within the range of 0.125-1.0.

Description

Organic semiconductor photodetector

[0001] The present invention relates to an organic semiconductor light-receiving device, and more particularly to an organic semiconductor light-receiving device having an active layer with a bulk heterojunction structure.

[0002] Research and development is underway on photoelectric conversion elements that have sensitivity in the near-infrared region and have an organic semiconductor layer formed on a flexible, inexpensive plastic substrate.

[0003] For example, Patent Document 1 discloses an optical sensor in which an organic electroluminescent element having an inverted structure with a cathode on a substrate and an organic light-receiving element having an inverted structure with a cathode on a substrate are formed on the same substrate.

[0004] In addition, for photoelectric conversion elements using organic semiconductors, adopting a bulk heterojunction structure in which donor and acceptor materials are mixed is considered promising for improving performance. However, conventional organic semiconductor materials have issues such as insufficient light-receiving sensitivity and large dark current. Furthermore, conventional bulk heterojunction structures have difficulty controlling each material, leading to problems with reproducibility.

[0005] Japanese Patent Application Laid-Open No. 2020-27875

[0006] The present invention has been made in view of the above-mentioned problems, and aims to provide an organic semiconductor light-receiving device that has high light-receiving sensitivity, suppressed dark current, and excellent light-receiving characteristics.

[0007] The organic semiconductor light-receiving device of the present invention comprises: a transparent substrate; a first electrode made of a transparent conductive film formed on the transparent substrate; an active layer formed on the first electrode and having a bulk heterojunction structure in which a donor material and an acceptor material are mixed; an electron-blocking layer formed on the active layer; and a second electrode formed on the electron-blocking layer and made of a metal, wherein the mixing ratio of the donor material to the acceptor material is within a range of 0.125 to 1.0.

[0008] FIG. 1 is a cross-sectional view schematically showing a cross section of an organic photodiode according to a first embodiment; FIG. 2 is a cross-sectional view schematically showing a cross section of an organic photodiode according to a comparative example 1 (CX1); FIG. 3 is a diagram showing measurement results of a current density J versus an applied voltage V of an organic photodiode having an inverted structure according to the first embodiment; FIG. 4 is a diagram showing measurement results of a current density J versus an applied voltage V of an organic photodiode having a forward structure according to a comparative example 1; FIG. 5 is a cross-sectional view schematically showing a cross section of an organic photodiode according to a second embodiment; FIG. 6 is a diagram showing measurement results of a current density J versus an applied voltage V of an organic photodiode according to the second embodiment (EX2) and an organic photodiode according to a comparative example 2 (CX2); ２ Pc: PC ６１ 1 is a diagram showing measurement results of light-receiving characteristics of organic photodiodes fabricated by changing the mixing ratio of ZnO (ZnS) and BM (Br). 2 is an image of a cross section of an active layer observed with a scanning transmission electron microscope (STEM). 3 is a schematic cross-sectional view of an organic photodiode according to a first modified example of the second embodiment.

[0009] Preferred embodiments of the present invention will be described below, but they may be modified and combined as appropriate. Furthermore, in the following description and accompanying drawings, substantially identical or equivalent components will be described using the same reference numerals. [First Embodiment] FIG. 1 is a cross-sectional view schematically illustrating an organic photodiode 10, which is an organic semiconductor light-receiving device according to a first embodiment. (1) Structure of Organic Photodiode The organic photodiode 10 (EX1) is an inverted-structure organic photodiode having an active layer disposed between a pair of electrodes and having an absorption band in the near-infrared region. At least one of the pair of electrodes has a transparent electrode as a cathode.

[0010] Specifically, the organic photodiode 10 is formed by laminating a base substrate 11, a transparent substrate 12, a first electrode 13, an electron injection layer 14, an active layer 15, an electron blocking layer 16, and a second electrode 17 in this order.

[0011] The base substrate 11 is a transparent substrate made of an inflexible material such as glass. The transparent substrate 12 provided on the base substrate 11 is a substrate made of a transparent material such as a resin film or glass. The transparent substrate 12 is preferably a flexible film substrate in order to take advantage of the characteristics of an organic photodiode (hereinafter also referred to as OPD) that uses an organic film. Light to be detected is taken in from the transparent substrate 12 side.

[0012] When the transparent substrate 12 is made of a film, the transparent substrate 12 may be attached to the base substrate 11 to form an element (photodiode), and the base substrate 11 may be peeled off and removed after the element is completed. In this case, the base substrate 11 does not need to be transparent.

[0013] In this specification, "transparent" means that the element has the property of transmitting light to the light receiving object. For example, the transparent element component may be colored, printed, or otherwise provided with an optical filter.

[0014] A first electrode 13 made of a transparent conductive film is patterned on the transparent substrate 12. A desired transparent electrode pattern can be obtained by mask deposition or by patterning using a photolithography process after deposition on the entire surface. In this embodiment, mask sputtering was performed using a SUS (stainless steel) mask.

[0015] In this embodiment, the first electrode 13 made of a transparent conductive film corresponds to the cathode, and the second electrode 17 corresponds to the anode. In this embodiment, indium tin oxide (ITO) is used as the first electrode 13, but this is not limiting. For example, other conductive metal oxides or conductive polymers such as polyethylenedioxythiophene (PEDOT) can also be used. Alternatively, a metal mesh film and these transparent conductive films can be combined.

[0016] An electron injection layer 14 is formed on the first electrode 13. The electron injection layer 14 functions as a carrier injection layer in the inverted organic device. Polyethyleneimine ethoxylate (PEIE) is used for the electron injection layer 14. By providing the electron injection layer 14, the work function on the ITO side can be controlled. For example, it can be controlled to approximately -4.7 V to -3.7 V. This improves OPD performance, such as increasing photocurrent and suppressing dark current. The PEIE film thickness is preferably 5-10 nm. While providing the electron injection layer 14 is preferable, it is not necessary. An active layer 15 is formed on the electron injection layer 14. The active layer 15 has a microphase-separated structure (bulk heterojunction structure) formed by mixing a donor material and an acceptor material.

[0017] Specifically, the active layer 15 contains an alkoxyphthalocyanine derivative (8OH), which is a low molecular weight material, as a donor material. ２ Pc: 1,4,8,11,15,18,22,25-octaalkoxy-phthalocyanine) was used. ２ Pc has a discotic shape, and the molecules are easily aligned with each other, so that it is easy to adopt a fine crystalline state.

[0018] In addition, a fullerene derivative (PC), a low molecular weight material, was used as the acceptor material. ６１ BM: Phenyl-C61-butylic acid methyl ester) was used.

[0019] The active layer 15 can be formed by dissolving these donor and acceptor materials in an organic solvent at a predetermined ratio and printing or coating the solution. In this embodiment, the active layer 15 is formed by mixing the donor and acceptor materials at a ratio of 8OH / 2. ２ Pc: PC ６１ The weight ratio of BM was 1:4.

[0020] The active layer 15 can be formed at room temperature under atmospheric pressure, and many coating methods can be applied, such as flexographic printing, inkjet printing, spray coating (including electrostatic spray deposition), bar coating, slit coating, and spin coating.

[0021] In this embodiment, chloroform was used as the solvent for dispersing the donor material and acceptor material (D / A material). The solvent is not limited to chloroform; toluene or other solvents can be used as long as they dissolve the D / A material. Here, the D / A material was mixed at a predetermined ratio and dissolved at 2 wt % in the solvent. This solution of the D / A material was filtered and then spin-coated.

[0022] The thickness of the active layer 15 is preferably in the range of 100 to 600 nm, and more preferably in the range of 200 to 400 nm in order to obtain a high photocurrent.

[0023] An electron blocking layer 16 is formed on the active layer 15. The electron blocking layer 16 is made of molybdenum oxide (MoO ｘ Specifically, it is made of molybdenum trioxide (MoO ３ A thin film of molybdenum trioxide (MoO) was formed to a thickness of about 5 nm to serve as the electron blocking layer 16. The electron blocking layer 16 can suppress the dark current of the OPD. ３ The thickness of the film is preferably in the range of 5-40 nm.

[0024] Finally, a second electrode 17 made of metal was formed on the electron blocking layer 16. In this embodiment, gold (Au) was used as the second electrode 17, and the film was formed by vacuum deposition using a SUS mask.

[0025] The second electrode 17 is formed as an ultra-thin film of Au that can be considered transparent. In this case, the thickness of the Au film is preferably within the range of 10-40 nm. This makes it possible to detect light incident on the second electrode 17, and light from both the top and bottom of the organic photodiode 10. The electrode material is not limited to Au. Furthermore, if light incident from the second electrode 17 side is not detected, the second electrode 17 does not need to be an ultra-thin film.

[0026] As described above, the organic photodiode 10 having an inverted structure according to the first embodiment can be briefly described as follows: ２ PC ６１BM (bulk heterostructure) / MoO ３ The structure is electron blocking layer / Au.

[0027] (2) Structure of Organic Photodiode (CX1) of Comparative Example 1 Fig. 2 is a cross-sectional view schematically showing the cross section of the organic photodiode 100 of Comparative Example 1 (CX1). The organic photodiode 100 of Comparative Example 1 is a photodiode with a forward structure.

[0028] The organic photodiode 100 of Comparative Example 1 is the same as the organic photodiode 10 of the first embodiment in that it has a base substrate 11 made of glass, a transparent substrate 12 made of a resin film provided on the base substrate 11, and a first electrode 13 made of ITO provided on the transparent substrate 12. In Comparative Example 1, the first electrode 13 corresponds to the anode, and the second electrode 107 corresponds to the cathode.

[0029] A hole injection layer 104 (electron blocking layer) serving as a carrier injection layer in the forward structure is formed on the first electrode 13. Polyethylenedioxythiophene (PEDOT) was formed as the hole injection layer 104.

[0030] The same active layer 15 as in the first embodiment was formed in the hole injection layer 104. That is, the active layer 15 had a bulk heterojunction structure.

[0031] A second electrode 107 made of aluminum (Al) was formed on the active layer 15. The second electrode 107 was formed by vacuum deposition using a SUS mask.

[0032] That is, the organic photodiode 100 of Comparative Example 1 (CX1) has a structure of {ITO / PEDOT hole injection layer / 8OH ２ PC ６１ The structure is a bulk heterostructure (BM / Al).

[0033] (3) Evaluation of Light-Receiving Characteristics FIGS. 3 and 4 show the current density J (A / cm) versus the applied voltage V (V) of the organic photodiode 10 (EX1) with the inverted structure of the first embodiment and the organic photodiode 100 with the forward structure of Comparative Example 1 (CX1), respectively. ２ ) is a diagram showing the measurement results.

[0034] The light from a xenon lamp was separated using a bandpass filter, and light with a wavelength of 760 nm was made to enter the organic photodiode 10 and the organic photodiode 100 from the transparent substrate 12 side to measure the light receiving characteristics (JV characteristics).

[0035] In addition, the donor material and the acceptor material (8OH ２ Pc: PC ６１ 1 shows the measurement results for the organic photodiode 10 and the organic photodiode 100 in which the active layer 15 uses a mixture ratio (D / A mixture ratio) of 1:4 by weight of BM.

[0036] When compared at an applied voltage (reverse bias) of −1 V, the photocurrent density (Jp) of the organic photodiode 10 (EX1) of the first embodiment is 1.6×10 －４ A / cm ２ The photocurrent density (Jp) of the organic photodiode 100 of Comparative Example 1 (CX1) is 1.0×10 －４ A / cm ２ That is, it is found that the organic photodiode 10 of the first embodiment provides a photocurrent that is 1.6 times larger than that of the organic photodiode 100 of the first comparative example.

[0037] It is also found that the dark current density (Jd) is reduced in the organic photodiode 10 (EX1) of the first embodiment compared to the organic photodiode 100 (CX1) of Comparative Example 1 in the applied voltage range of 0 to −1 V. Therefore, it was found that an organic photodiode having improved light receiving sensitivity, significantly reduced dark current, and a high S / N ratio can be obtained.

[0038] Second Embodiment (1) Structure of Organic Photodiode FIG. 5 is a cross-sectional view that schematically shows a cross section of an organic photodiode 30 that is an organic semiconductor light-receiving device according to a second embodiment.

[0039] The inverted-structure organic photodiode 30 (EX2) of this embodiment differs from the organic photodiode 10 of the first embodiment in that an electron injection barrier layer 31 is provided between the active layer 15 and the electron blocking layer 16, but other configurations are the same as those of the organic photodiode 10.

[0040] More specifically, the active layer 15 and molybdenum oxide (MoO ｘ ) / Au electrode (electron blocking layer 16 / second electrode 17), a hydrogenated phthalocyanine (H ２ Pc), where hydrogenated phthalocyanine (H ２ Pc) was formed by vacuum deposition.

[0041] The electron injection barrier layer 31 is an acceptor material of the active layer 15 and has a shallow PC (lowest unoccupied molecular orbital) level. ６１ BM is MoO ｘ / Direct contact with the Au electrode is avoided to suppress electron injection, which results in a reduction in dark current while maintaining almost no change in photocurrent.

[0042] The electron injection barrier layer 31 is made of hydrogenated phthalocyanine (H ２ The electron injection barrier layer 31 is not limited to Pc. An inorganic or organic semiconductor layer having a higher electron injection barrier than the electron blocking layer 16 can be used as the electron injection barrier layer 31. For example, when the electron blocking layer 16 is an organic semiconductor, a material having a LUMO level (eV) higher than the LUMO level of the electron blocking layer 16 can be used.

[0043] The electron injection barrier layer 31 can be made of, for example, a material generally known as a hole injection material, such as a phthalocyanine derivative, starburst amines such as m-MTDATA (4,4′,4″-tris[phenyl(m-tolyl)amino]triphenylamine), or a polymer-based material such as polythiophenes such as PEDOT (poly(3,4-ethylenedioxythiophene)), or polyvinylcarbazole derivatives.

[0044] (2) Evaluation of Light-Receiving Characteristics FIG. 6 shows the relationship between the applied voltage V (V) and the current density J (A / cm) of the organic photodiode 30 (EX2) of the second embodiment and the organic photodiode of Comparative Example 2 (CX2) with a forward structure. ２ ) is a diagram showing the measurement results.

[0045] The organic photodiode of Comparative Example 2 (CX2) is a sample in which the electron injection barrier layer 31 is formed between the active layer 15 and the second electrode 107 of the organic photodiode 100 of Comparative Example 1 (CX1) under the same conditions as the organic photodiode 30 (EX2). ２ Pc: PC ６１ 1 shows the measurement results for the organic photodiode 30 and the organic photodiode 100, in which the active layer 15 has a B:M ratio of 1:4.

[0046] The photocurrent density (Jp) of the organic photodiode 30 (EX2) is equivalent to that of the organic photodiode 10 (EX1) of the first embodiment, and it is clear that high light-receiving sensitivity can be obtained.

[0047] Furthermore, the dark current is significantly reduced compared to the organic photodiode 10 (EX1) of the first embodiment, and is 1×10 at a reverse bias voltage of −1 V. －９ A / cm ２ It is clear that it is suppressed to some extent.

[0048] In organic photodiodes with a light-receiving band in the near-infrared region, the gap between the HOMO-LUMO (HOMO: Highest Occupied Molecular Orbital) levels of the active layer is narrow, making it difficult to block carrier injection from the electrodes, and leading to the problem of large dark currents.

[0049] It has been found that this embodiment significantly suppresses electron injection on the second electrode 17 side, and provides an organic photodiode with an extremely high S / N ratio.

[0050] [D / A Mixing Ratio of Active Layer] FIG. 7 shows the D / A mixing ratio of the donor material and the acceptor material (8OH ２ Pc: PC ６１ The graph plots the measurement results of the light-receiving characteristics of the organic photodiode 100 of Comparative Example 1 (CX1), which was fabricated by changing the mixing ratio (D / A mixing ratio) of the donor material and the acceptor material in the active layer. That is, the photocurrent and the light-receiving sensitivity were evaluated by focusing on the mixing ratio of the donor material and the acceptor material in the active layer.

[0051] The relationship between the D / A mixing ratio of the active layer and the photocurrent (or photosensitivity) was confirmed for the organic photodiode 30 of the second embodiment (EX2) and the organic photodiode 100 of the comparative example (CX1). As a result, it was confirmed that in the case of the second embodiment (EX2) with an inverted structure and the comparative example (CX1) with a forward structure, a high photocurrent (or photosensitivity) can be obtained in a range of D / A mixing ratios that are considered to be the same within the range of lot-to-lot variations and measurement errors. Therefore, the results of the comparative example (CX1), for which evaluation was performed on a large number of lots, will be used below for explanation.

[0052] The horizontal axis is 8OH ２ Pc: PC ６１ The left vertical axis represents the photocurrent density J (A / cm ２ ), and the right vertical axis represents the light receiving sensitivity R (A / W) calculated from the photocurrent.

[0053] As shown in the figure, the photocurrent and light sensitivity are significantly dependent on the D / A mixing ratio. When the D / A mixing ratio (mixing ratio of donor material to acceptor material) is in the range of 0.125 to 1.0, the light sensitivity is high. It is more preferable that the D / A mixing ratio is in the range of 0.20 to 0.50. In particular, it was found that significantly high light sensitivity can be obtained when the D / A mixing ratio is in the range of 0.25 to 0.35.

[0054] The photosensitivity R exceeds 0.3 A / W when the D / A mixing ratio is near 0.30 (1:3.5). This is converted to an external quantum efficiency (EQE) of approximately 50%, demonstrating that near-infrared light is absorbed with extremely high efficiency and converted into a photocurrent for output.

[0055] 8 is an image of a cross section of the active layer 15 observed by a scanning transmission electron microscope (STEM). ２ Pc: PC ６１ 10 is an observation image of an active layer 15 having a D / A mixture ratio of 1:4.

[0056] The right side of the figure shows an enlarged image of a part of the active layer 15. The whitish part is the 8OH ２Pc domain, the gray area is PC ６１ This is the BM region (domain).

[0057] In the case of an organic photodiode with an inverted structure, when a reverse bias voltage is applied to function as a photodiode, the carriers generated by light are transferred to the acceptor PC on the first electrode 13 side (ITO in this case), which is the lower electrode. ６１ Electrons are injected from the BM region into the first electrode, and the donor 8OH is released on the second electrode 17 side (here, the metal electrode (Au)) which is the upper electrode. ２ Holes are preferably injected from the Pc region into the second electrode, thereby allowing photocurrent to be observed.

[0058] On the second electrode 17 side, the donor material (8OH ２ It can be seen that the density of the acceptor material (PC) is high and decreases toward the first electrode 13. ６１ It can be seen that the density of the BM is low on the second electrode 17 side and increases toward the first electrode 13.

[0059] The distribution of such domains is 8OH ２ This is a feature of the use of Pc, and it can be seen that this allows the formation of a bulk heterostructure that is particularly suitable for the inverted organic photodiode. Such a distribution is due to the fact that the micro-phase separation that results in the bulk heterostructure is due to the small molecules and the 8OH ２ Pc is crystalline, while PC ６１ This was thought to be due to the difference that the BM is an amorphous material.

[0060] In the second embodiment, a shallow acceptor material (PC ６１ BM) is MoO ｘ The electron injection barrier layer 31 is provided to prevent direct contact with the / Au electrode (second electrode 17), but the acceptor material (PC ６１ It is believed that the low density of BM on the second electrode 17 side more effectively suppresses electron injection, which is effective in reducing dark current.

[0061] In addition, light in the near infrared region is ２The light is absorbed by the Pc domain, but the 8OH ２ The Pc domain has a width of 5-10 nm. In organic photodiodes, this domain width is important, and if the domain width exceeds 20 nm, excitons generated by light absorption will be deactivated before becoming carriers. In other words, the low molecular weight 8OH ２ In the Pc-based system, a bulk heterostructure with an ideal width can be formed.

[0062] In addition, 8OH ２ Pc: PC ６１ When the BM mixture ratio changes, the domain width of the donor material changes, and therefore, as shown in FIG. 7, it is considered that the light receiving sensitivity changes depending on the D / A mixture ratio.

[0063] 9 is a cross-sectional view schematically showing a cross section of an organic photodiode 40 (EX3) that is a first modification of the organic photodiode 30 of the second embodiment. In the organic photodiode 40 of the first modification, the active layer 15 is composed of a first active layer 15A formed on the electron injection layer 14 and a second active layer 15B formed on the first active layer 15A. The other configuration is the same as that of the organic photodiode 30 of the second embodiment.

[0064] More specifically, the D / A mixing ratio of the second active layer 15B is larger than that of the first active layer 15A. In other words, the donor material (8OH ２ The mixing ratio of the donor material (8OH Pc) in the first active layer 15A is ２ Pc). As mentioned above, it is preferable that the D / A mixture ratio of the entire active layer 15, i.e., the entire first active layer 15A and the second active layer 15B, is within the range of 0.125 to 1.0. With this configuration, electron injection on the second electrode 17 side is further suppressed, thereby reducing dark current and obtaining an organic photodiode with a high S / N ratio. Although the case of two active layers has been described here, three or more layers may also be used.

[0065] As described above in detail, according to the present invention, it is possible to provide an organic semiconductor light-receiving device that has high light-receiving sensitivity, suppresses dark current, and has excellent light-receiving characteristics.

[0066] The present invention is not limited to the above-described embodiments, and modifications can be made without departing from the scope of the present disclosure. For example, in the above-described embodiments and modifications, an organic photodiode (OPD) is used as an example of an organic semiconductor light-receiving device, but the organic semiconductor light-receiving device to which the present disclosure can be applied is not limited to this. The present disclosure can be applied to various photoelectric conversion devices that convert received light into electricity.

[0067] For example, the present invention can be applied to organic solar cells (OPVs). As described above, when an ultra-thin film that can be considered transparent is used as the second electrode, power generation can be achieved by using light from both sides of the organic semiconductor light-receiving device, improving the power generation efficiency.

[0068] 10, 30, 40: Organic photodiode 11: Base substrate 12: Transparent substrate 13: First electrode 14: Electron injection layer 15: Active layer 15A: First active layer 15B: Second active layer 16: Electron blocking layer 17: Second electrode 31: Electron injection barrier layer 100: Organic photodiode (Comparative example)

Claims

1. An organic semiconductor light-receiving device comprising: a transparent substrate; a first electrode made of a transparent conductive film formed on the transparent substrate; an active layer formed on the first electrode and having a bulk heterojunction structure in which a donor material and an acceptor material are mixed; an electron-blocking layer formed on the active layer; and a second electrode formed on the electron-blocking layer and made of a metal, wherein the mixing ratio of the donor material to the acceptor material is within the range of 0.125 to 1.

0.

2. The organic semiconductor light-receiving device according to claim 1, wherein the density of the donor material in the active layer is higher on the second electrode side and decreases toward the first electrode.

3. The organic semiconductor light-receiving device according to claim 1, wherein the donor material is a crystalline small molecule organic semiconductor material, and the acceptor material is a small molecule organic semiconductor material having an amorphous structure.

4. The organic semiconductor light-receiving device according to claim 3, wherein the donor material is an alkoxyphthalocyanine derivative having an absorption band in the near-infrared region, and the acceptor material is a fullerene derivative.

5. The donor material is 8OH ２ 4. The organic semiconductor light-receiving device according to claim 3, wherein the organic semiconductor light-receiving device is Pc.

6. The donor material is 8OH ２ Pc, and the acceptor material is PC ６１ 4. The organic semiconductor light-receiving device according to claim 3, wherein the organic semiconductor light-receiving device is a BM.

7. The organic semiconductor light-receiving device according to claim 1, wherein the mixture ratio of said donor material to said acceptor material is in the range of 0.20 to 0.

50.

8. The organic semiconductor light-receiving device according to claim 1, wherein the mixture ratio of said donor material to said acceptor material is in the range of 0.25 to 0.

35.

9. The organic semiconductor light-receiving device according to claim 1, further comprising an electron injection layer formed between said first electrode and said active layer.

10. The organic semiconductor light-receiving device according to claim 1, further comprising an electron injection barrier layer, which is a semiconductor layer having a higher electron injection barrier than the electron blocking layer, and is provided between the active layer and the electron blocking layer.

11. The second electrode is made of gold (Au), and the electron blocking layer is made of molybdenum oxide (MoO ｘ ) and the electron injection barrier layer is made of H ２ 11. The organic semiconductor light-receiving device according to claim 10, which is made of Pc.

12. The organic semiconductor light-receiving device according to claim 1, wherein the second electrode is made of gold (Au) and has a film thickness within the range of 10 to 40 nm.

13. The organic semiconductor light-receiving device according to claim 1, wherein the active layer comprises a first active layer formed on the electron injection layer and a second active layer formed on the first active layer, the mixing ratio of the donor material to the acceptor material in the second active layer is higher than the mixing ratio of the donor material to the acceptor material in the first active layer, and the mixing ratio in the entire first active layer and the second active layer is within a range of 0.125 to 1.0.

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