GB378451A - Improvements relating to photo-electric devices - Google Patents

Abstract

378,451. Light-sensitive cells. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN, 13D, Emmasingel, Eindhoven, Holland. May 9, 1931, No. 13817. Convention date, May 10, 1930. [Class 40 (iii).] One electrode consists, at least in part, of a photo-electric substance separated by a layer of less thickness than one millimeter, containing one or more solid insulating substances from the other electrode, both electrodes and the separating layer being supported on one another. The cell will operate without the application of a potential between the electrodes. The photoelectric substance may be caesium, barium, or other alkali or alkaline-earth metals. The separating layer may be the oxide or other compound of one of the electrodes and the photo-electric substance is preferably very thin and adsorbed in the separating layer. The resistance of the insulating layer may be reduced by incorporating with it particles of conducting material such as tungsten or the photo-electric substance. In the cell shown, one electrode 3 consists of a plate of zirconium the surface of which is oxidized to form a thin insulating layer 6. The cell is evacuated and caesium is admitted, for example from a mixture of caesium. chromate and a reducing agent such as zirconium, the metal being deposited as a layer 9 on the insulating layer 6. The filling may be an inert gas or vapour. It is stated that the polarity of the difference of potential set up, depends on the portion of the electrode 9 which is illuminated. Illumination of the upper part of the electrode 9 causes that electrode to become the negative pole, but illumination of the lower part around the junction with the lead 10, where the layer of insulating oxide is thicker, causes the electrode 9 to become the positive pole. In another arrangement the electrode 3 is of nickel, the insulating layer consists of barium oxide, and the photo-electric substance of barium. The insulating layer may also consist of calcium fluoride in which caesium is adsorbed as the photo-electric electrode. A substance such as caesium oxide, which adsorbs the photo-electric substance, may be mixed with or coated on zirconium oxide or other insulating layer.