Effect of quantum dot shape on dynamical dephasing suppression in exciton qubits under applied electric field

We investigate the efficiency of periodic dynamical decoupling of an exciton qubit confined in a self-assembled quantum dot in the presence of an applied electric field. The shape of the quantum dot is found to have a large effect on the excitonic dephasing. It is shown that dynamical suppression of dephasing, through a simple series of equally spaced bit flips, is most efficient for quantum dots that are close to spherical. In addition, compared to the no field case, the presence of an electric field increases the efficiency of the decoupling technique as the quantum dot becomes more oblate. Our calculations show that dephasing can be significantly suppressed in GaAs/AlAs quantum dots suitable for quantum information processing.     

Realizing efficient exciton dissociation in an all-organic heterojunction photocatalyst for highly improved photocatalytic H2 evolution

Although graphitic carbon nitride is a promising photocatalyst in the field of energy conversion and environmental purification, the intrinsic properties like excitonic effects and sluggish charge transfer restrict further photocatalytic applications. To circumvent these limitations, the novel all-organic heterojunction photocatalysts were constructed by anchoring organic carbon dots (O-dots) on porous graphitic carbon nitride nanosheets (O-dots/CNS). Results demonstrated that excitons can be e?ectively dissociated into electrons and holes at the interface of O-dots/CNS heterojunction, followed by holes injected to O-dots and electrons accumulated in CNS to realize efficient charge separation. Consequently, the O-dots/CNS with the optimized hydrogen (H₂) evolution performance could be reached 1564.5 μmol h^?1g^?1 under the visible light irradiation. This work not only presents new ideas for rational design photocatalytic reaction system from exciton and charge carrier, but also broaden the applications of this new kind of organic dots in the field of energy conversion.     

Bright electroluminescence from single-layer organic light-emitting diodes comprising an ambipolar carrier transport layer of phenyldipyrenylphosphine oxide

We investigated the carrier transport and recombination characteristics of single-layer organic light-emitting diodes (SLOLEDs) composed of a phenyldipyrenylphosphine oxide (POPy₂) layer doped with orange fluorescent molecules of 2,5-bis-[{bis-(4-methoxy-phenyl)-amino}-styryl]-terephthalonitrile (BST). The SLOLEDs achieved a high external quantum efficiency of 1.6% and a high luminance of 24,000 cd/m² at a low driving voltage of 8 V. These very good electroluminescence characteristics originate from factors that include our use of the following: (1) the ambipolar POPy₂ layer, which can transport balanced amounts of electrons and holes, (2) a high BST-doping concentration that traps injected carriers on BST molecules, and (3) insertion of an undoped POPy₂ layer next to a metallic cathode to prevent exciton quenching.     

Investigation on the synthesis and quantum confinement effects of pure and Mn added Zn(1−x)CdxS nanocrystals

Zn_(1−x)Cd_xS and Zn_(1−x)Cd_xS:Mn²⁺ semiconductor quantum dots (2-4 nm) have been prepared by a novel solvothermal route assisted microwave heating method. The growth parameters governing the smaller size and higher yield have been optimized. The synthesized QDs exhibit a significant blue shift as compared to their corresponding bulk counterpart in the UV-vis optical absorption spectrum. The dielectric constant value varies from 2.79 to 6.17 (at 40 °C, 1 kHz) depending upon the composition of the alloy; lower value corresponds to Zn_0.75Cd_0.25S:Mn²⁺ and the higher value corresponds to Zn_0.25Cd_0.75S:Mn²⁺. The crystallite size to exciton bohr radius ratio being <1 indicates a strong quantum confinement effect in both CdS and ZnS QDs. The quantum confinement effect exists in the sequence of ZnS:Mn²⁺ < Zn_(1−x)Cd_xS:Mn²⁺ (x < 0.5) < ZnS < Zn_(1−x)Cd_xS < CdS < CdS:Mn²⁺.     

Exciton quantum confinement in nanocones formed on a surface of CdZnTe solid solution by laser radiation

The investigation of surface morphology using atomic force microscope has shown self-organizing of the nanocones on the surface of CdZnTe crystal after irradiation by strongly absorbed Nd:YAG laser irradiation at an intensity of 12.0 MW/cm². The formation of nanocones is explained by the presence of a thermogradient effect in the semiconductor. The appearance of a new exciton band has been observed after irradiation by the laser which is explained by the exciton quantum confinement effect in nanocones.     

Advances in Materials Research for Displays from Serendipity to Materials by Design

New materials have been developed for PDP for fast addressing and power reduction.They show the transition in R&D from materials invented accidentally to materials-by-design.Cathode-luminescence on MgO...