Study Of ?-? Semiconductor Nanostructural Composite Based Photodetectors

Photodetectors which can convert incident light into electrical signal have drawn much attention due to their extensive applications,such as optical communications,biological imaging,environmental monitoring,and chemical sensing,etc.II-VI semiconductor nanostructures as the direct bandgap semiconductors play the key role in the optoelectronic devices and novel electronic devices because of their excellent photoconductive properties.However,the pure ?-? semiconductor nanostructure based photodetector exhibits a narrow response range in visible and ultraviolet region,which may limit its application for a broadband response and near-infrared photodetection.To solve these problems,this thesis is mainly focused on the synthesis of different dimensional cadmium sulfide selenide nanostructures and zinc oxide(ZnO)nanoparticles and then fabrication of II-VI semiconductor nanostructure composite photodetectors,furthermore to improve the photoelectric performance and extend the photoresponse range of the photodetector.We also proposed a flexible and self-powered ultraviolet photodetection system based on impedance matching effect between a triboelectric nanogenerator(TENG)and ZnO nanoparticles ultraviolet photodetector,which can realize real-time monitoring of ultraviolet light and then reflects on the lighted of LED through circuit adjustment.The main content is as the following:1.High quality one-dimensional(ID)single crystalline cadmium sulfide selenide(CdSxSe1-x)nanoribbons were synthesized via a one-step metal-catalyzed physical evaporation route.The as-synthesized ternary nanoribbons were employed to construct two terminal contact photodetectors on both rigid(Si/SiO2)substrates and flexible polyethylene terephthalate(PET)substrates.The flexible photodetectors exhibit the ultrahigh current on-off ratios of about 4×106,the high responsivity of 1.24×103 A/W,the excellent reversible stability switching properties,and the response time and recovery time of 0.56 s and 0.8 s,respectively.In addition,the as-prepared flexible photodetector displayed excellent mechanical and electrical stability.These results indicate that the 1D CdSxSe1-x nanoribbons are the promising candidate for constructing rigid and flexible optoelectronic devices.2.Two-dimensional(2D)non-layered nanomaterials have attracted extensive attention for electronic and optoelectronic applications recently because of their distinct properties.In this work,we first employed a facile one-step method to synthesize 2D non-layered cadmium sulfide selenide(CdSxSe1-x,x=0.33)nanosheets with a highly crystalline structure and then we introduced a generic spin-coating approach to fabricate hybrid nanomaterials composed of PbS quantum dots(QDs)and 2D CdSxSe1-x nanosheets and demonstrated their potential for high-performance broadband photodetectors.Compared with pure 2D CdSxSe1-x nanosheet photodetectors,the photoelectric performance of the PbS/CdSxSe1-x hybrid nanostructure is enhanced by 3 orders of magnitude under near-infrared(NIR)light illumination and maintains its performance in the visible(Vis)range.The photodetector exhibits a broadband response range from Vis to NIR with an ultrahigh light-to-dark current ratio(3.45×106),a high spectral responsivity(1.45×103 A/W),and high detectivity(1.05x 10 5 Jones).The proposed QDs/2D non-layered hybrid nanostructure based photodetector paves a promising way for next-generation high-performance broadband optoelectronic devices.3.The flexible and broadband photodetectors have drawn extensive attention due to their potential application in foldable displays,optical communications,environmental monitoring,etc.In this work,a flexible photodetector based on the crystalline PbS quantum dots(QDs)/ZnO nanoparticles(NPs)heterostructure was proposed.The photodetector exhibits a broadband response from ultraviolet-visible(UV-Vis)to near infrared detector(NIR)range with a remarkable current on/off ratio of 7.08×103 under 375 nm light illumination.Compared with pure ZnO NPs,the heterostructure photodetector shows the three orders of magnitude higher responsivity in Vis and NIR range,and maintains its performance in the UV range simultaneously,The photodetector demonstrates a high responsivity and detectivity of 4.54 A/W and 3.98×1012 Jones.In addition,the flexible photodetectors exhibit excellent durability and stability even after hundreds of times bending.This work paves a promising way for constructing next-generation high-performance flexible and broadband optoelectronic devices4.The flexible and self-powered ultraviolet(UV)photodetectors have demonstrated their potential application in optical communication,biological/chemical sensor,and wearable environmental ultraviolet monitoring,etc.In this work,the flexible and self-powered ultraviolet photodetection system was demonstrated based on impedance matching effect between a triboelectric nanogenerator(TENG)and UV photodetector.The self-powered system was constructed using the freestanding triboelectric-layer based nanogenerator as power source,ZnO nanoparticles based photodetector as UV light sensor,and several LED as alarm.The ZnO nanoparticles based photodetector exhibit a strong response in the UV range with a remarkable current on/off ratio of 104 under UV light illumination and can easily distinguish the effect of visible light.The working principle and electrical output characterizations of the whole self-powered system at single-electrode and freestanding tribolectric-layer modes were studied,and the voltage output of TENG is of 68 V under tapping mode.Finally,the proposed flexible and self-powered UV light detection system shows that the output of TENG varies with the different UV light intensity of the ZnO photodetector,which can realize real-time monitoring of ultraviolet light and then reflects on the lighted of LED through circuit adjustment.