Interface formation between metal and poly-dialkoxy-p-phenylene vinylene

Abstract

In this work we address the dynamics and stability of calcium/PPV and barium/PPV interfaces during and after deposition of the metal. Diffusion of calcium and barium into OC 1 C 10 PPV is studied with low energy ion scattering (LEIS) and x-ray photoelectron spectroscopy (XPS). During metal deposition the diffusivity is found to be orders of magnitude higher than after deposition and the diffusion coefficient was found to be dependent on the metal concentration in the PPV. Furthermore, the amount of metal inside the polymer films was found to depend on the deposition rate. These observations were explained in a two-stage diffusion model. In the first stage atoms land on the surface and diffuse fast into the polymer and in the second stage metal ionizes and is trapped and diffusion is strongly decreased. The diffusion coefficient of barium into PPV at T = 298 K is found to be almost an order of magnitude lower than the diffusion coefficient of calcium into PPV [͑0.35± 0.05͒ ϫ 10 −23 m 2 / s and ͑2.7± 0.4͒ ϫ 10 −23 m 2 / s, respectively]. Furthermore, the activation energy of the diffusion process of barium into PPV ͑0.75± 0.07eV͒ is significantly higher than the activation energy of the diffusion process of calcium into PPV ͑0.62± 0.05 eV͒. The difference in diffusion coefficient and activation energy between calcium and barium are discussed in terms of an Arrhenius law of diffusion. Finally, polymer LED performance was studied as a function of the amount of metal diffused into the polymer layer. It was observed that the light output and the efficiency decreased as the amount of metal in the PPV increased. This indicates that the metal ions form charge carrier traps and exciton quenching sites in the PPV.

Electrochemistry at Well‐Characterized Bimetallic Surfaces

“…The results indicate two important characteristics of the surface structure at 0.05 and 0.55 V: (i) at 0.05 V, expansion of the Pt surface atoms induced by the adsorption of hydrogen is very similar to that observed on Pt(111) [Janssen et al, 2004;Iwasita and Nart, 1997] (Dd 1 Pt ¼ þ2%); (ii) at 0.55 V, the p(2 Â 2) structure remains stable but, while the Pt surface atoms are unrelaxed, the Sn atoms in the topmost layer expand up to (Dd 1 Sn ¼ 8:5%) of the lattice spacing. At potentials higher than 0.55 V, this expansion is even more pronounced, indicating that before Sn dissolution, the Sn surface atoms are expanded by approximately 12% of the bulk lattice spacing.…”

“…More recently, investigation of the tails in LEIS has been used as a tool for high resolution nondestructive in-depth composition analysis of ultrathin layers [Brongersma et al, 2003] and shallow interfaces [Janssen et al, 2004].…”

Amide‐Functionalized Small Molecules as Solution‐Processed Electron Injection Layers in Highly Efficient Polymer Light‐Emitting Diodes

“…Interestingly, devices with ODAD/Al and Ca/Al cathodes showed the same current turn‐on voltage ( V J ‐on ) and V L ‐on . The electron injection barrier in both devices should be quite similar and could be ignored because the LUMO of G‐PF is nearly identical to the WF of Ca (–2.9 eV) for the possible formation of Ohmic contact . However, the device with the ODAD/Al cathode showed a much lower J than that with a Ca/Al cathode at the bias of <7.0 V. And, it also showed a lower L at the bias of <7.0 V and a similar L at the bias of 7.0 V. These phenomena were also found in the efficient PLEDs where an intrinsically insulating material was used as the EIL.…”

Effect of Ion Depth in Low Energy Ion Scattering Spectroscopy for Evaluating Nanostructures

“…Since top layer composition and morphology are of decisive importance for the performance of a nanostructure, LEIS is an obvious surface analysis tool for investigation of reaction of activity at the nanostructure surfaces of metal [1][2], organic [3][4], and catalysis [5]. In analysis of surface structure by ion beam technique, the undesired beam effects can disturb the analysis.…”