Minority-carrier effects in poly-phenylenevinylene as studied by electrical characterization

Electrical measurements have been performed on poly[2-methoxy, 5 ethyl (2' hexyloxy) paraphenylenevinylene] in a pn junction with silicon. These included current-voltage measurements, capacitance-voltage measurements, capacitance-transient spectroscopy, and admittance spectroscopy. The measurements show evidence for large minority-carrier injection into the polymer possibly enabled by interface states for which evidence is also found. The shallow acceptor level depth (0.12 eV) and four deep trap level activation energies (0.30 and 1.0 eV majority-carrier type; 0.48 and 1.3 eV minority-carrier type) are found. Another trap that is visible at room temperature has point-defect nature. (C) 2001 American Institute of Physics

Inkjet printing of well-adapted PEDOT-PSS dispersions

Poly (3,4-ethylenedioxythiophene)-polystyrenesulfonic acid (PEDOT-PSS) is a popular conductive polymer that finds widespread use in the fields of polymeric electronics and display applications. Its major advantages lie in the suitability for flexible electrical devices and the relatively simple deposition process capabilities with techniques such as inkjet printing. However, the deposition of PEDOT-PSS dispersions with inkjet printheads can cause a number of problems due to possible interaction of the fluids with the printhead, and due to poor inkjet functionality and layer formation on the substrate. In the present work we have adapted PEDOT-PSS dispersions for improved performance in a Xaar-type piezoelectric inkjet printhead, in particular for high quality drop formation and for reduced corrosion of the inkjet printhead. At the same time the best PEDOT-PSS inks regarding layer formation and conductivity were identified. As an application example, a passive LCD device incorporating an inkjet printed PEDOT-PSS electrode pattern that was produced with an adapted PEDOT-PSS ink is presented

High levels of alkali-metal storage in thin films of hexa-peri- hexabenzocoronene

The affects of alkali-metal atoms on the electronic structure of disordered and highly ordered thin films of the medium-size aromatic hydrocarbon hexa-peri-hexabenzocoronene (HBC) have been investigated by valence and core level photoelectron spectroscopies-ultraviolet photoelectron spectroscopy (UPS) and x-ray photoelectron spectroscopy (XPS)-and accompanying quantum-chemical calculations. Deposition of Li or Na atoms in situ leads to new spectral features in the UPS spectra, which are related to formerly unoccupied molecular states. The binding energies and intensities of these features depend on the nature of the counterion. The smaller Li ion exhibits a stronger influence on the electronic structure than its sodium counterpart. In the intercalation of sodium into ordered films, a high degree of molecular order is preserved, and, at high deposition levels, a surface dipole is formed that is associated with the layered structure of the compound. Remarkably, high levels of alkali-metal storage of at least one alkali-metal atom for each four carbon atoms have been observed, indicating clearly the potential use of these graphene materials in lithium-ion batteries with a high charge- storage capacity. (C) 2002 American Institute of Physics