JP2005011841A - Vertical junction organic photovoltaic device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pn junction photovoltaic device of photo-conductive organic semiconductor, that is, an organic solar cell, where a light irradiating the solar cell is much absorbed by an active zone near a pn junction, and the solar cell is made low in internal resistance. <P>SOLUTION: A pn junction 15 composed of a p-channel organic semiconductor layer 12 and an n-channel organic semiconductor layer 14 is sandwiched between electrodes 16 and 18. The pn junction 15 has an interface between light irradiation surfaces 12a and 14a, extending in a direction perpendicular to the light irradiation surfaces 12a and 14a. All positive/negative carriers generated near the pn junction are collected by the lateral electrodes 16 and 18, passing through the surface layers (layer as thick as light is penetrable) 12a and 14a of a pn junction cell irradiated with light. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an organic optoelectronic device, and more particularly to a pn-junction photovoltaic device using a photoconductive organic semiconductor.
[0002]
[Prior art]
A pn junction type photovoltaic device using an organic semiconductor is called an organic solar cell, and takes out photocarriers generated at the pn junction as a current. A typical example is shown in FIG. 13, and phthalocyanine H as the p-type organic semiconductor layer 2 is used. ₂ Pc and the perylene derivative Me-PTC as the n-type organic semiconductor layer 4 are laminated to form a pn junction 5 and sandwiched between the electrodes 6 and 8. Reference numeral 10 denotes a transparent glass substrate as a support substrate. A gold (Au) electrode is used as the electrode 6 in contact with the p-type organic semiconductor layer 2, and an ITO (indium tin oxide) transparent electrode is used as the electrode 8 in contact with the n-type organic semiconductor layer 4. Light enters the pn junction 5 through the transparent electrode 8 (see Non-Patent Document 1).
[0003]
However, the organic solar cell of the type in which the pn junction 5 is arranged so as to be parallel to the light irradiation surface irradiated with light in this way has a very thin active region thickness for photocarrier generation, and pn The photoelectric energy conversion efficiency was 1% or less from the characteristic that not only the thickness of the junction 5 was only several tens of nm on both sides of the junction 5 but also the internal resistance of the device was very high, which was far from practical use.
There is also an attempt of a tandem cell in which two or more pn junction cells are stacked (see Non-Patent Document 2), but it has not led to a significant improvement in conversion efficiency.
[0004]
[Non-Patent Document 1]
C. W. Tang, Appl. Phys. Lett. , 48, 183 (1986).
[Non-Patent Document 2]
M.M. Hiramoto, M.M. Suezaki, M .; Yokoyama, Chem. Lett. , 1990, 327 (1990).
[Non-Patent Document 3]
M.M. Hiramoto, H.M. Fukusumi, M.M. Yokoyama, Appl. Phys. Lett. 61, 2580 (1992).
[0005]
[Problems to be solved by the invention]
The major causes of the poor efficiency of organic solar cells are (1) the thickness of the active region for generating photocarriers is very thin and (2) the internal resistance is very high, as described above. The serious effects of the above on the cell characteristics of the structure of FIG. 13 are listed as follows.
[0006]
(1) Since only the vicinity of the pn junction is photoactive, when a film thicker than the active layer width is produced, all of the extra thick portions become inactive layers that do not generate photocurrent even if they absorb light, and light is not The active layer is considerably absorbed and only a little light reaches the active pn junction that can generate a photocurrent. This is called a masking effect. Therefore, only a small photocurrent flows.
[0007]
(2) If the cell is made thin in order to avoid the above masking effect and the organic semiconductor layers 2 and 4 have a very thin film thickness of several tens of nanometers, for example, cell conduction (the upper and lower electrodes 6, 6) 8 will come into contact with each other), and it will not function as a solar cell.
[0008]
(3) Even if the cell can be made thin, a considerable portion of incident light is not absorbed by the thin active layer but passes through the cell and escapes, so that the photoelectric conversion efficiency does not increase.
{Circle around (4)} When the organic semiconductor layer is thick, the back portion of the film where light cannot enter due to absorption is in a dark state. An organic semiconductor is close to an insulator in a dark state, and if the cell is made thick to absorb all incident light, the internal resistance becomes very high. On the other hand, the photocurrent cannot reach the electrode unless it passes through the high resistance portion. As a result, the photocurrent density, fill factor (FF: fill factor), and photovoltaic voltage are drastically reduced.
[0009]
In order to fundamentally solve these problems, it is necessary to realize a cell in which a large amount of irradiated light is absorbed in the active region near the pn junction and the internal resistance is lowered.
The object of the present invention is to provide a solar cell structure that satisfies these requirements.
[0010]
[Means for Solving the Problems]
The organic photovoltaic device of the present invention includes a pn junction composed of a p-type organic semiconductor layer and an n-type organic semiconductor layer as a photovoltaic layer, and the pn junction has an edge on the light irradiation surface and is irradiated with light. A vertical junction organic photovoltaic device characterized in that it is formed in a direction perpendicular to the surface.
[0011]
As shown in FIG. 1, a pn junction 15 composed of a p-type organic semiconductor layer 12 and an n-type organic semiconductor layer 14 has an edge on the light irradiation surfaces 12a and 14a and is perpendicular to the light irradiation surfaces 12a and 14a. It is formed in the direction. Reference numerals 16 and 18 denote electrodes.
Since the pn junction 15 is perpendicular to the light irradiation surface, all of the light that has entered the organic semiconductor layer is near the pn junction (a region having a width smaller than about 100 nm with the pn junction in the middle). Absorption by the inactive layer, that is, absorption without loss due to the masking effect, contributes to the generation of photocurrent. The pn junction can be realized by a laminated body of organic semiconductor thin films, and in that case, light is irradiated to the end face of the organic semiconductor thin film, so that the direction from the irradiation surface to the back is 1 mm or more. Now, an upright organic film can be continued, and virtually all light is absorbed even in a wavelength region having a small absorption coefficient.
[0012]
Further, as shown in FIG. 2, if a vertical junction type organic photovoltaic cell having a plurality of junctions is formed by forming such vertical pn junctions 15 at an interval of 100 nm, for example, the entire light irradiation surface is formed. Works as an active layer, and there is essentially no loss of light, and the photocurrent generated by all incident light can be used effectively. The structure of this solar cell is Pt / H ₂ Pc layer (thickness 50 nm) / Me-PTC layer (thickness 50 nm) / Au layer (thickness 1 nm) / H ₂ Pc layer (thickness 50 nm) / Me-PTC layer (thickness 50 nm) / Au layer (thickness 1 nm) / ...... H ₂ Pc / Me-PTC / In / Ag. The reverse np junction at the interface between the pn junctions formed when a large number of pn / pn /... / Pn are joined is eliminated by inserting a metal ultrathin film (about 1 nm) as will be described later. be able to. That is, the above problem (1) can be fundamentally solved by employing the cell structure of the present invention.
[0013]
Further, as shown in FIG. 1, positive and negative carriers generated in the vicinity of the pn junction are all exposed to cell surface layer portions (thickness portions where light can enter from the surface) 12a, 14a, and the left and right electrodes 16, 18 collected. The conductivity under light irradiation, i.e. the photoconductivity, is much greater than the conductivity under dark conditions, i.e. dark conductivity, i.e. the resistance is much lower. As a result, the internal resistance of the cell can be fundamentally reduced. This phenomenon is the same even when a plurality of pn junctions are stacked as shown in FIG. That is, the above problem (2) can be fundamentally solved by employing the cell structure of the present invention.
Thus, the vertical junction organic photovoltaic cell of the present invention can fundamentally solve the major problems of the cell having the structure shown in FIG.
[0014]
A plurality of pn junctions may be provided, and the pn junctions may have a series connection structure of pn junctions stacked via a metal layer so as to be parallel to each other.
For example, the p-type organic semiconductor layer may be selected from the group consisting of phthalocyanines and quinacridone, and the n-type organic semiconductor layer may be selected from the group consisting of perylene derivatives, naphthalene derivatives and fullerenes.
[0015]
The material of the metal electrode is preferably selected so that the work function of the electrode in contact with the p-type organic semiconductor is large and the work function of the electrode in contact with the n-type organic semiconductor is small. An example of the metal having a high work function is Pt, and an example of the metal having a low work function is In.
At least one of the p-type organic semiconductor layer and the n-type organic semiconductor layer is a laminate in which organic semiconductor layers having different band structures are laminated so as to form a staircase energy structure, or a laminate in which organic semiconductor layers having different light absorption characteristics are laminated. It may be a body.
[0016]
The manufacturing method of the present invention for producing the vertical junction type organic solar cell of the present invention includes a step of forming a first metal electrode layer on a substrate, and a p-type or n-type organic semiconductor on the first metal electrode layer. A step of forming a pn junction layer formed by laminating a thin film and an organic semiconductor thin film of the opposite conductivity type, a step of forming a second metal electrode layer on the pn junction layer, and formation by these steps Cutting the laminated body in a direction perpendicular to the film surface to form a light irradiation surface.
[0017]
The step of forming the pn junction layer is a step of forming a metal layer and a pn junction layer thereon after laminating a p-type or n-type organic semiconductor thin film and an organic semiconductor thin film of the opposite conductivity type. May be included.
[0018]
One method of cutting the laminate on the substrate is a method performed by a microtome. In that case, it is preferable to use a resin substrate as the substrate. In addition, it is preferable to include a step of forming a protective layer covering the laminated body over the second metal electrode layer so as to cover a wider area than the laminated body at least at a position where the laminated body on the resin substrate is cut. .
[0019]
It can also cut | disconnect by methods other than a microtome. Alternatively, a glass substrate can be used as the substrate, and after similarly forming an electrode, an organic pn layer, and an electrode by a vapor deposition method or the like, the glass substrate can be cut to expose the end face of the laminate. In this case, the organic protective layer may be omitted.
At least one of the p-type organic semiconductor thin film and the n-type organic semiconductor thin film may include a step of stacking different types of organic semiconductor thin films.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
In order to confirm the effectiveness of the solar cell structure of the present invention, first, a cell having one vertical pn junction was fabricated as shown in FIG.
[0021]
This cell was produced by the following procedure. First, platinum (Pt) is formed as a metal electrode layer 16 on a flat epoxy resin substrate to a thickness of 2000 nm by vacuum deposition. On top of that, metal-free phthalocyanine (H ₂ Pc) is formed by vacuum deposition to a thickness of 250 nm. Further, a perylene pigment (Me-PTC) is formed thereon as a n-type organic semiconductor layer 14 to a thickness of 250 nm by vacuum deposition. Further, a laminated film (In / Ag) comprising an indium (In) film having a thickness of 100 nm and a silver (Ag) film having a thickness of 100 nm thereon is formed as a metal electrode layer 18 by vacuum deposition. . Further thereon, Im-PTC is formed as a protective layer to a thickness of 750 nm by vacuum deposition. The protective layer is effective in preventing the interface between the electrode and the organic semiconductor layer from peeling off at the time of subsequent slicing (cutting) with a microtome or the like.
[0022]
Im-PTC is used as a protective layer, but this Im-PTC layer does not function as a semiconductor because it is not sandwiched between two electrodes, and is merely an organic protective film. As the protective layer, various organic or inorganic thin film materials can be used.
Next, it slices perpendicularly | vertically to a vapor deposition surface using a microtome, and takes out an end surface. These end surfaces become the light irradiation surfaces 12a and 14a of FIG.
[0023]
FIG. 3 shows an SEM (scanning electron microscope) image of the joint end face obtained by slicing with a microtome. Metal layer (Pt) / Organic semiconductor layer (H ₂ It can be clearly seen that Pc / Me-PTC) / metal layer (In / Ag) is laminated. In order to obtain such a clean end face, it is necessary to use a diamond knife with a microtome.
[0024]
In order to efficiently extract the photocurrent generated at the pn junction to the outside, the junction between the metal layer and the organic semiconductor layer needs to be ohmic. Therefore, H, which is a p-type semiconductor ₂ Pt having a large work function was used for the electrode layer in contact with the Pc layer, and In having a small work function was used for the electrode layer in contact with Me-PTC which is an n-type semiconductor.
[0025]
In order to make electrical contact with the two metal electrodes 16 and 18 and connect them to the external lead wires, the laminate is formed into the pattern of FIG. 4 by vapor deposition, and slicing is performed at the portion where the two electrodes 16 and 18 overlap. It was. Specifically, FIG. 4 is a plan view showing a state in which the obtained laminate is sliced. Reference numeral 11 denotes an epoxy resin substrate, on which an electrode Pt layer 16 is formed in an L shape, and an Ht is formed thereon. ₂ An organic semiconductor layer 13 composed of the Pc layer 12 and the Me-PTC layer 14 is formed. At this time, the pattern of the organic semiconductor layer 13 is set so that a part of the Pt layer 16 is exposed from the organic semiconductor layer 13. On the organic semiconductor layer 13, an (In / Ag) layer 18 as the other electrode is formed in an I shape. At this time, the pattern of the (In / Ag) layer 18 is set so that a part of the (In / Ag) layer 18 protrudes from the organic semiconductor layer 13. Lead wires 24 and 28 are connected to electrode layers 16 and 18 protruding from the organic semiconductor layer 13 by silver pastes 22 and 26, respectively. After that, a protective layer is formed in a region covering this laminate at least at a cutting position where subsequent slicing is performed. For example, the protective layer is formed so as to cover the entire surface of the substrate 11. Slicing is performed at the portion where the two electrodes 16 and 18 overlap as shown in the figure. 20a has shown the part cut | disconnected by the slice, and the part to which the lead wires 24 and 28 are connected becomes a photovoltaic cell of this invention. A cut surface (light-irradiated surface) is exposed at the rice portion, and the cut surface has a laminated structure as shown in FIG. The portion that functions as a solar cell is the portion where the upper and lower Pt electrodes 16 and the In / Ag electrode 18 overlap.
[0026]
Typical examples of p-type and n-type organic semiconductors are shown in FIG. 7, and their absorption spectra are shown in FIG. In FIG. 8, the horizontal axis represents wavelength, and the vertical axis represents absorbance in arbitrary units. The p-type has no metal phthalocyanine (H ₂ There are phthalocyanines including metal-substituted phthalocyanines (MPc) such as Pc) and TiOPc, and quinacridone (DQ). The n-type includes perylene derivatives (Me-PTC, Im-PTC, etc.), naphthalene derivatives (NTCDA, etc.) and fullerenes (C60). However, it is not limited to these. A pn junction can be obtained by combining these p-type and n-type organic semiconductors.
[0027]
In addition, a method for manufacturing the organic semiconductor thin film is not limited to a deposition method such as an evaporation method or a sputtering method, and a wet method such as spin coating may be used depending on the material. As an organic semiconductor thin film that can be formed by a wet method, PPV (polyparaphenylene and C is used in polymer solar cell systems). ₆₀ And a system in which a derivative thereof is dispersed.
[0028]
As the organic semiconductor thin film, a resin-dispersed organic semiconductor film in which an organic semiconductor is dispersed in a resin can also be used. Examples of the resin for dispersing the organic semiconductor include general-purpose polymers such as polycarbonate, polyvinyl butyral, polyvinyl alcohol, polystyrene, and polymethyl methacrylate, and conductive polymers such as polyvinyl carbazole, polymethylphenylsilane, and polydimethylsilane. Some chemical formulas of these resins are shown in FIG.
[0029]
Resin-dispersed organic semiconductor films are prepared by spin-coating or bar-coating a mixture of an organic semiconductor and a resin in a solvent on the electrode substrate (a method in which the dispersion applied on the substrate is thinly stretched with a metal rod with grooves. ) To form a film. The resin-dispersed organic semiconductor film is convenient for increasing the area.
[0030]
FIG. 5 shows current-voltage (IV) characteristics of the cell shown in FIG. Light is 100mW / cm ² (AM1.5) simulated sunlight is irradiated. The left vertical axis is the absolute value of photocurrent, and the right vertical axis is the light irradiation area (1.25 × 10 ^-6 cm ² 1cm divided by the absolute value of photocurrent ² Per photocurrent density. The white circle is when light is irradiated, and the black circle is when dark. Although the total width of the organic semiconductor layers 12 and 14 was as large as 500 nm, a good fill factor (FF: 0.46) and open-circuit voltage (Voc: 0.3 V) were observed. FF is good because photogenerated carriers are collected on the electrode through only the light irradiated portion, and the low internal resistance of the cell contributes greatly. This result means that the problem (2) can be solved by the present invention. If the cells having the same film thickness and the conventional structure shown in FIG. 13 are used, the FF becomes very bad.
[0031]
The observed short-circuit photocurrent (Isc) is 20 nA (vertical axis left plot). Although the absolute value is small, the area of this cell is the area exposed to light (light irradiation surface (12a, 14a) in FIG. 1) [(width of organic semiconductor layers 12, 14: 500 nm) × (organic semiconductor layer length). In this cell, 1.25 × 10 ^-6 cm ² It becomes. Therefore, the short circuit photocurrent density (Jsc) is 16 mA / cm. ² And a very large value (vertical plot on the right). Such a large photocurrent density has never been observed in organic solar cells. Further, this photocurrent density is larger than that of amorphous silicon, comparable to that of polycrystalline silicon, and close to that of CdS / CdTe, so that it is sufficient for ordinary inorganic solar cells. The size is comparable. The photoelectric energy conversion efficiency at this time is 2.2%. As will be described later, this value can be greatly improved by joining many pn junctions.
[0032]
FIG. 6 shows the wavelength dependence of Jsc by black square dots. Me-PTC and H ₂ The absorption spectrum of Pc is also shown. Thus, Me-PTC and H ₂ It can be seen that a photocurrent is generated in both absorption regions of Pc and has sensitivity in the entire visible region. In the conventional cell structure of FIG. ₂ With a film thickness of Pc (250 nm) / Me-PTC (250 nm), a photocurrent is generated only in the absorption region of one organic semiconductor on the opposite side of the irradiated surface due to the masking effect. The result of FIG. 6 means that the above-described masking effect is essentially absent in a cell having a vertical pn junction. In the vicinity of the upright pn junction, since there is no inactive layer, the absorbed light is not lost and contributes to the photocurrent. Furthermore, even in a wavelength region where the absorption coefficient is low (such as the bottom of the absorption spectrum), the organic semiconductor layer exists with a thickness of 1 mm or more from the light irradiation surface toward the back, so that the irradiated light It can be said that substantially all of the light is absorbed (if there is a 1 μm organic semiconductor layer, light is almost absorbed in view of the absorption coefficient of the organic semiconductor). Further, since all absorbed light is collected by the electrode standing perpendicular to the irradiated surface, as in the case of the outermost surface layer, all of the light can contribute to the generation of photocurrent.
[0033]
As described above, since the solar battery cell of the present invention has a very high light utilization efficiency, it is 16 mA / cm. ² It can be said that an unprecedented large Jsc was obtained. This result means that the problem (1) can be solved by the cell structure of the present invention.
[0034]
Although the above photocurrent density is large, it is not yet optimized. The reason is that photocurrent is generated only in the vicinity of the pn junction (50 nm on each side of the pn junction and a total thickness of about 100 nm). This is because 400 nm of the total width 500 nm of the organic semiconductor layers 12 and 14 does not contribute to the generation of optical carriers, and only carriers are flowing. Therefore, if the cell film thickness can be reduced to 100 nm, it can be expected that a considerably larger Jsc can be obtained. Heretofore, when the total width of the organic semiconductor layer is 1000 nm (the width at which carriers are not generated is 900 nm), 4 mA / cm ² In the case of 500 nm (the width at which carriers are not generated is 400 nm), as described above, 16 mA / cm ² Is obtained. That is, although the light irradiation area is reduced by half, the absolute value of the generated photoelectric flow rate (not the photocurrent density divided by the area) is doubled. It can be seen that the short-circuit photocurrent increases four times as the light irradiation area (because the width of the organic semiconductor layer is halved) is halved. From this result, it is considered that the photocurrent density is considerably increased at the width of 100 nm.
[0035]
In the solar cell structure of the present invention, the remarkable features other than those described so far will be described.
(1) As shown in FIG. 2, a large voltage can be taken out by connecting a large number of pn junctions in series.
Let us consider a cell in which the thickness of one pn junction cell is 100 nm and five pn junctions are connected in series. A pn / pn / pn / pn / pn junction is formed, but an ultrathin metal film is inserted so that a pn junction in the reverse direction is formed at the slash (/) and the photovoltage is not canceled. Specifically, in the pn junction series structure, the insertion of a very thin metal layer (for example, a thin film such as Au or Ag having a film thickness of about 1 nm) eliminates an electromotive voltage in the reverse direction, and the entire obtained structure. It is known that the open-circuit voltage (Voc) is expressed by the product of the number of pn junctions and Voc indicated by one pn junction (see Non-Patent Document 2). Since Voc in FIG. 5 is 0.3V, if five pn junctions are connected, a voltage of 0.3V × 5 = 1.5V can be obtained with the same area. In this structure, any number of pn junctions can be connected and there is no limit. In the conventional cell of FIG. 13, when the pn junction is overlapped (tandem type), light reaching the pn junction on the rear side is reduced by absorption of the pn junction on the light irradiation side. Two or three is the limit. A conversion efficiency of about 5% is considered possible.
[0036]
(2) Photocurrent can be generated by absorption over most or the entire wavelength region of the sunlight spectrum.
In the solar cell structure of the present invention, when organic semiconductors having different absorption wavelength ranges are stacked, the entire solar spectrum can be covered in principle. As can be seen from the spectrum of FIG. 8, the Me-PTC / H shown above. ₂ The combination of Pc covers almost all visible light. For example, if TiOPc or Im-PTC sensitive to infrared light is added, almost the entire solar spectrum can be absorbed. So far, it has been said that the organic solar cell can absorb all the solar spectrum with a combination of organic semiconductors having various absorption wavelengths. However, the above two problems (1) and (2) Such a feature has been erased, and the feature has hardly been revealed as a cell characteristic in practice. However, the features of the solar cell structure of the present invention clearly appear. As shown in FIG. 6, the wavelength dependence without the masking effect is evidence. This is a great advantage of the structure of the present invention.
[0037]
An inorganic semiconductor cannot absorb light having an energy smaller than its band gap (for example, 1.1 eV in crystalline silicon). This determines the theoretical limit of photoelectric energy conversion efficiency, but the solar cell structure of the present invention may possibly achieve an efficiency exceeding the limit.
[0038]
In addition, as shown in FIG. 9, it is possible to further improve the quantum efficiency of generating a photocurrent by appropriately combining organic semiconductor band structures to create a staircase energy structure (see Non-Patent Document 3). . The staircase energy structure facilitates the separation of photogenerated electrons and holes.
[0039]
In addition, when laminating these semiconductor layers in the organic semiconductor layer, the wavelength of sunlight is much longer (300 nm to 1800 nm) even if the film width of each semiconductor layer is as thin as several tens of nm. , Such thin film width cannot be identified (wavelength limit: structures smaller than wavelength, objects cannot be identified). For example, as schematically shown in FIG. 10, if the total width of the organic semiconductor layers is 1 μm (1000 nm) and there are several organic semiconductor layers with a 50 nm film width that absorb a specific wavelength region within the width, Even if there is no semiconductor layer that absorbs the wavelength region in any other layer, all the light in the specific wavelength region having a width of 1 μm is absorbed. This may be called a quantum light condensing effect. This is because the above properties are derived from particle-wave duality, where light behaves as a wave when propagating and behaves as a single photon when absorbed by a semiconductor.
[0040]
(3) Driving under condensing conditions is suitable.
Under condensing, the photoconductivity increases, the influence of internal resistance is reduced, and a large current may flow. As will be described later, this feature is effective when the area is increased.
[0041]
(4) Large area method:
Although the area of the solar battery cell of the present invention is small because it uses the film end face, if a large number of pn junctions are stacked and the total film thickness is increased to about 10 μm, each cell 30 is shown in FIG. It is possible to collect light and generate electric power by placing the end face portion of the lens on the end of the cylindrical lens 32, and the problem of increasing the area can be solved.
[0042]
The vertical junction type organic photovoltaic cell of the present invention has the potential to surpass inorganic solar cells from the viewpoint of effective use of the entire solar spectrum. In addition, a very large voltage can be taken out by connecting a large number of pn junctions in series (when 1000 pieces are connected, 0.3 × 1000 = 300 V. At this time, the organic layer width is 100 nm × 1000 = 10 μm).
[0043]
According to the present invention, a photoelectric energy conversion efficiency of at least 5% or more can be obtained. Actually, in the example, 16 mW / cm ² However, a large photocurrent density that could not be observed in organic systems has been obtained. Larger areas can also be solved by considering light collection with a lens. The present invention can provide a photoelectric energy conversion by an organic semiconductor, that is, an organic solar cell having a practical efficiency of 5% or more, which has been difficult until now.
[0044]
【The invention's effect】
The organic photovoltaic device of the present invention includes a pn junction composed of a p-type organic semiconductor layer and an n-type organic semiconductor layer as a photovoltaic layer, and the pn junction has an edge on the light irradiation surface and is irradiated with light. Since it is formed in a direction perpendicular to the surface, it is possible to achieve a higher photoelectric energy conversion efficiency than conventional organic semiconductor solar cells.
If a pn junction is connected in series with a plurality of pn junctions and these pn junctions are stacked via a metal layer so as to be parallel to each other, a large voltage can be taken out, and the conventional organic semiconductor Thus, photoelectric energy conversion efficiency of 10% or more, which has been considered impossible, can be realized.
If the metal electrode is selected so that the work function of the electrode in contact with the p-type organic semiconductor is large and the work function of the electrode in contact with the n-type organic semiconductor is small, the metal layer and the organic semiconductor layer The junction between them can be made ohmic, and the photocurrent generated at the pn junction can be efficiently extracted to the outside.
If at least one of the p-type organic semiconductor layer and the n-type organic semiconductor layer is a stacked body in which organic semiconductor layers having different band structures are stacked so as to form a staircase energy structure, quantum efficiency for generating a photocurrent can be further improved. Will be able to.
If at least one of the p-type organic semiconductor layer and the n-type organic semiconductor layer is a laminate in which organic semiconductor layers having different light absorption characteristics are laminated, a photocurrent can be generated by absorption over most or the entire wavelength region of the solar spectrum. Can be.
The manufacturing method of the present invention includes a step of forming a first metal electrode layer on a substrate, a p-type or n-type organic semiconductor thin film on the first metal electrode layer, and an organic semiconductor thin film having a conductivity type opposite thereto. Forming a pn junction layer formed by laminating layers, forming a second metal electrode layer on the pn junction layer, and forming the laminate formed by these steps in a direction perpendicular to the film surface And forming the light irradiation surface, and the organic photovoltaic device of the present invention can be manufactured by a combination of existing techniques.
The step of forming the pn junction layer is a step of forming a metal layer and a pn junction layer thereon after laminating a p-type or n-type organic semiconductor thin film and an organic semiconductor thin film of the opposite conductivity type. If at least one of them is included, a pn junction series connection structure can be formed.
On the second metal electrode layer, at least at the position where the laminate on the resin substrate is cut, a protection layer covering the laminate is formed so as to cover a wider area than the laminate. It is possible to effectively prevent the interface between the electrode and the organic semiconductor layer from peeling when the laminate is cut by the layer.
If at least one of the p-type organic semiconductor thin film and the n-type organic semiconductor thin film includes a step of laminating different types of organic semiconductor thin films, the quantum efficiency for generating a photocurrent can be further improved, or most of the solar spectrum can be obtained. Alternatively, a solar battery cell that can absorb the entire wavelength region and generate a photocurrent can be created.
[Brief description of the drawings]
FIG. 1 is a perspective view schematically showing the structure of a vertical junction organic photovoltaic battery cell of one embodiment having one pn junction.
2 is a perspective view showing a structure of a solar battery cell in which a large number of pn junctions are connected by further developing the cell structure of FIG. 1. FIG.
FIG. 3 is an SEM image of a joining end face.
FIG. 4 is a plan view showing a pattern of a metal electrode and an organic semiconductor layer.
FIG. 5 is a current-voltage (IV) characteristic of a vertical junction type organic photovoltaic cell having one vertical pn junction.
FIG. 6 shows the wavelength dependence (black square plot) of the short-circuit photocurrent (Jsc) with Me-PTC and H ₂ It is a figure shown with the absorption spectrum (dotted line) of Pc.
FIG. 7 is a chemical structural formula showing main organic semiconductors.
FIG. 8 is a diagram showing an absorption spectrum of the organic semiconductor shown in FIG.
FIG. 9 is a diagram showing the principle of optical carrier generation by a multistage energy structure.
FIG. 10 is a diagram showing a quantum light condensing effect.
FIG. 11 is a diagram showing a lens system for increasing the area by connecting a light irradiation end face of a solar battery cell of one embodiment to a cylindrical lens array.
12 is a chemical formula showing some examples of resins used for dispersing an organic semiconductor when the organic semiconductor layer is a resin-dispersed organic semiconductor film in the present invention. FIG.
FIG. 13 is a schematic cross-sectional view showing a conventional ordinary organic photovoltaic device having a pn junction arranged in parallel to the light irradiation surface.
[Explanation of symbols]
12 p-type organic semiconductor layer
14 n-type organic semiconductor layer
12a, 14a Light irradiation surface
15 pn junction
16, 18 electrodes

Claims (10)

A pn junction composed of a p-type organic semiconductor layer and an n-type organic semiconductor layer is provided as a photovoltaic layer between a pair of metal electrodes, and the pn junction has an edge on the light irradiation surface and is opposite to the light irradiation surface. A vertically-junction organic photovoltaic device characterized by being formed in a vertical direction. 2. The vertical junction organic photovoltaic device according to claim 1, comprising a plurality of the pn junctions, wherein the pn junctions are stacked via a metal layer so as to be parallel to each other. 3. The p-type organic semiconductor layer is selected from the group consisting of phthalocyanines and quinacridone, and the n-type organic semiconductor layer is selected from the group consisting of perylene derivatives, naphthalene derivatives and fullerenes. The vertical junction organic photovoltaic device as described. The material of the metal electrode is selected so that a work function of an electrode in contact with a p-type organic semiconductor is large and a work function of an electrode in contact with an n-type organic semiconductor is small. The vertical junction organic photovoltaic device as described. 5. At least one of the p-type organic semiconductor layer and the n-type organic semiconductor layer is a stacked body in which organic semiconductor layers having different band structures are stacked so as to form a step energy structure. Vertical junction type organic photovoltaic device. 5. The vertical junction organic photovoltaic according to claim 1, wherein at least one of the p-type organic semiconductor layer and the n-type organic semiconductor layer is a laminate in which organic semiconductor layers having different light absorption characteristics are laminated. Power equipment. Forming a first metal electrode layer on the substrate;
Forming a pn junction layer by laminating a p-type or n-type organic semiconductor thin film and an organic semiconductor thin film of the opposite conductivity type on the first metal electrode layer;
Forming a second metal electrode layer on the pn junction layer;
Cutting the laminate formed by these steps in a direction perpendicular to the film surface to form a light irradiation surface;
A method of manufacturing a vertical junction organic photovoltaic device, comprising: The step of forming the pn junction layer includes forming a metal layer and a pn junction layer thereon after laminating a p-type or n-type organic semiconductor thin film and an organic semiconductor thin film of the opposite conductivity type. The method for producing a vertical junction organic photovoltaic device according to claim 7, comprising at least one step. The method further comprises a step of forming a protective layer covering the multilayer body on the second metal electrode layer so as to cover an area wider than the multilayer body at least at a position where the multilayer body is cut. The manufacturing method of the perpendicular | vertical junction type organic photovoltaic apparatus as described in any one of. 10. The vertical junction organic photovoltaic device according to claim 7, wherein at least one of the p-type organic semiconductor thin film and the n-type organic semiconductor thin film includes a step of laminating different types of organic semiconductor thin films. Production method.

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