Preparation And Room Temperature Phosphorescence Properties Of A New Two-dimensional Cadmium-based Perovskite

Room temperature phosphorescence is a phenomenon that continues to emit light after the excitation light is turned off.It has been widely used in information storage,anti-counterfeiting encryption,biological imaging and emergency lighting.Two-dimensional perovskite is a kind of material with layered structure formed by self-assembly of organic and inorganic components,which has both the structural designability of organic components and the stability of inorganic components.Moreover,rigid inorganic layer can inhibit non-radiative recombination and enhance the luminescence of organic parts,which is a kind of luminous material with application prospect.However,there are few two-dimensional perovskites with high performance room temperature phosphorescence characteristics,and room temperature phosphorescence color is concentrated in short wavelength luminescence（blue,yellow and green）,while long wavelength luminescence is less（red and near infrared）.The heavy atom effect of two-dimensional cadmium-based perovskite system can promote intersystem crossing of singlet to triplet system,which is conducive to the realization of triplet luminescence.In this paper,by adjusting the alkyl chain length of organic components of two-dimensional cadmium-based perovskite and changing inorganic components,a series of two-dimensional perovskite materials with high performance room temperature phosphorescent properties were designed and successfully prepared.The concrete research contents are as follows:In this chapter,cadmium chloride is selected as the inorganic component,and 4-phenoxy benzylamine（4-POMA）and 4-phenoxy phenylethylamine（4-POEA）,two organic amine with different alkyl chain length,are selected as the organic component,two-dimensional cadmium-based perovskite materials（4-POMACC and 4-POEACC）are synthesized by liquid-phase method.Among them,4-POMACC shows green phosphorescence,and the room temperature phosphorescence lifetime can reach 254 ms;The 4-POEACC shows an orange-red color with a phosphorescent lifetime of 68 ms at room temperature.In addition,the quantum efficiency of the two materials is 9.50%and8.06%,respectively.Through theoretical calculation,it is found that the interline transiting constant of 4-POMA is greater than that of 4-POEA,which indicated that the interline transiting process is more likely to occur in 4-POMA,and effective three-line luminescence is realized.The results of layer spacing showed that the 4-POMACC layer spacing is 24.37?,which is much smaller than the4-POEACC layer spacing（29.73?）,indicating that the 4-POMACC layer stacking is closer than the4-POEACC layer,and the closer stacking is conducive to luminescence.Finally,based on the room temperature phosphorescence characteristics of 4-POMACC material,it is applied in the field of anti-counterfeiting.In this chapter,a series of two-dimensional perovskite P-MACC:x%Mn(x is the theoretical molar doping percentage of Mn²⁺)materials are prepared by doping Mn²⁺in the synthesized two-dimensional perovskite materials（P-MACC）with green room temperature phosphorescent properties.P-XRD results show that manganese doping does not change the layered structure of two-dimensional perovskite system.The Mn-doped material exhibits strong orange-red phosphorescence emission at625 nm,and its luminescence peak is due to the ⁴T₁→⁶A₁ transition of Mn²⁺.In addition,the quantum efficiency of two-dimensional perovskite P-MACC is greatly improved by manganese doping.The quantum efficiency of 20%Mn doped two-dimensional perovskite material is 66.38%,which is 7.6times higher than that of P-MACC two-dimensional perovskite material which is 8.69%.This is attributed to the fact that the doping of manganese ions provides a new luminous energy level,which can make the energy of the triplet state be absorbed by Mn²⁺,and the radiation recombination is enhanced.Finally,based on the orange-red light properties of P-MACC:20%Mn,the material is coated on the LED device,and the light-induced orange-red light emission is successfully realized.