JPS6138627B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a photoconductive element having a sandwich structure.

Conventionally, photoconductive elements composed of - group compound conductors such as CdS, CdSe, and CdS--CdSe,
As shown in FIG. 1, a photoconductive layer 2 is formed on a substrate 1 made of ceramic or the like, metal electrodes 3 and 4 are provided facing each other on one side of the photoconductive layer 2, and lead wires 5 and 6 are provided thereon. It was a so-called lateral structure that used only one side of the crystal. Since approximately half of the light-receiving surface of this lateral structure photoconductive element is covered with the metal electrodes 3 and 4, the efficiency is extremely low, and a high photosensitivity cannot be obtained with a small light-receiving area.

In contrast to the above-mentioned photoconductive element having a lateral structure, there has recently been a photoconductive element having a sandwich structure as shown in FIG. This is a transparent glass substrate 7
A transparent electrode 8 made of tin oxide or the like is attached on top, a photoconductive layer 2 is sintered on top of the transparent electrode 8, and electrodes 3 and 4 are attached to the photoconductive layer 2 and the transparent electrode 8, respectively. The lead wires 5 and 6 are taken out from the. The light enters from the glass substrate 7 side, passes through the transparent electrode 8, and irradiates the photoconductive layer 8.

The photoconductive element having the sandwich structure has the following characteristics compared to the lateral structure.

(1) Since light enters from the glass substrate side, there is no dead area caused by electrodes.

(2) The resistance value should be 1/10 or less.

(3) Excellent response characteristics.

(4) The ability to integrate minute elements at high density.

As a method for manufacturing a photoconductive element having a sandwich structure having the above-mentioned characteristics, the first method is to slice and use a single crystal.

The second method is to use a vapor deposited film.

is likely. However, all of these methods have the following drawbacks.

(1) In both the first and second methods, if the growth is left as it is, the photoconductivity is insufficient, that is, the S/N
The ratio is small.

(2) Because the resistance is too high, some kind of post-processing, for example, processing to form donor levels and acceptor levels in the crystal, is required.

(3) The first method is that the effective area is small.

(4) In the second method, the deviation from the stoichiometric ratio is large due to the high vapor pressure of the group elements, resulting in very poor reproducibility.

(5) Manufacturing costs are very high.

For these reasons, neither method can be put to practical use.

In contrast to these methods, if a sandwich structure can be manufactured using a polycrystalline sintering method, that is, a flux melting method, the above-mentioned problems will not occur. However, as an absolute condition for the sandwich structure, it is necessary that there be no pinholes, but it is difficult to obtain a satisfactory result using conventional sintering methods, and several attempts have been made. One of them is the special public service in the 1970s.
There is issue 26918. In this method, glass substrates are arranged on a rotating ring that rotates in a closed container, and when the glass substrates pass under a spray gun installed at the top of a low-temperature area away from local heating, the glass substrates are sprayed to a predetermined thickness. Then, when passing through a local heating section, the material is sintered, and this process is repeatedly sintered and grown until it reaches a predetermined thickness. Therefore, as shown in FIG. 3, a plurality of photoconductive films ₂₁ to ₂₄ are formed on the transparent electrode 8 of the glass substrate 7.

In such a method of laminating multiple layers of sintered films, the state in which pinholes decrease with each layer can be confirmed by observation with a scanning electron microscope. However, the degree of particle size growth also differs from layer to layer. Therefore, the resistance value and other characteristics have a gradient in the thickness direction of the photoconductive element, that is, between the two electrodes, which is extremely disadvantageous. Also,
From the first layer ₂₁ to the fourth layer ₂₄ , the number of pinholes clearly decreases, but as the layers are piled up, the amount of flux accumulates and increases, and the amount of flux in the layers that have been formed so far increases. Among the particles, sintering occurs in which a plurality of particles combine at once to form large particles, and at this time, the number of pinholes that had been reduced increases again. moreover,
In a chloride atmosphere, that is, a flux atmosphere in which CdCl ₂ is vaporized at high temperatures, when the temperature is frequently raised, the transparent electrode (SnO ₂ , In ₂ O ₃ , Au thin film, Ni thin film, Cr thin film, etc.) undergoes chemical changes and the electrode It had drawbacks such as high resistance itself.

In view of the above points, the present invention provides a manufacturing method for forming a pinhole-free polycrystalline film by sintering only one layer.

A specific embodiment of the method for manufacturing a photoconductive device with a sandwich structure according to the present invention will be described below.

(1) First, CdS or CdSe alone powder or
CdS―CdSe mixed powder, activator ( _CuSO4・
5H ₂ O), a fluxing agent (CdCl ₂ ), and water (H ₂ O). As a specific formulation example, CdS powder and
CdSe powder is ground in a pole mill for over 48 hours, and only particles with a particle size of 1 μm or less are selected. 10g of these CdS powders and 10g of CdSe powder
Copper sulfate solution containing 100 ppm of Cu ions ( _CuSO4 .
5H ₂ O) are suspended in 1960 ml of deionized water.

(2) On the other hand, a glass substrate 7 with a transparent electrode 8 formed on one side is prepared. As the transparent electrode 8, tin oxide (SnO ₂ ), indium oxide (In ₂ O ₃ ), indium tin oxide (ITO), or a metal thin film (sputtered film of Au, Ni, Cr, etc.) is used.

(3) Arrange the glass substrates 7 attached to the transparent electrodes 8 on the bottom of a heat-resistant glass container, and pour 40 ml of the suspension into the glass container.

(4) After the CdS--CdSe powder has completed precipitation, remove the supernatant water through paper, etc., and dry thoroughly.

(5) Next, arrange the precipitated film in a separately prepared heat-resistant glass container with the side to which it is attached facing up, and attach the lid with 25 mg of cadmium chloride (CdCl ₂ ) as a sintering agent attached to the inside as microcrystals. Cover the container. Then, it is sintered by heating at about 600°C for 10 to 20 minutes. The photoconductive layer 2, which is a sintered polycrystalline film, has a diameter of 10 to 10 mm without pinholes as shown in FIG.
The thickness is approximately 40 μm.

(6) After sintering, wash with distilled water and dry.

(7) Tin (Sn) electrodes 3 and 4 are attached to the photoconductive layer 2 and the transparent electrode 8 by vacuum evaporation.

(8) Take out the lead wires 5 and 6 from each electrode 3 and 4 using conductive adhesive.

(9) Fix the lead wire extraction part with transparent solidified resin.

(10) Cover and protect the entire cell surface with transparent solidified resin.

According to the manufacturing method of the present invention, in addition to the above-mentioned features of the Sandwich-type photoconductive element, the following extremely excellent effects unique to the present invention are achieved.

(1) A photoconductive element of any thickness can be produced by a single precipitation and sintering process.

(2) Compared to the spraying method, it is easier to increase the area.

(3) Compared to the spraying method, the film thickness is more uniform, the quality is consistent between products, and the yield is better.

(4) Compared to the spraying method, there is less waste of materials such as CdS, CdSe powder, and CdCl ₂ flux.

(5) In the spraying method, by spraying many times, the dark resistance gradually decreases from the first sprayed layer, and the S
(bright resistance)/N (dark resistance) becomes worse. However, in the manufacturing method of the present invention, since precipitation and sintering are performed only once, there is no deterioration in S/N.

(6) Mass production is possible and costs are low.

Incidentally, the photoconductive element manufactured by the method of the present invention and the conventional photoconductive element have excellent characteristics as shown in the illuminance-resistance characteristics in Figure 5 and the responsiveness at constant illuminance in Figure 6. This shows that.

[Brief explanation of the drawing]

Figures 1a and b are a front view and a cross-sectional view taken along the line A--A of a lateral type photoconductive element, Figures 2 a and b are a front view and a cross-sectional view taken along the line B-B of the sandwich-type photoconductive element;
The figure is a cross-sectional view of a photoconductive layer formed by a conventional spraying method, and FIG. 4 is a cross-sectional view of a photoconductive layer formed by a precipitation method of the present invention.
FIG. 5 is an illuminance-resistance characteristic diagram, and FIG. 6 is a response characteristic diagram. 1... Ceramic substrate, 2... Photoconductive layer, 3,
4... Electrode, 5, 6... Lead wire, 7... Glass substrate, 8... Transparent electrode.

Claims (1)

[Claims] 1 Cadmium sulfide, cadmium selenide, or a mixture powder thereof and an activator are suspended in deionized water, and this suspension is placed in a container in which a glass substrate with a transparent electrode is arranged on the bottom of the container. The powder is injected to form a precipitated film, and this precipitated film is turned upward and heated and sintered in a container to which a sintering agent is attached, and a photoconductive film of a predetermined thickness is formed by this one-time precipitated sintering. , a method for manufacturing a photoconductive element by attaching electrodes and lead wires thereto. 2 The suspension contains a powder mixture of 10 g of cadmium sulfide and 10 g of cadmium selenide, and 100 ppm of Cu ions.
2. A method for producing a photoconductive element according to claim 1, wherein 18 ml of a copper sulfate solution containing 18 ml of copper sulfate is suspended in 1960 ml of deionized water. 3. The method for manufacturing a photoconductive element according to claim 2, wherein the cadmium sulfide powder and the cadmium selenide powder are fine powders each having a particle size of 1 μm or less.