| Rare earth doped up-conversion nano luminescent materials are those can transform photons with low energy to photons with high energy by multi-photons and energy transmission processes. Compared to fluorescent dyes, quantum dot materials, rare earth doped up-conversion nano luminescent materials possess non-toxic, high optical and chemical stability, long luminescence lifetime, narrow luminescence FWHM, etc. Furthermore, because the excitation sources are normally infra-red light, it can avoid the interference of fluorescent background on biological samples and improve signal-noise ratio effectively. Meanwhile, penetration depth and low injury to cell are other advantages. Hence, rare earth doped up-conversion nano luminescent materials are widely applied on biological detection, cell imaging,3D displays, anti-counterfeiting, solar cells, solid lasers and sensors. Therefore, the optimization of preparation method, the functional design and the material structure design of rare earth doped up-conversion nano luminescent materials are hot issues in luminescence domains.Recently, the unsolved problems of rare earth doped up-conversion nano luminescent materials are:(1) With the decrease of the nano materials size, their luminescence intensity decreases sharply; (2) Optimization the morphology of nano materials, crystal structure; (3) Using surface modified method, ligand-exchange method to realize the functionalization of up-conversion luminescence materials; (4) Exploration the applications of rare earth doped up-conversion nano luminescent materials. In this paper, Solvothermal Method is used to prepare the shape, size and controllable NaYF4 up-conversion nano luminescent materials. The ions doping is investigated to realize the morphology, the particle diameter and optical characteristics controllable, while surface modification is investigated to realize the performance optimization of materials.The main achievements in the paper are as follows:The ions doping effects on the NaREF4 family up-conversion luminescent fluoride materials were investigated systematically. The effects of ions density of luminescent center, rare earth ions doping of non-luminescent center and positive ions doping on properties of materials were studied. The effects of positive ions K+ doping on up-conversion luminescent materials were also discussed:with appropriate positive ions doping, the luminescent intensity of materials was improved.The surface modification and coating of nano materials impact significantly on luminescent properties and water-solubility. It infers that homogeneous coating can solve the surface quenching problems efficiently and The active shell can improve luminescent intensity obviously than non-active shell. SiO2 coating can transfer nano materials from oil soluble to water soluble. The effects of CuS coating on up-conversion materials luminescence were investigated, inferring that CuS system plasma resonance will decrease the luminescence intensity. The ligand exchange processes between inorganic compound and up-conversion nano materials were studies for the first time.Furthermore, we introduced rare earth doped up-conversion nano luminescent materials to organic solar cells for the first time and investigated the effect of up-conversion nano materials on PTB7:PC70BM family solar cells properties. They are doped into PTB7:PC70BM to enhance the absorption of active layer. A series of devices with different rate of doping were prepared, inferring that devices with doping intensity of 3% reach performance optimum with PCE increase from 7.22% to 8.83%. In summary, the doping up-conversion materials can improve efficiently the PCE of solar cells. |
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