JPH054825B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a photovoltaic device having a printed thin film CdS/CdTe structure that can be used as a solar cell, particularly as a power source for indoor consumer equipment.

BACKGROUND OF THE INVENTION Recently, photovoltaic elements have been actively developed using various manufacturing methods in order to manufacture low-cost solar cells. Among them, one of the methods for manufacturing photovoltaic elements having a CdS/CdTe structure is a manufacturing method using screen printing and firing in a belt conveyor furnace. This method is characterized by a simple manufacturing process, high productivity in mass production, and the ability to obtain inexpensive solar cells.

With reference to the drawings below, the conventional
An example of a photovoltaic device having a CdS/CdTe structure will be described.

FIGS. 2A to 2D are a plan view and a cross-sectional view of a solar cell manufactured by screen printing and belt furnace firing.

First, a CdS sintered film 2 is manufactured by applying a CdS layer to a transparent substrate 1 such as a glass substrate by screen printing and firing it in a belt conveyor furnace. Next, a CdTe layer with a desired pattern is applied onto this CdS sintered film 2 by the same screen printing method and fired in a belt conveyor furnace to form a CdTe sintered film 3. On top of this, a CdTe sintered film 3 is placed.
At the same time as molding, a carbon paste that is in ohmic contact with the CdTe sintered film 3 is printed in a desired pattern, and a carbon film 4 is obtained by heat treatment.
Form a CdS/CdTe heterojunction. Further, an AgIn electrode 5 in ohmic contact with the CdS sintered film 2 and an Ag electrode 6 on the carbon film 4 were formed by screen printing and conveyor furnace firing to produce a solar cell element.

In the stacking of the plurality of films, the CdS sintered film 2 and the AgIn electrode 5, that is, the negative electrode,
When the carbon film 4 and the Ag electrode 6, ie, the positive electrode, come into contact, a short circuit occurs and the photoelectric characteristics deteriorate. On the other hand, the photovoltaic current generating portion is a portion where the CdS film 2 and the CdTe film 3 on which the carbon film 4 is printed overlap. This portion is called the effective light-receiving area. The effective light-receiving area is as wide as possible, and
Traditionally, CdTe was used as a printing pattern to prevent the above short circuit.
The size of the film 3 was designed to be equal to or smaller than the CdS film 2, and the carbon film 4 was designed to be smaller than the CdTe film 3.

Problems to be Solved by the Invention However, in the above-mentioned printing pattern configuration, the CdS film 2
There is a possibility that the carbon film 3 comes into contact with the carbon film 3. One way to prevent this is to make the carbon film 4 much smaller than the CdTe film 3, but the above-mentioned effective light-receiving area decreases accordingly. That is, the photovoltaic power characteristics per area of the glass substrate are reduced.

In view of the above problems, the present invention prevents contact between the CdS film 2 and the carbon film 4 due to printing misalignment and oozing of the carbon film, and reduces leakage current without causing a decrease in the effective light-receiving area that contributes to photoelectric conversion. The present invention provides a photovoltaic element with significantly reduced energy consumption.

Means for Solving the Problems In order to solve the above problems, in the photovoltaic device of the present invention, the CdTe film, which is the second film, covers all of the CdS film, which is the first film, except for the electrode portion. cover, and a third film, a carbon film, is a second film.
CdS that does not protrude from the CdTe film and is the first film
It is made to be equivalent to or larger than this to correspond to the membrane.

Effect The present invention has the above-described structure in which the n-type semiconductor film CdS, which is the first film, is covered with the p-type semiconductor film, which is the second film, so that printing of the carbon film, which is the third film, is possible. Contact between the CdS film and carbon film due to shearing or oozing is greatly reduced, improving the characteristic yield. Furthermore, since the p-n junction interface is not exposed around the device except for the CdS electrode portion, the interfacial recombination current is also reduced and reliability is improved. Furthermore, the effective light-receiving area is increased and the characteristics are also improved. As a result, under low illuminance conditions such as indoors, a reduction in leakage current leads to a significant improvement in characteristics.

Embodiment A photovoltaic device according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1A is a plan view of a photovoltaic device according to an embodiment of the present invention, and B, C, and D of FIG.
Each cross-sectional view taken along line D' is shown.

On a barium borosilicate glass substrate 1 with an alkali content of 0.3% by weight or less, 10% by weight of CdCl ₂ powder was added as a flux to CdS powder by screen printing method.
Using CdS paste, prepare the substrate 1 as shown in Figure 1.
Apply a CdS layer leaving a margin around the periphery and heat at 120℃ for 60 minutes.
After drying for several minutes, put it in an alumina firing container and fire it in a belt-type firing furnace at a firing temperature of 690℃ for about 1 hour.
A CdS sintered film 2 was formed. On this CdS fired film 2
Using a CdTe printing paste made by adding 0.5% by weight of CdCl ₂ powder to Cd powder and Te powder, a pattern is created that covers everything except the electrode part of the CdS film 2, including the side surfaces of the CdS film 2 and the substrate. of
After coating the CdTe layer and drying, place it in an alumina firing container and fire it in a belt-type firing furnace at a temperature of 580°C.
Baked for an hour. Using a screen printing method, a carbon paste containing an appropriate amount of acceptor impurities was applied to the CdTe sintered film 3 formed in this way, so that it did not protrude beyond the CdTe film 3 as shown in the figure.
In correspondence with CdS film 2, a carbon layer was applied in a pattern that was equal to or larger than this film. Thereafter, a carbon film 4 was formed by heat treatment at 400° C. for 30 minutes in an N ₂ atmosphere, and at this time, acceptor impurities contained in the carbon were diffused into the CdTe film. Next, 20% by weight was applied onto the CdS sintered film 2.
Using Ag paste containing In powder of
An ohmic electrode was formed on the CdS sintered film by heat treatment for 40 minutes. Further, Ag paste was also applied on the carbon film 4 and dried at 150° C. for 30 minutes to form an Ag electrode 6.

As described above, according to this example, the CdTe film
By covering everything except the electrode portion of the CdS film, contact between the carbon film and Ag electrode and the CdS film can be prevented, and photovoltaic characteristics can be improved by reducing leakage current. In addition, short circuits due to printing misalignment and paste oozing during mass production are reduced, improving production yield. Furthermore, the size of the carbon film
By making it equal to or higher than the CdS film, the effective light-receiving area can be increased compared to the conventional one, and the photoelectric conversion characteristics can also be improved.

Effects of the Invention As described above, the present invention provides a CdTe film as a second film.
The film covers everything except the electrode part of the CdS film, which is the first film, and the carbon film, which is the third film, does not protrude from the CdTe film and is equivalent to or better than the CdS film. By having a structure that is
Characteristics are improved by reducing leakage current and increasing the effective light-receiving area, and in addition, production yield during mass production can also be improved.

[Brief explanation of the drawing]

FIG. 1A is a plan view of a photovoltaic device according to an embodiment of the present invention, and FIG. 1B, C, and D are lines BB' of A;
Cross-sectional views along lines C-C' and D-D', Figure 2A
are plan views of conventional photovoltaic elements;
These are cross-sectional views taken along lines B-B', C-C', and D-D' of A. 1...Glass substrate, 2...CdS film, 3...
CdTe film, 4... Carbon film, 5... AgIn electrode,
6...Ag electrode.

Claims (1)

[Claims] 1. A first film made of an n-type compound semiconductor containing CdS or Cd, S formed on a substrate, and CdTe or Cd, Te formed on this first film.
a second film made of a compound semiconductor containing In a sintered film type CdS/CdTe photovoltaic device consisting of a formed electrode, the second film covers everything except the electrode part of the first film, including the side surface of the first film and the substrate. 3. A photovoltaic element characterized in that the film of No. 3 does not protrude from the second film and has a size equal to or larger than that of the first film other than the electrodes of the first film. 2. The photovoltaic power according to claim 1, wherein the third film is obtained by printing and firing a paste containing conductive carbon as a main component and adding an element that acts as an acceptor impurity to the second film. element.