Search

In this manuscript we investigated the influence of Au nanoparticles on electrical and electroluminescent (EL) performances in organic light-emitting diodes (OLEDs) via doping as-synthesized Au nanorods (NRs) or nanocubes (NCs) into hole transport layer (HTL). Through accurately controlling the distance between the Au NRs and the emitting layer, altering the guest emitter’s lifetime, and replacing Au NRs with Au NCs to satisfy a better spectrum overlap with the emission guest, we got a conclusion that doping Au NRs or NCs into HTL has no significant influence on the device’s electrical and EL performances, although we observed an increase in the spontaneous emission rate in a fluorescent material by the exciton-surface plasmon-coupling. Our results suggest that a further research on emission mechanism in surface plasmon-enhanced OLEDs is still in process.

Flexible warm-white top-emitting organic light-emitting devices (TEOLEDs) are fabricated onto PET substrates with a simple semi-transparent cathode Sm/Ag and two-color phosphors respectively doped into a single host material TCTA. By adjusting the relative position of the orange-red EML sandwiched between the blue emitting layers, the optimized device exhibits the highest power/current efficiency of 8.07 lm/W and near 13 cd/A, with a correlated color temperature (CCT) of 4105 K and a color rendering index (CRI) of 70. In addition, a moderate chromaticity variation of (-0.025, +0.008) around warm white illumination coordinates (0.45, 0.44) is obtained over a large luminance range of 1000 to 10000 cd/m2. The emission mechanism is discussed via delta-doping method and single-carrier device, which is summarized that the carrier trapping, the exciton quenching, the mobility change and the recombination zone alteration are negative to color stability while the energy transfer process and the blue/red/blue sandwiched structure are contributed to the color stability in our flexible white TEOLEDs.

Reliable lasers on Si with large bandwidth are desirable for high-performance data communication systems on Si-photonics platforms. Here, we report short optical pulses generated by gain-switched InP-based 1.55 µm quantum dash (Qdash) lasers directly grown on (001) Si. The laser performance and related physical parameters were investigated by carrying out a gain-switching test for lasers on both Si and native InP substrates. The shortest pulses obtained were 217 and 252 ps for the lasers on InP and Si, respectively. By varying the electrical bias and pulse duration systematically, the evolution of the generated optical pulse duration and peak power was studied. The impact of cavity size on the optical pulse was also examined. Parameters were extracted using established equations fitted with our measurement results to gain insight into the underlying physics and correlation with the observed behavior. The obtained results indicate that the pulse width is limited by the low differential gain and strong gain compression of the active material. Our results indicate that Qdash lasers on Si can demonstrate comparable performance to those on a native InP substrate and manifest its potential application in an Si-based photonics chip for optical on-chip communications.

In this study, the mechanical deformation behaviors of Au nanotubes (Au-NTs) under torsional stress are investigated using molecular dynamics (MD) simulations. The inter-atomic interaction is modeled using the embedded-atom potential. In particular, the effects of loading rate, thickness and length of the nanotube, as well as the thermal effects were systematically explored. The results indicated that higher loading rate, longer length and thinner wall thickness all led to a larger value of critical torsional angle (θcr), which signifies the onset of plastic deformation. On the other hand, θcr decreases with increasing temperature in all simulated results. Moreover, the torsional buckling deformation behavior and geometrical instability are found to strongly depend on the length of Au-NTs, the applied strain rate and temperature with vastly different underlying mechanisms.