JPH01154571A - Photoelectric converter - Google Patents

Abstract

PURPOSE:To obtain a photoelectric converter which can be easily manufactured inexpensively with large area and high conversion efficiency with flexibility by incorporating specific phenylene compound in an optically active layer. CONSTITUTION:A photoelectric converter is composed, for example, of a structure in which a photoconductive organic semiconductor and an optically active layer 2 including a compound represented by a formula I are sandwiched between a front electrode 1 and a back electrode 4. Since light is incident from the electrode 1, the front electrode becomes a light transmittive. Both the front and back electrodes may be solely employed, or may be provided with a support or protective layer. The electrodes 1, 4 are connected by leads or the like to an external circuit to be employed in a practical use. This optically active layer 3 may be of a layer for generating a charge by the light similarly to the layer 2 or may be of a layer permitting efficient movement of charge generated from the layer 2. R1, R2, R3, R4 in the formula I are hydrogen, substituted or nonsubstituted aryl, and the R1, the R2, and the R3, the R4 may form a ring.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a photoelectric conversion element (organic solar cell) using an organic photoconductor, and is applied to optical sensors, image sensors, etc.

[Prior Art] Many attempts have been made to produce photoelectric conversion elements using inorganic semiconductors. The goal is a) high conversion rate and b)
It is a low-priced photoelectric conversion element.

Medium crystalline Si, polycrystalline S tSCdS, CdTe.

Attempts have been made to put GaAs, amorphous Si, etc. to practical use, but it is hard to say that all of these satisfy the criterion b) (1).

In order to improve this drawback, attempts have been made in recent years to fabricate photoelectric conversion elements using organic semiconductors. Examples of the organic semiconductor layers used are as follows.

(a) Merocyanine dye layer coated with a spinner (JP-A-51-122389, JP-A-53-131782, and "Journal, Off. Applied, Phys. Ap
pl, Phys, ) J 49.5982.1978) (
b) Laminated layer of phthalocyanine vapor layer or electron donor layer such as obalene and electron acceptor layer such as pyrylium dye (JP-A-54-27787, JP-A-60-201672)
and R, O, Loutfu-r (R, O, Lout
[Journal of Applied Physics J, Appl.

Phys,) J 52.5218.1981) (c)
Eutectic complex layer formed from pyrylium dye and polycarbonate (JP-A-54-27387) (d) Layer in which metal-free phthalocyanine is dispersed in a binder (JP-A-55-9)
497) (e) Laminated layer of n-type silicon and p-type doped polyacetylene thin film (JP-A-55-1301, 82,
Japanese Patent Publication No. 55-138879 and Applied Physics 9 Letter by B. R. Weinnberger (Appl, Phys,
Lett,) 3g, 555.1981) (to) Vacuum pale blue merocyanine dye layer (JP-A-56-35477
) These can be produced by applying a solution of these organic semiconductors alone or together with a suitable binder dissolved or dispersed in a medium onto a substrate, or by vacuum-depositing them at low temperatures, and then providing another conductive layer thereon. Although a large-area product can be obtained at low cost, the conversion efficiency was too low to be put to practical use.

[11] The present invention has been made to solve the above-mentioned conventional drawbacks, and is inexpensive, easy to manufacture in a large area, flexible, and using organic materials. The present invention aims to provide a photoelectric conversion element that has high conversion efficiency and is more suitable for the spectral distribution of sunlight and indoor light than conventional ones.

[Mizosei] In order to achieve the above object, the present invention provides an organic semiconductor capable of generating optical carriers in the visible light region, or when used alone or together with a suitable binder [said (a) to (a).
As a result of intensive research to improve the drawbacks of This is based on the discovery that by containing , the photocurrent increases significantly and, as a result, the photoelectric conversion efficiency increases.

General formula However, in the above general formula, R1, R2, R3, R4
are hydrogen, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, and R1 and R2 and R3 and R4
may form a ring.

In the photoelectric conversion element of the present invention, for example, the photoactive layer (1) containing a photoconductive semiconductor and the above-mentioned compound has two electric charges. il
i! (front electrode, back electrode).

Since light enters from the front electrode side, the front electrode is transparent.

Both the front and back electrodes may be used alone or may be provided with a support or a protective layer. Examples of these are shown in FIGS. 1-3.

The front electrode and the back electrode are connected to an external circuit through lead wires, etc., and used for actual use.

The photoactive layer need not be a single layer; examples of two layers are shown in FIGS. 1-3(b), respectively. This photoactive layer (II) may be a layer that generates charges by light like the photoactive layer (1), or may be a layer that efficiently transfers the charges generated in the photoactive layer (I). In the example of FIG. 1(b), the photoactive layer (I) is drawn on the front electrode side, but it goes without saying that the photoactive layer (II) may be on the front electrode side. The photoactive layer (I) may also be a multilayer consisting of different photoconductive organic materials.

The present invention relates to the photoactive layer (I).

The photoactive layer (1) is a layer in which light (11) is emitted and generates holes and electrons.For this purpose, it is necessary that an electric field exists within the layer, and this is caused by the presence of an electric field between the front electrode and the back electrode. an external voltage is applied between them, or metals with different work functions are used for the front and back electrodes, or the photoactive layer (1) is bonded to the front or back electrode or the photoactive layer (n). Sometimes, due to the difference in their Fermi levels (or work functions), heat carriers move and a junction barrier is formed, which can be achieved without an external voltage.

The photoactive layer (I) is a layer containing a phenylenediamine compound represented by the general formula (A).

This layer contains, as another essential component, a photoconductive organic semiconductor that absorbs visible light. It may also contain a suitable binder if necessary.

We believe that the presence of such phenylenecyamine compounds
It has been found that the amount of photocurrent generated in the photoactive layer (I) upon irradiation with light increases dramatically compared to the case where it does not exist, thereby increasing the conversion efficiency.

Here, a photoconversion element is one that generates an electromotive force or current, or both, when light is irradiated without applying an external voltage between the front and back electrodes in Figure 1, and that generates a large amount of electromotive force or current when an external voltage is applied. This is an element from which photocurrent can be extracted.

As described above, the photoactive layer (1) is a layer containing as essential components a phenylenediamine compound represented by the general formula and a photoconductive organic semiconductor that absorbs visible light.

The phenylenecyamine compound represented by the general formula has a high ability to be uniformly compatible with other organic semiconductors and binders in the layer without crystallization, and has a low ionization potential among organic compounds, and has a low hole transfer potential. The degree is also high.

Here, the base of each component in the photoactive layer (I) is: 1 to 70 wt% of a phenylene diamine compound, 30 to 90 wt% of a photoconductive organic semiconductor that absorbs visible light, and 0 to 50 wt% of a binder.
Preferably 5 to 50 vt% and 40 to 70 wt%, respectively.
, 10-40vt%.

As the proportion of the phenylenediamine compound decreases, the effect of adding the same compound becomes weaker, and as the proportion of the phenylenediamine compound increases, the concentration of the light-absorbing photoconductive organic semiconductor becomes relatively lower, thereby reducing the amount of light absorbed. becomes smaller.

When the proportion of the photoconductive organic semiconductor decreases, the amount of light absorption decreases, and when the proportion increases, the concentration of the phenylenediamine compound becomes relatively low, and the effect of addition becomes weak.

If the amount of binder is small, the probability that the phenylenediamine compound will crystallize increases, and if it is large, the amount of parts involved in the generation and movement of photocharges will be reduced, resulting in a decrease in efficiency.

The thickness of the photoactive layer is suitably 0.01 to 10 μm.

The optimum film thickness varies depending on the type of photoconductive organic semiconductor and resin used, and is preferably 0.05 to 3 μm. If it is thin, the amount of light absorbed will be small, and the probability of pinholes occurring between the front and back electrodes will increase.

Is it one of the holes and electrons generated as the thickness increases? The distance it takes to reach the electrode increases, the probability of deactivation on the way increases, and efficiency decreases.

For the aqueous layer, mix the above-mentioned organic semiconductor with a resin if necessary in a suitable medium, and in the case of the above-mentioned organic semiconductor or pigment, grind the pigment using a method such as a ball mill to create a uniform slurry, or mix it with an organic amine. After dissolving the pigment in a solvent such as the like, a phenylenediamine compound is added, and these are coated on the back electrode or the back electrode on the support, or the front electrode on the support.

The photoactive layer formed in this manner has a slightly increased open circuit voltage (Voc) and a significant increase in short circuit current (Jsc) compared to the case without the phenylenediamine compound. The conversion efficiency (η) is determined by the following formula, 1n (P i n : incident light energy, ff: fill factor).

The device of the present invention provides higher conversion efficiency than a device without the addition of a phenylenecyamine compound. The reason for this is that since the phenylenediamine compound has a low ionization potential as an organic substance, holes among the photocharges generated in the photoconductive organic 1'-conductor by light absorption are easily injected into the phenylenediamine compound. Also,
The compound also has high hole mobility. For this reason, it is thought that the probability of recombination of holes and electrons is lowered compared to the system without addition, and the efficiency of hole transfer is also increased.

Moreover, of course, even when a voltage is applied from the outside, a large photocurrent can be extracted, and therefore it is used as a photoelectric conversion element with excellent sensitivity.

The phenylenediamine compound used in the present invention is represented by the following general formula.

However, Rl, R2, R3, and R4 above are hydrogen, unsubstituted or an alkyl group substituted with a haloken atom, cyano group, or phenyl group, or unsubstituted or a phenyl group substituted with a halogen atom, a cyano group, a nitro group, or an alkyl group. group, a fused aromatic ring group such as a naphthyl group or anthryl group, or a heterocyclic group such as a carbazolyl group, a furanyl group, a thienyl group, or an indolyl group.

R1, R2 and R3, R4 may form a ring.

The compounds represented by the above general formula include 1,4-bis(N,N-diphenylamino)benzene, 1,4-bis(N-phenyl-N-1-lyluamino)benzene, 4-bis[N -Phenyl-N-(4-methquinphenyl)-aminocobenzene, 1.4-bis(N,N-ditolylamino)hensen, 1
- (N,N-diphenyl)amino-4-(N-phenyl-N-methoxyphenyl-amino)benzene, 1-(N,)J-diphenyl)amino-4-(N,N-
Diethylamino-benzene, 4-(N,N-diphenyl)amino-aniline, 1.
4-bis[N-phenyl-N-(4-diethylamino)
Phenyl-aminocobenzene, 1,4-bis(N,N-
dibenzylamino)benzene, ■, 4-bis(N,N-dimethylamino)benzene, ■
, 4-bis(N,N-diethylamino)benzene, 1-
(N,N-dimethylamino)-4-(N-methyl-N
-phenylamino)benzene, N,N'-diphenylphenylenediamine, N,N'-
Ditolylphenylenediamine, ■, 4-bis[N-phenyl-N-(4-chlorophenyl)aminocobenzene, 1-(4-aminophenyl)amino-4-phenylamino-benzene, 1,4-bis[ N-(3-methylphenyl)-N=phenyl-aminocobenzene, 1.4-bis[N-(3-methoxyphenyl)-N-phenyl-aminocobenzene, 1.4-bis[N-(2 -methylphenyl)-N-phenyl-aminocobenzene, and the like.

Regarding the front electrode layer and its support.

Aluminum, lead, zinc, tantalum, nickel, titanium, cobalt, niobium, copper, Hastelloy C1 gold, platinum,
A translucent metal such as silver or palladium or a metal oxide such as tin oxide or ITO can be used as the front electrode, and glass or a transparent plastic film can be used as the support. Regarding the back electrode and its support: Most metals can be used as the back electrode.

Glass or transparent plastic film is used as the support.

Regarding the photoactive layer (II): This layer contains a) other Gf-generating organic semiconductors in order to cover the low sensitivity wavelength range of the pigments used in the photoactive layer (1), and b) the photoactive layer The layer that forms a junction barrier between C) photoactive 1'1J (1) is a layer that effectively moves either holes or electrons generated in (1).

Among these layers, a compound having a color tone correcting to that of (1) among the exemplified compounds of the photoactive layer (I) described later is highly effective for layer a), and is formed by coating in the same manner as the photoactive layer (1). be done.

The layer b) is formed by dispersing fine particles of zinc oxide, titanium oxide, cadmium sulfide, selenium crystals, lead oxide, etc. in an adhesive resin.

The layer C) is formed by mixing the additive of the photoactive layer (I) or an electron donor with an even lower Ip value with a suitable resin.

The light-absorbing angle machine semiconductor used as an essential component of the present invention includes azo pigments such as disazo pigments and trisazo pigments, phthalocyanine pigments, quinacridone pigments, perylene pigments, aromatic polycyclic boron pigments, and indigo pigments. , thioindigo pigments, and dyes such as triphenylmethane dyes, cyanine dyes, and merocyanine dyes.

Examples of resins used as binders include polyester resins, polycarbonate resins, polyamide resins, polyurethane resins, epoxy resins, alkyd resins, phenolic resins, melamine resins, acrylic resins, cellulose resins, vinyl acetate resins, vinyl chloride resins, and vinylidene chloride. Resin, vinylidene fluoride resin, butyral resin, polyvinylcarbazole resin, polystyrene resin, polyimide resin, polyacrylonitrile resin, vinyl chloride-vinyl acetate copolymer, vinylidene chloride-acrylonitrile copolymer, styrene-maleic anhydride copolymer, styrene -butadiene copolymer, ethyl cellulose, etc.

Next, structural examples of the photoelectric conversion element of the present invention will be explained with reference to the schematic diagrams shown in FIGS. 1 to 3. Figure b shows an example in which a second photoactive layer is added to supplement the photoactive layer shown in figure a.

In the figure, ■ is a translucent front electrode, 2 is a photoactive layer (I),
3 is a photoactive layer (II), 4 is a back iIj electrode, 5 is a front electrode support, and 6 is a back electrode support. It should be understood that these structures can be varied in various ways depending on the application.

Examples are shown below to further specifically explain the present invention, but the present invention is not limited thereto.

Example 1 0.9 g of azo pigment with the following structure and butyral resin (UC
9 g of a 5% tetrahydrofuran solution (XYHL manufactured by Company C) was ball milled for 3 days, and then further diluted with tetrahydrofuran to prepare a 5 wt % solution.

To this solution was added an additive represented by the following structural formula in the same weight as the pigment, and after stirring, a coating solution was prepared.

This coating solution is indium-doped tin oxide (hereinafter referred to as I).
A glass substrate provided with
The substrate was pulled up at a speed of seconds to form a coating film on the ITO substrate.

On top of this, semitransparent aluminum was vacuum-deposited so that the transmittance at 800 nm was about 4.8%, and then ITO
A thin copper wire was connected to the aluminum using silver paste.

This sample was irradiated with 660% m monochromatic light from the At electrode side (the light m P ! no that reached the pigment dispersion film was 1.
The current-voltage characteristics were measured by applying a ramp wave swept at 6 mv/sec to the picture electrode while setting the voltage to 45 μv/c-. The result was Voc-0,91V Jsc-49,lnA/c+f ('r-0,24).

The photoelectric conversion efficiency (η') at 600% m after correcting the transmittance of the electrode was 0.74%.

Example 2 A sample containing an additive was prepared in the same manner as in Example 1, except that the amount of the additive added in Example 1 was changed to 172.

Monochromatic light of 600 r+m was incident on this sample from the Al electrode side (Pin' = 1.45 μv/c), and Example 1
When the photoelectric conversion efficiency was measured in the same manner as above, the following results were obtained.

Voc=0.8[1V Jsc-65,5nA/cJ fr-0,28 η-1,01% Comparative Example 1 A sample was prepared in the same manner as in Example 1 except that no additives were added, and 800% m monochromatic light is incident from the At electrode (Pin
'-1.45 μw/cJ), and the photoelectric conversion efficiency was similarly measured, and the following results were obtained.

Voc-0,77'J Jsc-1,35nA/c4 1'r-0,25 η--0,018% Example 3 The azo pigment in Example 1 was changed to the following, and the additives were changed to the following. A sample containing the additive was prepared in the same manner as in Example 1 except that the sample was changed to a different one.

Monochromatic light of 580% m is incident on this sample from the Al electrode side (
Pin'=1.55 μw/c+#) L. When the photoelectric conversion efficiency was determined as 7Il11 in the same manner as in Example 1, the following results were obtained.

Voc=0.99V Jsc-71,5nA/co! rr-0,23 η--1,05% Azo pigment additive comparative example 2 A sample was prepared in the same manner as in Example 1 except that no additive was added, and monochromatic light of flionm was incident from the At electrode (P
in'=1.45 μw/cJ), and when the light 7u conversion efficiency was similarly measured, the following results were obtained.

Voc=0.74 V Jsc-2,50n^/cJ rr-0,22 η''-0,026% Example 4 Same additives as in Example 3 except that the additives in Example 3 were changed to the following. A sample containing .

Monochromatic light of 580% m is incident on this sample from the A1 electrode side (
When the charging conversion efficiency was measured in the same manner as in Example 1, the following results were obtained.

Voc-1,00V Jsc-54,4nA/cJ rf'-0,24 Example 5 A sample containing additives was prepared in the same manner as in Example 3 except that the additive in Example 3 was changed to the following. .

111 colored lights of 580 nm were incident on this sample from the Al electrode side (Pin' = 1.55 μv/cn L, Example 1
When I measured the photoelectric conversion efficiency in the same way as above, I got the following results. 1) It was done.

Voc-0,96V Jsc-48,4nA/cnf rr-0,21 Cu-0,83% Example 6 Contains additives in the same manner as Example 3 except that the additive in Example 3 was changed to F. A sample was prepared.

580 nm monochromatic light is incident on this test key 1 from the electrode side (
Pin'=1.54 μw/cot) When the photoelectric conversion efficiency was determined as tpj in the same manner as in Example 1, the following results were obtained.

Voc-0,HV Jsc-57,1nA/CJ fr-0,24 Example 7 A sample containing additives was prepared in the same manner as in Example 3 except that the additives in Example 3 were changed to the following.

Monochromatic light of 580 rv is incident on this sample from the Al electrode side (
When the photoelectric conversion efficiency was determined as Δll] in the same manner as in Example 1, the following results were obtained.

Voc-0,92V Jsc-67,4nA/ c♂ rr-0,23 Example 8 A sample containing additives was prepared in the same manner as in Example 1 except that the azo pigment in Example 1 was changed to β-type copper phthalocyanine. Created.

Monochromatic light of 620 nm is incident on this sample from the Al electrode side (
When the photoelectric conversion efficiency was measured in the same manner as in Example 1, the following results were obtained.

Voc-0,93V JSC-22,2nA/at rf-0,24 η--0.3396 Comparative Example 3 A sample was prepared in the same manner as in Example 5 except that no additives were added, and 820 nm monochromatic light was emitted. Incidence from AI electrode (Pin
'-1.5 μv/d), and the photoelectric conversion efficiency was measured in the same manner, and the following results were obtained.

Voc-0,72V Jsc-10,4nA/c4 1'l'-0,26 η--O,ta% [Effect As described above, according to the present invention, a phenylenediamine compound is added to the photoactive layer. By adding it to , it is possible to achieve a photoelectric conversion element that exhibits a high photocurrent, is inexpensive, and has a large area.

For this reason, conventionally, alone or in combination with a binder,
Photoconductive organic semiconductors, which were previously unusable due to their low photocurrent, can now be used effectively, and the range of monthly charges can be expanded.

[Brief explanation of the drawing]

FIGS. 1a to 3 are schematic diagrams showing cross sections of the photoelectric conversion element of the present invention. 1... Transparent front electrode, 2... Photoactive layer (1)
, 3... Photoactive layer (n), 4... Back electrode, end...
Front electrode support, 6... Back electrode support. Procedural amendment (Shark) November 22, 1988 Director General of the Japan Patent Office Yoshi 1) Relationship with Takeshi Moon Case Patent applicant name Date of amendment order for Ricoh Co., Ltd. 58 (Voluntary) (Attachment) (1) Specification The scope of the claims is summarized as follows. ``2. Claims: A photoelectric conversion element having a light-transmitting front electrode, a photoactive layer, and a back electrode, wherein the photoactive layer contains a small amount of a phenylenediamine compound represented by the following general formula. A photoelectric conversion element characterized by the general formula. However, in the above general formula, RI, R2, R3%
R4 is hydrogen, a substituted or unsubstituted aryl group, and R
1 and R2 and R3 and R4 may form a ring. ” (2) Page 5, lines 9-8 from the bottom, “Replace or...”
・Delete "alkyl group". (3) Page 12, lines 1 and 2, "Unsubstituted or . . . alkyl group," is deleted. (4) The descriptions on page 13, lines 1-2 and lines 8-11 are deleted. (5) ``Correction'' on page 15, line 4 of the specification shall be corrected to ``complementary color.'' (6) Similarly, "additive" in the following section should be corrected to "additive." 2 lines below the chemical formula on the top of page 18, 4th line from the bottom on page 19, 8th line from the bottom on page 20, 3rd line from the bottom on page 21, 3rd line on page 25, 7th line from the bottom, (7) Similarly, "sample containing similar additives" in the following section should be corrected to "similar sample." Page 20, last line, page 22, line 9, page 23, line 1, 5th line from the bottom, page 24, line 3 from "Example 7" (8), also page 21 "Example 1" in the third line from the bottom is corrected to "Example 3". (9) Same, second line from the bottom, correct r600J to r580J. Similarly, the ending line r 1.45J is corrected to r 1.55J.

Claims (1)

[Scope of Claims] A photoelectric conversion element having a translucent front electrode, a photoactive layer, and a back electrode, wherein the photoactive layer at least comprises:
A photoelectric conversion element characterized by containing a phenylenediamine compound represented by the following general formula. General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ However, in the above general formula, R_1, R_2, R_3
, R_4 is hydrogen, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group, and R_1 and R_2 and R_3 and R_4 may form a ring.