Investigation On The Preparation And Properties Of Rare Earth Doped Zinc Oxide Thin Film Electroluminescence Devices Based On Silicon

The f-f transitions of trivalent rare earth ions generally emit sharp line spectrum,and the color purity of the luminescence is high.It has been widely used in the field of solid state illumination,and can also be used as an ideal three-primary luminescent material in display devices.On the other hand,ZnO is an emerging wide direct bandgap(3.37 eV)semiconductor with high exciton binding energy(60 meV)at room temperature,so high UV exciton emission is easily obtained at room temperature.In addition,it has properties similar to those of GaN,while its growth temperature is only 500-600?,which is lower than that of GaN(>1000?).Thus it can be grown on a glass substrate.Therefore,if the electroluminescence of trivalent rare earth ions with high color purity and the electroluminescent device with adjustable CIE chromaticity can be realized in ZnO host,it will provide a new path for the development of stable and efficient inorganic electroluminescent display and phosphor-free white LED in the future.In the study of the luminescence properties of ZnO,the main mechanism of defect luminescence and the enhancement of UV luminescence have been widely studied,but the main mechanism of defect emission is still controversial.In the rare earth doped ZnO electroluminescent device,since the solid solubility of rare earth ions in ZnO is low,the effect of increasing the doping concentration to increase the rare earth ion electroluminescence is not obvious.In view of the above problems,in this paper,the main mechanism of defect emission in ZnO was investigated by studying the photoluminescence spectra of ZnO thin films in different annealing atmospheres.Secondly,the electroluminescence of rare earth ions is improved by the design of the device structure and the energy transfer between rare earth ions,and the ZnO-based electroluminescent device with CIE color tunability is realized by energy transfer between rare earth ions.The specific research work is as follows:(1)Preparation of high quality ZnO thin films and their photoluminescence properties.A ZnO thin film was deposited on the Si substrate by magnetron sputtering,and the ultraviolet luminescence in the PL spectrum of the ZnO thin film was improved by adjusting the substrate temperature and the argon-oxygen ratio during sputtering.The main mechanism of the defect emission is discussed by studying the PL spectra of ZnO thin films annealed in different atmospheres(O2,N2).By adjusting the annealing temperature and time in the N2 atmosphere,a high quality ZnO film of ultraviolet(UV):visible(VIS)=19:1 in the PL spectrum was obtained.(2)Improvement of the ZnO:Er electroluminescent device by the introduction of hole injection layer and hole transport layer.A ZnO:Er electroluminescent device was fabricated on a n-Si substrate by magnetron co-sputtering,and Er3+ green electroluminescence was obtained.The mechanism of the EL was discussed by comparing the EL and PL spectra.Furthermore,the introduction of PEDOT/PSS as a hole injection layer in a ZnO:Er single layer device enhances the green EL of Er3+.Moreover,a MgZnO:In layer was introduced as a hole transport layer in a ZnO:Er single layer device,and the band position of the MgZnO:In layer was adjusted by adjusting the concentration of In,thereby improving the electroluminescence property of the device.The ZnO:Tb green electroluminescent device was prepared by magnetron co-sputtering method,and Tb3+ green electroluminescence was obtained.(3)Study on energy transfer phenomena in rare earth doped ZnO thin film electroluminescent devices.The ZnO:Eu electroluminescent device was prepared by magnetron co-sputtering method,and the red electroluminescence of Eu3+ was obtained.Tb3+ was introduced into the ZnO:Eu electroluminescent device by co-sputtering and layered growth,and the electroluminescence of Eu3+ was enhanced by the energy transfer from Tb3+?Eu3+.The doping concentration of Eu was unchanged.Next,the optimum doping concentration of Tb is obtained.In addition,Tm3+ was introduced into the ZnO:Eu device by the same method,and the electroluminescence of Eu3+ was enhanced by the energy transfer from Tm3+?Eu3+.At the same time,the color coordinates of the EL of the device are adjusted by changing the doping concentration of Eu and Tm.A ZnO:Sm/Tb electroluminescent device was prepared by the same method.The energy transfer through Tb3+?Sm3+ enhances the electroluminescence of Sm3+.(4)Preliminary investigation of rare earth doped ZnO thin-film white electroluminescent devices.A ZnO:Tm blue electroluminescent device was prepared by layered growth method,and the blue electroluminescence of Tm3+ with CIE coordinates of(0.13,0.09)was obtained.The blue electroluminescence of Tm3+ was enhanced by the introduction of the hole injection layer and the hole transport layer.A ZnO:Dy yellow electroluminescent device was prepared by co-sputtering method,and yellow electroluminescence of Dy3+ was obtained.ZnO:Dy/Tm electroluminescent devices were prepared by a combination of co-sputtering and layered growth,and the electroluminescence of Dy3+ was improved by the energy transfer from Tm3+?Dy3+.In the ZnO:0.6 mol%Dy electroluminescent device,2 mol%Tm was introduced,and the CIE coordinate of the device was adjusted from(0.45,0.48)to(0.43,0.44),and the luminescence shifted toward the white light.