Organic Hot Carrier Photodetector With Interface Layer

Free electrons in metals can be excited as hot carriers by the nonradiative relaxation of surface plasmon resonance.In the Schottky structure formed by metal nanostructure and semiconductor,the surface plason resonance generated by external light irradiation on the metal side will induce the generation of hot carriers,and the hot carriers will be collected under the internal electric field or external bias voltage to achieve photoelectric conversion.This breaks the limit of semiconductor band gap width and widens the response range of optoelectronic devices.This advantage has attracted great attention.In this paper,ITO/Alq₃/Ag NPs/Al hot carrier photodetector was prepared by hot evaporation method,and its research was carried out.The response range of the photodetector is extended to the near infrared band by using metal nanoparticles to generate hot carriers in photoelectric conversion.On this basis,different interface layers are introduced above Alq₃ to improve the device reliability and photoelectric detection performance.The specific research work is as follows:(1)The effect of Ag NPs on the performance of ITO/Alq₃/Ag NPs/Al hot carrier photodetector was studied.In this paper,silver nanoparticles were prepared at the evaporation rate of 0.02nm/s and mixed between ITO and Alq₃.The incident light irradiates the surface plasiton resonance effect of Ag NPs,and generates hot carriers through non-radiation attenuation,thus realizing effective photoelectric detection in the non-absorbable band of Alq₃.Compared with ITO/Alq₃/Ag NPs/Al hot carrier photodetector,the response band of this device extends from 375nm to 850nm.In addition,at 850nm,the light to dark current ratio of the device reaches 25.(2)The influence of different interface layers on the operating reliability and performance of organic hot carrier photodetector was studied.Because the metal is deposited directly on the organic layer by hot evaporation plating,the metal will penetrate into the organic layer and destroy the organic film,which makes the device performance worse.Based on this,we inserted an interface layer between the metal layer and the organic layer to protect the organic thin film layer from being damaged.The interfacial layers of BCP,Bphen and A1₂O₃ are analyzed and compared in this paper.Among them,the organic hot carrier photodetector with BCP as interface layer has the best effect.The repetition rate of ITO/Alq₃/Ag NPs/Al photodetectors with BCP interface layer is increased from 10%to 60%.In addition,the dark current was effectively reduced from 40 p A to 5 p A.Light/dark current ratio increased from 25 to60.In conclusion,this paper proposes to modify the organic hot carrier photodetector with metal nanoparticles,which realizes the goal of broadening the response band of the photodetector.In addition,the insertion layer is introduced to further improve the device repeatability and reduce its dark current.The work in this thesis will provide reference for further research on broadening absorption spectrum,reducing dark current and improving repeatability.