DE1265313B - Photocell and process for its manufacture - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

HOIl

German class: 21g-29/01

Number: 1265 313

File number: N 26201 VIII c / 21;

Filing date: February 10, 1965

Open date: April 4, 1968

The invention relates to a photocell with a photosensitive body provided with electrodes made of cadmium sulfide, which is obtained from a compacted body and sintered Powder and a practically balanced concentration of activators and coactivators contains. The invention also relates to a method for producing such a photocell.

In the case of the photocells of the type referred to here, copper and / or silver, usually copper, are used as activators and these activators are in relatively large concentrations, e.g. B. 10 ~ ⁴ atoms per molecule of CdS, necessary to achieve in a practically reproducible manner a high photosensitivity, as is desired for practical applications. But in order to be able to incorporate such a high concentration of activators, it is necessary to maintain the charge equilibrium to incorporate so-called coactivators, which consist of an element of column III or column VII of the Periodic Table, such as e.g. B. indium, gallium or a halogen, may exist. In order to achieve a high dark resistance and a high sensitivity to light, the atomic concentrations of activators and coactivators are practically balanced, i.e. they are chosen to be practically the same, on the condition that, since even a small excess of coactivator is harmful to the dark resistance, this is usually a precaution Activator-coactivator ratio is selected equal to 1: 0.95. The activators and co-activators are incorporated into cadmium sulfide powder by means of a heat treatment, and this powder is then converted into a compact body, e.g. B. a plate, pressed, which is sintered simultaneously or subsequently by heating to a high temperature.

The pressed and sintered cadmium sulfide cells obtained in this way have particularly favorable properties with regard to their light sensitivity and their dark resistance. But they have the disadvantage that they are too sluggish for certain applications, e.g. B. for use as a breaker cell in one Converter from direct current to alternating current. During the continually alternating switching on and off is the switch-on time at low illuminance levels, e.g. B. at 50 lux, about 80 milliseconds and at high illuminance, e.g. B. at 2000 lux, about 35 milliseconds, during the switch-off time at low illuminance and high illuminance 70 milliseconds or about 30 milliseconds amounts to. With the switch-on time, the time course between the moment of switch-on is shown here Photocell and process for its manufacture

Applicant:

N. V. Philips' Gloeilampenfabrieken,

Eindhoven (Netherlands)

Representative:

Dipl.-Ing. E.-E. Walther, patent attorney,

2000 Hamburg 1, Mönckebergstr. 7th

Named as inventor:

Roelof Egbert Schuil, Eindhoven (Netherlands)

Claimed priority:

Netherlands of February 14, 1964 (6 401 302)

the lighting and the moment when the luminous flux has reached 90% of its final value, and with the switch-off time, the time lapse between the moment the switch was switched off and the moment in which the luminous flux has dropped to 10% of its initial value, meant. For certain important ones Applications, such as a breaker in a converter from direct current to alternating current, are special the switching speed at high illuminance is important, but an improvement the switching speed at low illuminance is for other applications also desirable. Incidentally, others also have this disadvantage of being too inert Cadmium sulfide photocells that are not made by pressing and sintering, but by that cadmium sulfide powder together with a low-melting melting salt, also known in the art, such as B. cadmium chloride, applied to a carrier and then the cadmium sulfide powder is sintered with volatilization of the molten salt at a relatively low temperature. As a result of the different manufacturing methods and often also the activation, the speak on the The last-mentioned way, photocells often produced differently to the impurities added to the cadmium sulfide as the photocells, which are produced by pressing and sintering and which are on the invention relates.

The invention aims, inter alia, to provide a simple measure which, when applied

809 537/455

3 4

in the case of the pressed and sintered photocells with the properties of cadmium sulfide, the type described at the outset could lead to the achievement of a considerably shorter switch-on time and switch-off time, at least for certain applications, which is undesirable. For potassium and alkaline earth metals and these elements have been found suitable for both low illuminance characteristics and in particular concentrations of between 10 ^-3 and particularly at high illuminance in conjunction 5 1Q ^B atoms per molecule CdS particularly suitable connection with the practical application in Lower Be values of the light sensitivity and the dark illuminance already make a shortening of the switching resistance possible. Times by a factor of 2 to 3 deliver under Beibe-With a photocell of the attitude described at the beginning of a relatively high light-sensitivity type with a light-io h'chlichkeit provided with electrodes. Even at higher illuminance levels, a sensitive body made of cadmium sulfide results, which, with the addition of these elements, improves the switching speed of a compact body. On the basis of the already pressed and sintered cadmium sulphide powder available experimental data can further admit and a practically balanced concentration can be concluded that, especially with proportions of activators and coactivators, contains moderately high illuminance lead as an additive according to the invention of the cadmium sulphide body besides particularly preferable is. The preferred concentration of the Aktivatoren- and Koaktivatoren- already mentioned for lead is between about 5 x 10 ^-4 and 10 ^-2 concentration atoms per molecule, a concentration of at least CdS, and who are at relatively 10 ~ ⁵ atoms per molecule at one or more CdS high illuminance levels already reproducibly achieved by the switching speed increasing elements 20 short switch-on and switch-off times, from the group formed by lead, strontium, calcium, both of which are about 1 to 2 milliseconds, among barium, magnesium and potassium. It has been found that an addition of the appropriate photosensitivity and a favorable element from the aforementioned group in addition to the dark resistance.

already in pressed and sintered cells usual 25 I _n connection with a doping on the already activators and coactivators a considerable mentioned elements to improve the switching-shortening of the switch-on time and switch-off time at speed is preferably used as an activator with low illuminance and especially with copper and / or Silver and, as a coactivator, bring about preferably high illuminance, probably wisely used gallium, whereby the activator and, because these elements are balanced in the 30 coactivator concentrations produced in this way, activated material as rapid recombination and are preferably ^{effective between about 10 -3} and the center. Although 10 ~ ⁵ atoms per molecule will be CdS by this addition, the light sensitivity to a small extent downgrades In manufacturing a photoelectric cell according to the

set, but the gain in switching speed invention is preferably proceeded in such a way that this weighs at least one or more of the switching speed for many applications before pressing and sintering the powder in the sense that in this way one of several of the already mentioned suitable combination of speed-increasing elements in the desired Kon-switching speed, light sensitivity and centration can be added to the starting powder, dark resistance is achieved, which has been z. B. simultaneously with the addition of the activator and in another simple way for cadmium sulfide cells 40 coactivator, and by a temperature treatment, has proven to be unachievable, z. B. between 800 and 1100 ⁰ C, homogeneous in the powder. For the sake of completeness, it should be mentioned that already installed. Subsequently, it has been proposed, in the case of a light-sensitive semiconductor component made of a crystalline semi-conductor with the cadmium sulfide powder obtained in this way, cadmium conductor material with a negative resistance character- 45 oxide powder in a content of at least 0.1 the breakdown voltage weight percent and at most 10 weight percent at extremely low temperatures of the light homogeneously mixed, or instead of the cadmium oxide to reduce strength by additionally using a cadmium compound, e.g. B. cadmium doping with heavy metals such as zinc, nickel, carbonate, added, which is formed at the sintering temperature gold, iron, thallium od , the light guide does not decompose harmful components, which is noted between the donor and the acceptor line that this mixing is with cadmium oxide (German patent 1 214 340). or a cadmium oxide compound for pressed The concentration to be used for the switching and sintered photocells per se known speed-increasing elements depends below 55 It has been shown, however, that the switching speed also depends on the values of the photosensitivity required for a certain application with the addition of the switching speed and increasing elements according to the present invention, since the concentration of this already known method also affects the photosensitivity and the Ge is preferably applied. The pressing of a speed depends. Although individual differences can occur for the various compact bodies in the usual way, just like sintering, a lower concentration usually suffices, mostly at a temperature between 700 and 1200 ° C than 10 ~ ^a atoms per molecule CdS, and although done under.

higher concentrations given certain ratios. The invention will be applicable to some embodiments would be, the 65 examples and figures are preferably explained in more detail, Mentioned upper limit retained, since above Fig. 1 shows schematically in plan view with the

This limit chemical transformations can occur Electrodes provided with photosensitive cadmium, the to such deviating physical sulfide bodies of a photocell and

F i g. 2 shows the corresponding cross section according to the dashed line II-II in FIG. 1.

F i g. 3 shows schematically in longitudinal section an example of a fully assembled photocell according to FIG Invention.

To explain the invention, the production and the measurement results of several Photocells according to the invention described with different of the aforementioned, the switching speed increasing elements were doped, compared with a simultaneously in the same way known photocell produced by the photocell according to the invention only by the absence the elements increasing the switching speed deviates.

To do this, eight equal amounts of 100 g of pure cadmium sulfide powder each are weighed out. These eight batches of 100 g are each 1.5 ecm of an aqueous Cu (NO ₃ ) ₂ solution containing 8.794 mg of copper per cubic centimeter, and 1.5 ecm of an aqueous Ga (NO ₃ ) ₃ solution containing 9.167 mg Contains gallium per cubic centimeter. These additives correspond to a concentration of 3 x 10 ~ ⁴ atoms of the activator copper and 2.85 x 10 ~ ⁴ atoms of the coactivator gallium per molecule CdS.

In addition, seven of the eight batches will have a further concentration on the switching speed increasing elements are added, namely an additive that is different for each of the seven batches is as follows:

Batch I:

0.5 ecm of an aqueous Pb (NO ₃ ) ₂ solution which contains 28.7 mg of lead per cubic centimeter. This addition corresponds to a concentration of 10 ~ ⁴ atoms of lead per molecule of CdS.

Chargell:

0.5 ecm of an aqueous Sr (NO ₃ ) ₂ solution, which contains ^ ₀ 12.13 mg of strontium per cubic centimeter. This addition corresponds to 10 ~ ⁴ atoms of Sr per molecule of CdS.

Batch III:

0.5 ecm of an aqueous Ba (NO ₃ ) _a solution containing 19.05 mg of barium per cubic centimeter. This addition corresponds to a concentration of 10 "" ⁴ atoms of barium per molecule of CdS. _ ₀

Charge IV:

0.5 ecm of an aqueous Mg (NO ₃ ) ₂ solution which contains 3.36 mg of magnesium per cubic centimeter. This addition corresponds to a concentration of 10 ~ ⁴ atoms of magnesium per molecule of CdS.

Batch V:

0.5 ecm of an aqueous KNQ ₃ solution which contains 7.76 mg of potassium per cubic centimeter. This addition corresponds to a concentration of IO ⁴ atoms of potassium per molecule CdS.

Batch VI:

65

0.5 ecm of an aqueous Ca (NO ₃ ) ₂ solution containing 5.55 mg calcium per cubic centimeter. This addition corresponds to a concentration of IO ⁴ atoms of calcium per molecule CdS.

Batch VII:

5 ecm of an aqueous Pb (NO ₃ ) ₂ solution which contains 28.7 g of lead per cubic centimeter. This addition corresponds to a concentration of K) - ³ atoms of lead per molecule of CdS.

Batch VIII:

contains only the mentioned additives of copper and gallium.

After each batch has been thoroughly mixed separately, it is dried ^{by heating at, for example, 120 ° C. for 24 hours.}

Each batch is then _{heated in an atmosphere of H 2} S and nitrogen at 850 ° C for 3 hours. This heating serves to build the added activators into the bodies of the cadmium sulfide powder by diffusion.

The activated powder of each batch is then finely ground, and with each batch is 1 g of CdO powder mixed homogeneously.

From each batch several cadmium sulfide plates with dimensions 32 X 11 X 1 ecm are then produced by pressing under a pressure of about 7000 kg / cm ² , whereupon the pressed plates in a flowing nitrogen atmosphere for ¹ I ₂ hours at z. B. 950 ° C are sintered and heated.

The cadmium sulfide plates are then one-sided with an interdigital electrode pattern according to the F i g. 1 and 2 provided. On the cadmium sulfide plate 1 there are two interdigital interlocking Electrodes 2 and 3, which are applied by vapor deposition in a manner known per se be and z. B. consist of a gold-indium alloy (Au 95 percent by weight, In 5 percent by weight). The width of each line is e.g. B. about 200 μ, and the distance between two adjacent lines different electrodes is about 800 μ.

The obtained cadmium sulfide photosensitive bodies 1 with electrodes 2 and 3 finally become fully assembled in the usual and known manner and for this purpose z. B. inserted into a flat glass envelope 4, which fits around the plate 1 with some clearance. The shell is covered with a silicone grease 5 to close to the Filled seal 6, which is made of plastic, for. B. an epoxy resin. A lead wire 7 is with the underside of the plate and thus with one half 3 of the electrode pattern and the other Feed conductor 8 is with the top of the plate and thus with the other half 2 of the electrode pattern tied together.

The switching speed and light sensitivity of the photocells of the different batches will be then measured, initially at a relatively low illuminance of about 50 lux with the help of a tungsten ribbon lamp (color temperature 2800 ° C). Become from every batch three photocells measured, and the measurement results are in the table below together with the Dopings recorded, the value given for each batch being the mean value for the three photocells which show only minor deviations per batch.

Activator Coactivator w yours Switch on Switch-off time Photosensitive cnarge
XT-I- additive time in in possibility in ανγ. 3 x 10- * Cu 2.85 x 10- * Ga 10- * Pb Milliseconds Milliseconds Milliamps I. 3 x 10- * Cu 2.85 x 10- * Ga 10- * Sr 70 60 1 II 3 x 10- * Cu 2.85 x 10- * Ga 10- * Ba 35 25th 5 III 3 x 10- * Cu 2.85 x 10- * Ga 10- * mg 45 40 10 IV 3 x 10- * Cu 2.85 x 10- * Ga ίο- * κ 40 35 4th V 3 x 10- * Cu 2.85 ■ 10- * Ga 10- * Approx 30th 25th 4th VI 3 x 10- * Cu 2.85 x 10- * Ga 10- ³ Pb 40 35 10 VII 3 x 10- * Cu 2.85 x 10- * Ga no 60 15th 0.5 VIII 80 70 10 to 12

completely lower photosensitivity, which by the way is still one for many applications has a sufficiently high value. It is also used for certain applications where such a high Switching speed is required, such as. B. when used as a breaker cell for conversion from direct current to alternating current, precisely a resistance that is not too low for lighting, d. H. one

The different sizes were at lower
Illuminance of 50 lux and one between
voltage applied to electrodes 2 and 3
10 V measured.

When comparing the properties of the photocells
from batches II to VI inclusive with the
Properties of those produced in a known manner
Photocells from batch VIII shows that at
the first-mentioned photocells according to the invention 25 relatively low light sensitivity, he

both the switch-on time and the switch-off time. The dark resistance of those doped with lead

are shortened by a factor of 2 to 3 and the light cells is generally considerably higher than that

sensitivity has decreased somewhat, but of the known cells. The cells doped with lead

still has a value which is therefore a particularly favorable combination for cadmium sulfide cells can be considered very high. The 30 of switching speed, light sensitivity and

Dark resistance of the cells according to the invention dark resistance.

was generally even lower than that of the cells from batch VIII. B. up to and including VI it was found that this also at more than 1000 megohms. high illuminance a similar improvement to batches I and VII, which both relate to the 35 by at least a factor of 2 to 3, the same as with the addition of lead, it can be noted that these have lower illuminance. For high illuminance even at low illuminance, the improvement in the switching speed of the lead-doped cells is in general improvement compared to Charge VIII, which applies in particular to Charge VII. The general is considerably larger, so that lead is the great advantage of the addition of lead and the particular advantage achieved with high illuminance and for considerable improvement, but high switching speeds are still preferable. In clearer expression, if the photocells own other cases, however, in which, z. B. at lower shafts of the batch I and especially the batch illuminance, a relatively fast VII for high illuminance levels of z. B. 2000 lux cadmium sulfide cell is desired, are also compared with those of batch VIII. For 45 cells doped with alkaline earth metals or potassium, such an illuminance of about 2000 lux is important, whereby it can also be noted that the latter cells are often used in optoelectronic circuits generally have a higher light, the switch-on time and the sensitivity than those with Lead doped cells. Switch-off time of Charge I 15 milliseconds or preliminary tests indicate in this 10 milliseconds and for Charge VII1 to 2 MiIIi- 50 direction that with a further increase in the concentration seconds or 2 to 3 milliseconds, while with tration of the alkaline earth metals and potassium this illuminance the switch-on time and the z. B. 10 ~ ³ still a similar improvement in the switch-off time of the known cells of Charge VIII switching speed, but no further improvement of about 35 milliseconds or 30 milliseconds is achieved, at least not to the same extent. As can be seen from the table above 55, as is the case with lead, and that the photosensitivity is, the photosensitivity of the lead-doped cell is practically less at these higher concentrations than in the others, or at least does not decrease significantly. Cells. Although this table refers to a load, it should be finally noted that the invention does not have a luminosity of 50 lux, but at a higher luminosity to the embodiments given above, the light sensitivity decreases, ie 60 is limited and, within the scope of the invention, the light resistance In the cadmium sulfide in the professional many modifications are still possible, proportional ratio from, so that even with higher So z. B. the concentration of the switching illuminance of 2000 Lux a practically the same speed-increasing elements as well as the ratio between the light sensitivity of the concentrations of the adapted amounts of cells from the different batches maintained 65 of activator and coactivator can be changed. It will. it is also possible to combine two or more than two of the elements mentioned with lead. In the case of the herd-doped cadmium sulfide cells, however, the somewhat position of the photocells by means of the pressing and sintering

technology are naturally changes in the temperature and duration of the heating as well as in the Way of adding elements possible.

Claims (7)

Patent claims: 1. Photocell with an electrode-provided light-sensitive body made of cadmium sulfide, which consists of a powder compressed into a compact body and sintered and contains a practically balanced concentration of activators and coactivators, characterized in that the cadmium sulfide body is balanced in addition to those already mentioned contains Aktivatoren- and Koaktivatorenkonzentrationen a concentration of at least 10 ^"5 atoms per molecule CdS on one or more of increasing the switching speed of elements from the group formed by lead, strontium, calcium, barium, magnesium and potassium. 2. photocell according to claim 1, characterized in that the concentration of one or more of the latter elements is lower than 10- ² atoms per molecule CdS. 3. A photocell according to claim 1 or 2, characterized in that one or more of the elements potassium, strontium, barium, magnesium, calcium are present in a concentration of 3,000 to ~ ³ to 10 ~ ⁵ atoms per molecule of CdS. 4. photocell according to claim 1 or 2, characterized in that lead is provided as the switching speed-increasing element, preferably in a concentration of between about 5 x 10- ² and ⁴ ΙΟ- atoms per molecule CdS. 5. Photocell according to one or more of claims 1 to 4, characterized in that copper and / or silver are present as activator and gallium as coactivator, preferably in a concentration between 10 ^-3 and ΙΟ- ⁵ atoms per molecule of CdS. 6. A method for producing a photocell according to one or more of the preceding Claims, characterized in that one or more of the mentioned, the switching speed-increasing elements in the desired concentration in the cadmium sulfide starting powder are added, preferably simultaneously with the addition of the activator and the coactivator, and that this addition is incorporated homogeneously in the powder by means of heat treatment. 7. The method according to claim 6, characterized in that according to the additive mentioned and the Heat treatment before pressing and sintering, cadmium oxide powder in one Content of at least 0.1 percent by weight and at most 10 percent by weight homogeneous with the Powder is mixed or instead of the cadmium oxide a cadmium compound is added, which at the sintering temperature cadmium oxide and other volatile and / or for the light transmission not decomposes harmful components. Legacy Patents Considered:
German Patent No. 1 214 340. 1 sheet of drawings 809 537/455 3.68 © Bundesdruckerei Berlin