A high-performance metal halide perovskite-based laser-driven display.

Laser-driven liquid crystal displays (LCDs) comprising metal halide perovskites (MHPs) as the blue-to-green/red color converters are at the forefront of ongoing intense research on the development and improvement of display devices. However, the inferior high photoluminescence quantum yield (PLQY) of MHPs under the excitation of high-power blue light and photoluminescence deterioration at high temperatures remain major concerns. Herein, we design a kind of octylamine-modified MHP via binding energy engineering, and the synthesized materials show PLQY of 97.6% under the excitation of a blue laser at 450 nm. Meanwhile, this design endows a structural self-healing ability to achieve a high PLQY and luminescence stability under high temperature (90 °C) and high flux excitation (386 mW cm-2). The blue light-excitable MHPs with a near unity PLQY, strong stability, and low PLQY deterioration are further encapsulated into a laser-driven LCD device. This prototype demonstrates excellent color gamut (132% NTSC, 98% Rec. 2020), illuminance intensity (>10 000 lux), and energy consumption (47.5% of commercial consumption), and hence is expected to be beneficial for the reduction of energy consumption in backlight display devices, particularly in large-screen outdoor displays.

Highly Thermotolerant Metal Halide Perovskite Solids.

By virtue of their narrow emission bands, near-unity quantum yield, and low fabrication cost, metal halide perovskites hold great promise in numerous aspects of optoelectronic applications, including solid-state lighting, lasing, and displays. Despite such promise, the poor temperature tolerance and suboptimal quantum yield of the existing metal halide perovskites in their solid state have severely limited their practical applications. Here, a straightforward heterogeneous interfacial method to develop superior thermotolerant and highly emissive solid-state metal halide perovskites is reported and their use as long-lasting high-temperature and high-input-power durable solid-state light-emitting diodes is illustrated. It is found that the resultant materials can well maintain their superior quantum efficiency after heating at a temperature over 150 °C for up to 22 h. A white light-emitting diode (w-LED) constructed from the metal halide perovskite solid exhibits superior temperature sustainable lifetime over 1100 h. The w-LED also displays a highly durable high-power-driving capability, and its working current can go up to 300 mA. It is believed that such highly thermotolerant metal halide perovskites will unleash the possibility of a wide variety of high-power and high-temperature solid-state lighting, lasing, and display devices that have been limited by existing methods.

Hybrid coordination-network-engineering for bridging cascaded channels to activate long persistent phosphorescence in the second biological window.

We present a novel "Top-down" strategy to design the long phosphorescent phosphors in the second biological transparency window via energy transfer. Inherence in this approach to material design involves an ingenious engineering for hybridizing the coordination networks of hosts, tailoring the topochemical configuration of dopants, and bridging a cascaded tunnel for transferring the persistent energy from traps, to sensitizers and then to acceptors. Another significance of this endeavour is to highlight a rational scheme for functionally important hosts and dopants, Cr/Nd co-doped Zn1-xCaxGa2O4 solid solutions. Such solid-solution is employed as an optimized host to take advantage of its characteristic trap site level to establish an electron reservoir and network parameters for the precipitation of activators Nd(3+) and Cr(3+). The results reveal that the strategy employed here has the great potential, as well as opens new opportunities for future new-wavelength, NIR phosphorescent phosphors fabrication with many potential multifunctional bio-imaging applications.

A long persistent phosphor based on recombination centers originating from Zn imperfections.

The recombination luminescence from Zn imperfections has been extensively investigated; however, there have been few reports on the long persistent luminescence of Zn imperfections as emitting centers. Here, we observed a long persistent luminescence in blue-white visible region from 6 ZnO:3 GeO2:Al2O3 phosphor with Zn imperfections as emitting centers. Persistent luminescence could be observed beyond 2h with naked eyes. The properties of traps were also elaborated by the measurements of thermo-luminescence spectra and photo-stimulated luminescence decay curves. Furthermore, a long persistent phosphor with warm white color was developed by doping Cr(3+) into 6 ZnO:3 GeO2:Al2O3 phosphor.

Enhanced luminescence in SrMgAl(x)O(17±Î´):yMn4+ composite phosphors.

Red-emitting SrMgAlxO17±Î´:yMn(4+) composite phosphors (x=10-100; y=0.05-4.0 mol%) are synthesized by solid-state reaction method in air. Addition of Al2O3 leads to the formation of two concomitant phases, i.e., SrMgAl10O17 and Al2O3 phases in the composite phosphor. Red emission from Mn(4+) ions in the composite phosphors is greatly enhanced due to multiple scattering and absorption of excitation light between SrMgAl10O17 and Al2O3 phases. SrMgAlxO17±Î´:yMn(4+) composite phosphors would be a promising candidate as red phosphor in the application of a 397 nm near UV-based W-LED.

Investigation of energy transfer mechanisms between Bi(2+) and Tm(3+) by time-resolved spectrum.

Here, we report for the first time the optical properties of Bi(2+) and Tm(3+) co-doped germanate glasses and elucidate the potential of this material as substrates to improve the performance of CdTe solar cell. A strong emission peak at 800nm is observed under the excitation of 450-700nm in this material. The energy transfer processes from the transitions of Bi(2+) [(2)P3/2(1)→(2)P1/2]: Tm(3+) [(3)H6→(3)H4] are investigated by time-resolved luminescence spectroscopy. A cover glass exhibiting an ultra-broadband response spectrum covering the entire solar visible wavelength region is suggested to enhance the conversion efficiency of CdTe solar cells significantly.

Enhanced broadband near-infrared luminescence of Bi-doped oxyfluoride glasses.

Broadband near-infrared luminescence covering 900 to 1600 nm has been observed in Bi-doped oxyfluoride silicate glasses. The partial substitution of fluoride for oxide in Bi-doped silicate glasses leads to an increase of the intensity and lifetime of the near-infrared luminescence and blue-shift of the near-infrared emission peaks. Both Bi-doped silicate and oxyfluoride silicate glasses show visible luminescence with blue, green, orange and red emission bands when excited by ultra-violet light. Careful investigation on the luminescence properties indicates that the change of near-infrared luminescence is related to optical basicity, phonon energy of the glass matrix and crystal field around Bi active centers. These results offer a valuable way to control the luminescence properties of Bi-doped materials and may find some applications in fiber amplifier and fiber laser.

Comment on "Synthesis, functionalization and bioimaging applications of highly fluorescent carbon nanoparticles" by Sourov Chandra et al., Nanoscale, 2011, 3, 1533.

A recent paper in this journal reported the synthesis of highly fluorescent crystalline carbon nanoparticles by microwave irradiation of sucrose with phosphoric acid. The emission wavelengths reported in this investigation are always twice the corresponding excitation wavelengths and the full widths at half maximum are extremely small (15-20 nm). We suggest that their results and discussions are questionable. Detailed analysis indicates that the fluorescence may not be real fluorescence, but the second order diffraction of excitation light.