JPS6148796B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photovoltaic device, and particularly to a photovoltaic device in which a large number of photovoltaic elements are connected in series on a substrate.

The photovoltaic voltage of a single photovoltaic element using a pn junction of semiconductor material is small at about 0.3 to 1.0V, and in order to drive devices such as watches and calculators, a large number of these elements are connected in series. It is necessary to use an electromotive force device.

The structure of a photovoltaic device conventionally used for this purpose is shown in FIG. A printed circuit board 3 in which a silicon single crystal with a pn junction formed thereon is cut and divided into desired shapes, and an element 1 is wired with copper foil 2.
The upper comb-shaped electrode 4 of the silicon single crystal element is connected to the copper foil 2 of the adjacent element using lead wires 5 by bonding or soldering. By repeating this process, a photovoltaic device in which a large number of silicon single crystal elements were connected in series was obtained. However, when manufacturing this device, cutting each silicon single crystal element, fixing each element to the printed circuit board 3,
Furthermore, it is necessary to connect the individual elements using lead wires 5, which requires a lot of labor and time, resulting in high costs.

On the other hand, a conventional structure of a photovoltaic device using a thin film semiconductor is shown in FIG. On a transparent substrate 7 such as glass, on which a transparent electrode 6 such as In ₂ O ₃ or SnO ₃ film is formed in a desired pattern, n is deposited by vapor deposition or vapor phase growth.
A p-type semiconductor material 8 is formed in a pattern in which the elements are separated from each other, and a p-type semiconductor material 9 is formed thereon in a pattern in which the elements are also separated from each other, so that a plurality of independent
Forms a pn junction. In order to connect the plurality of elements in series, a metal 10 that is in ohmic contact with the p-type semiconductor 9 is formed by vapor deposition, thereby connecting the transparent electrode 6 and the p-type semiconductor 9, respectively. In this case, the electrode 10 and the n-type semiconductor 8 of each element must not be in contact with each other, and the p-type semiconductor 9 and the transparent electrode 6 must not be in contact with each other. This is necessary to prevent short-circuiting of the pn junction, and as shown in Figure 2, the device component material close to the transparent substrate is formed on top of the material to cover the components necessary for the device configuration. It is necessary to form one after another. As a final step, the elements are connected in series using the p-type semiconductor electrode 10 to produce a photovoltaic device. Indeed, even between elements connected in series, for example, the transparent electrode 6 and the n-type semiconductor 8 of the adjacent element must not come into contact, and the p-type semiconductor 9 and the p-type semiconductor electrode 10 of the adjacent element must not come into contact. must not. This is because each element does not work as a series connection, but works as a parallel connection. As described above, in a photovoltaic device using a thin film semiconductor, it is necessary to form many layers in a narrow space between the elements one after another by shifting their positions to avoid short circuits. When forming on a substrate, alignment of pattern forming masks when forming each constituent material is important, and this operation requires manpower and time. In addition, such a divided structure is necessary for separating the photoelectric conversion operations of the elements and for connecting them in series, but the area between the elements is not useful as an area for producing the photoelectric conversion effect of the elements. , the effective light-receiving area will be reduced. When incorporated into a calculator, watch, etc., if such a portion is present in the area exposed to light, the effective power generation amount will be reduced.

The present invention has been made to improve these drawbacks, and the manufacturing process is simplified and made more effective by using a plurality of first films and a second film provided in common with the first films. It is an object of the present invention to provide a photovoltaic device with an increased light-receiving area.

The present invention will be explained below along with examples using the drawings.

FIGS. 3a and 3b are a structural sectional view and a plan view showing an embodiment of the photovoltaic device of the present invention.

First, by screen printing on the glass substrate 11.
A patterned CdS layer 12 is formed using a CdS paste made by adding 10 wt% CdCl ₂ to CdS powder containing 0.1 mol% Ga. This is placed in an alumina boat and fired in a belt conveyor furnace at a temperature of 690°C for approximately 1 hour.
Bake for an hour. The CdS film thus obtained is an n-type semiconductor with a film thickness of approximately 25 μm, a crystal grain size of 10 to 15 μm, and a specific resistance of approximately 0.5 Ω·cm in the lateral direction of the film.
A strip-shaped CdTe layer 13 is formed on this patterned CdS layer 12 by screen printing. CdTe layer 1
3 has 6w% CdCl ₂ added and is similar to the CdS mentioned above.
Firing is carried out in the same manner as layer 12. In this case, the firing temperature is 680°C and the firing time is about 20 minutes. The CdTe layer 13 obtained in this way has a thickness of 15 to 20 μm.
m, crystal grain size 8-10μm, lateral specific resistance of the film approx.
It is a p-type semiconductor with a resistance of 10 ³ Ω・cm. This band-shaped CdTe
The part where the layer 13 and the patterned CdS layer 12 are in contact is a pn junction and is where a photovoltaic effect is generated. Carbon paste was printed in a predetermined pattern on this CdTe layer 13, and
After heat treatment for 1 minute, each patterned CdS layer 12
The carbon electrode 14 is formed to correspond to the above.
In order to connect this carbon electrode 14 and the CdS layer 12, an In electrode 15 is deposited between the ends of each photovoltaic element to connect the part of the carbon electrode 14 located on the substrate 11 and the part not covered by the CdTe layer 13. A photovoltaic device in which CdS/CdTe photovoltaic elements are connected in series is manufactured by connecting a part of the CdS layer 12. in this case
The CdS layer 12 also functions as an electrode layer. p-type
The electrode on the CdTe layer 13 side may be made of any material such as Cu ₂ Te/Au, Ni, etc. as long as it works as an ohmic electrode.On the other hand, the electrode on the CdS layer 12 side may be formed by printing such as Ag paste added with In powder. An ohmic electrode may also be used.

Using the method described above, CdS/CdTe with a light-receiving area of approximately 1 cm ² was
We manufactured a photovoltaic device with eight photovoltaic elements connected in series, and the characteristics of this device were: open circuit voltage 3.4 to 4.0 V, short circuit current 25 to 35 μA, maximum under 500 lux white fluorescent light. It was possible to obtain a power of 60 to 80 μW. This value was almost the same as the characteristics of a photovoltaic device having the structure shown in FIG. 2 manufactured by a similar method, and the characteristics were not adversely affected by forming the CdTe layer 13 in a band shape.

To explain the reason for this, consider a case in which the photovoltaic device shown in FIGS. 3a and 3b is simplified and consists of two photovoltaic elements as shown in FIG. 4.

First, let R ₁ be the resistance in the thickness direction of element A, that is, between the CdS layer 12 and the opposing carbon electrode 14, and the lateral resistance occurring between the CdS layer 12 of element A and the carbon electrode 14 of element B. Let it be R ₂ . The dimensions of the carbon electrode are ω×l, the distance between the CdS layers 12 is t ₂ , and the thickness of the CdTe layer 13 is t ₁ . ω, l, t ₁ , t ₂ of the element that obtained the above output characteristics
The values are 1.6 cm, 0.6 cm, 20 μm, and 0.5 mm, respectively. Now assume that the specific resistance of the CdTe layer 13 is ρ, which is the same value in both the vertical and horizontal directions.

Here, when R ₁ and R ₂ are calculated, R ₁ =ρt ₁ /ωl. On the other hand, for R ₂ , the relationship t ₂ ≫ _{t 1} holds, so R ₂ =
It becomes ρt ₂ /ωt ₁ . Therefore, when finding the ratio of R ₂ /R ₁ ,
R ₂ /R ₁ = t ₂ l / t ₁ ² , and by substituting the above values,
It becomes R ₂ /R ₁ 10 ⁴ . Therefore, even if the CdTe layer 13 is formed into a strip, almost no current flows between the elements A and B, and they function in the same way as when they are separated. It is now assumed that the specific resistance of the CdTe layer 13 is the same value in the vertical and horizontal directions. However, in the horizontal direction, since the CdTe film is polycrystalline, the effect of grain boundaries is strong, and the resistivity tends to be larger than that in the vertical direction, so the actual ratio of R ₂ / R ₁ is likely to be even larger. Seem.

As is clear from the above results, the effectiveness of the photovoltaic device of the present invention is limited not by the differences in the types of n-type and p-type semiconductors or their manufacturing methods, but by the differences in the materials constituting the device. Because of the mutual arrangement and film thickness, the present invention can be widely applied to cases where semiconductor materials are manufactured using other semiconductor materials and other manufacturing methods. In addition, as shown in Figure 3b, the electrodes that connect the elements can be formed at a position farther away from the junction, so there is less reduction in the light-receiving area, and this has the effect of eliminating short circuits during connection and adverse effects on the junction that occur when forming the electrodes. There is also. Furthermore, it helps to simplify the device structure and improves reliability and yield.

In this example, the CdS sintered film is used as both a bonding material and an electrode material, but even if the structure shown in Figure 2 used to explain the conventional example is used, that is, an n-type semiconductor is formed on a transparent electrode, there will be no problem at all. Similarly, the p-type semiconductor formed thereon may be formed into a band shape. Furthermore, the same effect can be obtained even if the p-type semiconductor is separated and the n-type semiconductor is formed into a band.

As is clear from the above description, the photovoltaic device of the present invention has the following effects.

(1) Since a large number of photovoltaic elements are simultaneously formed on a substrate, the manufacturing process is simplified and the device can be manufactured at low cost.

(2) When forming a photovoltaic device with separate elements on a substrate, it is necessary to gradually shift the positions of many element constituent materials in the narrow space between the elements to prevent short-circuits between the elements and short-circuits between the elements. Therefore, it is important to align the patterns. However, in the case of the present invention, one semiconductor material forming a pn junction may be a band-shaped material common to all other semiconductor materials, so short circuits as described above are less likely to occur, and pattern alignment is difficult. Errors are reduced, the manufacturing process is simplified, and yields are improved.

(3) When used as a power source for watches, calculators, etc.
Since there is no part on the light irradiation surface that does not contribute to power generation as in the conventional case, that is, a part where the element constituent materials are gradually shifted in order to prevent short circuits between elements or short circuits between elements, the power generation per the same light receiving surface is reduced. The amount increases.

(4) The above-mentioned portions that do not contribute to power generation are not aesthetically pleasing because the two types of semiconductor materials and metals are visible from the incident light surface side, but in the present invention, the second layer common to multiple first films Because of the membrane, the above-mentioned parts are softened and the aesthetic appearance is not spoiled.

(5) The electrode that connects the elements can be formed on one main surface of the substrate away from the junction, so that the effective light-receiving area is less reduced, and highly reliable electrodes can be easily formed.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a conventional photovoltaic device using a silicon single crystal, Fig. 2 is a cross-sectional view of a conventional photovoltaic device using a thin film semiconductor, and Fig. 3 a and b are a cross-sectional view of a conventional photovoltaic device using a silicon single crystal. A structural sectional view and a plan view showing one embodiment of the electromotive force device, and FIG. 4 is a simplified configuration diagram of the photovoltaic device for explaining the present invention. 11...Glass substrate, 12...CdS layer, 13...
...CdTe layer, 14...Carbon electrode, 15...In
electrode.

Claims (1)

[Claims] 1 A plurality of first films made of a semiconductor material of one conductivity type formed on one main surface of a substrate; and a plurality of first films made of a semiconductor material of a conductivity type opposite to the one conductivity type; A second film commonly provided on the plurality of first films except for a part of the film, and a second film provided on the second film corresponding to each of the plurality of first films. a plurality of first electrodes formed over one main surface of the substrate; a partial region of the adjacent first film installed on the one main surface of the substrate; A photovoltaic device comprising: second electrodes each connecting a portion of the electrode located on one principal surface of the substrate.