The invention discloses a P-type 
graphene / N-type 
germanium nanocone array schottky junction 
infrared photoelectric 
detector and a preparation method thereof. The preparation method is characterized by comprising the following steps of forming an insulating layer on the front face of an N-type 
germanium basal layer in an 
evaporation manner by taking the N-type 
germanium basal layer as a base region of the photoelectric 
detector; arranging an N-type germanium nanocone array on the upper surface of the N-type germanium basal layer; transferring P-type 
graphene to the N-type germanium nanocone array covered with the insulating layer; 
coating the P-type 
graphene with 
indium tin oxide (ITO) nano-particles in a spin manner to realize a P-type graphene / N-type germanium nanocone array schottky junction-based 
photodiode. According to the 
infrared photoelectric 
detector disclosed by the invention, by utilizing the structure of the germanium nanocone array and the characteristic of the surface 
plasma resonance of the ITO nano-particles, the ability of absorbing light is enhanced, and the ability of responding to light is improved; the preparation method disclosed by the invention is simple, is suitable for 
mass production, and can be used for preparing the 
infrared photoelectric detector which has high light absorption ability and is high in 
photoelectric conversion efficiency, and a foundation is laid for applying the germanium nanocone array structure to the photoelectric detector.