Discovery of two new phases of zirconium tetrakis(8-hydroxyquinolinolate): synthesis, crystal structure and their electron transporting characteristics in organic light emitting diodes (OLEDs)

Two new phases of zirconium tetrakis(8-hydroxyquinolinolate) (Zrq4) have been synthesised and characterised by single crystal X-ray diffraction. Their electrical, electronic, optical and thermal properties have been studied. Their electron transporting characteristics have been investigated in organic light emitting devices where the two phases show remarkable differences in performance. One of the forms (designated a-Zrq4) gives significantly lower operating voltage, higher efficiencies and longer lifetime than the other (designated b-Zrq4) in organic light emitting devices.EPSR

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

The modification of the room-temperature conductivity of electrodeposited Bu4NNi(dmit)2 with ambient gases

This paper describes the effects of sulfur dioxide and nitric oxide on the conductivity of electrodeposited films of the nickel salt of tetrabutylammonium bis(1,3-dithiol-2-thione-4,5-dithiolate). The resistance of the films increased on exposure to SO2; these changes were reversible in argon. The films were more sensitive to NO although these changes were found to be largely irreversible. The absorption kinetics of the gas interaction were studied and were found to follow the Elovich isotherm. It was anticipated that the changes in resistance would be in opposite directions on exposure to SO2 and NO. Elemental analysis suggested the film contained a small amount of the mixed valence species. It is suggested that the NO acted on this species and oxidized it to the lower conductivity neutral species; the SO2 was presumed to act upon the mixed valence species and reduce it to the lower conductivity monoanion species

Isolation and Characterisation of 2-Tert-butyl-8-hydroxyquinoline as a Crystalline Solid and Its Blue Fluorescent Li Complex

2-Tert-butyl-8-hydroxyquinoline (2-TB-8-hq) has been isolated as a crystalline solid and its X-ray structure elucidated, resolving three decades of controversy, since it was previously wrongly reported as yellow oil by some other workers. An improved synthetic method has been developed which increases the yield from 20% to 60%. The lithium complex of 2-TB-8-hq is blue emitting and the HOMO and LUMO levels are lowered by 0.86 eV and 0.74 eV, respectively, compared with the parent lithium 8-hydroxyquinolinolate (Li 8-hq)