The Research Of Photodetector Based On Carbon Nanotubes Film

Carbon nanotubes?CNTs?have attracted intense attention due to their special band structure,excellent electrical and photoelectric properties.However many great attributes CNTs may have,in their pristine forms they don't naturally meet the diverse specific demands for different applications.In addition to the fact that,the inert chemical structures with low surface energy are a principal bottleneck for cost-effective solution processing,some pristine CNTs are intrinsically metallic that restricts their uses in optoelectronics and electronics.In recent years,researchers have modified carbon nanotubes in many ways to improve their photodetection performance,including orientation of carbon nanotubes,N doping and construction of van der Waals heterojunctions.In this paper,single-walled carbon nanotubes?SWCNTs?were used as research materials.In order to improve the performance of photodetectors based on SWCNTs,orientation treatment,doping modification,and van der Waals heterojunction have been used to control the interface energy bands.High-performance photodetectors were successfully constructed.By using various characterization techniques and band theory systems,we systematically studied the surface morphology and carrier dynamics of the films.There are four main aspects in this dissertation.1.The first part is based on the polymer-assisted orientation method to prepare large-area oriented single-walled carbon nanotube films.By studying the effects of polymer concentration,ion dispersant concentration and other factors on the orientation of single-walled carbon nanotube films,the optimized oriented film was obtained,and the visible-near-infrared sensitive photodetection was prepared by using the oriented single-walled carbon nanotube film.The polarization index S of the device is close to 1,the maximum photoresponsivity is 20?A/W@780 nm,and the fastest response time is 34 ms@532 nm,indicating that the single-walled carbon nanotubes after orientation treatment have good application potential.2.The second part is based on doping the fifth family elements and using high work function/low work function electrode structure to improve the performance of single-wall carbon nanotube devices.The optimum doping ratio of the device was obtained by changing the concentration of doped hydrazine.The highest photoresponsivity of the device was R_max=292.5 mA/W@532 nm and the response time was 34 ms.In addition,the response of the constructed Au-Al electrode asymmetric structure device is much larger than that of the Au-Au symmetric electrode structure device,and the reason is analyzed in detail by the energy band theory.3.The third part is based on photodetection of single-walled carbon nanotubes/graphene/P3HT composite films.The absorption of single-walled carbon nanotubes in the visible to near-infrared region is very high.The zero band gap structure of graphene enables it to achieve wide spectral absorption.Combining P3HT with other two materials can significantly improve its photodetection performance.We comprehensively utilized the advantages of the three materials to construct a high-response,broad-spectrum photodetector with a maximum photoresponsivity of R_max=10466 A/W@650 nm and a response time of 1.532 s.It shows that the combination of a variety of low-dimensional materials and organic functional materials can significantly improve the response of the device,and provides reference for other low-dimensional materials photodetectors.4.The fourth part is based on photodetection of single-walled carbon nanotubes/graphene/C₆₀ composite films.C₆₀ has excellent light absorption in the ultraviolet range and has a similar atomic arrangement with graphene.We constructed a broad-spectrum detector using three carbon allotropes with a response band covering405 nm to 980 nm.The highest photoresponsivity of the detector is R_max=10597A/W@450 nm and the response time is 99.2 ms.In addition,a method for improving the response speed of the device is proposed,that is,using continuous visible light as a gate light,the photoresponse of the device under pulsed infrared source illumination can be modulated.In summary,this dissertation systematically studied the photoelectric properties and carrier dynamics of carbon nanotube-based photodetectors,and discussed its physical mechanism in depth.This results provide important reference for designing high-performance optoelectronic devices.