▎ 摘　　要

NOVELTY - The cathode has a substrate layer (3), a p-type graphene emitting layer (2) and a cesium/oxygen activating layer (1) which are orderly arranged from bottom to top. The light is incident from the cesium/oxygen activating layer. The electron is escaped from the cesium/oxygen activating layer. The material of the substrate layer is copper or nickel or silicon or silicon dioxide or glass or quartz or sapphire or magnesium fluoride or gallium arsenide or indium gallium arsenide or gallium arsenide phosphide or gallium aluminum arsenide or gallium nitride or indium gallium nitride or gallium aluminum nitride. The p-type graphene emitting layer is prepared by using phenyl boric acid as the boron source doped graphene chemical vapor deposition (CVD) growth method. The number of the graphene layers in the p-type graphene emitting layer is not more than 20. USE - Reflective graphene photoelectric cathode applied to vacuum photoelectric detection device and vacuum electron source. ADVANTAGE - The reflective photocathode has good stability, visible light response and higher quantum efficiency. The number of the emission layers is easy to regulate and control, and the preparation of the photocathode with higher electron emission performance is facilitated. The photoelectric cathode keeps excellent electron emission performance under more complex conditions in view of the excellent characteristics of the graphene such as atomic layer thickness, and unique light absorption. The transmission type photocathode has better stability, low requirement on a vacuum environment, and easiness in preparation. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: (1) a method for preparing the reflective graphene photocathode; (2) a method for activating the reflective graphene photocathode; (3) a transmission type graphene photocathode; (4) a method for preparing the transmissive graphene photocathode; and (5) a method for activating the transmissive graphene photocathode. DESCRIPTION OF DRAWING(S) - The drawing shows a structural diagram of the reflective graphene photoelectric cathode. (Drawing includes non-English language text) Cesium/oxygen activating layer (1) P-type graphene emitting layer (2) Substrate layer (3)