Emission In Broad Range Research Articles

Simple synthesis of AgInS2/ZnS core/shell quantum dots with wide tunable emission wavelength for white light-emitting diodes

Phosphor with efficient and broad range emission is necessary for lighting applications. I-III-VI group quantum dots (QDs) have the advantages of non-toxic composition and large adjustable spectrum range, and have potential applications in the field of lighting. However, the efficient luminescence of these QDs at shorter wavelengths still needs further study, which is crucial for the development of high color rendering index white light LED devices (WLEDs). In this work, wide visible range emitting AgInS2/ZnS QDs with broad band and high luminous efficiency were obtained by altering the Ag/In ratios and Zn2+ inter-diffusion with cation of AgInS2. Photo-luminescent (PL) wavelength range of the obtained core-shell structured AgInS2/ZnS extended from 703 nm to 524 nm with high PL quantum yield (QY) and stability. The champion device based on the optimized AgInS2/ZnS QDs exhibits warm white light (correlated color temperature = 3652 K) characteristics with high color rendering index (CRI Ra) of 92.85 while maintaining excellent color stability under different driving currents. These properties are far superior to those of WLEDs with YAG phosphor.

Structural and optical properties of H2 diluted c-Si/a-SiO x core-shell silicon nanowire

We observed photoluminescence quenching in crystalline (c) Si/amorphous (a) SiOx core-shell silicon nanowires (Si-NWs). We observed that the photoluminescence (PL) intensity strongly depends on the stoichiometry of outer a-SiOx matrix, which was characterized by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The PL showed a broad-range emission from 1.6 to 2.4 eV with the peak centered at 2.27 eV, which quenched as the oxygen content decreased from 60.5 to 54.6 at.%. Both transverse optic and longitudinal optic signatures of Si–O–Si were shifted to lower wavenumbers, which indicate the modification of chemical networks in core-shell Si-NWs. The minority carrier life time (τ) increased from 3.4 to 7.5 µs as the diameter of core Si increased from 22 to 78 nm, indicating the decrease of trap densities and alternation trap states. The reason for PL quenching is mostly attributed to the structural and stoichiometry changes in outer a-SiOx of c-Si/a-SiOx-NW.