US1568694A - Photo-electric device - Google Patents

Description

1,568,694 w. A. RUGGLES PHOTO ELECTRIC DEVICE Jan. 5 1926. 7

Filed April 16, 1921 Inventor \Xfllliam A. Fluggles,

His Attorney.

electrode which common y Patented Jan. 5, 1926.

UNITED "STATES 1,568,694 P'ATENT o FicE;

WILLIAM A. RUGGLES, OF SCHENECTADY, NEW YORK, ABSIGNOR 'IO GENERAL ELEC- TRIO COMPANY, A CORPORATION OF NEW YORK.

PHOTO-ELECTRIC DEVICE.

Application filed April 16, 1921. Serial No. 462,052.

To all whom it may concern:

Be it known that I, WILLIAM A. RUGGLES', a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Photo-Electric Devices, of which the following is a specification.

The present invention relates to the preparation of photo-electric devices and includes in particular a new method of forming the conductive sup ort for an active is constituted by a film of light-sensitive metal, as, for example, potassium. v

Heretofore, a conductive backing for the active electrode material has been prepared by depositing a film of silver from an aqueous solution upon the inner surface of a glass bulb. Upon ordinary drying, potassium was admitted to the bulb in the presence of air and deposited upon the backing metal. The resulting electrode inevitably contained various impurities, notably oxidation products and occluded moisture, which were a source of variability in the photo-electric device.

In accordance with my invention, I have provided a photo-electric electrode of imby depositing a film of proved sensitivity to serve as a conductive metal in a vacuum base for the light-sensitive metal which preferably is deposited likewise in a vacuum upon the conductive foundation surface. My invention includes also new methods of preparing metal films as set forth with greater particularity in the appended claims.

In the accompanying drawing, Fig. 1 illustrates in perspective a device to which my invention is applicable, the bulb wall being in part broken away, and Fig. 2 is an enlarged view of a slightly modified heater electrode with a bead of volatilizable metal attached.

The device shown in the drawing comprises a glass bulb 1 having a side arm 2 containing a glass stem 3 into which are sealed electric conductors 4, 5. Attached to these conductors is a vaporizer which is constituted by a coiled filament 6 consisting of a refractory metal, as, for example, tungsten,-molybdenum or tantalum. The conductor 5 also acts as a support for a coneshaped body 7 consisting of nickel, or other suitable material, which acts as a shield to prevent deposition of metal upon part of the bulb. It is not necessary that the shield 7 should have the particular shape illustrated. A cone or pyramidal shape is prefarable, as it reduces loss of light when the device 18 111 use,'rays of light striking the shield being reflected to the side walls upon the sensitive electrode. A shield 8 intercepts metal articles projected from the filament 6, as escribed below to prevent silvering of the inner surface of the side arm 2 which might cause electrical shert-circuiting.

The bulb 1 is first carefully freed from moisture by baking at a temperature close to but below the softening temperature of glass, say, at 360 C. The bulb is then exhausted through the tubulation 9, a condensation pump preferably being used.

A bead of easily volatilizable metal, as, for example, silver, gold, or copper, is affixed to the filament 6 before sealing in the stem 3, as shown at 10 inFig. 2. The filament 6 is heated by passage of current to the volatilizing templerature of the bead 10 when the bulb as been well exhausted, say, to a vacuum of about 5 micron (0/0005 mm. of mercury), the molten bead clingin to the turns of the coiled filament while t e metal is volatilizin'g. The metal vapor is projected radially in the evacuated bulb interior and is condensed upon the inner surface of the bulb which is artificially cooled if necessary; for exam le, by immersing the bulb in water. The eposited metal film makes electrical contact with a sealed-in electrode 11 consisting of platinum or other suitable material. The shield 7 will shadow a portion of thebulb, as indicated at 12, which is left clear-of deposit as the metal vapor me high vacuum travels in straight lines. Thereupon the bulb is again heated and with the vacuum unbroken and the vacuum pump in constant operation, a light-sensitive material, for example, metallic potassium is introduced as a vapor into the bulb. Conveniently, the potassium, or other suitable light-sensitive material, may be contained in a small bulb 13 intercalated in the vacuum line 9, heat being applied in any convenient way to volatilize the same. In order to render the potassium free from im urities, I prefer to introduce the same in t e unavoidably oxidized state into a side chamber 14, as indicated at 15. After the silver or other metal has been deposited as above described, the chamber 14 is heated to distill the potas sium into an adjoining chamber 16 where it distills as indicated by the dotted lines, the bulb 13 and the device 1 being gently heated. Thereupon the potassium is distilled in turn into the bulb 13 and then into the device 1. The potassium condensed upon the window 12 can be driven off by external heating.

The photo-electric device now may be subjected to a sensitizing treatment by admitting hydrogen at a pressure ofsay, 100 microns of mercury, and passing a suitable current through the device, the hydrogen eventually being replaced by argon gas but these steps in the manufacture of the photo-electric device subsequent to the formation of the film electrode forms no part of my present invention. The completed device is finally sealed off by fusion at 17 in the usual manner.

During the operation of the device, light rays are admitted through the window 12 and impinge either directly or by reflection from the surface of the shield upon the surface of the film electrode which acts as a cathode, causin an electron current to be emitted. The filament 6 and the shield 7 functions as anode in the completed device, the filament being'unheated. The photoelectric device produced as herein described is more sensitive and reproducible in its characteristic than devices formerly made by chemical methods.

\Vhat I claim as new and desire to secure by Letters Patent of the United States, is,-

1. The method of preparing a light sensitive device which consists in depositing metal upon the inner surface of an evacu ated container, and depositing a hoto-sensitive material upon said sur ace while maintaining said vacuum.

2. A photo-electric device comprising a sealed bulb, a film of conductive material upon the inner surface of said bulb, said film being formed by the deposition of metal vapor in a vacuum, and having a clear area constituting a window formed by shielding a portion of said bulb surface from said vapor, a light-sensitive material superimposed upon said film and a cooperating electrode.

3. The method of preparing a cathode in a photo-electric device having an insulating container which consists in evacuating the container at an elevated temperature, depositing by vaporization a metal film upon the inner surface of said container except for a region through which light is to be admitted while keeping said vacuum unbroken, and depositing a photoelectric material upon said film.

4. The method of preparing a photo-electrio device comprising a glass container, which consists in removing gas from the walls and the space within said container, depositing a metallic film on the inner surface of said container and thereupon depositing a light-sensitive material, the vacuum remaining unbroken during the latter two operations.

The method of depositing a conductive film upon a non-conductive support adapted to receive the active material in a photoelectric device which comprises evacuating said device, vaporizing a metal in the evacuated space in said device, maintaining said foundation cool enough to condense vapor thereon and mechanically shielding portions of the support which is to be maintained clear from deposit.

6. The steps in the preparation of a photo-electric device which consists in evacuating said device at an elevated temperature, vaporizing a metal in said device while maintaining said vacuum intact, cooling the portion of the envelope of said device to deposit a film of metal thereon, shielding another portion of said envelope from a deposit of said metal and thereupon depositing a light sensitive material upon said film while keeping said vacuum unbroken.

7. The method of preparing a photo-sensitive electrode which consists in coating a gas-free interior surface of an evacuated envelope with a layer of metal in the absence of water, and thereupon depositing a layer of photo-sensitive material on said coating.

8. A photo-electric device comprising a bulb, a shield within said bulb, the inner surface of said bulb being coated with metal layer formed by condensation from vapor in a vacuum and having a clear space whereon condensation has been prevented by said shield which constitutes a reflector in said device.

9. A photo-electric device comprising a bulb containing an attenuated gas, a conductive metallic film upon the inner surface of said bulb except for a clear area constituting a Window, a leading-in conductor therefor, a photo-sensitive material upon said film, a cooperating electrode and a light reflector in said bulb opposite said window.

Inwitness whereof, I have hereunto set my hand this 15th day of April, 1920.

. WILLIAM A. RUGGLES.

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