Full visible spectra emission introduced by crystal-site engineering in beta-Ca-3(PO4)(2)-type solid solution phosphors for high quality white light emitting diodes application

摘要

Exploring the phosphors with full visible spectra emission in a single system to realize versatile color output is highly desired but still challenging for high quality phosphor converted white light emitting diodes (WLEDs). Here, inspired by the multiple crystallographic sites in beta-Ca-3(PO4)(2) structures and facile crystal-site engineering method, full visible spectra emission was obtained via the design of two kinds Ca9Y(PO4)(7)-Ca10Li(PO4)(7):Eu2+, Mn2+ and Ca9Y(PO4)(7)-Ca10Na(PO4)(7):Eu2+, Mn2+ solid solution phosphors. The structure characteristics and photoluminescence properties were investigated by the Rietveld refinement on the basis of X-ray diffraction data, density functional theory, and low/room/high temperature spectra. The nonlinear phase evolutions introduced by the disappearances of vacancy, decreases of polyhedron number and changes of occupying atom in the different five cationic sites aroused the redistributions of Eu2+ among the cationic sites, which achieved full visible spectra emission and then enabled the fabricated WLEDs to exhibit high color rendering index (CRI= 81.5) and low correlated color temperature (CCT= 4087 K) under 365 nm chip excitation. Moreover, the R9 value was further enhanced from 24.6 to 93.1 with the help of construction of Eu2+-Mn2+ energy transfer in selected phosphors, which improved the qualities of device with higher CRI and lower CCT (CRI= 95.1 and CCT= 3213 K). The new kinds of solid solution phosphors reported here could not only manipulate the redistributions of Eu2+ among different cationic sites for full visible spectra emission, but also pave a way to develop phosphors for high quality WLEDs.