JPH01175774A - Manufacture of solar cell with self-contained reverse current blocking diode - Google Patents

Abstract

PURPOSE:To enable a solar cell which is small, thin and inexpensive and has a high reliability to be produced, by a method wherein a reverse current blocking diode and a CdS/CdTe type thin film solar cell are formed on a common substrate simultaneously or successively, and so forth. CONSTITUTION:A sinter-type solar cell is produced which comprises a first film into which an n type semiconductor which is a cadmium sulfide or contains it is spread on a transparent substrate 1 and then sintered, and a second film 3 into which a p type semiconductor which is a cadmium telluride or contains it is spread on the part of the first film 2 other than the exposed part of the first film 2 and then sintered. Further, after conductive third films 5 and 4 are spread simultaneously on side exposed part of the first film 2 and the second film 3, respectively, sintering is performed, and thereby the electrode of the solar cell and a reverse current blocking diode are formed on the second and first films 3, 2, respectively. For example, said first film 2 and said third films 5, 4 forming the diode are formed by the film into which the paste, in which 50-1000ppm copper oxide is dispersed in carbon paste, is spread and thereafter sintered at 350-500 deg.C.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a method for manufacturing a solar cell with a built-in backflow prevention diode when the solar cell is used for charging a secondary battery such as a storage battery. .

Background of the Invention In recent years, solar cells have been widely used as power sources for electronic devices.
ing. If the device is used only under a lighting source such as a calculator, it is sufficient to connect the load directly to the solar cell, but as a power source for an electronic device such as a watch that operates continuously regardless of the presence or absence of light irradiation. When using a solar cell, it is necessary to use a combination of a secondary battery or a high-capacity capacitor with the solar cell.

In other words, the electricity generated during light irradiation is charged to a secondary battery, etc., and when there is no light or the light is too weak to directly drive the equipment with solar cells, the charged secondary battery supplies electricity to the equipment. This is because it is required to do so. but,
At this time, current also flows in the forward direction from the secondary battery to the solar cell, causing current loss. Therefore, a diode (hereinafter referred to as a backflow prevention diode) that prevents the backflow of stored electricity to the solar cell is generally installed between the secondary battery and the solar cell. For example, FIG. 2 shows a circuit diagram of a crystal oscillation electronic watch that uses solar cells. A coin type secondary 7I battery 11 and a solar cell 8 are connected in parallel to an electronic watch circuit 13 serving as a load.
In between, a backflow prevention diode 1o is provided with rectifying properties in the direction shown in the figure, and is wired in series with the protective resistor 9. The solar cell and backflow prevention diode are manufactured in separate processes.
This means that the components are wired onto the wiring board of the electronic device.

In recent years, especially as the power consumption of electronic devices has decreased, the number of electronic devices that use a power source that combines a solar cell and a secondary battery is increasing. Therefore, it has become necessary to mount a backflow prevention diode on the wiring board, which is unnecessary when using negative batteries.

Problems to be Solved by the Invention However, the above configuration requires a space for mounting the diode, which not only poses a problem in making electronic equipment smaller and thinner, but also because the solar cell and the diode are mounted separately. The cost increases due to the increase in assembly man-hours. Further, during mounting, problems tend to occur in which the resistance of the diode and solar cell is set to be opposite to the predetermined combination. Furthermore, there is also the problem that deterioration troubles in the binding portion during use tend to have a large effect on reliability.

In view of the above-mentioned problems, the present invention is designed to simultaneously form a thin film solar cell on a substrate on which a thin film solar cell is formed.

Alternatively, the present invention provides a method for manufacturing a highly reliable solar cell with built-in backflow prevention, which is manufactured by directly connecting a single-film type backflow prevention diode to a solar cell.

Means for Solving the Problems In order to solve the above problems, the present invention provides a method for manufacturing a solar cell with built-in backflow prevention on a common substrate.

A backflow prevention diode and a CdS/CdTe type thin film solar cell are formed simultaneously or sequentially, and at this time, at least one of the constituent materials of the thin film type backflow prevention diode is replaced with the constituent material of the solar cell. It was used in common with

Operation The present invention utilizes the above-mentioned structure, and utilizes the characteristics that the electrode material that can obtain ohmic contact with the p-type conductor CdTe has a high work function and exhibits rectifying properties with respect to the n-type semiconductor CdS. , At the same time as electrode formation on the CdTθ film, a rectifying diode with CdS as n-type is formed on the CdS film in the negative electrode formation portion simultaneously or successively by coating and sintering, similar to the formation of solar cells. As a result, it is possible to manufacture a solar cell with built-in backflow prevention that is small, thin, inexpensive, and highly reliable.

EXAMPLE Hereinafter, a method for manufacturing a solar cell with a built-in backflow prevention diode according to an example of the present invention will be described with reference to the drawings. FIG. 1 shows the manufacturing process of a solar cell with a built-in backflow prevention diode in an embodiment of the present invention. First, the formation of a CdS sintered film and a CdTe sintered film, which are constituent materials of a solar cell, will be explained. Add 10% by weight of Cd C/2 as a flux to high-purity CdS powder with a particle size of several microns.
Propylene glycol: add 30-4oM amount of Cd
Make S paste and apply it on glass substrate 1 as shown in Figure 1a.
It was printed in the predetermined pattern shown below. After drying this in a dryer kept at a temperature of 120'C for 1 hour, it was placed in an alumina firing container and fired at a temperature of 90'C in a belt type firing furnace.
It was sintered for about 1 hour. On this CdS sintered film 2, C(i
A printing paste in which 30 to 40 wt% of C (IC/2 powder and propylene glycol) was added to the powder and Te powder was partially exposed on the CdS sintered film 2 shown in Fig. 1. After drying this at 100'Q for 30 minutes, it was placed in an alumina firing container and fired at a temperature of 620'C in a belt-type firing furnace.
The film was sintered for 1 hour to form a CdTe sintered film 3. Carbon paste 4.6 is applied in a predetermined pattern shown in FIG. Printed. Naori-Bon paste contains ca'
ra'f: 1100 pp of copper oxide was added as an acceptor to make it p-type. After applying carbon film, 120
'C for 1 hour and fired at a temperature of 4 using a belt firing furnace.
Sintering was carried out at 00°C for 1 hour. Next, paste was applied onto the carbon film 5 on the CdS sintered film and on the carbon film 4 on the C(ITθ sintered film 3) in a predetermined pattern shown in FIG. By drying for 30 minutes, a mug electrode 6 was formed.

Carbon-C which is a conductor-semiconductor contact in the above structure
Whether the dS film or carbon-CdTe film contact exhibits ohmic contact or rectification is determined by the difference between the work function of carbon and the work function of the semiconductor. Carbon work function φm =5. Oe V, C(Is work function φ14
= 4.4315 V, work function φB of CdTa
"' 4.50 eV. Generally, between a conductor and an n-type semiconductor, φm>φS exhibits rectifying properties, and φkcφ8 exhibits ohmic characteristics. Furthermore, between a conductor and a p-type semiconductor, the opposite characteristics are exhibited. Therefore, the carbon to p-type CdTe contact is φ.

〉Because it is φS, it has ohmic characteristics, and carbon-n
Since φm>φS, the type CdS contact exhibits rectifying properties. That is, a CdS/CdTe solar cell can be formed in which a backflow prevention diode exhibiting rectification is connected to the negative electrode CdS.

Figure 3 shows the copper oxide concentration in the carbon paste at 50 ppm.
14, 1000ppm 15. 2000
1)1)m 16. The diode characteristics of cas7 carbon are shown when the pH is changed to 5000pph117. It can be seen that by increasing the copper oxide concentration in carbon, Cu diffusion occurs in the CdS film, and as the CdS film resistance increases, the rise of the diode characteristics becomes gradual. On the other hand, it is known that the copper oxide concentration in the carbon and the firing temperature have a great influence on the characteristics of CdS/CdTe solar cells.
It was determined that the calcination temperature was 0 ppH and the calcination temperature was 350'C to 500C.

From Figure 3, the voltage vF at which the forward current begins to flow is approximately 0.
It is 3v.

The maximum output of a CdS/CdTe solar cell is at an operating voltage of 0.
Since the voltage is 46V, it can be seen that the backflow prevention diode does not have any particular effect when charging the secondary battery from the solar battery. It was found that by connecting six solar cells with the above configuration in series using the final A[electrode], even if a terminal voltage of 1.6 V was applied from the secondary battery side, no discharge would occur through the solar cells.

As described above, according to this embodiment, a carbon film, which is an electrode of a CdTe film of a Gas/CdTe solar cell formed by a coating sintering method, is simultaneously formed on Cds by coating and sintering, thereby forming a solar cell. A solar cell with a built-in connected thin film anti-backflow diode can be formed without any special process.

Next, a second embodiment of the present invention will be described.

After forming a Cds+CdTe sintered film in the same manner as in the first example, unlike the first example, carbon 11 was replaced with Cds+CdTe.
It was formed only on the Ta sintered film. Next, only on the exposed (ds sintered film) was a pattern similar to that shown in Fig.
3μm Ni! ! A conductive paste consisting of a resin and a solvent containing 2ON of an N1-containing compound was completely printed, and 150
Dry at °C for 30 minutes. Next, on the carbon film and on the Ni
Electrodes were formed by printing mug paste on the v and drying it at 150'C for 30 minutes. Work function φH of N1
=5.2 eV, and exhibits rectifying properties compared to n-type CdS. In the CdS/Ni diode formed with the above configuration, the voltage vr at which forward current begins to flow was approximately 0.35 V.

As described above, after forming an electrode on the p-type CdTe p of the coated and sintered CdS/CdTa solar cell, Ni and Ni compound films are printed and fired on the n-type CdS sintered film in a separate process. By doing so, it is possible to manufacture a backflow prevention diode in series connection with a solar cell using a material and processing conditions different from the Ca're electrode material.

In addition, when copper paste is used as the electrode material formed on the CdTθ film in the second embodiment, the firing temperature is 150'C, which is lower than the firing temperature of the N1 film, which is 150'C.
Even if the above Ni was printed and fired first, the desired performance was not achieved.

Effects of the Invention As described above, the present invention provides a coated sintered Can/CdTe
This is a manufacturing method in which a thin-film backflow prevention diode is coated on a substrate on which a thin-film solar cell is formed, either simultaneously or in succession with the thin-film solar cell, and then connected to the solar cell by baking. It is possible to provide error-free and highly reliable solar cells with built-in backflow prevention.

[Brief explanation of the drawing]

Fig. 1 is a manufacturing process diagram of a solar cell with a built-in backflow prevention diode according to the first embodiment of the present invention, Fig. 2 is a circuit diagram of a crystal excavation type electronic watch using a solar cell, and Fig. 3 is a manufacturing process diagram of a solar cell with a built-in backflow prevention diode according to the first embodiment of the present invention. FIG. 3 is a diagram showing the characteristics of the backflow prevention diode when the CuO concentration in the carbon film is changed in the first example. 1... Glass substrate, 2... Cds sintered film, 3... cd're sintered film, 4...
Carbon film (on CdTθ film), 5... Carbon film (on Cds film), 6... Mug electrode, 8...
...Solar cell, 9...Resistance, 10...
・Backflow prevention diode, 11...Silver oxide battery,
12... Light, 13... Electronic watch circuit, 14... Cu concentration 50 ppm, 15-
・-・Cu g degree 10ooppm116・old・・aug
degree 200oppm, 17---Cu concentration 50o
Oppm. Name of agent: Patent attorney Toshio Nakagishi and 1 other person1-
・Glass substrate 6...-Act switch Fig. 2 Fig. 3

Claims (4)

[Claims] (1) A first film made by coating and sintering cadmium sulfide or an n-type semiconductor containing it on a transparent substrate, exposing a part of this first film, and coating cadmium telluride or it on other films. A sintered solar cell is formed with a second film coated and sintered with a p-type semiconductor containing a p-type semiconductor, and the exposed first film is
By coating a conductive third film on the second film and the second film at the same time and baking it, a solar cell electrode can be formed on the second film and a backflow prevention diode can be formed on the first film. 1. A method for manufacturing a solar cell with a built-in anti-backflow diode, characterized in that: (2) The first film and the third film forming the diode are formed by applying a paste containing 50 to 1000 ppm of copper oxide dispersed in carbon paste and then baking it at 350 to 500°C. A method for manufacturing a solar cell with a built-in backflow prevention diode as described in . (3) A first film made by coating and sintering cadmium sulfide or an n-type semiconductor containing it on a transparent substrate, and exposing a part of this first film and disposing cadmium telluride or an n-type semiconductor containing it on other films. A sintered solar cell is formed with a second film coated with a p-type semiconductor and sintered, and a second film is formed on the second film.
A conductive third film that forms a diode with the first film is applied and fired on the exposed first film before or after forming an electrode that can make ohmic contact with the film. A method for manufacturing a solar cell with a built-in anti-backflow diode. (4) The third film forming the diode with the first film is N
2. The method for manufacturing a solar cell with a built-in backflow prevention diode according to claim 1, wherein a paste made of a compound containing i or Ni, a resin, and a solvent is applied and fired.