JPS6248395B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a photovoltaic device using a bond between n-type CdS and p-type CdTe, and provides an improved method for manufacturing a paste for a CdTe sintered film. As a manufacturing method for this type of device, n-type CdS with low resistance and good light transmittance is formed on a supporting substrate.
On the sintered film, a paste made by mixing CdTe compound powder with a binder or a paste made by mixing Cd powder and Te powder with a binder is screen printed and dried. After that, it is generally fired in a nitrogen atmosphere to form a CdTe sintered film. In such a manufacturing method, in order to prepare a paste for a CdTe sintered film, it has been common practice to take the necessary amounts of all the components constituting the paste from the beginning, crush and mix them, and then manufacture the paste.
For example, it was common practice to collect CdTe or a certain ratio of Cd powder and Te powder, add a fluxing agent such as CdC _l2 if necessary, and then add a binder and mix while grinding. . However, in this method, due to the hygroscopic nature of the binder, during grinding and mixing, the moisture content in the paste may change due to moisture absorption in the air, or the binder itself may absorb moisture. The viscosity of the paste usually changes due to changes in its concentration due to evaporation. In addition, the purpose of adding a binder, which is to impart viscosity, itself serves to reduce the efficiency of pulverization and mixing, and has the drawback that it requires extra energy and time to pulverize into the required level of fine particles. The present invention provides a method for manufacturing a photovoltaic element that eliminates the above-mentioned drawbacks, and when manufacturing a paste for a CdTe sintered film, a CdTe compound or a mixture of Cd powder and Te powder is soaked in water in advance. It is characterized in that it is made into a fine powder using the added system, and a paste is prepared by adding a binder to the dried product. Incidentally, in order to strengthen the adhesion to the CdS sintered film or to increase the strength of the thin film, it is possible to add a flux when adding the binder in some cases. According to this method, CdTe compounds and Cd powder
Since the binder is added after the Te powder has been pulverized, the time required to mix the binder is very short. Therefore, water absorption during mixing and evaporation of the binder are incomparably reduced. Therefore, by collecting and mixing the required amount of binder, the desired paste viscosity can be obtained.
There is no need to adjust the viscosity as in conventional methods. Needless to say, when printing a paste to form a thin film, the viscosity of the paste affects the amount of printing and the density (porosity) of the printed material. According to the manufacturing method of the present invention, since the paste viscosity is stable for each paste production lot, the variation in performance of photovoltaic elements manufactured by printing the paste from one paste production lot to another is reduced, and the performance It also gets better. Hereinafter, the manufacturing method of the present invention will be specifically explained with reference to Examples. (Example) Add 10% by weight of CdC _l2 as a flux to CdS powder,
Propylene glycol was added as a binder to make a slurry, which was then screen printed on the glass substrate 1 as shown in the drawing, and then baked at 690°C for 20 minutes in an _N2 atmosphere to achieve stoichiometry. An n-type CdS sintered film 2 containing excess Cd was formed. The resistivity of the n-type CdS sintered film thus obtained is about 10 ⁰ to ^{10 −1} Ω·cm. This n-type
Pastes for CdTe sintered film according to the conventional method and the present invention were screen printed on the CdS sintered film 2 as shown in the following table, and after drying, the paste was heated at 650°C in an N ₂ atmosphere.
The CdTe sintered film 3 was formed by firing for 30 minutes. However, the paste for CdTe sintered film according to the present invention was prepared as follows. In other words, a paste using a CdTe compound as a starting material is
50 g of CdTe compound and 50 ml of distilled water were mixed in an experimental planetary ball mill manufactured by Fritschu, West Germany.
Put it in an agate pot of Pulverisette 5 along with 7 agate balls, take it out after crushing it for 29 hours, and heat it to 100℃.
It was obtained by drying it in a dryer until the weight remained unchanged.
It was prepared by adding 0.1 g of CdCl ₂ and 7 g of propylene glycol (PG) to 20 g of CdTe fine powder and kneading the mixture for 1 hour using a grinder manufactured by Ishikawa Factory Co., Ltd. Also Cd
The paste using powder and Te powder as starting materials is Cd
23.6 g of powder, 25.5 g of Te powder, and 50 ml of distilled water were placed in a pot of a planetary ball mill along with 7 balls, ground for 29 hours, taken out, and dried in a dryer at 100°C until the weight remained unchanged (Cd + Te). ) fine powder of 20
0.1 g of CdCl ₂ and 7 g of PG were added to the mixture and kneaded for 1 hour using a mulch mill. Next, CdTe sintered film 3
After forming a carbon film 4 by screen printing muddy carbon with a trace amount of acceptor impurities added thereto, heat treatment is performed at 350°C for 30 minutes in an N ₂ atmosphere to remove acceptors contained in the carbon. Impurities were doped into the CdTe sintered film 3. In this way, a heterojunction having a photovoltaic effect was formed between the n-type CdS sintered film 2 and the p-type CdTe sintered film 3. Next, on the CdS sintered film 2 and the carbon film 4
After attaching ohmic electrodes 5 and 6 on top,
Lead wires 7 were drawn out from each electrode 5,6.
The incident light 8 is irradiated from the CdS sintered film 2 side. The intrinsic conversion efficiency of the device thus obtained under 80 mW/cm ² tungsten halogen lamp light is shown in the following table. Note that the true conversion efficiency in the table is the average value of 10 values. As is clear from the table, if the paste prepared by the method of the present invention is used, a photovoltaic device with generally high conversion efficiency can be obtained. Furthermore, the variation between paste manufacturing lots is significantly smaller than in the conventional method.

【table】

[Table] *Propylene glycol As explained above, according to the production method of the present invention, paste can be produced in a short time,
In addition, variations in elements from paste production lot to lot can be reduced compared to conventional methods, making this an extremely effective means for producing photovoltaic elements with high conversion efficiency.

[Brief explanation of the drawing]

The drawing is a sectional view showing an example of a photovoltaic device obtained by the manufacturing method of the present invention. 1...Glass substrate, 2...CdS sintered film, 3...
CdTe sintered film, 4...carbon film, 5...ohmic electrode, 6...ohmic electrode, 7...lead wire.

Claims (1)

[Claims] 1 A sintered film of CdS or a compound semiconductor containing CdS is formed on a supporting substrate, and then CdTe
A paste consisting of a compound and a binder, or a Cd powder, a Te powder, and a binder is screen printed, and this is fired in an inert atmosphere to form a CdTe sintered film, and then the two sintered films are When manufacturing a photovoltaic device by forming electrodes, the above
To prepare a paste consisting of a CdTe compound and a binder, or a Cd powder, a Te powder, and a binder, a CdTe compound or a mixture of Cd powder and Te powder is pulverized in advance in a system with distilled water, and then,
A method for producing a photovoltaic device, comprising using a paste prepared by adding a binder to the dried product.