| In the 1990s, Shuji Nakamura has made unprecedented breakthroughs in InGaN/GaN-based blue-emitting LED chips, which can exhibit higher electroluminescence efficiency, better stability, and also can be made with easy mass production. The white-emitting LED-based solid-state lighting (SSL) shows varios kinds of applications in many fields, such as backlights for liquid-crystal display, point-source imaging and general illumination. Currently, the commercial available strategy to produce a white-emitting LED (WLED) is by combining a blue LED chip with yellow-emitting (Y, Ga)3(Ga, Al)5O12:Ce3+ phosphor using organic epoxy resin. Unfortunately, this route suffers many intrinsic drawbacks, such as chromatic aberration, poor correlated color temperature (CCT) and complicated procedure processes. Consequently, UV-pumped full-color-emitting inorganic glass phosphors can be employed as the sealant materials for WLED devices.Compared with conventional crystal phosphors, tunable full-color emitting glasses are considered as promising candidates for use in UV-driven WLEDs due to various excellent advantages, such as low chromatic aberration, epoxy resin-free, excellent physical and chemical stability. It is notable that borosilicate-based glass systems exhibit many unique optical phenomena and have better chemical and physical properties. As a result, our research is mainly focused on Ce3+/Sn2+/Cu+-doped borosilicate-based glasses, aiming to discuss the mechanisms of tailorable full-color emitting in amorphous matrix. The principal contents in the thesis have been listed as follows:Firstly, a series of tunable full-color emitting Mn2+/Ce3+/Tb3+-doped 15CaO-55B2O3-30SiO2 (CBS) glasses were fabricated in air via a melt-quenching technique. The PL spectra and decay curves demonstrate that there are dual energy-transfer (ET) processes of Ce3+â†'Tb3+ and Ce3+â†'Mn2+in CBS:0.04Ce3+, yTb3+, zMn2+ glasses. When the doped content of Ce3+ is fixed, the emission hue, the CCT and the color rendering index (CRI) can be widely tuned through adjusting Tb3+/Mn2+ contents. After optimization, the CCT and CRI of CBS:0.04Ce3+,0.56Tb3+ 1.50Mn2+ glass sample were measured and calculated to be 4380 K and 88.4, respectively.Secondly, wide-range-accommodative full-color emission was first demonstrated in Mn2+/Sn2+/Tb3+-doped 20CaO-50B2O3-30SiO2 (CBSS) glasses, and the emission properties of ns2-type Sn2+ single doped CBSS were also investigated. Upon UV-light excitation, CBSS:xSn2+ exhibits blue emission band peaked at 398 nm in 320-370 nm, owing to Tiâ†'S0 relaxation of Sn2+ CBSS:xSn2+has the largest PL intensity when x=2.5 due to the concentration quenching effect of Sn2+ ions. The effect of glass structure on Sn2+ valence in mB2O3-(70-m)CaO-30SiO2-2.5Sn2+ glasses was also discussed, and results suggest that the B2O3-rich glasses exhibit stronger PL intensities because they have more Sn2+ cations instead of Sn4+. The reduction mechanism of Sn4+to Sn2+ was then carefully discussed. Besides, dual ETs of Sn2+â†'Mn2+ and Sn2+â†'>Tb3+ were systematically demonstrated in CBSS:xSn2+,yTb3+, zMn2+ glasses, and tunable full-color emission with low CCT (3384-6924 K) can be realized through adjusting their ET ratio by tuning the doped concentration of Tb3+ or Mn2+ cations in CBSS. Moreover, increasing the glass composition of B2O3, the dual ETs of Sn2+â†'Mn2+ and Sn2+â†'Tb3+ could be monotonously enhanced, and the mechanism of the enhancement is also discussed systematically. These UV-induced converting glasses show potential applications in lighting and display fields.Thirdly, a series of emission-tunable Tb3+-Cu+-Mn2+-doped 50SiO2-30CaF2-8B2O3-7Al2O3-5Na2O (SBF) oxyfluoride glasses were synthesized, and the the species and formation of copper, i.e., Cu+, Cu2+, Cu0 and Cu NPs in SBF glasses have been analysed as well. Results indicate that there is coexistence of Cu+ and Cu2+ in SBF glasses, and Cu NPs were not in the SBF glass host. Under the excitation of 284 nm, SBF:0.2Cu+ shows blue emission band peaked at 440 nm, originating from the sâ†'d transition of Cu+cations instead of Cu2+ or Cu NPs. There are dual ETs of Cu+â†'Mn2+ and Cu+â†'Tb3+ in SBF:xCu+, yTb3+, zMn2+ glasses, and appropriate addition of SnO in this system could promote the reduction of Cu2+ to Cu+ which could further enhance the emission intensity of Cu+ and the ETs processes from Cu+ to Mn2+/Tb3+. Interestingly, a full-color-tunable emitting from blue to green, and to orange-red region, and ideal white-light emission (x=0.33, y=0.32) were realized in SBF:xCu+, yTb3+, zMn2+ glass samples by precisely tuning the contents of Mn2+/Tb3+. These glass phosphors show potential applications in deep-UV and high-power light sources pumped optical devices and fluorescent lamps. Besides, the interplay between Tb3+ and Cu+ was further systematically investigated via Cu+-Na+ ion-exchanged method. Our research promotes the development of glass phosphors for WLEDs. |
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