Research On Preparation And Performance Of Organic Thin Film Modulated Graphene Detector

With the continuous development of two-dimensional materials,photodetectors based on two-dimensional materials have become the focus of photodetectors in recent years.Among them,graphene,a two-dimensional material,is one of the hot spots of researchers.However,single-layer atomic graphene has limited light absorption capacity.Therefore,organic materials can be combined with graphene.Organic materials have the characteristics of high absorbance,large area expandability,and low cost,and high carrier mobility in graphene.Therefore,the combination of graphene and organic materials is expected to prepare high-performance detectors,is also one of the current research hotspots in the field of photodetectors.This thesis studies organic-graphene photoconductive detectors,introduces the preparation process of graphene devices,analyzes the mechanism of two organic-graphene photoconductive detectors with different structures,and compares and analyzes their photoelectric properties.First,we study a single-layer organic material/graphene detector.Comparing the performance difference between C₆₀ organic material enhanced graphene detector and pure graphene detector,due to the broadband absorption of C₆₀,the detection wavelength range of C₆₀ thin film/graphene detector is 405nm-1550nm,and the maximum responsivity of the device is 650 A/W,Response time is on the order of milliseconds.And study the effect of C₆₀ organic material thickness on performance,and analyze the mechanism.In addition,the morphology of the C₆₀ organic film was treated with m-xylene to study the effect of the organic film morphology on the performance of the device.Based on the single-layer organic material/graphene photodetector,we study the double-layer organic material/graphene photodetector.We stack the C₆₀ material and the zinc phthalocyanine material and combine them with graphene to form a graphene/C₆₀/zinc phthalocyanine photodetector.The stack of N-type material C₆₀ and P-type zinc phthalocyanine forms a built-in electric field mechanism,which promotes the transfer and separation of carriers.The response time is as low as 7?s and the responsivity is as high as 6537A/W.Compared with the single-layer organic material/graphene detector,the performance of the double-layer organic material/graphene detector has been improved to a certain extent.In addition,the contact between graphene and C₆₀ will form a heterojunction,and the contact between C₆₀ and the zinc phthalocyanine material will also form a heterojunction.The double heterojunction mechanism causes the device to produce a bi-directional response.We studied the influence of C₆₀ thickness on the bi-directional response effect and proposed the photoresponse mechanism of two heterojunctions.In addition,we have not only enriched the bi-directional response related to wavelength,but also found that the device has the bi-directional response related to the intensity of the detection light,and use the photoresponse mechanism of two heterojunctions to explain this novel phenomenon.The bi-directional response effect related to the intensity of the detection light makes the responsivity-optical power curve bend,which no longer follows the traditional exponential linear change.Our full analysis of bi-directional response effect characteristics provides a reference for opto-electronic logic devices.