Er ~ 3 + (eu ~ 2 +) / Yb ~ 3 + Co-doped Fluoride Calcium Phosphate Nano-glass Spectrum Modulation

In 1954, Chapin et al developed first photoelectric conversion mono-crystalline silicon solar battery and the efficiency of it is about 6%. This is the symbol of modern solar cells. For a long time, silicon purification and complex material processing technology were constantly used to improve photoelectric conversion efficiency of the silicon solar cells. Due to the bandgap of crystalline silicon is about 1.12 eV, which correspond with wavelength only for 1100 nm. Thus, the wavelength of sunlight shorter than 1100 nm can be absorb by crystalline silicon and generate electron-hole pairs, then occur photoelectric conversion in silicon-based solar cells. The infrared wavelengths that is more than 1100 nm can not be used by silicon-based solar cells due to low energy,which caused about 25% sunlight energy losses. In addition, effective response spectrum of silicon crystals for sunlight is larger than 400 nm. The ultraviolet light of wavelength less than 400 nm also cannot be used by silicon-based solar cells. Furthermore, the sunlight in 400-1100 nm, only an electronic-hole pair can be generates while the silicon-based solar cells absorbs a photon, as well as, the surplus energy convert to heat by the no radiation form and transfer to surrounding.For this part about 30% of the solar energy lost. Therefore, effective response spectrum range of solar spectrum and heating effect of existence limited photoelectric conversion efficiency.At present, broadband spectral modulation by means of upconversion or quantum cutting has been widely studied to improve photoelectric conversion efficiency. Through this method, the sunlight of shorter than 400 nm and larger than 1100 nm change into the range which can be used by silicon-based solar cells. Therefore, broadband spectral modulation method is different from using silicon improvement and device performance optimization. This method offer new ideas to improve photoelectric conversion efficiency of silicon-based solar cells.In this paper, the rare earth ions doped transparent glass-ceramics containing Ca5(PO4)3F nano-crystals were prepared. X-ray diffraction and transmission electron microscopy analyses evidenced the crystallites is fluorine calcium phosphate nanocrystals. TEM images showed that Ca5(PO4)3F nano-crystals of 10-20 nm in diameter precipitated uniformly in the glass matrix, which is similar to the result of this calculated by Scherrer equation. Absorption and luminescence spectrum of the Eu2+/Yb3+ and Er3+/Yb3+ co-doped glasses and glass-ceramics has been studied. This experiment was adopted to study sensitization agent Yb3+ ions concentration to the luminescence of upconversion and quantum cutting Energy transfer mechanism between Eu2+-Yb3+ and Er3+-Yb3+ was discussed. The article analysis the energy transfer and quantum cutting spectral modulation process of the Eu2+ between Yb3+ in the ultraviolet and short-wave blu-ray excitation. By changing the doping Yb3+ concentration and heat treatment time to study fluorine calcium phosphate glass and glass ceramics' luminescence properties. Compared the luminescence intensity of the glass and glass ceramics, and the luminescence intensity in the glass ceramics is obviously enhance than that in the glass. In addition, the energy transfer mechanism of quantum cutting in the Eu2+/Yb3+ co-doped glass ceramics has been studied. Meanwhile, the research analysis the energy transfer and upconversion process of the Er3+ between Yb3+ in the near-infrared area. By changing the doping Yb3+ concentration and excitation power to study fluorine calcium phosphate glass and glass ceramics' luminescence properties. Compared the upconversion luminescence intensity of the glass and glass ceramics, and the luminescence intensity in the glass ceramics is obviously enhance than that in the glass.luminous properties of glass-ceramics, and the luminescence intensity in the glass ceramics is obviously enhance than that in the glass. The energy transfer mechanism of upconvertion in the Eu2+/Yb3+ co-doped glass ceramics has been studied. Through the rare earth ions Eu3+ as probes to discover that the rare earth ions have chosen enter into the fluoride phosphate calcium microcrystal and the energy transfer and luminescence efficiency improved significantly in the glass ceramics. From the experiment results that rare earth ions doped fluorine calcium phosphate glass ceramics is considered to be a promising material in silicon-based solar cells.