U.S. patent application number 15/079562 was filed with the patent office on 2016-10-06 for photoelectric conversion device and method of manufacturing the same.
This patent application is currently assigned to Kabushiki Kaisha Toshiba. The applicant listed for this patent is Kabushiki Kaisha Toshiba. Invention is credited to Takeshi GOTANDA, Atsuko llDA, Hideyuki NAKAO, Haruhi OOOKA, Kenji TODORI.
Application Number | 20160293874 15/079562 |
Document ID | / |
Family ID | 57017480 |
Filed Date | 2016-10-06 |
United States Patent
Application |
20160293874 |
Kind Code |
A1 |
OOOKA; Haruhi ; et
al. |
October 6, 2016 |
PHOTOELECTRIC CONVERSION DEVICE AND METHOD OF MANUFACTURING THE
SAME
Abstract
A method of manufacturing a photoelectric conversion device of
an embodiment includes: forming a layer on a substrate; and drying
this layer. The layer contains a p-type semiconductor, an n-type
semiconductor, and a compound represented by the following formula
(1). The layer is dried under pressures of 100 Pa or less and
substrate temperatures of 40 to 200.degree. C.
R.sup.1--(CH.sub.2).sub.n--R.sup.2 (1) Here, n: 1 to 20, and R1,
R2: halogen or SH
Inventors: |
OOOKA; Haruhi; (Kawasaki,
JP) ; llDA; Atsuko; (Yokohama, JP) ; NAKAO;
Hideyuki; (Setagaya, JP) ; TODORI; Kenji;
(Yokohama, JP) ; GOTANDA; Takeshi; (Yokohama,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kabushiki Kaisha Toshiba |
Minato-ku |
|
JP |
|
|
Assignee: |
Kabushiki Kaisha Toshiba
Minato-ku
JP
|
Family ID: |
57017480 |
Appl. No.: |
15/079562 |
Filed: |
March 24, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 51/0007 20130101;
H01L 51/0036 20130101; H01L 2251/308 20130101; Y02P 70/521
20151101; H01L 51/0043 20130101; H01L 51/4253 20130101; Y02E 10/549
20130101; H01L 51/0046 20130101; Y02P 70/50 20151101; H01L 51/0026
20130101 |
International
Class: |
H01L 51/42 20060101
H01L051/42; H01L 51/00 20060101 H01L051/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 30, 2015 |
JP |
2015-068300 |
Claims
1. A method of manufacturing a photoelectric conversion device,
comprising: forming a layer containing a p-type semiconductor, an
n-type semiconductor, and a compound represented by the following
formula (1) on a substrate; and drying the layer under pressures of
100 Pa or less and substrate temperatures of 40 to 200.degree. C.
R.sup.1--(CH.sub.2).sub.n--R.sup.2 (1) n: 1 to 20 R1, R2: halogen
or SH
2. The method of claim 1, wherein the pressures are
1.times.10.sup.-3 Pa or less and the temperatures are 40 to
160.degree. C.
3. The method of claim 1, wherein: the dried layer has a
microphase-separated structure of the p-type semiconductor and the
n-type semiconductor; the p-type semiconductor has a polymer; and
the n-type semiconductor has a fullerene derivative.
4. The method of claim 1, wherein the compound is
1,8-diiodooctane.
5. A photoelectric conversion device, comprising: a first electrode
layer; a second electrode layer; and a photoelectric conversion
layer disposed between the first and second electrode layers and
including an organic active layer, the organic active layer
containing a p-type semiconductor, an n-type semiconductor, and a
compound represented by the following formula (1), and a
concentration of the compound being 0.001 mass % or more to less
than 0.1 mass %. R.sup.1--(CH.sub.2).sub.n--R.sup.2 (1) n: 1 to 20
R1, R2: halogen or SH
6. The photoelectric conversion device of claim 5, wherein the
photoelectric conversion layer has a microphase-separated structure
of the p-type semiconductor and the n-type semiconductor, the
p-type semiconductor has a polymer; and the n-type semiconductor
has a fullerene derivative.
7. The photoelectric conversion device of claim 5, wherein the
compound is 1,8-diiodooctane.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is based upon and claims the benefit of
priority from Japanese Patent Application No. 2015-068300, filed on
Mar. 30, 2015; the entire contents of all of which are incorporated
herein by reference.
FIELD
[0002] Embodiments described herein relate generally to a
photoelectric conversion device and a method of manufacturing the
same.
BACKGROUND
[0003] In recent years, an organic photovoltaic cell having an
organic semiconductor film has been examined due to simplification
of a manufacturing process. Since an organic semiconductor thin
film can be formed by a coating method, simplification of a process
of manufacturing a photovoltaic cell and a reduction in power
generation cost are expected.
[0004] There has been known an organic photovoltaic cell having a
bulk hetero junction type photoelectric conversion active layer. In
the bulk hetero junction type photoelectric conversion active
layer, an electron donating organic semiconductor (p-type organic
semiconductor) and an electron accepting organic semiconductor
(n-type organic semiconductor) are mixed, so that the bulk hetero
junction type photoelectric conversion active layer has a large
area of a pn junction interface where charge separation occurs.
[0005] When the bulk hetero junction type photoelectric conversion
active layer is formed by a coating method, a coating solution
containing a p-type organic semiconductor, an n-type organic
semiconductor, and a solvent is used as a main component. In order
to form a photoelectric conversion active layer excellent in power
conversion efficiency, an alkane compound whose end is
halogen-substituted (for example, 1,8-diiodooctane) is added to the
coating solution.
[0006] In many cases, power conversion efficiency of a photovoltaic
cell decreases as the photovoltaic cell is used. That is, the
photovoltaic cell which power conversion efficiency significantly
decreases during use is far to be practical, even though its power
conversion efficiency is high immediately after manufacture.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a cross-sectional view illustrating a
photoelectric conversion device of an embodiment.
[0008] FIG. 2 is an external view explaining a coating method by a
meniscus coating method.
[0009] FIG. 3 is a view explaining a method of supplying a coating
solution in the meniscus coating method.
[0010] FIG. 4 is an enlarged view explaining the coating method by
the meniscus coating method.
DETAILED DESCRIPTION
[0011] A method of manufacturing a photoelectric conversion device
of an embodiment includes: forming a layer on a substrate; and
drying this layer. The layer contains a p-type semiconductor, an
n-type semiconductor, and a compound represented by the following
formula (1). The layer is dried under pressures of 100 Pa or less
and substrate temperatures of 40 to 200.degree. C.
R.sup.1--(CH.sub.2).sub.n--R.sup.2 (1)
[0012] Here, n: 1 to 20, R1, R2: halogen or SH
[0013] Hereinafter, there will be explained modes for carrying out
the present invention. First, there will be explained a
photoelectric conversion device of an embodiment.
[0014] FIG. 1 is a cross-sectional view illustrating an organic
photovoltaic cell (organic solar cell) as the photoelectric
conversion device of the embodiment.
[0015] An organic photovoltaic cell 10 includes a supporting
substrate 11. On the supporting substrate 11, a pair of first
electrode layers 12 is disposed. On the first electrode layer 12 on
the right of the drawing, a photoelectric conversion layer 13 is
disposed. On the photoelectric conversion layer 13, a second
electrode layer 14 is disposed. The second electrode layer 14 is
electrically connected to the first electrode layer 12 on the left
of the drawing. Further, on the supporting substrate 11, a sealing
substrate 18 is disposed. The sealing substrate 18 covers the
photoelectric conversion layer 13 and the second electrode layer
14, and is fixed on the supporting substrate 11 by an adhesive
layer 19.
[0016] The photoelectric conversion layer 13 includes: a first
intermediate layer 15; an organic active layer 16 as a
photoelectric conversion active layer; and a second intermediate
layer 17 in the order from the first electrode layer 12. The
organic active layer 16 contains a p-type semiconductor, an n-type
semiconductor, and a compound represented by the following formula
(1).
R.sup.1--(CH.sub.2).sub.n--R.sup.2 (1)
[0017] Here,
[0018] n: 1 to 20
[0019] R1, R2: halogen (fluorine (F), chlorine (Cl), bromine (Br),
or iodine (I)) or SH
[0020] Light such as sunlight or illumination light is emitted to
the photoelectric conversion layer 13 from the supporting substrate
11, for example. The light emitted to the photoelectric conversion
layer 13 is absorbed by the organic active layer 16. This causes
charge separation at a phase interface between the p-type
semiconductor and the n-type semiconductor to generate an electron
and its paired hole. Out of electrons and holes generated in the
organic active layer 16, the electrons are collected in the first
electrode layer 12 and the holes are collected in the second
electrode layer 14, for example.
[0021] In the case when light is emitted from the supporting
substrate 11, the supporting substrate 11 is constituted of a
material having a light transmission property. As a constituent
material of the supporting substrate 11, an inorganic material or
an organic material can be used. Examples of the inorganic material
are non-alkali glass, quartz glass, and sapphire. Examples of the
organic material are polyethylene, polyethylene terephthalate
(PET), polyethylene naphthalate (PEN), polyimide, polyamide,
polyamide-imide, and a liquid crystal polymer.
[0022] In the case when light is emitted from the supporting
substrate 11, the first electrode layer 12 is constituted of a
material having a light transmission property and conductivity. As
a constituent material of the first electrode layer 12, there can
be used a conductive metal oxide, a metal, and a conductive
polymer. Examples of the conductive metal oxide are an indium
oxide, a zinc oxide, a tin oxide, an indium tin oxide (ITO), a
fluorine-doped tin oxide (FTO), an indium-zinc oxide (IZO), and an
indium-gallium-zinc oxide (IGZO). Examples of the metal are gold,
platinum, silver, copper, titanium, zirconium, cobalt, nickel,
indium, and aluminum, and an alloy containing these metals.
Examples of the conductive polymer are poly
(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonic acid)
(PEDOT/PSS). The first electrode layer 12 can be formed by, for
example, a vacuum deposition method, a sputtering method, an ion
plating method, a plating method, a coating method, or the
like.
[0023] The organic active layer 16 has a function to perform charge
separation by the emitted light, and contains the p-type
semiconductor, the n-type semiconductor, and the compound
represented by the formula (1). For the p-type semiconductor, a
material having an electron donating property is used. For the
n-type semiconductor, a material having an electron accepting
property is used. One or both of the p-type semiconductor and the
n-type semiconductor constituting the organic active layer 16 may
be an organic material.
[0024] For the p-type semiconductor contained in the organic active
layer 16, there can be used one or a plurality of materials
selected from among polythiophene and its derivative, polypyrrole
and its derivative, a pyrazoline derivative, an arylamine
derivative, a stilbene derivative, a triphenyldiamine derivative,
oligothiophene and its derivative, polyvinyl carbazole and its
derivative, polysilane and its derivative, a polysiloxane
derivative having aromatic amine at a side chain or a main chain,
polyaniline and its derivative, a phthalocyanine derivative,
porphyrin and its derivative, polyphenylene vinylene and its
derivative, and polythienylene vinylene and its derivative.
[0025] As the n-type semiconductor contained in the organic active
layer 16, fullerene or a fullerene derivative is preferably used.
Examples of the fullerene are C.sub.60, C.sub.70, C.sub.76,
C.sub.78, and C.sub.84. The fullerene derivative may be any,
provided that it has a fullerene framework. Examples of the
fullerene derivative are a fullerene oxide being any of these
fullerenes whose carbon atoms at least partly are oxidized, a
compound in which part of carbon atoms of a fullerene framework is
modified by optional functional groups, and a compound in which
these functional groups are bonded to form a ring.
[0026] As the compound represented by the formula (1), which is
contained in the organic active layer 16, n is preferable to be 2
to 13, and n is more preferable to be 5 to 10 from a viewpoint of
the power conversion efficiency. Examples of the compound
represented by the formula (1) are octanedithiol, dibromooctane,
diiodooctane, diiodohexane, and diiodobutane. Only one kind of
these may be used, or two or more kinds of these may also be mixed
to be used. Among these, the octanedithiol, the dibromooctane, and
the diiodooctane are preferable from a viewpoint of the power
conversion efficiency.
[0027] The concentration of the compound represented by the formula
(1) in the organic active layer 16 is less than 0.1 mass %. When
the concentration is less than 0.1 mass %, a decrease in the power
conversion efficiency during use is suppressed. From a viewpoint of
suppressing a decrease in the power conversion efficiency during
use, the concentration of the compound represented by the formula
(1) is preferable to be 0.095 mass % or less and more preferable to
be 0.09 mass % or less. Here, the concentration of the compound
represented by the formula (1) can be adjusted, as will be
described later, by drying conditions such as a pressure and a
temperature at which the organic active layer 16 is formed.
[0028] Further, the concentration of the compound represented by
the formula (1) in the organic active layer 16 is 0.001 mass % or
more to less than 0.1 mass %. When the concentration becomes 0.001
mass % or more, the power conversion efficiency in an early stage,
namely the power conversion efficiency immediately after
manufacture increases. From a viewpoint of increasing the power
conversion efficiency in an early stage, the concentration is more
preferable to be 0.01 mass % or more. On the other hand, when the
concentration of the compound represented by the formula (1) is 0.1
mass % or more, the decrease in the power conversion efficiency
during use may become large.
[0029] The organic active layer 16 has a bulk hetero junction
structure containing a mixture of the p-type semiconductor and the
n-type semiconductor, for example. The bulk hetero junction type
organic active layer 16 has a microphase-separated structure of the
p-type semiconductor and the n-type semiconductor. A p-type
semiconductor phase and an n-type semiconductor phase are separated
from each other to form a pn junction on a nanometer order. When
the organic active layer 16 absorbs light, positive charges (holes)
and negative charges (electrons) are generated at an interface of
these phases and they are transported to the first electrode layer
12 and the second electrode layer 14 through the respective
semiconductors. A composition ratio of the p-type semiconductor to
the n-type semiconductor is preferable to be, in a mass ratio, the
p-type semiconductor: the n-type semiconductor=1 to 99: 99 to 1,
and more preferable to be 20 to 80: 80 to 20.
[0030] The thickness of the organic active layer 16 is normally
preferable to be 10 to 1000 nm and further preferable to be 50 to
500 nm. When the thickness of the organic active layer 16 becomes
10 nm or more, the p-type semiconductor and the n-type
semiconductor are mixed uniformly to be unlikely to cause a short
circuit. Further, when the thickness of the organic active layer 16
becomes 1000 nm or less, internal resistance becomes small and the
distance between the first electrode layer 12 and the second
electrode layer 14 becomes closer, so that charges are well
diffused. The organic active layer 16 can be suitably formed by
applying the coating solution containing the p-type semiconductor
and the n-type semiconductor.
[0031] The first intermediate layer 15 is provided as necessary.
For example, the first intermediate layer 15 functions as an
electron transport layer to block the hole generated in the organic
active layer 16 and to selectively and efficiently transport the
electron to the first electrode layer 12. The first intermediate
layer 15 can be constituted of a metal oxide or an organic
material. Examples of the metal oxide are a zinc oxide, a titanium
oxide, and a gallium oxide. Examples of the organic material are
polyethyleneimine.
[0032] The second intermediate layer 17 is provided as necessary.
For example, the second intermediate layer 17 functions as a hole
transport layer to block the electron generated in the organic
active layer 16 and to selectively and efficiently transport the
hole to the second electrode layer 14. The second intermediate
layer 17 can be constituted of an organic conductive polymer or a
metal oxide. Examples of the organic conductive polymer are
PEDOT/PSS, polythiophene, polypyrrole, polyacethylene,
triphenylenediaminepolypyrrole, and polyaniline. Examples of the
metal oxide are a molybdenum oxide and a vanadium oxide.
[0033] The first intermediate layer 15 and the second intermediate
layer 17 can be formed by a vacuum film-forming method such as a
vacuum deposition method or a sputtering method, a sol-gel method,
a coating method, or the like, for example.
[0034] The second electrode layer 14 is constituted of a material
that has conductivity and has a light transmission property in some
cases. As a constituent material of the second electrode layer 14,
it can be constituted of a metal, a conductive metal oxide, a
conductive polymer, or a carbon material. Examples of the metal are
platinum, gold, silver, copper, nickel, cobalt, iron, manganese,
tungsten, titanium, zirconium, tin, zinc, aluminum, indium,
chromium, lithium, sodium, potassium, rubidium, cesium, calcium,
magnesium, barium, samarium, terbium, and an alloy of these.
Examples of the conductive metal oxide are an indium-zinc oxide
(IZO). Examples of the conductive polymer are PEDOT/PSS. Examples
of the carbon material are graphene and a carbon nano tube. The
second electrode layer 14 can be formed by a vacuum film-forming
method such as a vacuum deposition method or a sputtering method, a
sol-gel method, a coating method, or the like, for example.
[0035] The sealing substrate 18 is for protecting the photoelectric
conversion layer 13 from moisture and the like and making the
photoelectric conversion layer 13 exhibit its characteristics for a
long time. The sealing substrate 18 may be either an inorganic
material or an organic material. Examples of the sealing substrate
18 are a metal substrate, a glass substrate, and a composite
substrate obtained by depositing a metal film on a resin film. When
light entering from the sealing substrate 18 side is used, a
material having a light transmitting property is used for the
sealing substrate 18.
[0036] Next, there will be explained a method of manufacturing the
photoelectric conversion device of the embodiment. The method of
manufacturing the photoelectric conversion device of the embodiment
is suitably used for manufacture of the organic active layer in
particular.
[0037] The method of manufacturing the photoelectric conversion
device of the embodiment includes a coating step and a drying step.
In the coating step, a coating solution containing a p-type
semiconductor, an n-type semiconductor, and a compound represented
by the following formula (1) is applied on a substrate. In the
drying step, the coating solution on the substrate is dried under a
condition that a pressure is 100 Pa or less and a temperature of
the substrate is 40 to 200.degree. C. Hereinafter, the respective
steps will be explained concretely.
R.sup.1--(CH.sub.2).sub.nR.sup.2 (1)
[0038] n: 1 to 20
[0039] R1, R2: halogen (fluorine (F), chlorine (Cl), bromine (Br),
or iodine (I)) or SH
[0040] In the coating step, the coating solution containing the
p-type semiconductor, the n-type semiconductor, and the compound
represented by the formula (1) is first prepared. The coating
solution can be prepared by adding the p-type semiconductor, the
n-type semiconductor, and the compound represented by the formula
(1) to a solvent and mixing the resultant mixture. Concrete
examples of the p-type semiconductor, the n-type semiconductor, and
the compound represented by the formula (1) have been already
explained, so that their explanations are omitted.
[0041] Examples of the solvent are tetrahydrofuran,
1,2-dichloroethane, cyclohexane, chloroform, bromoform, benzene,
toluene, o-xylene, chlorobenzene, bromobenzene, iodobenzene,
o-dichlorobenzene, anisole, methoxybenzene, trichlorobenzene, and
pyridine. These solvents may be used alone, or two kinds or more of
these may also be mixed to be used. Among these, the
o-dichlorobenzene, the chlorobenzene, the bromobenzene, the
iodobenzene, and the chloroform, which are high in solubility with
each of the p-type semiconductor and the n-type semiconductor, and
a mixture of these are preferable, and the o-dichlorobenzene, the
chlorobenzene, and a mixture of these are more preferable.
[0042] The total added amount of the p-type semiconductor and the
n-type semiconductor is preferable to be 0.5 mass % or more and
more preferable to be 0.9 mass % or more to 100 mass % of the
coating solution from viewpoints of a reduction in energy to be
consumed in the drying step of the solvent, speeding up of a drying
rate, and the like. Further, the total added amount of the p-type
semiconductor and the n-type semiconductor is preferable to be 4.2
mass % or less and more preferable to be 2.6 mass % or less to 100
mass % of the coating solution from viewpoints of solubility,
dispersibility, suppression of an increase in viscosity of the
coating solution, and the like.
[0043] The added amount of the compound represented by the formula
(1) is preferable to be 21.6 mass % or more and more preferable to
be 47.9 mass % or more to 100 mass % of the total of the p-type
semiconductor, the n-type semiconductor, and the compound
represented by the formula (1) from a viewpoint of increasing the
power conversion efficiency in an early stage, namely the power
conversion efficiency immediately after manufacture. Further, the
added amount of the compound represented by the formula (1) is
preferable to be 94.8 mass % or less and more preferable to be 90.2
mass % or less to 100 mass % of the total of the p-type
semiconductor, the n-type semiconductor, and the compound
represented by the formula (1) from a viewpoint of suppressing the
decrease in the power conversion efficiency during use, which is
caused by a residue.
[0044] The coating solution is applied on the substrate by using
various coating methods. As the substrate, the supporting substrate
having the first electrode layer in the organic photovoltaic cell
can be cited. Incidentally, the supporting substrate may have the
first intermediate layer in addition to the first electrode
layer.
[0045] As the coating method, a method that has been known until
now can be employed. For example, there can be employed a coating
method such as an immersion coating method, a spray coating method,
an ink jet method, an aerosol jet method, a spin coating method, a
bead coating method, a wire bar coating method, a blade coating
method, a roller coating method, a curtain coating method, a slit
die coater method, a gravure coater method, a slit reverse coater
method, a microgravure method, a comma coater method, or a meniscus
coating method. Among these, the coating is preferably performed by
the meniscus coating method.
[0046] FIG. 2 to FIG. 4 are views each explaining the coating
method of the coating solution by the meniscus coating method.
[0047] In the meniscus coating method, a meniscus coating apparatus
20 illustrated in FIG. 2 is used. The meniscus coating apparatus 20
has a plate-shaped stage 21 and a column-shaped coating head 22
that is disposed to face this stage 21, for example. The position
of the coating head 22 is fixed. The stage 21 is movable
horizontally with respect to the coating head 22.
[0048] The substrate as a coating object 23 is disposed on the
stage 21. Here, as the substrate being the coating object 23, the
supporting substrate in the organic photovoltaic cell on which the
first electrode layer is disposed, or the supporting substrate on
which the first electrode layer and the first intermediate layer
are disposed can be cited.
[0049] As illustrated in FIG. 3, a coating solution 25 is supplied
to the coating head 22 from a supply device 24 so as to spread over
the entire region in a width direction of the coating head 22.
Then, as illustrated in FIG. 4, the stage 21 is moved horizontally
in a state where the position of the coating head 22 is fixed.
Thereby, the coating object 23 disposed on the stage 21 is moved
with respect to the coating head 22. As a result, the coating
solution 25 is spread by the coating head 22 to coat the coating
object 23. Incidentally, the coating head 22 is normally used in an
irrotational state.
[0050] In the drying step, the coating solution coated on the
substrate is dried under the condition that the pressure is 100 pa
or less and the temperature of the substrate is 40 to 200.degree.
C.
[0051] Heating is performed so that the temperature of the
substrate becomes 40.degree. C. or more, and thereby a binding
force of the p-type semiconductor and the n-type semiconductor to
the compound represented by the formula (1) decreases to make the
compound represented by the formula (1) likely to be removed from
the coating solution (coated film) on the substrate. This makes the
concentration of the compound represented by the formula (1) in the
organic active layer become less than 0.1 mass %. From a viewpoint
of removing the compound represented by the formula (1), the
heating is preferably performed so that the temperature of the
substrate becomes 45.degree. C. or more.
[0052] Incidentally, when the temperature of the substrate exceeds
200.degree. C., the microphase-separated structure of the p-type
semiconductor and the n-type semiconductor, namely, the bulk hetero
structure deteriorates or the materials of the p-type semiconductor
and the n-type semiconductor deteriorate, resulting in a decrease
in the power conversion efficiency. Therefore, the heating is
performed so that the temperature of the substrate becomes
200.degree. C. or less. The heating is preferably performed so that
the temperature of the substrate becomes 160.degree. C. or less,
and the heating is more preferably performed so that the
temperature of the substrate becomes 100.degree. C. or less.
[0053] Further, reducing the pressure to 100 Pa or less enables the
compound represented by the formula (1) to be removed from the
coating solution (coated film) on the substrate sufficiently, in
combination with the fact that the heating makes the compound
represented by the formula (1) likely to be removed. From a
viewpoint of removing the compound represented by the formula (1),
the pressure is preferable to be 1 Pa or less and more preferable
to be 1.times.10.sup.-3 Pa or less. Incidentally, even if the
pressure is lowered more, it is sufficient to lower the pressure
down to 1.times.10.sup.-4 Pa. As the pressure becomes lower, the
compound represented by the formula (1) becomes more likely to be
removed, but there is a limit in terms of it. On the other hand,
time for reducing the pressure becomes long.
[0054] For the pressure reduction, a rotary pump, a turbopump, a
cryopump, and the like can be used. For example, after the pressure
is roughly reduced by the rotary pump, the pressure is fully
reduced by the turbopump and the cryopump, resulting in that the
pressure can be reduced efficiently. Using the turbopump or the
cryopump makes it possible to reduce the pressure to
1.times.10.sup.-4 Pa or less.
[0055] The time for the drying step, namely the time during which
the above-described temperature condition and pressure condition
are satisfied simultaneously is preferable to be 1 minute or more
and more preferable to be 10 minutes or more from a viewpoint of
removing the compound represented by the formula (1). On the other
hand, from viewpoints of suppressing a decrease in productivity and
a decrease in the power conversion efficiency to be caused by
deterioration of the p-type semiconductor and the n-type
semiconductor, the time for the drying step is preferable to be 180
minutes or less and more preferable to be 60 minutes or less.
EXAMPLES
[0056] Hereinafter, the present invention will be concretely
explained with reference to examples. Incidentally, the present
invention is not limited to these examples.
Example 1
[0057] A coating solution to be used for formation of the organic
active layer is prepared as follows. To 1.94 ml of
monochlorobenzene as the solvent, 0.06 ml of 1,8-diiodooctane as
the compound represented by the formula (1), 16 mg of PTB7
([poly{4,8-bis[(2-ethylhexyl)oxy]benz[1,2-b:
4,5-b']dithiophene-2,6-diyl-lt-alt-3-fluoro-2-[(2-ethylhexyl)carbonyl]thi-
eno[3,4-b]thiophene-4,6-diyl}]) being a polymer as the p-type
semiconductor, and 24 mg of PC70BM ([6,6]phenylC71butyric acid
methylester) being a fullerene derivative as the n-type
semiconductor are added. This mixed solution is stirred and
dispersed for 20 minutes at 80.degree. C., and then the temperature
returns to room temperature and the resultant mixed solution is
prepared as the coating solution to be used for formation of the
organic active layer.
[0058] Besides, one obtained by providing an ITO film as the first
electrode layer on a non-alkali glass plate as the supporting
substrate is prepared, and is cleaned by UV ozone as a
pretreatment. Next, as the first intermediate layer, a PEW
(polyethyleneimineethoxylate) film having a thickness of about 1 nm
is formed. Here, there is used PEW in which 80% of amine is
denatured into ethoxylate. Hereinafter, the non-alkali glass plate
having the ITO film and the PETE is described as an object
substrate.
[0059] Next, on the stage 21 in the meniscus coating apparatus 20
illustrated in FIG. 2, the above-described object substrate as the
coating object 23 is disposed. Further, the coating head 22 is
disposed above this object substrate being the coating object 23 to
have a gap of 0.88 mm therebetween.
[0060] Thereafter, as illustrated in FIG. 3, by using the supply
device 24, the coating solution 25 is supplied so as to spread over
the entire region in the width direction of the coating head 22.
Then, as illustrated in FIG. 4, the stage 21 is moved horizontally
at a 10 mm/s speed in a state where the position of the coating
head 22 is fixed, and the coating solution 25 is applied on the
object substrate being the coating object 23.
[0061] Next, this object substrate having the coating solution
(coated film) is put in a vacuum deposition machine, and by using a
rotary pump, the pressure is lowered to 60 Pa for 20 minutes.
Further, by using a cryopump, the pressure is lowered to
5.times.10.sup.-5 Pa for 15 minutes. In this state, heating is
performed for 10 minutes until the temperature of the object
substrate becomes 47.degree. C. from 25.degree. C., and further
maintaining at this temperature is performed for 1 minute. Thereby,
the coated film is dried and the organic active layer is formed.
The thickness of the organic active layer is about 90 nm.
Incidentally, the pressure is confirmed using an ion gauge.
Further, the temperature of the object substrate is confirmed using
a thermocouple.
[0062] This object substrate having the organic active layer is
taken out of the vacuum deposition machine, and a deposition mask
is set on this object substrate to be put in the vacuum deposition
machine again. Thereafter, as the second intermediate layer, a
V.sub.2O.sub.5 film having a thickness of about 10 nm, and as the
second electrode layer, an Ag film having a thickness of about 100
nm are deposited sequentially. After the deposition, the substrate
is taken out of the vacuum deposition machine.
[0063] Besides, as the sealing substrate, a glass having a recessed
portion in its center portion, namely a counterbored glass is
prepared. A desiccant is applied to a counterbored portion (the
recessed portion) of this counterbored glass, and an UV curing
epoxy adhesive to be an adhesive layer is applied to a surrounding
non-counterbored portion. This sealing substrate is laminated on
the object substrate having the organic active layer, and an
organic photovoltaic cell is manufactured.
[0064] When, of this organic photovoltaic cell, power conversion
efficiency immediately after manufacture (power conversion
efficiency in early stage in the table) is measured, it is 6.50%.
Further, when the power conversion efficiency of the organic
photovoltaic cell after a dry heat test at 85.degree. C., for 1000
hours, and under a nitrogen atmosphere (power conversion efficiency
after test in the table) is measured, it is 6.25%. Further, when a
decrease rate of the power conversion efficiency after the dry heat
test is found from these measurement results, it is 3.8%.
Incidentally, the power conversion efficiency is measured by using
a solar simulator with a reference spectrum of 100 mW/cm.sup.2
irradiance and AM 1.5 G.
[0065] Besides, as for the organic photovoltaic cell immediately
after manufacture, namely the organic photovoltaic cell that is not
subjected to a dry heat test, the concentration of 1,8-diiodooctane
in the organic active layer is measured as follows. First, after
the counterbored glass being the sealing substrate is removed, the
V.sub.2O.sub.5 film being the second intermediate layer and the Ag
film being the second electrode layer are removed by etching to
expose the organic active layer. Thereafter, an XPS (X-ray
Photoelectron Spectroscopy) analysis and etching of the organic
active layer are repeatedly performed alternately and the
concentration of 1,8-diiodooctane in the organic active layer in
mol % is measured in the entire region in a thickness direction.
The concentrations in mol % in this thickness direction are
averaged to be further converted into a concentration in mass %.
Incidentally, the detection limit of the 1,8-diiodooctane by the
XPS analysis is considered to be 0.001 mass %.
Example 2
[0066] A substrate having a coated film is manufactured in the same
manner as in Example 1. Thereafter, the pressure is lowered to 15
Pa in 20 minutes, and then heating is performed at 15 Pa for 10
minutes until the temperature of an object substrate becomes
46.degree. C., and further maintaining at this temperature is
performed at 15 Pa for 1 minute, and an organic active layer is
formed. Incidentally, the thickness of the organic active layer is
set to the same as that in Example 1. Thereafter, manufacture and
evaluation of an organic photovoltaic cell are performed in the
same manner as in Example 1.
Example 3
[0067] A substrate having a coated film is manufactured in the same
manner as in Example 1. Thereafter, the pressure is lowered to 15
Pa in 20 minutes, and then heating is performed at 15 Pa for 10
minutes until the temperature of an object substrate becomes
150.degree. C., and further maintaining at this temperature is
performed at 15 Pa for 1 minute, and an organic active layer is
formed. Incidentally, the thickness of the organic active layer is
set to the same as that in Example 1. Thereafter, manufacture and
evaluation of an organic photovoltaic cell are performed in the
same manner as in Example 1.
Comparative Example 1
[0068] A substrate having a coated film is manufactured in the same
manner as in Example 1. Thereafter, at normal pressure, heating is
performed for 20 seconds until the temperature of an object
substrate becomes 70.degree. C., and further maintaining at this
temperature is performed for 30 minutes, and an organic active
layer is formed. Incidentally, the thickness of the organic active
layer is set to the same as that in Example 1. Thereafter,
manufacture and evaluation of an organic photovoltaic cell are
performed in the same manner as in Example 1.
Comparative Example 2
[0069] A substrate having a coated film is manufactured in the same
manner as in Example 1. Thereafter, the pressure is lowered to
5.times.10.sup.-5 Pain the same manner as in Example 1, and then
heating is performed for 10 minutes until the temperature of an
object substrate becomes 30.degree. C., and further maintaining at
this temperature is performed for 1 minute, and an organic active
layer is formed. Incidentally, the thickness of the organic active
layer is set to the same as that in Example 1. Thereafter,
manufacture and evaluation of an organic photovoltaic cell are
performed in the same manner as in Example 1.
Comparative Example 3
[0070] A substrate having a coated film is manufactured in the same
manner as in Example 1. Thereafter, the pressure is lowered to 15
Pa for 20 minutes, and then heating is performed for 10 minutes
until the temperature of an object substrate becomes 39.degree. C.,
and further maintaining at this temperature is performed for 1
minute, and an organic active layer is formed. Incidentally, the
thickness of the organic active layer is set to the same as that in
Example 1. Thereafter, manufacture and evaluation of an organic
photovoltaic cell are performed in the same manner as in Example
1.
TABLE-US-00001 TABLE 1 Power conversion efficiency Concentration
Early stage After test Decrease rate Pressure Temperature [mass %]
[%] [%] [%] Example 1 5 .times. 10.sup.-5 Pa 47.degree. C. 0.08
6.50 6.25 3.8 Example 2 15 Pa 46.degree. C. 0.09 6.12 5.82 4.9
Example 3 15 Pa 150.degree. C. 0.05 2.40 2.29 4.6 Comparative
Normal pressure 70.degree. C. 5.28 6.72 4.37 35.0 Example 1
Comparative 5 .times. 10.sup.-5 Pa 30.degree. C. 8.70 6.71 5.17
23.0 Example 2 Comparative 15 Pa 39.degree. C. 0.12 6.44 5.83 9.5
Example 3
[0071] As is clear from Table 1, in Examples 1 to 3 in which the
coated film is dried under the condition that the pressure is 100
Pa or less and the temperature of the substrate is 40 to
200.degree. C., the decrease rate of the power conversion
efficiency after the dry heat test becomes 5% or less. In Example 1
in particular, the power conversion efficiency in an early stage is
high and the decrease rate of the power conversion efficiency after
the dry heat test is small.
[0072] Further, in Examples 1 to 3 in which the concentration of
1,8-diiodooctane in the organic active layer is less than 0.1 mass
%, the decrease rate of the power conversion efficiency after the
dry heat test becomes 5% or less. Here, requirements of 10.13 damp
heat test in JIS C8990 "Crystalline silicon terrestrial
photovoltaic (PV) modules-Design qualification and type approval"
include one in which the decrease rate at 85.degree. C. and 85% RH
and for 1000 h is 5% or less. According to the above, it is greatly
significant also in the organic photovoltaic cell that the decrease
rate at a dry heat test at 85.degree. C. and for 1000 h is 5% or
less.
[0073] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of the inventions. Indeed, the novel
embodiments described herein may be embodied in a variety of other
forms; furthermore, various omissions, substitutions and changes in
the form of the embodiments described herein may be made without
departing from the spirit of the inventions. The inventions
described in the accompanying claims and their equivalents are
intended to cover such forms or modifications as would fall within
the scope and spirit of the inventions.
* * * * *