Shuit-Tong Lee

Bio: Shuit-Tong Lee is an academic researcher from Soochow University (Suzhou). The author has contributed to research in topics: Silicon & Nanowire. The author has an hindex of 138, co-authored 1121 publications receiving 77112 citations. Previous affiliations of Shuit-Tong Lee include University of British Columbia & Hong Kong University of Science and Technology.

Synthesis of Homogeneously Alloyed Cu2−x(SySe1−y) Nanowire Bundles with Tunable Compositions and Bandgaps

Abstract: Bundles of homogeneously alloyed Cu 2 − x (S y Se 1 − y ) nanowires with various compositions (0 ≤ y ≤ 1) are controllably prepared via a simple water-evaporation method under mild conditions. It is found that the nanowire bundles have similar copper contents (0.37 ≤ x ≤ 0.44) and morphologies, and the same face centered cubic (fcc) crystal structure and growth orientation of [110] over the entire composition range of y . To the best of the authors’ knowledge, this is the fi rst report on cubic phased ternary Cu 2 − x (S y Se 1 − y ) compounds. It is found that lattice parameter of the Cu 2 − x (Sy Se 1 − y ) compound changes linearly with the S content. It is also shown that the direct and the indirect bandgaps of the nanowires vary quadratically with the S content and have bowing parameters of 0.20 and 0.21 eV respectively. Energy-gap-tuning via compositional change is achieved for both the direct (1.48 − 1.87 eV) and the indirect (0.50 − 0.90 eV) bandgaps. The trends of lattice parameter and bandgap variations are consistent with those described by Vegard’s Law.

Smallest diameter carbon nanotubes

Abstract: Mass-selected carbon ion beam deposition (MSIBD) was used to demonstrate that the diameter of a carbon nanotube could be as small as 0.4 nm, the theoretical limit predicted but never experimentally reached so far. The deposition was performed at an elevated temperature much lower than the high temperatures (800–1000 °C) needed for deposition of carbon nanotubes by conventional methods. High-resolution transmission electron microscopy showed that the combination of the stress induced by the ion impact and the C migration at the temperature applied formed graphitic sheets with their normal (c axis) parallel to the surface of the silicon substrate. Some sheets closed to form multiwall nanotubes. The smallest diameter of the innermost tube was found to be 0.4 nm. The novel use of MSIBD (a pure method, catalyst free, low deposition temperature, easily applied to large surfaces without surface pretreatment capable of pattern-writing) may significantly advance the carbon nanostructure technology.

Light extraction enhancement in organic light-emitting diodes based on localized surface plasmon and light scattering double-effect

Abstract: We have demonstrated a new approach to realize the light extraction enhancement in organic light-emitting diodes (OLEDs) by using platinum–cobalt (Pt3Co) alloy nanoparticles (ANPs). The current efficiencies of 19.2 cd A−1 and 29.3 cd A−1 at a current density of 20 mA cm−2 are obtained for the device with Pt3Co ANPs unannealed and annealed, respectively, which correspond to a ∼46% and ∼123% enhancement compared to the control device without Pt3Co ANPs. A systematic study on the devices with and without unannealed Pt3Co ANPs shows that the significantly enhanced efficiency is mainly due to the resonance of localized surface plasmon (LSP). The analysis of surface topography, angular-dependent EL spectra and theoretical calculations of the devices with and without annealed Pt3Co ANPs reveals that the annealing treatment of Pt3Co ANPs could result in a further enhancement in light extraction due to the increased light scattering effect, thereby achieving a double-enhancement in light extraction by simultaneously realizing the resonance of LSP and the light scattering effect.

Plasmonic-enhanced polymer solar cells incorporating solution-processable Au nanoparticle-adhered graphene oxide

Abstract: The effect of gold nanoparticle (NP)-induced surface plasmons on the performance of polymer solar cells (PSCs) is investigated by blending the solution processable Au NP-adhered graphene oxide (Au-GO) into the anodic buffer layer of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The incorporation of Au-GOs provides a simple method to introduce a plasmonic effect, which is helpful to avoid aggregation of Au NPs blended in PEDOT:PSS. The addition of Au-GOs increased the light absorption and exciton generation rate in the active layer, thereby enhancing the short-circuit current and power conversion efficiency of these PSCs. According to the experimental and simulated results, the improvement in device performance can be ascribed to the near-field enhancement arising from the excitation of the localized surface plasmon resonance of Au-GOs along the active layer/PEDOT:PSS interface. Our work indicates the great potential of Au-GOs for high-efficiency plasmonic-enhanced PSC applications.

A roadmap for graphene

Abstract: Recent years have witnessed many breakthroughs in research on graphene (the first two-dimensional atomic crystal) as well as a significant advance in the mass production of this material. This one-atom-thick fabric of carbon uniquely combines extreme mechanical strength, exceptionally high electronic and thermal conductivities, impermeability to gases, as well as many other supreme properties, all of which make it highly attractive for numerous applications. Here we review recent progress in graphene research and in the development of production methods, and critically analyse the feasibility of various graphene applications.

High-performance lithium battery anodes using silicon nanowires

Abstract: There is great interest in developing rechargeable lithium batteries with higher energy capacity and longer cycle life for applications in portable electronic devices, electric vehicles and implantable medical devices. Silicon is an attractive anode material for lithium batteries because it has a low discharge potential and the highest known theoretical charge capacity (4,200 mAh g(-1); ref. 2). Although this is more than ten times higher than existing graphite anodes and much larger than various nitride and oxide materials, silicon anodes have limited applications because silicon's volume changes by 400% upon insertion and extraction of lithium which results in pulverization and capacity fading. Here, we show that silicon nanowire battery electrodes circumvent these issues as they can accommodate large strain without pulverization, provide good electronic contact and conduction, and display short lithium insertion distances. We achieved the theoretical charge capacity for silicon anodes and maintained a discharge capacity close to 75% of this maximum, with little fading during cycling.

Nanobelts of Semiconducting Oxides

Abstract: Ultralong beltlike (or ribbonlike) nanostructures (so-called nanobelts) were successfully synthesized for semiconducting oxides of zinc, tin, indium, cadmium, and gallium by simply evaporating the desired commercial metal oxide powders at high temperatures. The as-synthesized oxide nanobelts are pure, structurally uniform, and single crystalline, and most of them are free from defects and dislocations. They have a rectanglelike cross section with typical widths of 30 to 300 nanometers, width-to-thickness ratios of 5 to 10, and lengths of up to a few millimeters. The beltlike morphology appears to be a distinctive and common structural characteristic for the family of semiconducting oxides with cations of different valence states and materials of distinct crystallographic structures. The nanobelts could be an ideal system for fully understanding dimensionally confined transport phenomena in functional oxides and building functional devices along individual nanobelts.

Raman spectroscopy as a versatile tool for studying the properties of graphene

Abstract: Raman spectroscopy is an integral part of graphene research. It is used to determine the number and orientation of layers, the quality and types of edge, and the effects of perturbations, such as electric and magnetic fields, strain, doping, disorder and functional groups. This, in turn, provides insight into all sp(2)-bonded carbon allotropes, because graphene is their fundamental building block. Here we review the state of the art, future directions and open questions in Raman spectroscopy of graphene. We describe essential physical processes whose importance has only recently been recognized, such as the various types of resonance at play, and the role of quantum interference. We update all basic concepts and notations, and propose a terminology that is able to describe any result in literature. We finally highlight the potential of Raman spectroscopy for layered materials other than graphene.

Aggregation-Induced Emission: Together We Shine, United We Soar!

Abstract: Ju Mei,†,‡,∥ Nelson L. C. Leung,†,‡,∥ Ryan T. K. Kwok,†,‡ Jacky W. Y. Lam,†,‡ and Ben Zhong Tang*,†,‡,§ †HKUST-Shenzhen Research Institute, Hi-Tech Park, Nanshan, Shenzhen 518057, China ‡Department of Chemistry, HKUST Jockey Club Institute for Advanced Study, Institute of Molecular Functional Materials, Division of Biomedical Engineering, State Key Laboratory of Molecular Neuroscience, Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China Guangdong Innovative Research Team, SCUT-HKUST Joint Research Laboratory, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China