JP5653658B2 - Organic photoelectric conversion device, organic thin film solar cell, and production method thereof - Google Patents

Description

  The present invention relates to an organic photoelectric conversion device, an organic thin film solar cell using the organic photoelectric conversion device, and a method for producing them.

  The photoelectric conversion device is used for a solar cell, for example. In recent years, in order to promote effective use of solar energy as alternative energy such as petroleum energy, development of solar cells that convert light energy into electric energy has been widely performed.

  Among them, organic solar cells are attracting attention because they have advantages such as low manufacturing cost, flexibility and weight reduction, and wide selection of materials compared to silicon-based inorganic solar cells. . On the other hand, the organic solar cell has a problem that the photoelectric conversion efficiency is low, and various studies have been made to solve the problem.

  As a photoelectric conversion device used for such an organic solar cell, there is an element structure having such a gradient that the content of the electron-accepting material contained in the photoelectric conversion region is high on the cathode side of the electrode and low on the anode side. It is known (see Patent Document 1).

JP 2004-165474 A

  In the element structure of the photoelectric conversion device disclosed in Patent Document 1, the content of the electron donating material is given a gradient so that carrier transportation between the electrodes can be performed efficiently. Here, in order to increase the photoelectric conversion efficiency, no consideration is given to the relationship between charge separation and carrier transport between electrodes.

  In view of such circumstances, the present invention provides an organic photoelectric conversion device, an organic thin-film solar cell, and a method for producing the same that can improve photoelectric conversion characteristics and improve photoelectric conversion efficiency. Objective.

The organic photoelectric conversion device of the present invention includes an organic photoelectric conversion layer including a p-type organic semiconductor and an n-type organic semiconductor, and the organic photoelectric conversion layer transports charges from one electrode to the other electrode. A region including a region where the p-type organic semiconductor and the n-type organic semiconductor are joined, and a pn junction area between the domain of the p-type organic semiconductor and the domain of the n-type organic semiconductor is a thickness of the organic photoelectric conversion layer A domain size gradient that expands toward a central region in the vertical direction, and a charge separation promoting region that promotes separation of charges transported to the charge transporting region, wherein the charge separation promoting region comprises the p-type organic semiconductor A p-type organic semiconductor rich region where there are more than the n-type organic semiconductor in the charge separation promoting region, and the n-type organic semiconductor is formed by the p-type organic semiconductor in the charge separation promoting region. The boundary between the charge separation promoting region on the p-type organic semiconductor rich region side or the n-type organic semiconductor rich region side and its vicinity is located between the n-type organic semiconductor rich region and the n-type organic semiconductor rich region. And the domain size gradient is formed from the charge transport region which is the p-type organic semiconductor rich region or the n-type organic semiconductor rich region to the charge separation promotion region ,
The domain size of the p-type organic semiconductor is reduced from the one electrode toward the other electrode, and the domain size of the n-type organic semiconductor is directed from the other electrode toward the one electrode. It is formed to be smaller Te characterized Rukoto. Moreover, this invention is applicable also to the organic thin film solar cell provided with such an organic photoelectric conversion device.

The method for producing an organic photoelectric conversion device of the present invention includes a step of forming a precursor layer having a gradient of a domain of a p-type organic semiconductor and a domain of an n-type organic semiconductor, and heat-treating the precursor layer. The region including the region where the p-type organic semiconductor and the n-type organic semiconductor are joined, and the pn junction area between the domain of the p-type organic semiconductor and the domain of the n-type organic semiconductor is the thickness direction of the organic photoelectric conversion layer Forming an organic photoelectric conversion layer by forming a domain size gradient that expands toward the central region, the organic photoelectric conversion layer having a charge transport region for transporting charges from one electrode to the other electrode And a charge separation promoting region for separating charges transported to the charge transporting region, wherein the charge separation promoting region is formed by the p-type organic semiconductor in the n-type organic semiconductor in the charge separation promoting region. Located between a p-type organic semiconductor rich region that is present more than the n-type organic semiconductor rich region in which the n-type organic semiconductor is present in a larger amount than the p-type organic semiconductor in the charge separation promoting region, The boundary of the charge separation promoting region on the p-type organic semiconductor rich region side or the n-type organic semiconductor rich region side and the vicinity thereof also serve as the charge transport region, and the domain size gradient is determined based on the p-type organic semiconductor rich region. A domain size of the p-type organic semiconductor is reduced from the one electrode toward the other electrode. And the domain size of the n-type organic semiconductor decreases from the other electrode toward the one electrode. Characterized in that the sea urchin formed.

  INDUSTRIAL APPLICATION This invention can aim at the improvement and stabilization of a photoelectric conversion characteristic, and there exists an effect that the improvement of a photoelectric conversion efficiency can be aimed at.

1 is a schematic cross-sectional view of an organic photoelectric conversion device according to Embodiment 1 of the present invention. 1 is a schematic cross-sectional view of an organic photoelectric conversion device according to Embodiment 1 of the present invention. The schematic sectional drawing of the organic photoelectric conversion device which concerns on Embodiment 2 of this invention. The schematic sectional drawing of the organic photoelectric conversion device which concerns on Embodiment 3 of this invention. The schematic sectional drawing of the organic thin-film solar cell concerning Embodiment 4 of this invention.

  Hereinafter, the present invention will be described in detail based on embodiments. The embodiment of the present invention described below is an example for explaining various concepts such as a superordinate concept, a middle concept, and a subordinate concept of the present invention. Therefore, the technical scope of the present invention is not limited to the following embodiments.

(Embodiment 1)
FIG. 1 is a schematic cross-sectional view showing a photoelectric conversion element which is an example of an organic photoelectric conversion device according to Embodiment 1 of the present invention.

As shown in FIG. 1, the organic photoelectric conversion device (organic photoelectric conversion element) 10 of the present embodiment can be deployed in an organic thin film solar cell, and between a pair of electrodes 1 and 2 and the pair of electrodes 1 and 2. And an organic photoelectric conversion layer 3 provided. The organic photoelectric conversion layer 3 is a layer that generates charges by incident light, and may have a single layer structure or a multilayer structure. For example, the organic photoelectric conversion layer 3 of the present embodiment has a single layer structure including a p-type organic semiconductor and an n-type organic semiconductor. The organic photoelectric conversion layer 3 is a layer domain size gradient is formed between the p-type organic semiconductor and the n-type organic semiconductor and includes an area for junction and the p-type organic semiconductor domains and n-type organic semiconductor domain In this case, the charge separation region and the charge transfer region from the charge separation region to the charge transport region are continuously formed by a domain size gradient. The organic photoelectric conversion layer 3 of the present embodiment is composed of, for example, a layer in which a domain size gradient is formed depending on the particle size (particle size). Specifically, the organic photoelectric conversion device 10 of this embodiment has a charge separation promoting region in which a domain size gradient is formed with respect to the organic photoelectric conversion layer 3 depending on the size of the pn particle diameter. Here, although the charge separation promoting region will be described in detail later, at least one of the average particle size of the p-type organic semiconductor and the average particle size of the n-type organic semiconductor changes with the position. It is an area that acts to ensure efficient transportation.

The organic photoelectric conversion device 10 of the present embodiment is to form an organic photoelectric conversion layer 3 by a layer the organic semiconductor is fused such that adjacent heteroconjugate junction region to layered bulk. The p-type organic semiconductor region P is substantially larger in the region on the electrode 1 side of the organic photoelectric conversion layer 3, and the p-type organic semiconductor region P is smaller as the region approaches the electrode 2 side of the organic photoelectric conversion layer 3. (FIG. 1 is a diagram schematically shown). In practice, the organic photoelectric conversion layer 3 forms a precursor layer (not shown) with a particle size so that a predetermined domain size gradient is formed, and charge separation having a domain size gradient by subsequent heat treatment or the like. A promotion region is formed. On the other hand, the n-type organic semiconductor region N is substantially smaller on the electrode 1 side and larger as it approaches the electrode 2 side of the organic photoelectric conversion layer 3.

  Accordingly, in the present embodiment, many pn particles having a relatively small average particle diameter are present in the vicinity of the center of the layer to be the organic photoelectric conversion layer 3 in terms of manufacturing. Therefore, the pn junction area that expresses the charge separation function is expanded, and as a result, a charge separation promoting region that acts to promote charge separation can be formed. On the other hand, in the vicinity of the interface between the layer to be the organic photoelectric conversion layer 3 and the electrodes 1 and 2, the average particle diameter of the organic semiconductor of one polarity is increased so that there are few grain boundaries that hinder the transport of charges and the resistance is low A charge transport path (charge transport region) is continuously formed. This makes it possible to form a desired hybrid function region that acts to improve charge transport and charge extraction efficiency. With these actions, the organic photoelectric conversion device 10 of the present embodiment can improve the photoelectric conversion efficiency more efficiently. In this case, for example, the domain size ratio of the p-type organic semiconductor and the n-type organic semiconductor is a layer that is changed in a direction approaching a ratio that is substantially uniform toward the central region of the organic photoelectric conversion layer 3. Moreover, even if one side (5p side in FIG. 2) of the organic photoelectric conversion layer 3 is made of a p-type organic semiconductor layer, the other side (5n side in FIG. 2) is made of an n-type organic semiconductor layer. Good.

  The p-type organic semiconductor particles and the n-type organic semiconductor particles may be in any form such as microcrystals and aggregates. In the present embodiment, the photoelectric conversion layer 3 has a single-layer structure, but may have a multilayer structure in which, for example, a p-type organic semiconductor layer, an n-type organic semiconductor layer, and a mixed layer thereof are stacked. Furthermore, the domain size gradient formed by the size of the particle diameter may be formed by continuously changing the average particle diameter, or may be formed by changing stepwise. That is, the charge separation promoting region may include a gradation region in which each domain size changes continuously, or may include a step region that changes stepwise. However, the single layer structure as in the present embodiment does not have a clear interface in the layer, and is advantageous in terms of charge transport compared to the multilayer structure.

  Here, with reference to FIG. 2, the organic photoelectric converting layer 3 which comprises the principal part of the photoelectric conversion device 10 of this embodiment is demonstrated in detail. FIG. 2 is a conceptual diagram showing a configuration of the organic photoelectric conversion device according to Embodiment 1 of the present invention.

As shown in FIG. 2, the organic photoelectric conversion device 10 of the present embodiment includes the charge separation promoting region 4 in which the domain size gradient A is formed in the organic photoelectric conversion layer 3 described above. For example, by heat treatment or the like of the driving body layer before the predetermined domain size gradient is formed in the p-type organic semiconductor and the n-type organic semiconductor to be formed, p-type organic semiconductor and n as the charge-separation enhancing region 4 A domain size gradient A with the type organic semiconductor is formed. The charge separation promotion region 4, by increasing the area of the pn junction interface between the p-type organic semiconductor and the n-type organic semiconductor (hetero junction interface into the bulk), to facilitate the action of the charge separated by their pn junction interface It becomes an area.

  Specifically, in such a bulk heterojunction region, the pn junction surface between the p-type organic semiconductor (acceptor) and the n-type organic semiconductor (donor) is dispersed in the bulk of the mixed layer (bulk heterojunction layer). It exists uniformly. Such an increase in the pn junction area is a region where photo-induced charge separation occurs efficiently.

Such a charge separation promoting region 4 is preferably a region containing a substantially equal portion of the pn junction ratio between the p-type organic semiconductor and the n-type organic semiconductor in terms of improving charge separation and charge transport efficiency. Further, it may be a region having a domain size gradient across its region near the pn junction proportion from approximately equal parts may be regions pn junction rate was present substantially evenly close ratio. In particular, in the charge separation promoting region 4, a layer structure in which a domain size gradient is appropriately formed from a portion where the pn junction ratio is substantially uniform and is continuously transferred to the p-type or n-type organic semiconductor rich regions 5 p and 5 n. It is preferable that As a result, it is possible to further increase the efficiency of transfer to charge transport while promoting the charge separation action.

  Note that the optimum pn junction ratio in the charge separation promoting region 4 can be appropriately adjusted in consideration of the balance between charge separation and charge transport efficiency in order to increase the efficiency of photoelectric conversion.

  Here, the domain size gradient A according to the organic photoelectric conversion layer 3 of the present embodiment is formed by phase separation at least in the charge separation promoting region 4, and is adjacent to the p-type organic semiconductor and the n-type organic semiconductor. Is the relative slope of each domain size. Further, the domain size gradient A is such that, in the thickness direction of the organic photoelectric conversion layer 3, the p domain of the p-type organic semiconductor and the n domain of the n-type organic semiconductor are in a volumetric relationship (the size of the particle or the like). Have a large and small relationship). For example, it can be formed based on the difference in the pn domain existence ratio due to the size relationship of the pn domain size. Thus, by forming the domain size gradient A in at least the charge separation promoting region 4, the charge separation promoting region 4 becomes a region where charge separation and charge transport are efficiently performed.

  In the present embodiment, by controlling the domain size gradient A, the entire arrangement of the p-type semiconductor region and the n-type semiconductor region in the organic photoelectric conversion layer 3 is not randomly (irregularly) formed. This is very advantageous in that it exhibits stable photoelectric conversion efficiency with less uncertainty.

  Furthermore, in the organic photoelectric conversion device 10 of the present embodiment, the region on the electrode 1 side of the organic photoelectric conversion layer 3 has a high abundance ratio of the n-type organic semiconductor, and approaches the electrode 2 side of the organic photoelectric conversion layer 3. As a result, the abundance ratio of the n-type organic semiconductor is continuously reduced. On the other hand, the abundance ratio of the n-type organic semiconductor is low on the electrode 1 side, and continuously increases as it approaches the electrode 2 side of the organic photoelectric conversion layer 3. That is, in this embodiment, since the photoelectric conversion layer 3 is a single layer and the layer size gradient A continuously changes, the layer does not have a clear interface and is advantageous in terms of charge transport.

  Further, in the vicinity of the interface between the organic photoelectric conversion layer 3 and the electrodes 1 and 2, the organic semiconductor rich regions 5 p and 5 n of one polarity are formed, and the grain boundary that impedes charge transport and the organic semiconductor region opposite in polarity to the moving charge are substantially present. It is trying to be less. Since the above-described charge separation promoting region 4 is provided between each of the organic semiconductor rich regions 5p and 5n, a high-quality charge transport path with less resistance and charge recombination is formed, and charge transport and charge extraction are performed. Efficiency is improved.

  For example, a region (n-type organic semiconductor rich region 5n) in which the abundance ratio of the n-type organic semiconductor and the p-type organic semiconductor is 1: 0 is provided in a region adjacent to the electrode 1. Further, a region (p-type organic semiconductor rich region 5p) in which the abundance ratio of the n-type organic semiconductor and the p-type organic semiconductor is 0: 1 is provided in a region adjacent to the electrode 2. By these, the said effect | action can be expressed efficiently. And according to the organic photoelectric conversion device 10 of this embodiment provided with such an electric charge separation promotion area | region 4, the improvement of a photoelectric conversion efficiency can be aimed at more efficiently.

  Here, as described above, the charge separation promoting region 4 according to the present embodiment is provided so as to be positioned between the p-type organic semiconductor rich region 5p and the n-type organic semiconductor rich region 5n. The p-type organic semiconductor rich region 5p is, for example, a region (p> n) in which the pn junction ratio is smaller than that of the charge separation promotion region 4 and the p domain is present in volume more than the n domain. The p-type organic semiconductor rich region 5p is preferably a region where more p-type organic semiconductor exists than the n-type organic semiconductor in the charge separation promoting region 4. Thereby, it becomes a region where charge separation and charge transport are performed efficiently. The p-type organic semiconductor rich region 5p includes a region (or p-type organic semiconductor layer) containing only the p-type organic semiconductor on one electrode side. Further, the n-type organic semiconductor rich region 5n means a region (n> p) in which the n domain is present in a larger volume than the p domain. The n-type organic semiconductor rich region 5n is preferably a region where more n-type organic semiconductor exists than the p-type organic semiconductor in the charge separation promoting region. Thereby, it becomes a region where charge separation and charge transport are performed efficiently. The n-type organic semiconductor rich region 5n includes a region (or an n-type organic semiconductor layer) containing only the n-type organic semiconductor on the other electrode side.

Further, in the organic photoelectric conversion device 10 of the present embodiment, the charge separation promoting region 4 and the p-type organic semiconductor rich region 5p or the n-type organic semiconductor rich region 5n substantially overlap as the charge transport region 6. Yes. Specifically, the charge separation promoting region 4 has a domain size gradient A continuously formed from the charge separation promoting region 4 to the p-type organic semiconductor rich region 5p or the n-type organic semiconductor rich region 5n. That is, the boundary of the charge separation promoting region 4 on the p-type organic semiconductor rich region side (region 5p side) or the n-type organic semiconductor rich region side (region 5n side) and the vicinity thereof also serve as the charge transport region 6. A clear interface between the separation promoting region 4 and the charge transport region 6 is eliminated. Efficiency This charge separation promoting region 4, i.e., while causing the energy gap in the hetero junction interface area to the bulk of the p domain and n domain, the transport of charge to the area 5p or regions 5n by domain size gradient A Can be done well. That is, according to the organic photoelectric conversion device 10 of the present embodiment, charge transfer from the charge separation functional region to the charge transport functional region can be efficiently performed, and the photoelectric conversion efficiency in the organic photoelectric conversion layer 3 can be improved. .

  Here, the p-type organic semiconductor used in the organic photoelectric conversion device 10 according to this embodiment described above is a donor organic semiconductor, and is typically represented by a hole transporting organic compound and has a property of easily donating electrons. An organic compound. More specifically, the organic compound (electron-donating organic material) having the smaller ionization potential when two organic materials are used in contact with each other. Therefore, any organic compound can be used as the donor organic compound as long as it is an electron-donating organic compound.

  Examples of p-type organic semiconductors include oligomers and polymers having thiophene and its derivatives in the skeleton, oligomers and polymers having phenylene-vinylene and its derivatives in the skeleton, oligomers and polymers having thienylene-vinylene and its derivatives in the skeleton, and carbazole. And oligomers and polymers having skeletons of vinyl carbazole and derivatives thereof, oligomers and polymers having skeletons of pyrrole and derivatives thereof, oligomers and polymers having skeletons of acetylene and derivatives thereof, phthalocyanines, Examples thereof include metal phthalocyanines and derivatives thereof, acenes such as pentacene and derivatives thereof, porphyrin and derivatives thereof, and polythiophene derivatives are particularly preferably used.

  The polythiophene derivative has a structure in which a side chain is attached to a polymer having a poly-p-thiophene skeleton. Specific examples include poly-3-alkylthiophenes such as poly-3-methylthiophene, poly-3-butylthiophene, poly-3-hexylthiophene, poly-3-octylthiophene, and poly-3-decylthiophene. This is not the case.

  On the other hand, the n-type organic semiconductor used in the organic photoelectric conversion device 10 according to this embodiment described above is an acceptor organic semiconductor, and is mainly represented by an electron transporting organic compound, and has an organic property that easily accepts electrons. Say. More specifically, it refers to an organic compound (electron-accepting organic material) having a higher electron affinity when two organic compounds are used in contact with each other. Therefore, as the acceptor organic compound, any organic compound can be used as long as it is an electron-accepting organic compound.

  Examples of the n-type organic semiconductor include fullerene and derivatives thereof (PCBM, etc.), carbon nanotubes and derivatives thereof, perylene and derivatives thereof (PTCDA, PTCDI, etc.), naphthalene derivatives (NTCDA, NTCDI, etc.), pyridine and derivatives thereof. Oligomers and polymers, fluorinated metal-free phthalocyanines, fluorinated metal phthalocyanines and their derivatives, tris (8-hydroxyquinolinato) aluminum complexes, bis (4-methyl-8-quinolinato) aluminum complexes, distyrylarylene derivatives And silole compounds. In particular, fullerene derivatives (PCBM and the like) are preferably used. However, this is not the case.

  In addition, the material mentioned above is an illustration, The precursor of the applicable material may be used for the p-type organic semiconductor and the n-type organic semiconductor, and the precursor may be converted into the relevant material by post-processing after film formation. good.

  Here, the material for forming the pair of electrodes 1 and 2 is not particularly limited, but the type of the constituent material of the adjacent or adjacent layer (the organic photoelectric conversion layer 3 in this embodiment), the direction in which light is irradiated, It is preferable to select appropriately according to the combination of work functions.

For example, when the material forming the electrode 1 is a material having a low work function, the material forming the electrode 2 is preferably a material having a high work function. Examples of the material having a low work function include In, Al, Ca, and Mg. Examples of the material having a high work function include Au, Ag, Co, Ni, Pt, ITO, SnO ₂ , fluorine-doped SnO ₂ , and ZnO.

  Here, the electrode 1 or 2 on the light irradiation side, that is, the incident light side is preferably formed of an optimal material in order to improve the photoelectric conversion efficiency. In particular, the organic photoelectric conversion layer 3 is preferably made of a material that transmits incident light that reacts in charge generation, and the electrode on the incident light side is preferably formed.

  In addition, the electrode on the incident light side has a wavelength other than the wavelength of incident light in which the organic layer portion of the photoelectric conversion layer 3 directly reacts in charge generation (the organic layer portion is inherently capable of photoelectric conversion). You may form with the material which is easy to permeate | transmit light. When light is irradiated perpendicularly to the electrode plane, the electrode on the light irradiation side is formed of a transparent material.

Examples of such transparent materials include In—Sn—O (ITO: Indium Tin Oxide), In—Zn—O (IZO), zinc oxide (ZnO), tin oxide (SnO ₂ ), and fluorine-doped oxide. Examples thereof include transparent conductive polymers such as tin and PEDOT: PSS.

  Hereinafter, an example of the manufacturing method of the organic photoelectric conversion device 10 of this embodiment is demonstrated. First, the organic photoelectric conversion layer 3 is formed on the electrode 2. Here, before the organic photoelectric conversion layer 3 is formed, the surface of the organic photoelectric conversion layer 3 (the surface of the electrode 2 in this embodiment) is subjected to oxygen plasma treatment for the purpose of cleaning the surface or improving the energy state. Surface treatment such as UV ozone treatment may be performed.

  The electrode 2 may be formed on a substrate, and the substrate may be transparent or opaque. For example, when the substrate side is a light receiving surface, a transparent substrate is preferable. As a material for the transparent substrate, for example, an inflexible transparent rigid material such as quartz glass, Pyrex (registered trademark), a synthetic quartz plate, a transparent resin film such as an aramid resin, an optical resin plate, etc. The transparent flexible material which has flexibility can be mentioned.

  For example, if the substrate is a flexible material such as a transparent resin film, it is useful for realizing a reduction in manufacturing cost, weight reduction, and an organic thin film solar cell that is difficult to break, and applicability to various applications such as application to curved surfaces. Is preferable in terms of spreading.

  The organic photoelectric conversion layer 3 is formed so that the domain size has a gradient in the layer thickness direction. That is, the organic photoelectric conversion layer 3 having the charge separation promoting region 4 is optimal by depositing the material (p-type organic semiconductor and n-type organic semiconductor) forming the organic photoelectric conversion layer 3 while changing the mixing ratio. It can be formed to have a domain size gradient A.

  Furthermore, it is desirable that the method for forming the organic photoelectric conversion layer 3 is appropriately selected depending on the constituent materials. For example, as a film forming method from a solution, a spin coating method, a casting method, a gravure coating method, a dip coating method, a spray coating method, a shower coating method, a curtain coating method, an electrodeposition coating method, an electrostatic coating method (ESD method) Various film forming methods such as a die coating method, a screen printing method, an ink jet printing method, and an electrolytic polymerization method can be used. Alternatively, an evaporation method, a sputtering method, a plasma CVD method, or the like may be used. Among them, electrical film formation methods (electrodeposition coating, electrostatic coating, etc.) can make effective use of the electrode 2 and the like, have excellent material selectivity such as organic materials, and introduce electric field forming substances. It is easy and can cope with large area. Therefore, the electrical film formation method is very advantageous in that a photoelectric conversion device such as an organic thin film solar cell with improved photoelectric conversion efficiency can be manufactured at low cost.

  Here, the object of the present invention is to improve the efficiency of charge separation and charge transport to improve the photoelectric conversion efficiency. However, the present invention is not limited to this, and the problem of increasing the area of the photoelectric conversion device (object) The present invention may be applied as a means for solving the problem. In this case, an organic photoelectric conversion device such as a solar cell (especially a single-layer or multilayer organic photoelectric conversion layer) is formed using the above-described film forming method, which greatly increases the area of the organic photoelectric conversion device. It will be advantageous.

  In the present invention, in particular, an electrostatic coating method (ESD method) can be preferably used. In the electrostatic coating method, for example, the time for injecting (applying) a p-type organic semiconductor and an n-type organic semiconductor that are constituent materials of the organic photoelectric conversion layer, the distance between the injection nozzle and the application surface (substrate), the injection nozzle, Parameters such as the strength (ON / OFF) of voltage applied to the coating surface, application time, pn material concentration ratio (mixing ratio), solvent type, and solvent amount are controlled. By these controls, the domain size and the pn junction ratio can be appropriately changed. Therefore, when the electrostatic coating method is used, it is easy to form the organic photoelectric conversion layer of the present invention.

  In addition, in the manufacturing method of the organic photoelectric conversion device of this invention, it is the feature point to form the gradient of a domain size directly by each control mentioned above. In this respect, it is different from the conventional technique in which the content of the electron donating material or the like (content of the material having a substantially uniform domain size) is merely given a gradient.

Here, in this invention, an organic photoelectric conversion device can be manufactured with the method etc. which were mentioned above. For example, a step of forming a precursor layer having a relative gradient in each domain by directly controlling the size and mixing ratio of each material of the p-type organic semiconductor and the n-type organic semiconductor by the above-described method ( Layer formation process). That is, at this point, the Precursor layer, underlying as a predetermined domain size gradient is substantially formed. In order to form an organic photoelectric conversion layer having a charge separation region, a charge transport region, and an overlap region of these regions, for example, heat treatment is performed. Charge separation region and a p-type organic semiconductor and the n-type organic semiconductor adjacent the engaged terror against bulk Thus is formed, as a region which overlaps with the charge separating region, adjacent p-type organic semiconductor or n-type organic The semiconductors are integrated (grained) to form a charge transport region. Therefore, a high-quality charge transport path (charge transport region) with less resistance and charge recombination is formed as a continuous region from the charge separation region, and as a result, an organic that can improve charge transport and charge extraction efficiency. A photoelectric conversion layer is formed.

  The organic photoelectric conversion layer 3 may be subjected to post-treatment such as heat treatment for the purpose of solvent drying or annealing, conversion of the precursor film of the material after the formation.

  Subsequently, the electrode 1 is formed on the organic photoelectric conversion layer 3 thus formed. As a method for forming the electrode 1, a known method such as a vacuum deposition method, a sputtering method, or various coating methods can be appropriately used. Thereby, the photoelectric conversion device 10 of this embodiment can be formed.

  Here, the case where the electrodes 2 are sequentially stacked has been described, but the electrodes 1 may be sequentially stacked.

  The organic solution to be electrostatically applied uses n-type and p-type organic semiconductor materials. By applying a voltage to the syringe filled with each organic semiconductor material, n-type and p-type bulk heterojunction structures are formed. For example, by controlling the voltage applied to one syringe here, the droplet size and ejection speed of the organic semiconductor material to be ejected change. Therefore, the domain size gradient A can be formed by continuously changing the applied voltage.

(Embodiment 2)
FIG. 3 is a schematic cross-sectional view of a photoelectric conversion element which is an example of an organic photoelectric conversion device according to Embodiment 2 of the present invention.

  As shown in FIG. 3, the organic photoelectric conversion device (organic photoelectric conversion element) 20 of this embodiment is the same as that of Embodiment 1 described above except that the organic photoelectric conversion layer 3 includes a charge separation promoting layer 4. In the present embodiment, the same components as those in the first embodiment (FIGS. 1 and 2) described above are denoted by the same reference numerals, and the description thereof is omitted.

  Specifically, the organic photoelectric conversion layer 3 according to the present embodiment includes a p-type organic semiconductor and an n-type organic semiconductor in the thickness direction, that is, from one electrode 1 side to the other electrode 2 side. A domain size gradient A is continuously formed. The organic photoelectric conversion layer 3 is continuous with a predetermined domain size gradient A across the p-type organic semiconductor rich region 5p on one electrode 1 side and the n-type organic semiconductor rich region 5n on the other electrode 2 side. Is formed. That is, the organic photoelectric conversion layer 3 is composed of the charge separation promoting layer 4. The domain size gradient A of the present embodiment may be the same as that of the first embodiment described above, or may be set with an appropriate difference in domain size between the n-type organic semiconductor and the p-type organic semiconductor. May be.

  Even in such a configuration, by performing charge separation at the pn junction interface and forming the domain size gradient A, it is possible to efficiently shift to charge transport. Therefore, the efficiency of charge separation and charge transport is ensured, and the photoelectric conversion efficiency can be improved in the organic photoelectric conversion device 20 as in Embodiment 1 described above.

(Embodiment 3)
FIG. 4 is a schematic cross-sectional view of a photoelectric conversion element that is an example of an organic photoelectric conversion device according to Embodiment 3 of the present invention.

  As shown in FIG. 4, the organic photoelectric conversion device (organic photoelectric conversion element) 40 of the present embodiment has a charge separation promoting region in which the organic photoelectric conversion layer 3 has a multilayer structure and has a step structure in which the domain size gradient is discontinuous. 4A and 4B (step regions) are provided. A buffer layer 7 is provided between the organic photoelectric conversion layer 3 and the pair of electrodes 1 and 2. Other than these, the second embodiment is the same as the first embodiment. In the present embodiment, the same components as those in the first embodiment (FIGS. 1 and 2) described above are denoted by the same reference numerals, and the description thereof is omitted.

  Specifically, the domain size gradient according to the present embodiment is formed stepwise by stacking two layers 4A and 4B having different pn junction ratios. The layer 4A on the electrode 1 side of the organic photoelectric conversion layer 3 has a high abundance ratio of the n-type organic semiconductor, and the n-type organic semiconductor gradually increases as it becomes the lower layer 4B of the layer (becomes a layer on the electrode 2 side). The abundance ratio of is low. On the other hand, the abundance ratio of the n-type organic semiconductor changes in the opposite direction to the change of the p-type organic semiconductor. In this case, there are a region where the domain size of the p-type organic semiconductor changes relatively as it moves away from the positive electrode, and a region where the domain size of the n-type organic semiconductor changes as it moves away from the negative electrode. It will be formed. Thereby, the improvement of photoelectric conversion efficiency can be aimed at similarly to Embodiment 1 mentioned above.

  Hereinafter, an example of the manufacturing method of the photoelectric conversion device 40 of this embodiment is demonstrated. First, the organic photoelectric conversion layer 3 is formed on the electrode 2. In the organic photoelectric conversion layer 3 here, a plurality of layers 4A and 4B having different domain size gradients are stacked therein.

  That is, a material for forming the organic photoelectric conversion layer 3 (either a p-type semiconductor, an n-type semiconductor, or a mixed material thereof) is formed on the electrode 2 to form the first layer. Next, a material having a domain size gradient different from that of the first layer is formed on the first layer (in this embodiment, the p-type organic semiconductor concentration is lower than the first layer and the n-type organic semiconductor concentration is higher). Then, the second layer is formed. By repeating this, the organic photoelectric conversion layer 3 including a plurality of layers having a multi-step (step) type domain size gradient is formed.

  Here, similarly to the manufacturing method of Embodiment 1 described above, the organic photoelectric conversion layer 3 may be subjected to post-treatment such as heat treatment. In this embodiment, even if post-treatment is performed after all the layers are stacked, 1 A post-treatment may be performed after laminating several layers. In the present embodiment, different post-treatments can be easily performed on each layer as necessary.

  In addition, as a method for forming the organic photoelectric conversion layer 3, the same method as that of the first embodiment can be selected, and the charge separation promoting region 4 in which the pn domain size gradient included in the organic photoelectric conversion layer 3 is formed is configured. It is possible to appropriately select an optimum film formation method for each of the layers 4A and 4B.

  In addition, you may mix a dopant, an additive, etc. selectively in each layer 4A, 4B which comprises the electric charge separation promotion area | region 4 contained in the organic photoelectric converting layer 3. FIG.

  Subsequently, the electrode 1 is formed on the organic photoelectric conversion layer 3. As a method for forming the electrode 1, the same method as that of the first embodiment described above can be used. Thereby, the organic photoelectric conversion device 40 of this embodiment can be formed. Here, the case where the electrodes 2 are sequentially stacked has been described, but the electrodes 1 may be sequentially stacked.

  In the present embodiment, the case where the charge separation promoting region 4 is configured by two layers (4A, 4B) has been described. However, the present invention is not limited to this, and a multilayer structure of three layers or more may be used. In this case, it is preferable to form a gradient so that the p-type organic semiconductor or the n-type organic semiconductor becomes richer as it approaches the electrode side. At this time, an appropriate difference may be made in the gradient in each layer.

(Embodiment 4)
FIG. 5 is a schematic cross-sectional view of a photoelectric conversion element that is an example of a solar cell (organic thin-film solar cell) according to Embodiment 4 of the present invention.

  As shown in FIG. 5, the organic thin-film solar cell 100 of this embodiment is provided with an ITO electrode 12 on a substrate 11 and a first buffer layer 13, an organic photoelectric conversion layer 14, and a second buffer layer 15 stacked thereon. Further, the Al electrode 16 is formed on the second buffer layer 15. In addition, the organic photoelectric conversion layer 14 can apply the organic photoelectric conversion layer in any one of Embodiment 1-4 mentioned above, and description of an organic photoelectric conversion layer is abbreviate | omitted.

  In addition, the substrate 11 is preferably selected as appropriate depending on the type of constituent material of adjacent or adjacent layers and the direction of light irradiation. Specifically, when light is irradiated from the substrate side, the substrate is formed of a transparent material.

  Examples of the material for forming such a substrate 11 include glass, quartz, polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), acrylic resin, polycarbonate, polyimide resin, norbornene resin, polystyrene, polyvinyl chloride, polyarylate. , Transparent resins such as polysulfone, polyethersulfone, and polyetherimide. However, it is not limited to these. When a flexible substrate such as the transparent resin is used, a flexible photoelectric conversion device can be manufactured by appropriately selecting a material and a film thickness such as an organic material layer stacked on the substrate.

  According to the organic thin-film solar cell 100 of the present embodiment, since the organic photoelectric conversion layer 14 improves the efficiency of charge separation and charge transport as described in the first embodiment and the like, from the substrate 11 side. The photoelectric conversion efficiency can be improved when responding to the incident light.

  In addition, as a manufacturing method of such a solar cell, first, the substrate 11 on which the ITO electrode 12 was formed was prepared, and the surface of the substrate 11 including the ITO electrode 12 was cleaned (ultrasonic cleaning, UV ozone cleaning, etc.). Thereafter, a plurality of organic films are stacked on the substrate 11. Here, as a film forming process of the organic film, for example, a buffer material such as PEDOT: PSS material is formed by spin coating, and then the first buffer layer 13 is formed by heat treatment. Next, an organic photoelectric conversion layer 14 having at least a charge separation promoting region is formed on the first buffer layer 13 by electrostatically applying an organic material such as P3HT: PCBM and performing a heat treatment. Thereafter, a buffer material such as LiF is formed on the organic photoelectric conversion layer 14 to form a second buffer layer 15 (the second buffer layer 15 also functions as an electrode adhesion layer and a part of the electrode). A solar cell (cell) is manufactured by forming the Al electrode 16 thereon.

(Other embodiments)
As mentioned above, although this invention was demonstrated in detail based on Embodiment 1-4, this invention is not limited to each Embodiment 1-4 mentioned above. For example, in each of the first to third embodiments described above, the element configuration is illustrated and described as an example of the photoelectric conversion device, but the present invention is not limited to this. For example, various photoelectric conversion devices using photoelectric conversion function, optical rectification function, etc., for example, photovoltaic cells (solar cells (photovoltaic power generation device), etc.), photovoltaic elements, electronic elements (photosensors, optical switches, phototransistors, etc.) Application to optical recording materials (optical memory, etc.) is possible. In particular, it is useful for solar cells (organic thin-film solar cells, organic-inorganic thin-film solar cells, silicon-based solar cells, etc.) and photovoltaic elements. Moreover, there is no problem even if the unit layer structure is laminated (tandem) according to the application.

  In the first embodiment described above, the charge separation promoting region layer 4 and other organic semiconductor rich regions (5p, 5n) are provided in the organic photoelectric conversion layer 3, and the domain size gradient A is provided in the overlap region 6. . In addition, as a specific example thereof, the first embodiment has described that the domain size gradient is formed by the size of the particle diameter as an example of the domain size gradient. However, the present invention is not limited thereto. For example, in the charge separation promoting region, a domain size gradient formed in the thickness direction of the organic photoelectric conversion layer by the linearized p-type organic semiconductor and n-type organic semiconductor is used. You may make it have.

1, 2 Electrode 3 Organic photoelectric conversion layer 4 Charge separation promoting region 10 Organic photoelectric conversion device 100 Organic thin film solar cell A Domain size gradient

Claims (9)

an organic photoelectric conversion layer including a p-type organic semiconductor and an n-type organic semiconductor;
The organic photoelectric conversion layer includes a charge transport region for transporting a charge from one electrode to the other electrode, a region where the p-type organic semiconductor and the n-type organic semiconductor are joined, and the p-type organic semiconductor A domain size gradient is formed in which a pn junction area between the domain of the n-type organic semiconductor and the domain of the n-type organic semiconductor expands toward a central region in the thickness direction of the organic photoelectric conversion layer, and separation of charges transported to the charge transport region A charge separation promoting region that promotes
The charge separation promoting region includes a p-type organic semiconductor rich region in which the p-type organic semiconductor is present in a larger amount than the n-type organic semiconductor in the charge separation promoting region, and the n-type organic semiconductor is in the charge separation promoting region. The n-type organic semiconductor rich region exists in a larger amount than the p-type organic semiconductor,
The boundary of the charge separation promoting region on the p-type organic semiconductor rich region side or the n-type organic semiconductor rich region side and the vicinity thereof also serve as the charge transport region, and the domain size gradient is determined by the p-type organic semiconductor. Formed from the charge transport region which is a rich region or the n-type organic semiconductor rich region to the charge separation promoting region ,
The domain size of the p-type organic semiconductor is reduced from the one electrode toward the other electrode, and the domain size of the n-type organic semiconductor is directed from the other electrode toward the one electrode. decreases Te so formed on the organic photoelectric conversion device according to claim Rukoto.   The charge separation promoting region has a domain size gradient formed in a thickness direction of the organic photoelectric conversion layer depending on a particle size of the p-type organic semiconductor and the n-type organic semiconductor. 1. The organic photoelectric conversion device according to 1.   3. The organic photoelectric conversion device according to claim 1, wherein the charge separation promoting region is a layer in which a bulk heterojunction region between the p-type organic semiconductor and the n-type organic semiconductor is formed in a layer shape.   The charge separation promoting region includes a gradation region in which each domain size of the p-type organic semiconductor and the n-type organic semiconductor continuously changes. Organic photoelectric conversion device.   The charge separation promoting region includes a step region in which each domain size of the p-type organic semiconductor and the n-type organic semiconductor changes stepwise. Organic photoelectric conversion device.   The organic photoelectric conversion layer has a layer in which each domain size ratio of the p-type organic semiconductor and the n-type organic semiconductor is changed in a direction approaching a ratio that is substantially uniform toward a layer center region of the photoelectric conversion layer. The organic photoelectric conversion device according to any one of claims 1 to 5, wherein: One surface of the organic photoelectric conversion layer comprises a layer of the p-type organic semiconductor, the other surface side according to any one of claim 1 to 6, characterized in that a layer of the n-type organic semiconductor Organic photoelectric conversion device. An organic thin-film solar cell comprising the organic photoelectric conversion device according to any one of claims 1 to 7 . forming a precursor layer having a gradient of a domain of a p-type organic semiconductor and a domain of an n-type organic semiconductor; and heating the precursor layer to bond the p-type organic semiconductor and the n-type organic semiconductor Forming a domain size gradient in which a pn junction area between the domain of the p-type organic semiconductor and the domain of the n-type organic semiconductor expands toward a central region in the thickness direction of the organic photoelectric conversion layer. An organic photoelectric conversion layer,
The organic photoelectric conversion layer has a charge transport region for transporting charges from one electrode to the other electrode,
A charge separation promoting region for separating charges transported to the charge transport region,
The charge separation promoting region includes a p-type organic semiconductor rich region in which the p-type organic semiconductor is present in a larger amount than the n-type organic semiconductor in the charge separation promoting region, and the n-type organic semiconductor is in the charge separation promoting region. The n-type organic semiconductor rich region exists in a larger amount than the p-type organic semiconductor,
The boundary of the charge separation promoting region on the p-type organic semiconductor rich region side or the n-type organic semiconductor rich region side and the vicinity thereof also serve as the charge transport region, and the domain size gradient is determined by the p-type organic semiconductor. Formed from the charge transport region which is a rich region or the n-type organic semiconductor rich region to the charge separation promoting region ,
The domain size of the p-type organic semiconductor is reduced from the one electrode toward the other electrode, and the domain size of the n-type organic semiconductor is directed from the other electrode toward the one electrode. It becomes smaller so formed method for producing an organic photoelectric conversion device according to claim Rukoto Te.

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