JP2004031648A - Photoelectric conversion element having optical confinement layer, photoelectric conversion device and solar battery having the device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric conversion element which is suitably used for a thin film type solar battery or the like and has an optical confinement layer which can efficiently confine an incident light in a substrate, a photoelectric conversion device and a solar battery having the device. <P>SOLUTION: In the optical confinement layer 2 which is used for a photoelectric conversion device and has unevenness of a prescribed shape, an optical confinement layer wherein a cell constituted of lattice-shaped unevenness is made a structural unit is arranged on a substrate 1 along almost the whole surface. The photoelectric conversion element having the optical confinement layer, the photoelectric conversion device and the solar battery having the device are provided. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a photoelectric conversion element and a photoelectric conversion device having a light confinement layer capable of efficiently trapping incident light used in a thin-film solar cell or the like in a substrate, and a solar cell including the device.
[0002]
[Prior art]
The photoelectric conversion element uses a transparent conductive layer in which a transparent conductive layer such as tin oxide or ITO (indium tin oxide) is formed on a glass surface as a substrate. 2. Description of the Related Art In a thin film solar cell which is one of photoelectric conversion elements, a transparent conductor having a tin oxide layer formed on a glass surface is widely used. A thin-film solar cell using thin-film silicon as a photoelectric conversion material has attracted much attention because of its low energy cost.
[0003]
In a general configuration of a thin-film silicon solar cell, an underlayer, a transparent conductive layer, thin-film silicon, and a metal layer are sequentially formed on the surface of a glass plate.
[0004]
As the transparent conductive layer, a tin oxide layer formed by a method involving a thermal decomposition oxidation reaction of a raw material such as a chemical vapor deposition (CVD) method is often used. The base layer is provided in order to prevent an alkali component such as sodium contained in the glass plate from diffusing into the transparent conductive layer and lowering the electric resistance characteristics (increase in resistance) of the transparent conductive layer. A transparent thin layer such as a silicon oxide layer is used as the underlayer.
[0005]
A transparent conductive layer for a thin-film solar cell is required to have a high transmittance (more light is input to the photoelectric conversion layer) and a low resistance (to reduce a loss when taking out generated current). Further, it is known that when appropriate irregularities are provided on the surface of the transparent conductive layer, incident light is scattered on the surface of the transparent conductive layer, which is effective in confining light in the photoelectric conversion layer.
[0006]
As a preferable example of the uneven shape, for example, Japanese Unexamined Patent Application Publication No. Sho 61-288473 describes an uneven shape having a height difference of about 1000 to 5000 angstroms and an interval between the convex portions of about 2000 to 10000 angstroms.
[0007]
Further, for example, Japanese Unexamined Patent Publication No. Hei 2-503615 describes an uneven shape having a diameter of 0.1 μm to 0.3 μm and a height / diameter ratio of 0.7 to 1.2. .
[0008]
Furthermore, for example, Japanese Patent Application Laid-Open No. 4-133360 discloses that a projection having a truncated pyramid shape or a pyramid shape having a height of 1000 to 3000 Angstroms has an angle between its ridge line and the normal line of the substrate of 30 to 50 degrees. Certain irregularities are described.
[0009]
Conventionally, it has been said that it is preferable to increase the scattering component of incident light as much as possible in order to increase the effect of the light confinement. Therefore, a substrate having a haze ratio of more than 10% has been considered preferable. For example, Japanese Unexamined Patent Publication No. 2-503615 discloses a substrate having a haze ratio of 8 to 30%.
[0010]
It is known that the characteristics of a solar cell obtained by forming the surface of a transparent conductive layer into such a concavo-convex shape to form a substrate having a high haze ratio and depositing amorphous silicon on the surface thereof are improved. .
[0011]
[Problems to be solved by the invention]
However, the uneven shape of the transparent conductive layer is a property directly related to the performance of a thin-film solar cell or the like, and further improvement is required. In addition, the conventional concavo-convex shape is a shape observed with an electron microscope. In order to confirm the shape, it is necessary to increase the observation magnification, and the observation result in a narrow area (about 1 to 2 μm square) is naturally obtained. Therefore, it was not always possible to provide an optimum uneven shape.
[0012]
In addition, the range of the height and interval of the convex portion, the angle of the ridge line, and the like are described in the patent publications cited above, but as a practical problem, the transparent conductive layer in which all the irregularities are within the range is described. It is difficult to form, and the size and shape of the unevenness are formed with a certain distribution. In particular, it is known that the use of a transparent conductive layer having a surface irregularity in which irregularities are uneven and a large number of convexes having a large particle diameter are present in a thin-film solar cell substrate deteriorates battery performance. In the observation method, the observation area was too small to discuss the distribution of the uneven shape, and nothing was mentioned.
[0013]
Here, the reason why the performance of the battery deteriorates when a transparent conductive layer having a surface irregularity in which irregularities are irregular and the number of convexes having a larger particle diameter than the surroundings are present is used for a thin-film solar cell substrate is obvious. Has not been. However, when a photoelectric conversion layer such as amorphous silicon is formed on a transparent conductive layer having a projection having a larger particle size than the surrounding area, a decrease in step coverage to the transparent conductive layer can be prevented. As a result, the quality of amorphous silicon film deteriorates, and as a result, a large amount of incident light is absorbed at the interface between the transparent conductive layer and the photoelectric conversion layer, and the amount of light incident on the photoelectric conversion layer decreases. It is thought to invite. In addition, it is considered that the bonding between the transparent conductive layer and the photoelectric conversion layer becomes poor, the resistance increases, and the loss when extracting the generated current increases.
[0014]
Therefore, the present invention has been made to solve the above technical problem, and has a photoelectric confinement layer that is preferably used for a thin-film solar cell or the like and has a light confinement layer capable of efficiently confining incident light in a substrate. An object is to provide a conversion element, a photoelectric conversion device, and a solar cell including the device.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is directed to a light confinement layer having irregularities of a predetermined shape used in a photoelectric conversion device,
A photoelectric conversion element having a light confinement layer, characterized in that a light confinement layer having a cell composed of lattice-like irregularities as a constituent unit is arranged over substantially the entire surface of a substrate.
[0016]
According to a second aspect of the present invention, in the photoelectric conversion element having the optical confinement layer according to the first aspect, the cell constitutive unit forming the optical confinement layer includes a cell having a curved lattice-like unevenness. .
[0017]
According to a third aspect of the present invention, in the photoelectric conversion element having the light confinement layer according to the first or second aspect, the lattice pitch is in a range of 5 to 500 μm and the height of the unevenness is in a range of 0.5 to 2 μm. It is characterized by.
[0018]
The invention according to claim 4 includes, in this order, a first electrode layer, a semiconductor photoelectric conversion layer, and a second electrode layer formed on a substrate, and the light confinement is provided between the substrate and the semiconductor photoelectric conversion layer. A photoelectric conversion device, wherein layers are arranged.
[0019]
The invention according to claim 5 is a solar cell having the photoelectric conversion device according to claim 4,
The solar cell has a structure fixed to the ground without changing its direction, and the cells forming the light confinement layer included in the photoelectric conversion device are selected and arranged corresponding to the solar orbit with season or time. A solar cell having a configuration.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
Note that the dimensional relationships are appropriately changed for clarity of the drawings and do not reflect the actual dimensional relationships, but do not obscure the present invention.
[0021]
FIG. 1 is a schematic sectional view showing a photoelectric conversion device as one embodiment of the present invention. As shown in FIG. 1, a fine uneven pattern of an uneven layer 2 for causing light diffusion on a substrate 1 is formed by using an electron beam exposure apparatus and controlling the computer to control X on which a planar substrate is placed. -Made by moving the Y stage.
[0022]
In the present invention, the fine concavo-convex pattern is not particularly limited, such as a prism-shaped pattern having a triangular or circular cross section, or a lens array-shaped pattern provided with pyramid-shaped or hemispherical units, and other irregular shapes. An uneven pattern may be mentioned, which may be regular or irregular. Also, the size of the concavo-convex pattern is not particularly limited, and, for example, the height and the pitch are each selected from about 0.5 μm to about several hundred μm. When used as a solar cell substrate, those having a height of about 0.3 μm to 2 μm and a pitch of about 0.5 μm to 3 μm are preferable. By using such a concavo-convex layer having a fine pattern, light absorption due to the light confinement effect is achieved. To increase efficiency conversion.
[0023]
In addition, in addition to enabling light scattering within the concavo-convex layer, the concavo-convex pattern in the present invention can be processed into a concavo-convex shape corresponding to the characteristics of incident light. For example, as shown in FIGS. 3 (a) and 3 (b), corresponding to the solar orbit of the sun which is incident light in the solar cell (see FIG. 2), the uneven layer is processed into a semicircular shape, By setting the center to the south, light can be efficiently scattered from sunrise to sunset.
[0024]
In addition, as shown in FIG. 4, by forming these irregularities in a cell structure with a width direction: 5 μm to 500 μm and a height: 0.5 μm to 2 μm, a uniform light scattering action over the entire surface of the irregularity layer. Can be obtained.
[0025]
Light scattering can also be controlled by changing the height, pitch, and shape of the irregularities in the cell structure described above.
[0026]
In the concavo-convex layer having the above-mentioned cell structure, one cell structure is created in the same manner as described above using an electron beam exposure apparatus, and the obtained concavo-convex layer is copied by a simple process such as embossing using the concavo-convex layer. By providing multiple surfaces, a photoelectric conversion element can be formed as one surface of the uneven layer.
[0027]
After the concavo-convex layer is formed, the transparent conductive layer 3, the semiconductor photoelectric conversion layer 4, the transparent conductive layer 5, and the metal electrode layer 6 are sequentially formed as other layers by the same known method as in the conventional photoelectric conversion device. It is laminated.
[0028]
On the uneven layer 2, a transparent electrode layer 3 made of tin oxide, ITO or the like is formed.
On the transparent electrode layer 3, for example, an amorphous silicon (a-Si) layer is deposited as the semiconductor photoelectric conversion layer 4. The a-Si layer 5 may include, for example, a sequentially stacked p-type sub-layer, i-type sub-layer, and n-type sub-layer (not shown). On the a-Si layer 4, the back surface reflective metal electrode layer 6 is laminated.
[0029]
On the a-Si layer 4, a backside reflective metal electrode layer 6 is laminated with a transparent layer 5 of ZnO preferably interposed. The ZnO layer 5 acts to prevent metal atoms from diffusing from the metal electrode layer 6 into the a-Si layer 4. Further, it can function as a part of the back electrode.
[0030]
It is needless to say that in the photoelectric conversion device shown in FIG. 1, light is incident from the light-transmitting substrate 1 side. As the translucent substrate 1, an electrically insulating resin film such as a polyester film can be used. When the resin film substrate 1 is used, the photoelectric conversion device can be reduced in weight, its handling can be simplified, and its manufacturing cost can be reduced. The material of the resin film substrate 1 is not limited to polyester, and polyimide, polycarbonate, polyethersulfone (PES) resin, fluororesin, or the like may be preferably used. Further, as the substrate 1, a glass plate may be used instead of the resin film.
[0031]
Further, the a-Si layer 4 of the photoelectric conversion device according to the present invention may have a tandem cell or triple cell structure in which a plurality of pin-type a-Si optical semiconductor elements are stacked.
[0032]
FIG. 5 is a schematic sectional view showing a photoelectric conversion device as another embodiment of the present invention. In this photoelectric conversion device, an uneven layer 2 according to the present invention is formed on a substrate 1 in a manner similar to the above-described method of forming unevenness in order to cause light diffusion. Further, these fine uneven patterns and sizes are not particularly limited as in the case of the above-described unevenness. A metal layer 7 of Al or the like is deposited on the uneven layer by a vacuum evaporation method, a sputtering method, or the like, and these are referred to as a back reflection layer. A transparent electrode layer 3 made of tin oxide, ITO, or the like is formed on the metal layer of the back reflection layer.
[0033]
On the transparent electrode layer 3, an a-Si photoelectric conversion layer 4 including an n-type sub-layer, an i-type sub-layer, and a p-type sub-layer (not shown) sequentially formed is formed. On the Aa-Si photoelectric conversion layer 4, a transparent electrode layer 5 made of ITO or the like and a comb-shaped current collecting metal electrode layer 8 made of Ag or the like are laminated. It is needless to say that in the photoelectric conversion device as shown in FIG. 2, light enters the photoelectric conversion layer 4 via the comb-shaped metal electrode layer 7 and the transparent electrode layer 3.
[0034]
It goes without saying that the photoelectric conversion device obtained above can be used not only for solar cells but also for various other uses such as optical switches and optical sensors.
[0035]
【The invention's effect】
Advantageous Effects of Invention According to the present invention, a photoelectric conversion element and a photoelectric conversion device having a light confinement layer that can suppress more surface reflection, allow more light to enter the substrate, and efficiently confine the incident light within the substrate And a solar cell having high photoelectric conversion efficiency provided with the device.
The light confinement layer in the present invention uses an existing electron beam exposure apparatus to create a cell structure composed of the concavities and convexities that constitute the light confinement layer. Etc. can be arbitrarily and easily processed. Further, it is also possible to form a light confinement layer on one surface of the substrate by emboss replication technology.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing a photoelectric conversion device as one embodiment of the present invention.
FIG. 2 is an explanatory diagram illustrating a solar orbit in each season.
FIG. 3 is a schematic perspective view showing an uneven layer corresponding to a solar orbit.
FIG. 4 is an explanatory diagram illustrating a minute cell structure.
FIG. 5 is a schematic sectional view showing a photoelectric conversion device as another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Substrate 2 Uneven layer 3 Transparent conductive layer 4 Semiconductor photoelectric conversion layer 5 Transparent conductive layer 6 Metal electrode layer 7 Comb-shaped metal electrode

Claims (5)

In a light confinement layer having irregularities of a predetermined shape used for a photoelectric conversion device,
A photoelectric conversion element having a light confinement layer, wherein a light confinement layer having a cell composed of lattice-like irregularities as a constituent unit is arranged over substantially the entire surface of a substrate. 2. The photoelectric conversion device having a light confinement layer according to claim 1, wherein the cell constituent unit forming the light confinement layer includes a cell having a curved lattice-like unevenness. The photoelectric conversion element having a light confinement layer according to claim 1, wherein the grating pitch is in a range of 5 to 500 μm, and the height of the unevenness is in a range of 0.5 to 2 μm. A first electrode layer, a semiconductor photoelectric conversion layer, and a second electrode layer formed on a substrate are included in this order, and the light confinement layer is disposed between the substrate and the semiconductor photoelectric conversion layer. Characteristic photoelectric conversion device. A solar cell having the photoelectric conversion device according to claim 4,
The solar cell has a structure fixed to the ground without changing its direction, and the cells forming the light confinement layer included in the photoelectric conversion device are selected and arranged corresponding to the solar orbit with season or time. A solar cell having a configuration.

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