Search

White light emitting diodes (LEDs) suffer from two most common drawbacks: the deficiency of the red component and the poor thermal stability of silicone. Ce3+-doped garnet phosphors with tailor-made luminescence properties can be achieved by variations in {A}, {B}, and {C} cation sites. Herein, a simultaneous ion co-substitution design strategy has been adopted to synthesize a series of (Y, Ca)3(Al, Mg)2(Al, Si)3O12 garnet phosphors and corresponding phosphor-in-glass (PiG) films. The co-substitution is finely restricted to the assigned sites. The emission peak is shifted from 529 to 565 nm, which is beneficial to obtain low color temperatures and high color rendering using a single phosphor for white LEDs. By employing the as-synthesized phosphor, the corresponding PiG films were fabricated by the low temperature co-sintering technology using the SiO2–B2O3–ZnO–Na2O glass system characterized with excellent thermal stability and moisture resistance. The morphological and elemental analyses demonstrated that the as-made phosphor powders were uniformly distributed in the glass host without any interfacial reactions. Finally, modular white LEDs with a high color rendering (Ra = 82.7) is achieved through the as-synthesized PiG film on an InGaN blue chip. This study may open up a facile approach to obtain high quality luminescence based on the mono-luminescence center, avoiding excitation energy wastage and low quantum efficiency aroused by multi-luminescence centers or color compensation phosphors in glass. [ABSTRACT FROM AUTHOR]

Using a green and convenient method to prepare fluoride red phosphor is an important challenge for industrialization applications. In this work, K2SiF6:Mn4+ red phosphor was successfully prepared through a brief one-step co-precipitation method without HF. A simplified and non-toxic ion exchange strategy for the formation of narrow-band red-emitting K2SiF6:Mn4+ phosphors was developed using different solvent (HAc, H3PO4, HNO3, HCl, H2O). The photoluminescence intensity of the prepared K2SiF6:Mn4+ red phosphor was the highest when the pH of the reaction solution was 1.0. Furthermore, using K2SiF6:Mn4+ as red component, the warm white light LED (light-emitting diode) with low correlated color temperature (CCT = 4095 K), high color rendering index (CRI, Ra = 87) was achieved, which proved that the phosphor synthesized by this method had great application potential. The preparation method provided in this article is safer and more environmentally friendly, and has important commercial and social value. [ABSTRACT FROM AUTHOR]

In this work, a novel red-emitting oxyfluoride phosphor Na2NbOF5:Mn4+ with an ultra-intense zero-phonon line (ZPL) was successfully synthesized by hydrothermal method. The phase composition and luminescent properties of Na2NbOF5:Mn4+ were studied in detail. The photoluminescence excitation spectrum contains two intense excitation bands centered at 369 and 470 nm, which match well with commercial UV and blue light-emitting diode (LED) chips. When excited by 470 nm blue light, Na2NbOF5:Mn4+ exhibits red light emission dominated by ZPL. Notably, the color purity of the Na2NbOF5:Mn4+ red phosphor can reach 99.9%. Meanwhile, the Na2NbOF5:Mn4+ phosphor has a shorter fluorescence decay time than commercial K2SiF6:Mn4+, which is conducive to fast switching of images in display applications. Profiting from the intense ZPL, white light-emitting diode (WLED) with high color rendering index of Ra = 86.2 and low correlated color temperature of Tc = 3133 K is realized using yellow YAG:Ce3+ and red Na2NbOF5:Mn4+ phosphor. The WLED fabricated using CsPbBr3 quantum dots (QDs) and red Na2NbOF5:Mn4+ phosphor shows a wide color gamut of 127.56% NTSC (National Television Standard Committee). The results show that red-emitting Na2NbOF5:Mn4+ phosphor has potential application prospects in WLED lighting and display backlight. [ABSTRACT FROM AUTHOR]

The discovery of pure-red emitting phosphor is great meaningful for the achievement of high color rendering index white light emitting diodes, but still a challenge due to the strict crystal field limitations. In this work, we demonstrate the preparation of a 630 nm pure-red emitting Ca 3 Si 2 O 7 :Eu2+ phosphor for the first time through a CO reduction strategy. The changes in crystal field strength caused by different methods for the preparation of Ca 3 Si 2 O 7 :Eu2+ are investigated and discussed based on the understanding of the thermodynamic theory and structure resolution. Finally, a white light-emitting diode with a high color rendering index (Ra = 98) is accomplished by combining the as-prepared Ca 3 Si 2 O 7 :Eu2+ pure-red emitting phosphor with a 375 nm chip and the commercial used blue and green phosphors. The results also demonstrate the generalizability of the weak reduction strategy for the exploration of "redder" Eu2+ doped phosphors. Pure-red emitting Ca 3 Si 2 O 7 :Eu2+ phosphor was developed by solid state reaction under CO reduction based on the understanding of the thermodynamic theory. Benefiting by the weaker reduction minimizes the impact on the initial crystal field, Eu2+ ions thus presenting an unprecedented 630 nm emission in the as prepared stronger crystal field silicate matrix. [Display omitted] • Pure-red phosphor Ca 3 Si 2 O 7 :Eu2+ was prepared by solid state reaction under CO reduction atmosphere. • The reducing activity of CO is weaker than that of H 2 at 1250 °C according to the thermodynamic theory. • Weak reduction minimizes the impact on the initial crystal field. [ABSTRACT FROM AUTHOR]