Study On Rare Earth Doped BiOCl Stocks And Anti - Stocks Specific Luminescence

Along with the progress of lighting display and semiconductor light emitting device, rare earh (RE) doped semiconductor material have received much attention due to their unique optical properties and potential applications in many technical fields. RE ions and semiconductor materials are good luminescent materials, the effective combination of both can give birth to high efficiency light or laser devices have been the focus of numerous investigations.BiOCl is a type of semiconductor material with a band gap of3.5eV. In recently years, BiOCl has drawn considerable attention for photocatalysts and magnetic materials because of its unique electronic structure and catalytic performance. However, BiOCl, which not only has good optical performance, but also relatively low phonon energy, favorable physical properties and high chemical durability, is very suitable for acting as host of luminescence. More importantly, BiOCl possesses special energy band and crystal structure, when RE ions doped which can formation strong coupling effect.Among the trivalent RE ions, Er3+and Eu3+ions is most important fluorescent photoactive for upconversion (anti-Stocks) and downconversion (Stocks), respectively. Because they exhibiet excellent luminescent properties, and have significant interaction between the host material and luminescent properties, which may explore the relationship between host structure and properties of RE luminescent. Based on Er3+and Eu3+doped BiOCl, we have preformed systematic investigations on light-matter interaction through synthesis, crytals structural and ions doping.We found the novel Er3+ion activtated multi-band photon avalanche (PA) from Er3+doped BiOCl. Under980nm excitation, when exceed the pump power threshold (70W/cm2), the PA UC from the2H9/2(violet),2H11/2/4S3/2(green),4F9/2(red) and2I13/2(NIR) levels of Er3+ions were observed. This is different from traditional PA behavior. In Er3+/Yb3+co-doped BiOCl crystals, as Yb3+ions concentration increases, although the emission intensity increases but the value of n decreased significantly. And the PA phenomena of all emission bands are close to disappearance when the concentration of Yb3+dopants reaches at a critical concentration. Different with Yb3+dopants, althought Li+ions doped in BiOCl:Er3+can greatly enhance the green and red UC emission, but do not degenerate the PA behaviors of Er3+ion.Compared with bulk material, BiOCl:Er3+nanocrystals showed different phenomenon in UC emission. We were not observed the PA phenomena of BiOCl:Er3+nanocrystals synthesized by hydrothermal method. With increase the Yb3+concentration, the absorption edge of samples red-shifts and forming impurity energy level in Er3+/Yb3+co-doped BiOCl nanocrystals, and the green and red UC emission from three-photon changed to two-photon processes gradually with increase in Yb+ion concentration. However, the PA phenomena of BiOCl:Er3+nanocrystals through solvent-thermal synthesis were observed. Interesting, the NIR emission of BiOCl:Er3+ nanosheets even presents n value more2below the threshold power, which show different interaction between light and materials. On tuning the surfactant addition, solvent content and pH value in synthesis, the cycle numbers for the UC and NIR PA processes could be modified accordingly.For Eu3+-doped BiOCl phosphor, it also shows unique emission behavior. The first-principles calculations and diffuse reflectance spectra indicated that Eu3+ions dopant resulted in forming impurity energy level. The excitation spectra shows that it has excellent broadband NUV-exciting ability, which due to the electronic transitions from the valence band to conduction band, and indicated that the Eu3+emissions can be achieved via an efficient ET process from the BiOCl host to Eu3+. Under358nm excitation, the quantum efficiencies reached70%, which indicate that Eu3+-doped BiOCl phosphor is a promising red phosphor for WLEDs. Importantly, the special Eu3+emission properties in BiOCl lie in the abnormally highest emission intensity of BiOCl from the5D0â†'7F4transition (699nm, far-red) of Eu3+ions, contrary to most of the Eu3+-activated phosphors whose highest emission intensities are from either5Doâ†'7F1(595nm) or5D0â†'7F2(615nm) transition. In the nanocrystals, the BiOCl:Eu3+also prosses broadband NUV-exciting ability. Compared with the bulk material, the excitation spectra blue shift, emission intensity decrease, which is due to increase the surface defect with decreasing particles size. On the other hand, the sample exhibit more superior far-red light emission, which extending their potential applications of Eu3+ions.