Effect of a Rubidium Chloride Carrier Confinement Layer on the Characteristics of CsPbBr3 Perovskite Light-Emitting Diodes

This work describes the effect of a rubidium chloride (RbCl) interlayer in CsPbBr3 perovskite light-emitting diode (LED) structures. RbCl crystallites exhibited polyhedral structures and lattice parameters similar to those of CsPbBr3 perovskite crystallites. The lattice mismatch between the RbCl interlayer and CsPbBr3 active layer was only approximately 2%. The devices exhibited the best quality and performance when RbCl was used as the nucleation and carrier confinement layer. The crystallite sizes of CsPbBr3 with 0.2-, 0.5-, and 1-nm-thick RbCl bottom layers were 55.1, 65.4, and 55.1 nm, respectively. The full width at half maximum (FWHM) of the photoluminescence (PL) emission peak for CsPbBr3 with the RbCl bottom layer was 0.096 eV.

Synthesis and Characterization of Lightweight Beryllium Chloro Silicate Phosphor

In this chapter, low weight barium-based cholorsilicate Ba5Cl6Si2O6:Eu2+ is prepared through a solid-state reaction. To confirm the structure of the synthesized phosphors, powder photographs were obtained using an x-ray diffractometer. Photoluminescence spectra and FTIR spectra were recorded. Photoluminescence spectra are studied. The emission peak is observed at 407 nm at excitation 275 nm. The intense violet-blue emission is obtained. The broad excitation band and strong emission indicate that Ba5Cl6Si2O6:Eu2+could be a good phosphor candidate for blue LED and white LEDs. Decay curve indicates the phosphor has a long afterglow feature.

Developments of crystal structures and photoluminescence properties of Sr0.85Eu0.15Al12O19 green phosphors using different synthesis parameters

First, a solid-state reaction method was used to synthesize a [Formula: see text] phosphor at 1250[Formula: see text]C–1400[Formula: see text]C for 1 h, and its crystal structures and photoluminescence properties were investigated as a function of synthesis temperature. When the furnace reached the synthesis temperature, the 5% [Formula: see text] reduction atmosphere was infused and the reduction atmosphere was removed as the temperature was dropped to 800[Formula: see text]C. When 1200[Formula: see text]C was used as the synthesis temperature, the [Formula: see text], [Formula: see text], and [Formula: see text] phases co-existed; only one weak emission peak was observed in the photoluminescence excitation (PLE) spectra, and two weak emission peaks were observed in the photoluminescence emission (PL) spectra. When the [Formula: see text] phosphors were synthesized at a temperature higher than 1200[Formula: see text]C, the diffraction intensities of [Formula: see text], [Formula: see text], and [Formula: see text] phases were almost unchanged, but the crystal sizes of [Formula: see text] powders increased. For [Formula: see text] phosphors, PLE spectra had one broad exciting band with two centered wavelengths of 317 and 365 nm, and PL spectra had one emission band with one centered wavelength of 513 nm. As the synthesis temperature rose, the emission intensities of PLE and PL spectra increased. Second, we show that the removed temperature of reduction atmosphere of [Formula: see text] phosphors had an apparent effect on their emission properties of PLE and PL spectra.

Growth and scintillation properties of LiBr/CeBr3 eutectic scintillator for neutron detection

The 6LiBr/CeBr3 eutectic scintillator for thermal neutron detection has been developed due to achieving high 6Li concentration. The eutectics were grown by vertical Bridgman method. Molar ratio of 6Li in 6LiBr/CeBr3 eutectic is 35 %, which is higher than that of commercial neutron scintillators such Ce:LiCaAlF6 and Ce:Cs2LiYCl6. The grown eutectic had lamellar-type eutectic structure extending along the growth direction and optical transparency. The grown eutectics showed an emission peak at 360 and 380 nm ascribed to Ce3+ 4f-5d transition from CeBr3 scintillation phase. The measurements of scintillation performance of the 6LiBr/CeBr3 were performed using x-ray, gamma-ray and neutron irradiation to evaluate its potential as a neutron scintillator.

High-performance narrow spectrum green phosphorescent top-emitting organic light-emitting devices with external quantum efficiency up to 38%

In this work, we have experimentally demonstrated the efficacy of micro-cavity effect in realizing high-performance top-emitting organic light-emitting diodes (TEOLEDs). By optimizing the thickness of top Yb/Ag electrode and cavity length, highly efficient green TEOLED with external quantum efficiency as high as 38% was achieved. A strong dependence of electroluminescent (EL) performances and spectrum on cavity length was observed, and there was also a significant angle dependence of EL spectrum. Ultimately, ultra-high current efficiency up to 161.17 cd/A (3.2 V) was obtained by the device with emission peak at 552 nm, which is 35 nm longer than the intrinsic emission peak (517 nm) of utilized green emitter. Interestingly, this device displayed narrow emission with full-width at half-maximum (FWHM) of less than 20 nm, which was obtained by increasing the Ag layer thickness.

Luminescence and Crystalline Properties of InGaN-based LED on Si Substrate with AlN/GaN Superlattice Structure

A crack-free indium gallium nitride (InGaN) based light emitting diode (LED) grown on silicon (Si) substrate was successfully demonstrated by introducing aluminium nitride/gallium nitride (AlN/GaN) superlattice structure (SLS) in the growth of the LED. The luminescence and the crystalline properties of the LED were discussed. From photoluminescence (PL) surface mapping measurement, the emission wavelength of the LED (453 nm) was almost uniform across the LED epi-wafer area. Temperaturedependent PL revealed that the dominant emission peak of the LED was 2.77 eV at all temperatures. The emission peak was related to the quantum wells of the LED. Some additional peaks were also observed, in particular at lower temperatures. These peaks were associated to alloy fluctuations in the In0.11Ga0.89N/ In0.02Ga0.98N multiquantum wells (MQWs) of the LED. Furthermore, the dependence of PL intensity and PL decay time on temperature revealed the evidence related to indium and/or interface fluctuations of the quantum wells. From X-ray diffraction (XRD) ω-scan measurements, fringes of the AlN/GaN SLS were clear, indicating the SLS were grown with good interface abruptness. However, the fringes for the MQWs were less uniform, indicating another evidence of the alloy fluctuations in the MQWs. XRD-reciprocal surface mapping (RSM) measurement showed that all epitaxial layers of the LED were grown coherently, and the LED was fully under strain.

Fabrication and electroluminescence properties of alloyed CdSxSe1-x quantum dots-based LEDs

We report the facile synthesis of alloyed CdSxSe1-x QDs via one-pot method using simultaneous injection of Se and S source into a solution of the Cd precursor dissolved in a coordinating mixture of hexadecylamine and trioctylphosphine, during which the formation of CdSxSe1-x nanocrystals was controlled by growth time at a certain temperature of 260 oC. In particular, emission peak and full width at half maximum of photoluminescence (PL) of alloyed CdSxSe1-x QDs were tunable in a range of 588 - 604 nm and 36 - 38 nm, respectively, with a PL quantum yield up to 55 % by a reaction time of 60 min. Importantly, the structural advantage of alloyed CdSxSe1-x QDs based LEDs have been fabricated and their electroluminescence properties were characterized. A good performance device with a maximum luminance and luminous efficiency of 761 cd/m2 and 0.82 cd/A was obtained, respectively.

Preparation of Eu0.075Tb0.925-Metal Organic Framework as a Fluorescent Probe and Application in the Detection of Fe3+ and Cr2O72−

Luminescent Ln-MOFs (Eu0.075Tb0.925-MOF) were successfully synthesised through the solvothermal reaction of Tb(NO3)3·6H2O, Eu(NO3)3·6H2O, and the ligand pyromellitic acid. The product was characterised by X-ray diffraction (XRD), TG analysis, EM, X-ray photoelectron spectroscopy (XPS), and luminescence properties, and results show that the synthesised material Eu0.075Tb0.925-MOF has a selective ratio-based fluorescence response to Fe3+ or Cr2O72−. On the basis of the internal filtering effect, the fluorescence detection experiment shows that as the concentration of Fe3+ or Cr2O72− increases, the intensity of the characteristic emission peak at 544 nm of Tb3+ decreases, and the intensity of the characteristic emission peak at 653 nm of Eu3+ increases in Eu0.075Tb0.925-MOF. The fluorescence intensity ratio (I653/I544) has a good linear relationship with the target concentration. The detection linear range for Fe3+ or Cr2O72− is 10–100 μM/L, and the detection limits are 2.71 × 10−7 and 8.72 × 10−7 M, respectively. Compared with the sensor material with a single fluorescence emission, the synthesised material has a higher anti-interference ability. The synthesised Eu0.075Tb0.925-MOF can be used as a highly selective and recyclable sensing material for Fe3+ or Cr2O72−. This material should be an excellent candidate for multifunctional sensors.