JP2009302252A - Organic thin film light receiving element, organic thin film light receiving/emitting element, organic thin film light receiving/emitting element array, pulse sensor using thereof and vehicle equipped with pulse sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic thin film light receiving element capable of controlling a dark current by forming an ion doped surface. <P>SOLUTION: The thin film light receiving element has, on a base material 1, a first electrode 2 and a second electrode 4, at least one of which possesses an optical transparency, and a photoconductive organic thin film layer 3 for generating a photo carrier by absorbing the incident light interposed between the first electrode 2 and the second electrode 4. At least one of the first electrode 2 and the photoconductive organic thin film layer 3 includes the ion doped surface 5, in which ions are doped, on the boundary between the first electrode 2 and the photoconductive organic thin film layer 3. The size of the energy of the work function of the first electrode 2 is smaller than the energy of the ionization potential of the photoconductive organic thin film layer 3, and to generate a photoinduced current, a larger positive voltage is applied to the first electrode 2 than that applied to the second electrode 4 which is capable of transporting the photo carrier. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an organic thin film light receiving element, an organic thin film light emitting / receiving element provided with the organic thin film light receiving element and the organic thin film light emitting element, an organic thin film light receiving / emitting element array including a plurality of the organic thin film light receiving / emitting elements, and the organic thin film light receiving element. The present invention relates to a pulse sensor using a light emitting element or an organic thin film light emitting / receiving element array, and a vehicle provided with the pulse sensor.

  As a light receiving element for taking in external light, there are optical sensors such as a photoelectric element and a photovoltaic element. The light receiving element is used, for example, in a pulse meter. The pulse meter is equipped with a light emitting element and a light receiving element. The light from the light emitting element is applied to the human body, particularly the arterial part and the vein part, and the reflected light scattered by hemoglobin in the blood is received by the light receiving element. In addition to the pulse, the amount of change in hemoglobin is measured.

In recent years, light receiving elements using organic semiconductors have been developed. In Patent Document 1, a photo-induced current is obtained by dispersing a photoconductive organic semiconductor such as perylene or pentacene in an insulating resin such as polycarbonate or polyvinyl carbazole and irradiating the resin-dispersed organic semiconductor layer with light. A light receiving element is disclosed.
JP 2002-76430 A

  However, in Patent Document 1, since the photoconductive organic semiconductor is dispersed in the insulator, it is necessary to increase the applied voltage in order to obtain a high S / N ratio.

  Accordingly, an object of the present invention is to provide an organic thin film light-receiving element that can obtain a high S / N ratio with low power.

  An organic thin film light receiving element according to the present invention for solving the above-described problems is characterized by the following configuration. A light carrier is generated by absorbing incident light that is interposed between the first electrode and the second electrode, and the first electrode and the second electrode, at least one of which is light transmissive on the substrate. A photoconductive organic thin film layer. At least one of the first electrode and the photoconductive inducing thin film layer has an ion-doped surface doped with ions at the interface between the first electrode and the photoconductive organic thin film layer, and the work function of the first electrode Is smaller than the ionization potential energy of the photoconductive organic thin film layer, and a positive voltage is applied to the first electrode higher than the second electrode.

  According to the present invention, since at least one of the mating surfaces of the first electrode and the photoconductivity-inducing thin film layer is provided with an ion-doped surface doped with ions, a potential barrier is formed at the interface between the two layers. The current can be suppressed, and the ratio (S / N ratio) to the photoinduced current can be increased.

  First, a preferred embodiment of the organic thin film light receiving element of the present invention will be described. However, the organic thin film light receiving element of the present invention is not limited to the following embodiments. In the accompanying drawings, each component is exaggerated for clarity of explanation. In the drawings, the same elements are denoted by the same reference numerals, and the description of the same elements is omitted in the specification.

  In the following description, a case where the organic thin film light receiving element of the present invention is used as a pulse sensor together with the organic thin film light emitting element will be described as a representative embodiment. However, the technical scope of the present invention is not limited to the following forms, and includes other forms. That is, in addition to use as a pulse detection device, it can be used as various detection devices.

[First embodiment]
FIG. 1 is a conceptual diagram for explaining an organic thin film light emitting / receiving element 30 having the organic thin film light receiving element 10 according to the first embodiment of the present invention.

  The organic thin film light receiving element 10 according to the present embodiment is formed on a single substrate 1 together with the organic thin film light emitting element 20 to form an organic thin film light receiving and emitting element 30. The organic thin film light emitting / receiving element 30 is arranged with the surface including the organic thin film light receiving element 10 and the organic thin film light emitting element 20 facing the subject 40, and irradiates the subject 40 with light 8 from the organic thin film light emitting body 20. Then, the light 8 reflected by the subject 40 is received by the organic thin film photoreceptor 10, and detection of biological information such as a pulse in the subject 40 from information (for example, light intensity) of the light 8, or of the subject 40. Used to detect physical properties. Here, instead of the organic thin film light emitting element 20 provided in the organic thin film light emitting / receiving element 30, it is also possible to receive and detect light by the organic thin film light receiving element 10 using external light.

  Hereinafter, each member will be described in detail.

[Substrate 1]
A rigid member or a flexible member can be used as the substrate 1, but since the organic semiconductor material is used for the photoconductive organic thin film layer and has a flexible effect, the substrate 1 is a flexible member. Is preferred. Examples of the flexible member include an epoxy resin, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polystyrene (PS), polycarbonate (PC), and polyimide (PI). By applying various resin substrates and fibrous structures made of a flexible member to the base material 1 of the organic thin film light emitting / receiving element 30, the flexibility of the organic thin film light receiving body 10 and the organic thin film light emitting body 20 as will be described later. In combination, the element itself can be made very flexible. Therefore, the organic thin film light emitting / receiving element 30 can be used in an arbitrary shape, particularly in a curved shape.

[Organic thin film light receiving element 10]
FIG. 2 is a schematic sectional view for explaining the organic thin film light receiving element 10 according to the present embodiment.

  As shown in FIG. 2A, an organic thin film light receiving element 10 includes a first electrode 2 formed on a substrate 1, a photoconductive organic thin film layer 3 formed on the first electrode 2, a light A second electrode 4 formed on the conductive organic thin film layer 3 is provided. The first electrode 2 has an ion-doped surface 5 on which ions are doped at the interface with the photoconductive organic thin film layer 3. In this configuration, the light 8 is incident from the surface of the second electrode 4 with the voltage 6 applied between the first electrode 2 and the second electrode 4. The applied voltage is a positive voltage applied to the first electrode 2, and the photoinduced current is measured with the microammeter 7 in this state.

  As shown in FIG. 2 (b), the induced thin film light receiving element 10 is not limited to the order shown in FIG. 2 (a), for example, the second electrode 4 and the second electrode formed on the substrate 1. The photoconductive organic thin film layer 3 formed on the electrode 4 and the first electrode 2 formed on the photoconductive organic thin film layer 3 may be used. Further, the ion-doped surface 5 may be formed at the interface between the first electrode 2 and the photoconductive organic thin film layer 3, and either the first electrode 2 or the photoconductive organic thin film layer 3 is present. do it. In FIG. 2 (b), the photoconductive organic thin film layer 3 has an ion doped surface 5.

[First electrode 2 and second electrode 4]
The first electrode 2 and the second electrode 4 have a process in which light is incident on the photoconductive organic thin film layer 3 between both electrodes and the photocarriers generated in the photoconductive organic thin film layer 3 are transported. For this reason, at least one of the electrodes needs to be made of a light transmissive material. Here, the light transmittance in the present application is the same as the wavelength range in which the photoconductive organic thin film 3 has the best light receiving sensitivity from the viewpoint of absorbing a specific wavelength in the photoconductive organic thin film 3 and generating and transporting photocarriers. It is preferable to have light transmittance in the wavelength range, and it is not always necessary to have high light transmittance in the entire visible light region, or the entire region of ultraviolet rays or near infrared rays.

Examples of the material of the first electrode 2 and the second electrode 4 include SnO ₂ (tin oxide), ZnO (zinc oxide), FTO (F) in addition to ITO (indium tin oxide) which is an inorganic transparent electrode material. An inorganic oxide such as doped tin oxide) may be applied. Or, various conductive polymers such as π-conjugated polymer, such as polyethylenedioxythiophene (PEDOT) / polystyrene sulfonic acid (PSS), polyaniline (PANI), polypyrrole (PPy), polythiophene, carbon nanotube dispersion, etc. Is also possible. Thereby, since it has solubility, a printing technique such as ink jet is applied, and an advantage that an element can be directly formed on the substrate 1 is born.

  For example, when polycopper phthalocyanine (PCuPc) is selected for the photoconductive organic thin film layer 3, the absorption peak wavelength is in the range of 380 nm to 500 nm. Any one of the electrodes on the incident light side only needs to have high light transmittance (for example, light transmittance of 60% or more) in the same wavelength range as that of polycopper phthalocyanine (PCuPc).

[Photoconductive organic thin film layer 3]
The photoconductive organic thin film layer 3 is made of an organic semiconductor material and absorbs incident light by utilizing the properties of the semiconductor. When the energy of the light is equal to or greater than the energy band gap Eg, photocarriers (electrons, holes) ) Is generated. For example, the band gap of silicon is about 1.2 eV, and the energy of light depends on the wavelength. However, if the energy is 1.2 eV or more, photocarriers (electrons and holes) are generated. Since the wavelength sensitivity of light to be absorbed varies depending on the material constituting the photoconductive organic thin film layer 3, it is preferable to select an optimal material having a wavelength range of light to be received. The generated photocarriers (electrons, holes) move to the first electrode 2 (+) to which a positive voltage is applied, and the holes move to the second electrode 4 (−). A photo-induced current will flow. Here, since the photoconductive organic thin film layer 3 generates electrons according to the amount (number) of light, the current of the photoinduced current varies depending on the amount of light.

  In the present embodiment, the material of the photoconductive organic thin film layer 3 desirably includes, for example, a π-conjugated polymer. This facilitates the transport of the generated optical carrier (improves mobility) and has the advantage of being capable of forming an element directly on the substrate 1 by applying a printing technique such as inkjet because it is soluble. Is born.

  As such a π-conjugated polymer system, a hole transporting material in which majority carriers are holes is preferable. Examples of the hole transporting material include phthalocyanine derivatives, porphyrin derivatives, merocyanine derivatives, quinacridone derivatives, triphenyl diamine derivatives and mixtures thereof, or polyethylenedioxythiophene (PEDOT) / polystyrene sulfonic acid (PSS), polythiophene, Examples thereof include conductive polymers such as polyaniline (PANI), polypyrrole (PPy), and polyselenophene. Among these, phthalocyanine derivatives, porphyrin derivatives, merocyanine derivatives, quinacridone derivatives, triphenyl diamine derivatives and the like have strong absorption sensitivity in the visible light region and are preferable from the viewpoint of generation of photocarriers.

[Ion-doped surface 5]
As shown in FIG. 2, the ion-doped surface 5 is located at the interface between the first electrode 2 and the photoconductive organic thin film layer 3, and the surface of the first electrode 2 or the surface of the photoconductive organic thin film layer 3. Formed. The ion doped surface 5 greatly contributes to the positive formation of a potential barrier at the interface between the first electrode 2 and the photoconductive organic thin film layer 3.

  3 and 4 are schematic energy band diagrams for explaining the ion doped surface 5 provided in the organic thin film light receiving element 10 according to the present embodiment. As shown in FIGS. 3 and 4, the energy band structure changes depending on the presence or absence of the ion-doped surface 5 located at the interface between the first electrode 2 and the photoconductive organic thin film layer 3. The present invention is located at the interface of the first electrode 2 or the photoconductive organic thin film surface 3 when the ionization potential of the photoconductive organic thin film layer 3 is Ip and the work function of the first electrode 2 is Φm. The surface is positively provided with an ion-doped surface 5 that satisfies the relationship that the magnitude of energy is Φm <Ip, thereby forming a potential barrier of an arbitrary size and suppressing dark current. The dark current is generated as a current component even though no light is incident on the light receiving element.

  Hereinafter, the energy band structure and the height of the potential barrier depending on the magnitude of each energy will be described in detail with reference to the drawings. FIG. 3 shows an energy band structure when the magnitude of energy is Ip <Φm. FIG. 4 shows an energy band structure when the magnitude of energy, which is a feature of the present invention, is Ip> Φm.

[If Ip <Φm]
First, the energy band structure when the energy magnitude is Ip <Φm will be described with reference to FIG. 3A is a diagram showing an energy band structure before the first electrode 2 and the photoconductive organic thin film layer 3 are in contact with each other, and FIG. 3B is a diagram showing the first electrode 2 and the photoconductive structure. It is a figure which shows the energy band structure after the organic organic thin film layer 3 contacted.

  Now, the work function of the first electrode 2 is Φm, the ionization potential of the photoconductive organic thin film layer 3 made of a hole transporting material is Ip, and the lowest occupied molecular orbital of the photoconductive organic thin film layer 3 (Lowest Unoccupied Molecular). Orbital: LUMO) and the highest occupied molecular orbital (HOMO). In addition, both Fermi levels are denoted as Ef.

  In the photoconductive organic thin film layer 3, the ionization potential Ip indicates an energy difference between the vacuum level (VL) and the highest occupied molecular orbital HOMO, while the first electrode 2. Is the energy difference between the vacuum level VL and the Fermi level Ef (see, for example, “Organic Thin Film Work Function Data Collection”, page 6 of CMC Publishing).

  Based on the above definition, the magnitude of the energy function of the work function Φm of the first electrode 2 and the ionization potential Ip of the photoconductive organic thin film layer 3 made of a hole transporting material is Ip <Φm think of. The energy band structure of both before contact is in the state shown in FIG. 3 (a), but when in contact and in equilibrium, the two Fermi levels are shifted so as to coincide with each other to the state shown in FIG. 3 (b). It is considered to be. In this state, in the photoconductive organic thin film layer 3 made of a hole transporting material, holes that are majority carriers can easily move to the first electrode 2 side because there is no potential barrier at the interface. Is possible. When it becomes a state close to ohmic contact in the semiconductor theory and a positive voltage is applied to the first electrode, the dark current N also increases in proportion to the magnitude of the voltage. When the magnitude of the applied voltage is increased in this state, the photo-induced current S increases, but the dark current N also increases in the same manner. As a result, the ratio of the dark current N to the photo-induced current S (S / N ratio) does not increase. In order to improve the S / N ratio, it is necessary to suppress the dark current N, and for this purpose, it is necessary to form a potential barrier at the interface. Therefore, as a method of reducing the dark current N, a method of positively controlling the potential barrier height so that the magnitude of energy satisfies the relationship of Ip> Φm can be considered.

[If Ip> Φm]
On the other hand, FIG. 4 shows the energy band structure when the work function Φm of the first electrode 2, the ionization potential Ip of the photoconductive organic thin film layer 3 made of a hole transporting material, and the magnitude of the energy is Ip> Φm. Will be described. 4A is a diagram showing an energy band structure before the first electrode 2 and the photoconductive organic thin film layer 3 are in contact with each other, and FIG. 4B is a diagram showing the first electrode 2 and the photoconductive layer. It is a figure which shows the energy band structure in a thermal equilibrium state after the organic organic thin film layer 3 contacts. FIG. 4C is a diagram showing an energy band structure when a positive voltage is applied to the first electrode 2 in the state of FIG.

  As shown in FIG. 4A, the magnitude of the energy of the work function Φm of the first electrode 2 and the ionization potential Ip of the photoconductive organic thin film layer 3 made of a hole transporting material is Ip> Φm It is a relationship. The Fermi level Ef of the photoconductive organic thin film layer 3 is located in the energy gap Eg between HOMO and LUMO. Further, Ef is basically located at an energy close to HOMO. Since the Fermi level Ef of the first electrode 2 is located at Φm from the vacuum level VL, it is located at an energy higher than the Fermi level Ef of the photoconductive organic thin film 3.

  Then, as shown in FIG. 4B, when the first electrode 2 and the photoconductive organic thin film layer 3 come into contact with each other, the Fermi levels are shifted so as to coincide with each other. Holes that are majority carriers in the conductive organic thin film layer 3 cannot easily move to the first electrode 2 side because of the high potential barrier Φb. In addition, since the holes at the interface also have potential barriers, they move away from the first electrode 2.

  Furthermore, as shown in FIG. 4C, when a positive voltage is applied to the first electrode 2, the band is inclined. By setting the applied voltage V to the first electrode 2 to + Va, the height of the potential barrier is increased compared to V = 0, and the dark current is suppressed. When light enters the photoconductive organic thin film layer 3 in this state, electrons move to the first electrode 2 and holes move to the second electrode 1, and a photo-induced current flows. In addition, holes which are majority carriers in the photoconductive organic thin film layer 3 cannot move to the first electrode 2. Therefore, it is considered that, when a positive voltage is applied to the first electrode 2, holes cannot move, and therefore the dark current N is suppressed.

  That is, the potential barrier is positively set so that the work function Φm of the first electrode 2 and the ionization potential Ip of the photoconductive organic thin film layer 3 made of the hole transporting material satisfy the relationship of Ip> Φm. By forming the dark current, it becomes difficult to overcome the potential barrier and is suppressed. Furthermore, by applying a voltage between the electrodes, the potential barrier can be further increased and the dark current can be further suppressed. Therefore, the ratio (S / N ratio) between the dark current N and the photoinduced current S can be greatly improved by increasing the photoinduced current S.

[Formation of ion-doped surface 5 satisfying the relationship of Ip> Φm]
Next, formation of the ion doped surface 5 that satisfies the relationship of Ip> Φm will be described. In order to satisfy the relationship of Ip> Φm, in general, the work function Φm of the first electrode 2 is smaller than the ionization potential Ip of the photoconductive organic thin film layer 3 made of a hole transporting material (for example, It is theoretically possible to select a metal material) and form a thin film. However, metal materials with small Φm are very active and cannot exist stably in the atmosphere, and a continuous vacuum process is required to form a series of films including electrodes, resulting in high costs. End up.

  Furthermore, it is basically difficult to control at an arbitrary size such that Ip> Φm, and in particular, it is impossible to further increase the potential barrier height Φb to 0.5 eV or more.

  In the present application, a treatment surface that satisfies the relationship of Ip> Φm is positively provided on the first electrode 2 surface or the photoconductive organic thin film 3 surface to form a potential barrier height of an arbitrary size. It was discovered after intensive study. The treatment surface that satisfies the relationship of Ip> Φm in the present application is specifically an ion-doped surface obtained by doping hydroxide ions with respect to the first electrode 2 surface or the photoconductive organic thin film 3 surface. This can be achieved.

Specific examples of the hydroxide ions include NaOH, KOH, NH ₃ , and the like. As a method for the doping treatment, the hydroxide ions are immersed in an aqueous solution containing the hydroxide ions for an arbitrary time. Or by exposing the vapor of the aqueous solution. Further, the doping treatment conditions of hydroxide ions can include concentration (pH value), temperature, and treatment time. For example, as an example of ion doping the surface of the first electrode 2 using an aqueous NaOH solution, This is possible by setting pH = 10, temperature = room temperature, and processing time = 10 seconds. In this case, a polyethylenedioxythiophene (PEDOT) / polystyrene sulfonic acid (PSS) thin film, which is a π-conjugated polymer having a thickness of 100 nm, was used for the first electrode 2. The ionization potential Ip at that time was reduced by 0.6 eV (before treatment: 5.2 eV, after treatment: 4.6 eV).

  The reason why the ionization potential Ip is reduced by forming the ion-doped surface 5 is not necessarily clear at the present time, but is generally considered as follows. That is, it is considered that a positively charged cation is generally induced immediately after the hydroxide ion (OH-) is doped to maintain electrical neutrality (formation of an electric double layer). When such a situation is established, electrons are easily emitted from the electrode surface to the outside, and as a result, the ionization potential Ip is reduced. Note that the ionization potential Ip is defined in terms of molecular theory as energy necessary for extracting electrons from neutral atoms to the outside.

[Ion doped surface 5 satisfying a difference of 0.5 eV or more in the relation of Ip> Φm]
FIG. 5 is a diagram showing the relationship between the energy difference between Ip and Φm and the S / N ratio.

  The effect of satisfying the relationship of Ip> Φm and satisfying the difference in energy magnitude between Ip and Φm of 0.5 eV or more will be described with reference to FIG. Here, a polydiacetylene dioxide (PEDOT) / polystyrene sulfonic acid (PSS) thin film which is a π-conjugated polymer is used as the first electrode 2, and polycopper phthalocyanine (PCuPc) is used as the photoconductive organic thin film layer 3. ITO (indium tin oxide) is used as the second electrode 4, and the ion-doped surface 5 is formed with respect to the surface of the first electrode 2. All the layer thicknesses are 100 nm. Hereinafter, for the sake of explanation, this element is abbreviated as (PEDOT / PSS) / PCuPc / ITO.

  In addition, the work functions Φm and Ip of the PEDOT / PSS thin film as the first electrode 2 and the PCuPc layer as the photoconductive organic thin film layer 3 are measured by photoelectron spectroscopy (manufactured by Riken Keiki Co., Ltd., AC-2). The value of work function Φm of the PEDOT / PSS thin film was 5.1 eV, and the value Ip of the ionization potential of the PCuPc layer was 4.9 eV. On the other hand, in order to actively form a potential barrier at the interface between the PEDOT / PSS of the first electrode 2 and the PCuPc of the photoconductive organic thin film layer 3, the work of the PEDOT / PSS thin film of the first electrode 2 is performed. The value of the function Φm was controlled so as to decrease the energy of the work function Φm (immersion processing time: large) by changing the time for doping by immersing in an aqueous NaOH solution (before treatment: 5 .1 eV, after treatment: 4.8 eV, 4.7 eV, 4.5 eV, 4.4 eV, 4.3 eV, 4.1 eV). The concentration of the NaOH aqueous solution was constant at pH = 10.

In FIG. 5, the horizontal axis represents the energy of the work function Φm of the first electrode 2 (PEDOT / PSS thin film) and the ionization potential Ip = 4.9 eV of the photoconductive organic thin film layer 3 (PCuPc). Taking the difference of magnitude | Φm−Ip | and taking the ratio of the dark current value N expressed in the (PEDOT / PSS) / PCuPc / ITO element and the photoinduced current value S (S / N ratio) as the vertical axis, The relationship between the two is plotted. The dark current value N and the photoinduced current value S were measured by applying an applied voltage of 6 V (electric field intensity E = 6 × 10 ⁵ V / cm), an irradiation light wavelength of 470 nm, an irradiation light intensity of 10 μW / cm ² , and under vacuum (10 ^-3 Torr). As apparent from FIG. 5, the S / N ratio gradually increases when | Φm−Ip | is from 0.1 eV to 0.4 eV, but clearly when | Φm−Ip | is 0.5 eV or more. The S / N ratio increases, and an S / N ratio of 20 or more can be secured. When the S / N ratio is 20 or less, when the ambient temperature of the light receiving element rises, the dark current value N generally increases and stable practical performance cannot be secured.

  Therefore, in general, if the S / N ratio can be ensured to be 20 or more, more preferably about 50, it is evaluated as sufficient performance as a light receiving element. Therefore, the energy magnitudes of Ip and Φm satisfy Ip> Φm, and The organic thin film light receiving element 10 having the ion doped surface 5 processed so that the difference in energy size satisfies 0.5 eV or more is at a sufficiently practical level.

  FIG. 6 is a graph showing the relationship between the energy difference between Ip and Φm and the S / N ratio.

  Further, a positive voltage is applied to the (PEDOT / PSS) layer, which is the first electrode 2 subjected to the ion doping process, with respect to the (PEDOT / PSS) / PCuPc / ITO element having the ion doped surface 5, and the voltage FIG. 6A shows data in which the ratio (S / N ratio) between the dark current N and the photoinduced current S when V is changed from 0.1 V to 10 V is plotted. As is clear from FIG. 6A, the dark current Id increases suddenly as the voltage increases when a low voltage is applied, but is almost saturated when the applied voltage is 6 V or higher. In contrast, the photoinduced current Iph1 (PCuPc) is not so large when a low voltage is applied, but gradually increases as the applied voltage increases. As described above, this is considered to be due to the increase of the photo-induced current due to the dark current being suppressed by the formation of the potential barrier.

Also, FIG. 6B is a rewrite of the relationship between the electric field intensity E and the S / N ratio from the data of FIG. It can be seen that when the electric field intensity E becomes 10 ⁶ V / cm, the S / N ratio increases greatly and improves to about 80.

  In this way, by forming a potential barrier at the interface between the first electrode 2 and the photoconductive organic thin film layer 3 and applying a positive voltage to the first electrode 2, the dark current N is reduced. It has been clarified that an S / N ratio of 20 or more can be secured by suppressing and increasing the photoinduced current S.

[Organic thin film light emitting / receiving element 30]
As shown in FIG. 1, the organic thin film light emitting / receiving element 30 includes the organic thin film light receiving element 10 and the organic thin film light emitting element 20 on the same substrate 1. Light 8 having a specific wavelength emitted from the organic thin film light emitting element 20 is incident on the object 40, and the reflected light 8 is detected by the organic thin film light receiving element 10, whereby weakly reflected light from the object 40 to be detected is S. / N ratio can be detected.

  The organic thin film light emitting element 20 is, for example, an organic EL element. As the light emitting element, in addition to the organic thin film light emitting element 20, an inorganic semiconductor such as an inorganic LED or a laser, or an organic material may be used. However, when the detection object is not a flat body but applied to a curved body, A light receiving / emitting element in which both the light receiving element 10 and the light emitting element 20 are formed on the flexible substrate 1 is desirable. From such a viewpoint, the light emitting element 20 is also preferably an organic thin film light emitting element.

  FIG. 7 is a schematic cross-sectional view for explaining the organic thin film light emitting / receiving element 30 according to the present embodiment.

  As shown in FIG. 7, the organic thin film light emitting element 20 includes a first electrode 21 formed on the substrate 1, an organic semiconductor light emitting layer 23 made of an organic semiconductor material formed on the first electrode 21, and an organic semiconductor. A second electrode 24 formed on the light emitting layer 23 is provided. By applying a voltage between the first electrode 21 and the second electrode 24, the light 8 is output from the organic semiconductor light emitting layer 23.

  Although the material of the 1st electrode 21 and the 2nd electrode 22 is not specifically limited, The material which has a light transmittance is used for the electrode of the surface which inject | emits light from the objective of injecting light.

Examples of such materials include inorganic oxides such as SnO ₂ (tin oxide), ZnO (zinc oxide), and FTO (F-doped tin oxide) in addition to ITO (indium tin oxide) which is an inorganic transparent electrode material. You may apply things. Alternatively, various conductive polymers such as polypyrrole (PPy), polyethylenedioxythiophene (PEDOT) / polystyrene sulfonic acid (PSS), polythiophene, and carbon nanotube dispersion can also be applied.

  An organic semiconductor material system for the organic semiconductor light emitting layer 23 of the organic thin film light emitting element 20 will be described. Examples of the organic semiconductor material system include polyphenylene derivatives, polyfluorene derivatives, triphenylamine derivatives, benzidine derivatives, pyrazoline derivatives, styrisamine derivatives, oxadiazole derivatives, triazole derivatives, silole derivatives, and the like.

  The organic thin film light receiving / emitting element 30 in which the organic thin film light receiving element 10 and the light emitting element 20 are combined will be described. By forming the organic thin film light receiving element 10 and the light emitting element 20 on the same substrate 1, light 8 having a specific wavelength emitted from the light emitting element 20 is incident on the object 40, and the weakness from the object to be detected is weakened. The light emitting / receiving element 30 capable of detecting reflected light with a high S / N ratio can be provided.

[Organic thin film light emitting / receiving element array 40]
FIG. 8 is a diagram for explaining the organic thin film light emitting and receiving element array 40 according to the present embodiment. As shown in FIG. 8, the organic thin film light emitting / receiving element array 40 has a configuration in which a plurality of organic thin film light emitting / receiving elements 30 are arranged on a substrate. In FIG. 8, they are regularly arranged. However, the arrangement is not limited to this, and they may be arranged at an arbitrary place.

  Here, although all show what provided the light shielding body 25, it is not limited to this, The light shielding body 25 does not need to be provided. The light shield 25 is installed between the two elements so that the light output from the organic thin film light emitting element 20 does not directly enter the organic thin film light receiving element 10, and prevents a decrease in light receiving sensitivity of the organic thin film light receiving element 10 due to light leakage. . The light shield 25 is preferably made of a material having low light transmissivity. For example, a polyimide resin having a brown color or a member in which carbon or the like is dispersed in a resin to exhibit a dark color is preferable. The shape and size of the light shield 25 can be formed in any shape and size so as to be adapted to the organic thin film light emitting element 20 and the organic thin film light receiving element 10 and to reduce light leakage as much as possible.

  FIG. 8A shows a plurality of organic thin film light emitting / receiving elements 30 each having a rectangular organic thin film light receiving element 10 and an organic thin film light emitting element 20, and FIG. 8B shows a circular organic thin film light emitting element 30. A plurality of organic thin film light emitting / receiving elements 30 each including a light receiving element 10 and a rectangular organic thin film light emitting element 20 are arranged. In FIGS. 8A and 8B, the pair of organic thin film light emitting / receiving elements 30 includes only one organic thin film light receiving element 10 and one organic thin film light emitting element 20, but The light emitting element 30 may include at least one organic thin film light receiving element 10. By using the organic thin film light emitting / receiving element array 40 in which a plurality of organic thin film light emitting / receiving elements 30 each having at least one organic thin film light receiving element 10 are arranged, a wide range and high accuracy detection is further possible.

  This makes it possible to easily and accurately detect light from any part and any size, not limited to a specific part of the subject. Furthermore, from the viewpoint of future flexibility, wearability, and ubiquity, the organic thin film light emitting / receiving element array 40 includes the plurality of organic thin film light receiving elements 10 and the organic thin film even when the subject is not fixed and is moving. Since the light emitting element 20 is provided, light can be detected.

  Thus, by using the organic thin film light emitting / receiving element array 40 in which a plurality of pairs of organic thin film light emitting / receiving elements 30 are arranged on the base material, for example, pulse fluctuations can be obtained from any part in contact with the palm or finger. It can be detected stably and with high accuracy.

[Pulse sensor 50]
FIG. 9 is a diagram for explaining the pulse sensor 50 according to the present embodiment.

  The organic thin film light emitting / receiving element 30 or the organic thin film light emitting / receiving element array 40 can be used, for example, in the form of a pulse sensor 50 that detects a pulse from arterial blood of a living body as a photoelectric pulse wave as one practical example. For example, the organic thin film light emitting / receiving element 30 of the present application can be attached to a peripheral portion such as an earlobe, a palm, a finger, etc., and a pulse wave signal can be detected by a reflection type photoelectric pulse wave signal. 9A and 9B are schematic views of the pulse sensor 50 and its pulse wave signal detection.

  The pulse sensor 50 is disposed so that the surface of the organic thin film light emitting / receiving element 30 on which the organic thin film light emitting element 20 and the organic thin film light receiving element 10 are located is in contact with a living body 45 (for example, a fingertip) as a subject. The living body 45 is irradiated with light from the organic thin film light emitting element 20. Then, the light is received by the organic thin film light receiving element 30 through interactions such as reflection, absorption, and transmission on the living body surface and in the living body. As shown in FIG. 9B, the organic thin film light receiving element 30 outputs a pulse wave signal according to the intensity of light reflected by hemoglobin in arterial blood flowing in the living body 45. Since the amount of hemoglobin in arterial blood changes due to pulsation, the pulse can be calculated from the relationship between the pulse wave signal and time.

[vehicle]
The organic thin film light emitting / receiving element 30 having the organic thin film light receiving element 10 can be mounted on a vehicle, for example, in the form of the pulse sensor 50 described above.

  FIG. 10 is a diagram for explaining the vehicle according to the present embodiment. In FIG. 10, the vehicle which provided the pulse sensor 50 in the steering wheel 60 of a vehicle can be provided.

  Such a pulse sensor 50 can be disposed on the steering wheel 60 of the vehicle. This is because the organic thin-film light-emitting / receiving element 30 itself having the organic thin-film light-receiving element 10 is very flexible, so that it can be disposed so as to be almost completely covered by the curved surface of the steering wheel 60. For this reason, the pulse sensor 50 can be disposed without giving the driver a sense of incongruity with the normal steering wheel 60 at all.

  The arrangement of the organic thin film light emitting / receiving elements 30 having the organic thin film light receiving elements 10 is most preferably a plurality of disposed throughout the steering wheel 60. As a result, as long as the driver holds the steering wheel 60, the pulse can be continuously detected and monitored from the palm of the hand or finger regardless of where the driver is holding or with one hand. Moreover, you may make it arrange | position not only in the whole but only in the part corresponded to the home position of what is called a driver | operator's hand.

  Thus, by disposing the pulse sensor 50 on the steering wheel 60, the biological information of the driver can be measured as a pulse. Therefore, by analyzing the pulse signal itself or a combination result with other physiological information (respiration, blood pressure, etc.), it can be used for detection of the driver's health level, fatigue, stress, and the like.

  In addition, by providing the pulse sensor 50 on door knobs, armrests, handrails, straps and the like that are touched by passengers including the driver, the present invention can be applied not only to the driver but also to the passenger.

  As described above, the organic thin film light emitting / receiving element 30 having the organic thin film light receiving element 10 is a non-invasive and real-time optical technique for various biological information (fatigue, stress, comfort level, etc.) of the driver or passenger in the vehicle. A monitor such as a pulse sensor and autonomic nerve activity can be provided for the movement to be measured. For example, it is useful for a biological information detection device or means for detecting weak light such as a change in absorbance of hemoglobin in blood or biophotons (bioluminescence) emitted from the human body. In particular, when an organic thin film light emitting / receiving element 30 having an organic thin film light receiving element 10 is arranged on the skin of a steering wheel having a curved surface shape, a vehicle capable of detecting faint light from a driver's bare hands with low voltage and high accuracy is provided. be able to.

  As described above, since the organic thin-film light receiving element 10 of the present invention is driven at a low voltage, suppresses dark current, and improves photoinduced current sensitivity, weak light is highly sensitive (S / N ratio 20). It became detectable in the above. In addition, by using a soluble polymer for the electrode and the photoconductive organic thin film layer 3 applied to the organic thin film light receiving element 10, it is possible to directly form the element on the substrate 1 using a printing technique such as inkjet. Cost reduction can also be achieved.

  Furthermore, by using the organic thin film light receiving / emitting element 30 in which the organic thin film light receiving element 10 and the light emitting element 2 are combined, a biological signal (for example, a pulse wave signal) can also be detected and disposed on the steering wheel of the vehicle. Thus, the pulse wave signal can be monitored with high accuracy and stability from the driver's bare hands (eg, palm or finger).

[Second Embodiment]
FIG. 11 is a schematic cross-sectional view for explaining the photoconductive nanorods 9 or nanotubes 9 according to the present embodiment.

  In the present embodiment, the photoconductive organic thin film layer 3 is dispersed in the photoconductive nanorods 9 or nanotubes 9 having the ability to absorb light of a specific wavelength and generate and transport photocarriers. It is possible to increase the current. Dispersing the nanorods 9 and the nanotubes 9 in the photoconductive organic thin film layer 3 increases the number of those having hole transportability, so that the photoinduced current can be increased. Further, as the aspect ratio of the nanorods 9 and the nanotubes 9 increases, the photoinduced current also tends to increase. Although the reason for this is not yet clear, it is considered that incident light is efficiently absorbed and contributes to an increase in the number of optical carriers. Further, since the aspect ratio is large, it is considered that a conductive path of the generated optical carrier is secured and contributes to improvement of mobility (reduction of deactivation of the optical carrier). As an aspect ratio of such a carbon nano lot, for example, 10 can be mentioned.

  Further, as described above, the photoconductive nanorod 9 or the nanotube 9 is preferably a hole transporting material in which majority carriers are holes. Examples of the hole transporting material include phthalocyanine derivatives, porphyrin derivatives, merocyanine derivatives, quinacridone derivatives, triphenyl diamine derivatives and mixtures thereof, or polyethylenedioxythiophene (PEDOT) / polystyrene sulfonic acid (PSS), polythiophene, Examples thereof include conductive polymers such as polyaniline (PANI), polypyrrole (PPy), and polyselenophene. Among these, phthalocyanine derivatives, porphyrin derivatives, merocyanine derivatives, quinacridone derivatives, triphenyl diamine derivatives and the like have strong absorption sensitivity in the visible light region and are preferable from the viewpoint of generation of photocarriers.

  More specific examples of the photoconductive nanorods 9 or nanotubes 9 include carbon nanorods, titanium oxide nanorods, carbon nanotubes, nanorods or nanotubes of various compound semiconductors, and the like. In particular, carbon nanorods, titanium oxide nanorods, and carbon nanotubes are more preferably photoconductive, and further, the energy difference between the photoconductive organic thin film layer 3 and the nanorods 9 or nanotubes 9 is small.

  The effect will be described in detail with reference to FIG. FIG. 6A shows an organic material in which carbon nanorods having an aspect ratio of 10 are dispersed as a photoconductive organic thin film layer 3 as a nanorod 9 having a hole transport property in a polycopper phthalocyanine (PCuPc) layer. The relationship between the applied voltage of the thin film light receiving element 10 and the photoinduced current is inserted.

  As is apparent from FIG. 6, in addition to the effect of forming a potential barrier at the interface between the first electrode 2 and the photoconductive organic thin film layer 3, the photoconductive nanorods 9 are dispersed to thereby generate a photoinduced current. It can be seen that is increasing. In particular, the increase becomes significant when the applied voltage is 2 V or more, and when the applied voltage is 10 V, it can be increased by an order of magnitude compared to the photo-induced current when only the potential barrier is formed.

FIG. 6B is a graph in which the data is rearranged from the relationship of FIG. 6A and the relationship between the electric field strength E and the S / N ratio is plotted. The S / N ratio gradually increases when the electric field intensity E is from 10 ³ V / cm to about 10 ⁵ V / cm, whereas the S / N ratio increases remarkably when the electric field intensity E is 10 ⁵ V / cm or more. The S / N ratio at E = 10 ⁶ V / cm reaches a level exceeding 10 ³ . Note that the dispersion amount of the nanorods 9 or the nanotubes 9 must be appropriately examined in consideration of the type and size used. In particular, the surface treatment of the nanorods 9 or the nanotubes 9 may be performed so that the photoconductive organic thin film layer 3 can be uniformly dispersed in consideration of the affinity with the π-conjugated polymer, the thickness of the layer, and the like.

  As described above, by dispersing the photoconductive nanorods 9 or the nanotubes 9, it becomes possible to dramatically increase the S / N ratio, and the organic thin film light receiving element 10 is extremely used for detecting weak light. It is valid.

[Example]
Hereinafter, the organic thin-film light receiving element 10 according to the present embodiment will be specifically described based on examples, but the present invention is not limited to the illustrated examples.

(Evaluation)
(1) Measurement of work function and ionization potential
The work function Φm of the first electrode 2 formed on the substrate 1 and the value of the ionization potential Ip of the photoconductive organic thin film layer 3 (values before and after the ion doping process) are both photoelectron spectrometers (manufactured by Riken Keiki Co., Ltd.). , AC-2).

(2) Measurement of dark current and photo-induced current
The dark current N and the photo-induced current S of the produced organic thin film light receiving element 10 were both placed in a cryostat in a room temperature at a constant temperature and performed in a vacuum state (10 ⁻³ Torr). The light irradiation during the measurement of the photoinduced current S was monochromatic light having a wavelength of 470 nm and a light intensity of 10 μW / cm ² . The applied voltage at the time of dark current measurement and photoinduced current measurement was such that the first electrode 2 was a positive voltage, and the applied voltage was constant at 10V.

  The ratio of S (photo-induced current) / N (dark current) was calculated from the difference between the dark current N and the photo-induced current S. The results obtained in the following examples and comparative examples are summarized in Table 1.

(Example 1)
In order to form the organic thin film light receiving element 10 shown in FIG. First, a 250 μm thick polyethylene terephthalate (PET) film was prepared as the flexible substrate 1.

  Next, Pt was formed to a thickness of 100 nm on the PET film by a vacuum deposition method to form the first electrode 2. Thereafter, hydroxide ion doping treatment (NaOH aqueous solution concentration: pH = 10, solution temperature: room temperature, immersion time: 10 seconds) is performed on the surface of the Pt thin film, and drying is performed at 80 ° C. to form the ion doping treatment surface 5. did.

  Further, a polycopper phthalocyanine (PCuPc) thin film having a hole transporting property was formed on the treated surface 5 to a thickness of 100 nm by using an ink jet apparatus, thereby forming a photoconductive organic thin film layer 3. Subsequently, a transparent conductive film ITO was formed on the photoconductive organic thin film layer 3 by a sputtering method to a thickness of 100 nm to form the second electrode 4, thereby manufacturing the organic thin film light receiving element 10. The processes after the ion doping process were all performed in a glow box in an Ar atmosphere (the same process was performed in the following examples, and thus omitted).

(Example 2)
In order to form the organic thin film light receiving element 10 shown in FIG. First, a 250 μm thick polyethylene terephthalate (PET) film was prepared as the flexible substrate 1.

  Next, polyaniline (PANI), which is a π-conjugated polymer, was formed to a thickness of 100 nm on the PET film by an ink jet method to form the first electrode 2. Thereafter, hydroxide ion doping treatment (NaOH aqueous solution concentration: pH = 10, solution temperature: room temperature, immersion time: 6 seconds) is performed on the surface of the PANI thin film, and drying is performed at 80 ° C. to form the ion doping treatment surface 5. did.

  Further, a polycopper phthalocyanine (PCuPc) thin film having a hole transporting property was formed on the treated surface 5 to a thickness of 100 nm by an ink jet method to obtain a photoconductive organic thin film layer 3. Subsequently, a transparent conductive film ITO was formed on the photoconductive organic thin film layer 3 by a sputtering method to a thickness of 100 nm to form the second electrode 4, thereby manufacturing the organic thin film light receiving element 10.

(Example 3)
In order to form the organic thin film light receiving element 10 shown in FIG. First, a 250 μm thick polyethylene terephthalate (PET) film was prepared as the flexible substrate 1.

  Next, polyaniline (PANI), which is a π-conjugated polymer, was formed to a thickness of 100 nm on the PET film by an ink jet method to form the first electrode 2. Thereafter, hydroxide ion doping treatment (NaOH aqueous solution concentration: pH = 10, solution temperature: room temperature, immersion time: 10 seconds) is applied to the surface of the PANI thin film, and drying is performed at 80 ° C. to form an ion doping treatment surface 5. did.

  Further, a polycopper phthalocyanine (PCuPc) thin film having a hole transporting property was formed on the treated surface 5 to a thickness of 100 nm by an ink jet method to obtain a photoconductive organic thin film layer 3. Subsequently, a transparent conductive film ITO was formed on the photoconductive organic thin film layer 3 by a sputtering method to a thickness of 100 nm to form the second electrode 4, thereby manufacturing the organic thin film light receiving element 10.

(Example 4)
In order to form the organic thin film light receiving element 10 shown in FIG. First, a 250 μm thick polyethylene terephthalate (PET) film was prepared as the flexible substrate 1.

  Next, polyaniline (PANI), which is a π-conjugated polymer, was formed to a thickness of 100 nm on the PET film by an ink jet method to form the first electrode 2. Thereafter, hydroxide ion doping treatment (NaOH aqueous solution concentration: pH = 10, solution temperature: room temperature, immersion time: 20 seconds) is performed on the surface of the PANI thin film, and drying is performed at 80 ° C. to form an ion doping treatment surface 5. did.

  Further, a polycopper phthalocyanine (PCuPc) thin film having a hole transporting property was formed on the treated surface 5 to a thickness of 100 nm by an ink jet method to obtain a photoconductive organic thin film layer 3. Subsequently, a transparent conductive film ITO was formed on the photoconductive organic thin film layer 3 by a sputtering method to a thickness of 100 nm to form the second electrode 4, thereby manufacturing the organic thin film light receiving element 10.

(Example 5)
In order to form the organic thin film light receiving element 10 shown in FIG. 2A, the following materials were selected as the material of each layer of the element. First, a 250 μm thick polyethylene terephthalate (PET) film was prepared as the flexible substrate 1.

  Next, polyethylene dioxythiophene (PEDOT / PSS), which is a π-conjugated polymer, was formed to a thickness of 100 nm on the PET film by an ink jet method to form the first electrode 2. Thereafter, hydroxide ion doping treatment (NaOH aqueous solution concentration: pH = 10, solution temperature: room temperature, immersion time: 10 seconds) is applied to the surface of the PEDOT / PSS thin film, and drying is performed at 80 ° C. Formed.

  Further, a polycopper phthalocyanine (PCuPc) thin film having a hole transporting property was formed on the treated surface 5 to a thickness of 100 nm by an ink jet method to obtain a photoconductive organic thin film layer 3. Subsequently, a transparent conductive film PEDOT / PSS was formed to a thickness of 100 nm on the photoconductive organic thin film layer 3 by an ink jet method to form the second electrode 4, thereby manufacturing the organic thin film light receiving element 10.

(Comparative Example 1)
In order to form the organic thin film light receiving element 10 shown in FIG. First, a 250 μm thick polyethylene terephthalate (PET) film was prepared as the flexible substrate 1.

  Next, Pt was formed to a thickness of 100 nm on the PET film by a vacuum deposition method to form the first electrode 2. Thereafter, a polycopper phthalocyanine (PCuPc) thin film having a hole transporting property was formed on the first electrode 2 to a thickness of 100 nm by an ink jet method to obtain a photoconductive organic thin film layer 3. Subsequently, a transparent conductive film ITO was formed on the photoconductive organic thin film layer 3 by a sputtering method to a thickness of 100 nm to form the second electrode 4, thereby manufacturing the organic thin film light receiving element 10. Note that the processes after the formation of the first electrode 2 were all performed in a glow box in an Ar atmosphere (the same process was performed in the following comparative examples, and thus omitted).

(Comparative Example 2)
In order to form the organic thin film light receiving element 10 shown in FIG. First, a 250 μm thick polyethylene terephthalate (PET) film was prepared as the flexible substrate 1.

  Next, on the PET film, polyaniline (PANI), which is a π-conjugated polymer, was formed to a thickness of 100 nm by an inkjet method to form a first electrode 2. Thereafter, a polycopper phthalocyanine (PCuPc) thin film having a hole transporting property was formed on the first electrode 2 to a thickness of 100 nm by an ink jet method to obtain a photoconductive organic thin film layer 3. Subsequently, a transparent conductive film ITO was formed on the photoconductive organic thin film layer 3 by a sputtering method to a thickness of 100 nm to form the second electrode 4, thereby manufacturing the organic thin film light receiving element 10.

(Comparative Example 3)
In order to form the organic thin film light receiving element 10 shown in FIG. First, a 250 μm thick polyethylene terephthalate (PET) film was prepared as the flexible substrate 1.

  Next, polyethylene dioxythiophene (PEDOT / PSS), which is a π-conjugated polymer, was formed to a thickness of 100 nm on the PET film by an ink jet method to form the first electrode 2. Thereafter, a polycopper phthalocyanine (PCuPc) thin film having a hole transporting property was formed on the first electrode 2 to a thickness of 100 nm by an ink jet method to obtain a photoconductive organic thin film layer 3. Subsequently, a transparent conductive film PEDOT / PSS was formed to a thickness of 100 nm on the photoconductive organic thin film layer 3 by an ink jet method to form the second electrode 4, thereby manufacturing the organic thin film light receiving element 10.

It is a conceptual diagram with which it uses for description of the organic thin film light emitting / receiving element 30 which has the organic thin film light receiving element 10 which concerns on 1st Embodiment of this invention. It is a schematic sectional drawing with which it uses for description of the organic thin film light receiving element 10 by this embodiment. It is an energy band schematic diagram with which it uses for description of the ion dope surface 5 with which the organic thin film light receiving element 10 by this embodiment is equipped. It is an energy band schematic diagram with which it uses for description of the ion dope surface 5 with which the organic thin film light receiving element 10 by this embodiment is equipped. It is the figure which showed the relationship between the energy difference of Ip and (PHI) m, and S / N ratio. It is the figure which showed the relationship between the energy difference of Ip and (PHI) m, and S / N ratio. It is a schematic sectional drawing with which it uses for description of the organic thin film light emitting / receiving element 30 by this embodiment. It is a figure where it uses for description of the organic thin film light emitting and receiving element array 40 by this embodiment. It is a figure where it uses for description of the pulse sensor 50 by this embodiment. It is a figure where it uses for description of the vehicle by this embodiment. FIG. 3 is a schematic cross-sectional view for explaining a photoconductive nanorod 9 or a nanotube 9 according to the present embodiment.

Explanation of symbols

1 substrate,
2 first electrode;
3 photoconductive organic thin film layer,
4 second electrode,
5 ion-doped surface,
6 voltage,
7 Microammeter,
8 Light,
9 photoconductive nanorods or nanotubes,
10 Organic thin film light receiving element,
20 Organic thin film light emitting device,
25 light shield,
30 Organic thin film light emitting / receiving element,
40 Organic thin film light emitting / receiving element array,
50 pulse sensor,
60 Steering wheel.

Claims (14)

An optical carrier that absorbs incident light that is interposed between the first electrode and the second electrode, and the first electrode and the second electrode, at least one of which is light transmissive, on the substrate. A photoconductive organic thin film layer that produces
At least one of the first electrode and the photoconductive organic thin film layer includes an ion-doped surface in which ions are doped at an interface between the first electrode and the photoconductive organic thin film layer,
The magnitude of the work function energy of the first electrode is smaller than the ionization potential energy of the photoconductive organic thin film layer,
An organic thin film light receiving element, wherein a voltage that is positively greater than that of the second electrode is applied to the first electrode.   2. The organic thin-film light receiving element according to claim 1, wherein the ion-doped surface doped in the first electrode is an ion-doped surface doped with hydroxide ions. 3.   2. The organic material according to claim 1, wherein the magnitude of the work function energy of the first electrode and the magnitude of the ionization potential energy of the photoconductive organic thin film layer have a difference of 0.5 eV or more. Thin film photo detector.   The organic thin-film light-receiving element according to claim 1, wherein the photoconductive organic thin-film layer includes a π-conjugated polymer.   5. The organic thin-film light-receiving element according to claim 1, wherein at least one of the first electrode and the second electrode includes a π-conjugated polymer.   6. The organic thin film light-receiving element according to claim 4, wherein the π-conjugated polymer is a hole transporting material in which a majority of carriers are holes.   The organic material according to claim 6, wherein the hole transporting material is one or more derivatives selected from the group consisting of phthalocyanine derivatives, porphyrin derivatives, merocyanine derivatives, quinacridone derivatives, and triphenyl-diamine derivatives. Thin film photo detector.   The photoconductive organic thin film layer absorbs light of a specific wavelength to generate a photocarrier, and a photoconductive nanorod or nanotube having an ability to transport the photocarrier is placed in the photoconductive organic thin film layer. The organic thin film light receiving element according to claim 1, wherein the organic thin film light receiving element is dispersed.   The organic thin film light receiving device according to claim 8, wherein the nanorods or nanotubes include one or more derivatives selected from the group consisting of phthalocyanine derivatives, porphyrin derivatives, merocyanine derivatives, quinacridone derivatives, and triphenyl-diamine derivatives. element.   The organic thin film light receiving element according to claim 9, wherein the nanorods or nanotubes are one or more mixtures selected from the group consisting of carbon nanorods, titanium oxide nanorods, and carbon nanotubes.   The organic thin film light receiving element according to any one of claims 1 to 10 and the organic thin film light emitting element having an emission spectrum peak in a light receiving sensitivity wavelength region of the organic thin film light receiving element are provided on the same substrate. An organic thin-film light emitting / receiving element.   An organic thin film light emitting / receiving element array, wherein two organic thin film light emitting / receiving elements according to claim 11 are arranged in pairs on a substrate. One or more selected from the group of the organic thin film light receiving / receiving element according to claim 1, the organic thin film light receiving / emitting element according to claim 11, and the organic thin film light receiving / emitting element array according to claim 12. Have
A pulse sensor characterized in that vibration of light irradiated from a living body is detected by an organic thin film light receiving element to measure the pulse of the living body.   A vehicle comprising the pulse sensor according to claim 13 arranged along a surface shape of a steering wheel.