Controllable and facile synthesis of CsPbBr3-Cs4PbBr6 perovskite composites in pure polar solvent.

Here, we present a single atomic supersaturated recrystallization method to synthesize the green-emitting CsPbBr3-Cs4PbBr6 perovskite composites in solid state with the highest PLQY of 40.8% in pure polar solvent. The component, morphology, and optical properties of the microcrystals can be tuned by varying growth time, the content of ammonium bromide, and bromine source. The developed method provides a new route to large-scale synthesize high quality perovskite composites emitters for light-emitting diodes.

Layered Structure Produced Nonconcentration Quenching in a Novel Eu3+-Doped Phosphor.

Energy migration (energy transfer among identical luminescence centers) is always thought to be related to the concentration quenching in luminescence materials. However, the novel Eu3+-doped Ba6Gd2Ti4O17 phosphor seems to be an exception. In the series of Ba6Gd2(1- x)Ti4O17: xEu3+ ( x = 0.1, 0.3, 0.5, 0.7, and 0.9) phosphors prepared and investigated, no concentration quenching is found. Detailed investigations of the crystal structure and the luminescence properties of Ba6Gd2(1- x)Ti4O17: xEu3+ reveal that the nonoccurrence of concentration quenching is related to the dimensional restriction of energy migration inside the crystal lattices. In Ba6Gd2Ti4O17, directly increasing the number of Eu3+ ions to absorb as much excitation energy as possible allows to achieve a higher brightness. The highly Eu3+-doped Ba6Gd2(1- x)Ti4O17: xEu3+ ( x = 0.9) sample can convert near-UV excitation into red light, whose Commission Internationale de l'Eclairage (CIE) coordinates are (0.64, 0.36) and the color purity can reach up to 94.4%. Moreover, warm white light with the CIE chromaticity coordinates of (0.39, 0.39), the correlated color temperature of 3756 K, and the color rendering index of 82.2 is successfully generated by fabricating this highly Eu3+-doped phosphor in a near-UV light-emitting diode chip together with the green YGAB:Tb3+ and blue BAM:Eu2+ phosphors.

White Light Emission and Enhanced Color Stability in a Single-Component Host.

Eu3+ ion can be effectively sensitized by Ce3+ ion through an energy-transfer chain of Ce3+-(Tb3+) n-Eu3+, which has contributed to the development of white light-emitting diodes (WLEDs) as it can favor more efficient red phosphors. However, simply serving for WLEDs as one of the multicomponents, the design of the Ce3+-(Tb3+) n-Eu3+ energy transfer is undoubtedly underused. Theoretically, white light can be achieved with extra blue and green emissions released from Ce3+ and Tb3+. Herein, the design of the white light based on these three multicolor luminescence centers has been realized in GdBO3. It is the first time that white light is generated via accurate controls on the Ce3+-(Tb3+) n-Eu3+ energy transfer in such a widely studied host material. Because the thermal quenching rates of blue, green, and red emissions from Ce3+, Tb3+, and Eu3+, respectively, are well-matched in the host, this novel white light exhibits superior color stability and potential application prospect.