Study Of Ag Nanoparticle Localized Surface Plasmon-enhanced ZnO Quantum Dot Ultraviolet Light-emitting Devices

ZnO,a directly wide band-gap(3.37eV)semiconductor with high exciton binding energy(60meV),can achieve efficient excitonic emission at room temperature and higher temperature which makes ZnO become an ideal candidate for ultraviolet(UV)light-emitting devices.Compared with ZnO bulk material,ZnO quantum dots(QDs)have a wider band gap because of quantum-size effect,are expected to structure more UV light-emitting devices.Besides,in recent years,metal localized surface plasmons(LSPs)are confirmed to an effective method to improve the performance of light-emitting devices.Meanwhile,Ag nanoparticle(NP)LSPs are often used to enhance the efficiency of ZnO light-emitting devices.Because there is some overlap between Ag NP LSPs resonance peak and ZnO near-band-edge(NBE)excitonic emission peak.In this thesis,ZnO QDs were synthesized through a sol-gel route in ethanol.Then,AgNO3 dissolved in ethanol was dropped into ZnO QDs colloidal solution to prepare the composite of ZnO QDs and Ag NPs(ZD-Ag NPs).Next,we introduce ZD-Ag NPs into the optimized ZnO QD UV light-emitting devices.And,the efficiency of ZnO QD light-emitting devices was improved.The specific content is as follows:(1)ZnO QDs were synthesized through a sol-gel route in ethanol and were characterized by transmission electron microscope(TEM),scanning electron microscope(SEM),x-ray diffraction(XRD)and so on.Then,the ZD-Ag NPs were synthesized through dropping AgNO3 solution into ZnO QDs colloidal solution,without any other external conditions.And,the extinction peak was adjustable through the control of reaction time.(2)ZnO QD UV light-emitting devices based on p-GaN/ZnO QDs(30nm)/Al2O3/ZnO QDs(120nm)heterostructure were designed and prepared.ZnO QDs acted as an electron injection layer as well as an active layer.The results indicated that it has higher electroluminescence(EL)efficiency and relative stronger ZnO NBE emission,compared with p-GaN/ZnO QDs(150nm)conventional PN heterostructure Zn O QD light-emitting devices.(3)Based on above ZnO QD UV light-emitting devices,ZD-Ag NPs were introduced through replacing the ZnO QDs(120nm)layer.And,the Ag NP LSP-decorated p-GaN/ZnO QDs(30nm)/Al2O3/ ZD-Ag NPs heterostructure ZnO QD UV light-emitting device was manufactured.ZD-Ag NPs not only acted as an electron injection layer,but aslo introduced Ag NP LSPs.The results indicated that ZnO NBE EL efficiency was obviously enhanced through introducing ZD-Ag NPs into ZnO QD UV light-emitting devices.Finally,through comparing the fluorescence lifetime and temperature-dependent photoluminescence(PL)spectra between ZD-Ag NPs and ZnO QDs,we confirmed that ZnO NBE EL enhancement is ascribed to the resonance coupling between Ag NP LSPs and ZnO NBE excitons and photons.