Study On Synthesis And Upconversion Properties Of Yb/Er/Li/AZO Ceramic

In the world, as energy shortage become a serious problem, solar energy as sustainable energy is a major energy in the future. AZO has excellent photoelectric properties. When AZO is used as electrode of solar cell, only visible light can be absorbed. In this paper, AZO ceramics doped with Er3+ and Yb3+ are prepared by high temperature solid state method. And it possesses the property of up-conversion luminescence that can convert infrared light into visible light. After doping the Li+ ions in the ceramic, the intensity of up-conversion luminescence is further strengthened.This series of AZO ceramics are prepared by high temperature solid state method at different presintering temperature and sintering temperature.Through the tests of XRD, SEM, resistivity, Hall coefficient, up-conversion luminescence, it is found that the optimal presintering temperature and the optimal sintering temperature are determined by AZO structure, morphology, electrical resistivity and change of fluorescence. Under the optimal presintering and sintering temperature, AZO ceramics are prepared with different concentration of Er3+ and Yb3+. Efficient red and green emission are observed under excitation of 980 nm laser. With increasing concentration of rare earth ions, intensity of emission decreases firstly and then weaken. Then, the effect of rare earth ion concentration on up-conversion luminescence intensity is studied, and the impact of rare earth ions on AZO structure occupation of ions are analyzed by the means of XRD, ultraviolet absorption and resistivity. The test of power curve shows that red emission is two-photon process. Finally, the mechanism of up-conversion luminescence are analyzed. Ren emission is contributed to the transition from 4F9/2 energy level to 4I15/2 energy level, while green emission is contributed to transition from 2H11/2 or 4S3/2 energy level to 4I15/2 energy level.With the doping of Li+ ion, the Li+ occupy interstitial sites of AZO crystals and change the symmetry of AZO crystals. This change of the crystal symmetry reduces non-radiative transitions of rare earth ions and strengthens the intensity of up-conversion luminescence. The fluorescent emission is monochrome orange and change from red light to green light in CIE digram. By the power curve, the emission of red and green light are both two-photon process in AZO:Er3+/Yb3+/Li+. Through no interactive orthogonal experiment, The intensity of emission is strongest when concentration of Er3+ is 3mol%, concentrationof Yb3+ is 2mol% and concentration of Li+ is 4mol%. The AZO:Er3+/Yb3+/Li+ also shows a good property of monochrome.