Патент USA US2406139код для вставки
Aug. 20, A1946. ì . .‘ C, G, FlNK ¿TAL 2,406,139 PHOTQGELL' FOR MEASURING LONG WAVE RADIATIONS l Filed Feb.. 27,» 1941 ,` . @193. SW ' ¿E mí BY _, ATTORNEY 2,406,139 Patented Aug. 20, 1946 UNITED STATES PATEN T oFElcE " 2,406,139 PHoToCELL Fon MEASURING LONG WAVE RADIATIoNs Colin l(B‘r. Fink, New -York, N. Y., andJohnstone S., Mackay, Prospect Park, Pa. . - , Application YFebruary 27, 1941, Serial No..380,868 ' , Y (C1. 13e-89') 7 Claims. 2 1 This invention relates to photoelectric cells, and more particularly to such for measuring long transmitted from a distance and concentrated on acell, embodying our invention, for increas ing the sensitivity thereof.. Referring to, the drawing in detail, and first considering the embodiment of our invention Wave or infrared radiations. The principal object of our invention, generally considered, is the production of a photocell com prising a solid photo-element, bismuth sulfide, bismuth selenide, or equivalent, which is adapted to efficiently measure infrared rays including those of relatively long wave lengths. Another object of our invention is the produc-- illustrated in Figures l and 2, our cell I I con sist-s essentially of a soft metal backing I2, de` sirably of tin, covered with a layer I3 of a bis muth compound,_such as the sulfide, (BizSs), and the selenide (BizSes‘), which is in turn‘coated with a thin translucent film I4 of a conductor such as copper, silver, cadmium, carbon, bis tion of a photocell employing an element which has a large proportion or nearly all of this activ ity due to infrared radiations. ` v muth, lead, tin, 'combination of tWo or more `of the metals mentioned, or equivalent material. ' A further object of our invention is Ito develop a photocell which efficiently responds to infrared 1 radiation, as by developing as much as five mi croamperes per lumen, or the equivalent in mi crowatts, of energy received. . A still further object of our invention i-s the employment of bismuth sulfide for measuring ini . frared radiations to 70,000 Angstrom units, With « only a small response to visible radiations and Bismuth sulfide A(or equivalent) of such a `cell is a solid photo-element corresponding to the cuprous ‘oxide or selenium of the rectifier type of photocell. Such a cell generates its oWn power under the inñuence of radiations, Without `the external application of electromo-tive force. ` Both the direction of response and the efficiency of such a photocell, are dependent on the char those of shorter Wave length. _ acteristics of the photosensitive material which Other objects and advantages of the inven might be described as asemi-conductor. Y tion, relating to the particular arrangement and 25 The distinguishing feature of our cell, is that construction of the various parts, will become it is sensitivelto energy in the infrared outto a apparent as the description proceeds. ' threshold wave length of 70,000 Angstrom units. Referring tothe drawing illustrating our in- ` By comparison, the selenium cell is sensitive to energy out to 8,000 Angstrom units, caesium to vention: Y ' ' Figure 1 is a transverse sectional view of a 30 15,000 Angstrom units, and cuprous oxide to simple form .of photoeleotric cellpembodying our 14,000 Angstrom units. 4 ' ’ f Figure 2 is a face View of `the cell looking from Although it is possible to detect infrared radi ations having wave lengths of 15,000 Angstrom Figure 3 is a view of a cell, such as shown in units by means of a thermopile, which is a very expensive and delicate instrument, our inven tion makes direct reading of Ithe long Wave length invention. ' ‘ ` ` the left in Figure 1. Figure 2, `embodying a grid for increasing the conductivity of the photosensitive layer. Figure 4 is a View of a cell, such as shown in Figure 1, .the photosensitive portion 'of which is, however, duplicated on" ltheback so that it is adapted to receive radiations> from both sides. infrared radiations cheap and practical. l' The bismuth sulfide layer I3 may be about".005 inch in thickness, .although thi-cker films have' 40 been used. It is applied to the tin backing I2 under high pressure, such as about ñfty tons Figure 5 is a face View of a cell, such as shown per square inch. Other metals besides tin-may in Figure 2, except that it is of the null reading be employed if desired, but tin has been'found or compensating type. satisfactory. We prefer to make the bismuth .FigureV 6 is a view showing how a cell, such as- 45 »sulfide by chemical precipitation With hydrogen illustrated in Figure 1, may be adjustably mounted in position and associated with a'ñlter. Figure 7 is an elevational view of the com-` sulfide from acid solution, avoiding an excess of bismuth or sulfur. Such procedure is Well known to all chemists. An acid treatment after prepa bination of a cell, embodying our `invention,with ration has been found desirable. We have, how '50 ever, tried other methods of preparationybu-t the -Figure 8 is a vertical sectional view on `«they line one mentioned has given goodresults. Ä _ VlIlI--VVIII- of Figure 7 in the direction of they When the bismuth sulfide is firmly pressedinto a directional shield. La_rrOWS- ‘ j - ` . . ' . , ' . Figure? is" agdiagrammatic View, showing how. ` and onto the tin or. other soft'metal backing plate , .I 2,"5- the f outer surface Vof l:the f »phot'olayerï Vis cov radiations from an infrared source may be '5 ered with a thin layer of infrared transmittingV 2,406,139 3 conducting strap 28,'extending from a binding l electrical‘conducting material, and forms what ` post 29. A set screw 30, holds the cell tight and , has often been called the “translucent” layerA I4. ` This coating is desirably done by electrolytic de-~ ` position from an acid sulfate rof copper bath or ‘ provides an electrical connection with the metal base |29. >Leads I‘Ie and I8e extend, respectively, from- the binding post 29 and screw 30, to the millîammeter or other measuring instrument, not by sputtering the material selected from the list previously given. As an alternative, it has been i found satisfactory to rub a conducting very thin shown. 1 with a micrometer, and has been found to trans ` ` units, or hard rubber which is a good transmitter In order to connect a cell produced, as shown 1 of heat rays. i in >Figure 2, with a measuring instrument ¿such . It is also desirable, inrmany cases, to enclose the cell in .order to protect it fromY fumes, dust or other deteriorating action, in which case any Í asa milliammeter i5, a ring Iâ of metal or-other l 1 conducting material is .desirably applied, as g, shown, in engagement with the translucent layer I4, in order to make good contact there-K->` with, and the instrument I5 connectedbetween infrared transmitting substance may be used over the front face, such as one of the ñlters given above, and hermetically 'sealed to the box. Asfit is desired to avoid heat from extraneous sources, which might vitiaterthe results, 'the box , i saidring I6 and the soft'metal base, as by leads I'I and I8.' . which will pass infrared up to about 18,000 .Angstrom units, heat transmitting glass which transmits rays between 8,000 and 40,000 Angstrom mit about 20% of the radiation from an incan- ` Í descent tungsten ñlament lamp, as mea'sureclby . ‘._a selenium cell. - The filter 25, shown covering .the cell face in order to- limit the range :of infrared radiations to be detected, may be formed of “Pyrex”l glass, layer of graphite on the surfaceaof the photo l layerV I3. Such a 'coating is'too ïthinfto measure v The electrical resistances of cells, produced in 21% enclosing the cell is desirably formed-»of heat j accordance ywith our invention, have been Vfound ` to vary considerably. That is, they may be as lc'iv asï'75 ohms and ashigh as 15,600 Ohms, depend` insul-ating material, such a's Celotex. Isa, like the ringv I6 of 'Figures land A2, as shown 1 in Figure 3. .6, if desired.- ‘ Y In infrared signalling, a highly udirectional ef fect is often desired. vlin such a case, afshield .3i ing on the thickness of bismuth 'sulñde the of insulating and heat absorbing `>material may method of preparaticn,and thekind of contacts be used with a bc-X 24F holding-a bismuth suliide made to it. ' .In order to marke g-ocd contact, a metallic layer l 30 `cell Hf, as shown in Figures ’7 .and-»8. ln this case the iront contact 22.“ is provided by; the »box may besputtered or electrically deposited, as in, itself, and >the backcontact bythe setscrewZi-ílf dicated at Iâ in Figure rl, land'inorder to »cut down the cell resistance, lmultiple contacts may which box v2¢ifengages may be the provided metalwith backing a-pocket plate25f f lilf.for the be made with the translucent layer Ill by a grid reception rof ia iilter, like the lilter 25 of Figure like structure Iâ connected to a 4peripheral ring 35 ' - IAsan example of how’directional »effects Ímay ' Figure ‘l illustrates a further'ernbodiment of` ' be obtained, which also amplifyV the readings of a cell embodying our invention, Figure 9, shows our invention in whichvthemetal backing plate ; I2"b is inthe center,:.and'both surfaces-are coat-f` 40 a _50111138.32 of infrared radiations, such -as a Nernst .glowe'n a heated platinumball, ora llow' ` y ed with layers 93h of .bismutnrsulñde Vthe outer temperature projection' lamp, mounted at .the 1 V‘surfaces of -which layers vare then, in .turnfeacl-.r i'ocus ofthe sending device> 33, which'is `shown , 4coated with atranslucent"cenductinfßnlm isb; - ' _ in the form of a parabolicreiiector. . The films arethen- desirablylconnécted in parai-= ' - Y -A ybismuth.‘sulfide« cell vi ig, constructed in-ac cordancewith ourinvention, is mounted~=at~the lel, as by means of .conductorâh through con- Y necting> rings lâh. and themilliamnieter Íor other focus of a receiving device .34, which is alsoshown ' indicating Yinstrument may be connected to duplex cell. by leads >I'i’b and Ißb> from one ,of the . inthe form of> a parabolic reilector, the `sensitive rìngs"`I6b and the metal plate lâh;as„illustrated.` surface >facing inward' or toward the ¿reflecting ' surface ofthe device 35i. 'in this way theuenergy *Forf convenience in measuring, anull rea . is transmitted Afrom 'the sending deviceito the or compensated cell may be constructed, as `shox - ‘receiving device without much loss, and-focused in Figure 5, that is, two equivalent photoelectr on the cell Which is then ina position to efliciently a mountedzon a suitable base'fäü, `and 'balanced record the radiations. _against one another through a resistance izan-:l . : i . milliammeter or other sensitive measuring Tin» strumentv 23. After theyhave beenY both Y Y ' “ ~ Tests of bismuthsulñde cells, constructed in accordance with our invention, rshow that y-they have good stability, small fatigue, -slow response, and a lconductivity, which is only yslightly asym f metric. The current producedis roughly-pro >posed to the same vamount and kind ofradiation, and balanced against one another, then’the con-1 nections may be changed 'toA make them act to portional to the area exposed, vinversely propor tional tothe squareof the-distance iromrthe gether, the output from one cell 'being'then 'de-l ¿ termined as ,one-half that of both, then the out-` .light source, and both current and voltage; are kdirectly proportional to the wattage» of the ¿light i A' putgfromone of Athe cells may be balanced by a known v electromot'ive‘ force, asis usual with _'_su'ch` source.Y . ` ' 'A ' The degree of sensitivity. ,and` stabiiitylîyahes " vFigure 6 illustrates a'forin' of cell I i¿ijconstruct-`> Y _agreat _deal from cell tc cell, largely due to »varia "ed as shownin'Figures 'l and?, ‘and "adiustably` ‘ [tions bound ,to occur .in construction-andïmore `mounted§in al box“ 214; where it 'may be employed Y Aor ."lessV accidentalV characteristics. :The ,silver ".electroplatedï,bismuthfsulñde*cell'which ,had a` Wf'transmitting electricalV conducting'jlayer" isc; poor response, showed a relatively »highiunïipolar conductivity. The ratio ofßthe...conductivity'in Aopposite ï‘directions was te'nÍ toi-one. -In‘A thea-cases of the' higher sensitivity cellsfit lwas'around> two 1‘ ’ Contact is 'rríadej‘withfjthe Vlatter, #through a ` . .graphite 4.front contact 21, mountedY otra;resilient,y is; the 'resistance 'staifted’oiit ‘about this_¿same l as `’Io metal ba'seî‘I‘Ze; ai photosenis'it'ive" layer’ ' of’ bismuth ' f .v ßlllfide fsezfah'dà translucent lol'ltl’l'irlfíñfl'àred ' " “ to one, although this was not instantanefóusgùthat 2,406,139 A for other cells, but would then drift down if the current Was in one direction and up if it were in , 1. A photovoltaic cell having about 80% of its photoactivity in the infrared region and compris the other. The bismuth sulfide cell in Which the outer conducting or translucent layer was formed by ing a conducting base, a layer of material selected from the group consisting of bismuth sulñde and bismuth selenide thereover, and a thin trans evaporating Wood’s metal thereon, showed good asymmetric conductance and the only near instantaneous current response observed for any of such cells. 6 We claim: lucent electrically conducting iilm over said layer. 2. A photovoltaic cell sensitive t0 infrared radiations shorter than 70,000 Angstrom units and comprising a conductive base, a layer of material selected from the group consisting of bismuth sulfide and bismuth selenide thereover, ' The experimental bismuth sulñde cells We made Were not so photosensitive as the seleniumcell for radiations from an incandescent tungsten lamp or from the sun. Also, they were not so good as a sensitive thermopile for infrared radia and a thin translucent electrically conductive ñlm over said layer. tions. They are much cheaper, however, than a thermopile. A cell produced in accordance with our invention can, for example, be used to in dicate the amounts of energy radiated from black. bodies at low temperatures. Thus radiations from 3. A photovoltaic cell having about 80% of its photoactivity in the infrared region and compris ing a tin base, a layer of bismuth sulñde there over, and a thin translucent l layer of metal selected from the group consisting of copper, a flat iron heated to about 450° -C. gave ñfty 20l silver, cadmium, bismuth, lead, tin and combina microamperes when the iron was disposed 5 cm. tions of two or more of 'such metals deposited from the cell. thereon. Photovoltaic cells produced in accordance with 4. A photovoltaic cell having 80% of its photo our invention should find numerous practical ap activity in the infrared region of the spectrum plications in controlling furnaces,l detecting sig 25 and comprising a conducting base, a layer of bis nals in fog, burglar alarms, automatic ñre sig nals, sprinkler systems, chemicalreaction con trol device, and in any place Where it is desired to control relatively low temperatures. Although .muth sulñde, and a thin translucent electrically conducting film over said layer. 5. A photovoltaic cell having about 80% of its photoactivity in the infrared region and compris the cells which We,Í have experimented with have 30 ing a conducting base, a layer of bismuth sulfide had areas of about 1.2 square inches, it is possible thereover, a' thin translucent electrically conduct to produce cells of almost any desired surface ing ñlm deposited on said layer, and a contact area. The thickness of the backing metal is not ring engaging said layer. . critical, but should be great enough to stand 6. A photovoltaic cell having about 80% of its having the sensitive coating pressed thereinto 35 photoactivity in the infrared region and compris and properly rigidify the cell. The great advan ing a conducting base, a layer of bismuth sulfide tage of our cells, over other means for detecting thereover, an electrically conductive translucent infrared radiations, is that they may be con.. structed at small expense, While the total photo ñlm on said layer, and an electrical conductive grid engaging said film for increasing the con electric sensitivity compares favorably with that 40 ductance of said layer. of the vacuum tube photoelectric cells, being much greater than that of the sodium, and about 7. A photovoltaic cell comprising a conducting base, a layer of bismuth suliide pressed into each> face of said base, and a translucent iilm of elec the same as that of the caesium cell. Although preferred embodiments of our inven trically conducting material disposed over each tion have been disclosed, it will be understood 45 layer. that modifications may be made'within the spirit and scope of the appended claims which are not all limited to bismuth sulfide, as another com pound of bismuth, such as the selenide, may be substituted. 50 COLIN G. FINK. J OHNSTONE S. MACKAY.