The Luminescence Mechanism And Application Exploration Of Cs₂(Na,Ag)InCl₆

Lighting accounts for a fifth of global electricity consumption.Currently,the main technology of white lighting is blue light emitting diodes combined with yellow phosphor.This technology has inherent shortcomings:low color render index and excessive blue component which can cause damage to the retina.But this problem can be solved by ultraviolet light emitting diodes combined with white phosphor.Cs₂(Na,Ag)InCl₆ is a kind of potential white light emitter with self-trapped exciton emission,which has many advantages,such as broad emission,high emission efficiency,high stability and environmentally-friendly components.However,the understanding of the luminescence of Cs₂(Na,Ag)InCl₆ is not deep enough,and the light quality of Cs₂(Na,Ag)InCl₆ is unsatisfactory,and the application of Cs₂(Na,Ag)InCl₆ is limited to phosphors.These problems seriously restrict the development of Cs₂(Na,Ag)InCl₆ in the aspect of white lighting.Therefore,this dissertation is developed from three aspects of Cs₂(Na,Ag)InCl₆:deeply understanding the luminescence mechanism,improving the light quality and expanding the application.(1)Study on luminescence mechanism of self-trapped excitons in Cs₂(Na,Ag)InCl₆.Large stokes shift and broad emission are the intrinsic properties of Cs₂(Na,Ag)InCl₆.In this dissertation,with the help of configuration coordinates diagram,the analytic expressions of stokes shift and the spectral width were derived from Huang-Rhys Factor and the phonon energy.Then the temperature-dependent spectral properties were studied,including the change of peak width with temperature and the change of emission intensity with temperature.In the last,a simple method for obtaining Huang-Rhys Factor and phonon energy in materials by Raman spectrum and emission spectrum at room temperature is proposed.(2)Study on rare earth doped Cs₂(Na,Ag)InCl₆.The lack of blue and red components in the spectrum of Cs₂(Na,Ag)InCl₆ results in low white light quality.In this dissertation,Ho Cl₃ was added to the precursor to obtain the Ho doped Cs₂(Na,Ag)InCl₆.The rare earth emission and self-trapped exciton emission both existed in the doping system.The red and blue components of rare earth emission effectively improved the light quality of Cs₂(Na,Ag)InCl₆,enhancing the color render index from 70.3 to 75.4 and shifting the chromaticity coordinate from(0.40,0.47)to(0.39,0.46).The doping system was also very stable:the emission intensity was kept at 80%compared with the original intensity after 700 hours of continuous ultraviolet lighting in the air.(3)Study on the electrical pumping light-emitting-diode based on Cs₂(Na,Ag)InCl₆.So far the applications of self-trapped excitons are limited to phosphor.In the dissertation,the exploration of light-emitting-diode based on self-trapped excitons was performed.First,smooth and compact Cs₂(Na,Ag)InCl₆ film with 40%photoluminescence quantum yield was prepared by thermal evaporation and post-annealing process.Then the device structure was designed as ITO/PEIE/Zn O/PEIE/Cs₂(Na,Ag)InCl₆/TAPC/Mo O₃/Al and this device could work at a low efficiency.This dissertation also points out that the long lifetime of self-trapped excitons and low carrier mobility should be responsible for the low efficiency.