JPH09321325A - Cds/cdte solar cell and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a CdS/CdTe solar cell having a low cost and stable performance and a manufacturing method thereof. SOLUTION: The CdTe film forming material uses a film formed by printing a fine powder contg. Cd and Te on a heat resistive support 12; the powder is obtained by pulverizing Cd and Te or CdTe compd. It is heated into vapor to form a CdTe film on a CdS film, thus forming a CdS/CdTe solar cells. Thus it is possible to produce a CdS/CdTe solar cell at low cost with stable performance.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a CdS / CdTe
The present invention relates to a solar cell and a method for manufacturing the same, and in particular to Cd.
The present invention relates to a CdTe film forming material when a proximity sublimation method is used as a Te film forming method.

[0002]

2. Description of the Related Art In recent years, as global environmental problems such as global warming due to carbon dioxide and destruction of the ozone layer have been highlighted, expectations for new energy development, especially for early commercialization of solar cells, have been increasing. There is. However, many problems still remain to be solved for the early commercialization of solar cells. In particular, improvement of conversion efficiency and cost reduction of solar cells are important issues that cannot be avoided.

Under such circumstances, the CdS / CdTe solar cell has 1.4eV, which is close to the optimum forbidden band width as a light absorption layer.
CdTe is used and is expected as one of the favorite of high efficiency solar cells.

The method for producing a CdS / CdTe solar cell is as follows:
Although various methods have been tried, the proximity sublimation method is drawing attention as a method capable of forming a high-quality CdTe film and producing a highly efficient solar cell. TL for proximity sublimation
Chu et al., "HIGH EFFICI-ENCY CdS / CdTe SOLAR CELL
S FROM SOLUTION-GROWN CdS FILMS ": The Conference
Record of the 22nd IEEE Photovoltaic Specialists
Technically disclosed in Conference (1991) Vol.2, p952, etc., but in brief description, a substrate on which CdTe is deposited has a gap of about 1 to 2 mm with respect to a CdTe film forming material (hereinafter referred to as a source). It is a method of forming a CdTe film on a substrate by opening and bringing them close to each other and heating them under a reduced pressure atmosphere to sublime the source. Further, in this document, as a source material, commercially available CdT having a purity of 5N is used.
It is described as an e-polycrystal or a CdTe polycrystal obtained by directly synthesizing a constituent element and a dopant.

[0005]

Conventionally, in the proximity sublimation method, it has been a general method to spread CdTe powder as a sauce in a dish-shaped container and use it. However, the cost of CdTe powder is low, and the material utilization efficiency is low because the rest of the material must be discarded because the material deteriorates after the film has been formed several tens of times. There was a problem in aiming for Further, when exchanging the source, the vacuum film forming apparatus has to be vented and exposed to the atmosphere, which is time-consuming and, for example, in the case of mass production of this, the operating rate is lowered. Furthermore, there is a problem that the performance of the solar cell varies due to the source changing with time.

The present invention solves the above problems and provides a material for forming a CdTe film which is inexpensive and can form a stable CdTe film.

[0007]

In order to solve these problems, the present invention provides, as a material for forming a CdTe film, Cd and Te alone or CdTe on a support having heat resistance.
CdTe having a bonding interface with a CdS film by using a film printed with a fine powder containing at least Cd, Te obtained by pulverizing a compound and vaporizing it by heating
It is a CdS / CdTe solar cell which formed the film.

As a method of manufacturing the above-mentioned solar cell, Cd and Te alone or CdT are provided on a heat-resistant support.
A step of printing a fine powder containing at least Cd and Te obtained by crushing the e compound to obtain a CdTe film forming material, a substrate on which the CdTe film forming material, a transparent conductive film and a CdS film are sequentially formed. Step of arranging closely and facing each other, the Cd
Cd in which a Te film forming material is vaporized by heating and arranged in pairs
And a step of depositing CdTe on the S film.

By this means, it is possible to manufacture a CdS / CdTe solar cell with low cost and stable performance.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A CdS / CdTe solar cell according to the present invention is a substrate on which a transparent conductive film and a CdS film are sequentially formed, and a Cd and Te simple substance or a CdTe compound is ground on a support having heat resistance. Obtained at least Cd,
CdS / CdT obtained by arranging films printed with fine powder containing Te in close proximity to each other, vaporizing the films as a material for forming a CdTe film, and depositing CdTe on the CdS film.
e It is a solar cell. As the material for forming the CdTe film,
The use of inexpensive Cd and Te simple substances as starting materials has the merit of reducing the material cost. Further, by printing the amount of the source required for one film formation, the material utilization efficiency is improved. In addition, since the source is exchanged for each film formation, there is no variation in the performance of the solar cell due to the aging of the source, and stable CdS / C performance is achieved.
It becomes possible to manufacture dTe solar cells. As the support having heat resistance, a plate-shaped carbon material is excellent because of its uniform heat distribution and small heat capacity, but it is preferable to use a glass substrate in terms of price and ease of handling. Also, these supports can be used cyclically.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention and its manufacturing method will be described with reference to the drawings.

FIG. 1 shows CdS / Cd according to an embodiment of the present invention.
3 shows a cross section of a Te solar cell. 1 is a glass substrate, 2 is IT
A transparent conductive film such as O or SnO2 having a film thickness of 200 to 500
μm, 3 is a CdS film, the film thickness is 50 to 150 μm, 4 is a CdTe film, 5 is a carbon film which is an electrode for the CdTe film, 6 is an AgIn film which is an electrode for the CdS film, 7
Is an Ag film which is a current collector. The method of forming the CdTe film 4 which is the feature of the present invention in the structure of FIG. 1 will be described in more detail.

First, in the method of manufacturing a material for forming a CdTe film, Cd powder and Te powder are used as starting materials. These prices are about 20 yen per gram, which is significantly lower than the price of CdTe powder of about 250 yen. This C
The d powder and the Te powder were added in equimolar amounts and pulverized in water using a medium stirring mill to a particle size of about 1 μm or less. After that, take out the crushed powder, and after drying, add this fine powder to
Propylene glycol was added as a binder and kneaded to prepare a paste. This paste was printed on a carbon plate having a thickness of 1 mm and dried at 120 ° C. for 1 hour to evaporate the binder to obtain a printed film. When the composition of the printed film was examined by X-ray diffraction, diffraction peaks of Cd simple substance, Te simple substance and CdTe were observed. It is considered that this CdTe was synthesized by crushing energy during crushing.

Next, the printed film / carbon plate is opposed to the glass / ITO / CdS substrate so as to have a gap of 2 mm, and is set in a quartz tube 8 as shown in FIG. Form the membrane. Glass / I
On the TO / CdS substrate 9, a thickness of 1 mm as a soaking body
Place the carbon plate 10 of. The film forming procedure is as follows.
The inside of the quartz tube 8 is evacuated by the rotary pump 11, and then argon gas is introduced to keep the pressure at 1 to 5 Torr. The glass / ITO / CdS substrate 9 and the printed film / carbon plate source 12 are respectively provided with upper and lower lamp heaters 13.
The temperature of the source 12 is 600 to 630 ° C., the temperature of the substrate 9 is 58.
Heat to 0-600 ° C and hold for 1 minute. During this time Cd
A CdTe film is formed on the S film. After cooling, the CdTe sintered film on the carbon plate is almost gone,
The thickness of the CdTe film formed on the CdS film was 6 μm.

After forming the CdTe film, CdC is formed on the CdTe film.
coating a methanol saturated solution of l _2, after evaporation of the methanol, 400 ° C., and the CdTe and heat-treated for 30 minutes to improve the crystallinity of the film is grain growth. Then Cd
Carbon film as Te electrode, Ag as CdS electrode
An In film was formed and a solar cell was produced. When the characteristics of the obtained solar cell were measured under a solar simulator of AM 1.5, 100 mW / cm ² , a short circuit current was 23.5 mA.
/ Cm ² , open circuit voltage 0.813V, fill factor 0.69
6. Characteristics of a solar cell with a conversion efficiency of 13.3% and a CdTe powder dish-shaped container laid as a source (short-circuit current 23.4 mA / cm ² , open-circuit voltage 0.815).
V, fill factor 0.701, conversion efficiency 13.4%), and similar performances were obtained.

Next, a second embodiment will be described. First,
This is a method for producing a material for forming a CdTe film, and when propylene glycol was added as a binder to the pulverized powder described above and kneaded, an appropriate amount of CdCl ₂ was added as a melting point depressant to prepare a paste. This paste was printed on a 1 mm thick carbon plate and dried at 120 ° C. for 1 hour to evaporate the binder to obtain a printed film. When the composition of the printed film was examined by X-ray diffraction, Cd simple substance, Te simple substance, CdTe
In addition to the diffraction peak of CdCl _2, a peak of CdCl ₂ was naturally observed. After the printed film was formed, it was baked in a nitrogen atmosphere at a temperature of 600 ° C. to 700 ° C. for 1 hour to obtain a CdTe sintered film. This Cd
Only the X-ray diffraction peak of CdTe was observed from the Te sintered film. Next, the CdTe sintered film / carbon plate is opposed to the glass / ITO / CdS substrate so as to have a gap of 2 mm, set in the apparatus used in the first embodiment, and the same procedure as in the first embodiment. With CdTe on CdS film
A film was formed. After forming the CdTe film, CdTe is formed on the CdTe film.
After coating a saturated solution of Cl ₂ in methanol and evaporating the methanol, heat treatment was carried out at 400 ° C. for 30 minutes to cause grain growth of CdTe to improve the crystallinity of the film. Then, C
Carbon film as dTe electrode, A as CdS electrode
A gIn film was formed and a solar cell was produced. The characteristics of the obtained solar cell were measured under a solar simulator of AM 1.5, 100 mW / cm ² to find that a short circuit current was 23.6.
mA / cm ² , open-circuit voltage 0.816V, fill factor 0.6
99, conversion efficiency 13.5%, characteristics of a solar cell prepared as a source by laying it in a conventional CdTe powder dish-shaped container (short circuit current 23.4 mA / cm ² , open circuit voltage 0.81
5V, fill factor 0.701, conversion efficiency 13.4%) and similar performance was obtained.

In the above embodiment, Cd as the starting material,
Although Te alone was used, similar results were obtained using a commercially available CdTe compound.

As described above, as the material for forming the CdTe film, any of a simple substance of Cd and Te or a fine powder obtained by crushing a CdTe compound, which is printed and dried, or a film obtained by sintering the fine powder is used. I found it usable.

Next, regarding the correlation between the number of CdTe film formations and solar cell characteristics, when CdTe powder was spread as a source in a dish-like container and not replaced (conventional example), a film on which fine powder was printed was prepared for each CdTe film formation. A comparative experiment was carried out when the present invention was used after being replaced with the present invention.

FIG. 3 shows a change in conversion efficiency when a solar cell was prototyped 50 times. CdT as the source
e When the powder was spread in a dish-shaped container, the conversion efficiency of the solar cell decreased after 20 times of film formation, but when the printed film was replaced for each film, the conversion efficiency did not decrease. It was found that good results were obtained with good performance.

In this embodiment, the carbon plate is used as the substrate for forming the CdTe sintered film, but a glass substrate may be used. In that case, the same effect can be obtained by laying one carbon plate under the glass substrate. Is obtained.

[0022]

As described above, according to the present invention, it is possible to manufacture a CdS / CdTe solar cell with low cost and stable performance.

[Brief description of drawings]

FIG. 1 is a sectional view of a CdS / CdTe solar cell of the present invention.

FIG. 2 is a schematic view of a CdTe film forming apparatus by the proximity sublimation method used in the present invention.

FIG. 3 is a diagram showing changes in conversion efficiency with respect to the number of times CdTe film formation according to the present invention and a conventional example

[Explanation of symbols]

 1 Glass Substrate 2 Transparent Conductive Film 3 CdS Film 4 CdTe Film 5 Carbon Film 6 AgIn Electrode 7 Ag Film 8 Quartz Tube 9 Glass / ITO / CdS Substrate 10 Carbon Plate 11 Rotary Pump 12 Printing Film / Carbon Plate 13 Lamp Heater

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Mikio Murozono 1006 Kazuma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (6)

[Claims] 1. A CdS / CdTe solar system comprising a substrate on which a transparent conductive film and a CdS film are sequentially formed, a CdTe film forming material which is arranged in close proximity to and vaporized, and CdTe is deposited on the CdS film. In a battery, the CdTe
The film-forming material consists of Cd and Te on a heat-resistant support.
Which is a film obtained by printing a fine powder containing at least Cd, Te obtained by pulverizing a simple substance of CdTe compound or
CdS / Cd in which a CdTe film having a junction interface with the CdS film is formed by vaporizing the film by heating.
Te solar cell. 2. A CdTe film-forming material, which is obtained by printing a fine powder containing at least Cd and Te obtained by crushing a simple substance of Cd and Te or a CdTe compound on a support having heat resistance, and then sintering. The CdS / CdTe solar cell according to claim 1, which is a CdTe film obtained by the above. 3. A plate-like carbon material having a heat-resistant support,
Alternatively, the glass substrate is a CdS / CdT according to claim 1.
e solar cells. 4. A step of printing a fine powder containing at least Cd and Te obtained by pulverizing a simple substance of Cd and Te or a CdTe compound on a support having heat resistance to obtain a CdTe film forming material, the CdTe film forming material. A step of arranging a film forming material, a transparent conductive film, and a substrate on which a CdS film is sequentially formed in close proximity to each other, and a step of vaporizing the CdTe film forming material by heating to deposit CdTe on the CdS film that is opposed A method of manufacturing a CdS / CdTe solar cell having: 5. A CdTe film-forming material, which is obtained by printing fine powder containing at least Cd and Te obtained by crushing a simple substance of Cd and Te or a CdTe compound on a support having heat resistance, and then sintering. The method according to claim 4, further comprising the step of:
Method for manufacturing dS / CdTe solar cell. 6. A heat-resistant support having a plate-like carbon material,
Alternatively, the glass substrate is a CdS / CdT according to claim 4.
e Manufacturing method of solar cell.