JP2013179158A - Method for producing photoelectric conversion device, photoelectric conversion device and production device of photoelectric conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an organic photoelectric conversion device by a new method for orienting an orientational organic material which an active layer has, etc.SOLUTION: A method for producing a photoelectric conversion device having an orientation layer which has a first orientation organic material, and an active layer which converts incident light into electricity, includes: an orientation layer formation step of forming an orientation layer by using the first orientational organic material; a first rubbing step of rubbing the orientation layer in a first direction in the surface in parallel with the orientation layer; a second rubbing step of rubbing the orientation layer in a second direction different from the first direction in the surface in parallel with the orientation layer; and an active layer formation step of forming the active layer by using a second orientational organic material.

Description

  The present invention relates to a method for producing a photoelectric conversion device, a photoelectric conversion device, and a production apparatus for a photoelectric conversion device, and in particular, a photoelectric conversion having an alignment layer having a first alignment organic substance and an active layer for converting incident light into electricity. The present invention relates to a method for producing a device. In the present application, “orientation” refers to the arrangement of a plurality of molecules with a transition dipole moment in a specific direction.

  Patent Document 1 describes an organic solar cell having an organic thin film in which a conductive polymer is oriented by a rubbing (friction) method which is a simple method.

JP 2008-078129 A

  Patent Document 1 describes the effectiveness of orientation by rubbing regarding an organic solar cell. However, in order to broaden the options for the production method of the organic photoelectric conversion device, more detailed research and development is expected, for example, by clarifying the relationship between a specific alignment method and energy conversion efficiency.

  Therefore, an object of this invention is to provide the method of producing an organic photoelectric conversion apparatus by the new method of orienting the orientational organic substance which an active layer has.

  A first aspect of the present invention is a method for producing a photoelectric conversion device having an alignment layer having a first alignment organic substance and an active layer for converting incident light into electricity, using the first alignment organic substance. An alignment layer forming step for forming the alignment layer; a first friction step for rubbing the alignment layer in a first direction in a plane parallel to the alignment layer; and the first in a plane parallel to the alignment layer. A method for producing a photoelectric conversion device, comprising: a second friction step of rubbing the alignment layer in a second direction different from the direction; and an active layer formation step of forming the active layer using a second alignment organic material. is there.

  A second aspect of the present invention is a method for producing the photoelectric conversion device according to the first aspect, wherein the alignment layer includes n directions different from each other including the first direction and the second direction. (N is a natural number of 2 or more), and the smaller one of the angles formed by the first direction and the second direction is 180 / n [°].

  A third aspect of the present invention is a method for producing the photoelectric conversion device according to the first or second aspect, in the first friction step and / or the second friction step, under an inert gas atmosphere. Then, the alignment layer is rubbed with a dust-free cloth.

  A fourth aspect of the present invention is a method for producing a photoelectric conversion device having an alignment layer having a first alignment organic substance and an active layer for converting incident light into electricity, using the first alignment organic substance. An alignment layer forming step for forming the alignment layer, a friction step for rubbing the alignment layer in an inert gas atmosphere, and an active layer forming step for forming the active layer using a second alignment organic substance. This is a method for producing a photoelectric conversion device.

  According to a fifth aspect of the present invention, there is provided a photoelectric conversion device having an active layer for converting incident light into electricity, wherein the active layer includes a first direction in a plane parallel to the active layer and the first direction. Is a photoelectric conversion device comprising organic substances oriented in different second directions.

  A sixth aspect of the present invention is the photoelectric conversion device according to the fifth aspect, in which the alignment organic material includes n different directions (n is different from the first direction and the second direction). 2 or more), and the smaller one of the angles formed by the first direction and the second direction is 180 / n [°].

  A seventh aspect of the present invention is a photoelectric conversion device having an active layer for converting incident light into electricity, wherein the active layer includes an oriented organic material, and an absorption peak wavelength of the oriented organic material is determined. The absorbance of the active layer with respect to polarized monochromatic light incident on the active layer from a direction perpendicular to the active layer, or short-circuit current density when the polarized monochromatic light is incident, internal quantum efficiency, external quantum Efficiency, internal energy conversion efficiency, or external energy conversion efficiency is first with respect to a rotation angle (0 ° to less than 360 °) when the active layer is rotated in a plane perpendicular to the light traveling direction. A photoelectric conversion device having three or more maximum values including a direction and a second direction different from the first direction.

  An eighth aspect of the present invention is a photoelectric conversion device having an active layer for converting incident light into electricity, wherein the active layer includes an alignment organic substance, and the active layer is in the first direction. A photoelectric conversion device having a morphology extending in a streak shape and a morphology extending in a second direction different from the first direction.

  According to a ninth aspect of the present invention, there is provided the photoelectric conversion device according to any one of the fifth to eighth aspects, wherein the photoelectric conversion device has a first alignment organic material aligned in the first direction and the second direction. An alignment layer is further provided, and the alignment layer is adjacent to the active layer.

  According to a tenth aspect of the present invention, there is provided a production apparatus for a photoelectric conversion device that converts incident light into electricity, wherein the alignment organic layer of the photoelectric conversion device is arranged in a direction parallel to the alignment organic layer. An apparatus for producing a photoelectric conversion device, comprising: friction means for rubbing; and rotation means for relatively rotating the oriented organic layer and / or the friction means.

  An eleventh aspect of the present invention is the photoelectric conversion device production apparatus according to the tenth aspect, wherein the friction means rubs the oriented organic layer under a dust-free cloth and an inert gas atmosphere. And an inert gas applying means for applying an inert gas for the purpose.

  Note that the first alignment organic material included in the alignment layer and the second alignment organic material included in the active layer may be the same substance.

  Moreover, the method of producing a photoelectric conversion apparatus should just rub at least in the two directions of a 1st and 2nd friction step. For example, one or more other rubbing processes may be included before the first friction step, between the first friction step and the second friction step, or after the second friction step.

  According to each aspect of the present invention, it is possible to align the second alignment organic substance in a plurality of directions (multiaxial directions) in the plane of the active layer. For this reason, it becomes possible to produce an organic photoelectric conversion device that efficiently absorbs light having electric field vector components in a plurality of directions, such as natural light, and thus improves energy conversion efficiency.

  Here, there is an impediment to intentionally orienting the oriented organic material in a plurality of directions. That is, conventionally, it is known that a certain degree of orientation can be obtained in the active layer plane when oriented only in a uniaxial direction. However, when oriented in a plurality of directions, the degree of orientation in the active layer surface may decrease, and the carrier mobility (hole mobility or electron mobility) may be reduced. Moreover, rubbing in a plurality of directions may reduce the light absorbance of the uniaxial electric field vector component that has been conventionally oriented. Therefore, there was a possibility that it may become disadvantageous from a viewpoint of energy conversion efficiency. Therefore, conventionally, the direction in which friction is performed is preferably aligned in a uniaxial direction.

  On the other hand, the inventors of the present invention have organic materials that are aligned in a plurality of directions without reducing the energy conversion efficiency as a whole, as compared with an organic photoelectric conversion device having organic materials that are aligned in a uniaxial direction. This is the first finding that an organic photoelectric conversion device can be produced. And it discovered that energy conversion efficiency and durability improved compared with the organic photoelectric conversion apparatus which does not orientate organic substance.

  As described above, an organic photoelectric conversion device having an organic material oriented in a plurality of directions is more advantageous than an organic photoelectric conversion device having an organic material oriented in a uniaxial direction in absorbing light polarized in a plurality of directions like natural light. is there. Therefore, it becomes possible to improve the energy conversion efficiency of the organic photoelectric conversion device having the oriented organic material in the active layer.

  In addition, by dispersing the direction in which the second alignment organic material is oriented, a photoelectric conversion device that efficiently absorbs light having electric field vector components in a plurality of directions such as natural light and improves energy conversion efficiency is produced. It becomes easy.

  Further, by rubbing the alignment layer in an inert gas atmosphere, it becomes possible to rub without exposing the interface between the alignment layer and the active layer to oxygen or water. For this reason, it becomes possible to produce a photoelectric conversion device with improved energy conversion efficiency.

  That is, the static electricity generated by the friction treatment becomes an obstacle to the experimental operation such as scattering the powder during weighing. In addition, in an inert gas atmosphere, the concentration of oxygen and water in the atmosphere is kept low, and it is difficult to eliminate static electricity. For this reason, conventionally, friction treatment in an inert gas atmosphere has been avoided.

  On the other hand, the inventors of the present invention have found knowledge that the energy conversion efficiency of the organic photoelectric conversion device is improved by paying attention to the friction treatment and performing the friction treatment in an inert gas atmosphere. is there.

It is a schematic diagram which shows the structure of the photoelectric conversion apparatus 1 which concerns on a present Example. It is a flowchart which shows an example of the production method of the photoelectric conversion apparatus 1 of FIG. It is the figure which showed the direction which rubs an orientation layer, and is the figure which showed the case where (a) it rubs only to a uniaxial direction, and (b) the case where it rubs in several directions. 1 is a diagram illustrating an example of a morphology of a photoelectric conversion device 1. FIG. 2 is a diagram illustrating an example of a photocurrent density-voltage characteristic of the photoelectric conversion device 1. FIG. It is a figure which shows the energy level figure of (a) 1st and 2nd ionization potential of the active layer 12, and (b) the calculated p / n interface. It is a figure which shows an example of the polarization angle dependence of the incident light of the photoelectric current density of the photoelectric conversion apparatus. It is a figure which shows an example of the polarization angle dependence of the light absorbency of the active layer formed into a film on the orientation layer. It is a figure which shows the light absorbency when changing the inclination with respect to the incident direction of a board | substrate, (a) When light enters perpendicular | vertical to a board | substrate, (b) It shows about the case where it tilts 80 degrees from the case of (a). FIG. FIG. 10 is a diagram in which the wavelength range of incident light in FIG. 9 is 600 to 900 nm corresponding to the absorption wavelength range of PTCBI. It is a figure which shows an example of the wavelength dependence of (a) light absorption rate of the photoelectric conversion apparatus 1, (b) external quantum efficiency, and (c) short circuit current density. It is a figure which shows an example of the spectral fluorescence spectrum of (a) active layer of the photoelectric conversion apparatus 1, and the fitting curve for calculating (b) exciton diffusion length. FIG. 3 is a diagram illustrating an example of a change with time of characteristics of the photoelectric conversion device 1. It is a figure which shows an example of the photocurrent density-voltage characteristic of the photoelectric conversion apparatus in different friction conditions.

  Embodiments of the present invention will be described below with reference to the drawings. The embodiment of the present invention is not limited to the following examples.

  FIG. 1 is a schematic diagram illustrating a structure of a photoelectric conversion device 1 according to the present embodiment (an example of “photoelectric conversion device” in the claims of the present application). The photoelectric conversion device 1 includes a substrate 3, an anode 5, an alignment layer 7 (an example of “alignment layer” in the claims of the present application), a p-type layer 9, an n-type layer 11, a buffer layer 13, and a cathode 15. With. The p-type layer 9 and the n-type layer 11 function as an active layer 12 (an example of an “active layer” in the claims) as a whole. As the substrate 3, a glass substrate was used. For the anode 5, an ITO layer of 150 nm was used. For the alignment layer 7, α-6T (α-sexithiophene) (an example of “first alignment organic material” in the claims of the present application), which is an alignment organic material, was aligned by a friction step described later. As the p-type layer 9, an α-6T layer of 50 nm (an example of “second alignment organic substance” in the claims of the present application) was used. The n-type layer 11 includes another PTCBI (perylene derivative; 3,4,9,10-perylenetetracarboxylic bis-benzimidazole) layer 30 nm (“second alignment organic substance” in the claims). Example) was used. As the buffer layer 13, a BCP (Bathocuproine) layer of 10 nm was used. As the cathode 15, an Ag (silver) electrode layer of 100 nm was used. Hereinafter, such a layered structure is expressed as glass / ITO (150 nm) / α-6T (rub) / α-6T (50 nm) / PTCBI (30 nm) / BCP (10 nm) / Ag (100 nm).

  When light is incident on the photoelectric conversion device 1 from the glass substrate 3 side, the light is absorbed by the active layer 12 to generate excitons. The excitons move by diffusion to the interface (p / n interface) between the p-type layer 9 and the n-type layer 11 and are separated into holes and electrons at the p / n interface. Holes are extracted from the anode 5 through the p-type layer 9, and electrons are extracted from the cathode 15 through the n-type layer 11 and the buffer layer 13 to become a current (photocurrent). The buffer layer 13 prevents excitons from reaching the cathode 15 and being quenched (de-excited).

  FIG. 2 is a flowchart showing an example of a production method of the photoelectric conversion device 1 of FIG. 1 (an example of “a method of producing a photoelectric conversion device” in the claims of the present application). In step ST001, a glass substrate 3 on which an ITO layer 5 (150 nm) is formed is prepared. In step ST002 (an example of “alignment layer forming step” in the claims of the present application), α-6T (15 nm) is formed as the alignment layer 7 by a vacuum deposition method. The vapor deposition rate here was 0.1 nm / s.

  Next, the friction step will be described with reference to FIG. In step ST003 (an example of “first friction step” in the claims of the present application), the first direction 18 in a plane parallel to the alignment layer 7 is used by using the friction means 17 (an example of “friction means” in the claims of the present application). The alignment layer 7 is rubbed in (an example of “first direction” in the claims). Subsequently, in step ST004 (an example of “second friction step” in the claims of the present application), a rotating means (not shown) (an example of “rotating means” in the claims of the present application) makes the photoelectric conversion device 1 and / or the friction means 17 relative to each other. The alignment layer 7 is rotated in a second direction 19 (an example of a “second direction” in the claims) different from the first direction 18 in a plane parallel to the alignment layer 7 using the friction means 17. Rubbing. By rubbing in this way, α-6T of the alignment layer 7 is aligned so that the molecular plane lies in a plane parallel to the alignment layer 7.

  The photoelectric conversion device 1 was produced without being exposed to air even once including the above friction step. As the friction means 17, a dust-free nylon cloth was used. Details of the direction of friction will be described later. Note that dust-free means that the dust is washed in a clean room and the amount of dust or other foreign matter attached is extremely small.

  Subsequently, in step ST005, an α-6T layer (50 nm) is formed as a p-type layer 9 following the oriented alignment layer 7. The deposition rate at this time was set to 0.01 nm / s, which is slower than step ST002, in order to improve the degree of orientation of the p-type layer 9. In step ST006, a PTCBI layer (30 nm) is formed as the n-type layer 11. The vapor deposition rate at this time was 0.01 nm / s. Steps ST005 and ST006 are an example of the “active layer forming step” in the claims of the present application as a whole. In Step ST007, a BCP layer (10 nm) is formed as the buffer layer 13. Finally, in Step ST008, an Ag layer (100 nm) is formed as the cathode layer 15, and the photoelectric conversion device 1 is produced. Further, the produced photoelectric conversion device 1 was sealed using a glass cap and an ultraviolet curable resin with a desiccant without exposing the element to be measured to the atmosphere from the production stage.

  Subsequently, the friction steps of steps ST003 and ST004 will be described in detail. FIGS. 3A and 3B are diagrams showing directions in which the alignment layer 7 is rubbed. FIGS. 3A and 3B show a case in which friction is caused only in a uniaxial direction and a case in which friction is caused in a plurality of directions (multiaxial directions). It is a figure. FIG. 3 shows the element on which the alignment layer 7 is formed as viewed from the alignment layer 7 side.

  With reference to FIG. 3A, a device (hereinafter referred to as “uniaxial device”) in the case of friction only in the uniaxial direction will be described. In the uniaxial device, after the alignment layer 7 was formed, the entire surface of the alignment layer 7 was rubbed only in the same direction in a plane parallel to the alignment layer 7. The number of times of friction was 16 in order to compare with the friction step of the photoelectric conversion device 1. Production processes other than the friction method were produced in the same manner as the production process of FIG. Note that streaks were observed on the surface of the alignment layer 7 after being rubbed with a dust-free nylon cloth corresponding to the rubbing direction.

  With reference to FIG.3 (b), the friction direction of the photoelectric conversion apparatus 1 rubbed in the several direction is demonstrated. Also in the photoelectric conversion device 1, after forming the alignment layer 7, friction was repeated 16 times in a plane parallel to the alignment layer 7. However, unlike the uniaxial device, the friction directions were all different. Specifically, the order indicated by the circled numbers in FIG. In the first round, friction was performed in the same direction as the uniaxial device. The second time rubbed in the direction orthogonal to the first time. From the third time on, friction was performed in different directions. In this way, the alignment layer 7 of the photoelectric conversion device 1 was rubbed evenly. Note that streaks were observed on the surface of the alignment layer 7 after being rubbed with a dust-free nylon cloth corresponding to the rubbing direction.

  With reference to FIG. 4, the morphology (surface morphology) of the element in which the active layer 9 is laminated on the rubbed alignment layer 7 will be described. FIG. 4 is a diagram illustrating an example of the morphology of the photoelectric conversion device 1, and is a diagram illustrating (a) a frictionless device, (b) a uniaxial device, and (c) a morphology of the photoelectric conversion device 1. Each element configuration was a frictionless device; quartz glass / α-6T (50 nm), uniaxial device and photoelectric conversion device 1; quartz glass / α-6T (rub) / α-6T (50 nm). The measurement apparatus was an atomic force microscope (VN-8000, manufactured by Keyence Corporation), and observed in DFM mode. In the graph showing the surface roughness in the figure, the horizontal axis represents the scale [μm], and the vertical axis represents the roughness [nm].

  Referring to FIG. 4 (a), no noteworthy morphology was observed in the non-friction device. On the other hand, with reference to FIG.4 (b), in the uniaxial device, the morphology which has the trace extended in the direction of one direction 21 was observed. 4C, in the photoelectric conversion device 1, a morphology having traces extending in a plurality of directions (at least the first direction 23 and the second direction 25) was observed. It is considered that the molecular orientation is changed in the lower region of the streak-shaped portion where the film of the alignment layer 7 is cut. The surface roughness of the α-6T (50 nm) layer corresponding to the p / n interface in the photoelectric conversion device did not increase as compared with the device without friction. Therefore, the reason why the energy conversion efficiency of both the uniaxial device and the photoelectric conversion device 1 is higher than that of the non-friction device is due to other reasons such as an increase in absorbance rather than an increase in the contact surface area at the p / n interface. I think that.

The energy conversion characteristics of the produced photoelectric conversion device will be described with reference to FIG. FIG. 5 is a diagram illustrating an example of the photocurrent density-voltage characteristics of the photoelectric conversion device 1, a uniaxial device, and a device that does not cause friction (hereinafter, referred to as “a frictionless device”). The non-friction device was produced in the same manner as the production process of FIG. 2 except that the alignment layer 7 was not formed. The measurement was performed under conditions of 100 [mW / cm ² ] and AM1.5. As a measuring instrument, a computer-controlled source meter (2400, manufactured by Keithley) and a simulated solar irradiation device (LHX-500E3, Koken Kogyo Co., Ltd.) were used. In the graph of FIG. 5, the horizontal axis represents voltage [V], and the vertical axis represents current density [mA / cm ² ].

Table 1 compares the characteristics of these devices. The characteristics of the photoelectric conversion device 1 showed energy conversion efficiency and other characteristics comparable to those of the uniaxial device. One possible reason is that the amount of decrease in absorbance in the uniaxial direction due to friction in a plurality of directions was compensated by the increase in absorbance in other directions. Moreover, the photoelectric conversion apparatus 1 showed energy conversion efficiency and other characteristics superior to those of the frictionless device. Table 1 shows average values of measured values of 12 or more devices produced by the same method. On the other hand, the wavelength dependency of the short-circuit current density is calculated from the IPCE spectrum (FIG. 11B) and the sunlight spectrum shown later (FIG. 11C), and the entire wavelength region ( The short-circuit current density of white light) was calculated. The calculated short-circuit current densities were 2.67, 2.70, and 1.59 [mA / cm ² ] for the photoelectric conversion element 1, the uniaxial device, and the friction device, respectively. From this, it can be seen that the measured short-circuit current density J _sc coincided with the short-circuit current density obtained from the IPCE spectrum with good accuracy.

  Here, with reference to FIG. 6, the energy level of the active layer corresponding to each device will be described. FIG. 6 is a diagram showing (a) first and second ionization potentials of the active layer of each device including the photoelectric conversion element 1 and (b) the calculated energy level diagram of the p / n interface. The energy ranking was measured using AC-2 (Riken Keiki Co., Ltd.). As for the photoelectric conversion device 1 and the uniaxial device, an element of quartz glass / α-6T (rub) / α-6T (50 nm) / PTCBI (30 nm) was measured. As for the device without friction, an element of quartz glass / α-6T (50 nm) / PTCBI (30 nm) was measured. In the graph shown in FIG. 6A, the horizontal axis represents irradiation light energy [eV], and the vertical axis represents the square root of the photoelectron yield. The numbers in FIG. 6B represent energy levels [eV].

  With reference to FIG. 6A, the first ionization potential and the second ionization potential of the element corresponding to the photoelectric conversion element 1 were 5.24 [eV] and 5.89 [eV], respectively. The first ionization potential and the second ionization potential of the element corresponding to the uniaxial device were 5.25 [eV] and 5.90 [eV], respectively. The first ionization potential and the second ionization potential of the element corresponding to the device without friction were 4.96 [eV] and 5.81 [eV], respectively. An energy level diagram based on this result is shown in FIG. Therefore, the HOMO-LUMO gap between the p-type layer and the n-type layer of the photoelectric conversion element 1, the uniaxial device, and the non-friction device is 0.84 [eV], 0.84 [eV], and 0.64 [eV], respectively. These values are related to the open-circuit voltage Voc, and as shown in Table 1, are expressed as the difference in the open-circuit voltage obtained from the measurement result of FIG.

Next, the polarization angle dependency of incident light of each device will be described. FIG. 7 is a diagram illustrating an example of the dependency of the photoelectric current density of the photoelectric conversion device 1 on the incident light polarization angle. Photoelectric converter 1, uniaxial device or frictionless device was produced. Polarized light was incident on the produced device and the short circuit current density was measured. The incident light was 100 [mW / cm ² ] (AM1.5) before being polarized, and the light intensity after passing through the polarizer was 33 [mW / cm ² ]. As a measuring instrument, a computer-controlled source meter (2400, Keithley) and a simulated sunlight irradiation device (LHX-500E3) were used. The measured value was rounded off to the third decimal place. The scale in FIG. 7 represents the short circuit current density J _sc [mA / cm ² ]. The arrows in FIG. 7 indicate the friction direction in the uniaxial device and the first friction direction in the photoelectric conversion device 1.

  In the case of the photoelectric conversion device 1, it had three or more maximum values with respect to the polarization angle. In the case of a uniaxial device, it had two maxima for the polarization angle. It is considered that the orientational organic substances in the active layer are each oriented in the direction of friction. On the other hand, in the case of the device without friction, the same value of photocurrent density was obtained with respect to the polarization angle, and it did not have a maximum value with respect to the polarization angle of incident light. It is considered that anisotropy with respect to the polarization angle of incident light was not observed because the oriented organic material in the active layer of the frictionless device was randomly oriented.

  Moreover, the value of the short circuit current density of the photoelectric conversion device 1 exceeded that of the non-friction device at all polarization angles. One reason for this is that molecules that are oriented so that the molecular plane stands in the film thickness direction are oriented so that the molecular plane is oriented parallel to the active layer plane, so that the transition dipole moment of the molecule and the direction of the electric field vector of the light It is considered that the number of molecules that effectively absorb light increases.

  Therefore, the dependence of the absorbance of each device on the polarization angle will be described with reference to FIG. FIG. 8 is a diagram showing an example of the polarization angle dependence of the absorbance of the active layer 12 formed on the alignment layer 7, where (a) the light incident direction of the polarized light to the device, (b) α The polarization angle dependency when a 360 nm monochromatic light corresponding to the -6T absorption region is incident and (c) the polarization angle dependency when a 670 nm monochromatic light corresponding to the PTCBI absorption region is incident are shown. The scales in FIGS. 8B and 8C represent the absorbance at 360 nm and 670 nm, respectively.

  In the measurement of FIG. 8B, for the photoelectric conversion device 1 and the uniaxial device, an element of quartz glass / α-6T (rub) / α-6T (50 nm) was used as a measurement target. For the device without friction, a quartz glass / α-6T (50 nm) element was used as the measurement object. In the measurement of FIG. 8C, for the photoelectric conversion device 1 and the uniaxial device, an element of quartz glass / α-6T (rub) / α-6T (50 nm) / PTCBI (30 nm) was measured. As for the device without friction, an element of quartz glass / α-6T (50 nm) / PTCBI (30 nm) was measured. The vapor deposition rate was the same as in the production process of FIG. The arrows in FIG. 8 indicate the friction direction in the uniaxial device and the first friction direction in the photoelectric conversion device 1. As a measuring instrument, an ultraviolet visible near infrared spectrophotometer (V-670, JASCO Corporation) was used.

  With reference to FIG.8 (b), compared with the device without friction, the photoelectric conversion apparatus 1 has an increase in absorbance in all directions. In addition, it can be seen that the photoelectric conversion apparatus 1 has increased absorbance in a plurality of directions as compared to the uniaxial device. From this, it can be seen that in the active layer 12 of the photoelectric conversion device 1, the molecules are aligned in a plane parallel to the surface of the active layer 12.

  Furthermore, similar results were obtained with reference to FIG. That is, it can be seen that the orientation effect of the orientation layer 7 is also exerted on the n-type layer 11 laminated away from the orientation layer 7 with the p-type layer 9 interposed therebetween.

  Next, the orientation in the film thickness direction will be described with reference to FIGS. FIG. 9 is a diagram showing the absorbance when the inclination of the substrate with respect to the incident direction is changed. (A) When light is incident on the substrate vertically, (b) The substrate is inclined by 80 ° from the case of (a). FIG. Regarding the photoelectric conversion apparatus 1 and the uniaxial device, an element of quartz glass / α-6T (rub) / α-6T (50 nm) was used as a measurement target. For the device without friction, a quartz glass / α-6T (50 nm) element was used as the measurement object. As a measuring instrument, an ultraviolet visible near infrared spectrophotometer (V-670, JASCO Corporation) was used. The wavelength range of incident light was 300-600 nm corresponding to the absorption wavelength range of α-6T. FIG. 10 is a diagram in which the wavelength range of incident light in FIG. 9 is 600 to 900 nm corresponding to the absorption wavelength range of PTCBI. However, for the photoelectric conversion device 1 and the uniaxial device, an element of quartz glass / α-6T (rub) / α-6T (50 nm) / PTCBI (30 nm) was used as a measurement target. As for the device without friction, an element of quartz glass / α-6T (50 nm) / PTCBI (30 nm) was measured. 9 and 10, the horizontal axis represents the wavelength [nm] of incident light, and the vertical axis represents the absorbance.

  9 and 10, the absorbance of incident light from the vertical direction was higher in the element corresponding to the photoelectric conversion device 1 and the uniaxial device than in the element corresponding to the non-friction device (FIGS. 9A and 9B). 10 (a)). On the other hand, when it was tilted by 80 °, the opposite result was obtained (FIG. 9 (b) and FIG. 10 (b)). The light has an electric field vector perpendicular to the traveling direction. Therefore, when it is tilted by 80 °, the absorbance of the molecules oriented approximately in the film thickness direction of the element is measured. From FIG. 9 and FIG. 10, it can be seen that in both the photoelectric conversion element 1 and the uniaxial device, the absorbance of the molecules oriented in the film thickness direction decreased and the absorbance of the molecules oriented in the direction parallel to the active layer increased. That is, it can be seen that the number of molecules oriented in the direction in which the molecular plane stands in the film thickness direction decreases, and the number of molecules in which the molecular plane is oriented parallel to the active layer plane increases accordingly.

FIG. 11 shows an example of wavelength dependence of (a) absorbance, (b) Incident Photon-to-current Conversion Efficiency (IPCE), and (c) short-circuit current density of the photoelectric conversion device 1. FIG. 11, the horizontal axis represents the wavelength [nm] of incident light, and the vertical axis represents (a) absorbance (1-transmittance), (b) IPCE, (c) short-circuit current density Jsc [mA / cm ² nm].

  In any case, the characteristics of the photoelectric conversion device 1 were improved as compared with the device without friction. Specifically, the absorbance was 1.83 times at 400 nm and 1.45 times at 700 nm. IPCE was 2.11 times at 400 nm and 1.55 times at 700 nm. Moreover, the same value as the device which rubbed only in the uniaxial direction was shown. As a factor other than the increase in absorbance that contributed to the improvement of energy conversion efficiency, it is considered that the efficiency of exciton diffusion and dissociation, and charge transport and extraction increased due to molecular orientation.

Thus, the exciton diffusion length will be described with reference to FIG. FIG. 12 is a diagram illustrating an example of (a) the spectral fluorescence spectrum of the active layer of the photoelectric conversion device 1 and (b) a fitting curve for calculating the exciton diffusion length. JASCO FP-6500 (manufactured by JASCO Corporation) was used as a spectrofluorometer. The wavelength of the excitation light was 420 nm. In FIG. 12A, the horizontal axis represents the wavelength [nm] of incident light, and the vertical axis represents the fluorescence intensity. In FIG. 12B, the horizontal axis represents the film thickness [nm] of the α-6T layer, and the vertical axis represents the value of PL ₁ / PL ₂ . Here, in the spectrofluorescence analysis, for the photoelectric conversion device 1 and the uniaxial device, the excitons generated in the quartz glass / α-6T (rub) / α-6T (20-50 nm) element and the α-6T layer are used. A quartz glass / α-6T (rub) / α-6T (20 to 50 nm) / PTCBI (5 nm) element in which PTCBI was further laminated as a layer for quenching was measured. Regarding the non-friction device, quartz glass / α-6T (20 to 50 nm) element and quartz glass / α-6T (20 to 50 nm) / PTCBI (5 nm) element were measured. In addition, devices with an α-6T layer thickness of 20 nm, 30 nm, 40 nm, and 50 nm were fabricated. The exciton diffusion length L was calculated by Equation (1) using the value of the fluorescence intensity of about 590 nm at which the fluorescence peak was observed in FIG. 12A (see Reference 1).

Where PL ₁ ; α-6T fluorescence peak intensity in the element with quench layer, PL ₂ ; α-6T fluorescence peak intensity in the element without quench layer, L; exciton diffusion length [nm], d; α -6T film thickness [nm].

  The calculated results are shown in Table 2. The exciton diffusion length in the photoelectric conversion apparatus 1 exceeded the exciton diffusion length of not only a frictionless device but also a uniaxial device. The long exciton diffusion length means that the probability of excitons reaching the p / n interface increases even when the film thickness is increased and the number of excitons generated away from the p / n interface increases. means. For this reason, the possibility of further improving the energy conversion efficiency of the photoelectric conversion device 1 is expected by optimizing the manufacturing conditions such as the film thickness.

  Next, the durability of the photoelectric conversion device 1 will be described with reference to FIG. FIG. 13 is a diagram illustrating an example of the change over time of the characteristics of the photoelectric conversion device 1. (A) Open-circuit voltage, (b) Short-circuit current density, (c) FF, (d) Energy conversion efficiency change over time. FIG. In each graph of FIG. 13, the horizontal axis represents elapsed time [hour], and the vertical axis represents (a) standardized open-circuit voltage, (b) short-circuit current density, (c) FF, and (d) energy conversion efficiency. Represents.

  As for the characteristics of the photoelectric conversion device 1, the deterioration rate of characteristics other than the open-circuit voltage was slower than that of the non-friction device. In particular, the FF significantly decreased with time in a device that did not rub, whereas in the case of the photoelectric conversion device 1, the deterioration was moderate. As a result, the deterioration of the energy conversion efficiency of the photoelectric conversion apparatus 1 was more gradual than that of the device without friction. Compared to the uniaxial device, there was almost no difference in terms of change over time.

  Next, the friction conditions in the friction step will be described with reference to FIG. The photoelectric conversion device 1 was produced in a glove box filled with nitrogen without performing the friction step in a nitrogen atmosphere and being exposed to air including the friction step. A dust-free nylon cloth was used in the friction step. On the other hand, for comparison, friction was performed in the air, and a photoelectric conversion device 31 using a normal nylon cloth (an example of “friction means” in the claims of the present application) as the friction means 17 was produced. The other production processes were the same as in Example 1.

  FIG. 14 is a diagram illustrating an example of photocurrent density-voltage characteristics of each photoelectric conversion device. Table 3 shows characteristic values obtained from the measurement. The characteristic of the photoelectric conversion device 1 was superior to that of the photoelectric conversion device 31. From this result, it is understood that the characteristics of the photoelectric conversion device are improved by performing the friction step in an inert gas atmosphere and using a dust-free nylon cloth as the friction means 17.

  The details of the friction force, speed, number of times, direction, order, friction means, and the like in the friction step of the alignment layer may be appropriately changed. In particular, as a friction means, a cloth of another material may be used instead of the nylon cloth. Moreover, when using cloth as a friction means, the cloth which woven the thread | yarn may be used and a nonwoven fabric may be used.

  Furthermore, the alignment layer and the active layer may be formed using the same material or different materials. Moreover, the layer which contains 2 or more types of materials, respectively may be sufficient. Further, the active layer may be a single layer serving both as a p-type layer and an n-type layer, for example, as in a bulk heterojunction structure.

Further, the material used for the alignment layer and the p-type layer may be a material other than α-6T. For example, aromatic hydrocarbons such as pentacene and rubrene, oligomers such as 6P and 8T, polymers such as P3HT, MEH-PPV, MDMO-PPV, PFO and PFO-DMP, CuPc, ZnPc, CoPc, TiOPC, PbPc, NiPc, It may be a phthalocyanine derivative such as SbPc, a porphyrin derivative such as H ₂ TPP, a triphenylamine derivative such as α-NPD or TPD, or a mixture of two or more of these.

Furthermore, the material used for the n-type layer may be a material other than PTCBI. For example, PDCDA, PenPTC, ADIDI, PTCDA, PTCDI, NTDA, MePTC, HepPTC and other perylene derivatives, C _n (n = 60, 70, 76, 84, etc.), PCBM (C _n ) (n = 60, 70, 76) , 84, etc.), fluorine-substituted compounds such as F16CuPc, etc., or a mixture of two or more of these.

  Furthermore, if the material used for the active layer adjacent to the alignment layer 7 is an oriented organic material, the other materials used for the active layer may not be the oriented organic material. In the example of this embodiment, if only the p-type layer 9 adjacent to the alignment layer 7 is an oriented organic material, the n-type layer 11 may be formed of a material other than the oriented organic material. This is because even with such a structure, an orientation effect at least in the p-type layer can be obtained.

  Furthermore, the photoelectric conversion device 1 may include a carrier extraction layer that facilitates carrier extraction between the electrode layer and the active layer, or between the electrode layer and the alignment layer.

Furthermore, the photoelectric conversion device 1 may use a material other than BCP as the buffer layer. For example, oxadiazole derivatives such as PBD, OXD-7, Bpy-OXD, BP-OXD-Bpy, and Bpy-FOXD, triazole derivatives such as TAZ and NTAZ, phenanthroline derivatives such as Bphen, NBphen, and HNBphen, Liq, BAlq, and the like phosphoric acid derivatives of the metal complexes, such Popy ₂ of, mCP, TCTA, CBP, carbazole derivatives such CDBP, MPT, DPT, triazine derivatives such as TPT, BPyB, TpyB, may be a such as pyridine derivatives, such as B4PyMPM A mixture of two or more of these may be used. Further, the buffer layer may not be provided.

  Further, a substrate other than a glass substrate may be used. For example, a substrate such as quartz, sapphire, or metal may be used, or a polymer substrate such as PEN may be used. Further, instead of the ITO electrode and the Ag electrode, an electrode made of a material such as Pt, Au, Al, In, Mg, Ca, Cs, Li, Ba, Na, IZO, AZO, or carbon nanotube may be used. Furthermore, the electrode may be a multilayer film or an alloy.

  Furthermore, the film forming speed may be changed as appropriate. In the active layer forming step, a heating step for raising the substrate temperature may be performed. For example, it is preferable in that the orientation degree of the active layer is expected to be improved by the heating means raising the substrate temperature.

  Furthermore, the alignment layer and the active layer may be formed by a method other than the vacuum deposition method. For example, other dry processes include chemical vapor deposition and laser ablation. Examples of the wet process include a spin coating method and an ink jet method. By adopting a wet process, it becomes easy to adopt polymer materials.

[References]
1. Peter Peumans, Aharon Yakimov, and Stephen R. Forrest “Small molecular weight organic thin-film features and solar cells” J. Appl. Phys., 93, 3693 (2003).

  DESCRIPTION OF SYMBOLS 1 ... Photoelectric conversion apparatus, 7 ... Orientation layer, 9 ... P-type layer, 11 ... N-type layer, 12 ... Active layer, 17 ... Friction means, 18 ... First 1 direction, 19 ... 2nd direction

Claims (11)

A method for producing a photoelectric conversion device having an alignment layer having a first alignment organic substance and an active layer for converting incident light into electricity,
An alignment layer forming step of forming the alignment layer using the first alignment organic material;
A first friction step of rubbing the alignment layer in a first direction in a plane parallel to the alignment layer;
A second friction step for rubbing the alignment layer in a second direction different from the first direction in a plane parallel to the alignment layer;
An active layer forming step of forming the active layer using a second alignment organic material. The alignment layer is rubbed in n different directions (n is a natural number of 2 or more) including the first direction and the second direction,
The method for producing a photoelectric conversion device according to claim 1, wherein a smaller one of the angles formed by the first direction and the second direction is 180 / n [°].   3. The method for producing a photoelectric conversion device according to claim 1, wherein, in the first friction step and / or the second friction step, the alignment layer is rubbed with a dust-free cloth in an inert gas atmosphere. . A method for producing a photoelectric conversion device having an alignment layer having a first alignment organic substance and an active layer for converting incident light into electricity,
An alignment layer forming step of forming the alignment layer using the first alignment organic material;
A rubbing step of rubbing the alignment layer under an inert gas atmosphere;
An active layer forming step of forming the active layer using a second alignment organic material. A photoelectric conversion device having an active layer for converting incident light into electricity,
The active layer includes an organic material oriented in a first direction in a plane parallel to the active layer and a second direction different from the first direction. The oriented organic material is oriented in n directions (n is a natural number of 2 or more) different from each other including the first direction and the second direction,
6. The photoelectric conversion device according to claim 5, wherein the smaller one of the angles formed by the first direction and the second direction is 180 / n [°]. A photoelectric conversion device having an active layer for converting incident light into electricity,
The active layer contains an oriented organic material,
Absorbance of the active layer with respect to polarized monochromatic light incident on the active layer from a direction perpendicular to the active layer having an absorption peak wavelength of the oriented organic material, or short circuit when the polarized monochromatic light is incident A rotation angle (0 ° or more) when the active layer is rotated in a plane perpendicular to the light traveling direction, such as current density, internal quantum efficiency, external quantum efficiency, internal energy conversion efficiency, or external energy conversion efficiency The photoelectric conversion device has three or more maximum values including a first direction and a second direction different from the first direction with respect to less than 360 °. A photoelectric conversion device having an active layer for converting incident light into electricity,
The active layer contains an oriented organic material,
The photoelectric conversion device, wherein the active layer has a morphology extending in a streak shape in a first direction and a morphology extending in a second shape different from the first direction. An alignment layer having a first alignment organic material aligned in the first direction and the second direction;
The photoelectric conversion device according to claim 5, wherein the alignment layer is adjacent to the active layer. A photoelectric conversion device production device that converts incident light into electricity,
Friction means for rubbing the oriented organic layer of the photoelectric conversion device in a direction in a plane parallel to the oriented organic layer;
A production apparatus for a photoelectric conversion device, comprising: an orientation organic layer and / or a rotation unit that relatively rotates the friction unit. The friction means is
Dust-free cloth,
The apparatus for producing a photoelectric conversion device according to claim 10, further comprising an inert gas applying unit configured to apply an inert gas for rubbing the oriented organic layer in an inert gas atmosphere.