Spatial Separation Of Charge Carriers Research Articles

Phosphorene quantum dot-fullerene nanocomposites for solar energy conversion: An unexplored inorganic-organic nanohybrid with novel photovoltaic properties

Using the self-consistent charge density-functional based tight-binding (SCC-DFTB) method, coupled with time-dependent density functional theory (TDDFT) calculations, for the first time we explore the possibility of use of phosphorene quantum dots in solar energy harvesting devices. The phosphorene quantum dots-fullerene (PQDs-PCBA) nanocomposites show type-II band alignment indicating spatial separation of charge carriers. The TDDFT calculations also show that the PQD-fullerene nanocomposites seem to be exciting material for future generation solar energy harvester, with extremely fast charge transfer and very poor recombination rate.

Optoelectronic response and interlayer exciton features of MoS2/WS2 Van der Waals heterostructure within first principle calculations and Wannier Mott model

Recent photoluminescence spectra of MoS2/WS2 heterostructure have been measured and have shown a pronounced interlayer exciton resonance which opens to a prosperous functionalities and new physical effects. To theoretically explain and understand the interlayer exciton features, a first principle calculations, image potential method and Wannier-Mott model taking in account the so-called dielectric confinement are applied. Our results emphasize the type II alignment of MoS2/WS2 heterostructure and d-orbital character of angular momentum contribution resulting in spatial separation of charge carriers. An insight about the change in the effective mass values from isolated monolayers to heterobilayers and in dielectric constants versus applied energy is also mentioned. The interlayer exciton is found to have a considerable binding energy and is expected to be stable at room temperature. We believe that Van der Waals heterostructure MoS2/WS2 holds a strong potential for optoelectronic applications.

Enhanced photocatalytic activity by bulk trapping and spatial separation of charge carriers: A case study of defect and facet mediated TiO2

Revealing the interplay between composition and structure of a given photocatalyst allows in-depth understanding of the photocatalytic mechanism and also presents as an effective way to optimise the photocatalytic activity. In this work, by studying the property and performance of defect and facet mediated rutile TiO2 synthesized via a facile oxidation reaction, we demonstrated that the abundant self-doped defects can not only render visiblie responce to the reduced TiO2 but also supress the prompt recombination of the charge carriers through bulk trapping, while the {111}–{110} facet couples can induce the spatial separation of the e–h pairs. A synergistic effect between the defects and the facets was observed in the co-mediated TiO2, and its performance of hydrogen liberation was enhanced by a factor of 18 under simulated solar light compared with referenced commercial rutile, consequently. The present work sheds new light on how the composition and structure of a material can be finely tuned and work synergistically to achieve a much boosted performance.

High-Performance Photoconductivity and Electrical Transport of ZnO/ZnS Core/Shell Nanowires for Multifunctional Nanodevice Applications

We report the electrical and optical properties of ZnO/ZnS core/shell nanowire (NW) devices. The spatial separation of charge carriers due to their type II band structure together with passivation effect on ZnO/ZnS core/shell NWs not only enhanced their charge carrier transport characteristics by confining the electrons and reducing surface states in the ZnO channel but also increased the photocurrent under ultraviolet (UV) illumination by reducing the recombination probability of the photogenerated charge carriers. Here the efficacy of the type-II band structure and the passivation effect are demonstrated by showing the enhanced subthreshold swing (150 mV/decade) and mobility (17.2 cm2/(Vs)) of the electrical properties, as well as the high responsivity (4.4×10(6) A/W) in the optical properties of the ZnO/ZnS core/shell NWs, compared with the subthreshold swing (464 mV/decade), mobility (8.9 cm2/(Vs)) and responsivity (2.5×10(6) A/W) of ZnO NWs.

Tunable band gap of boron nitride interfaces under uniaxial pressure

In this work we show, by means of a density functional theory formalism, that the interaction between hydrogen terminated boron nitride surfaces gives rise to a metallic interface with free carriers of opposite sign at each surface. A band gap can be induced by decreasing the surface separation. The size of the band gap changes continuously from zero up to 4.4 eV with decreasing separation, which is understood in terms of the interaction between surface states. Due to the high thermal conductivity of cubic boron nitride and the coupling between band gap and applied pressure, such tunable band gap interfaces may be used in highly stable electronic and electromechanical devices. In addition, the spatial separation of charge carriers at the interface may lead to photovoltaic applications.

ChemInform Abstract: Semiconductor Nanoparticles with Spatial Separation of Charge Carriers: Synthesis and Optical Properties

AbstractReview: 165 refs.

Mechanism for spatial separation of charge carriers in inhomogeneous semiconductor alloys.

A novel mechanism is proposed for charge-carrier separation by band-edge steps in inhomogeneous alloys with sufficiently strong compositional fluctuations. The phenomenon is predicted to occur for alloy compositions where the highest valence band and the lowest conduction band have slopes of the same sign as a function of the average alloy composition. We discuss experimental data for indirect-gap $\mathrm{Ga}{\mathrm{As}}_{1\ensuremath{-}x}{\mathrm{P}}_{x}$ which provide confirmation of this prediction. Finally, other alloy systems and alloy structures for which related phenomena may occur are suggested.