JPS6250069B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a photovoltaic device using an amorphous semiconductor. As this type of device, a photovoltaic device is already known in which a plurality of mutually independent amorphous semiconductor layer regions are provided on a substrate and adjacent regions are electrically connected in series to each other over their adjacent opposing widths. . The structure of such a device is extremely preferable because it can output any electromotive voltage and can reduce series connection resistance. The present invention aims to improve the power conversion efficiency of the above device. The figure shows an embodiment of the present invention, in which 1 is a transparent insulating substrate such as glass; 2a, 2b, 2c are first electrodes arranged in a predetermined direction on the substrate; 3a, 3;
b, 3c are amorphous semiconductor layers deposited on the first electrodes 2a, 2b, 2c, respectively; 4a, 4b, 4c are second amorphous semiconductor layers deposited on the amorphous semiconductor layers 3a, 3b, 3c, respectively. The electrode 5 is an insulating film that tightly surrounds the laminate of the first electrode, the amorphous semiconductor layer, and the second electrode from the second electrode side. Each of the first electrodes and each of the second electrodes adjacent thereto have extension portions 10 and 11 that extend in the arrangement direction across each adjacent opposing full width L,
They are overlapped and connected at the extension. The first electrode has translucency and is made of tin oxide, indium oxide, indium tin oxide (In ₂ o ₃ +xsno ₂ ,
X≦0.1), and the second electrode is made of aluminum, chromium, or the like. Each of the amorphous semiconductor layers 3a, 3b, and 3c has a laminated structure of first, second, and third power generation layers 31, 32, and 33. In the above device, when light enters each power generation layer via the substrate 1 and the first electrode, free carriers (electrons and/or holes) are generated within each layer, and these are collected at the opposing first and second electrodes. A voltage is generated between the two electrodes. At this time, the second electrode 4a on the left and the first electrode 2b on the center, the second electrode 4b on the center and the first electrode on the right
The electrodes 2c are electrically connected, so that the electromotive voltages between the opposing electrodes are added in series. Furthermore, if a configuration consisting of a pair of first and second electrodes and an amorphous semiconductor layer interposed between these electrodes constitutes one power generation area, each power generation area 12
The smaller the series resistance between a, 12b, and 12c is, the better; however, in the solar cell according to the embodiment of the present invention, the adjacent first and second electrodes have an extension extending in the above arrangement direction over the entire width L of the adjacent opposite electrodes. Since the power generating sections 10 and 11 are connected in an overlapping manner, the series resistance between the power generating sections can be reduced without the current between the sections concentrating on one part. As a feature of the present invention, the optical band gaps Eop of the first, second, and third power generation layers 31, 32, and 33 stacked in the light incidence direction are sequentially set from the light incidence side as shown in FIG. It's getting smaller. To explain more specifically, the specific configurations of the first to third power generation layers are as shown in the table below.

[Table] In other words, in each power generation layer, the power generation function is mainly performed in the respective I-type layer, but as mentioned above, the first I-type layer I ₁ and the second I-type layer are laminated sequentially from the light incident side. Optical bandgap Eop of each of I ₂ and the third I-type layer I ₃
is decreasing in order of 2.0ev, 1.75ev, and 1.3ev. In the semiconductor power generation phenomenon, the wavelength of incident light that contributes to power generation, that is, the absorption wavelength, depends on the optical forbidden band width of the power generation region. FIG. 3 shows the first,
The light absorption characteristics 31a, 32a, 33a of the second and third power generation layers 31, 32, 33 are shown. If a power generation element has only one optical bandgap and sunlight, etc. is incident on such an element, only light of a part of the wavelength corresponding to the optical bandgap will contribute to power generation. First, incident light energy with a shorter wavelength becomes heat and dissipates within the element, and incident light energy with a longer wavelength is dissipated without being absorbed within the element. On the other hand, in this embodiment, as is clear from FIG. 3, there are multiple optical forbidden band widths when looking at the element as a whole, and since the arrangement is such that the optical band widths become smaller sequentially from the light incidence side, the incident light energy The short wavelength side effectively contributes to power generation in a relatively shallow area of the element, and the long wavelength side goes to a relatively deep area of the element without being absorbed in the shallow area of the element. As a result of making an effective contribution, a large power generation efficiency can be obtained as a whole of the element. If a single crystal material is used to laminate multiple power generation layers with different optical band gaps as in this example, there will be problems of crystal lattice mismatch between each power generation layer and problems between adjacent power generation layers. , seen in Figure 1,
Between the first N-type layer _N1 and the second P-type layer _P2 , between the second N-type layer _N2 and the second P-type layer P2.
This is difficult to realize because a rectifying junction in the opposite direction, such as with the 3P type layer _P3 , occurs. However, when an amorphous semiconductor material is used as in this example, the above-mentioned mismatch of crystal elements does not occur at all, and the amorphous semiconductor can be formed to an extremely thin film thickness. By making the thickness of the film in the portion where such a reverse rectifying junction is likely to occur very thin as in the embodiment, a tunnel current flows and the junction in that portion hardly becomes a substantial rectifying junction. For example, the manufacturing of the above embodiment can be carried out using the first electrodes 2a, 2
Put the substrate 1 prepared up to b and 2c into the reaction chamber,
This is carried out by appropriately filling the reaction chamber with a reaction gas to generate glow discharge. Each power generation layer 3
Since the compositions of Nos. 1, 32, and 33 are different from each other, it goes without saying that the reaction gases are changed in the order of stacking. The table below shows the composition of the reactive gas for each layer. Note that the substrate 1 is maintained at a temperature of 250° C. during the formation of all layers.

[Table] In addition, the reaction gas includes other carrier gases.
Contains _H2 gas. In addition, as a method for mass production, the individual reaction chambers for forming each of the layers are arranged in close proximity in the order in which the layers are formed, and the reaction chambers are separated by shutters, and the substrate 1 is separated from each of these chambers. All layers can be formed in assembly line by successive passes. As another embodiment, the first, second, and third I-type layers
An internal electric field may be additionally formed within each layer by gradually decreasing the optical band gap Eop of each of I 1 , I ₂ , and _{I 3 in} the direction of incident light within each layer.
Such an internal electric field promotes the movement of free carriers generated by light irradiation within each I-type layer, suppresses recombination annihilation, and further increases efficiency. The formation of the first I-type layer I ₁ was carried out by starting from the initial 10% of the reactive gas composition NH ₃ /SiH ₄ +NH ₃ in the first embodiment and gradually changing it to a final 5% as the film grows. In this case, Eop is 2.0eV
It varies from 1.8eV to 1.8eV. The formation of the second I-type layer I ₂ is
The substrate temperature in the above first embodiment was set to 180°C.
It is sufficient to start at ℃ and gradually change it to a final temperature of 300℃ as the film grows. In this case, Eop is 1.8eV.
It varies from to 1.7eV. The formation of the third I-type layer I ₃ is
The reaction gas composition in the first example above is SnCl ₄ /
SiH ₄ +SnCl ₄ may be started from the initial 1% and gradually changed to a final 20% as the film grows, and in this case Eop changes from 1.6 eV to 1.1 eV. 3rd I
With such a change in the type layer I ₃ , the reaction gas composition for the formation of the third N-type layer N ₃ is SnCl ₄ /SiH ₄ +SnCl ₄ =
20%, PH ₃ /SiH ₄ +SnCl ₄ = 1%, and at this time Eop becomes 1.1 eV. As yet another embodiment, in order to completely eliminate the reverse rectifying junction that exists between adjacent first, second, and third power generation layers 31, 32, and 33, the first, _{N +} ^_
Furthermore, the region near the start of growth of the second and third P-type layers P ₂ and P ₃ (the region with a thickness of 20 to 30% of each layer) may be made into P ⁺ type. As is clear from the above description, according to the present invention, a plurality of first electrodes are arranged on an insulating substrate, and an amorphous semiconductor layer is individually and sequentially deposited on each of the first electrodes. In a photovoltaic device including a first electrode and a second electrode, the adjacent first and second electrodes are connected to each other in an overlapping manner so as to extend in the above alignment direction over their adjacent opposing widths, the photovoltaic device has properties unique to an amorphous semiconductor. A highly efficient photovoltaic device can be realized by forming the power generation layer into a laminated structure.

[Brief explanation of the drawing]

FIG. 1A is a perspective view of a main part of an embodiment of the present invention, FIG. 1B is an enlarged sectional view of the same, FIG. 2 is an energy band structure diagram,
FIG. 3 is a diagram of light absorption characteristics. 31, 32, 32...first, second, and third power generation layers.

Claims (1)

[Claims] 1 A plurality of first electrodes arranged on an insulating substrate, an amorphous semiconductor layer and a second electrode individually and sequentially deposited on each of the first electrodes, and adjacent first and second electrodes. The photovoltaic device is a photovoltaic device in which two electrodes are connected to each other in an overlapping manner so as to extend in the arrangement direction over their adjacent opposing widths. First, second, and third power generation layers sandwiched by N-type impurity layers are laminated in the direction of light incidence, and each I in the power generation layer is laminated in the direction of light incidence.
In order to gradually reduce the optical bandgap width of the type layer from the power generation layer side in the light incident direction, the first I type layer is made of amorphous silicon nitride, the second I type layer is made of amorphous silicon, and the third I type layer is made of amorphous silicon. 1. A photovoltaic device made of crystalline silicon tin, and further characterized in that the thickness of the I-type layers is gradually increased from the power generation layer side in the direction of light incidence.