Research On Defect State Control And Luminescence Performance Of Light Storage Phosphors Based On Low-dimensional Crystal Structure

Optical storage?electron trapping?phosphors have attracted wide attention as a new type of optical storage medi um.According to the different optical storage properties,they can be used in various applications as night vision,lighting and safety indicator and biomedical imaging,etc.However,the internal defects of these materials are still unpredictable due to their complex structures,leading to their ambiguous optical storage and luminescence mechanism.Moreover,there are relatively fewer studies about this material in the regions of near infrared?NIR?and ultraviolet?UV?.In this paper,NaAlSiO₄ and Ca₂Ga₂GeO₇ substrates with low-dimensional crystal structures are selected to simplify the defect state and luminescence mechanism.Based on these studies,the optical storage performance with multi-band is designed.The main contents of this paper are as follows:?1?The non-self-activated matrix NaAlSiO₄ with single directional channel crystal structure and self-activated matrix Ca₂Ga₂GeO₇ with two-dimensional layered crystal structure were prepared by high temperature solid-state method.Under 259 nm excitation,t he green photoluminescence?PL?and long persistent luminescence?LPL?were realized in NaAlSiO₄ via introducing Tb³⁺ions;Then the defect states were controlled by co-doping Bi³⁺ions,and the types of defects were identified by analyzing the thermoluminescence?TL?curves.A“fluorescence probe method”was used in the self-activated CGG matrix.Zn²⁺ions were introduced as fluorescence probes to prove the double roles of oxygen vacancy,acting as both emitters and trap centers in the LPL process.By comparing the two host above,the self-activated phosphor Ca₂Ga₂GeO₇ is more conducive to simplifying the defects and luminescence mechanism,and have better optical storage performance,which lays a good foundation for the following research.?2?The green optical storage phosphor Ca₂Ga₂GeO₇:Tb³⁺?CGGT?was prepared and the LPL properties doped with different concentration of Tb³⁺ions were studied.TL curves show that Tb³⁺ions can effectively introduce continuous traps?300-500 K?in the matrix.Due to existence of deep traps,the UV pre-excited CGGT phosphor exhibited green photostimulated LPL?PSPL?phenomenon with the stimulation wavelength of 980 nm.WLED also had the similar effect on the pre-excited CGGT phosphor,and the reasons for the enhancement of green LPL intensity was investigated.Then the TL curves measured under different conditions were analyzed,and the effect of low-energy light excitation on the carriers inside the traps were analyzed.At last,the luminescence mechanism of this green opt ical storage phosphor CGGT was described.?3?The NIR and UV optical storage performances were designed and studied in Ca₂Ga₂GeO₇ phosphor.NIR LPL peaking at 978 nm was achieved by doping Yb³⁺;Then the NIR LPL intensity of Yb³⁺was enhanced by co-doping with Tb³⁺and the persistent quantum cutting energy transfer from Tb³⁺to Yb³⁺was analyzed;In addition,the PSPL of Ca₂Ga₂GeO₇:Yb³⁺,Tb³⁺?CGGYT?was also studied,and its optical storage and luminescence mechanism were described.UV PL peaking at 390 nm was realized in CGG by doping Pb²⁺;Owing to the luminescence of oxygen vacancy,bluish green LPL?300-600 nm?was observed after turning off the UV lamp;The trap distribution in CGG:Pb²⁺was studied by analysing the TL curve;The existence of deep traps can contribute to the photochromic phenomenon under UV lamp in this material;In addition,the low energy light induced PSPL phenomenon was also studied with its luminescence mechanism analyzed.