Novel lithium Schiff-base cluster complexes as electron injectors: synthesis, crystal structure, thin film characterisation and their performance in OLEDs

This journal is © The Royal Society of Chemistry 2012A set of novel lithium Schiff base cluster compounds has been synthesised and characterised for the first time and tested as electron injectors in OLED devices. Their electrical, electronic, thermal and optical properties have been investigated and compared with the industry standards LiF and lithium quinolinolate (LiQ). Amongst the compounds tested, lithium 2-((o tolylimino)methyl) phenolate was found to enhance the efficiency of OLEDs by 69% compared to LiF and 15% compared to LiQ. The same electron injector was found to extend the lifetimes of OLEDs by six-fold compared to LiF and 4.3- fold compared to LiQ respectively. The crystal structure of the parent compound, lithium 2- ((phenylamino)methyl)phenolate reveals that the compound is tetrameric in contrast to hexameric LiQ. Substituting the methyl group with fluorine causes a remarkable depression of the HOMO and LUMO levels by up to 1.2 eV. Analysis of current density vs. voltage characteristics of single-layer devices for Li–Al/electron injector/Li–Al and Al/electron injector/Al reveals that both sets of devices are operating as electron-only devices indicating that the formation of free lithium is the cause of enhanced electron injection, but either the energetic aluminium atoms (as proposed previously by other workers) or energetic lithium complexes on an aluminium surface (as we have demonstrated in this paper) are all that is required for efficient electron injection

Next‐Generation Energy Harvesting and Storage Technologies for Robots Across All Scales

Self‐powered untethered robots that can meander unrestrictedly, squeeze into small spaces, and operate in diverse harsh environments have received immense attention in recent years. As there is not a universal solution that can be applied to power robots with diverse forms, service functions, and a broad size range from nanometers to meters, the design, fabrication, and implementation of power systems with a suitable weight, desired power and operation duration, and adaptiveness to confined spaces and operation conditions represent one of the greatest challenges in robotic research. Herein, an overview of recent progress and challenges in developing the next‐generation energy harvesting and storage technologies is provided, including direct energy harvesting, energy storage and conversion, and wireless energy transmission for robots across all scales

Boron-doped ultrananocrystalline diamond synthesized with an H-rich/Ar-lean gas system

This paper reports the recent development and applications of conductive boron-doped ultrananocrystalline diamond (BD-UNCD). The authors have determined that BD-UNCD can be synthesized with an H-rich gaseous chemistry and a high CH4/H2 ratio, which is opposite to previously reported methods with Ar-rich or H-rich gas compositions but utilizing very low CH4/H2 ratios. The BD-UNCD reported here has a resistivity as low as 0.01 ohm cm, with low roughness (<10 nm) and a wide deposition temperature range (450–850 °C). The properties of this BD-UNCD were studied systematically using resistivity characterization, scanning and transmission electron microscopy, Raman spectroscopy, and roughness measurements. Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy confirms that up to 97% of the UNCD is deposited as sp3 carbon. These various measurements also reveal additional special properties for this material, such as an “M” shape Raman signature, line-granular nano-cluster texture and high Csingle bondH bond surface content. A hypothesis is provided to explain why this new deposition strategy, with H-rich/Ar-lean gas chemistry and a high CH4/H2 ratio, is able to produce high sp3-content and/or heavily doped UNCD. In addition, a few emerging applications of BD-UNCD in the field of atomic force microscopy, electrochemistry and biosensing are reviewed here