GB356895A - Improvements relating to photo-electric cells - Google Patents

Abstract

356,895. Photo-electric cells. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN, 13D, Emmasingel, Eindhoven, Holland. Aug. 5, 1930, No. 23421. Convention date, Feb. 26. Addition to 319,650, [Class 39 (i), Electric lamps, Arc &c.]. [Class 39 (i).] The photo-electric cell described in the parent Specification is modified by rendering monomolecular the chemical compound which supports the photoelectric substance, such as an alkali metal, upon the electrode. In one form, Fig. 1, the inner wall of the cell is coated for the greater part of its area with a thin metal layer 7 which may consist of silver formed as a metallic mirror applied in known manner, after which a quantity of a halogen element or of a hydrogen, halide, such as chlorine or hydrochloric acid, is introduced, for example through a tube 9, a mono-molecular layer of the introduced substance being adsorbed by the layer 7. The superfluous gas is subsequently removed, and the photo-electric substance, which may consist of an alkali metal such as caesium, is introduced, for example by vaporizing the substance from a vessel connected to the tube 9. In contact with the adsorbed halogen or hydrogen halide the photo-electric material acts to form a mono-molecular hnlide layer and, by introducing an excess of the photo-elcctric metal a thin layer of it will be partly adsorbed, this action being facilitated by exhausting and simultaneously heating to about 200‹ C. Instead of an alkali metal an alkaline earth metal such as calcium may be introduced to act on the adsorbed halogen or hydrogen halide layer. In another form, the mono-molecular layer may be obtained by introducing sulphur, hydrogen sulphide, or a volatile sulphur halogen compound, such as sulphur chloride or a thionvl chloride, for adsorbtion by the metal layer 7. The mono-molecular layer carrying the photo-electric metal may also consist of alkali metal oxide, a quantity of water vapour being introduced into the cell on to a layer of silver, followed by an excess of alkali metal, such as caesium, the reaction being facilitated by gentle heating and the removal of the evolved hydrogen. A layer of caesium oxide is formed and partly adsorbs some of the excess caesium, the remainder of which is removed. The cells may be highly exhausted or filled with a rare gas or a mixture of rare gases such as neon and argon. Specification 323,718, [Class 39 (i), Electric lamps, Arc &c.], is referred to.