JP2003249670A - Solar battery for flexible display, display device and electronic book - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flexible solar battery of light weight and low cost which is used for an auxiliary power source of a flexible display. <P>SOLUTION: The solar battery for a flexible display is provided which has a characteristic that a photoelectric conversion layer is arranged on a flexible base material. Since flexibility is imparted to the base material itself, the solar battery is not cracked when the flexible display is bent in the case that the solar battery is used as the auxiliary power source or the like of a flexible display. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell for a flexible display, a display device and an electronic book.

[0002]

2. Description of the Related Art In recent years, there has been an increasing need for a thin, light and portable display which is portable like paper.

A liquid crystal display formed on a flexible plastic film and a special table 11-50295.
An electronic book or the like using the electronic picture transfer type electronic paper disclosed in No. 0 has received a great deal of attention.

However, in such a portable display, a power source for driving the display is required, and a battery is generally built in the display and used as the power source.

However, in this case, the flexible display cannot be used when the secondary battery has reached the end of its life.

Further, if the battery is made larger in order to extend the carrying time, the flexible display becomes heavier.

Therefore, using a solar cell as the auxiliary power source is an extremely effective method for driving the battery for a long time.

However, the conventional solar cell has a single crystal Si
Many of them use semiconductor wafers, such as semiconductor wafers, or stack thin-film solar cells on a glass substrate. When such solar cells are used as an auxiliary power source for flexible displays, the solar cells do not have flexibility. There was a problem that it would break when it was bent.

In addition, the weight of the flexible display, which is a great feature that the glass and the solar cell element itself are too thick to be suitably provided in the flexible display, and that the solar cell itself is heavy, is lightweight. There is also the problem of becoming heavy.

[0010]

The present inventors have arrived at the present invention as a result of intensive studies to solve the drawbacks of the conventional power source solar cells such as auxiliary power sources for flexible displays. An object of the present invention is to provide a flexible, lightweight, inexpensive solar cell for an auxiliary power supply of a flexible display.

[0011]

In order to solve the above-mentioned problems, the invention according to claim 1 is characterized in that a photoelectric conversion element is provided on a flexible base material. For solar cells. When the base material itself is made flexible and used as a power source such as an auxiliary power source for a flexible display, the solar cell will not be broken even if the flexible display is curved.

The invention according to claim 2 is the solar cell for flexible display according to claim 1, wherein the flexible substrate is an organic plastic film. By using an organic plastic film, an inexpensive and lightweight solar cell can be provided.

The invention according to claim 3 is the solar cell for a flexible display according to claim 1 or 2, characterized in that both surfaces are transparent. Since both sides are transparent, electricity can be generated even if light is incident only from one side.

Further, the invention according to claim 4 is the invention according to claims 1 to 3.
It is a flexible display device using the solar cell for flexible displays as described in any one of 3 above.
By using such a solar cell, it is possible to realize a lightweight, inexpensive, flexible flexible display with a power source such as an auxiliary power source. In particular, when the solar cell for a flexible display according to claim 3 is used, a flexible display with an auxiliary power source that can generate power regardless of which light is incident can be realized.

The invention according to claim 5 is the flexible display device according to claim 4, characterized in that the area ratio of the photoelectric conversion element to the entire flexible display device is 5% or more. Solar cells can generate more current in large areas,
The area ratio of the photoelectric conversion element to the entire flexible display is preferably 5% or more, and more preferably 10% or more.

The invention according to claim 6 is an electronic book using the flexible display device according to claim 4 or 5. By using such a solar cell, it is possible to realize a lightweight, inexpensive, flexible electronic book with a power source such as an auxiliary power source.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

First, as the flexible base material of the solar cell of the present invention, polymethylmethacrylate, polycarbonate,
Polystyrene, polyethylene sulfide, polyether sulfone, polyolefin, polyethylene terephthalate, polyethylene naphthalate, triacetyl cellulose, polyvinyl fluoride film, ethylene-tetrafluoroethylene copolymer resin, weather resistant polyethylene terephthalate, weather resistant polypropylene, glass fiber reinforced acrylic resin Film, glass fiber reinforced polycarbonate, polyimide, transparent polyimide, fluorine resin,
A transparent film such as a cyclic polyolefin resin or a polyacrylic resin, an opaque film such as a SUS thin plate, or an Al foil can be used, but the present invention is not limited thereto.

These may be used as a single film, but it is also possible to use a composite film in which two or more kinds are laminated.

The photoelectric conversion element provided on the flexible substrate is
It is composed of electrode / photoelectric conversion layer / electrode. Either one or both of the two electrodes sandwiching the photoelectric conversion layer is transparent. The transparent electrode is also called a transparent electrode, and the opaque electrode is also called a back electrode. When light enters from the transparent electrode, light energy is converted into electric energy in the photoelectric conversion layer, and the converted electric energy is extracted from the two electrodes. Therefore, when the two electrodes sandwiching the photoelectric conversion layer are transparent, electric energy can be obtained regardless of which side the light enters.

The photoelectric conversion element in the solar cell of the present invention means all that generate electricity by utilizing the photovoltaic effect of semiconductors, such as silicon (polycrystalline or amorphous) solar cells and compound semiconductors ( A photoelectric conversion element using a photoelectric conversion layer of a solar cell, a photoelectric conversion layer of an all-solid-state dye-sensitized solar cell, a photoelectric conversion layer of an organic semiconductor solar cell, or the like is particularly preferable. Used for.

As the material of the transparent electrode, a transparent oxide conductive thin film or an ultrathin metal film can be used.
As the transparent oxide conductive thin film, tin oxide, tin oxide added with indium, zinc oxide, zinc oxide added with gallium,
As the zinc oxide to which aluminum is added and the ultrathin metal thin film, chromium, aluminum, silver, platinum, gold, nickel-chromium alloy, etc. can be used, but not limited thereto. The thickness of the ultrathin metal thin film is 75 nm or less, preferably 35 nm or less. Further, it may be a laminated body of various transparent oxide conductive thin films, a laminated body of ultrathin metal thin films, or a laminated body of transparent oxide conductive thin films and ultrathin metal thin films.

These electrode thin films are formed by vacuum vapor deposition, reactive vapor deposition, ion beam assisted vapor deposition, sputtering, ion plating, vacuum deposition processes such as plasma CVD, gravure coating and screen coating. It is possible to use a film forming process that combines a wet coating method, a heat drying method, a heat curing method, an ultraviolet ray irradiation curing method, an electron beam irradiation curing method, and the like, and the method most suitable for the characteristics of each thin film is appropriately selected. Any other film forming method may be used.

Further, in order to compensate for the high resistivity of the transparent conductive oxide thin film or the ultrathin metal film, a comb-shaped metal electrode may be provided to the extent that the light receiving area is not significantly lost.

In order to make more effective use of sunlight in the present invention, it is possible to provide an antireflection layer utilizing the interference of light on either the above layers or between the layers.

The antireflection film utilizes the coherence of light and is generally composed of a layer having a predetermined optical film thickness nd (refractive index n × shape film thickness d) in order to obtain a desired antireflection property. The number of layers is not particularly limited in the present invention.

As the antireflection film, a low refractive index layer such as silicon oxide or an organic fluorine compound may be provided as a single layer, but usually 1 to 6 layers in view of cost and antireflection effect. Is preferred.

The antireflection film is formed by vacuum vapor deposition, reactive vapor deposition,
Ion beam assisted vapor deposition method, sputtering method, ion plating method, vacuum film forming process such as plasma CVD method, wet coat such as gravure coat and screen coat, and heat drying method, heat curing method, ultraviolet irradiation curing method,
It is possible to use a film forming process in which an electron beam irradiation curing method or the like is combined, and an optimum method is appropriately selected for the characteristics of each thin film. Any other film forming method may be used.

In order to improve the weather resistance of the solar cell element, a gas barrier layer may be provided on either of the above layers or between the layers. Silicon oxide (SiO
x), silicon nitride (SiNx), aluminum oxide (AlxOy) alone, or a mixed vapor deposition layer of two or more thereof, or an inorganic-organic hybrid coat layer, or two or more thereof. A composite layer obtained by combining the above can be preferably used.

The above silicon oxide (SiOx), silicon nitride (SiNx), aluminum oxide (AlxOy)
The vapor deposition layer such as can be easily formed on the substrate film by a vapor deposition method, a sputtering method, a CVD method, a dipping method, a sol-gel method, or the like.

The thickness of such a gas barrier layer is 5 to 5
A range of 00 nm is suitable, and a range of 30 to 150 nm is particularly preferable.

Further, in order to improve the performance of the photoelectric conversion element, it is possible to appropriately provide an uneven light confining layer. For this, the flexible base material itself may be processed into an uneven shape, or a gas barrier layer, an antireflection layer, or a transparent conductive metal oxide may be grown to have an uneven shape, and a wet and It is also possible to perform uneven processing by dry etching or the like. It is also possible to add an uneven layer.

The flexible display of the present invention means all displays having flexibility, such as flexible liquid crystal display, electrophoretic display and organic EL display.
(Organic Light Emitting D
iode) and the like.

Since the solar cell of the present invention is flexible,
Compared to a conventional solar cell using a glass substrate or the like, it has excellent bending resistance even in a large area. In addition, solar cells can generate more current if they have a large area,
The area ratio of the photoelectric conversion element to the entire flexible display is preferably 5% or more, and more preferably 10% or more.

[0035]

EXAMPLES In the following, when the photoelectric conversion element is composed of transparent electrode / photoelectric conversion layer / back surface electrode, the photoelectric conversion element is composed of transparent electrode / photoelectric conversion layer / transparent electrode in the order of The battery will be specifically described.

1. In the case of transparent electrode / photoelectric conversion layer / back surface electrode First, when the photoelectric conversion element is composed of transparent electrode / photoelectric conversion layer / back surface electrode, the solar cell of the present invention will be specifically described below with reference to the drawings. . However, the present invention is not limited to these drawings. 1 to 3 show schematic sectional views of the solar cell of the present invention as an example.

The case of FIG. 1 is an example in which the photoelectric conversion element 1 is formed on the flexible base material 2, and the back electrode side thereof is laminated on the back surface protection sheet 3 for solar cells via the adhesive layer 5. In this case, the flexible base material 2 needs to transmit sunlight.

In the case of FIG. 2, the photoelectric conversion element 1 is formed on the flexible substrate 2, and the surface protection sheet 4 is laminated on the sunlight incident side (transparent electrode side) with the adhesive layer 5 interposed therebetween. is there. In this case, the flexible base material 2 may be transparent or opaque.

In the case of FIG. 3, as in the case of FIG. 2, the photoelectric conversion element 1 is formed on the flexible substrate 2, and the surface on the light incident side (transparent electrode side) thereof effectively takes in sunlight. This is an example in which the antireflection film 6 is formed.

In the above structure, although not shown in the figure, a gas barrier layer as described above may be provided on any layer of the film for a solar cell, if necessary, in order to prevent reflection in the case of FIGS. 1 and 2. A layer can be provided, and a protective layer formed by film laminating or resin coating can be further provided thereon. It is also preferable to provide an antifouling layer on the outermost surface of the solar cell film.

When the adhesive layer is used, the thickness of the adhesive layer is not particularly limited, and the adhesive layer can be laminated on the substrate film or the like with a thickness suitable for the type and shape of the photoelectric conversion element. Regarding the lamination method, depending on the material of the adhesive layer and the thickness to be laminated,
For example, it can be laminated on the surface of the base film by an appropriate means such as a coating method using a solution or a dispersion, an extrusion coating method, a calendar coating method, a thermal laminating method, a dry laminating method.

FIGS. 4 and 5 show an example of mounting such a flexible solar cell on a flexible display and an electronic book. However, it is not limited to the following example. The flexible solar cell has a flexible display (size 370 mm × 29) as shown in FIG.
0mm) Frame part 8 (30mm up and down from the edge, left and right 45
mm), the back surface 9 of the flexible display, or an electronic book (size 255 mm x 175 mm) as shown in FIG.
It can be provided by sticking to a front cover 10, a back cover 11, a spine cover 12, etc. of 10 mm x 10 mm, total 5 pages.

The drive circuit will be described with reference to the drawings. FIG. 6 is a drive circuit diagram of the display of the present invention. This structure is the same as the drive circuit of a normal display except that it has an auxiliary power supply 20 and a power supply switching circuit 21. That is, the IC 40 includes a CPU 44 that processes data according to a user program, a ROM 46 that stores the program, and an R that stores the data.
An AM 47, a clock 45 for operation, a bus 43 for transmitting data and an address, and a display control circuit 41 for actually issuing a drive signal for a display.

When supplying power to the IC 40, the power from the auxiliary power source 20 and the power obtained from the main power source 30 are connected to the power source switching circuit 21 so that the power source can be switched. When switching the power supply, the power supply switching circuit 21 consisting of a diode designed to prevent an instantaneous interruption.
To form.

The main power source 30 is connected to the power source switching circuit 21 through the power source stabilizing circuit 31. As a result, the main power source 3
15 for the duration of lighting, even if the electromotive force of 0 is lost
The voltage of V was continuously obtained. The actual circuit is formed by connecting the circuit at the spine of the book because the auxiliary power supply 20 is provided on the cover and the display is provided on the body when the electronic book format is used.

By using such a flexible solar cell as an auxiliary power source for a flexible display, a flexible, lightweight and inexpensive flexible display or electronic book can be provided, as described above.

2. In the case of transparent electrode / photoelectric conversion layer / transparent electrode Next, when the photoelectric conversion element is composed of transparent electrode / photoelectric conversion layer / transparent electrode, the solar cell of the present invention will be specifically described below with reference to the drawings. To do. However, the present invention is not limited to these drawings. 7 to 14 schematically show the cross section of the solar cell of the present invention as an example.

In FIG. 7, a transparent conductive metal oxide 62 is formed on a transparent flexible substrate 63, a photoelectric conversion layer 61 and a transparent conductive metal oxide 62 are formed thereon, and an adhesive layer 65 is formed thereon. This is an example in which the transparent flexible base material 63 is adhered via.

In FIG. 8, the transparent conductive metal oxide 62 is formed on the transparent flexible substrate 63, and the photoelectric conversion layer 6 is formed thereon.
In this example, the ultra-thin metal film 66 is formed, and the transparent flexible base material 63 is adhered on the ultra-thin metal film 66 via the adhesive layer 65.

In FIG. 9, an ultrathin metal film 66 is formed on a transparent flexible substrate 63, a photoelectric conversion layer 61 and a transparent conductive metal oxide 62 are formed thereon, and an adhesive layer 65 is formed thereon. This is an example in which the transparent flexible base material 63 is adhered via.

In FIG. 10, an ultrathin metal film 66 is formed on a transparent flexible substrate 63, a photoelectric conversion layer 61 and an ultrathin metal film 66 are formed on the ultrathin metal film 66, and an adhesive layer 65 is formed on the transparent thin film 66. This is an example in which the flexible substrate 63 is bonded.

The thickness of the adhesive layer is not particularly limited, and the adhesive layer can be laminated on the substrate film or the like with a thickness suitable for the type and shape of the photoelectric conversion element.

Regarding the laminating method, depending on the material of the adhesive layer and the thickness to be laminated, for example, a coating method using a solution or a dispersion, an extrusion coating method, a calendar coating method, a thermal laminating method, a dry laminating method, or the like can be used. It can be laminated on the substrate film surface or the like by an appropriate means.

In FIG. 11, a transparent conductive metal oxide 62, a photoelectric conversion layer 61, and a transparent conductive metal oxide 62 are laminated in this order on a transparent flexible substrate 63, and a gas barrier layer 64 is formed thereon. Here is an example.

In FIG. 12, a transparent conductive metal oxide 62, a photoelectric conversion layer 61, and an ultrathin metal film 66 are formed on a transparent flexible substrate 63.
This is an example in which the gas barrier layer 64 is formed by laminating in this order.

FIG. 13 shows an ultrathin metal film 66, a photoelectric conversion layer 61, and a transparent conductive metal oxide 62 on a transparent flexible substrate 63.
This is an example in which the gas barrier layer 64 is formed by laminating in this order.

FIG. 14 shows an example in which an ultrathin metal film 66, a photoelectric conversion layer 61, and an ultrathin metal film 66 are laminated in this order on a transparent flexible substrate 63, and a gas barrier layer 64 is formed thereon.

In the case of the example of FIGS. 11 to 14, the adhesive layer is
Although not necessarily required, a transparent protective film or the like may be further laminated on the gas barrier layer 64 via an adhesive layer.

In any of the examples shown in FIGS. 7 to 14, an antireflection layer can be provided, and a protective layer formed by film laminating or resin coating can be further provided thereon. It is also preferable to provide an antifouling layer on the outermost surface of the solar cell film, and it is also possible to form a gas barrier film as appropriate.

By using a solar cell having such a structure and having transparent both sides as an auxiliary power source for the flexible display, it is possible to generate electricity even in a situation where only one side of the flexible display is exposed to light. A flexible display having a battery can be provided.

Examples will be described more specifically below.

Example 1 Weatherproof PET (thickness 188
m), on each side of which SiOx was formed by vapor deposition with a thickness of 40 nm, and tin oxide (ITO) on one side of which was added indium
A thin film is formed by sputtering with a film thickness of 400 nm at a substrate temperature of 65 ° C., followed by PECVD (Plasma Enhance).
d Chemical Vapor Depositi
on), p layer, i layer, and n layer of amorphous silicon are stacked at a substrate temperature of 75 ° C., and a tin oxide (ITO) thin film with indium added thereon is deposited at a substrate temperature of 65 ° C.
It is formed by 0 nm sputtering. Then, a light resistant PET was laminated thereon as a protective layer via an adhesive.

Example 2 Weatherproof PET (thickness 188
m) SiOx is formed on both sides by 40 nm by vapor deposition, and Ag is formed on one side by EB vapor deposition at a substrate temperature of 20 nm to form a film having a thickness of 20 nm, followed by PECVD (Plasma).
Enhanced Chemical Vapor
P layer, i layer, and n layer of amorphous silicon are stacked at a substrate temperature of 75 ° C. by a deposition method, and a tin oxide (ITO) thin film to which indium is added is formed thereon by sputtering at a substrate temperature of 65 ° C. to a film thickness of 400 nm. . Then, a light resistant PET was laminated thereon as a protective layer via an adhesive.

Example 3 Weatherproof PET (thickness 188
m) SiOx is formed on both sides by 40 nm by a vapor deposition method, and a tin oxide (ITO) thin film added with indium is sputtered on the one side at a substrate temperature of 65 ° C. by a thickness of 400 nm, followed by PECVD (Plasma Enhance).
d Chemical Vapor Depositi
The p layer, the i layer, and the n layer of amorphous silicon are laminated by the on) method at a substrate temperature of 75 ° C., and Ag is formed thereon by a EB vapor deposition method at a substrate temperature of room temperature to a film thickness of 20 nm. Subsequently, a SiOx thin film (x = 1.7) having a thickness of 40 nm was formed thereon by PECVD.

Comparative Example 1 Weatherproof PET (thickness 188
m) 40 nm of SiOx on both sides in the same manner as in Examples 1 to 3.
And a tin oxide (ITO) thin film to which indium is added on one side thereof at a substrate temperature of 65 ° C.
Formed by 0 nm sputtering, and then PECVD (Plasm
a Enhanced Chemical Vapor
A p-layer, an i-layer, and an n-layer of amorphous silicon were stacked at a substrate temperature of 75 ° C. by a deposition method, and finally a vapor deposition layer of Ag was formed as a reflective layer at a substrate temperature of room temperature to manufacture a solar battery cell. Subsequently, a light-resistant PET was laminated as a back surface protection layer on the Ag vapor deposition layer side via an adhesive.

[Tests and Results] The solar cells 72 of Examples 1 to 3 and Comparative Example prepared as described above are shown in FIG.
As shown in FIG. 5, the flexible display 70 was connected to the side surface so that light could enter from both sides of the solar cell 72 as shown in FIG. Table 1 below shows the impossibility of power generation in the direction of incident light. When power is generated, it is indicated as ○, and when it is not generated, as ×. However, the case where the light is incident from the weather resistant PET side used as the substrate when the photoelectric conversion layer is attached is defined as the front side incident, and the case where the light is incident from the opposite side is defined as the back side incident.

[0067]

[Table 1]

As can be seen from Table 1, the solar cells of Examples 1 to 3 can generate power regardless of which direction the light is applied. By using such a solar cell as an auxiliary power source, the solar cell can effectively function as an auxiliary power source for a flexible display even when light is incident from only one direction.

[0069]

As is apparent from the above description, by using the solar cell formed on the flexible base material of the present invention as a power source such as an auxiliary power source for a flexible display, a flexible, lightweight and inexpensive auxiliary power source is provided. We can provide flexible displays and electronic books with power supplies.

Further, by making both surfaces of the solar cell for auxiliary power source of the flexible display transparent, it is possible to provide a solar cell characterized in that power can be generated even in a situation where light is incident from only one of them.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an embodiment of a solar cell for an auxiliary power supply of a flexible display of the present invention.

FIG. 2 is a schematic cross-sectional view showing an embodiment different from FIG. 1 of a solar cell for an auxiliary power supply of a flexible display of the present invention.

FIG. 3 is a schematic cross-sectional view showing an embodiment different from FIGS. 1 and 2 of a solar cell for an auxiliary power supply of a flexible display of the present invention.

FIG. 4 is a schematic view showing an example in which a solar cell for a flexible display auxiliary power supply of the present invention is installed.

FIG. 5 is a perspective view of an embodiment of an electronic book in which a solar cell for a flexible display auxiliary power supply of the present invention is installed.

FIG. 6 is a circuit diagram showing an example using a solar cell for a flexible display auxiliary power supply of the present invention.

FIG. 7 is a schematic sectional view showing an embodiment different from FIGS. 1 to 3 of a solar cell for an auxiliary power supply of a flexible display of the present invention.

FIG. 8 is a schematic cross-sectional view showing an embodiment different from FIGS. 1 to 3 and FIG. 7 of a solar cell for an auxiliary power supply of a flexible display of the present invention.

FIG. 9 is a schematic cross-sectional view showing an embodiment different from FIGS. 1 to 3 and FIGS. 7 and 8 of the solar cell for the auxiliary power supply of the flexible display of the present invention.

FIG. 10 is a schematic cross-sectional view showing an embodiment different from FIGS. 1 to 3 and FIGS. 7 to 9 of the solar cell for auxiliary power supply of the flexible display of the present invention.

FIG. 11 is a schematic cross-sectional view showing an embodiment different from FIGS. 1 to 3 and FIGS. 7 to 10 of the solar cell for auxiliary power supply of the flexible display of the present invention.

FIG. 12 is a schematic sectional view showing an embodiment different from FIGS. 1 to 3 and FIGS. 7 to 11 of the solar cell for auxiliary power supply of the flexible display of the present invention.

FIG. 13 is a schematic cross-sectional view showing an embodiment different from FIGS. 1 to 3 and FIGS. 7 to 12 of the solar cell for auxiliary power supply of the flexible display of the present invention.

FIG. 14 is a schematic cross-sectional view showing an embodiment different from FIGS. 1 to 3 and FIGS. 7 to 13 of the solar cell for auxiliary power supply of the flexible display of the present invention.

FIG. 15 is a schematic view showing an example in which a solar cell for a flexible display auxiliary power supply having transparent both sides according to the present invention is connected to a flexible display.

FIG. 16 is a schematic view showing an example in which a solar cell for a flexible display auxiliary power supply with transparent both sides according to the present invention is connected to a flexible display.

[Explanation of symbols]

1 ... Photoelectric conversion element 2 ... Flexible base material 3 ... Back surface protection sheet for solar cells 4 surface protection sheet 5 ... Adhesive layer 6 ... Antireflection layer 7 ... Image display section 8 ... Frame part 9 ... Flexible display backside 10 ... Ebook cover 11 ... Ebook back cover 12 ... Ebook back cover 20 ... Auxiliary power supply 21 ... Power switching device 30 ... Main power supply 31 ... Voltage stabilizing circuit 40 ... IC 41 ... Display control circuit 43 ... bus 44 ... CPU 45 ... Clock 46 ... ROM 47 ... RAM 50 ... Display 61 ... Photoelectric conversion layer 62 ... Transparent conductive metal oxide 63 ... Flexible transparent substrate 64 ... Gas barrier layer 65 ... Adhesive layer 66 ... Ultra-thin metal film 70 ... Flexible display 71 ... Display display 72 ... Solar battery for auxiliary power supply

Claims (6)

[Claims] 1. A solar cell for a flexible display, wherein a photoelectric conversion element is provided on a flexible base material. 2. The solar cell for a flexible display according to claim 1, wherein the flexible substrate is an organic plastic film. 3. The solar cell for flexible display according to claim 1, wherein both sides are transparent. 4. A flexible display device using the solar cell for a flexible display according to claim 1. 5. The flexible display device according to claim 4, wherein an area ratio of the photoelectric conversion element to the entire flexible display device is 5% or more. 6. An electronic book using the flexible display device according to claim 4.