JPH06314814A - Photovoltaic device and color sensor - Google Patents

Abstract

PURPOSE:To enable selective detection of a wavelength without using a color filter. CONSTITUTION:An element of a short wavelength contained in light injected to a photosensitive region is converted to an electric signal in a photovoltaic semiconductor layer 13 immediately below it. An element of a long wavelength repeats scattering or reflection in the semiconductor layer 13, is propagated in a surface direction, that is, in a lengthwise direction, and is absorbed in the semiconductor layer 13 in a light screening region. Therefore, an electric signal in accordance with light of a short wavelength is picked up from a rear electrode 14a, and an electric signal in accordance with a long wavelength is picked up from a rear electrode 14b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic device and a color sensor to which the photovoltaic device is applied.

[0002]

2. Description of the Related Art A conventional color sensor uses a color filter for wavelength selection.

[0003]

The conventional color sensor that uses a color filter to select a wavelength has a problem that not only the cost increases but also the element becomes large due to the filter. Therefore, the main object of the present invention is to provide a novel photovoltaic device.

Another object of the present invention is to provide a color sensor which is inexpensive and can be made compact.

[0005]

According to a first aspect of the present invention, there is provided a substrate, a photovoltaic semiconductor layer formed on the substrate and having a light confining effect, and at least two mutually-excited electrical layers formed on the photovoltaic semiconductor layer. A photovoltaic device having electrically independent electrodes, in which light is blocked from entering a portion of the photovoltaic semiconductor layer corresponding to at least one of the at least two electrodes.

A second invention is a color sensor using such a photovoltaic device.

[0007]

When light enters or is reflected by an uneven interface having a size similar to that of the wavelength, light undergoes scattering and is incident or reflected at an angle larger than that calculated from the refractive index. Spread laterally. Of the light incident from the non-shielded region, that is, the light receiving region, a component having a relatively short wavelength, such as 400 to 600 nm, is absorbed relatively quickly due to the large absorption coefficient of the photovoltaic semiconductor layer, and is converted into electric energy. To be converted. On the other hand, a component having a long wavelength of 700 nm or more has a small absorption coefficient of the photovoltaic semiconductor layer, and therefore a part of the component is shielded from the light receiving region while being reflected on the front surface or the back surface of the photovoltaic semiconductor layer. To a region where it is absorbed and converted into electrical energy. The electric energy converted in the light receiving region is individually taken out by the electrode corresponding to the portion, and the electric energy converted in the light shielding region is taken out individually by the electrode corresponding to the portion. That is, since at least two electrodes are electrically independent from each other, they can be independently extracted as an electric signal for each wavelength.

[0008]

According to the present invention, a novel photovoltaic device can be obtained. Further, in the optical sensor to which this photovoltaic device is applied, since it is not necessary to use the color filter, the cost can be reduced and the size can be reduced. The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A photovoltaic device 10 of the embodiment shown in FIGS. 1 and 2 includes a glass substrate 11 on which a transparent electrode 12 such as tin oxide is formed. At this time, the surface of the transparent electrode 12 is formed to be a slightly rough surface by, for example, chemical or plasma etching so that a light confining effect described later can be obtained. Then, on this transparent electrode 12, a photovoltaic semiconductor layer 1 made of amorphous silicon or a compound thereof having a pin junction.
3 is formed. This photovoltaic semiconductor layer 13 is formed by, for example, a known plasma CVD method.

On the other hand, on the light receiving surface side of the glass substrate 11, a light shielding film 15 made of, for example, metal or synthetic resin is formed so as to form a light receiving region and a light shielding region. Then, on the photovoltaic semiconductor layer 15, the electrodes 1 electrically isolated from each other are provided in the portions corresponding to the light receiving region and the light shielding region, respectively.
4a and 14b are formed. The electrodes 14a and 1
4b uniformly forms an electrode film on the semiconductor layer 13 by vacuum evaporation of silver, for example, so that a portion corresponding to the light receiving region and a portion corresponding to the light shielding region are electrically insulated.
For example, it can be formed by patterning with a laser beam.

In the photovoltaic device 10 shown in FIG. 1, when light is incident on the light receiving region, the light is received by the glass substrate 11.
And is incident on the transparent electrode 12. At this time, since the transparent electrode 12 has the uneven surface having a size of 1 μm or less as described above, light having a wavelength of, for example, several 100 nm is
The uneven surface of the transparent electrode 12 scatters and advances to the photovoltaic semiconductor layer 13 so as to spread in all directions.

The thickness of the photovoltaic semiconductor layer 13 is, for example, 1
It is 500 Å, and high reflectance is realized by using silver as the electrodes 14a and 14b. Therefore, the semiconductor layer 1
The light reaching the back surface of 3 is reflected with almost no loss and travels to the front surface side of the semiconductor layer 13, that is, the light incident side. The light thus reflected on the back surface and further reaching the front surface is scattered or reflected at the interface between the semiconductor layer 13 and the transparent electrode 12, and travels again into the semiconductor layer 13. Therefore, the light is trapped in the semiconductor layer 13 and repeatedly scattered or reflected until it is converted into electric energy.

Of the light incident from the incident surface, for example, 4
A component having a relatively short wavelength such as 00 nm to 600 nm is absorbed by the semiconductor layer 13 before being reflected on the back surface of the semiconductor layer 13 or when it is reflected once or twice, and converted into electric energy. On the other hand, a component having a long wavelength of 700 nm or more is reflected by the semiconductor layer 13 more times before being sufficiently absorbed, and as a result, the light is 1 μm in the plane direction (lateral direction).
Propagated over m. Therefore, the electrodes 14a and 14
If the interval of b is about 1 μm, the electric energy obtained by the short wavelength component is the electrode 14a, that is, the output terminal O1.
The electric energy obtained by the long wavelength component is extracted from the electrode 14b, that is, the output terminal O2. Therefore, such a photovoltaic device 10
When synthetic light including light of two or more kinds of wavelengths is incident on, the signal extracted from the electrodes 14a and 14b causes
As a result, the wavelength can be identified.

The photovoltaic device 20 of the embodiment shown in FIG.
Unlike the photovoltaic device 10 of the forward type structure of FIG. 1, it has an inverted type structure. The photovoltaic device 20 includes a substrate 21 such as stainless steel, which substrate 21
The reflective electrode 22 is formed thereon by, for example, vacuum evaporation of silver. This reflective electrode 22 also has an uneven surface with a size of 1 μm or less, like the transparent electrode 11 of FIG.
Then, a photovoltaic semiconductor layer 23 made of, for example, amorphous silicon or a compound thereof having a pin junction is formed on the reflective electrode 22. A transparent electrode 24 made of, for example, indium tin oxide is formed on the semiconductor layer 23. On the transparent electrode 24, collecting electrodes 25a and 25b are formed independently in the light receiving region and the light shielding region, respectively.
Although the light-shielding region is formed by the collecting electrode 25b, the light-shielding member 26 may be further attached to the collecting electrode 25b if necessary.
You may make it formed on b.

In the photovoltaic device 20 of this embodiment, the light is incident from the side opposite to the substrate 21, but the light is confined in the photovoltaic semiconductor layer 23 as in the embodiment of FIG. Depending on the wavelength, different collecting electrodes 25a and 25b, that is, output terminals O1 and O2, are taken out as electric signals. In the embodiment of FIG. 3, an electrode in which zinc oxide / silver / zinc oxide is laminated on tin oxide may be used in order to increase the reflectance on the back surface of the semiconductor layer 23.

The photovoltaic device 30 of the embodiment shown in FIG.
Similar to the embodiment shown in FIG. 3, it is a so-called reverse type,
In this embodiment, quartz is used as the substrate 31, and the metal electrode 32 is formed thereon. The metal electrode was formed by vacuum deposition of titanium, for example. As this electrode, a titanium / silver / titanium three-layer structure having higher conductivity may be used.

Thereafter, by patterning this metal electrode with, for example, a laser beam, an electrode 32a is present in a portion corresponding to the light receiving region, an electrode 32b is present in a portion corresponding to the light shielding region, and they are electrically connected to each other. Insulated. After that, an amorphous silicon film is formed by using, for example, a plasma CVD method, and then thermal annealing is performed in vacuum at 500 to 700 ° C.
A photovoltaic semiconductor layer 33 made of polycrystalline silicon having a grain size of about μm is formed. At this time, JP-A-62-193287 [H01L31 / 0] filed by the applicant of the present application
4], the photovoltaic semiconductor layer 33 made of polycrystalline silicon is formed under the conditions as shown in FIG.
An uneven surface having a size of μm or less is formed. At this time, the thickness of the semiconductor layer 33 is about 2000Å.

After that, a transparent electrode 34 made of, for example, tin oxide is formed, and a collector electrode 35 is formed thereon. The portion not covered with the collecting electrode 35 becomes the light receiving area, and the portion covered with the collecting electrode 35 becomes the light shielding area. Further, the light blocking member 36 may be used in order to ensure the light blocking by the collector electrode 35. In the photovoltaic device 30 of this embodiment, since polycrystalline silicon is used for the photovoltaic semiconductor layer 33, the light-receiving region and the light-shielding region around the light-receiving region are electrically connected due to the relationship between the light absorption coefficient and the conductivity. The spacing between the insulating portions can be made larger than that when amorphous silicon is used, which is advantageous in design. However, in this embodiment, crystal growth from amorphous silicon to polycrystalline silicon was realized by thermal annealing, but it goes without saying that well-known laser recrystallization technology using an excimer laser or the like may be used. Absent.

Further, the metal electrodes 32a and 32b may be formed by depositing a refractory metal material such as tungsten in addition to titanium. Photovoltaic device 30 shown in FIG.
In the case of the transparent electrode 34,
Through the photovoltaic semiconductor layer 34 made of polycrystalline silicon
Component having a short wavelength is absorbed by the light receiving region of the semiconductor layer 33 before being scattered, but the component having a long wavelength repeatedly scatters or reflects and reaches a light shielding region around the light receiving region. There, it is absorbed by the semiconductor layer 33.
Therefore, an electrical signal corresponding to the short wavelength component is extracted between the metal electrode 32a and the transparent electrode 34, that is, the output end O1, and an electrical signal of the long wavelength component is output between the metal electrode 32b and the transparent electrode 34, that is, the output end O2. Is obtained.

The photovoltaic device 40 shown in FIG. 5 has a forward type structure as in the embodiment of FIG. This example
It differs from the embodiment of FIG. 1 in the following points. That is, FIG.
A photovoltaic semiconductor layer 43 made of microcrystalline silicon is used in place of the photovoltaic semiconductor layer 13 of the embodiment, and a semiconductor layer 44 made of amorphous silicon or microcrystalline silicon having an ip junction is further formed thereon, for example, plasma C.
It is formed using the VD method. Then, the back surface electrodes 45a and 45b are formed by vacuum vapor deposition of silver, for example. In this embodiment, reference numeral 46 indicates a light blocking member.

In this embodiment, a transistor structure composed of a pinip is formed, and therefore, an appropriate bias is provided between the photovoltaic semiconductor layer 43 and the transparent electrode 42 or between the photovoltaic semiconductor layer 43 and the back electrode 45b. When the voltage B1 or B2 is applied, even a smaller amount of light can be detected, and a photosensor with higher sensitivity can be realized.

However, a similar transistor structure may be formed in the photovoltaic device 30 of the FIG. 4 embodiment. Figure 6
The photovoltaic device 50 shown in is a modification of the embodiment shown in FIG.
That is, in the light receiving area in the embodiment of FIG.
The n-structure is adopted, and the above-mentioned transistor structure is adopted in the light-shielding region.

According to this embodiment, drive power can be obtained by photoelectric conversion in the light receiving area, and control signals can be taken out in the light shielding area. In this way, the supply of drive power and the transmission of control signals can be achieved simultaneously with the same light. Therefore, according to this FIG. 5 embodiment, it is possible to control the power supply and the operation thereof in a small mechanical device by one device.

In any of the above embodiments,
Although the photovoltaic semiconductor layer has a pin structure from the substrate side, it goes without saying that a laminated structure having an opposite conductivity type can be formed by the same process and the same effect can be obtained. When a polycrystalline semiconductor layer is used, it may have a pn structure.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention.

FIG. 2 is an illustrative view showing the embodiment of FIG. 1 in plan view.

FIG. 3 is a schematic sectional view showing another embodiment of the present invention.

FIG. 4 is a schematic sectional view showing still another embodiment of the present invention.

FIG. 5 is a schematic sectional view showing still another embodiment of the present invention.

FIG. 6 is a schematic sectional view showing another embodiment of the present invention.

[Explanation of symbols]

10, 20, 30, 40, 50 ... Photovoltaic device 11, 21, 31, 41, 51 ... Substrate 12, 24, 34, 42, 52 ... Transparent electrode 13, 23, 33, 43, 53 ... Photovoltaic Semiconductor layers 44, 54 ... Semiconductor layers 14a, 14b, 32a, 32b, 45a, 45b, 5
5a, 55b ... Back surface electrode 15, 26, 36, 46, 56 ... Shading member 25a, 25b, 35 ... Collection electrode

Claims (3)

[Claims] 1. A substrate, a photovoltaic semiconductor layer formed on the substrate and having a light confinement effect, and at least two electrically independent electrodes formed on the photovoltaic semiconductor layer, A photovoltaic device in which light is blocked from entering a portion of the photovoltaic semiconductor layer that corresponds to at least one of the at least two electrodes. 2. A substrate, a photovoltaic semiconductor layer formed on the substrate and having a light confinement effect, and at least two electrodes electrically isolated from each other formed on the photovoltaic semiconductor layer. And a color sensor in which light is blocked from entering a portion of the photovoltaic semiconductor layer corresponding to at least one of the at least two electrodes. 3. The photovoltaic device or color sensor according to claim 1, wherein at least the light-shielding region of the photovoltaic semiconductor layer has a transistor structure.