JPH03196681A - Photovoltaic device - Google Patents

Abstract

PURPOSE:To restrain lowering of photovoltaic characteristics due to leaving of a device at a high temperature for a long time and to improve heat resistance by containing common Al as a constituting material to conducting paste and a rear electrode which are electrically connected by applying an energy beam. CONSTITUTION:A device is composed of a translucent insulating substrate 1, photosensitive electrodes 2a to 2c, conducting pastes 3a to 3c, insulating pastes 4a to 4c, semiconductor films 5a to 5c, rear electrodes 6a to 6c and unit power generating elements SC1 to SC3. As a constituting material of the conducting pastes 3a to 3c and the rear electrodes 6a to 6c which constitute series connection of the unit power generating elements SC1 to SC3, common Al is contained. Adhesion between the conducting pastes 3a to 3c and the rear electrodes 6a to 6b is improved by containing common Al as a constituting material thereof. Thereby it is possible to restrain lowering of photovoltaic characteristics due to leaving of the device at a high temperature for a long time and to improve heat resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to a photovoltaic device used for solar power generation and the like.

(b) Conventional technology By forming a plurality of unit power generation elements on a light-transmitting insulating substrate and electrically connecting the plurality of unit power generation elements to each other in series, it is possible to A photovoltaic device with an output voltage is obtained. As such a series connection form, there is a method in which the light-receiving surface 1 on the substrate side constituting one adjacent unit power generation element is made to extend from the effective power generation area to the pole and the back electrode of the other unit power generation element and are directly coupled to each other. Are known(
(See Japanese Patent Publication No. 62-14954).

However, according to this series connection form, it is necessary to pattern the semiconductor film of the unit power generation element by photolithography in order to expose the light-receiving surface electrode in the adjacent interval part where the series connection is performed. Patterning by otolithography not only hinders the increase in the area of the photovoltaic device, but also requires many steps, which is not preferable for cost reduction.

Therefore, in order to realize a larger area and lower cost, the applicant of the present application proposed a method using a laser beam in a patent application filed in 1986-17.
No. 3684 (Japanese Unexamined Patent Publication No. 62-33477) was filed. That is, a conductive paste is applied to the light-receiving surface where the poles are planned to be connected in series, and an insulating paste is applied parallel to and close to the conductive paste. The semiconductor film including the electrode is formed over the entire surface of the substrate, and then the back electrode is formed to cover the entire surface of the semiconductor film. Finally, a laser beam is irradiated from the back electrode side to the area where the conductive paste and insulating paste are located in the lower layer under low energy density irradiation conditions, welding the back electrode and the conductive paste, and insulating the paste. On the paste, the back electrode and the semiconductor film are physically divided for each unit power generating element.

In such a connection structure, conventionally, Ag paste is often used as the conductive paste, and Al is often used as the back electrode.

However, in a connection structure using Ag paste and an Al back electrode, if the photovoltaic device is exposed to high temperatures for a long time, the Al back electrode at the connection part is likely to be oxidized, increasing the connection resistance and adversely affecting the photovoltaic characteristics. It turned out to give.

Such oxidation of the A2 back electrode is particularly significant when the degree of welding by the laser beam is low. Therefore, if the energy density of the laser beam is increased in order to obtain strong welding, there is a problem that the laser beam will destroy the conductive paste and even the lower layer light-receiving surface electrode.

(c) Problems to be Solved by the Invention The present invention, as described above, uses a conductive paste suitable for increasing the area and reducing costs and welding by energy beam irradiation as a series connection form of unit power generating elements. This aims to solve the problem that photovoltaic properties deteriorate when exposed to high temperatures for a long period of time.

(d) Means for Solving the Problems The present invention arranges a plurality of unit power generating elements each consisting of a laminate of a light-transmitting light-receiving surface electrode, a semiconductor film, and a back electrode on a light-transmitting insulating substrate, and one The light-receiving surface of the unit power generating element is electrically connected to the area where the conductive paste partially provided between the pole and the semiconductor film and the extension of the back electrode extending from the other unit power generating element are opposed by irradiation with an energy beam. In order to solve the above problems, the 4-electrode paste and the back electrode are made of a common A as their constituent material.
It is characterized by containing l.

(E) Function As described above, the conductive paste and the back electrode, which are electrically coupled by irradiation with an energy beam, improve their adhesion by including Al as a common constituent material.

(f) Embodiment FIG. 1 shows the main parts of an embodiment of a photovoltaic device according to the present invention, in which (1) is a transparent insulating substrate made of glass or the like, (2a), (2b) , (2c) is ITO15n O
A light-receiving surface electrode made of a single layer or a laminate of a translucent conductive oxide (TCO) represented by
After being formed on the entire main surface of , it is divided into rectangular shapes by irradiation with a laser beam to form individual unit power generation elements.

The divided patterning of the light-receiving surface electrodes (2a), (2b), and (2C) is performed over a large area, for example, several IQcn+X several tens (1
It is particularly effective for the above devices, but 10cmXIQ
For devices on the order of cm or less, photolithography may be used. (3a), (3b), and (3c) are conductive pastes formed in a stringer shape along one adjacent opposing side of the light-receiving surface electrodes (2a), (2b), and (2c); 3a), (3b), and (3C) are made of Ag paste containing Al as a constituent conductive material. (4a), (4b), and (4C) are the above conductive pastes (
3a), (3b), and (3C), in parallel to the light-receiving surface electrodes (2a), (2b), and (2C) with an insulating paste such as 5ins paste provided on the inside of the adjacent opposing sides of the electrodes. Base) (4a), (4b), (4c) and conductive paste (3a), (3b), (3C) are applied to a film thickness (height) of about 10 to 20 pm by screen printing method, and heated at about 550°C. Fired.

(5a), (5b), and (5c) are the light-receiving surface electrodes (2a).
), (2b), and (2c), and has a single junction or tandem junction structure with pin and pn semiconductor junctions inside, and is preferably formed by plasma CVD method or the like, which can be applied to a large area. Film thickness number 1 formed by photo-CVD method
Although it is composed of an amorphous silicon-based semiconductor film with a thickness of 1,000 pm to several pm, it may be a polycrystalline silicon semiconductor or even a cadmium-based semiconductor such as CdS.

(6a), (6b), (6c) -F article conductor film (5a)
), (5b), (5c) stacked on At or A
The back electrode has a single layer structure of I1 alloy or a multilayer structure with layers of other conductive materials, and the light receiving surface electrode (2a) when viewed from the light incident side.
, (2b), (2c), semiconductor film (5a), (5b),
(5c) and the back electrodes (6a), (6b), (6c) unit power generation element (SCI), (SC,)
, (SC,) are constructed. And such a unit power generating element (S
CI), (SC1), (SCI) are the above-mentioned conductive pastes (3a), (3b), (3c) and insulating pastes (4a)
, (4b), (4c) and light-receiving surface electrodes (2a), (2b
), (2C) and a stack of semiconductor films and back electrodes formed entirely on the -main surface side of the insulating substrate (1),
As disclosed in the prior art, an energy beam such as a laser beam or an electron beam is applied to the conductive paste (3a), (3b).
, (3c) on the back electrodes (6a), (6b), (6c) of one unit power generating element (SC,), (SC,), (SCs) and the other unit. The light-receiving surface electrodes of the emitting elements (SC,), (SC1)... are electrically coupled, and the insulating pastes (4a), (4b)
), (4c)''- is irradiated with a high energy beam from the conductive paste and the semiconductor film and back surface t are deposited on the entire surface.
The laminated body of fi is each individual unit power generating element (SC,), (S
CI) and (SC3) are physically separated, and as a result, they are connected in series as shown in FIG.

Therefore, the structural feature of the present invention is that the unit power generating element (SCI)
), (SCI), (SC,) and the conductive pastes (3a), (3b), (3c) and the back electrode (6
A2 common as the constituent material of a), (6b), and (6c)
It is to include. That is, the conventional bonding between the Ag paste and the Al back electrode by welding had poor adhesion, which led to an increase in connection resistance due to oxidation at the contact portion of the Al back electrode in high-temperature reliability tests. However, conductive paste (3a
), (3b), (3c) by using a conductive material containing A2, the back electrodes (6a), (6b), (6
c) Adhesion is improved. Therefore, connection resistance can be reduced.

Furthermore, the present inventors have developed Al back electrodes (6a), (6b),
(6c) and eight! Conductive paste of Ag paste containing (
3a), (3b), and (3c) were subjected to a high-temperature reliability test at 90°C, and the Al content was 5 Wt%.
In this case, after about 200 hours, the FFf fill factor) decreased, and after 100 hours, it became 50% of the cutting property (after aging). However, A110wt%
The containing Ag paste had values equivalent to the initial characteristics even after 1000 hours. Nao, eight! In the case of Ag paste that does not contain, the FF decreases after about 100 hours,
It decreased to 50% in about 700 hours. Therefore, in the case of Ag paste, 1. It has been found that deterioration of properties is particularly suppressed when the Al content is about 10 wt% or more.

On the other hand 1. As mentioned above, when the Al content is about 10 wt% or more, the deterioration of characteristics due to high temperature can be suppressed, but when the Al content increases, the conductive paste (3a), (3
b), (3C) and TCO light-receiving surface electrodes (2a), (2b
), the contact resistance with (2c) increases, impairing the photovoltaic properties. This phenomenon becomes remarkable when the Al content exceeds that of Ag, which has low resistance. Therefore, the Al content is preferably less than 50wt%, more preferably 30wt% or less, even more preferably 20wt% or less.

(Effects of the Invention) As is clear from the above explanation, by including Al as a common constituent material of the conductive paste and the back electrode, the adhesion between the two is improved, so that the photovoltaic properties of the conductive paste and the back electrode are improved by leaving them at high temperatures for a long time. It is possible to provide a photovoltaic device that can suppress deterioration and has excellent heat resistance.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional perspective view showing essential parts of an embodiment of the photovoltaic device of the present invention.

Claims (1)

[Claims] (1) A plurality of unit power generation elements each consisting of a laminate of a light-transmitting light-receiving surface electrode, a semiconductor film, and a back electrode are arranged on a light-transmitting insulating substrate, and the light-receiving surface electrode and semiconductor film of one unit power generation element are A photovoltaic device in which a conductive paste partially provided between the opposing parts and an extension part of a back electrode extending from the other unit power generation element are electrically coupled by irradiation with an energy beam, A photovoltaic device characterized in that the conductive paste and the back electrode contain Al as a common constituent material.