Abstract
Cu+-activated aluminosilicate oxyfluride glasses were successfully synthesized by melt quenching method in air with adding Al powder as reducing agent. Their luminescent properties were studied systematically via optical absorption, excitation and emission spectra. Upon UV irradiation, a blue-emitting band of Cu+ with relatively low optical basicity is observed. By increasing optical basicity of glass, obviously red shifts of excitation (290→313 nm) and emission (435→470 nm) peaks can be obtained. Through enhancing Cu+ content, excitation and emission bands present further redshifts, which shift from 313 to 338 nm and from 470 to 560 nm, respectively. It is proposed that the absorption band and emitting color of Cu+-doped glass could be tuned by changing the optical basicity of glass and Cu+ concentration. The highest quantum yield can reach 62.5%. More importantly, investigation of the thermal stability displays that over 91% of the room temperature luminescent intensity still preserves at 200 °C. These results infer that Cu+-activated aluminosilicate oxyfluride glasses may be utilized for UV converted W-LEDs.
Highlights
Nowadays, ultraviolet (UV)-converted white light-emitting diodes (W-LEDs) have gained significant attention because they have a lower color temperature and a higher color-rendering index compared with those of commercial W-LEDs (Schubert and Kim, 2005; Pimputkar et al, 2009; Shang et al, 2014; Li et al, 2015; Zhou et al, 2015; Lu et al, 2017)
One of the most popular ways to realize UV-converted W-LEDs is through the integration of UV LED chips with single-phase white light-emitting phosphors, of which organic resins are always applied as encapsulating materials (Huang et al, 2017; Wei et al, 2018b)
Compared with the host P0 sample, redshifts of the absorption edge are observed in Cu+-doped glasses, which can be attributed to the absorption of Cu+, corresponding with the transition from ground d state to excited s state (Zhang et al, 2009)
Summary
Ultraviolet (UV)-converted white light-emitting diodes (W-LEDs) have gained significant attention because they have a lower color temperature and a higher color-rendering index compared with those of commercial W-LEDs (Schubert and Kim, 2005; Pimputkar et al, 2009; Shang et al, 2014; Li et al, 2015; Zhou et al, 2015; Lu et al, 2017). The encapsulating materials deteriorate and turn yellow when the device operates at a higher driving current, giving rise to the shift of luminescence and the degradation of luminous efficiency and longterm reliability To avoid this deficiency, an alternative strategy for the combination of UV LEDs with white light luminescent glasses is expected to be developed. Luminescent glasses exhibit simple preparation, low production costs, excellent physical and chemical stability, high transparency, and outstanding optical properties They present as free of epoxy resin in encapsulation (Dong et al, 2015; Meza Rocha et al, 2016; Kapoor et al, 2017; Ghosh et al, 2018; Li et al, 2019). In order to figure out the thermal quenching performance of glasses, temperature-dependent emission intensities were achieved using a FS5 spectrofluorometer applied with a TCB1402C temperature controller (China)
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